A multiplexer includes first, second, and third filters. The first filter has a first pass band including a first band to send a signal. The second filter has a second pass band including a second band to send a signal. The third filter has a third pass band including a third band. An unwanted frequency of a second-order or fourth-order distortion mode, generated when a first transmitted signal of the first band and a second transmitted signal of the second band are simultaneously transmitted, is included in at least one of the first, second, and third pass bands. An unwanted frequency of a third-order distortion mode, generated when the first transmitted signal and the second transmitted signal are simultaneously transmitted, is included in at least one of the first, second, and third pass bands. The first filter is a BAW filter. The second filter is a SAW filter.

A switch-less transceiver has parallel LC resonances that act as OFF switches and series LC resonances act as ON switches when resonating at the transmit (TX) or receive (RX) frequency. When the transmitter is disabled, no current flows through series LC filters. Instead, series impedances to ground provide an RF ground to the transmitter output node. A TX inductor between the transmitter output node and the antenna is in parallel with a TX blocking capacitor to ground, which together form a parallel resonance to ground that has a high impedance when resonating at the receiver frequency. This high impedance acts as an OFF switch to block antenna signals from entering the transmitter. The two paths are in parallel, presenting a high impedance to the antenna and forming an OFF switch when the receiver is disabled.

The present application relates to a wave limiting circuit, and a pre-calibration method, a dynamic correction method and apparatuses therefor. The circuit comprises: an LC series resonance circuit, a controller and a matching element, wherein a first end of the matching element is connected to a radio frequency circuit; a second end thereof is connected to an antenna, and a third end thereof is connected to one end of the LC series resonance circuit; and the other end of the LC series resonance circuit is connected to the controller so as to adjust parameters of the LC series resonance circuit by means of the controller.

Filters include a housing having an input port and an output port and a plurality of resonant cavities within the housing. Each resonant cavity may include a respective notch resonator. The filter may further include a bandpass filter that includes a plurality of bandpass resonators, the bandpass filter extending between the input port and the output port. The bandpass filter may replace a transmission line that is included in conventional filters.

In a receiver that demodulates a received signal, deterioration of signal quality is suppressed. A current output unit generates and outputs, from a voltage signal, a current signal including a predetermined offset current in a low-frequency component between a high-frequency component having a frequency higher than a predetermined frequency and the low-frequency component having a frequency lower than the predetermined frequency. A demodulation unit demodulates the high-frequency component. A filter circuit passes, in the current signal, the high-frequency component from a current output unit to the demodulation unit, and causes the low-frequency component to flow from the current output unit to a predetermined reference potential point.

A technology is described for direction finding. An example of the technology can include executing stages of an N stage search for a direction finding estimate of a plane wave X. The stages of the N stage search include searching a search space in a calibration set having a plurality of points in space and calculating a direction finding estimate, wherein a first search space is a coarse set of points in space and subsequent search spaces selected for subsequent stages of the N stage search are increasingly finer sets of points in the space, and a solution for the direction finding estimate output by a stage of the N stage search is used to select a next search space for a next stage of the N stage search. A direction finding estimate output by a final stage of the N stage search is the final direction finding estimate.

In a receiver that demodulates a received signal, deterioration of signal quality is suppressed. A current output unit generates and outputs, from a voltage signal, a current signal including a predetermined offset current in a low-frequency component between a high-frequency component having a frequency higher than a predetermined frequency and the low-frequency component having a frequency lower than the predetermined frequency. A demodulation unit demodulates the high-frequency component. A filter circuit passes, in the current signal, the high-frequency component from a current output unit to the demodulation unit, and causes the low-frequency component to flow from the current output unit to a predetermined reference potential point.

A front-end module (FEM) is disclosed that includes an integrous signal combiner. The integrous signal combiner can process received signals and use a set of resonant circuits to filter signal noise prior to recombination of a plurality of signal bands that form an aggregate carrier signal. These resonant circuits may be placed after a set of low noise amplifiers and can be used to more efficiently reduce noise and parasitic loading within each of a set of signal paths. Each resonant circuit may be configured to filter noise relating to a bandwidth for a signal that is to be combined with the signal of the signal path that includes the resonant circuit. In some implementations, the integrous signal combiner can be a tunable integrous signal combiner with resonant circuits that may be reconfigurable or dynamically configurable.

Various embodiments relate to a method for calibration of a center frequency of a BPF in an FSK transceiver, the method including the steps of filtering a carrier frequency signal by the BPF to produce a filtered signal, detecting, by a phase-frequency detector (PFD), a difference in phase between the carrier frequency signal and the filtered signal from the BPF, sweeping a calibration code of the BPF, detecting a transition in the sign of the phase difference and capturing a calibration code associated with the transition in the sign of the phase difference for calibration of the BPF.

A radio frequency module includes a first receive circuit that processes a receive signal in the first frequency band. The first receive circuit includes a first substrate, a first low noise amplifier, and a first filter circuit. The first low noise amplifier is mounted on a principal surface of the first substrate. The first filter circuit is connected to an output end of the first low noise amplifier. At least a portion of the first filter circuit is provided on the principal surface of the first substrate. The first filter circuit attenuates spurious components occurring due to a transmit signal in the first frequency band received by the first low noise amplifier. The spurious components are included in the transmit signal in the first frequency band and have a frequency bandwidth that overlaps, includes, or is included in the frequency bandwidth of the receive signal in the second frequency band.