SCHOOL OF SCIENCE AND TECHNOLOGY ENG 499 ENHANCED COUPLING OF A KA-BAND NARROW BAND PASS FILTER USING LTCC TECHNOLOGY PREPARED BY STUDENT PI SUPERVISOR PROJECT CODE : Tan Puay Thiam : H0604673 : LUM KUM MENG : JAN2010/ENG/0070 A project report submitted to SIM University in partial fulfilment of the requirements for the degree of Bachelor of Engineering Page 1 of 83 1 ACKNOWLEDGEMENT I would like to express my most sincere gratitude to my supervisors Dr. Lum Kum Meng for their invaluable guidance, suggestions, and constructive criticisms during the investigation of the project and the preparation of this thesis. At the same time, I would like to thank my friends and colleagues from our microwave group and ST Electronics for their support and kind assistance. Finally, I would like to express my appreciation to my family and friends, from whom I received much encouragement in the project. Page 2 of 83 Table of Contents 1 ACKNOWLEDGEMENT .......................................................................................... 2 2 PROJECT DEFINITION .......................................................................................... 5 2.1 2.2 2.3 Project Objective .................................................................................................................... 5 Overall Objective .................................................................................................................... 5 Approach and method to be employed ................................................................................ 6 2.3.1 Stage 1: Design a end Coupled pass filter enhanced coupling of Ka-Band in LTCC. ............ 6 3 PROCESS FLOW TO DESIGN THE FILTER, ASSEMBLE & MEASUREMENT .. 13 4 LITERATURE REVIEW......................................................................................... 14 4.1 4.2 RF Filter Design ....................................................................................................................14 Why using ADS tool? ...........................................................................................................18 4.2.1 Featuring of ADS Momentum ............................................................................................... 19 LTCC features with some application ................................................................................20 4.3.1 LTCC Process ........................................................................................................................ 22 Microstrip ..............................................................................................................................25 4.4.1 Other types of MICROSTRIP ............................................................................................... 26 4.4.2 Typically there are 5 types of Microstrip filter: ..................................................................... 27 Microstrip Resonator ...........................................................................................................28 MicroStrip Transmission Line .............................................................................................29 Coupled Microstrip lines .....................................................................................................31 FR4 Process Methodology ..................................................................................................33 4.8.1 Plating Process Options ......................................................................................................... 34 4.8.2 Tin/Lead Alloy Plating .......................................................................................................... 34 4.8.3 Ni/Au Electroless or Immersion Plating Process for Soldering ............................................. 34 4.8.4 Alternatives to Alloy Plating ................................................................................................. 34 4.8.5 Process on Organic Solderability Preservative (OSP) ........................................................... 34 4.8.6 Assembly Process Compatibility ........................................................................................... 35 4.8.7 Limited Shelf Life for OSP Coated Boards ........................................................................... 36 4.8.8 Benefits of Coated Surfaces................................................................................................... 36 4.8.9 Concerns of Coated Boards ................................................................................................... 36 4.8.10 Advantage on FR-4-86 material for Microwave and RF applications ................................... 36 4.8.11 ADS implementation ............................................................................................................. 37 4.8.12 Calculation Method ............................................................................................................... 38 4.8.13 Determine the microstrip guided wavelength ........................................................................ 39 4.3 4.4 4.5 4.6 4.7 4.8 5 FILTER IMPLENTATION IN ADS ......................................................................... 40 5.1 5.2 Setting of substrate Parameters in LTCC ..........................................................................40 5.1.1 Set up of Montenum under ADS ........................................................................................... 41 Setting of substrate Parameters in FR4 .............................................................................43 6 FABRICATION ON FR4 END GAP COUPLED .................................................... 46 6.1 6.2 6.3 Process of FR4 from supplier .............................................................................................47 Hardware Mounting 1 ( Initial Design) ................................................................................48 Hardware Mounting 2 ( Final Design) .................................................................................49 Page 3 of 83 7 HARDWARE MEASUREMENT ............................................................................ 50 7.1 Hardware Measurement Set Up ..........................................................................................50 7.1.1 Measurement Result .............................................................................................................. 51 7.1.2 Summary of the end-gap coupled multilayered FR4 BPF ..................................................... 52 7.1.3 Conclusion ............................................................................................................................. 52 8 GANTT CHART .................................................................................................... 53 9 APPENDIX A ........................................................................................................ 54 9.1 9.2 9.3 Website ..................................................................................................................................55 Appendix B............................................................................................................................57 Appendix C: Software simulation for FR-4 .......................................................................60 9.3.1 Appendix D: Software simulation for FR-4.......................................................................... 62 9.3.2 Appendix E: Software simulation for FR-4 .......................................................................... 67 Appendix F: Meetings Logs ...............................................................................................74 9.4 Page 4 of 83 2 PROJECT DEFINITION 2.1 Project Objective The main intention for this project is to design an enhanced coupling of a KA-BAND (26~40GHz) Narrow Band-Pass Filter using Low Temperature co-fired ceramics (LTCC) Technology. Scopes include: a) Reviewing the literature and understanding of LTCC technology. b) Evaluating current filter designs for LTCC applications. c) Design a narrow band filter according to LTCC specification. d) Illustrate a few filter designs using ADS software simulation. e) Research on FR4 printed circuit board. f) Design and simulate a narrow band filter using FR4 material. g) Illustrate a few filter designs using ADS software simulation. h) Draw out Gerber file and send for fabrication. i) Inter connect of PCB using SMA connectors for ribbon bonding or soldering. j) Using instruments like Scalar Network Analyzer or Vector Network Analyzer (VNA) to measure the response of the filter. k) Analyser for further modification and improvement to accomplished the proct. 