Multi-band filters, communications devices, and methods of designing multi-band filters are disclosed. A multi-band filter has a lower pass-band and an upper pass-band separated by an intervening stop-band. The multi-band filter includes a first ladder network and a second ladder network coupled in series. The first ladder network provides transmission zeros at frequencies below a lower edge of the lower pass-band and transmission zeros at frequencies above an upper edge of the upper pass-band. The second ladder network provides transmission zeros at frequencies within the intervening stop-band.

The present application provides a filtering circuit and a TV antenna amplifier, the filtering circuit includes a switching module, and the switching module includes a control unit and at least two filtering units. The present application switchably render one of the at least two filtering units conductive through the control unit, and filter the signals of different frequencies in the input signals through the at least two filtering units, so that different filtering units can be switched according to the filtering requirements of the frequency signal in different regions, which makes it a wide application range.

A capacitor structure is described. The capacitor structure includes a substrate, a plurality of source/drain regions formed in the substrate, and a plurality of gates formed above the substrate. The plurality of gates formed above the substrate such that each of the plurality of gates is formed between each pair of source/drain regions of the plurality of source/drain regions to form a channel between each pair of source/drain regions.

Communications devices, triplexers, high-pass filters, and low-pass filters are disclosed. A communications device includes a triplexer having a common port and first, second, and third branch ports. A hybrid LC/SAW high-pass filter is connected between the common port and the third branch port, a hybrid LC/SAW low-pass filter is connected between the common port and an internal node, an LC high-pass filter is connected between the internal node and the second branch port, and an LC low-pass filter is connected between the internal node and the first branch port.

A filter includes shunt circuits coupled between a reference node and each of an input port, an output port, a first node, and a second node. Resonant networks are coupled between the input port and the second node, and between the first node and the output port. Storage element circuits are coupled between the input port and the first node, and between the second node and the output port. The shunt circuits have an equivalent shunt circuit frequency response that partly defines a high passband frequency of the filter, the resonant networks have an equivalent resonant network frequency response that partly defines a low passband frequency of the filter, and the storage element circuits have an equivalent storage element circuit frequency response that defines a stopband frequency of the filter between the low passband frequency and the high passband frequency.

A radio-frequency module includes switch elements, first signal paths, band pass filters, first matching circuits, second signal paths, and second matching circuits. Each of the first signal paths is connected between one end of a corresponding one of the switch elements and an antenna terminal. Each of the band pass filters is connected to a corresponding one of the first signal paths and allows a radio-frequency signal of one of the plurality of frequency bands to pass therethrough. Each of the first matching circuits is connected to a corresponding one of the first signal paths. Each of the second signal paths is connected to a corresponding one of the switch elements. Each of the second matching circuits is connected to a corresponding one of the second signal paths. A component included in the first matching circuits and a component included in the second matching circuits are electromagnetically coupled.

This disclosure relates to radio frequency (RF) front end circuitry used to route RF signals. In one embodiment, the RF front end circuitry has a filter circuit and a switch device. The switch device includes a common port, an RF port, and switchable path connected in series between the common port and the RF port. The switch device is configured to present approximately the filter capacitance of the filter circuit at the common port when the switchable path is closed. However, when the switchable path is open, the switch device is configured to present a device capacitance at the common port that is approximately equal to the filter capacitance of the filter circuit. In this manner, if the common port is connected to an antenna, the capacitance seen by the antenna from the common port remains substantially unchanged regardless of which of the switchable path is opened or closed.

A radio-frequency module includes a multilayer substrate, an input switch, an output switch, and filters. A switch IC is disposed on a main surface of the multilayer substrate. The input switch is disposed in the switch IC and includes a first input terminal and first output terminals. The output switch is disposed in the switch IC and includes second input terminals and a second output terminal. The filters are disposed outside the switch IC and are connected to the first output terminals and the second input terminals. In a plan view of the multilayer substrate, the first input terminal and the first output terminals are disposed close to a first side of an exterior of the switch IC, and the second input terminals and the second output terminal are disposed close to a second side different from the first side of the exterior of the switch IC.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

An apparatus is disclosed that includes a frequency multiplexer circuit coupled to an input node and configured to receive an input signal via the input node. The frequency multiplexer circuit comprises a first filter circuit, a second filter circuit, and a third filter circuit. The apparatus also includes a switching circuit that is configurable to couple at least two of a first output of the first filter circuit, a second output of the second filter circuit, or a third output of the third filter circuit to a single output port.