Two interconnected oscillators having adjustable coupling for controlling frequency

An apparatus comprising:

• a first oscillator comprised of an input port and an output port, wherein the first oscillator produces at its output port a first signal;
• a second oscillator comprised of an input port and an output port, wherein the second oscillator produces at its output port a second signal which is about ninety degrees out of phase with the first signal;
• a first coupling module comprised of an input port, an output port, and a control input port;
• a second coupling module comprised of an input port an output port, and a control input port;
• wherein the input port of the first oscillator is connected to the output port of the first coupling module and the output port of the first oscillator is connected to the input port of the second coupling module;
• wherein the input port of the second oscillator is connected to the output port of the second coupling module and the output port of the second oscillator is connected to the input port of the first coupling module;
• further comprised of a frequency control circuit which is connected to the control input ports of the first and second coupling modules;
• and wherein the frequency control circuit varies the coupling of the first coupling module and the second coupling module and thereby varies the frequency of the first signal and the second signal.