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.

Techniques for isolation between filters using inductive coupling cancellation are disclosed. An apparatus includes a first filter including a first plurality of inductors and a second filter including a second plurality of inductors. The first and second filters are implemented physically adjacent to one another. First and second ones of the first plurality of inductors and a first one of the second plurality of inductors are polarized in a first direction, while a second one of the second plurality of inductors is polarized in a second direction opposite that of the first direction. The second one of the second plurality of inductors is physically adjacent to one of the first and second ones of the first plurality of inductors such that magnetic coupling currents induced into one another are canceled.

An acoustic wave device includes a piezoelectric substrate made of LiNbO.sub.3, and a dielectric film provided on the piezoelectric substrate to cover first and second IDT electrodes on the piezoelectric substrate. The first and second IDT electrodes include main electrode layers. When wave lengths determined by electrode finger pitches of the first and second IDT electrodes are .sub.1 and .sub.2, respectively, the average value thereof is .sub.0, .sub.1/.sub.0=1+X, and .sub.2/.sub.0=1X, a relationship of 0.05X0.65 is satisfied. The wavelength .sub.1 is the longest, and the wavelength .sub.2 is the shortest. In Euler angles (, , ) of the piezoelectric substrate, is 05, is 010, and satisfies Expression 1, wherein a relationship of B.sub.1<Tr0.10.sub.0 and B.sub.2<Tr0.10.sub.0 are satisfied.

A filter circuit for use with a system configured to be coupled with an electrical load, the filter circuit comprising a first filter, wherein the first filter is configured to receive a first voltage and provide an output voltage, the output voltage being the first voltage after filtering by the first filter, and the filter circuit is configured to adjust the bandwidth of the first filter in response to a load transient.

An electronic component includes a stack, a first inductor, a second inductor, a third inductor, and a shield conductor. The shield conductor includes a first conductor part provided on a side surface of the stack and a second conductor part provided on a side surface of the stack. The electronic component further includes a first connecting conductor that connects two columnar conductors of the first inductor and the first conductor part, a second connecting conductor that connects two columnar conductors of the second inductor and the second conductor part, and a third connecting conductor that connects two columnar conductors of the third inductor and the first conductor part.

A high frequency band pass filter with a coupled surface mount transition is provided, including a filter substrate, circuit connection elements defining input and an output elements provided on a surface of the filter substrate, electronic filter components provided on the first surface of the filter substrate, and impedance matching structures provided on the first surface of the filter substrate between the electronic filter components and the respective input and output elements. Signal connection structures are provided on an opposed surface of the filter substrate, in locations that positionally correspond to respective positions of the input and output elements. The respective signal connection elements are capacitively coupled, through a thickness direction of the filter substrate, to a respective one of the input and output elements on the opposed surface of the filter substrate without the presence of any vertical conductive structures within the filter substrate at the input and the output elements.

A wideband tunable combiner system for a dual frequency diversity transmitter is provided that includes a tunable capacitance network. Incoherent RF signals with the same audio signal may be combined with the system into a combined RF signal for transmission on an antenna. The tunable capacitance network, in conjunction with a combiner and a band pass fitter, may optimize the isolation between the incoherent RF signals and reduce intermodulation, white maintaining a wide operating bandwidth. The capacitance value of the tunable capacitance network may be selected based on the frequencies of the incoherent RF signals, RF spectrum information, or antenna loading data. An RF transmitter including the tunable combiner system may have improved spectral efficiency and performance and take advantage of available spectrum.

What is specified is a combined impedance matching and RF filter circuit having improved impedance matching in conjunction with good frequency-tunability of the filter circuit. The circuit comprises a reactance elimination circuit for reducing the reactance and a tunable RF filter circuit, which is frequency-tunable and can carry out a resistance matching.

A second conductor plane (102) is formed in a layer different from a layer in which a first conductor plane (101) is formed, and faces the first conductor plane (101). A first transmission line (104) is formed in a layer different from the layers in which the first conductor plane (101) and the second conductor plane (102) are formed, and faces the second conductor plane (102), and one end thereof is an open end. A conductor via (106) connects the other end of the first transmission line (104) and the first conductor plane (101). An insular conductor (112) is connected to a portion of the first transmission line (104) other than a portion thereof at which the transmission line (104) is attached to the conductor via (106), is located in a layer different from the layer in which the second conductor plane (102) is located, and faces the second conductor plane (102).

Embodiments of radio frequency (RF) filtering circuitry are disclosed. In one embodiment, the RF filtering circuitry includes a first port, a second port, a first RF filter path, and a second RF filter path. The first RF filter path is connected between the first port and the second port and includes at least a pair of weakly coupled resonators. The weakly coupled resonators are configured such that a first transfer response between the first port and the second port defines a first passband. The second RF filter path is coupled to the first RF filter path and is configured such that the first transfer response between the first port and the second port defines a stopband adjacent to the first passband without substantially increasing ripple variation of the first passband defined by the first transfer response.