A frequency converting circuit including: an impedance network having a first pair of terminals and operable to provide a first signal in a frequency band centered at a first frequency f1; an output network having second and third pairs of terminals and configured to pass, between the second and third pairs of terminals, a second signal in a frequency band centered at a second frequency f2 different from f1; a pump circuit having a fourth pair of terminals and operative to provide, at the fourth pair of terminals, a third signal at a pump frequency fp, where fp?f1 and f2; and a frequency converter having a first port connected to the first terminals, a second port connected to the second terminals and a third port connected to the fourth terminals, the frequency converter being operative to cause the difference between f1 and f2 to be equal to fp.