Monolithic double balanced microstrip mixer with flat conversion loss

A double balanced mixer circuit for a monolithic microwave integrated circuit, comprising:

• a diode ring modulator;
• a first balun coupled to said diode ring modulator for supplying radio frequency signals to said mixer circuit;
• a second balun coupled to said diode ring modulator for supplying a signal generated locally to said mixer circuit;
• two outputs leading from said diode ring modulator each providing an intermediate frequency signal;
• a first pair of circuits each comprising passive microstrip means for providing a relatively broadband radio frequency short circuit over an intermediate frequency signal band, said first circuits being coupled between said first balun and said diode ring modulator;
• and
• a second pair of circuits each comprising passive microstrip means for providing a relatively broadband radio frequency open circuit over said intermediate frequency signal band, said second circuits being coupled between said second balun and said diode ring modulator.

A double balanced mixer circuit comprising:

• a diode ring modulator;
• a first balun having a first impedance coupled to said diode ring modulator for supplying radio frequency signals to said mixer circuit;
• a second balun having a second impedance coupled to said diode ring modulator for supplying a signal generated locally to said mixer circuit;
• two outputs leading from said diode ring modulator each providing an intermediate frequency signal;
• a first pair of circuits each comprising passive microstrip means for providing a relatively broadband radio frequency short circuit over an intermediate frequency band, coupled between said first balun and said diode ring modulator;
• and
• a second pair of circuits each comprising passive microstrip means for providing a relatively broadband radio frequency open circuit over said intermediate frequency band, coupled between said second balun and said diode ring modulator;
• wherein said first and second pair of circuits enable broadband frequencies to be applied to said diode ring modulator independent of the impedance of said first and second baluns.