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RF system design

VIEWS: 9 PAGES: 27

  • pg 1
									         RF system design

    • Test environment of radio system specs
    - Receiver analysis
    - Transmitter analysis
    • Distribution of specs over Rx blocks
    • Summary



1                  RF Microelectronics         A. Thanachayanont
Test environment of system specs
    Frequency bands /filtering
    Reference sensitivity /NF
    Blocking requirements /1dB point and DR
    Intermodulation requirements / IP3, IP2 and
    LO phase noise
    Image rejection
    Transmitted power
    Out-of channel emission /filtering and LO
    phase noise
    Spurious tones
2                    RF Microelectronics   A. Thanachayanont
Reference sensitivity




3             RF Microelectronics   A. Thanachayanont
BER vs. SNR in demodulator




4           RF Microelectronics   A. Thanachayanont
CDMA receiver




5          RF Microelectronics   A. Thanachayanont
Blocking requirements
    Desensitization
    Dynamic range
    Reciprocal mixing and LO phase noise
    Band and channel filtering




6                   RF Microelectronics    A. Thanachayanont
Desensitization




7            RF Microelectronics   A. Thanachayanont
1dB compression point and DR




8           RF Microelectronics   A. Thanachayanont
Reciprocal mixing and LO phase noise




9              RF Microelectronics   A. Thanachayanont
Blocking requirements




10           RF Microelectronics   A. Thanachayanont
Intermodulation requirements




11           RF Microelectronics   A. Thanachayanont
Intermodulation requirements




12           RF Microelectronics   A. Thanachayanont
IP3 and IP2 requirements




13           RF Microelectronics   A. Thanachayanont
IP3 and IP2 requirements




14           RF Microelectronics   A. Thanachayanont
Image rejection in Rx
     Homodyne (zero-IF) overcomes problems of heterodyne (esp. image
     problem) but suffers from DC-offset, 1/f noise, LO leakage, self-mixing,
     even order distortions and IQ mismatch. For WCDMA systems DC band
     close to 0 can be sacrificed
     Low-IF overcomes DC-offset and 1/f noise but suffers from close-image
     problem and even order distortions. Image-reject mixer must be used like
     in zero-IF, but here the IQ requirements are much tougher. BPF at IF
     must be used (requires 2x more poles/zeros than LPF). For narrow-band
     systems better than zero-IF.




15                              RF Microelectronics               A. Thanachayanont
Required image rejection




16           RF Microelectronics   A. Thanachayanont
Channel filter and ADC




17           RF Microelectronics   A. Thanachayanont
Channel filter and ADC




18           RF Microelectronics   A. Thanachayanont
ADC and front-end gain




19          RF Microelectronics   A. Thanachayanont
Noise floor




20            RF Microelectronics   A. Thanachayanont
Spurious-free dynamic range (SFDR)




21            RF Microelectronics   A. Thanachayanont
Transmitter requirements
     Max power and emission mask
       noise
       spur tones
     Modulation quality
       SNR
       constellations and EVM/ BER




22                    RF Microelectronics   A. Thanachayanont
Phase noise (PN)




23          RF Microelectronics   A. Thanachayanont
Emission mask and PN




24          RF Microelectronics   A. Thanachayanont
Distribution of specs over Rx blocks




25             RF Microelectronics   A. Thanachayanont
Distribution of specs




26            RF Microelectronics   A. Thanachayanont
Summary
     First order specs can be retrieved from system
     requirements
     Simulation models needed for verification
     In case of integrated TRx’s the blocking and
     intermodulation requirements are more stringent
     than for Rx /leakage, substrate coupling, and
     radiation of Tx power/ Digital part even more noisy
     Distribution of specs depended on the available RF
     blocks and architecture, many constraints, little
     degree of freedom usually

27                      RF Microelectronics      A. Thanachayanont

								
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