An optical module may include an optical subassembly having a receptacle. The receptacle may have a first diameter. The optical module may include a housing having a circular opening for receiving the receptacle. The circular opening may have a second diameter. The first diameter and the second diameter may be sized to reduce electromagnetic interference at a cut-off frequency from the optical module. The cut-off frequency may be defined by a data rate of at least one component of the optical module.

The present invention provides a common-mode signal absorber, which comprises an impedance-matching network and a common-mode signal reflection circuit. A differential-mode signal is inputted into input ends of the impedance-matching network, and outputted from output ends of the common-mode signal reflection circuit. When a common-mode signal is inputted into the common-mode signal absorber, the common-mode signal reflection circuit is for reflecting the common-mode signal within a specific frequency band. Afterward, the reflection of the common-mode signal within the specific frequency band will be absorbed by an impedance element of the impedance-matching network. Thus, the common-mode signal within the specific frequency band may be absorbed by the impedance-matching network so as to avoid to interfere signals transmitted on a communication system.

The present invention provides a common-mode signal absorber, which comprises an impedance-matching network and a common-mode signal reflection circuit. A differential-mode signal is inputted into input ends of the impedance-matching network, and outputted from output ends of the common-mode signal reflection circuit. When a common-mode signal is inputted into the common-mode signal absorber, the common-mode signal reflection circuit is for reflecting the common-mode signal within a specific frequency band. Afterward, the reflection of the common-mode signal within the specific frequency band will be absorbed by an impedance element of the impedance-matching network. Thus, the common-mode signal within the specific frequency band may be absorbed by the impedance-matching network so as to avoid to interfere signals transmitted on a communication system.

A septum polarizer according to one embodiment can comprise a waveguide body and a stair-shaped septum, which is arranged in the longitudinal direction inside the waveguide body and divides the waveguide body into two parts, and has stepped parts of different heights so that a higher order mode can be reduced in a preset frequency band. In addition, a septum polarizer according to one embodiment can comprise: a waveguide body having a polygonal cross-section; a stair-shaped septum, which is arranged in the longitudinal direction inside the waveguide body and divides the waveguide body into two parts; and a pleated part arranged on the outer surface of the waveguide body, and

A waveguide includes: a substrate; a first ground wire; a second ground wire; a signal wire; and a compensation structure. The first ground wire, the second ground wire, and the signal wire are disposed on the substrate at intervals, and the signal wire is located between the first ground wire and the second ground wire. The compensation structure is configured to contact at least one of the substrate, the first ground wire, the second ground wire, or the signal wire; and the compensation structure comprises a superconducting material.

It is disclosed a waveguide array antenna for satellite communications. The antenna is configured to transmit and/or receive a first polarization signal and a second polarization signal, the second polarization being orthogonal to the first polarization, and comprises an array of unit cells, each comprising a radiating element. The antenna comprises: a grid configured to divide each radiating element into sub-elements having an inter-element distance lower than or equal to the wavelength at a highest frequency of operation of the antenna; and an electromagnetic band gap layer configured to support the grid above the radiating elements. The grid comprises a number of grid unit portions, and the electromagnetic band gap layer consists of a number of pins protruding from the walls of each grid unit portion.

Systems and methods for mode suppression in a cavity are provided. In certain implementations, an apparatus comprises a cavity for propagating electromagnetic signals therein, wherein the electromagnetic signals propagate multiple times through the cavity; and an absorbing material applied to a first side of the cavity, wherein the absorbing material absorbs the electromagnetic signals. Further, an apparatus includes at least one transmitting antenna configured to couple electromagnetic energy into the cavity; and at least one receiving antenna configured to couple electromagnetic energy from the cavity.

Systems and methods for mode suppression in a cavity are provided. In certain implementations, an apparatus comprises a cavity for propagating electromagnetic signals therein, wherein the electromagnetic signals propagate multiple times through the cavity; and an absorbing material applied to a first side of the cavity, wherein the absorbing material absorbs the electromagnetic signals. Further, an apparatus includes at least one transmitting antenna configured to couple electromagnetic energy into the cavity; and at least one receiving antenna configured to couple electromagnetic energy from the cavity.

The present invention provides a common-mode signal absorber, which comprises an impedance-matching network and a common-mode signal reflection circuit. A differential-mode signal is inputted into input ends of the impedance-matching network, and outputted from output ends of the common-mode signal reflection circuit. When a common-mode signal is inputted into the common-mode signal absorber, the common-mode signal reflection circuit is for reflecting the common-mode signal within a specific frequency band. Afterward, the reflection of the common-mode signal within the specific frequency band will be absorbed by an impedance element of the impedance-matching network. Thus, the common-mode signal within the specific frequency band may be absorbed by the impedance-matching network so as to avoid to interfere signals transmitted on a communication system.

A signal transmission line includes: a first electrical conductor; a second electrical conductor; a dielectric region between the first electrical conductor and the second electrical conductor; and an electrically thin resistive layer disposed within the dielectric region and disposed between the first electrical conductor and the second electrical conductor. A gap exists in the electrically thin resistive layer.