DELAY DETECTION CIRCUIT AND LOW-NOISE OSCILLATION CIRCUIT USING THE SAME

摘要

A delay detection circuit and a low-noise oscillation circuit using such a delay detection circuit. When the oscillation output of a VCO is to be supplied to two high frequency mixers, a .pi./2 phase shifter 24 in the front stage of one of the high frequency mixers gives a quadrature form. High frequency components are removed from the output voltage of the high frequency mixers by LPF. DC components are also removed from the output voltage of the high frequency mixers by HPF. The output voltages of low frequency mixers contain secondary phase noise components proportional to squared phase noise components and primary phase noise components proportional to the phase noise components and also depending on the delay time ? of a delay unit. When the output voltage of one of the low frequency mixers is subtracted from the output voltage of the other low frequency mixer, the secondary phase noise components are offset and the dependence on the delay time ? is removed from the primary phase noise components. The resulting voltage is used as a control voltage for the VCO (10). No voltage control delay unit or feedback loop for controlling it are required.