FREQUENCY CONVERTER

PURPOSE:To hold the identity of spectram components of input and output signals of transmitting and sending mixers, and to simplify switching of a radio frequency by constituting local signal generators of the mixers, of the same local signal generator. CONSTITUTION:A frequency difference of a transmitting RF signal from a transmitting signal end 21 and a receiving RF signal impressed to as receiving signal end 22 is absorbed by a transmitting mixer 4 and a receiving mixer 9, respectively, and a frequency of a local oscillator 14 is selected to 1/N of a frequency difference of the transmitting RF signal and the receiving RF signal, so that the mixers 4, 9 retain the identity of frequency spectrum components of a transmitting second IF signal of a transmitting second signal end 19 and a receiving second IF signal of a receiving second signal end 20. Also, a change of transmitting and receiving channels is adapted by adding an increase portion of a radio frequency of transmission and reception, to a frequency of a local oscillator 17.