Aspects of this disclosure relate to a hybrid acoustic LC filter cascaded with a non-acoustic LC filter. The hybrid acoustic filter can filter a radio frequency signal. The hybrid acoustic LC filter can include acoustic resonators, an inductor, and a capacitor. The inductor and capacitor can be external to an acoustic resonator die. The non-acoustic LC filter includes an LC circuit. Related multiplexers, wireless communication devices, and methods are disclosed.

In at least one embodiment of the invention, a method for reducing a dynamic range of a received radio frequency signal includes receiving digital IQ signals corresponding to an in-phase component of the received radio frequency signal and a quadrature component of the received radio frequency signal. The method includes demodulating the digital IQ signals to generate an instantaneous frequency signal. The method includes selecting a center frequency of a selectable filter according to whether an interfering signal is detected in a target frequency band of the received radio frequency signal. The center frequency is selected from a predetermined frequency and an estimated center frequency determined using the instantaneous frequency signal. The method includes filtering the digital IQ signals using the selectable filter configured using the center frequency to generate output digital IQ signals.

Apparatuses, methods, and systems of a hybrid node are disclosed. One embodiment of the hybrid node includes a first sector and a second sector. The first sector is operative to transmit a signal through a predetermined transmission channel at each of a first plurality of transmit beam forming settings. The second sector is operative to receive the signal through the predetermined channel at a second plurality of receive beam forming settings for each of more than one of the first plurality of transmit beam forming settings. Further, the node is operative to measure a received signal quality of the received signal at each of the second plurality of receive beam forming settings of the second plurality of antenna elements, for each of the more than one of the first plurality of transmit beam forming settings of the first plurality of antenna elements.

Mechanisms for interferer detection can detect interferers by detecting elevated signal amplitudes in one or more of a plurality of bins (or bands) in a frequency range between a maximum frequency (f.sub.MAX) and a minimum frequency (f.sub.MIN). To perform rapid interferer detection, the mechanisms downconvert an input signal x(t) with a local oscillator (LO) to a complex baseband signal xI(t)+jxQ(t). xI(t) and xQ(t) are then multiplied by m unique pseudorandom noise (PN) sequences (e.g., Gold sequences) gm(t) to produce m branch signals for I and m branch signals for Q. The branch signals are then low pass filtered, converted from analog to digital form, and pairwise combined by a pairwise complex combiner. Finally, a support recovery function is used to identify interferers.

An interference wave signal frequency is highly accurate and the interference wave signal is surely removed. A controller of an interference wave signal remover detects the interference wave signal based on a frequency scanning result by an entire-range frequency scanner, and sets a notch filter to attenuate the interference wave signal frequency. A local scan frequency band BWf.sub.L of a local frequency scanner is set by having the interference wave signal frequency as its central frequency, and local scan frequencies BIN.sub.L are set so that frequency bands overlap with each other between adjacent frequency BIN.sub.A. The local frequency scanner frequency-scans input signals to the notch filter. The controller calculates a frequency error δf of the interference wave signal frequency from the local frequency scanner, corrects the interference wave signal frequency which is from the entire-range frequency scanner by the frequency error δf, and updates the setting of the notch filter.

A high performance switch module to filter a radio frequency signal and to selectively connect to an output includes a filter unit and a plurality of switches. The filter unit has a filter configured to connect to the radio frequency signal and having a plurality of parallel output ports. The plurality of switches is connected between the plurality of parallel output ports and the output, the plurality of switches configured to connect to a control input to selectively connect an output port of the plurality of parallel output ports to the output and to selectively connect a remainder of the plurality of parallel output ports to a connection providing a substantially full reflection to the remainder of the plurality of parallel output ports of the filter unit.

Disclosed herein are methods and systems for identifying and reducing LTE-system coverage holes due to external interference. One embodiment takes the form of a process that includes receiving a signal in a first wireless band. The received signal comprises a signal of interest. The process also includes determining that a received signal quality of the signal of interest is less than a signal-quality threshold. The process also includes determining that the received signal quality of the signal of interest is less than the signal-quality threshold due to interference external to the first wireless band, and responsively attenuating the received signal. The process also includes demodulating the attenuated received signal to obtain the signal of interest.

In accordance with an embodiment, an RF system includes a transmit path having a first tunable transmit band stop filter, and a power amplifier coupled to an output of the first tunable transmit band stop filter, where the first tunable transmit band stop filter is configured reject a receive frequency and pass a transmit frequency; a receive path comprising an LNA; and a duplex filter having a transmit path port coupled to an output of the power amplifier, a receive path port coupled to an input of the LNA, and an antenna port, where the duplex filter is configured to pass the transmit frequency and reject the receive frequency between the antenna port and the transmit path port, pass the receive frequency and reject the transmit frequency between the antenna port and the receive path port.

Disclosed is a frequency selective limiter with a switched multiplexer filter bank having a plurality of filters coupled between antenna and receiver ports, wherein the switched multiplexer filter bank is configured to enable and disable selected ones of the plurality of filters in response to control signals. First detector circuitry is coupled to the antenna port and configured to detect signal voltage at the antenna port and generate a first detector voltage. Second detector circuitry is coupled to the receiver port and configured to detect signal voltage at the receiver port and generate a second detector voltage, and a digital controller is coupled between the first detector circuitry, the second detector circuitry, and a control interface, wherein the digital controller is configured to limit interfering signals by sending control signals to the switched multiplexer filter bank in response to the first detector voltage and the second detector voltage.

A multiplexer device includes at least one acoustic band pass filter connected to a common port, and a hybrid LC/acoustic filter connected to the common port in parallel with the at least one acoustic band pass filter. Each acoustic band pass filter has a corresponding passband and includes multiple acoustic resonators. The hybrid LC/acoustic filter includes at least one acoustic resonator, and has at least one capacitor replaced by a corresponding at least one acoustic resonator, respectively. Each of the at least one acoustic resonator included in the hybrid LC/acoustic filter provides a stopband response when operating in a corresponding acoustic frequency range, and acts as a capacitor when operating in a corresponding non-acoustic frequency range.