GB1279835A - Improvements in or relating to pulse generators - Google Patents

Abstract

1279835 Automatic phase and frequency control systems SIEMENS AG 6 Oct 1969 [4 Oct 1968] 48970/69 Heading H3A A timing pulse generator comprises a controlled oscillator OS to whose control input is supplied the sum of two variables corresponding to the phase difference between the timing pulses and input pulses applied at A and to the repetition frequency of the input pulses respectively, the second variable being produced by a control unit SEG. A controller REG producing the first variable comprises control circuits ST 1 , ST 2 generating control pulses having durations corresponding to the interval between the leading edge of a timing pulse and the leading edge of an associated input pulse and to the interval between the leading edge of a timing pulse and the trailing edge of an associated input pulse respectively and an amplifier VST producing an output dependent on the difference in length of the two control signals. As shown in Fig. 2, VST comprises transistors TS10, TS11 which conduct for the duration of the control signals charging or discharging a capacitor C L depending on an increase or decrease of frequency of input pulses. The capacitor C L is followed by a low-pass filter R S , C S at whose output is applied the variable corresponding to the repetition frequency of the input pulses via a further resistor connected to terminal G, the sum of the two variables V E being applied to the oscillator OS which is an astable multi-vibrator. The control unit SEG as shown in Fig. 4 comprises a transistor TS1 conducting at the end of input pulses to charge a capacitor C 1 , transistor TS 3 connected in parallel to C 1 and driven to conduction by the input pulses to discharge C 1 and a transistor TS 2 conducting for the duration of input pulses supplied at its base, to charge a second capacitor C 2 to the voltage across C 1 , the output of a low pass filter R 2 , C 3 connected to C 2 providing the desired input repetition frequency dependent variable. In the temporary absence of input pulses to the generator, transistors TS10, TS11 (see Fig. 2) do not conduct but since capacitor C L has a short charging time constant and a long discharging time constant, timing pulses continue to be supplied at the previous frequency. To achieve proportional action instead of integral action described above, a bipolar switch Sch (Fig. 2) is provided which charges capacitor C L to a fixed potential upon the appearance of each input pulse.