Frequency synchronising circuit for raster oscillator - compares its output with that of pulse shaper whose gain is controlled by lock-in circuit to increase amplitude only during hunt

摘要

The frequency synchronising circuit, for a raster oscillator, uses a pulse shaper to distort a fundamental frequency and to form a spectrum of harmonics. This is compared with the frequency of the tunable oscillator requiring locking. The output of the tunable oscillator is compared in a phase discriminator with the pulse shaper output. - The result is amplified, rectified and low pass filtered and applied to the tunable oscillator's control input via a frequency setting circuit. The gain of the pulse shaper is controlled in time with the frequency sweep by a lock-in circuit responding to the output of the LP filter. The gain is regulated so that the amplitude of the pulses at the pulse shaper output is only increased during the hunt process.