Fabrication of superconducting devices that combine or separate direct currents and microwave signals is provided. A method can comprise forming a direct current circuit that supports a direct current, a microwave circuit that supports a microwave signal, and a common circuit that supports the direct current and the microwave signal. The method can also comprise operatively coupling a first end of the direct current circuit and a first end of the microwave circuit to a first end of the common circuit. The direct current circuit can comprise a bandstop circuit and the microwave circuit can comprise a capacitor. Alternatively, the direct current circuit can comprise a bandstop circuit and the microwave circuit can comprise a bandpass circuit. Alternatively, the microwave circuit can comprise a capacitor and the direct current circuit can comprise one or more quarter-wavelength transmission lines.

A radio frequency circuit includes a multilayer substrate, series arm circuits in a first path connecting the input/output terminals (T1 and T2) on the multilayer substrate, a parallel arm circuit in a second path connecting a node on the first path and a ground, a wiring A on the multilayer substrate connected to the input/output terminal (T1) as a part of the first path, a wiring B on the multilayer substrate connected to the input/output terminal (T2) as a part of the first path, and a wiring C on the multilayer substrate as a part of the second path. The parallel arm circuit includes an impedance variable circuit, the wiring A and the wiring B in a layer different from the multilayer substrate. When viewed in a plan view, the wiring C does not overlap with the wiring A and the wiring B.

A common mode filter is disposed on a circuit board. A signal layer of the circuit board has a differential signal wire pair. The common mode filter has a slot structure and a filtering frequency adjusting device. The slot structure is formed on a reference voltage layer of the circuit board, wherein the slot structure surrounds the differential signal wire pair. The filtering frequency adjusting device is disposed on a corner part of the slot structure, wherein the filtering frequency adjusting device includes at least one of at least one capacitor and at least one inductor, and is disposed on the circuit board across the differential signal wire pair.

A band-pass filter includes a first input/output port, a second input/output port, a first high-pass filter, a first low-pass filter, and a first stub resonator. The first stub resonator includes a first distributed constant line. The first low-pass filter is provided between the first input/output port and the first high-pass filter in the circuit configuration. The first distributed constant line has a first end connected to a first path connecting the first input/output port and the first low-pass filter, and a second end closest to a ground in the circuit configuration.

A common mode filter is disposed on a circuit board. A signal layer of the circuit board has a differential signal wire pair. The common mode filter has a slot structure and a filtering frequency adjusting device. The slot structure is formed on a reference voltage layer of the circuit board, wherein the slot structure surrounds the differential signal wire pair. The filtering frequency adjusting device is disposed on a corner part of the slot structure, wherein the filtering frequency adjusting device includes at least one of at least one capacitor and at least one inductor, and is disposed on the circuit board across the differential signal wire pair.

A noise filter may include: a first conductive line extending between an input and an output terminal portion, wherein the first conductive line includes an input-side conductive line extending between the input terminal portion and a branch portion, and an output-side conductive line extending between the output terminal portion and the branch portion; a second conductive line connected to the branch portion of the first conductive line, wherein a capacitor is on the second conductive line; and a magnetic body surrounding at least a part of a circumference of at least a part of the first conductive line, wherein the magnetic body is configured to magnetically couple the input-side and the output-side conductive lines such that at least an equivalent series inductance of the capacitor and a parasitic inductance of the second conductive line are reduced by a mutual inductance between the input-side conductive line and the output-side conductive line.

A superconducting circuit includes a first port and a plurality of second ports; a plurality of filter poles, each filter pole comprising an inductor and a capacitor connected in parallel, between the first port and a second port in the plurality of second ports; an admittance inverter comprising at least one of a coupling capacitor, a coupling inductor, and a Josephson junction, the admittance inverter linking two successive filter poles together. The plurality of filter poles and associated admittance inverters define a plurality of current branches so that, when operating as a demultiplexer, an input electrical current input though the first port is routed to a selected one of the plurality of the plurality of second ports by an application of a first set of magnetic flux biases.

Disclosed herein are methods and circuits that prevent energy that would produce a spurious resonance from lumped, distributed or waveguide circuit elements by using for example a low pass filter with a cut-off below the first spurious resonance frequency and bypassing the energy at frequencies at or above the first spurious resonance frequency through a secondary path. This secondary path is high pass in nature, with a cutoff substantially similar to the low pass filter. The two paths are combined at the common output, using a lowpass matching network.

A Wilkinson power combiner (202) is described that includes: at least one input port (210) coupled to at least one output port (212, 214, 216, 218) by at least two power combining stages. A first power combining stage (204) of the at least two power combining stages is configured as a single-stage first frequency pass circuit and a second power combining stage (206) of the at least two stages is configured as a single-stage second frequency pass circuit, and wherein the first frequency is different to the second frequency.

In a first approach, a reconfigurable radio frequency (RF) filtering module includes a phase-change material (PCM) RF switch bank and an RF filter bank. Each RF filter in the RF filter bank is capable to be engaged and disengaged by a PCM RF switch in the PCM RF switch bank. In a second approach, a tunable RF filter includes PCM RF switches and a capacitor and/or an inductor. Each of the capacitor and/or inductor is capable to be engaged and disengaged by at least one PCM RF switch of the PCM RF switches. In a third approach, an adjustable passive component includes multiple segments and a PCM RF switch. A selectable segment in the multiple segments is capable to be engaged and disengaged by the PCM RF switch. In all approaches, each PCM RF switch includes a PCM and a heating element transverse to the PCM.