Improvements in or relating to electrical apparatus for determining the frequency response characteristic of an electrical component, circuit or system

摘要

897,505. Measuring frequency response. DE HAVILLAND AIRCRAFT CO. Jan. 30, 1961 [Oct. 28, 1959], No. 36642/59. Class 40(5). A four-phase oscillator feeds the 0 degree phase A cos #t to a component or system under test. The 0 degree and 180 degree phases are fed to a motor-driven potentiometer system 2 and the 90 degree and 270 degree phases to a similar system 3. The real and imaginary components B cos #t and C sin #t are compared with corresponding outputs X cos #t arid Y sin #t derived from the potentiometers 22 and the differences fed through phase-sensitive detectors 4, 5, comprising transistor 10, 11, switched by the appropriate oscillator phases, the outputs being fed back to the motors 24 to adjust the potentiometers 22 such that X = B and Y = C. D.C. potentiometers 23, linked to the potentiometers 22 provide outputs X, Y, indicating the properties of the component under test. A suitable four-phase oscillator is described (Fig. 7, not shown). Additional subsidiary circuits (Figs. 5 or 6, not shown) may be used when the output from the component under test includes harmonics of the test frequency.