GB1119261A - Wave form equalizers - Google Patents

Abstract

1,119,261. Automatic equalization. FUJITSU Ltd. 17 Feb., 1965 [17 Nov., 1963], No. 22031/63. Heading H4R. An automatic equalization system uses a differentiated echo type equalizer and a frequency characteristic equalizer in combination, the frequency characteristic equalizer operating of the lower frequency components of the signal. Fig. 5 shows a system for equalizing a line 4 for the transmission of television video signals from a source 1. At the transmitter a synch. separator 2 synchronizes a pilot waveform generator 3 the output of which, e.g. a square wave, is added to the transmitted signal, outside the time or frequency band of the television signal, e.g. during the frame blanking period. At the receiver the signals are applied to the echo type equalizer which includes the tapped delay line DL from the tap Ao of which the signal is applied to the frequency characteristic equalizer LE before the differentiated outputs from the other taps of the delay line are added at the input of amplifier 12. The proportions of the outputs of the various taps of the delay line which are to be added to the output from tap Ao, and the constants of the frequency characteristic equalizer are determined by the automatic adjusting system in which a synchronizing circuit 5 causes generator 7 to produce an appropriately synchronized replica of the pilot wave form added to the television signal at the transmitter. The locally generated pilot waveform is compared with the received pilot waveform in differential amplifier DA and a difference signal is produced which is sampled in circuit S at times determined by the synchronizing circuit 5 and related to the delay in the tapped delay line DL. The sampled difference signal is then fed through gates G-m to Gt2, opened at times corresponding to the time of appearance of the pilot waveform at the delay line tap with which the gate is associated, to operate adjusting motors M-m to Mt2 which adjust the attenuators K-m to Kn on the delay line taps, and the values of the components of the equalizer LE, to tend to reduce the values of the sampled difference signal to zero.