CALIFORNIA STATE UNIVERSITY, NORTHRIDGE DESIGN OF TWO STAGE MICROWAVE AMPLIFIER AT 10 GHZ A graduate project submitted in partial fulfillment of the requirements For the degree of Master of Science In Electrical Engineering By Dheekshitha Puliyadi Rameshbapu December 2015 The Graduate Project of Dheekshitha Puliyadi Rameshbapu is approved: Dr. Ramin Roosta Date Dr. Benjamin Mallard Date Dr. Matthew M. Radmanesh, Chair Date California State University, Northridge ii Acknowledgement I would like to express my gratitude and appreciation to, all those who gave me the opportunity to complete this report. I would like to express my special appreciation and sincere gratitude to Dr. Matthew Radmanesh. He has been a great mentor and a great inspiration for me. My attitude towards learning and to achieve a better understanding of the subject has changed after taking courses under him. It was an honor for me to work under his supervision. . He has always made efforts to go through my project and help me improving my knowledge in every aspect. I would like to thank Dr.Ramin Roosta and Dr.Benjamin Mallard for providing their valuable suggestions. I would also like to thank the Department of Electrical and Computer Engineering for providing the facilities to complete this project. Also, I thank almighty, my husband, my parents, my in-laws, brothers, sisters and friends for their constant encouragement without which this assignment would not be possible. iii Table of Contents Signature page ................................................................................................................................. ii Acknowledgement .......................................................................................................................... iii List of Figures ................................................................................................................................... v List of Table .................................................................................................................................... vii ABSTRACT...................................................................................................................................... viii CHAPTER 1: INTRODUCTION ............................................................................................................ 1 CHAPTER 2: DC-CIRCUIT BIASING .................................................................................................... 3 2.1 Classes of Amplifiers Based On Operating Point ...................................................................... 3 2.2 Small Signal Analysis................................................................................................................. 4 2.3 DC-Bias Circuit Design .............................................................................................................. 4 2.3.1 FET Biasing ........................................................................................................................ 5 CHAPTER 3: AMPLIFIER DESIGN ....................................................................................................... 8 3.1 Transistor Selection .................................................................................................................. 8 3.2 Stability..................................................................................................................................... 9 3.2.1 K-β Test ................................................................................................................................. 9 3.2.2 µ- Parameter Test........................................................................................................... 10 CHAPTER 4: MINIMUM NOISE AMPLIFIER DESIGN ........................................................................ 11 4.1 Matching Network ................................................................................................................. 11 4.2 Minimum Nosie Amplifier Gain Calculation ........................................................................... 17 CHAPTER 5: MAXIMUM GAIN AMPLIFIER DESIGN......................................................................... 18 5.1 Unilateral Figure of Merit....................................................................................................... 18 5.2 Matching Network ................................................................................................................. 19 CHAPTER 6: TWO STAGE AMPLIFIER DESIGN ................................................................................ 25 6.1 Overall Noise Figure of Two Sage Amplifiers ......................................................................... 25 6.2 Complete Amplifier Schematic (RF and DC) ........................................................................... 26 CHAPTER 7: SIMULATION............................................................................................................... 28 CHAPTER 8: CONCLUSION .............................................................................................................. 63 REFERENCE ..................................................................................................................................... 65 Appendix A ..................................................................................................................................... 66 Appendix B ..................................................................................................................................... 80 Appendix C ..................................................................................................................................... 90 iv List of Figures Figure 1: Two Stage Amplifier Schematic ..................................................................................................... 2 Figure 2: NE 3210S01 Transistor Characteristics [8] ..................................................................................... 4 Figure 3: FET Biasing Circuit [1] ..................................................................................................................... 7 Figure 4: The Concept of Matching [2] ....................................................................................................... 12 Figure 5: MNA Input Lumped Elements ...................................................................................................... 