The present disclosure relates to a slow-wave transmission line for transmitting slow-wave signals with reduced loss. In this regard, the slow-wave transmission line is formed in a multi-layer substrate and includes an undulating signal path. The undulating signal path includes at least two loop structures, wherein each loop structure includes at least two via structures connected by at least one intra-loop trace. The undulating signal path further includes at least one inter-loop trace connecting the at least two loop structures. Additionally, the slow-wave transmission line includes a first ground structure disposed along the undulating signal path. In this manner, a loop inductance is formed by each of the at least two loop structures, while a first distributed capacitance is formed between the undulating signal path and the ground structure.

A compact planar balun formed on a substrate including a hairpin-shaped conductive microstrip and a single-ended contact. The hairpin-shaped conductive microstrip includes first and second linear segments integrally formed with a U-shaped segment, and a single-ended contact is conductively coupled at a location along the first linear segment. The first and second linear segments each have a first characteristic impedance and are in parallel with each other having a first end forming first and second differential contacts and having a second end. The U-shaped segment has a second characteristic impedance that is less than the first characteristic impedance in order to achieve proper scatter parameter alignment. The U-shaped segment may be generally formed thicker or wider than the linear segments to achieve a reduced characteristic impedance. In the alternative or in addition, co-planer ground metal is formed closer to the U-shaped segment to achieve a reduced characteristic impedance.

A microstrip line filter comprising a coupling mechanism arranged to couple a first resonator and a second resonator, wherein the coupling mechanism includes a shared metallic coupling member arranged to have a predetermined dimension associated with an operation characteristics of the first and second resonators.

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.

According to an embodiment, a filter characteristic tuning apparatus includes a characteristic tuning member, an elastic member, a first movable member, a second movable member, and a driving mechanism. The elastic member comes in contact with a characteristic tuning member by deformation, and separates from the characteristic tuning member by a restoring force. The first movable member deforms the elastic member in a closing operation. The driving mechanism displaces a second movable member such that a projection opens/closes the first movable member. The characteristic tuning member changes a gap between the characteristic tuning member and the resonator by a linear driving force obtained by converting the transmitted rotary driving force.

A filter which stops the propagation of an electromagnetic wave of a predetermined frequency band in a signal line or a power supply line is provided. This filter is a conductor connected to the signal line or the power supply line. This conductor is configured to include a linear portion. The first portion of the linear portion with an end portion connected to the signal line or the power supply line has the first width, and the second portion different from the first portion of the linear portion has the second width different from the first width.

The present disclosure introduces wide tunable band filters. In one embodiment, a wide tunable band filter apparatus is described. The filter apparatus may include a microstrip patch having a plurality of symmetrical slots etched into the microstrip patch. A plurality of diodes may be coupled to the microstrip patch. Furthermore, two asymmetrical feed lines may be connected to the microstrip patch. Other embodiments are also described.

A notch filter includes a dielectric substrate, a microstrip transmission line on the dielectric substrate, and a fork-shaped open-circuited stub embedded in the microstrip transmission line.

Disclosed is a four-mode defected ground structure filter, including a four-mode defected ground structure resonator and two microstrip feed lines. The four-mode defected ground structure resonator comprises a metal dielectric substrate and a defected ground unit which is etched in one surface of the metal dielectric substrate; the microstrip feed lines are arranged at another surface of the metal dielectric substrate; shape of the defected ground unit is axially symmetric about a first central axis of the defected ground unit, and is axially symmetric about a second central axis of the defected ground unit; the first defected ground unit is provided with H-shape or quasi H-shape, the second defected ground unit is provided with L-shape, quasi L-shape, U-shape or quasi U-shape.

The present invention discloses a four-mode defected ground structure resonator, comprising a metal dielectric substrate and a defected ground unit which is etched in one surface of the metal dielectric substrate; the shape of the defected ground unit is axially symmetric about a first central axis of the defected ground unit, and also the shape of the defected ground unit is axially symmetric about a second central axis of the defected ground unit; the first defected ground unit is provided with H-shape or quasi H-shape, the second defected ground unit is provided with L-shape, quasi L-shape, U-shape or quasi U-shape. The four-mode defected ground structure resonator of the present invention is provided with four types of resonant modes, and the four types of resonant modes are provided with good tunability.