2.2 Overall Objective Microwave filters are essential components in modern wireless communication systems. RF band pass filter are sometimes required for the separation of up link and downlink transmission paths. Narrow band filters are used for the rejection of the image channel as well as any strong interfering signal in nearby frequency band. Recently the used of low temperature co-fired ceramic (LTCC) technologies broadly enchant more RF engineer attentions for their superior advantages over other substrate technologies. However, is not like a normal organic PCB but the general concept is reminded and the result is monolithic ceramic multi layers. Three dimensions in 3-D integration capabilities that create extend compendium and low costs design. Small value of dielectric loss tangents reveals very high excellent frequency characteristics[1]. Microwave BPFs have been employing more advantages of the LTCC technologies less than 10GHz [2][3]. End coupled Ka-Band pass filter adopting 3-D multilayered LTCC technology. Even though the end-coupled Band Pass Filter has a narrow bandwidth characteristic the same as other filter structures, the shrinkage and restricted resolution of LTCC process make it very difficult to control the absolute gap between the two adjacent resonators close enough coupling on the same planar substrate. Minimum spacing for the adjacent conductors is 150 micro meter with screen-printing LTCC process too large for the Page 5 of 83 wanted series capacitive coupling between adjacent resonators. Positions on the microstrip resonators on different layers in the multilayered structure abolish those process limitations by vertically isolate the adjacent resonators with an intermediate LTCC tape. In addition overlapping two adjacent ends of resonators can determine the filter characteristics, the bandwidth, sharpness and minimum insertion loss in pass band[4]. 2.3 Approach and method to be employed To commutate the objective of the project, a prerequisite project management is necessary. Execution of various tasks must be strictly adhered. The project progress is broken down into stages: 1ST STAGE: 1) Design a narrow band pass filter enhanced coupling 3th order of a Ka-Band in LTCC. 2) Simulate the filter using Advanced Design System tools. 3) Enhanced and simulate to get better result. 2nd STAGE: 1) 2) 3) 4) 5) 6) 7) 2.3.1 Design a narrow band pass filter on FR4 material. Enhanced to simulate and testing to get better S21 nearly to 0dB. Thick Film Fabrication on ceramics substrates Test Fixtures Testing and measurement Project evaluation Enhancement of design Stage 1: Design a end Coupled pass filter enhanced coupling of KaBand in LTCC. Understand and research of band pass filter enhanced of a Ka-Band. Have a clearer view which type and stages of filter to be used. Advantage and disadvantage of LTCC. Page 6 of 83 Stage 2: Simulate the filter using Advanced Design System tools. Understand the circuit simulation of a filter whereby the input signal defined as modulation of the carrier,V(t) and the RF carrier and its harmonics in the frequency domain. Time steps and total time interval also defined. When simulation is running, the spectrum at the output and other nodes is completed at each time point. The results make its available of the amplitude and the phase of any spectral component as a function of time. If any large signal of S-parameter needs to be done at two-port, the simulator can performs. Terminate port 2 with the complex conjugate of its reference impedance. Apply a signal with a specific power level P1 at port 1, using the source whose impedance equals to the complex conjugate of the port’s reference impedance. Use harmonics balance, calculate the currents and voltages at port1 and port 2. Use this information to calculate S11 and S21. Terminate port 1 with the complex conjugate of its reference impedance. Apply a signal of power P2=[S21]P1 at port 2. Using harmonics balance calculates the currents and voltages at port 1 and port 2. Use this information to calculate S12 and S22. Page 7 of 83 Stage 3: Enhanced and simulate to achieve better result 10 simulation layout and result based on a Ka-Band Narrow Band Pass Filter using LTTC technology. The design was base on third order gap coupled multilayered LTCC BPF characteristics according to Matthaei, Young and Jones synthesis method[5]. This overlapping design of two adjacent ends of resonators can control filter characteristics. Centre Freq (fo) = 30.23GHz Lower Band Edge (fL)= 29.77GHz Upper Band Edge (fH)= 30.68GHz Fractional Bandwidth (w)= 3.0% where ((fH-fL )/fo)x100% Min insertion loss= 3.12dB Page 8 of 83 2.3.1.1 Stage 1: Design a narrow band pass filter on FR4 material. Research and understand how to calculate narrow end coupled band filter with FR4 material for 1.5GHz. Have a clearer view which type and stages of filter to be used. Advantage and disadvantage of FR4. Enhanced result for s11 & s21. Centre Freq (fo) = 1.494GHz Lower Band Edge (fL)= 1.426GHz Upper Band Edge (fH)= 1.550GHz Fractional Bandwidth (w)= 8.299% where ((fH-fL )/fo)x100% Min insertion loss= 3.148dB Stage 2: FR4 Fabrication on printed circuit board and its features Multifunctional laminates, Tg 140ºC (DSC) Excellent electrical properties for standard loss material. Exceptional consistent laminate quality due to exclusive use of Nan Ya’s raw materials. Common PTH process parameters result in very good through hole reliability and copper foil peel strength. 90 min press at 182°C and 200-300psi. High luminance of Epoxy contract with copper for laser type AOL Page 9 of 83 Stage 3: Test Fixtures (Optional) A required or optional in mechanical housing and a transition between the microstrip circuit and the co-axial connectors. Example SMA connectors, APC3.5 etc. which are gold plated. Ensure clean surface when connecting free from oxidation. The coax usually has larger cross section than the microstrip and requires the uses of tapering either continuously or in steps. Launchers connect directly to the microstrip might be solder or using ribbon bonds attach below the connector depends on which material uses in microstrip. A typical launcher cross section shown in Fig 1.3.1.1 Some design principles need to be follow 1. 2. 3. 4. 5. The housing wall or centre pin should be 50Ω coax line. Centre must not be wider than 50Ω microstrip line. No gap between the carrier and the side of housing. Substrate height must be not so small that the ground interferes with the coaxial fields at launcher pin end. No air gaps should exist in between the microstrip ground plane and the housing base. Fig 1.3.1.1 Page 10 of 83 Stage 4: Testing and Measurement Using a Network Analyzer, self calibration on the equipment, that includes cal “Short” and “Open”. Connect DUT (Fixtures with Filter) input to Port 1 and the output to Port 2. Commonly measure are insertion loss, bandwidth and out of band rejection. Measure how well the filter passes through signals within its bandwidths while simultaneously rejection signals well outside that same bandwidth. Return loss is plot showing high reflection in the stopbands and good impedance matching in the same band. Page 11 of 83 Stage 6: Project Evaluation At these stage, simulated and tested resulted should be approximately the same that meets the objective. Limitation or enhanced improvement should be added in at the second stage of the design. Stage 7: Enhancement of design After comparing the result, the parameter of this project must be evaluated to improve the filter design. Lists of areas we should look into Return loss should be as low as possible. There should be nearly 0dB insertion loss ideally. Maintain the filter shape of the pass band pattern. Page 12 of 83 3 PROCESS FLOW TO DESIGN THE FILTER, ASSEMBLE & MEASUREMENT Start A Design and range of filter select Select Software simulation . Use ADS tools and design the filter Objective Met? Yes No Compare simulation and test result the Objective Met? Rework on assemble hardware Yes Re-simulate the filter at least few times on 1st design Compare simulation and test result again Simulate and fabrication using FR4 material on 2nd design Fabrication the test fixture.