ELEN 701 RF & Microwave Systems Engineering. Lecture 4 October 11, 2006 Dr. Michael Thorburn Santa Clara University

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1 ELEN 7 RF & Microwave Systems Engineering Lecture 4 October, 26 Dr. Michael Thorburn Santa Clara University

2 Lecture 5 Receiver System Analysis and Design, Part II Key Parameters Intermodulation Characteristics Linearity of Receiver Adjacent Channel and Alternate Channel Selectivity Channel Filters and Phase Noise of Local Oscillator Single-Tone Desensitization Linearity of Receiver Interference Blocking Channel Filters and Phase Noise of Local Oscillator Dynamic Range Automatic Gain Control

3 Superheterodyne Full-Duplex Architecture Configuration Receiver Section

4 Key Characteristics of Receiver Sensitivity Noise Figure, Noise Temperature Gain Linearity Signal S Noise N Self Noise No Receiver Noise Figure F Gain G Linearity C/3IM or NPR Signal G x S Noise G x (N+No) N F + N + N N N NF *log(f)

5 System Noise Figure Total Receiver Noise Figure is Computed from Assembly of Component Gains and Noise Figures g, F g2, F2 g3, F3 g4, F4 g5, F5 g6, F6 g7, F7 Iterative Formula CF Cumulative Noise Figure CG Cumulative Gain CF CF n F CF n + ( Fn ) / CGn EXAMPLE: g, F g2, F2 NF NF Total Total log F log F 2 + g NF + NF 2 G

6 System Noise Figure Unit Gain (db) Gain Cumm G Cumm NF Cumm G NF (db) NF Cumm NF (db) (db) Cumm Pct Pct Pre-selector E E E % 48.3% LNA E E+.5.4E % 24.% RF BPF E E E %.2% RFA E E+..E % 2.% RF D/C..E E+..26E %.% IFA..E E+..26E %.% BPF E E E %.4% VGA E E E % 4.2% VGA stage 2 3..E E+6 2..E %.3% LPF -5..E E+ 5..E %.3% Computation example of Receiver Line-up for Gain and Noise Figure Inputs are in Yellow (unit characteristics) Note: For passive units the F /g (NF -G) Many columns here to illustrate example. Must remember to assemble the NF properly (i.e. Don t Mix Up ratios and dbs!) Iterative Formula CF CF Cumulative Noise Figure F CG Cumulative Gain CFn CFn + ( Fn ) / CGn

7 Cascaded Noise Figure of Un-Matched Blocks of Receiver Chain + n i i j j i n g F F CF 2 Iterative Formula for Matched Stages CF Cumulative Noise Figure g is power gain g, F g2, F2 g3, F3 g4, F4 g5, F5 g6, F6 g7, F7 Total Receiver Noise Figure is Computed from Assembly of Component Gains and Noise Figures + + n m m l l o l o l i l o l i l v m cascade t R R R R R g F F CF 2,, 2,,, 2. _ Iterative Formula for Un-Matched Stages F Overall cascaded noise figure g is voltage gain R is input/output resistance

8 Receiver Desensitization Evaluation Due to Transmitter Noise Emission in the Receiver Band Rest of Transmitter Equivalent Antenna Temperature Method Duplexer NF 2.5 db PA Isolator Receiver NF 3.5 db Antenna Port P S kt BW Duplexer degradation T T e N, Rx e, Rx F F F Rx Rx Rx Rx Port kt kt + P e, Rx ( F T T e e T T Rx, T + ( F + ( F P kt N, Tx _ Rx N, Tx _ Rx ) T Rx, Rx, LNA + F ) T Te + ( F T Rx, Rx, kt ) ) T + P Rest of Receiver kt N, Tx _ Rx + ( F Rx, ) Unit Gain (db) Gain Cumm G (db) Cumm G NF (db) NF Cumm NF Cumm NF (db) Duplexer E E E Receiver E E E

9 Receiver Desensitization Evaluation Due to Transmitter Noise Emission in the Receiver Band Equivalent Antenna Temperature Method F Rx NF PN, Tx kt Rx _ Rx + F Rx, PN, Tx log kt _ Rx + F Rx, Duplexer NF 2.5dB Receiver NF 3.5 db NF Rx 2.33 log dB EXAMPLE: Desensitization is.6 db for this example Unit Gain (db) Gain Cumm G (db) Cumm G NF (db) NF Cumm NF Cumm NF (db) Duplexer E E E Receiver E E E

10 Influence of Antenna VSWR to Receiver Noise Figure We can characterize impedance mismatch by VSWR or Return Loss Antenna Noise Temp T A T + T F Equivalent Input Noise Temp, T F Feeder Input Loss, /L F T 2 + T Rx Equivalent Input Noise Temp, T Rx Noise-free system, Gain G RX For mobile system VSWR may vary between.5 and 6 depending on how system is held and how close to the head Feeder Network Note: L F > T T A + T F (L F -) + [ T Rx / (/L F ) ] T A + T F (L F -) + [T Rx * L F ] Receiver T 2 T A / L F + T F (L F -) / L F + T Rx R g V g V N I N Receiver Noiseless generator Equivalent Noise Voltage & Current load R L

