In an embodiment, a microwave circuit (circuit) includes an attenuator configured to attenuate a plurality of frequencies in a microwave signal. In an embodiment, the attenuator comprises a component of a first material, the first material exhibiting superconductivity in a cryogenic temperature range. In an embodiment, the circuit includes a magnet configured to generate a magnetic field at the attenuator, wherein the magnetic field is at least equal to a critical magnetic field strength of the first material. In an embodiment, the critical magnetic field strength causes the first material to become non-superconductive in the cryogenic temperature range.

A directional coupler includes an input connector, an output connector, and at least one tap connector. The directional coupler also includes a primary line connecting the input connector to the output connector and configured to carry an RF signal and an AC signal, and a secondary line connecting the primary line to the at least one tap connector and configured to carry a split off portion of the RF signal. The directional coupler also includes a tapped line circuit which is inhibited from carrying the AC signal. The mainline transformer includes a ferrite element surrounding the primary line and which is split in at least one location to include a gap of non-magnetic material that inhibits saturation of the ferrite element.

A frequency selective limiter (FSL) is provided having a transmission line structure with a tapered width. The FSL includes a magnetic material having first and second opposing surfaces. A first conductor is disposed on the first surface of the magnetic material, where a width of the first conductor decreases from a first end of the FSL to a second end of the FSL along a length of the FSL. Two second conductors are disposed on the second surface of the magnetic material, where a width of a gap between the two second conductors decreases from the first end of the FSL to the second end of the FSL along a length of the FSL. The first conductor and two second conductors form a biplanar waveguide transmission line.

A frequency selective limiter (FSL) is provided having a transmission line structure with a tapered width. The FSL includes a magnetic material having first and second opposing surfaces. A first conductor is disposed on the first surface of the magnetic material, where a width of the first conductor decreases from a first end of the FSL to a second end of the FSL along a length of the FSL. Two second conductors are disposed on the second surface of the magnetic material, where a width of a gap between the two second conductors decreases from the first end of the FSL to the second end of the FSL along a length of the FSL. The first conductor and two second conductors form a biplanar waveguide transmission line.

In an embodiment, a microwave circuit (circuit) includes an attenuator configured to attenuate a plurality of frequencies in a microwave signal. In an embodiment, the attenuator comprises a component of a first material, the first material exhibiting superconductivity in a cryogenic temperature range. In an embodiment, the circuit includes a magnet configured to generate a magnetic field at the attenuator, wherein the magnetic field is at least equal to a critical magnetic field strength of the first material. In an embodiment, the critical magnetic field strength causes the first material to become non-superconductive in the cryogenic temperature range.

In an embodiment, a microwave circuit (circuit) includes an attenuator configured to attenuate a plurality of frequencies in a microwave signal. In an embodiment, the attenuator comprises a component of a first material, the first material exhibiting superconductivity in a cryogenic temperature range. In an embodiment, the circuit includes a magnet configured to generate a magnetic field at the attenuator, wherein the magnetic field is at least equal to a critical magnetic field strength of the first material. In an embodiment, the critical magnetic field strength causes the first material to become non-superconductive in the cryogenic temperature range.

A rectangular waveguide device is provided. The rectangular waveguide device comprising: a first broad wall; a second broad wall parallel to the first broad wall; a first narrow wall perpendicular to and connected to the first broad wall and the second broad wall; a second narrow wall parallel to the first narrow wall and connected to the first broad wall and the second broad wall; and at least one slot in the first broad wall.

A rectangular waveguide device is provided. The rectangular waveguide device comprising: a first broad wall; a second broad wall parallel to the first broad wall; a first narrow wall perpendicular to and connected to the first broad wall and the second broad wall; a second narrow wall parallel to the first narrow wall and connected to the first broad wall and the second broad wall; and at least one slot in the first broad wall.

A frequency selective limiter (FSL) having an input port and an output port can comprise a plurality of vertically stacked transmission line structures. Each of the transmission line structures can be electrically coupled to a transmission line structure disposed directly above it and with a first one of the plurality of vertically stacked transmission line structures having one end corresponding to the FSL input port and a second one of the plurality of vertically stacked transmission line structures having one end corresponding to the FSL output port. Each of the plurality of vertically stacked transmission line structures can comprise a magnetic material having first and second opposing surfaces and one or more conductors disposed on at least one of the surfaces of the magnetic material.

A frequency selective limiter (FSL) having an input port and an output port can comprise a plurality of vertically stacked transmission line structures. Each of the transmission line structures can be electrically coupled to a transmission line structure disposed directly above it and with a first one of the plurality of vertically stacked transmission line structures having one end corresponding to the FSL input port and a second one of the plurality of vertically stacked transmission line structures having one end corresponding to the FSL output port. Each of the plurality of vertically stacked transmission line structures can comprise a magnetic material having first and second opposing surfaces and one or more conductors disposed on at least one of the surfaces of the magnetic material.