14 Figure 6: MNA Output Lumped Elements ................................................................................................... 16 Figure 7: MGA Input Lumped Elements ...................................................................................................... 21 Figure 8: MGA Output Lumped Elements ................................................................................................... 23 Figure 9: Complete Amplifier Schematic (RF and DC)................................................................................. 27 Figure 10: RFMW Design Essential Stability Result ..................................................................................... 28 Figure 11: S-Parameter Simulation of NE3210S01 ..................................................................................... 29 Figure 12: S-Parameter Simulation Result .................................................................................................. 30 Figure 13: Stability Table............................................................................................................................. 30 Figure 14: Simulation Result for Stability and mag (delta) ......................................................................... 31 Figure 15: S-parameter Plot ........................................................................................................................ 32 Figure 16: VSWR of the Transistor .............................................................................................................. 33 Figure 17: Noise Figure of the Transistor .................................................................................................... 34 Figure 18: Minimum Noise Amplifier RFMW .............................................................................................. 35 Figure 19 : Amplifier Specification .............................................................................................................. 36 Figure 20: Parameter Check ........................................................................................................................ 36 Figure 21: MNA Input Matching Network .................................................................................................. 37 Figure 22: MNA Output Matching Network ............................................................................................... 38 Figure 23: Minimum Noise Amplifier (MNA) Design .................................................................................. 39 Figure 24: MNA Input matching Solution 1 with ADS ................................................................................. 40 Figure 25: MNA Input Matching Solution 2 with ADS................................................................................. 41 Figure 26: MNA Output Matching Solution1 with ADS............................................................................... 42 Figure 27: MNA Output Matching Solution 2 with ADS .............................................................................. 43 Figure 28: Power Gain of MNA ................................................................................................................... 44 Figure 29: Noise Figure of MNA .................................................................................................................. 45 Figure30: Overall Noise of MNA ................................................................................................................. 46 Figure 31: Maximum Gain Amplifier Main Page RFMW Essential .............................................................. 47 Figure 32: MGA Amplifier Specification ...................................................................................................... 47 Figure 33: Unilateral Gain Calculations ....................................................................................................... 48 Figure 34: MGA Input Matching Network with RFMW Essentials .............................................................. 48 Figure 35: MGA Output Matching Network with RFMW Essentials ........................................................... 49 Figure 36: Maximum Gain Amplifier (MGA) Design.................................................................................... 50 Figure 37: MGA Input Matching With ADS ................................................................................................. 51 Figure 38: MGA Output Matching with ADS ............................................................................................... 52 Figure 39: Power Gain of MGA ................................................................................................................... 53 Figure 40: Overall Noise of MGA................................................................................................................. 54 Figure 41: Noise Figure of MGA .................................................................................................................. 55 v Figure 42: VSWR of MGA ............................................................................................................................ 56 Figure 43: Two Stage Amplifier Design with ADS........................................................................................ 57 Figure 44: Impedances for M1, M2, M3, M4 Blocks ................................................................................... 58 Figure 45: Power Gain of Two Stage Design ............................................................................................... 59 Figure 46: S-parameter of Two Stage Design.............................................................................................. 60 Figure 47: Noise of Two Stage Design ......................................................................................................... 61 Figure 48: VSWR of Two Stage Design ........................................................................................................ 62 Figure 49: Minimum Noise Amplifier Input Elements Solutions ................................................................ 82 Figure 50: Minimum Noise Amplifier Output Elements Solutions.............................................................. 