A band pass filter includes a first micro-strip port for receiving a
radio-frequency signal, a second micro-strip port for outputting a
filtered radio-frequency signal and 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.