K-band frequency up-converters using reduced-size couplers and dividers

A reduced-size branch-line hybrid circuit and a rat-race circuit, both of which were designed on an uniplanar approach, are successfully applied to a small size K-band balanced up-converter and an image-rejection up-converter. These two circuits utilize a combination of high-impedance transmission lines and lumped-constant capacitors. The image-rejection up-converter also employs a lumped-element balun and a lumped-element Wilkinson combiner. The use of these four circuit greatly reduced the size of the up-converter chips. The fabricated up-converter showed good performance including conversion gain of 1.7 dB and image-rejection of more than 20 dB at the K-band.<>