84 Figure 51: Maximum Gain Amplifier Input Elements Solutions.................................................................. 86 Figure 52: Maximum Gain Amplifier Output Elements Solutions............................................................... 89 vi List of Table Table 1: Comparison of Numerical values and Simulated Value…………………………….….63 vii ABSTRACT DESIGN OF TWO STAGE MICROWAVE AMPLIFIER AT 10 GHZ By Dheekshitha Puliyadi Rameshbapu Master of Science in Electrical Engineering This project is to design a two stage microwave amplifier with an overall gain of 29 dB and an overall noise figure less than or equal to 1 dB. The two stage microwave amplifier design consists of a Minimum Noise Amplifier Stage (MNA) followed by a Maximum Gain Amplifier Stage (MGA). For the amplifier design, I have used the RFMW essentials software which is provided by my professor Matthew M. Radmanesh, which helps to calculate the baseline solution, which is later used to design the two stage amplifier. Along with that I have used Agilent Technologies ‘Advanced Design System Software (ADS)’ to design the amplifier and also to calculate the required values for impedance matching. I have performed the simulations for the two stage amplifier design. I have used the transistor NE 3210S01 from NEC vendor for the two stage amplifier design. After transistor selection, I have calculated the DC biasing circuit for the two stage amplifier design. Then each stage is calculated using the ADS software and the results are displayed in the report individually for minimum noise stage and maximum gain stage. Then I have cascaded the two circuits and have achieved the overall gain of the project as 28.3dB and an overall noise figure of 0.8dB. Along with that VSWR, overall noise, S-parameter sweep and power gain simulation results of two stage amplifier design is simulated. viii CHAPTER 1: INTRODUCTION An amplifier is the basic element for a wireless communication system. The applications of amplifiers are universal. “In this design, my goal is to design a two stage amplifier and achieve an overall gain of 29 dB and an overall noise figure of 1dB or less at 10GHz”. The two stage amplifier design consists of a Minimum noise Amplifier stage and a Maximum Gain Amplifier stage. In RF/Microwave amplifier, the existence of noise plays a very important role in the overall design procedure and hence need to be reduced as much as possible before a design process is developed. “Minimum Noise Amplifier is a special case of a ‘Low Noise Amplifier (LNA)’ where, the noise figure circles are reduced to a single point and thus the design process is reduced to a single design choice” [4]. The main aim of a Minimum Noise Amplifier is reducing the noise of the signal and also makes sure that there are no alterations in the original characteristics of that signal. “The second stage is the Maximum Gain Amplifier (MGA), which is a special case of ‘High Gain Amplifier (HGA)’ design where, the input and output gain circles are reduced to single points and thus the design is reduced to a single design choice”[4]. Based on the microwave amplifier specifications for this project, NE3210S01, ‘a super low noise amplifier N-channel HJ-FET’ device is chosen. The transistor is then biased, which is used to drive the FET. The stability conditions at the required frequency are checked with the S parameters value taken from the data sheet. Once the conditions are met, the appropriate reflection coefficient π€OPT is chosen to determine the π€s and π€l in case of a minimum noise amplifier to achieve the minimum noise and for best VSWR at the output. In case of the Maximum Gain Amplifier, π€s and π€l are chosen as the complex conjugate of S11 and S22 in order to achieve the maximum gain. Thus, with the help of the matching networks, lumped elements for each stage are calculated. 1 The gain and noise figure for each stage is calculated with the matching network. The overall gain of the cascaded amplifier design is calculated by multiplying the gain of each stage and the results are plotted and verified. For the design process, ADS software is used and the project is done theoretically with no practical implementations. Figure 1, shows the two stage amplifier design schematic. M1 is the input matching network of the first stage (MNA) and M2 is the output matching network of the first stage (MNA). Similarly, M3 is the input matching network of the second stage (MGA) and M4 is the output matching network of the second stage (MGA). Figure 1: Two Stage Amplifier Schematic 2 CHAPTER 2: DC-CIRCUIT BIASING Among electronic circuits, signal amplification is the most important radiofrequency (RF) and microwave circuit functions. In recent times, the wireless communication revolution had provided an explosion of RF and microwave applications. Major benefits of transistor amplifiers versus tube amplifiers are smaller size, lighter weight, and higher reliability, a high level of integration capability, high-volume, high-yield production capability, greater design flexibility, lower supply voltages, reduced maintenance and unlimited application diversity. Transistors have much longer operating life and require much lower warming time. Nowadays, uses of microwave transistors (BJTs and FETs) have become popular. 2.1 Classes of Amplifiers Based On Operating Point Historically, amplifier class designations were related to the biasing of amplifier devices, 1. Class A: In this mode, each transistor in the amplifier operates in the active region for each cycle. This is the biasing scheme used in this project. 2. Class B: In this mode, each transistor is in the active region for approximately half of the cycle. 3. Class AB: In this mode, an amplifier operates in class A for small signals and in class B for large signals. 4. Class C: In this mode, each transistor is in active region for less than half of the signal cycle. They are used in radio-frequency applications. 5. Class D: It’s found in audio application. In vehicles, where it achieves high output levels, or in personal audio devices, where its efficiency contributes to long battery life. 3 2.2 Small Signal Analysis According to the signal level, amplifiers are classified as small signal mode and large signal mode. In small signal analysis, “the active circuit in which it is assumed that the signals deviate from the steady bias levels by such a small amount that only a small part of the operating characteristic of the device is covered and thus the operation is always linear”[4]. For small signal amplifier design, the biasing values of the transistor is determined first and connect the DC circuitry correctly to the RF portion of the amplifier. Design of an amplifier consists of two separate circuits: a. DC Circuit Design b. RF/MW Circuit Design. 