An apparatus for modifying a radio frequency signal includes a mixer core,
an input circuit and an interface circuit. The mixer core receives a first
signal having a first frequency and a second signal having a second
frequency, and outputs a third signal which is a function of the first and
second signals. The input circuit sets a predetermined bias current,
receives a radio frequency (RF) signal and inputs the RF signal into the
mixer core. The interface circuit is interposed between the mixer core and
the input circuit. The interface circuit receives the bias current and
input it to the mixer core. In one embodiment, the input circuit includes
a transistor and the interface circuit includes a transformer.
