A tunable RF filter circuit (AHF) is specified which enables good electrical properties, good tunability and simple driving despite low complexity. In this case, the filter circuit comprises a first and a second signal route (SW1, SW2) in a signal path (E, A). At least three resonant circuits (RK1, RK2, RK3) are arranged one after another in the second signal route and interconnect the second signal route with ground. The resonant circuits are electrically and/or magnetically coupled (K) and each comprise a tunable impedance element. The second signal route contains an impedance element (IMP).

An integrated circuit (IC) includes an input pad and an output pad separated from the input pad by a predetermined distance. A plurality of capacitors are coupled in series between the input pad and the output pad. The plurality of capacitors are distributed to substantially span the predetermined distance. An inductor is formed from a bond wire, having a first end attached at the first input pad and a second end attached at the output pad. The inductor and plurality of capacitors configured to form a predetermined open circuit resonance.

A multilayer filter includes first and second ground electrodes and first and second LC resonators. The first LC resonator includes a first line electrode, a first capacitor electrode, a first via conductor, and a second via conductor. The second via conductor extends from the first line electrode to a first capacitor electrode side and connects the first line electrode and the first ground electrode. The second LC resonator includes a second line electrode, a second capacitor electrode, a third via conductor, and a fourth via conductor. The fourth via conductor extends from the second line electrode to a second capacitor electrode side and connects the second line electrode and the second ground electrode.

A phase shifter module includes a base material, a common terminal, and individual terminals, the common terminal and the individual terminals being provided at the base material. Inside the base material, phase shifters that are connected between the individual terminals and the common terminal, respectively, are provided. The phase shifters each include a primary coil and a secondary coil that is coupled to the primary coil by magnetic field coupling and define a transformer phase shifter. With this configuration, a phase shifter module for use with SAW filters while reducing or preventing interference among the SAW filters, a multiplexer/demultiplexer that includes the phase shifter module, and a communication apparatus that includes the phase shifter module, are obtained.

A tuneable band pass filter (BPF), including a first transmission line electromagnetically coupled to a second transmission line, wherein a length of at least one of the first transmission and the second transmission line is adjustable, and wherein a frequency of a passband of the BPF is directly related to the length of the adjustable transmission line.

Filter circuits having a resonator-based filter and a magnetically-coupled filter are disclosed. A filter circuit is deployed with a resonator-based passband filter connected to a magnetically-coupled filter which mitigates or reduces flyback of the resonator-based filter. The magnetically-coupled filter can be a passband filter with a relatively low insertion loss. The magnetically-coupled filter can be designed to mitigate flyback of the resonator-based filter by attenuating frequency response at selected frequency ranges.

A multilayer fringe capacitor includes first and second interdigitated capacitor electrodes, both parallel to and intersecting a first planar surface; third and fourth interdigitated capacitor electrodes, the first and second electrodes parallel to and separated by a non-zero distance from the third and fourth electrodes; a first set of coupling vias that electrically couples the first electrode to the third electrode; and a second set of coupling vias that electrically couples the second electrode to the fourth electrode.

A variable-frequency LC filter that has sharp attenuation characteristics and that does not increase the size of a substrate and a high-frequency frontend module using such a variable-frequency LC filter are provided. A first variable capacitor and a second variable capacitor are disposed on a principal surface such that strength of magnetic field coupling caused between a first inductor and a third inductor is greater than strength of magnetic field coupling caused between a second inductor and the first inductor and than strength of magnetic field coupling caused between the second inductor and the third inductor.

A circuit includes a first amplifier path configured to carry a first radio frequency signal, a second amplifier path configured to carry a second radio frequency signal, a first resonator connected to the first and second amplifier paths, the first resonator being configured to resonate at a radio frequency to isolate the first and second radio frequency signals from one another and further configured to pass signals at a baseband frequency, and a second resonator coupling the first resonator and a reference voltage node, the second resonator being configured to pass signals at the baseband frequency to the reference voltage node.

The disclosure relates to an ultra-wide passband five-order band-pass filter based on an LTCC process. The ultra-wide passband five-order band-pass filter comprises a ceramic substrate, a bottom input electrode, a bottom output electrode and a bottom grounding electrode. Five parallel resonators, a grounding polar plate, two series connection capacitors, two series connection inductors, a cross-coupling capacitor and a parallel inductor are arranged in the ceramic substrate; the two series connection capacitors comprise a first series capacitor and a second series capacitor; the two series connection inductors comprise a first series inductor and a second series inductor; and according to the filter, a five-order parallel resonance structure is adopted, out-of-band suppression is deepened through the five parallel resonance units, a cross coupling capacitor, a parallel inductor and two series connection inductors are innovatively introduced.