RFIC Design ELEN 351 Lecture 2: RFIC Architectures

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1 RFIC Design ELEN 351 Lecture 2: RFIC Architectures Instructor: Dr. Allen Sweet Copy right 2003 ELEN 351 1

2 RFIC Architectures Modulation Choices Receiver Architectures Transmitter Architectures VCOs, Phase Locked Loops Transceiver Architectures Copy right 2003 ELEN 351 2

3 Modulation Choices are Judged by the Following Criteria: BER (Bit Error Rate) = Error bits/total bits per unit time Spectral Efficiency (Compare to Shannon) Power Efficiency (Relates to Battery Life) Copy right 2003 ELEN 351 3

4 Example of a Simple FM Transceiver Architecture Copy right 2003 ELEN 351 4

5 Digital FSK Modulation Copy right 2003 ELEN 351 5

6 FSK Non Coherent Detector Digital Processing Copy right 2003 ELEN 351 6

7 FSK Performance Summary BER is very good for moderate signal levels, but degrades rapidly for low signals. Spectral Efficiency is poor: BW = (W2-W1) +fm, where fm is the modulation rate (1/Tb) Power efficiency is excellent because FSK constant envelope modulation tolerates a high efficiency nonlinear PA. Copy right 2003 ELEN 351 7

8 Digital Phase Modulation: BPSK Copy right 2003 ELEN 351 8

9 BPSK Signal Constellation 2 1 Copy right 2003 ELEN 351 9

10 A BPSK Modulator Copy right 2003 ELEN

11 Quadrature Phase Modulation Types QPSK OQPSK PI/4-QPSK Copy right 2003 ELEN

12 QPSK Modulator Symbol rate is ½ the Bit rate, conserving Spectrum Copy right 2003 ELEN

13 QPSK Signal Constellation These phase Transitions Have Zero Crossings Copy right 2003 ELEN

14 A Non Linear PAs will cause Spectral Regrowth with QPSK Copy right 2003 ELEN

15 Spectral Regrowth is related to odd order Intermodulation Copy right 2003 ELEN

16 Two Tone Intermodulation Intercept Point Copy right 2003 ELEN

17 An Alternate Way of Describing QPSK Modulation Copy right 2003 ELEN

18 QPSK Performance Summary BER is excellent even at low signal levels (similar to BPSK). Spectral width is ½ that of BPSK for the same data rate. Power efficiency is fair: To prevent introducing noise into adjacent channels, QPSK requires a very linear PA because of its two 180 degree phase transitions which pass through zero Amplitude. Copy right 2003 ELEN

19 OQPSK Modulator Copy right 2003 ELEN

20 Signal Constellation with OQPSK Modulation Maximum phase Transition is 90 Degrees, no zero Crossings. Copy right 2003 ELEN

21 OQPSK Performance Summary Ber is excellent even at low signal levels(similar to QPSK) Spectral width is about the same as QPSK Power efficiency is fair-good: Since there are no zero crossings in its phase transitions, OQPSK works with a less linear PA than does QPSK, raising the Power Efficiency. Copy right 2003 ELEN

22 PI/4 QPSK Signal Constellation 8 Phase states Greatest phase Transition is 135 degrees Copy right 2003 ELEN

23 PI/4-QPSK Performance Created by phase shifting 2 QPSK signals by 45 degrees. PI/4-QPSK can support differential encoding. Ber is similar to QPSK Spectral width is ½ that of QPSK for the same data rate. Power efficiency is mid way between QPSK and OQPSK, because of 135 degree phase transitions have no zero crossings. Copy right 2003 ELEN

24 Transceiver Architecture for Full Duplex Operation FDMA or CDMA Systems Copy right 2003 ELEN

25 Duplexer filter Characteristics Copy right 2003 ELEN

26 Duplexer Leakage can Desensitize the Receiver Copy right 2003 ELEN

27 Transceiver Architecture for Time Division Duplex TDMA or PTT Systems only Copy right 2003 ELEN

28 Receiver Architectures Receiver Architectures are determined by their susceptibility to interferers. Most Receivers have about 90 db gain from Antenna to Detector. Interferers and electrical noise limit S/N. Many Solutions Trade off Sensitivity, Selectivity, Size, and Cost. Copy right 2003 ELEN

29 APPCAD Spreadsheet Calculations of 1.9 GHz Receiver Copy right 2003 ELEN

30 Band Pass Filter Tradeoffs Copy right 2003 ELEN

31 Out of Band Interferers can Intermodulate in the Receiver s Front End Copy right 2003 ELEN

32 Block Diagram of a Heterodyne Receiver Copy right 2003 ELEN

33 The Image Problem Copy right 2003 ELEN

34 A BPF Between the LNA and the Mixer can Minimize the Image Copy right 2003 ELEN

35 Component Lineup for a Complete Heterodyne Receiver Copy right 2003 ELEN

36 Receiver Filter Tradeoff Copy right 2003 ELEN

37 Dual Conversion Beats the Filter Tradeoff Copy right 2003 ELEN

38 NxM Spurs can self Generate Interferers in the Mixers:A Sound Frequency Plan is the Key Copy right 2003 ELEN

39 APPCAD NxM Spur Calculation Warn of problem Frequencies Copy right 2003 ELEN

40 Quadrature Detection in the Final Analog Stage of the Receiver Copy right 2003 ELEN

41 The Direct Conversion Receiver Copy right 2003 ELEN

42 The Advantages of a Direct Conversion Receiver Zero IF, no image, no image filters. Channel select filters become low loss LPFs Very few parts, everything is on chip Compact, low cost Copy right 2003 ELEN

43 Disadvantages of Direct Conversion DC offsets for various reasons, will drive the amplifiers to the rail LO leakage to the antenna (1/f) noise is strong near zero frequency I/Q mismatches Copy right 2003 ELEN

44 LO Leakage causes DC Offsets, and LO Radiation Copy right 2003 ELEN

45 Strong Interferers Cause DC Offsets Copy right 2003 ELEN

46 DC Blocking Capacitors are a Solution to DC Offset Problems Note: DC blocking Caps are Large and must be off chip. They Remove zero frequency energy from The pulse, and degrade S/N. Copy right 2003 ELEN

47 I/Q Mismatch Problems Copy right 2003 ELEN

48 Transmitter Architectures Transmitter Architecture is determined by the Avoidance of spurious signal creation. Also, high DC to RF conversion efficiency is a top priority. The Transmitter is the Primary Power Drain on the System s Battery. Its Power Efficiency and Low power Sleep Mode Capability determines battery life. Copy right 2003 ELEN

49 Direct Conversion Transmitter: VCO Injection Pulling Problems Copy right 2003 ELEN

50 The Solution is to up Convert the Transmitter s Frequency The VCO operates at a frequency W, The transmitter s output is at (W+W2) So Pulling cannot occur Copy right 2003 ELEN

51 LO Sources use a Phase Locked Loop Architecture Copy right 2003 ELEN

52 Antenna Diversity Switching Reduces Multipath Effects Copy right 2003 ELEN

53 RFIC Partitioning Criteria Technology Analog/Digital DC Voltage To Achieve High Isolation between Sections of the System Copy right 2003 ELEN

Session 3. CMOS RF IC Design Principles

Session 3. CMOS RF IC Design Principles Session 3 CMOS RF IC Design Principles Session Delivered by: D. Varun 1 Session Topics Standards RF wireless communications Multi standard RF transceivers RF front end architectures Frequency down conversion