Method and apparatus for isolating signals in RF circuits and systems

Abstract

An apparatus for providing electrical isolation between two ports prevents a potentially interfering signal input from one port from reaching the other port. A first circuit path passes a first signal in a first direction from a first port of the two ports to a second port of the two ports. A second path inverts the potentially interfering signal attempting to pass in a second direction opposite the first direction from the second port to the first port and adds the inverted signal to the potentially interfering signal at the first port to thereby cancel any affect the potentially interfering signal might have at the first port. According to one exemplary embodiment of the apparatus, the first circuit path includes two directional couplers—a first directional coupler coupled to the first port and a second directional coupler coupled to the second port. A delay line is coupled between the first and second directional couplers to match a time needed for a signal to pass through the second path. An inverting amplifier is coupled between the first and second directional couplers to perform the necessary inversion. The inverting amplifier includes a gain having a magnitude matching a magnitude of a total gain of the first and second directional couplers but opposite in sign to the total gain of the first and second directional couplers. Impedance matching resistors are coupled to the two directional couplers.

Dependencies are inferred from the claim text.