Analog means of shaping the frequency response characteristics of digital filter [and Doppler tracking application]

One of the important advantages of the digital filter is that its frequency response characteristics can be altered by changing the coefficients of the polynomials of the transfer function. In real time environment it is often desired to tune the hardware realized filter, continuously for several applications. This necessitates changing all the coefficient values simultaneously from one analog source such that a small change in the analog control function changes all coefficients to a new set of values. We propose an EPROM based technique for adjusting the frequency response characteristics of a digital filter controlled from a single analog source. This type of control has several fields of applications. As a typical application, a Doppler tracking system employing this technique is illustrated.