| 摘要 |
<p>1478896 Frequency modulators TELEFONAKTIEBOLAGET L M ERICSSON 25 June 1974 [25 June 1973] 28208/74 Heading H3R A frequency modulator comprises a cavity resonator (Fig. 5 not shown) and a device G D e.g. a Gunn diode or avalanche diode for generating an oscillation, a voltage dependent capacitance V D coupled to the device for performing frequency modulation in response to an applied bias U 0 and a modulating voltage U m , a reactance circuit PR, e.g. a parallel tuned circuit having a transfer function, the poles of which are situated at or substantially at the harmonic frequencies of the free-running oscillator frequency, the reactance circuit PR, at one of the harmonics, being strongly electromagnetically coupled to the device G D but weakly coupled to the capacitance V D whereby the modulator non- linearity is arranged to be zero or small. The frequency deviation from the linear modulator characteristic caused by the non-linear operation of the capacitance V D is compensated by the frequency deviation of the oscillator fundamental frequency due to the variation of the oscillator operating voltage caused by the reactive circuit operating about the harmonic frequency. The reactance circuit may include a combination of series and parallel resonant circuits.</p> |
