FREQUENCY CONVERSION CIRCUIT

摘要

PURPOSE:To decrease number or local oscillation circuits and to simplify and miniaturize a changeover switch by generating a local oscillation signal used at that time till a local oscillation circuit not selected is selected next among plural local oscillation circuits. CONSTITUTION:A control circuit 84 throws a changeover switch 83 to a position of a local oscillator 81 for a period of a time slot of a transmission data and a local oscillation signal Lo1 is fed to a mixer 5 via a frequency multiplier 85. Then a transmission intermediate frequency signal is converted into a high frequency signal and sent to a communication line from a high frequency amplifier 7. The control circuit 84 outputs a set control signal of a succeeding local oscillation signal Lo2 of a local oscillator 82 during non selection for the transmission period. Thus, the frequency synthesizer or the like is used for a low speed oscillation circuit and the changeover switch is simplified and miniaturized.