GB889899A - Microwave impedance-discriminating devices - Google Patents

Abstract

889,899. Impedance measurement. MULLARD Ltd. Dec. 9, 1960, No. 42565/60. Class 37. A micro-wave impedance discriminator for comparing an impedance to be tested with a known impedance element comprises means to apply identical signals to both impedances, junctions dividing signals reflected from both into two equal parts, first and second comparison devices for comparing each half of each reflected signal comprising hybrid junction and square law detectors, and means provided between second junction and second comparison device whereby the output signals have amplitudes proportional to the reflection coefficients and the amplitude and phase difference is a function of the difference between the angles of the reflection coefficients. A circuit of such a discriminator is shown in Fig. 1 in which an input terminal 8 is connected via a two-way power-splitter 180-degree hybrid junction F to a similar junction G having opposite arms terminated in a non-reflecting impedance and to a junction E having one terminal connected to a non-reflecting impedance and the other to an impedance TP to be tested. The remaining terminals of E and G are connected to junctions D and C, respectively, the output terminals of which are connected to both of two junctions A and B, each being connected to square law rectifiers R. The voltages so produced are applied to the X and Y plates of a cathode-ray oscillograph, as shown in Fig. 2, to produce a display in the form of a spot displaced from the centre point by a distance r and at an angle #. Specification 818,018 is referred to.