2.3 DC-Bias Circuit Design In this amplifier design process we are using an FET transistor. At higher frequencies the device of choice is N-channel type, since the electrons being the main charge carriers have higher mobility and thus high speed. It has three components: source, drain and gate. The resistance of the current path from the source to drain is controlled by applying a voltage to the gate electrode by varying the depletion layer under the gate area and thus reducing or increasing the conductance of the path. FET’s gate input impedance is very large and the current through the gate for all practical purpose can be considered to be zero. Figure 2: NE 3210S01 Transistor Characteristics [8] 4 2.3.1 FET Biasing The following are the steps involved in FET biasing. ο· Gate to source junction is always reverse biased in a FET ο· Gate has to be at a negative voltage compared to source for N-channel ο· Drain to source DC supply is positive to enable majority carriers to flow from source to drain ο· A separate negative supply or alternatively a resistance (RS) is placed in the source lead ο· The current from drain to source (ID) would develop a voltage across RS with the source end being positive ο· The gate is connected to the other end of RS making it negative with respect to the source end ο· Gate current of FET is zero ο· Sometimes a large value of RS is required for better stability which thus increases the supply voltage for suitable value of VDS and RD ο· To avoid this and have more flexibility in choosing RS a supply voltage VGG is used at the gate ο· Since VGG is positive and gate current is zero, it can be derived from VDD with the help of potential divider FET biasing values from data sheet are as follows: Drain current ID = 10 mA Drain to source voltage VDS = 2V Gate to source voltage VGS = -3V Threshold Voltage Vt = -0.7 V Saturated Drain Current IDSS = 40mA 5 The FET biasing equations are discussed as follows. IDSS = K Vt2 K= πΌπ·ππ ππ‘2 = 40 0.49 = 81.63mA/V2 Thus the value of K is calculated to be 81.63mA/V2 From the voltage divider rule we have, VDD = RD ID + VDS + RS ID Assume VDD = 17V and RS = 0.5Kβ¦ RD = RD = ππ·π· − ππ·π - RS πΌπ· 17−2 10 - 0.5K RD = 1Kβ¦ The resistance R1 and R2 are calculated as follows VS = RS ID = 5V The gate voltage is calculated as follows VGS = VG – VS VG = VGS + VS VG = -3+5 = 2V VG = VDD ( VG = VDD ( π 2 π 1 +π 2 1 π 1+ π 1 ) ) 2 6 ( 1 π 1+ π 1 2 π 1 π 2 )= 2 17 = 7.5 Assume R1 =100 Kβ¦ and R2 = 13.3 Kβ¦ The biasing circuit for FET is shown in figure 3. Figure 3: FET Biasing Circuit [1] 7 CHAPTER 3: AMPLIFIER DESIGN The next step is amplifier design. The following steps are performed in order to achieve the required amplifier design. As mentioned earlier, the transistor selected for the design is NE 3210S01 FET. The S parameters of the transistor are selected at 10GHz, since we are designing the amplifier for the 10GHz. 3.1 Transistor Selection Based on the amplifiers specifications, “it is important to select an appropriate device such that, if the gain (G) is given we have to choose a transistor with typical Ηπ21 Η Ηπ12 Η > G that is in the desired frequency range” [4]. Alternatively, if the noise figure (FO) is given, we have to make sure that it is greater than the Fmin of the selected transistor, i.e., FO > Fmin [4]. The transistor is selected if it satisfies the following condition: Η π21 π12 Η > Specified Gain (G) Based on the microwave amplifier specifications for this project, NE3210S01, a super low noise amplifier N-channel HJ-FET device is chosen. 4.063 Η0.086 Η = 47.244 = 16.7dB > 29/2 = 14.5 dB (the desired gain) Thus for a two stage design, a maximum of 33dB gain is available and an overall noise figure of 1dB. From the data sheet, for 10 GHz frequency, the respective S parameters are taken. The data sheet NE321S01 is attached in the appendix (A). 8 Thus the values satisfy the condition, Ηπ21 Η Ηπ12 Η > G. The next step is to calculate the stability of the device. The transistor selected for the design is operating at an optimal operating point at VDS = 2V and ID = 10 mA. The S parameters of the transistor are run with the ADS software to verify if the values obtained are matching with the data sheet of NE321S01. They are terminated with 50β¦ terminations in the input and output port. The S-parameter result is obtained when the ADS simulation is performed. The values match with the data sheet provided in the appendix A. 3.2 Stability In any amplifier design, one of the very important considerations is the stability of the circuit under different source and load conditions. Stability is defined as, “the ability of an amplifier to maintain its effectiveness in spite of large changes in the environment such as temperature, frequency, source and load conditions, etc., in its normal operating point”[4]. In order to determine the stability of a FET, three steps are performed. They are the K-β test and the µ- parameter test. 3.2.1 K-β Test At the required frequency the stability of K and β of the selected transistor is first checked. β = S11 S22 – S12 S21 β = [(0.554∠−127.2π )*(0.268∠−86.8π )] – [(0.086∠18.9π )*(4.063∠51.3π )] β = 0.344∠−134.49π By substituting the S-parameter values of the transistor, β = 0.344∠−134.49π K= K= 1−Ηπ11 Η2 −Ηπ22 Η2 +ΗβΗ2 2Ηπ12 π21 Η 1−Η0.5542 Η−Η0.2682 Η+Η0.3442 Η 2Η0.086∗4.063Η = 1.058 9 When substituting the values in the above equation we get K=1.058 Thus we have β<1 and K>1. By meeting this condition we can conclude that the transistor is unconditionally stable. The results are verified with the help of the software as well. When simulated, we get the values of the delta and k and they are tabulated. Thus, the transistor selected at 10 GHz is unconditionally stable. 