ZERO Order Adaptive Equalizer
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
A device is described which adapts certain data modulator-demodulator characteristics to the characteristics of the telephone line in use, and dynamically varies modem characteristics during call, to track telephone line changes. Adaptive equalization of modem signals is a well-known art. Normally, adaptive equalizers are configured as a finite-impulse-response (FIR) filter with a multiplicity of taps. The coefficient of each tap is continually updated based on output level. FIR adaptive equalizers are powerful, but require substantial processing. A typical FIR equalizer for a DPSK modem requires at least 30 taps, and requires about three math operations per sample time per tap. Thus the computational requirement is 180 math operations per sample time.