(Optional) No Objective Met? No Design and Fabrication error. Retune the Filter Yes Final Assembly Assemble to test fixture by using Epoxy or Eutectic method in the housing and assemble the connector. Perform measurement using Network Analyzer End A Page 13 of 83 4 4.1 LITERATURE REVIEW RF Filter Design Radio Frequency (RF) defined as a class of electronic filter to operate at the low to high frequency signals. This frequency range for example can be use in broadcasting, mobile, WI-Fi etc. This RF devices which will include some of the filtering signals for transmitted or received. It also can be used as a blocking of duplexers or to separate certain frequency bands. Generally there are 4 types of filters that we know. Low Pass Filter High Pass Filter Band Pass Filter Bandstop Filter For Low Pass Filter we knows it allow lower frequency signals to be transmitted from the input to the output with little attenuation. Moreover, if the frequency exceeded a certain cut off point, the attenuation increases significantly of the result to deliver amplitude reduced signal to the output port. For High Pass Filter is the opposite of low pass filter. The lower frequency components are higher to the signal attenuated or reduced in amplitude while a cut off frequency point the signal passes through the filter with little attenuation. For Band Pass or Band Sop Filter restricted the band pass between certain or specific lower and upper frequencies point where the attenuation is either low in Band pass or high in Band stop compared the rest of the remaining frequency band. Below on Fig 4.1.A shows the summary of the behaviors on ideal 4 types of filters of their attenuation in dB versus normalized angular frequency in Ω behavior. Page 14 of 83 Figure 4.1.A The parameter Ω= / c as a normalized frequency with respect to the angularfrequency c which denotes the cut off frequency for low pass and high pass filter and centre frequency for pass band and band stop filter. This normalization will simplify in developing standard filter approaches. Actual attenuation profile in Figure 4.1.B show three type of low pass filter which are: Binomial Filter (Butterworth) Chebyshev Filter Elliptic (Cauer) Filter Page 15 of 83 Figure 4.1.B The Binomial Filter normally called Butterworth exhibits a monotonic attenuation profile that easily to implement. But to achieve a steep attenuation transition from pass to stop band a large number of component is needed. A better steeper slope can be implemented if one permits a certain degree of variations or ripples in the pass band attenuation profile. As for Chebyshev filter each ripple to maintain equal number of amplitude either in stop band or pass band. Both Binomial and Chebyshev attenuation approach to infinity as . As for Elliptic filters which allows the steepest transitions from pass band to stop band at the expense of ripples in both hands. Analyzing the various trade offs when dealing with filters which described below in Figure 4.1.C: Page 16 of 83 Insertion Loss Ripple Bandwidth Ideally perfect filter inserted into RF circuit path which introduced no power loss in the pass band. In reality, we expect a certain power loss associated with the filter. Its quantifies how much below 0dB line power amplitude response drops. Flatness of the signal in the pass band quantified by specifying the ripple between maximum and minimum amplitude response in dB or Nepsers. For band pass filter, the bandwidth defines between upper and lower frequencies typically recorded at the 3dB above the pass band Shape Factor Rejection Its describes the sharpness of the filter response by taking the ratio between 60dB and the 3dB bandwidths Obtain infinite attenuation level at the undesirable signal frequencies. In reality expect the upper bound due to deployment of a finite number of filter components. Practical design often specifies 60dB as the rejection rate. Figure 4.1.C Page 17 of 83 4.2 Why using ADS tool? In the commercial worlds, there lot of software for filter simulation. For example, Sonnet High Frequency Structure Simulator (HFSS) Advanced Design System (ADS) Fig 4.2.A shown comparison between 3 software simulations. Software HFSS Sonnet Advanced Design System 1 Automation software for RF. Most innovative and Full wave EM simulation for High frequency industry as a commercially such as Xhigh frequency/ High speed developer and supplier of parameter & 3D EM Components. Eg Circuits, innovative planar EM simulators use in wireless connectors and filter. analysis tool communication industries and defence industries. 2 Integrates with many software through Ansoft designer environment access to HFSS. Nexxim circuit simulator and Slwave signal integrity analysis tool. EM simulation tools analyzing 3-D plannar circuits including Microstrip, Stripline, Printed circuit board with multilayer Provide full standard based design and verification using in wireless libraries and system EM-co simulation integrated platform. Figure 4.2A Page 18 of 83 Why choosing ADS? ADS come with some benefits that I would like to proposal in my filter project. A high low frequency and high speed platform for engineers to do co-design of integrated circuit, module, and printed circuit board for filters. Its help the designers work with a single EDA platform to share simulation models and to minimize design for rework, costs and delays in communications. ADS also supported by 3th party by leading industry and foundry partner. Accuracy and integrate fast for ease of use in the system for circuit & EM simulators and able to first pass deign in a complete desktop flow. There is a Demo on how to design a filter on ADS on youtube. Courtesy from: http://www.youtube.com/watch?v=2bgk0dnNjaY&feature=player_embedded# 4.2.1 Featuring of ADS Momentum The Momentum simulator uses the actual physical layout of the device to perform the simulation. ADS convieniantly translates the parameters entered into the circuit diagram into real shapes in the layout side of the program. The user then pieces together the parts to make the device. The translator tries to piece them together, but often fails. After the substrate is entered, the substrate Green's functions must be calculated. These are needed for the momentum method and are independent of the actual shape of the signal conductors. They can, therefore , be computed before the bulk of the simulation and be reused. Momentum then needs to define a mesh for the simulation. Here, the user has some input as to how fine the mesh is laid out. The default resolution is 30 cells per wavelength. This, along with the maximum frequency of the simulation determines the mesh. Momentum will draw rectangles and triangles that approximate the signal artwork. This should give an idea of the minimum feature that affects the results. Momentum uses the "method of moments" to solve for currents and the fields are inferred from the currents. The distributed element is broken into discreet cells. Each cell is replaced with a capacitor to ground and an inductor to each neighboring cell. The major task of the simulator is to solve for the currents by inverting large matrices. Page 19 of 83 4.3 LTCC features with some application LTCC technology has per nature a number of interesting features applications: Very good electrical characteristics and stability up to millimetre waves. The inherent properties of the material are insensitive to moisture influence and degrade largely many organic compositions. Depending on the material used, dielectric constants are between 6 and 9 in GHz range, loss tangent between 0.001 and 0.006. Very good outstanding dimensional and mechanical stability because of glass ceramic nature. Not only the TCE is low from 5 to 7 ppm/ C the thermo mechanical properties have very elastic reversible behaviour largely beyond the use of the temperature range. Low TCE is a great advantage of ceramics close to semi conductor (Si, GaAs, LnP) TCEs facilitating their chip use in chips and wires or flip chip form.. LTCC very adapted to short wedge bonding due to patterning and machinery precision ability. Its also allows better maintaining alignment over temperature span. Firing temperature below 900 C make it good thermal conductivity because of dielectric has only very fair intrinsic thermal conductivity value from 2 to 4 W/m. C and is approximately much higher quality than organic PCBs. More importantly there was improvement on the application of thermal up to 50W/m. C . Very dedicated patterning from direct printing and photo- imageable. 