Patent GB-1141009-A (GB)
Title: Improvements in or relating to electric pulse-controlled shift registers and frequency filters
IPC: H03H11/26
Filed: 1966-12-13
Abstract: 1,141,009. Shift registers. SIEMENS A.G. 13 Dec., 1966 [14 Dec., 1965], No. 55664/66. Heading G4C. A shift register comprises a pair of line wires bridged by a plurality of shunt capacitors, adjacent capacitors being periodically connected by shift pulse trains controlling switches in one of the line wires to permit such energy exchanges to occur between adjacent capacitors that pulses of any polarity and amplitude can be shifted simultaneously in both directions along the line wires, the shift pulse trains being independent of the energy exchanges. In the shift register of Fig. 2, input data pulses at e1 are stepped along the chain of capacitors C by two interleaved trains of shift pulses, Pa, Pb, each with the same prf as the data pulse train, controlling the switches S. During transfer of charge from one capacitor to the next, all the charge is transferred (in fact the charges on the two capacitors are interchanged). This is achieved by the series insertion of an inductor before each switch, the switch being closed for one half-cycle of the resonant frequency resulting (Fig. 3, not shown), or as shown in Fig. 4 for two capacitors CO1, C02 of the shift register. In Fig. 4, each capacitor CO1, CO2 has two further capacitors, e.g. C11, C21 in shunt, and an amplifying transistor, e.g. T11, to eliminate losses. In Fig. 4, only negative potentials must occur at the upper terminals of CO1 and C02. This can be accomplished by biasing the input, the input pulses being of opposite polarities alternately. The data pulse train input at el in Fig. 2 may be amplitude modulated by a sinusoid of lower frequency (e.g. a quarter), and may be derived by sampling a sinusoid. In the latter case, the original sinusoid may be reconstituted by a low-pass filter at the register output. The same inputs may be used below. The capacitors in Fig. 2 may be equal in value. Alternatively, a frequency filter is obtained by having the capacitances of C1, C2 ... C10 in the ratio 3:9:9:1:1:1:1:9:9:3. The output of the shift register of Fig. 2 can be terminated by a shunt resistor and a second shift register, forming a stub, can be connected at an intermediate position to the first register (Fig. 9, not shown), thus again forming a filter. Fig. 5 shows a frequency filter, constituting a stub, the switches Sa, Sb being closed alternately, each at twice the rate of the input pulse frequency to be recognized. When input pulses with this frequency are applied at Ee, each pulse results in C1 being charged, its charge being transferred to C2 where it is inverted and then transferred back to C1 to cancel the next input pulse. Fig. 7 (not shown) shows a modification in which switch Sb joins the junction of La and Sa to the lower horizontal line, and Lb is eliminated. Fig. 6 (not shown) differs from this in interchanging Sa and La. In this latter modification, the remaining inductor La may be eliminated by giving C1 and C2 shunt arrangements as in Fig. 4 (Fig. 8, not shown). In the frequency filters, the prf of the shift pulses may be adjustable to alter the natural frequency of the filter. The input data signals may come from a plurality of sources, time-division-multiplexed. Integrated circuits may be used.