Limiting frequency modulation circuit - uses frequency and phase comparator circuit and oscillator output and reference voltage, frequency of latter being determined by synthesiser

摘要

The circuit generates an output voltage between two limiting frequencies. The output voltage of an oscillator (01) is compared with a reference voltage (UB) in a frequency and phase comparator (TH). The frequency (f3) of the reference voltage is determined by a synthesiser (03) which is supplied by both limiting frequencies (fa,fe), via an adjustable memory. The control voltage (U2) for the tunable oscillator is analogously generated. A change-over switch (SAI) has pref. a series-connected integrator (IN) with timing element (C,R). At the starting low output frequency (f1) of the oscillator an auxiliary voltage (U1) is applied for charging the integrator RC-element. The setting signal (U2) tunes the oscillator until the desired limiting frequency has been reached. The integrator may contain a differential amplifier, supplied with a reference voltage derived from the auxiliary voltage and forming a fraction of the same. This reference voltage may be one half of the auxiliary voltage.