3.2.2 µ- Parameter Test To determine the unconditional stability of the device as well as its degree of stability to other devices, a new criterion has been derived that combines K-β parameter into a single parameter test and is often referred to as the µ-parameter test. The parameter µ is defined as: µ= 1−Ηπ11 Η2 ∗ βΗ+Ηπ π Η Ηπ22 −π11 21 12 = 1.068 In this case the value is found to be, µ=1.068 >1 Thus the device is unconditionally stable. By plugging in the values of the S-parameters, it is evident that the device is unconditionally stable with the help of RFMW design essential software and ADS. The Stability factor and the magnitude of delta are simulated and the graph is obtained. The transistor S-parameter plot is also simulated with the help of the ADS software. Also, the VSWR and the noise figure of the selected transistor are simulated and the results are obtained with the help of the ADS software. 10 CHAPTER 4: MINIMUM NOISE AMPLIFIER DESIGN “Minimum Noise Amplifier (MNA) design is a special case of Low Noise Amplifier (LNA) design where the noise figure circles are reduced to a single point ( π€opt) and thus the design process is reduced to a single design choice”[4]. From the data sheet attached in the appendix A, the value of the reflection coefficient is taken. For minimum noise amplifier design, the source reflection coefficient is taken as the optimum reflection coefficient in order to get best VSWR at the output. π€S = π€OPT The load reflection coefficient is calculated using the following formula π12 π21 π€πππ π€L = π€OUT* = (S22 + 1−π11 π€πππ )* Once the value of the source reflection coefficient and the load reflection coefficient are calculated, the input and output matching networks can be designed. At 10GHz the S- parameters for the transistor is S=[ π11 π21 π12 0.554 ∠−127.2π ]=[ π22 4.063∠51.3π 0.086∠18.9π ] 0.268∠ − 86.8π With the S-parameter values, the source and load reflection coefficient values are calculated π€S = 0.38∠97π β¦ = 34.5+j30.5 β¦ π€L = 0.251 ∠ 122.6π β¦ = 35.13+j15.85 β¦ 4.1 Matching Network “Matching is defined to be connecting two circuits (source and load) together via a coupling device or network in such a way that the maximum transfer of energy occurs 11 between two circuits. This concept of impedance matching is also called as tuning, and it is a very important concept in RF/Microwave frequencies since it allows: ο· Maximum power transfer to occur from source to load and, ο· Signal to noise ratio to be improved because matching causes an increase in the signal level” [4]. The most important design used in amplifier and oscillator design is shown as follows. Figure 4: The Concept of Matching [2] With the help of RFMW software, the matching network can be calculated. The input matching network is derived by moving from the center of smith chart to the source reflection coefficient. In Minimum noise amplifier design the source reflection coefficient is equal to the optimum reflection coefficient, which is taken from the data sheet. In this case the load is located outside the unit conductance and the resistance unity circle. There are four solutions possible, and for this design series C and shunt L (solution 1) is selected. Solution 1: Series C and Shunt L Series C1: jXS = j(-0.5) = −π ππΆππ −π (2π10∗109 )πΆ1 (50) 12 C1 = 0.636pF Shunt L1: jBP = j(-1.0) = −π ππΏππ −π (2π10∗109 )πΏ1 (0.02) L1 = 0.796nH The lumped elements are calculated from the smith chart and are shown in figure 5. Additionally, they are verified with the smith chart tool available in ADS software. The other three solutions are discussed in appendix B. 13 Solution 1 Figure 5: MNA Input Lumped Elements 14 The output matching network is derived by moving from the center of the smith chart to the load reflection coefficient. In Minimum noise amplifier design, the load reflection coefficient is derived with the help of the following equation. In this case the load is located inside the unit conductance. In this case, there are two solutions possible. π€L = ( S22 + π21 π12 π€πππ 1−π11 π€πππ )* π€L = 0.251 ∠ 122.6π β¦ Solution 1: Shunt C and Series L πππΆ Shunt C2: jBP = j(0.65) = ππ π(2π10∗109 )πΆ2 (0.02) C2 = 0.207pF Series L2: jXS = j(0.94) = πππΏ ππ π(2π10∗109 )πΏ2 (50) L2 = 0.754nH For this design, the shunt C and series L (solution 1) lumped element design is chosen for the output matching network and the values are calculated from the smith chart and are shown in figure 6. The second solution is discussed in appendix B. 15 Solution 1 Figure 6: MNA Output Lumped Elements 16 4.2 Minimum Nosie Amplifier Gain Calculation For the Minimum noise amplifier stage, we have terminated with a 50β¦ source and load. With the results of the input and output matching networks, shunt C and series L is selected for the input matching network and shunt L and series C for the output matching network. The matching networks are made up of passive components and have no inherent gain, thus are incapable of generating power. Since input and output matching networks are capable of increasing the degree of match in the circuit as the signal flows through, they can be considered to have a positive gain in a relative manner. The overall gain can be calculated as follows: GT = 1−Ηπ€π Η 2 2 ΗS21Η Η1−π€πΌπ π€π Η 1−Ηπ€πΏ Η Η1−π22 π€πΏ Η2 The above equation can be written as: GT = GS*Go*GL = 21.9 = 13.12(dB) Where GS = GL = 1−Ηπ€π Η Η1−π€πΌπ π€π Η2 1−Ηπ€πΏ Η Η1−π22 π€πΏ Η2 = 1.283 (ratio) = 0.1965 (ratio) 2 Go = ΗS21Η = 16.5 (ratio) π€IN =S11 + π12 π21 π€πΏ 1−π22 π€πΏ = 0.6299 ∠−132.35π β¦ The overall gain of the minimum noise amplifier is calculated as 13dB. The minimum noise amplifier (MNA), provides a gain of 13dB and an overall noise of 0.669dB which is a very good design, as the goal is achieved, which is the minimum noise. 