A digital quadrature phase detector for angle modulated signals

摘要

An analog quadrature-modulated signal is converted into a digital signal by an A/D converter (1) using a sampling clock having a frequency four times higher than the carrier of the quadrature modulated signal. The digital signal is delayed by one sampling slot in each of four delay circuits (2-5) connected in series to the A/D converter. The output of the A/D converter and that of the fourth delay circuit are multiplied by -1/2 by respective digital weighting circuits (6,7), and the multiplied outputs together with the output of the second delay circuit are added together in an adder (8) to generate an I component (in-phase) signal. The output of the first delay circuit is multiplied by -1 by another weighting circuit (10) and this multiplied output and the output of the third delay circuit are added together in another adder (11) to generate a Q component (quadrature phase) signal. The I and Q signals are held in latches (9,12) clocked at one quarter of the sampling clock rate. IMAGE