3D capability to design as cavities, holes and fences. Hermetic and Brazing feasibility. Proven to be reliability and cost effectively demanding on applications like aerospace and automotive. Page 20 of 83 Some Application and Example by using LTCC technology No. Application Frequency 1 Edge Coupled Band Pass Filter (24.1~25.5) GHz 2 Wilkinson Power Divider Networks (Strip-line & MicroStrip) (17.~26) GHz 3 Shield Strip-line Band Pass Filter with ground to ground via chains (24.5+25.5) GHz 4 Multiplier (x3) (8.5~25.5) GHz 5 Balanced Push Pull Amplifier 6 Band Pass Filter 7 Packaged Microstrip BP-Filter Photo GSM 900 (24.5~25.5) GHz (39~43) GHz Courtesy by http://www.ltcc.de/en/examples.php Page 21 of 83 4.3.1 LTCC Process Slitting: Greensheets are shipped on a Roll and tapes have to be unrolled onto a clean, stainless steel table. The sheet has been cut with a razor, laser or a punch into parts (these parts have to be a little larger than the blank size, if the material needs to be preconditioned). If a laser is used it is very necessary to control the power to avoid firing of the sheets. (a) Preconditioning: Some tapes need to be preconditioned (e.g. Dupont GreenTape); that means the greensheet has to be baked for about half an hour at 120°C (depends on manufacturer and material). Normally the tapes are shipped with an applied foil / bake sheet, which has to be removed before lamination at the latest; some processors use this foil as a filling mask for the vias. (b) Blanking: A blanking die is used to create orientation marks and lamination tooling holes and the final working dimension in case of to be preconditioned tapes. (c) Forming vias: Vias may be punched or drilled with a laser (low power). Filling vias: Vias can be filled with a conventional thick film screen printer or an extrusion via Page 22 of 83 filler. In the first case the tape has to be placed on a sheet of paper which lays on a porous stone; a vacuum pump holds the tape on his place and is used as an aid for via filling. Note: The possibilities of this method are limited; the vias must have a larger diameter than tape thickness. The smallest possible size of vias to be filled also depends on the viscosity of the paste. The second possibility to fill the vias is to use a special extrusion via filler that works with pressures of about 4 to 4.5 bar. Both methods need to have a mask; this mask should be made of a 150-200mm thick stainless steel. An alternative to that is to use the (Mylar-)foil the tape usually is applied on. For the filling of blind vias it is advisable to form the holes concerned of the masks a little smaller than the diameter of the blind vias. Otherwise there could occur problems with the filling rate. Printing: Cofireable conductors etc are printed on the green sheet using a conventional thick film screen printer. The screens are standard (250 – 325) emulsion type thick film screens. Just like the via printing process, a porous stone is used to hold the tape in place. Printing of the conductor tends to be easier and of higher resolution than standard thick film on alumina. This is due to the flattness and solvent absorption of the tape. After printing, the vias and conductors have to be dried in an oven at 80 to 120°C for 5 to 30 minutes (depends on material); some pastes need to level at room temperature for a few minutes before drying. Note: Resistors may vary their value when terminated with different conductors. With the help of a Micro-Screen printer, it is possible to print conductors with a 50mm line resolution. Register for Lamination: Each layer is placed in turns over tooling pins. Some processors use a heat pliers to fix the sheets in turns one on top of the other. Lamination: There are two possibilities of laminating the tapes. The first is named uniaxial lamination; the tapes are pressed between heated platens at 70°C, 200 bar for 10 minutes (typical values). This method requires a 180° rotation after half the time. The uniaxial lamination could cause problems with cavities / windows. This method causes higher shrinking tolerances than the isostatic lamination. Page 23 of 83 The main problem is the flowing of the tape; that results in high shrinkage tolerances (especially at the edge of the part) during the firing and varying thicknesses of single parts of each layer (causes hard problems on the high frequencies sector). The second way is to use an isostatic press. The stacked tapes are vacuum sealed in a foil and pressed in hot water (temperature and time are just the same like using the uniaxial press). The pressure is about 210 bar. Note: deep cavities and windows need to have an inlay during lamination. Cofiring: Laminates are fired in one step on a smooth, flat setter tile. The firing should follow a specific firing profile, what causes the need of a programmable box kiln. A typical profile shows a (slow) rising temperature (about 2-5°C per minute) up to about 450°C with a dwell time of about one to two hours, where the organic burnout (binder) takes place; then the temperature has to be rised up to 850 to 875°C with a dwell time of about 10 to 15 minutes. The hole firing cycle lasts between three and eight hours (depends on the material; large / thick parts cause the need of a modification of the firing profile). Note: especially resistor pastes need to have defined firing conditions (temperatures);Otherwise they vary enormous in value. Postfiring: Some materials need to be postfired; that means the paste is to be applied after firing the tape and has to be fired again. The postfiring conditions depend on the used material and vary in a wide range. Note: especially resistor pastes need to have defined firing conditions (temperatures); Otherwise they vary enormous in value. Singulation: If the fired parts have to be cut into smaller pieces or other shapes, there are three different ways to realize. The first is to use a post fire dicing saw, which is a common method and works very well for rectangular shapes; it holds tight outside dimensional tolerances and allows high quality edges.The second possibility is to use an ultrasonic cutter; the final part shows low tolerances and may have unusually shapes. This process is very slow and expensive.The third method uses a laser to cut the fired tape; the tolerances are tight, but the quality of the edges is very bad. Page 24 of 83 4.4 Microstrip Common practise use in planar printed circuit boards (PCBs). When dealing with actual RF circuits need to consider the higher frequencies behaviour of conducting strips etches on the PCBs. The ground plane below carries conductors traces help excess field leakage and reduces radiation loss. The use of PCBs simplify the access to the active and passive devices on the board and reduces the cost of the manufacturing process in the transmission lines. Below Fig 4.4.A Fig 4.4.A One major disadvantage of the single layered PCBs is that they have rather high radiation loss and interference (CrossTalk) between nearby conductor traces. The leakage depends on the relative dielectric constants in the electric field line displays for Teflon epoxy ( r 2.55) and alumina ( r =10.0) dielectrics. Below Figure 3.4.B is an example show how the electric field leakage as a function of dielectric constant. Figure 4.4.B To achieve high board density of the field line of the components layout: Use substrates with high dielectric constants to minimum cross coupling. Use Multilayered techniques to achieve balanced circuit board designs where the microstrip line is sandwiches between two ground plane, resulting 3 layer configuration. Page 25 of 83 Configuration used for low impedance, high power application. Current and Voltage Flow confined two plates separated by dielectric medium. 