  Analog signal processing (ASP) is presented as a systematic approach to
address future challenges in high speed and high frequency microwave
applications. The general concept of ASP is explained with the help of examples
emphasizing basic ASP effects, such as time spreading and compression, chirping
and frequency discrimination. Phasers, which represent the core of ASP systems,
are explained to be elements exhibiting a frequency-dependent group delay
response, and hence a nonlinear phase response versus frequency, and various
phaser technologies are discussed and compared. Real-time Fourier
transformation (RTFT) is derived as one of the most fundamental ASP operations.
Upon this basis, the specifications of a phaser resolution, absolute bandwidth
and magnitude balance are established, and techniques are proposed to enhance
phasers for higher ASP performance. Novel closed-form synthesis techniques,
applicable to all-pass transmission-type cascaded Csection phasers, all-pass
reflection-type coupled resonator phasers and band-pass cross-coupled resonator
phasers are described. Several applications using these phasers are presented,
including a tunable pulse delay system, a spectrum sniffer and a realtime
spectrum analyzer (RTSA). Finally, future challenges and opportunities are
discussed.
