Plural band converter

Abstract

A frequency converter employs a balanced bridge mixer of switching elements such as field-effect transistors (FETs) with a local oscillator supplying control signals to gate terminals of the transistors. A carrier at intermediate frequency (IF) or at radio frequency (RF) is modulated for communication of data, and is applied to alternate nodes of the bridge. The remaining bridge nodes supply output signals to respective branches of an output circuit. Each branch of the output circuit is provided with a bandpass filter having a spectral characteristic corresponding to the spectral characteristic of a specific one of plural output signals to be outputted via the branch. Each branch may contain an active element, such as an amplifier, which is activated for outputting a signal, and which is deactivated for when node signal is to be outputted. A switchable impedance circuit is included within each of the branches to present a substantially constant impedance characteristic to the bridge, independently of whether the bridge amplifier is activated or deactivated. The local oscillator may provide plural frequencies, as by use of a variable-frequency oscillator or by use of plural oscillators, to place an output signal within the frequency band of a specific one of the output branches.