Subharmonic frequency converter for applications to millimetric radio waves

Microwave subharmonic frequency converter comprising:

• a diplexer filter in microstrip having one input port for a local oscillator signal with subharmonic frequency and an input or output part for an intermediate frequency signal, said filter being set up by a pass-band section and by a low pass section;
• a second low pass filter realized in microstrip connected between a point common to both said sections of the diplexer filter and a couple of frequency mixer diodes, said second low pass filter letting go through said local oscillator signal with subharmonic frequency towards the diodes and blocking the frequencies higher than said subharmonic generated by the diodes, in this way isolating said ports of the local oscillator signal and intermediate frequency signal from a radiofrequency signal going through the diodes;
• a waveguide with rectangular section which transports towards said mixer diodes the reception radiofrequency signal, or outwards said diodes the transmission radiofrequency signal respectively;
• a metallic line deposed on a dielectric plate and without metallization below in correspondence of a zone opposite to the cross rectangular section of said waveguide, the metallic line being interrupted in the center where said diodes are connected in antiparallel to the heads of the interruption and between the second low pass filter and the ground;
• a metal body including at least 2 contiguous cavities in which, a first one contains said diplexer filters and said second low pass filter, and a second one with a rectangular section goes through all the thickness of said metal body and extends to said waveguide which transports a reception radiofrequency signal towards said mixer diodes, or a vice versa, the diodes being placed along the center line of said second rectangular cavity in the sense of the shortest dimension;
• a third small cavity which extends the first cavity beyond the second cavity for lodging one extremity of said dielectric plate supporting the diodes and to enable the soldering of one end of said interrupted metallic lines to a wall of the cavity;
• a metal plate which closes completely said first and third cavities, and which closes on one side said second cavity setting up for the latter one a short-circuit plate.