4.4.1 Other types of MICROSTRIP Several derivates of microstrip lines can be used as alternative structures for microstrip filter implementations. These include suspended and inverted microstrip lines, multilayered microstrip,thin film microstrip and valley microstrip. In addition there are many types of transmission lines that are interest of filter designs. Suspended and inverted microstrip lines in Figure 4.4.1.A provides a higher Q (500~5000 for normal Conductor) than the conventional microstrip lines[6]. Normally they are enclosed for filter applications.Although they can be used for realizing any types of filters, the wide range of impedance values achievable makes them suitable for bandpass filter. By using thin electric substrates of low dielectric constant, dielectric loss can be minimized[7]. (a) Suspended microstrip line (b) Inverted microstrip line (c) Suspended or inverted Microstrip line Figure 4.4.1.A Page 26 of 83 Typically there are 5 types of Microstrip filter: 4.4.2 1. 2. 3. 4. 5. Low-Z / High-Z Lowpass Lowpass using shunt stubs Parallel-coupled bandpass End-coupled bandpass Branch-line bandpass General features of microstrip filter are: Low Cost Easily integrated with active device Except that they have: Lossy, low Q, performance very poor Low power handling Spurious in free range Page 27 of 83 4.5 Microstrip Resonator Microwave resonant structures are extensively used in a variety of applications, such as filters, oscillators and tuned amplifiers [6]. At low frequencies, resonant structure are composed of the lumped elements. As the frequency of operation increases, lumped elements in general cannot be used because the dimensions of lump resonator circuit become comparable to the wavelength and this may cause energy loss by radiation. At microwave frequencies, resonant structures using cavity resonators and microstrip resonators are commonly employed. Since the project is primarily devoted to microstrip filter circuits. Emphasis is placed on microstrip resonatorsonly. The choice of microstrip resonators for filter design mainly attributed to easy of fabrication, low cost, lightweight, reproducibility and greater flexibility in the design. Its main drawback is its much higher insertion loss compared with the other types of resonators such as cavity and dielectric resonators. The distributed line resonators shown in Figure 3.4(c) and (d) may be termedquarter-wavelength resonators, since they are long, go / 4 where g0 is the guidedwavelength at the fundamental resonant frequency f0. They can also resonate at otherhigher frequencies when f (2n – 1) f0 for n = 2, 3, · · · . Another typical distributedline resonator is the half-wavelength resonator, as shown in Figure 3.4(e), which is go / 2 long at its fundamental resonant frequency, and can also resonate at f nf0 for n = 2, 3, · · · . It will be demonstrated later when we discuss filter designsthat this type of line resonator can be shaped into many different configurations for filter implementations, such as the open-loop resonator [8]. (a) (d) (b) (c) (e) FIGURE 3.5 Some typical microstrip resonators: (a) lumped-element resonator; (b) quasi-lumped element resonator; (c) go / 4 line resonator (shunt series resonance); (d) go / 4 line resonator (shun resonance); (e) go / 2 line resonator. Page 28 of 83 4.6 MicroStrip Transmission Line Before digging into the microstrip topic let's spend a minute on transmission lines. see Figure If you ignore parasiticresistances each section could be modeled as a small serial inductance because any wire has a nonnull inductance and as a small capacitor between the wire and the ground because the central wire is not far from the grounded shield. These parasitic inductances and capacitances are roughly proportional to the length of the small section so they can be noted L.dZ and C.dZ with L and C in henries per meter and farads per meter. Therefore the wire can be approximated as a serially connected set of identical L.dZ/C.dZ networks. If we apply a voltage on one end of the cable some current will flow untilall capacitors are charged. If we are well rich and have an infinite length of cable this current will flow forever. And if we apply an AC input you will get a given impedance. This impedance is what is called the cable‘s characteristic impedance. In fact it can be easily demonstrated that this characteristic impedance is simply the square root Imagine you have a piece of coaxial cable divided into a large number of small sections each of length dZof L/C. Just remember that the characteristic impedance of the cable increases with L and decreases with C. Transmission line can be modeled as a succession of small L/C networks. The mathematical relationship between the L and C parameters and the characteristic impedance of the line is simple to apply and slightly more complex to demonstrate. Various forms of planar transmission lines have been developed for use in MIC. The stripline, microstrip line, slot line and coplanar waveguide are some representative planar transmission lines. Microstrip line is one of the most popular types of planar transmission lines that will be described here. The geometry of a microstrip line is shown in Fig3 .5a. A conducting strip (microstrip line) with a width W and a thickness t is on top of a dielectric substrate that has a dielectric constant εr and a thickness h. The bottom of the substrate is a conducting ground plane. Page 29 of 83 Fig 3.6 (a) Geometry of a microstrip transmission line The microstrip line is an inhomogeneous transmission line. The field between the strip and the ground plane are not contained entirely in the substrate but extend within the two media namely, the air above and the dielectric below. Therefore, the mode propagating along the microstrip is not purely transverse electromagnetic (TEM) but quasi-TEM. Extensive literature dealing with analytical and numerical solutions of this medium exists. Many simple closed-form empirical formulations have been reported .For fast approximation of the microstrip characteristic impedance, we considered the effect of conducting strip thickness t=0 in the calculation. How do we control the characteristic impedance of a microstrip track? Usually with the only parameter that we can easily manage on your LineCal tool track width synthesize method and equation in 3.52. Intuitively if the track is wider the capacitance between the track and the ground plane will increase and the characteristic impedance will decrease. If the track is thinner its inductance and its characteristic impedance will increase too. So there should be a given track width that corresponds exactly to 50 Ω at least for a given PCB technology. This width is dependent on the PCB substrate FR4 is the most common through its dielectric constant and the PCB thickness 1.6 mm or 0.8 mm for double-sided designs and slightly on the copper thickness which is 35 μm most of the time. and the usual Roughly a 50-Ω track corresponds to a 3-mm wide track on a standard 1.6-mm thick PCB and to 1.5 mm on a 0.8-mm PCB. For RF projects simply because the tracks have a more manageable width. In summary whenever we design a low frequency project we must always use tracks with the width for proper impedance matching with a full ground plane on the opposite layer. The only exception is when the length of the track is short compared to the signal‘s wave length e.g. a couple of millimeters as in case impedance matching may be neglected. Page 30 of 83 4.7 Coupled Microstrip lines Coupled microstrip lines are widely use for implementing microstrip filters and directional couplers [9]. Figure 4.7.A shows the cross section of a pair of coupled microstrip lines. The two microstrip lines of width w are placed side by side with a separation s on a dielectric substrate above a ground plane. The microstrip lines can be arranged in parallel or edge-coupled configuration. This coupled line structure supports two quasi-TEM modes. They are the even and odd-mode excitations. Figure 4.7.B illustrates the field distribution for the even and odd-modes on coupled microstrip lines [9]. In the even-mode excitation, both microstrip conductors are of the same potential and on which the same currents exist. The odd-mode excitation corresponds to the conductors being at opposite potential. Thus the currents on the two conductors are equal in amplitude but of opposite sign. The even and odd modes have different characteristic impedances. Their values become equal when the separation between