Discrete-Time Processing of RF Signals
Signal processing in a radio-frequency (RF) receiver consists of three fundamental elements: frequency translation, filtering, and amplification. These three elements are necessary in order to precondition the RF signal so that efficient analog-to-digital conversion of the signal desired can follow . Filtering in an RF receiver, which is the main subject of this chapter, is used to cope with the large dynamic range of the input signal. The RF signal desired is sensed at the RF receiver’s antenna, along with all other electromagnetic signals that are present in the environment. Analog filters can eliminate large unwanted signals and thereby relax the dynamic-range requirements of subsequent blocks, particularly the dynamic-range requirements of an analog-to-digital converter (ADC). Alternatively, some filtering in the analog domain can be transferred to the digital domain if a suitably high-dynamic-range ADC is available.
Several factors must be considered in designing analog filters for an RF receiver. First and foremost are the traditional linear circuit design metrics: noise, power consumption, and distortion. Second, it is often desirable to have a precise, and programmable, corner or stopband frequency. Having precise control ...