GB1490849A - Phase shift circuits - Google Patents

Abstract

1490849 Phase shift circuits; AFC systems HEWLETT-PACKARD CO 24 Sept 1974 [23 Nov 1973] 41522/74 Headings H3R and H3A A phase shift circuit suitable for producing a large phase shift of an input signal at 12<SP>1</SP> in a network analyser (Fig. 2, not shown) comprises a phase synchronization arrangement 58, 62-74 for synchronizing the frequencies of two signals, and frequency converter stages 60, 54 for obtaining a phase shift of the input signal. The phase synchronization arrangement is of the phase lock loop type and at sync. establishes a predetermined phase shift between the signals compared in a phase detector. Synchronized oscillators 58, 66 have their outputs differ by a multiple of this phase shift by employing dividers 62, 68 in the signal paths. Up and down converters 60, 54 merely superpose this multiplied phase shift upon the input signal. The phase shift obtainable may be varied by an applied control signal at 48 and by a variable voltage source 74. The source 74 may be replaced by a control signal (not shown) resulting from a phase comparison of the input signal at 12<SP>1</SP> with another signal. In another embodiment (Fig. 3, not shown) the input signal is synchronized with the output of an oscillator in a phase locked loop and the input, oscillator signals are heterodyned after suitable frequency multiplication. The network analyser of which the phase shift circuit forms a part is the subject of invention claimed in the divisional Specification 1,490,850 (see Division G1).