A BAW resonator filter can include a BAW resonator pass-band filter ladder, the BAW resonator pass-band filter ladder can be configured to pass frequency components of an input signal in a pass-band of frequencies received at an input node of the BAW resonator pass-band filter ladder to an output node of the BAW resonator pass-band filter ladder. A first rejection-band series resonator can be coupled in series between an input port of the BAW resonator pass-band filter ladder and the input node, the first rejection-band series resonator can have a first anti-resonant frequency peak in a rejection-band of frequencies that is less than the pass-band of frequencies. A second rejection-band series resonator can be coupled in series between an output port of the BAW resonator filter and the output node, the second rejection-band series resonator can have a second anti-resonant frequency peak in the rejection-band of frequencies.

An interdigitated RF filter. The interdigitated RF filter includes input fingers connected to an input node and output fingers connected to an output node where at least one input finger is connected the output node or at least one output finger is connected to the input node. The described interdigitated RF filter can be implemented in various configurations such as series, shunt, ladder or a combination thereof.

A filter (10) has a first passband and a second passband on a higher frequency side than the first passband and includes a series arm circuit (11) and a parallel arm circuit (12), wherein the parallel arm circuit (12) includes a parallel arm resonator (p1) connected between a node (x1) and ground and having a resonant frequency frp located between a first passband and a second passband, an inductor (L1) connected between the node (x1) and the ground, and an inductor (L2) connected between the node (x1) and the ground and connected in series to the parallel arm resonator (p1), and a circuit in which the parallel arm resonator (p1) and the inductor (L2) are connected in series is connected in parallel to the inductor (L1).

A filter having a pass band includes a series circuit in which a series arm resonator and a first inductor are connected in series with each other and which forms at least part of a signal path R connecting a first input/output terminal and a second input/output terminal and a parallel arm resonator connected between one end of the series circuit and a ground. The series circuit becomes inductive in the pass band. An anti-resonant frequency of the series arm resonator is higher than a frequency at a higher-frequency end of the pass band. A resonant frequency of the parallel arm resonator is higher than the anti-resonant frequency of the series arm resonator.

In tuning a radio frequency (RF) module including a non-volatile tunable RF filter, a desired frequency and an undesired frequency being provided by an amplifier of the RF module are detected. The non-volatile tunable RF filter is coupled to an output of the amplifier of the RF module. A factory setting of an adjustable capacitor in the non-volatile tunable RF filter is changed by factory-setting a state of a non-volatile RF switch, such that the non-volatile tunable RF filter substantially rejects the undesired frequency and substantially passes the desired frequency. The adjustable capacitor includes the non-volatile RF switch, and the factory setting of the adjustable capacitor corresponds to a factory-set state of the non-volatile RF switch. An end-user is prevented access to the non-volatile RF switch, so as prevent the end-user from modifying the factory-set state of the non-volatile RF switch.

An amplification apparatus as the embodiment of the present invention includes a switching amplifier and an adjuster. The switching amplifier is driven on the basis of a control signal and amplifies an input signal to be amplified to generate an amplified signal. The adjuster adjusts at least one of the signal to be amplified and the control signal before being input into the switching amplifier. In addition, the adjuster adjusts so that timing when the control signal turns from LOW to HIGH aligns with timing when the signal to be amplified turns from LOW to HIGH, or aligns with timing when the signal to be amplified turns from HIGH to LOW.

An integrated isolator circuit for isolating receiver and transmitter in a Time-Division Duplex transceiver is disclosed. The integrated isolator circuit comprises a first node, a second node and. a third node. The integrated isolator circuit further comprises a first capacitor connected in series with a first switch and connected between the first and second nodes. The integrated isolator circuit further comprises a first inductor connected between the first and second nodes and a second capacitor connected between the second node and the third node. The first switch has an on state and an off state, and the integrated isolator circuit is configured to have a different impedance at a certain operating frequency by controlling the state of the first switch.

A diplexer (100) includes: first and second directional couplers (106A, 106B); and first and second filters (101A, 101B). The filters (101A, 101B) each include a plurality of resonators (110A to 150A, 110B to 150B) that are electromagnetically coupled. The resonators (110A to 150A, 110B to 150B) each have a broad wall that is in a shape of a circle or a regular polygon with six or more vertices, and two resonators, which are coupled together, of the resonators (110A to 150A, 110B to 150B) are arranged such that D<R.sub.1+R.sub.2 is satisfied, where R.sub.1 and R.sub.2 represent radii of circumcircles of the broad walls of the two resonators and D represents a center-to-center distance between the two resonators.

In a band pass filter, a signal input into a first terminal is transmitted to a first LC resonator and a second LC resonator in this order and is then output from a second terminal. The band pass filter includes a third inductor and a third capacitor. A first end of the third inductor is electrically connected to the ground. The third capacitor is electrically connected between a second end of the third inductor and a node between the first LC resonator and the second LC resonator.

A multilayer band pass filter includes first and second LC parallel resonators. The first and second LC parallel resonators include a first inductor and a second inductor, respectively. The first inductor includes a first line conductive pattern, a first via conductive pattern, and a second via conductive pattern. The first line conductive pattern extends in the X-axis direction on a first dielectric layer. The first via conductive pattern and second via conductive pattern extend from the first line conductive pattern toward a second dielectric layer. The second inductor includes a third via conductive pattern extending in the Z-axis direction.