11 Influence of Antenna VSWR to Receiver Noise Figure R g Simple approximation: Antenna input resistance is much larger than input reactance. V g generator V N I N Equivalent Noise Voltage & Current Receiver Noiseless R L load F NFRx log + Ra ρ R g, o Freq (MHz) 2 + ρ ρ Rx, o Comparison of ADS Simuluation with Calculation Original Antenna Simulation Calculation Difference

12 Intermodulation Characteristics The Ratio of the fundamental signal S_ (db) to the mth-order intermodulation product S_m (db) satisfies the following equation S S m ( m )( IIP S ) m i Where S_i is the input desired signal of the system or device and IIP is the mthorder input intercept point

13 Cascaded IIP Expressions The cascaded mth order input intercept point of the n stage block is represented n k k m m IIP n IIP IIP IIP n k IIP k IIP m n k m m IIP k j j IIP P g g g P g g P g P P g g g P P g P 3, 2 3, 3,2 3, 3, 3, For the 3 rd order intermod:

14 Adjustments to IIP calculation Frequency Selective System Practically all the receiver systems have frequency selectivity and suppress interferers to a great extent. It is necessary to take the receive selectivity into account when calculating the overall input intercept point of the receiver Cascaded IIP Expressions in Voltage and Hybrid Form In the IF and analog BB blocks, input and output signals of each stage are measured based on their voltage instead of the power and the amplification level for individual stages is thus represented by voltage gain. We shall note this but defer it for purposes of this lecture

15 Calculation of Receiver Intermodulation Characteristics Allowed Degradation of the Received Desired Signal The linearity of a receiver, represented by the IIP, is the main casue of intermodulation distortion, but the intermodulation spurious response also depends on other factors. Other topics: Intermodulation Distortion Resulting from Finite Receiver Linearity Degradation Caused by Phase Noise and Spurs of Local Oscillators Degradation Resulting from Cross-Modulation

16 Single-Tone Desensitization A unique specification for CDMA mobile systems Cross-Modulation Products Determination of the Allowed Single-Tone Interferor

17 Adjacent Channel and Alternate Channel Selectivity The adjacent/alternate channel selectivity measures a receiver s ability to receive a desired signal at its assigned channel frequency in the presence of adjacent/alternative channel signal at a given frequency offset from the center frequency of the assigned channel. Desired Signal Level and Allowed Degradation Formula of Adjacent/Alternate Channel Selectivity and Blocking Characteristics Two-Tone Blocking and AM Suppression Characteristics

18 Receiver Dynamic Range and AGC System Dynamic Range of a Receiver The dynamic range of a mobile station receiver is the input signal power range at the antenna port of the receiver over which the data error rate (BER) does not exceed a specified value. The lower end of this range depends on the receiver sensitivity level The upper end of this range is determined by the allowed maximum input power at which the data error does not exceed the specified value. Automatic Gain Control To be able to operate over a wide dynamic range, a receive commonly employs an AGC system

19 Reciever System Design and Performance Evaluation Receiver System Design Basics Define design goals based on application Good electrical performance Low power consumption Low cost Small size Performance is represented mainly by Receiver sensitivity Intermodulation characteristics Adjacent and alternate channel selectivity Blocking characteristics Spurious emissions

20 Basic Requirements of Key Devices in Receiver System Filters Main Specifications of passive band-pass filters Center Frequency Pass-band Bandwidth Pass-band Insertion Loss Pass-band Ripple Group Delay Group Delay Distortion Rejection (i.e. Adjacent Channel Rejection or Rejection at other frequencies) Input Impedance Output Impedance Input Return Loss Output Return Loss

21 Basic Requirements of Key Devices in Receiver System LNA Main Specifications of LNAs Operating Frequency Band Nominal Gain Noise Figure IIP Reverse Isolation Input and Output Impedance Input and Output Return Loss Input Power Range

22 Basic Requirements of Key Devices in Receiver System Downconverter and I/Q Demodulator Main Specifications of LNAs Operating Frequency Band Nominal Gain Noise Figure IIP-M (in particular IIP-3) IIP-2 for Demod Isolation between RF/IF and LO ports Isolation between LO and IF/BB ports Isolation between RF/IF and IF/BB ports Nominal LO power Input and output impedance Input Return Loss RF power range

23 Reciever System Design and Performance Evaluation Receiver System Performance Evaluation

24 Homework (due Nov ) Expand your Spreadsheet (or Program) from last week to calculate the Noise Figure, the Signal Level and the C/3IM for the cascaded set of components comprising your receiver. Give yourself enough flexibility so that you can add components (passive or active) to your line up. Use example in text on page 297 to validate your equations For now, only consider center frequency of channel (do not try to characterize filters)

ELEN 701 RF & Microwave Systems Engineering. Lecture 2 September 27, 2006 Dr. Michael Thorburn Santa Clara University

ELEN 701 RF & Microwave Systems Engineering Lecture 2 September 27, 2006 Dr. Michael Thorburn Santa Clara University Lecture 2 Radio Architecture and Design Considerations, Part I Architecture Superheterodyne