the conductors is very large, that is the lines are uncoupled. Because coupled microstrip lines are not pure TEM modes, the velocities of propagation of the two modes are unequal. The different in phase velocity result in the microstrip coupled filter having an asymmetrical passband response, deteriorating the upper stopband performance and moves the second passband towards the center frequency [10]. To overcome this problem, capacitive compensation of phase velocity in parallel microstrip filters has been employed. Figure 4.7.A: Cross section of a pair of coupled microstrip lines Figure 4.7.B: The field distribution for the even and odd modes on coupled microstrip line Page 31 of 83 In the static approach, the fundamental mode of wave propagation in a microstrip is assumed to be pure TEM. The characteristic impedances and the effective dielectric constants of the two modes can characterize the coupled microstrip lines. Figure 4.7.C shows the capacitances representation of symmetrical coupled lines. Cp denotes the parallel plate capcitance between the conductor strip and the ground plane. Cm denotes the coupling capacitance between the two conductors. By dividing the circuit along the symmetry axis as shown in Figure 4.7.D, the capacitance Cm can be divided into a series circuit of two capacitances, 2Cm. Figure 3.7.C Figure 3.7.D In the even-mode excitation, the symmetry plane PP' as shown in Figure 4.7.D acts as magnetic wall (open circuit). The determination of the even-mode capacitance reduces to finding the capacitance of either line with the plane of symmetry PP' by a magnetic wall as shown in Figure 4.7.E. This results in a great simplification of the problem. Similarly, in the odd-mode excitation, the symmetry plane behaves as an electric wall (short circuit). The determination of the odd-mode capacitance reduces to finding the capacitance of either line by replacing the plane of symmetry by an electric wall as shown in Figure 4.7.F. Figure 3.7.E Figure 3.7.F Page 32 of 83 The even and odd mode capacitances Ce and Co are given by: Ce = Cp Co = Cp +2Cm The even and odd mode characteristic impedances Zce and Zco can be obtained from the capacitances. Z ce Z co 1 c C e C oe 1 c C 0 C 00 where Coe and Coo are the even and odd mode capacitance for the coupled microstrip line configuration with air as dielectric. The effective dielectric constant εree and εreo for even and odd mode due to the unequal phase velocities of the two modes are ree Ce C oe re0 C0 C 00 An excitation of symmetric coupled line can be considered as the superposition of even and odd modes. The understanding of basic concepts for microstrip lines and coupled microstrip lines are useful for design of microstrip resonator filters. 4.8 FR4 Process Methodology Electroplating a tin/lead alloy circuit pattern over the copper foil as an etch resist is a very common fabrication method. The subtractive method (chemical etch) of selectively removing copper continues to be in wide use throughout the PCB industry. When SMOBC boards are processed, the tin/lead is chemically stripped leaving only the copper conductors and component attachment sites free of plating. Plasma may be used to achieve etchback. Where appropriate, standard FR-4 desmear and/or etchback processing can be used Copper coated with epoxy or polymer solder mask to prevent exposure processes. Permanganate preconditioners (swellants) using non-aqueous solvents such as NMP (N-Methyl Pyrolidone) have been used successfully to provide 2-point etchback. Plating and/or coating options include alloys and chemistry. Page 33 of 83 4.8.1 Plating Process Options 4.8.2 Hot Air Leveled Tin/Lead (HASL) Electroplated Tin/Lead Electroless Gold over Nickel Electroplated Gold over Nickel Tin/Lead Alloy Plating With the hot air leveling method, tin lead is applied to the board after solder mask application. Coated boards are cleaned, fluxed and dipped into molten solder and while the alloy is still in a liquid state, excess material is blown off the contact surface leaving a alloy coated surface. The HASL plating process is widly used and generally compatible with reflow solder assembly processes however, inconsistent solder volume and flatness may not be suitable for boards using fine pitch devices. 4.8.3 Ni/Au Electroless or Immersion Plating Process for Soldering Electroless nickel/gold is applied over the exposed bare copper after solder mask coating process. With this process, the fabricator will typically use the tin/lead plated circuit pattern as an etch resist, strip the tin lead after etching as noted above but, instead of applying solder alloy to the exposed attachment sites and holes, the boards are immersion coated with the nickel/gold alloy. 4.8.4 Alternatives to Alloy Plating Adding solder alloy to the board after solder mask application is costly and subjects the substrate to extremely stressful conditions. With tin/lead coating for example, the board is thrust into molten solder, extracted and blasted with air to remove excess tin/lead material. Thermal shock can cause delamination of the substrate structure, damage to plated holes and defects that may affect long term reliability. Nickel/Gold plating, although less stressful, is not a technology that is available from all board fabricators. As an alternative to plating, many companies have found success and an economic advantage as well as a flat attachment surface with organic preservatives or pre-flux coatings over bare copper. 4.8.5 Process on Organic Solderability Preservative (OSP) As a means of retarding oxide growth on the bare copper attachment sites and via/test pads, a special preservative or inhibitor coating is applied to the board. Organic/nitrogen coating materials such as Benzotriazole and Imidazole are developed to replace the alloy finishes described and are available under trademark names from several sources. Chemical inhibitors compounds are implent to the bare copper by dipping or spray coat. Before implent the material, the copper surface is complled with void of all oxidation and oil residue. A typical cleaning agent for copper surfaces is Alkaline and Nitric Acid. The acid definitely acts as a mild etchant leaving a matte texture. The process flow chart illustrated in Figure 4.8.5.A is an example of the steps necessary to assure that the bare copper device attachment sites are protected from oxidation before the solder attachment of surface mounted devices. Page 34 of 83 Figure 4.8.5.A OSP are utilization in the latest part of process in the fabrication of PC boards. Solder mask, silk-screen legend and electrical testing should be complled before coating. The chemical film coating is to be cleaving only to the exposed copper alloy and is formulated to dissolve when the flux is energized during the solder process. Shelf life is severley . To maximize the storage life of the coating, packaging should be sealed and boards stored in a low humidity environment and one should avoid physical contact with the device attachment sites. 4.8.6 Assembly Process Compatibility The organic coated copper is compatible with most soldering processes and can decrease defects attributed to the uneven surface typical of hot air solder leveled (HASL) boards. OSP Provides a Uniform Solder Paste Pattern Minimizes Skewing When Placing Fine Pitch Devices Improves Overall Solder Process Yield* Compatible With Most Soldering Technologies * Solder process related defects on the higher density PC boards cannot be totally eliminated however, when compared directly to HASL type boards, the OSP board will typically have 15-20% fewer solder process related defects on fine pitch devices. Page 35 of 83 4.8.7 Limited Shelf Life for OSP Coated Boards Solderability testing should be performed on boards that have been stored for over six months. If the solder quality is degraded because of a breakdown of the coating, the material can be stripped in an alkaline solution and recoated without physical stress or damage to the PC board structure. Other factors that will affect solderability of coated boards is surface contamination caused by physical contact of the boards surface by inspection personnel or assembly operators. Those handling OSP circuit boards should pick up the board holding only the edges or use gloves because the oils typically present on fingers and hands contain salts and acids that will easily degrade the coating material. 