RFIC Design and Testing for Wireless Communications A PragaTI (TI India Technical University) Course July 18, 21, 22, 2008 Lecture 1: Introduction Vishwani D. Agrawal Foster Dai Auburn University, Dept. of ECE, Auburn, AL 36849, USA 1 Abstract This course discusses design and testing of RF integrated circuits (RFIC). It is suitable for engineers who plan work on RFIC but did not have training in that area, those who work on IC design and wish to sharpen their understanding of modern RFIC design and test methods, and engineering managers. It is an abbreviated version of a onesemester university course. Specific topics include semiconductor technologies for RF circuits used in a wireless communications system; basic characteristics of RF devices – linearity, noise figure, gain; RF front-end design – LNA, mixer; frequency synthesizer design – phase locked loop (PLL), voltage controlled oscillator (VCO); concepts of analog, mixed signal and RF testing and built-in self-test; distortion – theory, measurements, test; noise – theory, measurements, test; RFIC SOCs and their testing. 2 Objectives To acquire introductory knowledge about integrated circuits (IC) used in radio frequency (RF) communications systems. To learn basic concept of design of RFIC. To learn basic concepts of RFIC testing. 3 Outline Introduction to VLSI devices used in RF communications ■ SOC and SIP ■ Functional components ■ Technologies Design concepts and selected case studies Test concepts ■ Basic RF measurements ■ Distortion characteristics ■ Noise ■ SOC testing and built-in self-test (BIST) 4 References 1. M. L. Bushnell and V. D. Agrawal, Essentials of Electronic Testing for Digital, Memory & Mixed-Signal VLSI Circuits, Boston: Springer, 2000. 2. J. Kelly and M. Engelhardt, Advanced Production Testing of RF, SoC, and SiP Devices, Boston: Artech House, 2007. 3. B. Razavi, RF Microelectronics, Upper Saddle River, New Jersey: Prentice Hall PTR, 1998. 4. J. Rogers, C. Plett and F. Dai, Integrated Circuit Design for High-Speed Frequency Synthesis, Boston: Artech House, 2006. 5. K. B. Schaub and J. Kelly, Production Testing of RF and System-on-a-Chip Devices for Wireless Communications, Boston: Artech House, 2004. 5 Schedule, July 18, 2008 09:00AM – 10:30AM Lecture 1 10:30AM – 11:00AM Break 11:00AM – 12:30PM Lecture 2 12:30PM – 01:30PM Lunch 01:30PM – 03:00PM Lecture 3 03:00PM – 03:30PM Break 03:30PM – 05:00PM Lecture 4 Introduction Agrawal Power & Gain Agrawal Distortion Agrawal Noise Agrawal 6 Schedule, July 21, 2008 09:00AM – 10:30AM Lecture 5 10:30AM – 11:00AM Break 11:00AM – 12:30PM Lecture 6 12:30PM – 01:30PM Lunch 01:30PM – 03:00PM Lecture 7 03:00PM – 03:30PM Break 03:30PM – 05:00PM Lecture 8 RF Design I Dai RF Design II Dai RF Design III Dai RF Design IV Dai 7 Schedule, July 22, 2008 09:00AM – 10:30AM Lecture 9 10:30AM – 11:00AM Break 11:00AM – 12:30PM Lecture 10 12:30PM – 01:30PM Lunch 01:30PM – 03:00PM Lecture 11 03:00PM – 03:30PM Break 03:30PM – 05:00PM Lecture 12 RF Design V Dai RF Design VI Dai ATE & SOC Test Agrawal BIST Dai 8 An RF Communications System Superheterodyne Transceiver 0° VGA LNA Phase Splitter LO Duplexer 90° ADC LO DAC 0° PA VGA Phase Splitter LO 90° Digital Signal Processor (DSP) ADC DAC RF IF BASEBAND 9 An Alternative RF Communications System Zero-IF (ZIF) Transceiver 0° LNA Phase Splitter LO Duplexer 