17 CHAPTER 5: MAXIMUM GAIN AMPLIFIER DESIGN Gain consideration in an amplifier plays an important role in the design process. In order to obtain maximum gain, ‘input and output matching networks are simultaneously conjugated to the transistor’. Also, the entire amplifier system has to be matched to the system impedance. “Maximum Gain Amplifier design is a special case of a High Gain Amplifier design where the input and output gain circles are reduced to a single point and thus the design process is reduced to a single design choice” [4]. In order to achieve this condition, the following two conditions should be met: π€S = π€IN* π€L = π€OUT* 5.1 Unilateral Figure of Merit The next step in the amplifier design process is to check unilateral or bilateral analysis. In this case S12 ≠ 0, hence I have used unilateral design formulas. U= Ηπ12 Η Ηπ21 Η Ηπ11 Η Η π22 Η (1−Ηπ11 Η2 )(1−Ηπ22 Η2 ) U= Η0.086Η Η4.063Η Η0.554Η Η0.268Η (1−Η0.554Η2 )(1−Η0.268Η2 ) U = 0.08064 Where, “U is defined as the Unilateral Figure of Merit” which varies with frequency due to its S-parameter dependence. When π€S = S11* and π€L = S22*, GTU achieves its maximum value, GTU, max. Thus, the maximum error introduced using unilateral assumption is given by, 1 (1+π)2 < πΊπ πΊππ,πππ₯ < 1 (1−π)2 18 0.9936 < -0.086 < πΊπ πΊππ,πππ₯ πΊπ πΊππ,πππ₯ <1.0064 < 0.087 (in dB) The error is tolerable using the unilateral assumption because GTU, max = 14.16dB. The selected transistor provides the required maximum gain. Therefore, we can use the following conditions: π€S = S11* π€L = S22* These two conditions provide maximum transducer gain (GTU, max): GTU, max = GS, max * Go* GL, max Where GS, max = GL, max = 1 1−Ηπ11 Η2 1 1−Ηπ22 Η2 = 1.443 (ratio) = 1.59dB = 1.0774 (ratio) = 0.3237 dB Go = ΗS22Η2 = 16.508 (ratio) = 12.177dB Thus the transducer gain is calculated as GTU, max = 14.16dB 5.2 Matching Network The source and the load reflection coefficients are used to calculate the matching network for maximum gain amplifier design. An Input network is designed by moving from the center of the smith chart to the source reflection coefficient and they are calculated with the help of the smith chart shown in figure 7. It has two possible solutions: 19 Solution 1: Shunt L and Series C Shunt L3: jBP = j(-1.4) = −π ππΏππ −π (2π10∗109 )πΏ3 (0.02) L3 = 0.568nH Series C3: jXS = j(-0.94) = −π ππΆππ −π (2π10∗109 )πΆ3 (50) C3 = 7.96pF The second solution is discussed in appendix B. 20 Solution 1 Figure 7: MGA Input Lumped Elements 21 Similarly, the output matching network is designed by moving from the center of the smith chart toward the load reflection coefficient on the smith chart as shown in figure 8. It has four possible solutions where we have selected solution 1 as follows: Solution 1: Series C and Shunt L Series C4: jXS = j(-0.42) = −π ππΆππ −π (2π10∗109 )πΆ4 (50) C4 = 6.3pF Shunt L4: jBP = j(-1.0) = −π ππΏππ −π (2π10∗109 )πΏ4 (0.02) L4 = 0.796nH Other three solutions are discussed in appendix B. 22 Solution 1 Figure 8: MGA Output Lumped Elements 23 The overall circuit design for maximum gain amplifier is designed with the help of ADS software. With the values of the input and output matching networks calculated before, the circuit is run with the help of the ADS software to calculate the overall gain of the maximum gain amplifier design and also the noise figure of the circuit. The unilateral gain calculation shows that the gain of the maximum gain amplifier design is calculated as 14.16dB. When the graph is plotted with the help of the ADS software, a power gain of 14.37dB is achieved. Similarly, the overall noise figure of the maximum gain amplifier design is also plotted with the help of ADS. 24 CHAPTER 6: TWO STAGE AMPLIFIER DESIGN 6.1 Overall Noise Figure of Two Sage Amplifiers “Noise is passed into a microwave component or system, either from external source or is generated within the unit itself” [4]. The design consists of two stage network connected in cascade where each adds noise to the system, thus degrading the overall signal-to-noise ratio. If the noise figure of each stage is known, the overall noise figure can be determined. The noise figure for the two stage amplifier design is given by: FCAS = F1 + πΉ2 −1 πΊπ΄1 Where F1 = Noise Figure of first stage F2 = Noise Figure of second stage GA1 = Gain of the first stage The noise figure of first stage is the minimum noise figure of the transistor. In this case, F1 = Fmin = 0.32 dB = 1.076 (ratio) GA1 = 13 dB = 19.95 (ratio) F2= Fmin + Where N= N= 4 ππ π Η1+π€πππ‘Η 2 Ηπ€π −π€πππ‘Η Η2 1−Ηπ€π Η2 Η0.554−0.38 Η2 1−Η0.554Η2 = 0.0436 From the data sheet [appendix A] we have rn = 0.11 F2 = 1.076 + 4 (5.5)(0.0436) (1+0.38)2 = 1.186 25 The noise figure of the cascaded network is FCAS = 1.076 + 1.186−1 19.95 FCAS = 1.1853 (ratio) = 0.738 dB Thus, the two stage amplifier design yields a power gain of 28.3dB and the overall noise of 0.738dB at 10 GHz. The VSWR of the two stage amplifier design is also improved. 6.2 Complete Amplifier Schematic (RF and DC) “It is essential that the amplifier’s bias circuitry be connected to the RF circuit in such a way that it will; create minimum interaction and leakage for the RF/microwave signals. To successfully achieve such a task, we use several schemes which can be briefly stated as follows: 1.) Connect an RF choke (RFC), between the DC source and RF/MW circuitry that is actually an inductor that allows low frequency or DC to pass through, but blocks all high frequency signals such as RF signals. 2.) Connect a high impedance quarter-wave transformer between the DC source and the RF circuitry. The characteristic impedance of the transformer should be high enough to create a high impedance path for travelling RF signals. 3.) Connect high value capacitors as loads to short the residual RF/MW signals that might leak into the DC circuitry. These high value capacitors create an open circuit at the input end of the RF circuit” [4]. Combination of all these schemes will guarantee a high degree of isolation. The complete amplifier schematic with RF and DC is shown in figure 9. 26 Figure 9: Complete Amplifier Schematic (RF and DC) 27 CHAPTER 7: SIMULATION With the help of ‘RF and Microwave E-book’ software provided by Dr. Matthew Radmanesh, I was able to perform some baseline solutions, which helped to verify the values calculated manually. The screenshot of the results have been provided. Figure 10, checks for the stability of the transistor NE3210S01 which has been selected for this design. Figure 10: RFMW Design Essential Stability Result 28 The transistor selected for the design, NE 3210S01, is a low noise FET. Agilent technologies have collaborations with NEC, so this particular transistor is found in the Agilent library. The device characteristics are now found out which are shown in figure 11. Figure 11: S-Parameter Simulation of NE3210S01 29 The S-parameters are simulated and the following results are obtained. The values are found to be exactly the same as provided in the data sheet. Figure 12: S-Parameter Simulation Result Figure 13: Stability Table 30 The graph for stability factor for the transistor NE 3210S01 is shown in figure 14. Figure 14: Simulation Result for Stability and mag (delta) 31 The S- parameter plot for the transistor NE 3210S01 is shown in figure 15. Figure 15: S-parameter Plot 32 The VSWR graph