A tunable dual-band resonator and a tunable dual-band band-pass filter using the tunable dual-band resonator. The dual-band resonator is structured such that a stub is added to each half-wavelength resonator provided with half-wavelength resonator protrusions (capacity-component adjust parts). The dual-band resonator is made up of an odd-number mode resonator in a shape including a ground conductor disposed on the back surface of a dielectric body, and a strip conductor disposed on the top surface thereof, and an even-number mode resonator in such a shape as to be formed when the stub is connected to an end face on the opposite side of the open-end of the strip, characterized in that a dielectric rod circular in cross section is provided in the space above the respective stubs, and another dielectric rod circular in cross section is provided in the space above the half-wavelength resonator protrusions.

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 filter device includes a body, a ground terminal, and resonators in the body and coupled to each other by electromagnetic field coupling. The resonators include a first resonator coupled to an input terminal, a second resonator coupled to an output terminal, and third and fourth resonators. The second resonator is adjacent to the first resonator in a first direction. The third resonator is adjacent to the first resonator in a second direction perpendicular to the first direction. The fourth resonator is adjacent to the third resonator in the first direction. The third and fourth resonators partially share a path to the ground terminal.

A filter device includes a stack including a plurality of dielectric layers stacked together, and a resonator configured using a conductor integrated into the stack. Each of the plurality of dielectric layers is formed of a dielectric material, and has a resonance frequency that changes depending on a temperature. In the dielectric material, the resonance frequency changes linearly with respect to a change in the temperature when the temperature is within a first temperature range, and the resonance frequency changes nonlinearly with respect to the change in the temperature when the temperature is within a second temperature range.

Methods and apparatus, including computer program products, are provided filters. In some example embodiments, there is provided a radio frequency filter including at least one resonant circuit selectable to vary at least the selectivity of the radio frequency filter, wherein the selectivity is varied based on at least one of a first amount of transmit power being used at a user equipment and a second amount of received signal power. Related apparatus, systems, methods, and articles are also described.

An antenna having a line feed delivering a radiofrequency (RF) signal to or from a radial waveguide is provided. The radial waveguide may include radiating elements on its periphery for converting the RF signal into a wireless signal. Filter elements are disposed within the waveguide, interposed radially between the line feed and the waveguide periphery. The filter elements are controllable for tunably filtering of the RF signal in their vicinity. Portions of the RF signal propagating through the waveguide in different direction may be bandpass filtered differently or blocked, thereby allowing for both beamsteering and bandpass filtering to support multiple frequency bands concurrently. Also provided is a design for the filter elements as tunable filter components of a frequency selective surface.

A filter device for multi-band wireless communication includes a first circuit characterized by a first pass-band from a first frequency to a second frequency; a second circuit characterized by a second pass-band from a frequency no smaller than the first frequency to a third frequency, the third frequency being no higher than the second frequency but higher than the first frequency; a third circuit characterized by a third pass-band from a fourth frequency to a frequency no greater than the second frequency, the fourth frequency being no smaller than the first frequency but smaller than the second frequency; and a switch configured to connect the first circuit either to the second circuit to reconfigure a first filter with the second pass-band or to the third circuit to reconfigure a second filter with the third pass-band.

A directional coupler includes a main line, a sub line electromagnetically coupled to the main line, a coupling output terminal connected to one end of the sub line, a filter connected between the one end of the sub line and the coupling output terminal, and a filter with a pass band higher than a pass band of the filter. One end of the filter is connected to the coupling output terminal. Another end of the filter is terminated.

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.

A filter device includes a dielectric substrate, first and second ground electrodes connected to a ground terminal, and resonators between the ground electrodes and electromagnetically coupled to each other. The ground electrodes are at different positions in a normal direction of the dielectric substrate. Each of the resonators includes a first capacitor electrode partially overlapping with the first ground electrode in plan view of the dielectric substrate, a second capacitor electrode partially overlapping with the second ground electrode in plan view of the dielectric substrate, and a via connecting the capacitor electrodes. The resonators include a first resonator connected to an input terminal, a second resonator connected to an output terminal, and a third resonator between the first and second resonators. Shunt electrodes are connected to the via and the ground terminal in the first and second resonators, respectively.