The disclosure provides a filtering module for a cavity filter having a housing defining an enclosed cavity, wherein a surface of the cavity is electromagnetically conductive; and a plurality of planar resonators arranged within the cavity, one or more of the resonators being rotatable about an axis of rotation so as to vary an electric-field coupling between the resonator and other resonators of the plurality of resonators. The disclosure also provides a cavity filter having an input for receiving a signal to be filtered; a plurality of filtering modules, each filtering module comprising: a cavity, wherein a surface of the cavity is electromagnetically conductive; and a plurality of resonators arranged within the cavity, at least one of the resonators being movable so as to vary an electromagnetic coupling between the resonator and other resonators of the plurality of resonators; and an output for outputting a filtered signal.

A band pass filter includes filter circuits, first and second intermediate circuits, and a first capacitor. The first intermediate circuit includes an inductor connected between second and third capacitors. The second intermediate circuit includes an inductor connected between third and fourth capacitors. Resonant circuits included in the filter circuit are connected to ground via a common capacitor. Resonant circuits included in the filter circuit are connected to the ground via a common capacitor. The first capacitor is connected between the first and second intermediate circuits.

Provided is a filter capable of suppressing variation in characteristics. A filter has: a plurality of resonators each having a via electrode and a first strip line that is opposed to a first shielding conductor and connected to one end of the via electrode; a first coupling capacitive electrode that has a first comb-shaped electrode including a plurality of first electrodes and that is provided to the first resonator; and a second coupling capacitive electrode that is provided to the second resonator, that has a second comb-shaped electrode including a plurality of second electrodes, and that is formed on the same layer as that of the first coupling capacitive electrode, wherein the first and second electrodes are arranged so as to be adjacent to each other.

A filter includes first and second resonators and first and second stub resonators. Each of the first and second resonators includes a first conductor part and a second conductor part electrically connected to the first conductor part and having an impedance smaller than an impedance of the first conductor part. The first stub resonator is electrically connected to the first conductor part of the first resonator. The second stub resonator is electrically connected to the first conductor part of the second resonator. The shape of the first stub resonator and the shape of the second stub resonator are different from each other.

A filter circuit includes an input node, an output node, a first filtering element and a second filtering element. The first filtering element has a first terminal coupled to the input node and a second terminal, and is configured to provide a first signal conducting path toward the second terminal for conducting a first signal received at the input node to the second terminal. The second filtering element has a first terminal coupled to the input node and a second terminal, and is configured to provide a second signal conducting path toward the output node for conducting a second signal received at the input node to the output node. The second terminal of the first filtering element and the second terminal of the second filtering element are open-circuit terminals.

An electrically controllable RF circuit that includes an EC cell and an EAP-based actuator configured to produce relative movement of an electrode of the electrochromic cell and an electrically conducting patch or another electrode electromagnetically coupled thereto. In one embodiment, the RF circuit operates as a tunable patch antenna whose frequency characteristics can be changed by changing the bias voltages applied to the EC cell and EAP-based actuator. Advantageously, the capability to tune the antenna using two different tuning mechanisms (i.e., a dielectric-permittivity based tuning mechanism implemented using the EC cell and a geometry-based tuning mechanism implemented using the EAP-based actuator) provides more degrees of control over the pertinent antenna characteristics compared to what is available in some other antenna designs. In another embodiment, the RF circuit can operate as a tunable RF filter whose frequency characteristics can similarly be changed using these two different tuning mechanisms.

The invention presents a LTCC balun filter using two out-of-phase filtering circuits. The LTCC balun filter is comprised of three half-wavelength resonators and grounds which are located on fourteen metal layers. Vias are utilized to connect different metal parts. The first, fourth, seventh, eleventh and fourteenth metal layers are the ground. The three half-wavelength resonators are on the second, third, fifth, sixth, eighth, ninth, tenth, twelfth and thirteenth metal layers. By adjusting the coupling parts of the three half-wavelength resonators, namely the lengths of the seventh, eighth, ninth, tenth and eleventh layers, as well as the distances between them, the coupling strength between the half-wavelength resonators can be tuned. In addition, the quality factor of the circuit can be improved by tuning the port positions. By using the multi-layer LTCC technology, the present invention has the advantage of compact size, novelty, creativity and practicability.

A filter apparatus is disclosed. The filter apparatus may include a plurality of dielectric layers. The plurality of dielectric layers may include one or more first dielectric layers formed of a first dielectric material and one or more second dielectric layers formed of a second dielectric material. The second dielectric material of the one or more second dielectric layers being different than the first dielectric material of the one or more first dielectric layers. The filter apparatus may further include one or more thin-film metal layers arranged between at least one dielectric layer of the plurality of dielectric layers and an additional dielectric layer of the plurality of dielectric layers.

A high pass filter includes a first LC series resonator including a first end connected to a signal path, and a second end connected to at least one ground terminal, a second LC series resonator including a third end electrically connected to the signal path, and a fourth end connected to the at least one ground terminal, and a third capacitor between a first portion extending from a first capacitor to a first inductor and a second portion extending from a second capacitor to a second inductor.

The invention provides a bandpass filter, comprising: a substrate with a plurality of dielectric layers; a plurality of resonators; and a plurality of ground layers each having one slot arranged on; wherein the plurality of resonators are arrayed vertically each on respective one of the plurality of dielectric layers alternately without any of offsets, and each of the plurality of ground layers is between adjacent dielectric layers. Adjacent slots are arranged in opposite sides of the ground layers. The invention also provides a method of fabricating the bandpass filter.