for the transistor NE 3210S01 is shown in figure 16. Figure 16: VSWR of the Transistor 33 The noise figure graph for the transistor NE 3210S01 is shown in figure 17. Figure 17: Noise Figure of the Transistor 34 With the help of the RFMW essential tool the baseline solution for the minimum noise amplifier stage is calculated. Before the actual circuit is designed, this tool helps to generate a workable solution to create a base design. Once results are generated, later ADS software is used to build the circuit design and the results are then simulated. The snapshots of the MNA design calculations are shown as follows: Figure 18: Minimum Noise Amplifier RFMW 35 Figure 19 : Amplifier Specification Figure 20: Parameter Check 36 Figure 21: MNA Input Matching Network 37 Figure 22: MNA Output Matching Network 38 Now the ADS software is used to design the first stage which is the minimum noise amplifier circuit with the base solution obtained with the RFMW tool. The overall circuit is shown in figure 23. Figure 23: Minimum Noise Amplifier (MNA) Design 39 The lumped elements for input and output matching network are simulated with the help of the smith chart tool available in the ADS software. The results are shown as follows: Figure 24: MNA Input matching Solution 1 with ADS 40 Figure 25: MNA Input Matching Solution 2 with ADS 41 Figure 26: MNA Output Matching Solution1 with ADS 42 Figure 27: MNA Output Matching Solution 2 with ADS 43 The powergain graph for the minimum noise amplifier stage is shown in figure 28. Figure 28: Power Gain of MNA 44 The Noise figure (NFMIN) of the minimum noise amplifier stage is shown in figure 29. Figure 29: Noise Figure of MNA 45 The plot for the overall noise of the minimum noise amplifier stage is shown in figure 30. Figure30: Overall Noise of MNA 46 Similar to the minimum noise amplifier stage, the RFMW essential tool is used to calculate the baseline solution for the maximum gain amplifier stage. Figure 31: Maximum Gain Amplifier Main Page RFMW Essential Figure 32: MGA Amplifier Specification 47 Figure 33: Unilateral Gain Calculations Figure 34: MGA Input Matching Network with RFMW Essentials 48 Figure 35: MGA Output Matching Network with RFMW Essentials 49 The design for the second stage, which is the Maximum Gain amplifier, is designed with ADS software. The input and output matching elements, the gain of MGA, noise figure and the overall noise for MGA design are simulated and the results are displayed. Figure 36: Maximum Gain Amplifier (MGA) Design 50 The ADS smith chart tool is used to verify the values of the lumped elements calculated in chapter 5 and the verified results are displayed below for the input and output matching networks for maximum gain amplifier stage. The results are shown as follows: Figure 37: MGA Input Matching With ADS 51 Figure 38: MGA Output Matching with ADS 52 The results of maximum gain amplifier stage are plotted with ADS. The power gain of the MGA design is shown in figure 39. Figure 39: Power Gain of MGA 53 The overall noise of maximum gain amplifier stage is shown in figure 40. Figure 40: Overall Noise of MGA 54 The minimum noise figure (NFmin) of maximum gain amplifier stage is shown in figure 41. Figure 41: Noise Figure of MGA 55 The VSWR of maximum gain amplifier stage is shown in figure 42. Figure 42: VSWR of MGA 56 The two stage amplifier design with minimum noise amplifier as the first stage and maximum gain amplifier as the second stage is designed with ADS and the transistor is already biased at VDS = 2V and IDS = 10mA. Figure 41 shows the schematic of two stage design. Figure 43: Two Stage Amplifier Design with ADS 57 Figure 44 shows the impedances for M1, M2, M3 and M4 blocks for the two stage design. Figure 44: Impedances for M1, M2, M3, M4 Blocks 58 The plot for the overall power gain of two stage amplifier design is shown in figure 45. Figure 45: Power Gain of Two Stage Design 59 The S-parameter plot for the two stage amplifier design is shown in figure 46. Figure 46: S-parameter of Two Stage Design 60 The noise figure plot of two stage amplifier design is shown in figure 47. The overall noise of the two stage design is 0.814dB. The specifications for the two stage design have been met. Figure 47: Noise of Two Stage Design 61 The plot for the VSWR of two stage amplifier design is shown in figure 48. Figure 48: VSWR of Two Stage Design 62 CHAPTER 8: CONCLUSION The design of the two stage amplifier has been shown to successfully meet the performance criteria. The numerical design and the simulation of this project are shown in table-1. The numerical calculations and simulated results are comparable. Parameter Design Goals Numerical Simulated Results Calculation ADS RFMW Book Gain 29dB ±1dB 28dB 28.348dB 28.4dB Noise ≤1dB 0.738dB 0.814dB 0.8dB ADS refers to Agilent’s ‘Advanced Design System’ software RFMW Book refers to ‘RF and Microwave Book’ software [4] Table 1: Comparison of Numerical values and Simulated Values The transistor was initially checked for stability and was found out to be unconditionally stable. The two stage design using active bias networks (which is modeled in ADS) has been designed and simulated. The first stage (MNA) is based on NE321S01 transistor. It was designed, simulated and tuned for the best possible gain and noise figure. From the results displayed, it is evident that a gain of 13 dB and a noise figure of 0.669dB can be achieved. In order to get a better power gain for the designed MNA, a second stage MGA based on the same transistor is added in cascade after the first stage. This maximum gain amplifier (MGA) design provides a gain of 14.205dB. The design has been adjusted using optimization tools applied to matching networks such that the final design is improved in both gain and noise figure. The final two-stage amplifier design shows a peak power gain of 28.3 dB and an excellent noise figure of 0.814 dB. This meets our design requirements. Also, ADS software provided an accurate method for circuit design and simulations. 63 Overall, working on this project has helped me to understand amplifier design concepts at microwave frequencies as well as the overall design process at the industrial level. 