Circuit for linearizing frequency modulated oscillators on microstrip

Apparatus for linearizing the modulation circuit in a frequency modulated oscillator, comprising:

• a microstrip oscillator having a frequency determining resonator circuit and an output matching circuit;
• a secondary resonator made up of a microstrip transmission line, having first and second ends, and having a length that is approximately equal to one quarter wavelength;
• a source of DC bias voltage having first and second terminals, said second terminal being connected to the second end of said secondary resonator;
• a source of modulting signals having first and second terminals, said second terminal being connected to ground;
• a varactor diode having one terminal end thereof connected to the first terminal of said DC bias voltage and modulating signal sources, and having the other terminal end connected to said first end of said resonator;
• a first variable capacitor having one side connected to said first end of said secondary resonator, having the other side connected to said frequency determining resonator circuit, whereby the deviation sensitivity of said oscillator is controlled;
• and
• a variable reactor having one side connected to the second end of said secondary resonator, whereby the impedance of the combination of said secondary resonator and said variable reactor may be varied to linearize said frequency modulated oscillator.