A method of constructing an RF filter comprises designing an RF filter that includes a plurality of resonant elements disposed, a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and a sub-band between the transmission zeroes. The non-resonant elements comprise a variable non-resonant element for selectively introducing a reflection zero within the stop band to create a pass band in the sub-band. The method further comprises changing the order in which the resonant elements are disposed along the signal transmission path to create a plurality of filter solutions, computing a performance parameter for each of the filter solutions, comparing the performance parameters to each other, selecting one of the filter solutions based on the comparison of the computed performance parameters, and constructing the RF filter using the selected filter solution.

An RF filter, particularly a stripline type RF filter, includes a casing and two or more strip-conductor-type resonators in the casing. At a distance from the ends of the resonator, between the resonator sides, there are one or more coupling lines forming an integral piece with the resonators.

A filter apparatus includes a first conductive signal line configured to form a first radio frequency resonator; a second conductive signal line configured to form a second radio frequency resonator; a cross-coupling element comprising a first electrode arranged to couple capacitively to the first conductive signal line, a second electrode arranged to couple capacitively to the second conductive signal line, and an electrically conductive signal line coupling the first electrode to the second electrode. The cross-coupling element is bendable with respect to the first conductive signal line and the second conductive signal line to adjust the capacitive coupling.

Balun with tunable bandpass filter characteristic includes first, second and third coupling elements disposed on a substrate. The first and second coupling elements are arranged on the substrate relative to the third coupling element to couple two identical but out of phase signals to form a corresponding unbalanced signal in the third coupling element. A plurality of tunable resonator elements are distributed within an area of the substrate defined on one side by the first and second coupling elements and on an opposing side by the third coupling element. The tunable resonator elements are configured to selectively produce a bandpass filter response.

This invention can reduce the size of a filter device as compared to a conventional filter device having the same coupling degree. A filter device (1) includes: a substrate (11); strip-shaped conductors (12a1 to 12a5); and a ground conductor layer (13), an area facing an area interposed between adjacent ones of the strip-shaped conductors (between 12a1 and 12a2 and between 12a2 and 12a3) having a first recessed portion (recessed portions 11a1 and 11a2) having a surface covered with the ground conductor layer (13).

An object of this invention is to reduce the size of a filter device. Provided is a filter device (1) including: a substrate (11) including a first main surface and a second main surface (111, 112); strip-shaped conductors (12a1 to 12a5) provided to the first main surface (111); and a ground conductor layer (13) provided at least to the second main surface (112), the second main surface (112) having a recessed portion (11ai) provided for each strip-shaped conductor (12ai), the recessed portion (11ai) overlapping the strip-shaped conductor (12ai) in plan view and having a surface covered with the ground conductor layer (13).

A filter in a wireless communication system includes: a cover; a housing; a printed circuit board (PCB); a resonance plate provided between the cover and the PCB; and a plurality of resonators provided on a single layer in the resonance plate.

A filter in a wireless communication system includes: a cover; a housing; a printed circuit board (PCB); a resonance plate provided between the cover and the PCB; and a plurality of resonators provided on a single layer in the resonance plate.

A UWB band pass filter that is formed by a circuit board. The circuit board includes a first dielectric layer made of a dielectric substrate, a filter structure made of electrically conductive material, on a first side of the first dielectric layer, a first ground layer made of electrically conductive material, on a second side of the first dielectric layer. The filter structure has an input terminal and an output terminal between which a line extends that includes multiple first line sections and second line sections, and wherein the filter structure has multiple stubs that are situated between the first line sections and that branch off from the second line sections. The first line sections and the stubs are situated in parallel. The longitudinal line of the middle first line sections is inserted, from which two open stubs that are rotationally symmetrical about the middle first line sections branch off.