4.8.8 Benefits of Coated Surfaces Attachment Surface is Flat and Uniform Low Thermal Stress on Board Storage Life is Good (but not unlimited) Excellent Solder Process Yield Each of the coating technologies have their advantages but assembly process complexity, solder/flux material and cleaning methods will greatly influence the overall success of the manufacturing quality and cost. 4.8.9 Concerns of Coated Boards 4.8.10 Deteriorates in High Humidity and Temperature\ Limited (6-12 month) Shelf Life Physical Contact Will Degrade Coating Exposed Copper Will Tarnish w/o Solder Coating Advantage on FR-4-86 material for Microwave and RF applications FR4 is a sophisticated and well established substrate technology with low initial and production costs. Not suitable for high frequency application because of it losses. Low tolerance in dielectric constant (RO3003) & electrical strength under both dry & humid conditions. In addition, it has flame resistance of at least Class I in accordance with NEMA test method 7.11 High TCE (close to Cu and Al) Capable for multilayer modules with prepreg technology Large circuit area possible >(20 x 20) inch sq Page 36 of 83 4.8.11 ADS implementation 4.8.11.1 Calculate width & 50Ω impedance for LTCC & FR4 The width of the microstrip can be pre-determined by line cal synthesize method to obtain 50Ω impedance. Since for a start we need to input all the parameter specification including dielectric constant to fine tune the process. Attach below in Figure 4.8.11.1.A for LTCC and Figure 4.8.11.1.B for FR-4. Er=7.4, Mur=1.0,H=1060 m , Hu=3.9e+3.4mil, T=17 m , Cond=4.1e7, Tan D=0.001, Freq=30GHz Zo=50Ω, E_eff=180ºC. W=1925.49 m approximate = 1930 m Figure 4.8.11.1.A Er=4.7, Mur=1.0,H=1600 m , Hu=3.9e+3.4mil, T=17 m , Cond=5.8e7, Tan D=0.02, Freq=1.5GHz, Zo=50Ω, E_eff=180ºC W=2887 m approximate = 2890 m Figure 4.8.11.1.A Page 37 of 83 4.8.12 Calculation Method 4.8.12.1 LTCC W /h 1 W 1930 1.82 h 1060 value is greater than 1. re r 1 2 r 1 h 1 12 W 2 0. 5 7.4 1 7.4 1 1930 1 12 2 2 1060 4.869 0. 5 re where r is the delectric constant & re is the effective dielectric constant of a microstrip W W Zc 1.393 0.677 In 1.444 re h h 1 120 1930 1930 1.393 0.677 In 1.444 4.869 1060 1060 50 1 4.8.12.2 FR4 W /h 1 W 2900 1.8125 h 1600 value is 1. re r 1 2 r 1 2 h 1 12 W 0 .5 4.7 1 4.7 1 1600 1 12 2 2 2900 3.52 0 .5 re Page 38 of 83 W W Zc 1.393 0.677 In 1.444 h re h 4.8.13 1 120 2900 2900 1.393 0.677 In 1.444 1600 3.52 1600 50 Determine the microstrip guided wavelength 1 Once the effective dielectric constant of a microstrip is determined, the guided wavelength with fundamental resonant frequency is given by as shown below: 4.8.13.1 For LTCC g 0 f (GHz ) re where 0 is the free space wavelength of operating frequency g 0 f (GHz ) re 3 10 8 30 10 9 4.869 3.5.3.1(a) 453.189m For half wavelength micro-strip: l g 2 226.59m 4.8.13.2 For FR4 g 0 f (GHz ) re 3 10 8 1.5 10 9 3.52 3.5.3.1(b) 5681.81m For half wavelength micro-strip: l g 2 2840.905m Page 39 of 83 5 FILTER IMPLENTATION IN ADS 5.1 Setting of substrate Parameters in LTCC A prototype design was designed and mapped onto BPF using ADS simulation software. The most difficult parts when we set the dielectric constant to 7.4 have to set the length and the width of the microstrip lines to overlap the resonators. The passing criteria of the S11 must be less than -10dB and the S22 must be as flat as possible. Many experiments have been carried out. To achieve the passing criteria of the S11 & S22, I have to play around the resonators length, width and overlapping. I have attached how to set the ADS software and the design of the simulation result behind appendix . Since both side of the resonator are symmetrical, I will only point out the changes. Page 40 of 83 5.1.1 Set up of Montenum under ADS Refer to Explanation on Chapter 5 and Appendix C. Page 41 of 83 As we can see from the graph from the 10 simulation results at appendix, when increasing the length not more than 1555μm, result become very stable but in the meantime don’t forget about the overlapping it’s very critical. When the resonator began to shift from (0~120)μm, I discovered that the S11 began to shift lower and lower up to 40dB. Comparing of Fig 1, Fig 9 & Fig 10, all can achieve the specification given by tutor. But the main point is that to achieve gratifying result, Fig 9 given the best result for this BPF fractional bandwidth of 3%, return loss at -40.8dB , insertion loss at 3.12dB at centre frequency 30.23GHz. As I can conclude that the width and spacing of the lines determine the filter characteristics, with narrow spacingbeing required for broad pass bands. Narrow pass bands thus require larger spacing which results in less coupling between the elements and thus increased loss. Other filtering structures are possible based on coupled line arrangements where lowloss or narrow bandwidths are required. Page 42 of 83 5.2 Setting of substrate Parameters in FR4 A prototype design for FR4 was designed and mapped onto BPF using ADS simulation software. The most difficult parts when we set the dielectric constant to 4.7 and the loss tangent of 0.02dB given by the manufacturer specification have to set the length and the width of the microstrip lines to overlap the resonators. The passing criteria of the S11 must be less than -10dB and the S22 must be as flat as possible. After synthesis from LineCal, we need to pre-determined the width. As I say calculation may not be so accurate so we need to fine tune. After fine tune, it came to meet the S11 & S21 desired result. We also have to make sure the input and output ports need to set 50Ω for impedance matching as shown in figure 4.2.d Page 43 of 83 Figure 4.2.d I also test out the most very basic of the microstrip attached behind the appendix to to see whether the frequency will shifted more than 3GHz. From the result attached result in figure 4.2.e, the best result simulation at point 3. Page 44 of 83 Figure 4.2.e Gap between the microstrip and resonator also play important part for the S11 and S21 simulation. Refer to appendix for more simulation result. When the gap reaches on point 5, S11 result getting -23.966dB and S21 result getting -3.166dB As I say before even with LTCC, the width and spacing of the lines determine the filter characteristics, with end gap spacing being required for broad pass bands. End Gap coupled thus require larger spacing which results in less coupling between the elements and thus increased loss. Other filtering structures are possible based on coupled line arrangements where lowloss or narrow bandwidths are required. Page 45 of 83 6 FABRICATION ON FR4 END GAP COUPLED Before we send for fabrication, we need to give the supplier our gerber file. For the ADS itself we export each layer of file send to the supplier as shown in Figure 6.C. Note: Format Version should be tell to supplier because of their cad version may be different. Figure 6.A. Figure 6.B. 16.89mm 136mm Figure 6.C Page 46 of 83 6.1 Process of FR4 from supplier Mentioned in 4.8.5 OSP are utilization in the latest part of process in the fabrication of PC boards. Solder mask, silk-screen legend and electrical testing should be complled before coating. The chemical film coating is to be cleaving only to the exposed copper alloy and is formulated to dissolve when the flux is energized during the solder process. Shelf life is severley . To maximize the storage life of the coating, packaging should be sealed and boards stored in a low humidity environment and one should avoid physical contact with the device attachment sites. Page 47 of 83 6.2 Hardware Mounting 1 ( Initial Design) After fabrication, we need to break away all sided PCB. Assemble all 4 sided PCB together with screw and nuts. Solder 2 input and output ports with SMA Jack connector. But in the end, I realize that when doing mounting all four PCB to the connector the 50 ohm impedance very difficult to solder the trace in Figure 6.2.A. So I come out another assemble PCB design on Figure 6.3.B Break Away all 4 sided PCB. Figure 6.2.A Page 48 of 83 6.3 Hardware Mounting 2 ( Final Design) Figure 6.3B shows the fabricated FR4 End Gap Coupled Band BPF of which size is 136 x 17 x 1.6mm. Openings were made to probe the CPW pads on the third layer for direct measurement without any additional vertically connected vias. Because the FR4 board all conductors including transmission lines and resonators were designed considering the shrinkage. Figure 6.3.B Page 49 of 83 7 HARDWARE MEASUREMENT Hardware measurement is performed firstly in SIM LABORATORY RM 5.0.6 with the following measuring equipments and tools: 1) Agilent VNA Network Analyzer E5062A (Figure 7.A) 2) 2m BNC cables x 2 (Figure 7.B) 3) SMB Female Jack Adapter (Figure 7.C) (Figure 7.A) 7.1 (Figure 7.B) (Figure 7.C) Hardware Measurement Set Up The following steps are carried out in the process of set up the equipment and measuring the filter. 