A planar structure for a planar radio frequency filter is configured to block the transmission of electromagnetic waves in at least two independent radio frequency bands, the planar structure comprising a periodic array of multipole inclusions, wherein the periodic array of multipole inclusions comprises a plurality of primary multipole inclusions having a plurality of primary poles to generate a lower frequency resonance and a plurality of secondary poles to generate a higher frequency resonance, wherein the periodic array of multipoles are arranged with arms of the plurality of primary poles overlapping with and substantially parallel to adjacent arms of the plurality of primary poles of adjacent multipole inclusions. The array of multipole inclusions may include a plurality of secondary multipole inclusions located between the plurality of primary multipole inclusions to tune the higher frequency resonance.

A power dividing circuit includes an input port, a first microstrip line, a first transmission subcircuit, a second transmission subcircuit, and a matching element. The first transmission subcircuit is coupled to a first microstrip line first end, and the first transmission subcircuit includes a first output port and a first resonance unit. The second transmission subcircuit is coupled to a first microstrip line second end, and the second transmission subcircuit includes a second output port and a second resonance unit. The matching element is coupled between the first output port and the second output port, the matching element matches impedances between the first transmission subcircuit and the second transmission subcircuit. A power divider is also provided.

A multilayer filter (1) includes an element body (2) formed by stacking a plurality of insulator layers (10), and an input terminal T.sub.IN (5), a first output terminal T.sub.OUT1 (9), and a ground terminal G (4, 8) arranged on outer surfaces of the element body (2), a first LC resonance circuit (RC2) provided in a line (S1) connecting the input terminal T.sub.IN (5) to the first output terminal T.sub.OUT1 (9) and including a first inductor (L2) and a first capacitor (C2), and an open inductor (L.sub.OPEN) having one end connected to the ground terminal (G) and the other end open are provided in the element body (2), and the open inductor (L.sub.OPEN) is arranged to face the first output terminal T.sub.OUT1 (9) or the first inductor (L2).

A resonant circuit includes a first inductor and a first capacitor which define a first series circuit and a second inductor connected in parallel to the first series circuit. The first inductor and the second inductor are coupled via a magnetic field in a direction in which magnetic fluxes passing through the inductor and the second inductor strengthen each other to effectively increase steepness in a transient band.

A multilayer filter includes a plurality of mutually coupled resonant circuits provided within a multilayer body. Capacitor internal electrodes, inductor internal electrodes, and inductor via electrodes, ground via electrodes, and input-output via electrodes are arranged within the multilayer body. The ground via electrodes and the input-output via electrodes are provided on a dielectric layer on a mounting surface, or a second dielectric layer on a first dielectric layer provided on the mounting surface. The capacitor internal electrodes arranged towards the side of the mounting surface do not overlap the input-output electrodes when viewed in plan view. With this configuration, degradation in frequency characteristics of a resonant circuit is effectively prevented by controlling one of an inductive component and a capacitive component of the resonant circuit.

A filter device includes an unbalanced terminal, balanced terminals, and first and second resonant circuits. The first resonant circuit is connected to the unbalanced terminal. The second resonant circuit is connected to the balanced terminals and electromagnetically coupled with the first resonant circuit. The first resonant circuit includes a resonator in which an inductor and a capacitor are connected in parallel between the unbalanced terminal and a reference potential. The second resonant circuit includes a resonator including an inductor connected between the balanced terminals and capacitors connected in series between the balanced terminals.

An electronic component includes a first main body including a plurality of dielectric layers stacked together, and a second main body mounted to the first main body. The second main body includes a first circuit section and a second circuit section that are each constituted by using at least one acoustic wave element and are electrically separated from each other. The first main body includes first to third ground conductor lavers located between the first and second circuit sections when seen in a Z direction.

An antenna system including a signal source, at least one antenna coupled to the signal source, a matching circuit connected to the signal source at a first port and to the at least one antenna at a second port and operative to match the at least one antenna to the signal source, the matching circuit having a characteristic impedance with respect to the first port and the second port, real and imaginary parts of the characteristic impedance not being defined by the Hilbert transform.

A resonator includes an LC resonant unit and an embedded resonant unit. The LC resonant unit includes a resonant element. The resonant element includes a first portion, a second portion, and an interface between the first portion and the second portion. The first portion is connected to the second portion through the interface. The embedded resonant unit is embedded in the LC resonant unit through the interface.

A filter circuit includes an inductor provided between a signal path and a ground and including a first end electrically connected to the ground, a resonator provided between the signal path and the ground and including a third end electrically connected to the ground, and a capacitor provided on the signal path and electrically connected to a second end of the inductor and a fourth end of the resonator. The inductor is configured using an inductor element. The resonator is configured without using the inductor element.