GB628866A - Improvements in or relating to circuit arrangements for producing a measuring or control voltage varying with the instantaneous phase relation between two voltage wave forms - Google Patents

Abstract

628,866. Frequency and phase-difference measurements. PHILIPS LAMPS, Ltd. April 11, 1947, No. 9690. Convention date, Sept. 2, 1944. [Class 37] [Also in Group XL (c)] In a mixing circuit oscillations are applied to the grid of a valve and are modulated by a train of short pulses applied to the anode, which is so biassed that conduction occurs only during the pulsing period. The combination frequencies formed between the oscillations and the harmonic series into which the pulse train resolves include a term due to the harmonic nearest in frequency to the oscillations, and this is selected by means of a low-pass filter 11, 12 cutting off at half the fundamental frequency of the pulse train. According to the Specification as open to inspection under Sect. 91 the arrangement may be used for frequency measurement, the oscillations applied to the grid comprising the unknown frequency and the output from the low-pass filter being measured by known means, such as comparison with a low-frequency oscillator. It may also be used for measuring the relative phase of oscillations where frequency coincides with one of the harmonics of the pulse train by measurement of the D.C. voltage produced across the condenser 12. A modification of the arrangement (Fig. 1, Cancelled, not shown) may also be employed for generating a continuous range of frequencies (see Group XL (c)). This subject-matter does not appear in the Specification as accepted.