Multiple frequency generator for quadrature amplitude modulated communications

A carrier signal generator comprising:

• a quadrature voltage controlled oscillator coupled in a phase locked loop wherein an output of the oscillator is coupled through at least one quadrature frequency divider to a phase comparator responsive to a reference signal input to control a frequency of the oscillator;
• a quadrature mixer having inputs coupled to the phase locked loop on opposite sides of the quadrature frequency divider, such that two frequency inputs are applied to the quadrature mixer, the quadrature mixer including at least two stages respectively coupled to corresponding quadrature components of said two frequency inputs, and wherein outputs of the two stages are added, the quadrature mixer providing a differential output signal at a third frequency at a difference between the two frequency inputs;
• and
• a polyphase filter coupled to the differential output signal producing two quadrature outputs at the third frequency.

A method for generating carrier signals for multiplex communications, comprising:

• providing a quadrature phase locked loop responsive to a reference frequency signal, wherein the phase locked loop comprises cascaded frequency dividers in a signal path, the frequency dividers providing signals at a plurality of integer multiples of a basic frequency;
• generating at least one signal at an integer multiple of the basic frequency, by mixing at least two of said signals provided by the frequency dividers to provide a differential signal at a difference frequency of said two of said signals;
• and
• producing, by a polyphase filter, from the differential signal a quadrature signal at the third frequency, the quadrature signal having at least two outputs separated in phase by 90 degrees.