Frequency conversion apparatus

摘要

A frequency conversion apparatus has a high-frequency amplifier for amplifying an input high-frequency signal, a mixer for mixing the output signal of the high-frequency amplifier with a local oscillation signal, a filter for restricting the band of the output signal of the mixer to permit passage of only components within a predetermined band, and a variable filter provided between the high-frequency amplifier and the mixer and having a controllable cut-off frequency. With this configuration, it is possible to reduce back talk at low cost without inviting variation of input return loss characteristics.