GB1296548A - - Google Patents

Abstract

1296548 Testing two port networks STATNI VYZKUMNY USTAV PRO STAVBU STROJU 11 Nov 1969 [11 Nov 1968] 55147/69 Heading G1U In order to determine the transmission properties of a network 2, Fig. 4, under test, a signal A1 is applied to the network, its output signal A2 is amplitude modulated 5 on to a carrier S1, and the output signal M from the modulator is applied to a phase sensitive detector 8 receiving a reference signal S2 having a frequency equal to that of the upper sideband from the modulator 5 to produce an output signal V1 having a average D. C. level proportional to the product of the amplitude of the fundamental frequency emitted by the network and the cosine of the phase shift produced in the fundamental by the network. In the preferred embodiment shown the signal A1 applied to the network is produced by mixing 11 the outputs of two generators G, g and using the difference frequency. Also a further phase sensitive detector 15 is provided in quadrature with the first to produce a second output signal V2 proportional to the sine of the phase shift introduced by the network 2 under test. One method of operating the arrangement shown is to adjust the phase of the signal S1 from the generator G until the D.C. component of the signal V2 is zero. The phase shift in generator G necessary to achieve this is then equal to the phase shift produced in the fundamental by the network under test, and the D. C. component of the output signal V1 is then directly proportional to the amplitude of the fundamental transmitted by the network.