90° ADC DAC 0° Phase Splitter PA LO 90° Digital Signal Processor (DSP) ADC DAC RF BASEBAND 10 Components of an RF System Radio frequency ● Duplexer ● LNA: Low noise amplifier ● PA: Power amplifier ● RF mixer ● Local oscillator ● Filter Intermediate frequency Mixed-signal ● ADC: Analog to digital converter ● DAC: Digital to analog converter Digital ● Digital signal processor (DSP) ● VGA: Variable gain amplifier ● Modulator ● Demodulator ● Filter 11 Duplexer TDD: Time-Division Duplexing FDD: FrequencyDivision Duplexing ● Same Tx and Rx frequency ● RF switch (PIN or GaAs FET) ● Less than 1dB loss Rx ● Tx to Rx coupling (-50dB) ● More loss (3dB) than TDD ● Adjacent channel leakage fr ft Rx fr Tx TDD command Tx ft 12 LNA: Low Noise Amplifier Amplifies received RF signal Typical characteristics: ● Noise figure ● IP3 ● Gain ● Input and output impedance ● Reverse isolation ● Stability factor 2dB – 10dBm 15dB 50Ω 20dB >1 Technologies: ● Bipolar ● CMOS Reference: Razavi, Chapter 6. 13 PA: Power Amplifier Feeds RF signal to antenna for transmission Typical characteristics: ● Output power ● Efficiency ● IMD ● Supply voltage ● Gain ● Output harmonics ● Power control ● Stability factor +20 to +30 dBm 30% to 60% – 30dBc 3.8 to 5.8 V 20 to 30 dB – 50 to – 70 dBc On-off or 1-dB steps >1 Technologies: ● GaAs ● SiGe Reference: Razavi, Chapter 9. 14 Mixer or Frequency (Up/Down) Converter Translates frequency by subtracting local oscillator (LO) frequency Typical characteristics: ● Noise figure ● IP3 ● Gain ● Input impedance ● Port to port isolation 12dB +5dBm 10dB 50Ω 10-20dB Tecnologies: ● Bipolar ● MOS Reference: Razavi, Chapter 6. 15 Passive Mixer nFET V(RF) V(IF) RL V(LO) 16 Active Mixer VDD V(IF) V(LO) V(RF) 17 LO: Local Oscillators Provide signal to mixer for down conversion or upconversion. Implementations: ● Tuned feedback amplifier ● Ring oscillator ● Phase-locked loop (PLL) ● Direct digital synthesizer (DDS) 18 Phase Splitter Splits input signal into two same frequency outputs that differ in phase by 90 degrees. Used for image rejection. C R Vout_1 Vin Vout_2 R C 19 SOC: System-on-a-Chip All components of a system are implemented on the same VLSI chip. Requires same technology (usually CMOS) used for all components. Components not implemented on present-day SOC: ● Antenna ● Power amplifier (PA) 20 SIP: System-in- Package Several chips or SOC are included in a package. Routing within SIP may be provided via a semiconductor substrate. RF communications system may contain: ■ SIP, containing ● SOC consisting of CMOS digital and mixed-signal components (DSP, ADC, DAC) CMOS LNA and mixers CMOS DDS Filters ■ Power amplifier (PA) ■ Antenna 21 Dimensions of RF Design Communication theory Microwave theory Random signals Signal propagation RF Design Wireless standards Transceiver architecture IC design CAD tools 22 RF Design Hexagon Noise Power Frequency Linearity Supply voltage Gain 23 Technologies GaAs: ■ High frequency ■ High power ■ Used in PA and front-end switches ■ Low yield, expensive to manufacture ■ Not integrated on silicon chips Silicon bipolar and BiCMOS Silicon CMOS, suitable for tens of GHz SiGe ■ Possible replacement for GaAs ■ Can be integrated on silicon chips 24 Problem to Solve Analyze the function of phase splitting for image rejection in the following circuit: LPF 90o sin ωLOt RF + cos ωLOt IF LPF 25