A wireless communication device is described. The wireless communication device includes a processor, a memory in communication with the processor and instructions stored in the memory. The instructions are executable by the processor to detect a signal degradation indication for a radio frequency (RF) signal. The instructions are also executable by the processor to cause a switch to select a combination of a first matching network and a second matching network coupled to an antenna in response to detecting the signal degradation indication.

A noise suppressor includes a first differential-mode transmission module, a second differential-mode transmission module and a common-mode absorption module. The first and second differential-mode transmission modules are configured to receive a differential signal at one of the first and second differential-mode transmission modules, and output the differential signal at the other of the same. The common-mode absorption module is electrically connected to a reference node, and is configured to absorb common-mode noise of the differential signal from at least one of the first differential-mode transmission module or the second differential-mode transmission module.

A wireless communication device is described. The wireless communication device includes a processor, a memory in communication with the processor and instructions stored in the memory. The instructions are executable by the processor to detect a signal degradation indication for a radio frequency (RF) signal. The instructions are also executable by the processor to cause a switch to select a combination of a first matching network and a second matching network coupled to an antenna in response to detecting the signal degradation indication.

A low pass filter includes a first via-hole conductor connected to a first end portion of a first inductor and a third end portion of a second inductor and extending to another side in a lamination direction with respect to a second end portion of the first inductor and a fourth end portion of the second inductor, and a first capacitor electrically connected in parallel with at least a portion of the first inductor and a portion of the second inductor and defined by a first capacitor conductor layer. The low pass filter allows the interval between attenuation poles to be easily adjusted.

An RF amplifier includes a harmonic filter with a plurality of shunt filter legs. The harmonic filter provides a suppressing frequency range for a harmonic frequency of a carrier frequency in a range of carrier frequencies. Each of the shunt filter legs includes capacitor, inductor, and a node coupled between the capacitor and inductor. Each node of the shunt filter leg is coupled to at least one other node of another shunt filter leg of the filter with a resistive element. The harmonic filter includes a first shunt filter leg that has a resonant frequency between the center frequency and (1/1.220) times the center frequency and a second shunt filter leg that has a resonant frequency between the center frequency and 1.220 times the center frequency.

A low pass filter includes a first via-hole conductor connected to a first end portion of a first inductor and a third end portion of a second inductor and extending to another side in a lamination direction with respect to a second end portion of the first inductor and a fourth end portion of the second inductor, and a first capacitor electrically connected in parallel with at least a portion of the first inductor and a portion of the second inductor and defined by a first capacitor conductor layer. The low pass filter allows the interval between attenuation poles to be easily adjusted.

An antenna system including a signal source, at least one antenna coupled to the signal source, a matching circuit connected to the signal source at a first port and to the at least one antenna at a second port and operative to match the at least one antenna to the signal source, the matching circuit having a characteristic impedance with respect to the first port and the second port, real and imaginary parts of the characteristic impedance not being defined by the Hilbert transform.