GB1341867A - Voltage-to-frequency converters - Google Patents

Abstract

1341867 Gunn oscillator circuits; frequency modulation BRITISH AIRCRAFT CORP Ltd 7 July 1972 [7 July 1971] 31918/71 Headings H3T and H3R A voltage to frequency convertor includes a pair of Gunn effect devices connected in parallel across a common bias supply, a mixer for mixing the outputs of the two Gunn devices and a tuning means responsive to an input voltage or current to vary the frequency of at least one of the Gunn devices whereby the mixer produces a difference frequency related to the magnitude of the input voltage or current. As shown the Gunn devices are biased on the same side of the hump of the frequency v bias characteristic and either the resistor R1 or R2 is adjusted until the output frequency from the mixer for zero input at A, B is zero or a required offset frequency. An input signal at A, B applies a differential shift in frequency between the two devices and a low pass filter is included in the output of the mixer to obtain the difference frequency at the output. In a modification (Fig. 2, not shown) the two Gunn devices are biased on opposite sides of the frequency v bias hump so that on input (at CD) increases the frequency of one Gunn device and decreases the frequency of the other Gunn device. In a further modification (Fig. 3, not shown) both Gunn devices are biased on the same slope of the frequency bias characteristic. The input voltage is applied to one of the devices and the other device provides a fixed reference frequency for the mixer. The tuning of the Gunn devices may be obtained by varactor diodes or YIG spheres placed in the cavities of the Gunn devices (Figs. 4 and 5, not shown).