Methods and system for using a multifunctional filter to minimize insertion loss in a multi-mode communications system are described. Specifically described is a multifunctional filter that is configurable to operate in a band-pass mode when a first type of signal is propagated through the multifunctional filter, and to operate in a low-pass mode when a second type of signal is propagated through the multifunctional filter. The multifunctional filter presents a lower insertion loss to the second type of signal when operating in the low-pass mode than in the band-pass mode.

A multi-tune filter system and a control system for operating the multi-tune filter system are described herein. The multi-tune filter system is a tunable frequency range filter. Further, the multi-tune filter system is a digitally programmable filter with an adjustable passband between first and second customizable frequency bounds f1, f2.

A flexible multi-path RF adaptive tuning network switch architecture that counteracts impedance mismatch conditions arising from various combinations of coupled RF band filters, particularly in a Carrier Aggregation-based (CA) radio system. In one version, a digitally-controlled tunable matching network is coupled to a multi-path RF switch in order to provide adaptive impedance matching for various combinations of RF band filters. Optionally, some or all RF band filters include an associated digitally-controlled filter pre-match network to further improve impedance matching. In a second version, some or all RF band filters coupled to a multi-path RF switch include a digitally-controlled phase matching network to provide necessary per-band impedance matching. Optionally, a digitally-controlled tunable matching network may be included on the common port of the multi-path RF switch to provide additional impedance matching capability. In a third version, CA direct mapped adaptive tuning networks include filter tuning blocks for selected lower frequency bands.

Integrated circuit architectures for load and input matching that include a capacitance selectable between a plurality of discrete levels, which are associated with a number of field effect transistors (FET) capacitor structures that are in an on-state. The capacitance comprises a metal-oxide-semiconductor (MOS) capacitance associated with each of the FET capacitor structures, and may be selectable through application of a bias voltage applied between a first circuit node and a second circuit node. Gate electrodes of the FET capacitor structures may be coupled in electrical parallel to the first circuit node, while source/drains of the FET capacitor structures are coupled in electrical parallel to the second circuit node. Where the FET capacitor structures have different gate-source threshold voltages, the number of FET capacitor structures in the on-state may be varied according to the bias voltage, and the capacitance correspondingly tuned to a desired value. The FET capacitor structures may be operable in depletion mode and/or enhancement mode.

A configurable micro-acoustic RF filter comprises first and second filter subsections (140, 150) and at least one switch (160) to selectively bypass or activate the second filter subsection (150). The filter sections include at least one serially connected and at least one shunt connected micro-acoustic resonator.

Aspects of this disclosure relate to a radio frequency system with tunable notch filtering. The radio frequency system includes a first tunable filter and a second tunable filter. The first tunable filter is coupled between an output of a power amplifier and a radio frequency switch. The second tunable filter is coupled between an antenna switch and an antenna node. The second tunable filter has a notch at a lower frequency than a notch of the first tunable filter. Related methods and wireless communication devices are also disclosed.

Aspects of this disclosure relate to a radio frequency system with tunable notch filtering. The radio frequency system includes a first tunable filter and a second tunable filter. The first tunable filter is coupled between an output of a power amplifier and a radio frequency switch. The second tunable filter includes mutually coupled inductors and a tunable impedance circuit electrically connected to at least one of the mutually coupled inductors. The second tunable filter is coupled between an antenna switch and an antenna node. Related methods and wireless communication devices are also disclosed.

Customizable tunable filters are provided herein. In certain implementations, a tunable filter including: a first filter bank including a plurality of high-pass filters each having a different cutoff frequency, and a second filter bank including a plurality of low-pass filters each having a different cutoff frequency. The tunable filter further includes a first pair of switches configured to select a first filter chosen from the first filter bank, and a second pair of switches configured to select a second filter chosen from the second filter bank. The tunable filter operates with a first cutoff frequency of the first filter and with a second cutoff frequency of the second filter.

In a first approach, a reconfigurable radio frequency (RF) filtering module includes a phase-change material (PCM) RF switch bank and an RF filter bank. Each RF filter in the RF filter bank is capable to be engaged and disengaged by a PCM RF switch in the PCM RF switch bank. In a second approach, a tunable RF filter includes PCM RF switches and a capacitor and/or an inductor. Each of the capacitor and/or inductor is capable to be engaged and disengaged by at least one PCM RF switch of the PCM RF switches. In a third approach, an adjustable passive component includes multiple segments and a PCM RF switch. A selectable segment in the multiple segments is capable to be engaged and disengaged by the PCM RF switch. In all approaches, each PCM RF switch includes a PCM and a heating element transverse to the PCM.

A filter includes: a series-arm circuit; a first parallel-arm circuit connected to a ground and a node; and a second parallel-arm circuit connected to the ground and a node. The first parallel-arm circuit includes a parallel-arm resonator, and a first switch circuit. The second parallel-arm circuit includes a parallel-arm resonator, and a second switch circuit. The first switch circuit includes a first switch. The second switch circuit includes a second switch. A voltage across the first switch is lower than a voltage across the second switch. A stack count of the first switch is lower than a stack count of the second switch.