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 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 that can make a reflection delay of an initial stage coupling part correspond to a change in a passband due to a manufacturing error of a substrate or the like is realized. A filter according to an example embodiment includes: a substrate having a dielectric property; an initial stage coupling part formed on the substrate; and an interstage coupling part formed on the substrate. The initial stage coupling part is formed so that a reflection delay is decreased in accordance with an increase in a passband due to a manufacturing error of the substrate or the interstage coupling part, or so that the reflection delay is increased in accordance with a decrease in the passband.

An acoustic wave device includes a piezoelectric layer, an IDT electrode, a high-acoustic-velocity support substrate, and a low-acoustic-velocity film. The high-acoustic-velocity support substrate is located on an opposite side of the piezoelectric layer from the IDT electrode in the thickness direction of the piezoelectric layer. The low-acoustic-velocity film is disposed between the high-acoustic-velocity support substrate and the piezoelectric layer in the thickness direction. The high-acoustic-velocity support substrate includes a base region and a surface region disposed nearer to the low-acoustic-velocity film than the base region in the thickness direction and whose crystal quality is worse than that of the base region. The surface region includes first and second layers disposed nearer to the base region than the first layer in the thickness direction and whose crystal quality is better than that of the first layer.

Provided are a resonator having a good Q value and a filter using the resonator. The resonator has: a via electrode portion formed inside a dielectric substrate; a plurality of shielding conductors formed on the dielectric substrate to surround the via electrode portion; a first strip line which is connected to one end of the via electrode portion in the dielectric substrate and faces a first shielding conductor among the plurality of shielding conductors; and a second strip line which is connected to the other end of the via electrode portion in the dielectric substrate and faces a second shielding conductor among the plurality of shielding conductors.

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 resonant unit and a filter, where the resonant unit includes a dielectric substrate, a metal microstrip disposed on a plane of the dielectric substrate, where the metal microstrip is used as a signal input/output port, and a defected ground structure disposed on another plane opposite to the plane of the dielectric substrate, where the defected ground structure includes a ground loop and an interdigital structure located inside the ground loop, the interdigital structure includes multiple fingers, and the ground loop or at least one finger in the interdigital structure includes at least one embedded interdigital structure. Harmonic suppression capabilities of the resonant unit and the filter can be improved, and an area can be reduced.

Metallization layer structures for reduced changes in radio frequency characteristics due to registration error and associated methods are provided herein. An example resonator includes a first conductive layer defining an error limiting feature and a second conductive layer. The resonator further includes at least one communication feature configured to electrically couple the first conductive layer and the second conductive layer at a communication position. The error limiting feature is configured to reduce changes in radio frequency characteristics of the resonator due to registration error. Methods of manufacturing resonators are also provided herein.

A coaxial filter comprises a housing that surrounds a receiving space. The housing comprises a trough-shaped housing element with sidewalls and a front wall. The housing further comprises a further trough-shaped housing element, wherein the two trough-shaped housing elements are placed on top of one another, thus forming the receiving space; or a lid arrangement which, together with the trough-shaped housing element forms the receiving space. At least one resonator inner conductor arrangement comprises a connecting bridge, with which resonator inner conductors are conductingly connected.

The present invention provides a compact filter with excellent characteristics. This filter has a plurality of resonators, each of which having: via electrode parts formed inside a dielectric substrate; and a first strip line that faces a first shielding conductor of a plurality of shielding conductors formed so as to surround the via electrode parts, the first strip line being connected to one end of the via electrode parts. The positions of the via electrode parts of the first resonator of the plurality of resonators, and the positions of the via electrode parts of the second resonator, which is adjacent to the first resonator, are mutually offset in a first direction (X), which is the longitudinal direction of the first strip line.