DIGITAL SIGNAL PROCESSING

                                                   DIGITAL  SIGNAL  PROCESSING     

  The introduction of practical and economical digital processing to M T I radar allowed a significant increase in the option open to the signal processing designer. The convenience of digital processing means that multiple delay-line cancelers with tailored frequency-response characteristics can be readily achieved.A digital M T I processor does not, in principle, do any better than a well-designed analog canceler; but it is more dependable, it requires less adjustments and attention,and can do some tasks easier.Most of the advantages of a digital M T I processor are due to its use of digital delay lines,rather than analog delay lines which are characterized by variation due to temperature, critical gains, and poor on-line availability.A simple block diagram of a digital M T I processor,from the output of the I F amplifier the signal is split into two channels.One is denoted I, for in-phase-channel.To the other is denoted Q for quadrature channel,since a 90 degree phase change is introduced into the coho reference signal at the phase detector. This causes the output of the two detectors to be 90 degree out of phase.The purpose of the quadrature channel is to eliminate the effects of blind phases, as will be described later. It is desirable to eliminate blind phases in any M T I processor, but it is seldom done with analog delay-line cancelers because of the complex of the added analog delay lines of the second channel.

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