Frequency converter used for a receiver which receives signals of a UHF band or a microwave band

摘要

@ A frequency converter which is capable of rejecting unnecessary signal generated by image signals. The frequency converter has first and second local oscillation circuits (1, 2) which generate local oscillation signals whose frequencies are the same and whose phases are different by 90 degrees from each other, has two mixer circuits (7, 8), and has a hybrid coupler (9). The mixer circuits (7, 8) generate two unnesserary signals whose phases are different by 90 degrees from each other. The hybrid coupler (9) delays one unnecessary signal by a quarter of the wavelength to generate two unnecessary signals whose phases are different by 180 degrees from each other, so that they are cancelled by each other.