1. Turn on the VNA Network Analyzer E5062A. 2. Connect BNC cable to input to Port 1 and the output to Port 2. 3. Self calibration on the equipment, which includes cal “Short” and “Open”. 4. Set the VNA frequency range from 1GHz to 3GHz. 5. Connect the filter design with the SMB Female Jack connector from one end of Port 1 and the other end of Port 2. 6. Measure filters response of S11 & S21. 7. Repeat Step 1 to Step 5 with OSP coating. 8. Save it to the disk. Page 50 of 83 7.1.1 Measurement Result Without Solderability Preservatives Figure 7.1.1.A Figure 7.1.1.B With Solderability Preservatives Figure 7.1.1.C Figure 7.1.1.D Parameter Measure Measured with OSP Measured without OSP Centre Frequency (fo) 1.494GHz 1.895GHz 1.953GHz Lower Band Edge (fL) 1.426GHz 1.801GHz 1.882GHz Upper Band Edge (fH) 1.550GHz 1.989GHz 2.025GHz Fractional Bandwidth 8.30% 9.90% 7.73% Min insertion loss -3.148dB -10.101dB -17.84dB -24.21dB -22.577dB -14.528dB Max return loss Figure 7.1.1.E Page 51 of 83 7.1.2 Summary of the end-gap coupled multilayered FR4 BPF The s-parameters of the BPF are measured and the insertion loss and the return loss are plotted in Fig.7.1.1.E with the EM and measuring simulation results. The measured data include the effect of microstrip feedthroughs. The minimum insertion loss of the BPF is 10.1dB at 1.8 GHz, and the fractional bandwidth is 9.9%. The measured insertion loss is about 7 dB lower than that of simulated value, and the center frequency is also shifted from 1.4 GHz to 1.9 GHz. We suppose that the shift of the center frequency and the loss are mainly due to the oxidation without any OSP coating and the simulated and measured result vary. The EMsimulation and at 1.5 GHz in the measurement whichwas not expected in the first trial ideal series capacitor model. The first trial circuit was optimized in the final layout to an electromagnetic structure of which coupling capacitances between the resonators in the circuit model, and which accounts the peaking in both EM simulation and measurement. in Figure 7.1.1.E 7.1.3 Conclusion The final design had a reasonable on return loss on (S11) return loss.but insertion loss more than 10dB after fabrication. However it does not meet the expectation from simulated result. One root cause maybe, it should be mount on test jig as I mentioned before previous chapter to get more grounding and stable frequency for the improved version.I have to fabricated a few more to see any changes or drifted frequency. Another root cause maybe cause by tangent loss and material use in microstrip line. Every PCB the specification given by supplier the loss vary so it better to get a multilayered in one PCB because I need to adjust all the 4 layered PCBs together, the coupling may not be able to archieve what I suppose to get the desired result. Connector issue also plays another apart. I using the 75 ohms SMB Jack because of the combination of 4 PCBs so that it can be soldered on the trace. It should be chosen on 50 ohm SMA female connector and consideration of thickness PCBs. Page 52 of 83 8 GANTT CHART Page 53 of 83 9 APPENDIX A [1] C. Q. Scrantom, “Where we are and where we’re going-II,” in IEEE MTT-S IMS Dig., 1999, pp. 193–200. [2] S. Pinel, S. Shakraborty, M. Roellig, R. Kunze, S. Mandal, H. Liang, C-H. Lee, R. Li, K. Lim, G. White, M. Tentzeris, and J. Laskar, “3D integrated LTCC module using _ BGA technology for compact C-band RF front-end module,” in IEEE MTT-S IMS Dig., 2002, pp. 1553–1556. [3] C.-H. Lee, S. Chakraborty, S. Yoo, D. Heo, and L. Laskar, “Broadband highly integrated LTCC front-end module for IEEE 802.11a WLAN applications,” in IEEE MTT-S IMS Dig., 2002, pp. 1045–1048. [4] C.-K. C. Tzuang, Y.-C. Chiang, and S. Su, “Design of a quasiplanar broadside end-coupled bandpass filter,” in IEEE MTT-S IMS Dig., 1990, pp. 407–410. [5] G. L. Matthaei, L. Young, and E. M. T. Jones, Microwave Filters, Impedance-Matching Networks, and Coupling Structures. New York: McGraw-Hill, 1964. Authorized licensed [6] K. C. Gupta, R. Garg, I. Bahl, and P. Bhartis, Microstrip Lines and Slotlines, Second Edition, Artech House, Boston, 1996. [7] J.-S. Hong, J.-M. Shi, and L. Sun, “Exact computation of generalized scattering matrix of suspended microstrip step discontinuities,” Electronics Letters, 25, 5, 1989, 335–336. [8] J.-S. Hong and M. J. Lancaster, “Couplings of microstrip square open-loop resonators for cross-coupled planar microwave filters,” IEEE Trans., MTT-44, Nov. 1996, 2099–2109. [9] R. Mongia, I. J. Bahl and P. Bhartia, RF and Microwave Coupled-line Circuits, Artech House, 1999. [10] J. Bahl, " Capacitively Compensated High-Performance Parallel Coupled Microstrip Filters," IEEE MTT-S Int. Microwave Symp. Dig., pp. 679-682, Page 54 of 83 9.1 Website http://www.rfglobalnet.com/article.mvc/Filter-Design-Considerations- 0002 http://www.rfglobalnet.com/article.mvc/The-ADS-Filter-Design-Guide-0001 http://www.syfer.com/doc_docs//an0023_LTCC_Filters.pdf http://www.ltcc.de/en/software.php http://amsacta.cib.unibo.it/423/1/JGM1_Massiot.pdf http://www.ltcc-consulting.com/LTCC_technology http://www.home.agilent.com/agilent/product.jspx?cc=US&lc=eng&ckey=1297113 &nid=-34346.0.00&id=1297113 http://www.plextek.com/papers/nordic.pdf http://en.wikipedia.org/wiki/Low_temperature_co-fired_ceramic http://www.ansoft.com/partnersindesign/16.pdf http://cc.ee.ntu.edu.tw/~jfkiang/electromagnetic%20applications/ch8_2004.pdf http://cc.ee.ntu.edu.tw/~jfkiang/electromagnetic%20applications/ch8_2005.pdf http://www.ursi.org/Proceedings/ProcGA05/pdf/D03.10(0626).pdf http://hehr-sachsen.de/files/3d_module_paper.pdf http://www.eecs.stut.edu.tw/~test3/ieet/word/961121.pdf http://books.google.com.sg/books?id=uU2rnznM2kC&pg=PA5&lpg=PA5&dq=LTCC+filter+on+ADS&source=bl&ots=lou QUvQvbQ&sig=wenGPm2Rkbtzv68fi1GXXYOWtA&hl=en&ei=MA6US4PuKcq2rAfI49jFCw&s a=X&oi=book_result&ct=result&resnum=10&ved=0CCMQ6AEwCTgU#v=onep age&q=&f=false http://www.ltcc.de/en/home.php http://en.wikipedia.org/wiki/Printed_circuit_board Page 55 of 83 http://www.edaboard.com/thread73580.html http://www.trianglecircuits.com/lead-free-finishes.html http://www.youtube.com/watch?v=JDKzQeWhAJM&feature=related http://www.ltcc-consulting.com/LTCC_technology http://chemandy.com/calculators/microstrip_transmission_line_calculator.htm Page 56 of 83 9.2 Appendix B Page 57 of 83 Page 58 of 83 Page 59 of 83 9.3 Appendix C: Software simulation for FR-4 Step 1: (MicroStrip P1) Step 2 : (Microstrip P1 & P2 with Resonator R1) Page 60 of 83 Step 3: (Microstrip P1, P2 & P3 with resonator R1) Step 4 : Page 61 of 83 9.3.1 Appendix D: Software simulation for FR-4 Test 1: (107 micronmeter) Gap between Microstrip & Resonator Page 62 of 83 Test 2: (207 micronmeter) Overlapping Gap between Microstrip & Resonator Page 63 of 83 Test 3: (407 micronmeter) Overlapping Gap between Microstrip & Resonator Page 64 of 83 Test 4: (807 micronmeter) Overlapping Gap between Microstrip & Resonator Page 65 of 83 Test 5: (679 micronmeter) Overlapping Gap between Microstrip & Resonator Page 66 of 83 9.3.2 Appendix E: Software simulation for FR-4 Gap between Microstrip & Resonator Test 1: (585 micronmeter) Page 67 of 83 Test 2 : : (2000 micronmeter) Gap between Microstrip & Resonator Page 68 of 83 Test 3: (3000 micronmeter) Gap between Microstrip & Resonator Page 69 of 83 Test 4: (4000 micronmeter) Gap between Microstrip & Resonator Page 70 of 83 Test 5: (5085 micronmeter) Gap between Microstrip & Resonator Page 71 of 83 Page 72 of 83 Test 6: (4085 micronmeter) Gap between Microstrip & Resonator Page 73 of 83 9.4 Appendix F: Meetings Logs Page 74 of 83 Page 75 of 83 Page 76 of 83 Page 77 of 83 Page 78 of 83 Page 79 of 83 Page 80 of 83 Page 81 of 83 Page 82 of 83 Page 83 of 83