Digital implementation of some standard filters outlined in IEEE standard 743-1984 for telecommunication system testing

Digital implementation of several most commonly used filters in telecommunications was done on an Intel 8088 based microcomputer. These filters include various cascade combinations of 1010 Hz notch, C-message weighting, 3 kHz flat, low frequency protection and intermodulation distortion. Design of these filters was based on 12 bit input. Sampling frequency is 20 kHz. Specifications outlined in the testing standard, IEEE 743 - 1984 were met and a high repetition rate can be achieved (1.1 second was required for the cascaded combination of C-notch and low frequency protection filter). Several techniques were developed. These techniques include a finite length algorithm in computations, transient cancellation to eliminate the ringing transient response and automatic gain control for auto-ranging.