A band-pass filter includes a first inductor and a second inductor electromagnetically coupled to each other, a first ground terminal electrically connected to the first inductor, a second ground terminal electrically connected to the second inductor, and a stack for integrating the first inductor, the second inductor, the first ground terminal, and the second ground terminal. The first ground terminal and the second ground terminal are each connected to a ground and are not electrically connected to each other in the stack.

A programmable filter includes a first programmable filter instance comprising a first adjustable active inductance capacitively coupled to a signal receive path, the capacitive coupling comprising at least one adjustable capacitance, the adjustable active inductance and the at least one adjustable capacitance configurable to provide a filter response at a first selected frequency, and a second programmable filter instance comprising a second adjustable active inductance capacitively coupled to the signal receive path, the capacitive coupling comprising at least one adjustable capacitance, the second adjustable active inductance and the at least one adjustable capacitance configurable to provide a filter response at a second selected frequency.

A tunable probe includes a first resonator, a second resonator spaced from the first resonator, and a cross-couple extending from the first resonator to the second resonator. The cross-couple includes a first substrate and a second substrate disposed between the first and second resonator to create a capacitance between the first and second resonators. The cross-couple further includes a wire connecting the first and second substrates and a dielectric surrounding the wire.

Transmission-line filtering with enhanced frequency response is disclosed. In an example aspect, an apparatus includes a transmission-line filter to enhance a frequency response of a filtering operation. The transmission-line filter includes an input port, an output port, and multiple transmission-line base units. The multiple transmission-line base units are disposed between the input port and the output port and are coupled to the input port and the output port. Each of the multiple transmission-line base units includes a respective transmission line of multiple transmission lines. At least one transmission-line base unit of the multiple transmission-line base units includes a multi-resonant circuit.

Techniques are disclosed for forming tunable capacitors including multiple two-dimensional electron gas (2DEG) and three-dimensional electron gas (3DEG) structures for use in tunable radio frequency (RF) filters. In some cases, the tunable capacitors include a stack of group III material-nitride (III-N) compound layers that utilize polarization doping to form the 2DEG and 3DEG structures. In some instances, the structures may be capable of achieving at least three capacitance values, enabling the devices to be tunable. In some cases, the tunable capacitor devices employing the multi-2DEG and 3DEG structures may be a metal-oxide-semiconductor capacitor (MOSCAP) or a Schottky diode, for example. In some cases, the use of tunable RF filters employing the multi-2DEG and 3DEG III-N tunable capacitor devices described herein can significantly reduce the number of filters in an RF front end, resulting in a smaller physical footprint and reduced bill of materials cost.

Techniques are disclosed for forming tunable capacitors including multiple two-dimensional electron gas (2DEG) and three-dimensional electron gas (3DEG) structures for use in tunable radio frequency (RF) filters. In some cases, the tunable capacitors include a stack of group III material-nitride (III-N) compound layers that utilize polarization doping to form the 2DEG and 3DEG structures. In some instances, the structures may be capable of achieving at least three capacitance values, enabling the devices to be tunable. In some cases, the tunable capacitor devices employing the multi-2DEG and 3DEG structures may be a metal-oxide-semiconductor capacitor (MOSCAP) or a Schottky diode, for example. In some cases, the use of tunable RF filters employing the multi-2DEG and 3DEG III-N tunable capacitor devices described herein can significantly reduce the number of filters in an RF front end, resulting in a smaller physical footprint and reduced bill of materials cost.

Transmission-line filtering with enhanced frequency response is disclosed. In an example aspect, an apparatus includes a transmission-line filter to enhance a frequency response of a filtering operation. The transmission-line filter includes an input port, an output port, and multiple transmission-line base units. The multiple transmission-line base units are disposed between the input port and the output port and are coupled to the input port and the output port. Each of the multiple transmission-line base units includes a respective transmission line of multiple transmission lines. At least one transmission-line base unit of the multiple transmission-line base units includes a multi-resonant circuit.

A tunable probe includes a first resonator, a second resonator spaced from the first resonator, and a cross-couple extending from the first resonator to the second resonator. The cross-couple includes a first substrate and a second substrate disposed between the first and second resonator to create a capacitance between the first and second resonators. The cross-couple further includes a wire connecting the first and second substrates and a dielectric surrounding the wire.

RF communications circuitry includes an RF filter structure, which includes a group of resonators, a group of cross-coupling capacitive structures, and a group of egress/ingress capacitive structures, is disclosed. Each of the group of cross-coupling capacitive structures is coupled between two of the group of resonators. A first portion of the group of egress/ingress capacitive structures is coupled between a first connection node and the group of resonators. A second portion of the group of egress/ingress capacitive structures is coupled between a second connection node and the group of resonators.

A band-pass filter includes a first inductor and a second inductor electromagnetically coupled to each other, a first ground terminal electrically connected to the first inductor, a second ground terminal electrically connected to the second inductor, and a stack for integrating the first inductor, the second inductor, the first ground terminal, and the second ground terminal. The first ground terminal and the second ground terminal are each connected to a ground and are not electrically connected to each other in the stack.