Phase locked loop that includes d. c. modulation

Abstract

A D.C. modulated phase locked oscillator (220 or 264) is usable separately to provide an output that is both phase locked and D.C. modulated or is usable in a radio frequency receiver (200). The D.C. modulated phase locked oscillator (220or 264) includes a phase locking oscillator (222 or 266) and a D.C. modulator (224 or 268). Both a forward path (14) and a feedback path (16) are D.C. modulated. In one embodiment. D.C. modulation of the feedback path (16) includes using a modulation oscillator (64) and two flip-flops (228 and 164) to develop quadrature square waves, and using a quadrature phase shift keying (QPSK) mixer (234) to subtract a frequency of one of the square waves from the frequency in the feedback path (16). In another embodiment, D.C. modulation of the feedback path (16) includes a dual modulus divider (34) being interposed into the feedback path (16), frequencies from a modulation oscillator (64) being used to control a parallel adder (272), and the parallel adder (272) being used to change one of the inputs of a modulus controller (50) that includes both 'A' and 'N' inputs, and that controls the number of times that the dual modulus divider (34) divides by lower and higher dividing ratios in accordance with the 'A' and 'N' inputs, whereby D.C. modulation of the feedback path (16) is achieved by a change in one of the inputs, 'A' or 'N'.