Rf modem with improved binary transversal filter

Abstract

A binary transversal filter (200) in which the delay line of flip-flops (A-L, A'-L') is driven by timing signals (CLK, CLK*, CLKD, CLKD*) that are the same clock rate as the clock rate (CLK) of the encoded binary signals (IMPULSE 0, IMPULSE 1) being introduced into the delay line forming the binary transversal filters (200). The timing signal (CLK, CLK*, CLKD, CLKD*) that time or clock the stages of the delay line (A-L, A'-L') are phases of the clock (CLK) that introduces the encoded binary signals (IMPULSE 0, IMPULSE 1) into the delay line (A-L, A'-L'). Two substantially identical binary transversal filters (200a, 200b) are used to convert two encoded binary data streams (IMPULSE 0, IMPULSE 1) into a duobinary signal. The output of the two binary transversal filters (200a, 200b) are summed (Q2) and passed to a programmable amplifier (210), the gain of which is turned on when there is data in the encoded binary signals (IMPULSE 0, IMPULSE 1) to be converted and transmitted and is turned off otherwise. The carrier is prevented from being applied to the transmission medium (218) when the last bit of data in the encoded binary signals (IMPULSE 0, IMPULSE 1) has been converted to duobinary data by a binary transversal filter (200a, 200b) and applied to the medium (218). The encoded binary signal (IMPULSE 0, IMPULSE 1) inputted to the delay line (A-L, A'-L') of each binary transversal filter (200a, 200b) is monitored (25); the data shifted out of the last delay stage (L, L') of each binary transversal filter (200a, 200b) is also monitored (26). When the monitors (25, 26) indicated (27) that both encoded binary signals (IMPULSE 0, IMPULSE 1) are a logic 1 and the binary data shifted out of the last stage of delay (L, L') in both binary transversal filters (200a, 200b ) are also both logic 1, all meaningful data has been converted to duobinary data and transmitted on the medium (218) and therefore the carrier may be turned off.