64 REFERENCE [1] http://wps.prenhall.com/chet_paynter_introduct_6/0,5779,426159-,00.html [2] http://www.globalspec.com/reference/75707/203279/2-6-narrowband-matchingnetworks, 2001. [3] Matthew M. Radmanesh, ‘Electronic Waves and Transmission Line Circuit Design’, Bloomington, Indiana, AuthorHouse, 2011 [4] Matthew M. Radmanesh, ‘RF & Microwave Design Essentials: Engineering Design and Analysis from DC to Microwaves’, Bloomington, Indiana, Authorhouse,2007 [5] Matthew M. Radmanesh, ‘Advanced RF & Microwave Circuit Design: The Ultimate Guide to Superior Design’, Bloomington, Indiana, AuthorHouse, 2009 [6] http://www.engr.uky.edu/~gedney/courses/ee523/ADSTutorials.html, May 2009. [7] http://www.uio.no/studier/emner/matnat/ifi/INF5481/h11/undervisningsmateriale/ ADS.pdf, 2009. [8] http://search.datasheetcatalog.net/key/3210S01, 2014. [9] Singla, Shrey. “Design of Three Stage Low noise Microwave Amplifier at 10 GHz”, California State University, Northridge; http://hdl.handle.net/10211.2/2621 65 Appendix A DATA SHEET 66 67 68 69 70 71 72 73 74 75 76 77 78 79 Appendix B Lumped Element Possible Solutions Minimum Noise Amplifier Stage (Stage 1): a) Input Matching Network Solutions: When calculating the input lumped elements from smith chart, four possible solutions are possible. The solution selected for this design is series C and shunt L (solution 1). The other three solutions are discussed below. Solution 2: Shunt C and Series L πππΆ Shunt C5: jBP = j(0.67) = ππ π(2π10∗109 )πΆ5 (0.02) C5= 0.213pF Series L5: jXS = j(1.08) = πππΏ ππ π(2π10∗109 )πΏ5 (50) L5 = 0.859nH Solution 3: Series C and Shunt C Series C6: jXS = j(-3.03) = −π ππΆππ −π (2π10∗109 )πΆ6 (50) 80 C6 = 0.105pF Shunt C7: jBP = j(2.13) = πππΆ ππ π(2π10∗109 )πΆ7 (0.02) C7= 0.68pF Solution 4: Shunt C and Series C Shunt C8: jBP = j(0.66) = πππΆ ππ π(2π10∗109 )πΆ8 (0.02) C8 = 0.211pF Series C9: jXS = j(-0.146) = −π ππΆππ −π (2π10∗109 )πΆ9 (50) C9 = 2.18pF The input lumped element values are calculated manually from the smith chart and are shown in figure 49. 81 Solution 4 Solution 3 Solution 1 Solution 2 Figure 49: Minimum Noise Amplifier Input Elements Solutions 82 b) Output Matching Network Solutions: Similarly when calculating the output lumped elements from the smith chart, two solutions are possible. For this design, shunt C and series L (solution 1) is selected. The other solution for output lumped elements is as follows: Solution 2: Series C and Shunt L Series C10: jXS = j(-0.13) = −π ππΆππ −π (2π10∗109 )πΆ10 (50) C10 = 0.49pF Shunt L6: jBP = j(-0.6) = −π ππΏππ −π (2π10∗109 )πΏ6 (0.02) L6 = 1.32nH The output lumped element values are calculated manually from the smith chart and are shown in figure 50. 83 Solution 1 Solution 2 Figure 50: Minimum Noise Amplifier Output Elements Solutions 84 Maximum Gain Amplifier Stage (stage 2): a) Input Matching Network Solutions For input lumped elements, two solutions are possible. Shunt L and Series C (solution 1) is chosen for the maximum gain input lumped element design. The other solution is discussed below. Solution 2: Shunt C and Series L Shunt C11: jBP = j(0.04) = πππΆ ππ π(2π10∗109 )πΆ11 (0.02) C11= 0.013pF Series L7: jXS = j(1.3) = πππΏ ππ π(2π10∗109 )πΏ7 (50) L7 = 1.035nH The input lumped element values are calculated manually from the smith chart and are shown in figure 51. 85 Solution 1 Solution 2 Figure 51: Maximum Gain Amplifier Input Elements Solutions 86 b) Output Matching Network Solutions: For output lumped element design, four possible solutions are possible. The solution used for this design is series C and shunt L (solution 1). The other three solutions are discussed below. Solution 2: Shunt C and Series L πππΆ Shunt C12: jBP = j(0.24) = ππ π(2π10∗109 )πΆ12 (0.02) C12= 0.076pF Series L8: jXS = j(0.6) = πππΏ ππ π(2π10∗109 )πΏ8 (50) L8 = 0.477nH Solution 3: Series C and Shunt C Series C13: jXS = j(-0.26) = −π ππΆππ −π (2π10∗109 )πΆ13 (50) C13 = 1.22pF Shunt C14: jBP = j(0.35) = πππΆ ππ π(2π10∗109 )πΆ14 (0.02) 87 C14= 0.11pF Solution4: Shunt C and Series C Shunt C15: jBP = j(0.1) = πππΆ ππ π(2π10∗109 )πΆ15 (0.02) C15 = 0.031pF Series C16: jXS = j(-0.4) = −π ππΆππ −π (2π10∗109 )πΆ16 (50) C16 = 0.796pF The output lumped element values are calculated manually from the smith chart and are shown in figure 52. 88 Solution 4 Solution 3 Solution 1 Solution 2 Figure 52: Maximum Gain Amplifier Output Elements Solutions 89 Appendix C S2P Data file Used NEC Compound Semiconductor Devices Ltd. 16. July 2002 NE3210S01 N-channel HJ-FET Vds = 2V Id = 10mA GHz S MA R 50 f S11 S21 S12 GHz MAG ANG MAG ANG MAG ANG (Deg) (Deg) (Deg) 2.00 0.973 -21.2 4.450 154.2 0.022 75.9 2.50 0.951 -27.7 4.453 147.1 0.028 71.2 3.00 0.935 -34.3 4.439 140.3 0.033 66.7 3.50 0.914 -40.6 4.389 133.5 0.038 63.5 4.00 0.893 -46.3 4.314 127.3 0.042 57.7 4.50 0.872 -51.4 4.230 121.1 0.045 54.5 5.00 0.848 -55.9 4.158 115.3 0.048 49.7 5.50 0.829 -60.0 4.118 109.9 0.050 48.2 6.00 0.814 -64.8 4.130 104.3 0.053 46.1 6.50 0.781 -70.1 4.149 98.3 0.058 42.8 7.00 0.745 -76.3 4.180 91.8 0.063 40.4 7.50 0.699 -82.7 4.170 85.3 0.065 36.6 8.00 0.660 -90.3 4.184 78.7 0.070 33.7 8.50 0.635 -99.8 4.197 71.7 0.074 29.4 9.00 0.602 -109.5 4.171 64.7 0.077 25.4 9.50 0.578 -118.3 4.109 57.9 0.081 22.3 10.00 0.554 -127.2 4.063 51.3 0.086 18.9 10.50 0.537 -135.2 4.030 44.6 0.092 15.3 11.00 0.507 -144.1 3.978 37.6 0.095 10.8 11.50 0.477 -154.0 3.950 30.8 0.099 5.9 12.00 0.445 -166.2 3.906 23.5 0.103 2.1 12.50 0.428 -179.6 3.851 16.0 0.108 -2.2 13.00 0.418 165.3 3.762 8.5 0.110 -6.6 13.50 0.430 150.6 3.642 1.1 0.111 -10.3 14.00 0.453 137.9 3.517 -6.1 0.110 -14.8 14.50 0.486 126.7 3.395 -13.0 0.112 -19.6 15.00 0.513 116.7 3.259 -19.9 0.111 -22.0 15.50 0.526 108.4 3.150 -26.4 0.113 -25.6 16.00 0.531 100.4 3.046 -33.3 0.110 -29.3 16.50 0.539 91.1 2.911 -40.7 0.112 -32.1 17.00 0.533 82.1 2.739 -48.0 0.111 -36.1 17.50 0.537 72.2 2.573 -54.3 0.110 -40.1 18.00 0.546 64.7 2.400 -59.4 0.106 -41.6 90 S22 MAG 0.550 0.538 0.523 0.511 0.500 0.495 0.492 0.484 0.482 0.472 0.450 0.423 0.393 0.360 0.327 0.290 0.268 0.251 0.233 0.224 0.211 0.187 0.157 0.123 0.110 0.125 0.161 0.207 0.255 0.299 0.329 0.343 0.347 ANG (Deg) -15.2 -19.9 -25.2 -30.3 -34.9 -39.1 -42.9 -45.8 -48.8 -52.6 -56.3 -59.2 -62.6 -67.3 -72.4 -78.8 -86.8 -96.2 -105.3 -114.3 -123.1 -132.5 -146.2 -164.0 169.0 141.4 121.7 113.4 109.0 105.4 101.5 95.9 90.6 f GHz 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 Fmin dB 0.25 0.26 0.28 0.30 0.32 0.34 0.42 0.56 0.72 Gammaopt MAG ANG (Deg) 0.940 12.0 0.800 26.0 0.660 44.0 0.500 68.0 0.380 97.0 0.290 133.0 0.270 177.0 0.330 -129.0 0.390 -82.0 91 Rn/50 0.38 0.33 0.26 0.18 0.11 0.09 0.08 0.11 0.23