Chapter 1
Software-Defined Radio Front Ends
1.1 INTRODUCTION
The ultimate dream of every software-defined radio (SDR) front-end architect is to deliver a radio-frequency (RF) transceiver that can be reconfigured into every imaginable operating mode, in order to comply with the requirements of all existing and even upcoming communication standards. These include a large range of modes for cellular (2G–2.5G–3G and further), WLAN (802.11a/b/g/n), WPAN (Bluetooth, Zigbee, etc.), broadcasting (DAB, DVB, DMB, etc.), and positioning (GPS, Galileo) functionalities. Obviously, each of them has different center frequency, channel bandwidth, noise levels, interference requirements, transmit spectral mask, and so on. As a consequence, the performances of all building blocks in the transceiver must be reconfigurable over an extremely wide range, requiring ultimate creativity from the SDR designer.
Reconfigurability is a requirement for SDR functionality, but often one forgets that it can also be an enabler for low power consumption. Indeed, once flexibility is built into a transceiver, it can be used to adapt the performance of a radio to the actual circumstances instead of those implied by the worst-case situation of the standard. Since linearity, filtering, noise, bandwidth, and so on, can be traded for power consumption in the SDR, a smart controller is able to adapt the radio at runtime to the actual performance required, and hence can reduce the average ...
