Patent ID: 8050650

Claim:
A frequency down converter for enhancing rejecting effect of image frequency, the frequency down converter comprising: a receiver end for receiving a radio-frequency signal; a mixer for transforming a frequency of a filtered radio-frequency signal to a preset frequency according to a local oscillation signal, so as to outputting an intermediate frequency signal; and a band pass filter coupled between the receiver end and the mixer, the band pass filter comprising: a first micro-strip port for receiving a radio-frequency signal; a second micro-strip port for outputting a filtered radio-frequency signal, the second micro-strip port comprising at least one resonating cavity formed for enhancing rejecting effect of image frequency corresponding to the filtered radio-frequency signal; and a plurality of resonators arranged between the first micro-strip port and the second micro-strip port for performing band pass filtering on the radio-frequency signal to generate the filtered radio-frequency signal.