14-06-2013, 12:19 PM
Receiver & Transmitter Architectures
Receiver & Transmitter.pdf (Size: 506.8 KB / Downloads: 32)
Signal processing in front-end
• Filtering
• Up/down conversion
• Effect of nonlinearities
– Interferers and blockers in Rx
– Images in Rx
– Spurious emission in Tx
Filtering in front-end
• In most cases BP (or LP) filters needed
• Bandwidth of RF system determined by filters
• Unwanted signals must be suppressed (interferers, images)
• Selectivity of BPF is of big concern /but high Q tough to obtain
• BW = f0/Q so for given Q, BW~ f0
• Filter of same Q more effective at lower frequency (e.g. at IF or BB)
than at RF (in Rx only partial suppression at RF)
• Ultimate filtering in Rx always at low frequency
Transmitter issues
• Frequency accuracy and stability (phase noise)
• Ability to change f0 rapidly
• Spectral purity
- low spurious tones
- low noise emission
• Power and power efficiency
• Modulation fidelity
Conclusions
• Variety of transceiver architectures exist
• Individual design solutions represent different
trade-off in performance
• Quadrature modulation and conversion preferred
• DSP support is crucial for modern architectures
• Design of a receiver part more critical than of a
transmitter, however band corruption by a
transmitter maybe a problem