Cavity oscillator with undesired mode absorbing waveguides for linear FM

A cavity oscillator operable over a range of frequencies and having substantially attenuated modes higher than the mode of the fundamental resonant frequency comprising:

• a waveguide section having dimensions which determine the fundamental resonant frequency of the oscillator;
• a gain element disposed in said section to provide amplification to sustain oscillation;
• a first waveguide means contiguously coupled to said section for propagating higher order modes having an electric field maxima at the center of said section;
• a second waveguide means contiguously coupled to said section for propagating higher order modes having an electric field minima at the center of said section;
• and
• absorbing loads disposed in said first and second waveguide means to absorb propagated modes, whereby higher order modes with electric field minima and maxima at the center of said section are effectively attenuated.

A modulated elongate cavity oscillator having minimized modulation nonlinearities comprising:

• a first cavity having dimensions which determine the fundamental resonant frequency of the oscillator;
• means disposed in said first cavity for providing amplification to sustain oscillation and for modulating the fundamental frequency;
• a first waveguide means coupled to said first cavity for absorbing modes higher than the mode of said fundamental frequency which have an electric field maxima concurrent with the longitudinal center line of said first cavity;
• and
• a second waveguide means coupled to said first cavity for absorbing modes higher than the mode of said fundamental frequency which have an electric field minima concurrent with the longitudinal center line of said first cavity, said second waveguide means including a second and third waveguide contiguous to each other, and absorbing loads which terminate said second and third waveguides to absorb propagated higher order modes, said first and second waveguide means providing effective attenuation of the higher order modes such that modulation nonlinearities due to the existence of higher order modes are substantially eliminated.

A cavity oscillator operable over a range of frequencies and having substantially attenuated modes higher than the mode of the fundamental resonant frequency comprising:

• a waveguide section having dimensions which determine the fundamental resonant frequency of the oscillator;
• a gain element disposed in said section to provide amplification to sustain oscillation;
• a first waveguide means coupled to said section for propagating higher order modes having an electric field maxima at the center of said section;
• a second waveguide means coupled to said section for propagating higher order modes having an electric field minima at the center of said section, said second waveguide means comprising a second waveguide having a reflective obstruction at its center line, and second and third apertures on each side of said obstruction for propagating said higher order modes, said obstruction concurrent with said electric field minima;
• and
• absorbing loads disposed in said first and second waveguide means to absorb propagated modes, whereby higher order modes with electric field minima and maxima at the center of said section are effectively attenuated.