Abstract: A radio frequency multiplexer, which supports a plurality of frequency bands, comprises a common node, a plurality of single band nodes, and a plurality of parallel branches. Each of the plurality of parallel branches is designated to one of the plurality of frequency bands and connects the common node and one of the plurality of single band nodes. A particular branch of the parallel branches may comprises a filter for a desired frequency band that passes through the particular branch, a quadrature hybrid coupler coupled to the filter, and a set of one or more other filters for one or more other frequency bands in the plurality of frequency bands respectively. The set of one or more other filters is coupled to the quadrature hybrid coupler for rejecting the one or more other frequency bands by the particular branch.

Abstract: A method for maintaining good cancelation in a passive feed-forward cancelation circuit is disclosed. The feed-forward cancelation circuit may include at least one path which may comprise a phase-shifter and a variable attenuator. This method uses the complex value of the reflection coefficient at the point where the communication device is connected to a transmission medium, such as an antenna, to determine the values for the phase shifter(s) and the variable attenuator(s).

Abstract: An all-acoustic filter includes acoustic directional couplers and acoustic filters. In one embodiment, the all-acoustic filter includes two acoustic directional couplers, pair of matched acoustic filters corresponding to either transmit or receive frequency bands, and another acoustic filter corresponding to the other of transmit or receive frequency bands. An all-acoustic duplexer may be realized monolithically in a small form factor, may be tunable, may support multiple transmit or receive frequency bands, or may include schemes for antenna mismatch correction.

Abstract: The disclosure provides circuitry and methods to determine the reflection coefficient of a transmission line connected another physical element or device such as an antenna. The outgoing and the reflected signals on the transmission line are compared using two separate paths, with one path going through a signal conditioning circuitry such as an equalizer. The two paths are then combined and detected. A lookup table may be used for non-linear responses.

Abstract: A radio frequency (RF) circuitry includes a device that taps a transmission line and picks up some of electromagnetic signals traveling in both directions. The RF circuitry includes a first detector, a second detector, a third detector, and a processor. The first detector measures a power of a first portion of the tapped electromagnetic signal travelling in one direction. The second detector measures a power of a first portion of the tapped electromagnetic signal travelling in the other direction. The third detector measures a power of a combined signal which includes a second portion of the tapped electromagnetic signal travelling in the one direction and a second portion of the tapped electromagnetic signal travelling in the other direction. The processor determines, based on outputs from the detectors, a relative magnitude and a relative phase of the electromagnetic signals.