Coherent tunable filter apparatus and wireless communication front-end circuit thereof

Abstract

A front-end circuit with coherent tunable filters is provided. The circuit includes a first filter, an amplifier, and a second filter. The amplifier is coupled to the first filter, and the second filter is coupled to the amplifier. Furthermore, the amplifier is placed between the first and second filters. The first filter has a first tunable intermediate frequency, and is used to filter a received signal. The amplifier is used to amplify the output of the first filter. The second filter has a second tunable intermediate frequency, and is used to filter the output of the amplifier. The first and second intermediate frequencies have a coherent-tuning relation with each other.