Abstract: A horn antenna comprises an electrically conductive shell having an inner surface, a cavity formed in the shell, an aperture defined at one end of the cavity, a throat section coupled to the electrically conductive shell in communication with another end of the cavity opposite the aperture, and a spatially and frequency dependent radio frequency (RF) attenuator disposed within the cavity, such that an attenuation of RF energy propagating through the cavity between the throat section and the aperture more rapidly increases in an outward direction towards the inner surface of the electrically conductive shell as the frequency of the RF energy increases.

Abstract: A structure for performing socket power calibration comprises a plurality of socket ports on a load board electrically coupled to a plurality of traces on a first end of a flexible printed circuit board, wherein the plurality of traces are configured to allow traversal of an electrical signal from the plurality of socket ports to a waveguide. The structure further comprises the plurality of traces, wherein the traces are operable to terminate on a second end of the flexible printed circuit board into a plurality of patch antennas, wherein the plurality of patch antennas is adapted to radiate the electrical signal into the waveguide. Finally, the structure also comprises a power sensor electrically coupled to the waveguide, wherein the waveguide is configured to communicate the electrical signal from the waveguide to the power sensor.

Abstract: A hollow conductor system is described which comprises at least two hollow conductor bundles and at least two connecting members. Each hollow conductor bundle comprises at least two hollow conductors separated by each other via a common intermediate wall. Each connecting member connects one hollow conductor of one hollow conductor bundle with a corresponding hollow conductor of the other hollow conductor bundle such that a void is provided between the connecting member and the adjacent connecting member and/or an adjacent hollow conductor. Further, a method for assembling a hollow conductor system is described.

Abstract: A lens-enhanced phased array antenna panel includes a phased array antenna panel and at least one lens situated over the phased array antenna panel. The phased array antenna panel has a plurality of antennas arranged in a plurality of antenna segments. Each lens corresponds to at least one of the antenna segments. Each lens is configured to increase a gain of its corresponding antenna segment. Each lens increases a total gain of the phased array antenna panel. Additionally, each lens can provide an angular offset to direct a radio frequency (RF) beam onto its corresponding antenna segment.

Abstract: A load accumulator for a cellular base station antenna includes a plurality of input terminals configured to receive a plurality of input voltages, a plurality of output terminals configured to be coupled to a respective plurality of tower top equipment and configured to supply output voltages to the tower top equipment, a plurality of switches coupled to respective ones of the plurality of input terminals and the plurality of output terminals; a voltage sensor coupled to at least one input terminal of the plurality of input terminals and configured to sense a level of one of the plurality of input voltages received at the at least one input terminal, a supplemental input terminal configured to receive a supplemental voltage, and a control logic coupled to the voltage sensor and to the plurality of switches and configured to detect that the supply voltage supplied to the at least one input terminal has fallen below a threshold voltage, and in response to detecting that the supply voltage supplied to the at le

Abstract: An RF frequency window comprises a dielectric disc, a main metal skirt brazed all the way around the periphery of the dielectric disc and a surrounding prestressing ring in contact with the main metal skirt around the periphery of the dielectric disc and applying, in the rest state, over the whole of the periphery of the dielectric disc, a radial compressive stress directed towards the center of the dielectric disc, the prestressing ring comprising a set of at least one cooling channel in the longitudinal direction of the prestressing ring.

Abstract: Lower-limit frequency reflection characteristics of a horn antenna are improved even though element spacing, of less than or equal to one wavelength, is a spacing at which grating lobes do not occur in an antenna radiation pattern. The horn antenna includes a horn antenna and a conductor grid that divides an aperture A of the horn antenna in a grid pattern and that electrically connects to an inner surface of the horn antenna at the aperture A of the horn antenna. Width of the conductor grid in a direction orthogonal to a horn antenna aperture plane differs from electrical length of the path of the horn antenna of the conductor grid portion at the frequency of power supplied to the horn antenna.

Abstract: An apparatus includes a waveguide. The waveguide includes a waveguide wall having a shape associated with a dominant propagation mode. The waveguide includes a first dielectric material having a cross-sectional area that varies along a length of a portion of the waveguide.

Abstract: An antenna device of the present disclosure includes: a dielectric layer; first and second conductor layers provided on both surfaces, respectively, of the dielectric layer; first and second antenna elements provided in the first conductor layer; a grounded conductor provided in the second conductor layer; and an EBG structure provided between the first and second antenna elements, wherein the EBG structure includes a first EBG portion provided in the first conductor layer, the first EBG portion including a plurality of first patch conductors electromagnetically coupled to the grounded conductor, and a second EBG portion provided in the second conductor layer, the second EBG portion including a plurality of second patch conductors electromagnetically coupled to the grounded conductor.

Abstract: A method for fabricating and installing an artificial impedance surface antenna (AISA) includes locating a substantially flat surface having a line of sight to a satellite or satellites of interest, determining an angle ?o between a normal to the substantially flat surface and a direction to the satellite or satellites of interest, selecting an antenna superstrate from a pre-fabbed stock of antenna superstrates, the selected antenna superstrate configured for having a peak radiation within two (2) degrees of the angle ?o, laminating the selected antenna superstrate to an antenna substrate to form the AISA, and mounting the AISA on the substantially flat surface.

Abstract: A radar antenna assembly suitable to mount atop a vehicle as part of a radar system for the vehicle includes a horizontal array and a vertical array. The horizontal array is configured to preferentially detect objects in a forward area and a rearward area about the vehicle. The vertical array is configured to preferentially detect objects in a leftward area and a rightward area about the vehicle. The horizontal array and the vertical array cooperate to detect an object in a panoramic area that surrounds the vehicle.

Abstract: A radio frequency transmission arrangement comprises a ground plate having an aperture comprising a slot with an elongate cross-section and substantially parallel sides, and a first and second transmission line. The thickness of the ground plate is greater than a width of the slot. The first transmission line comprises a first elongate conductor on a first side of the ground plate and has an end terminated with a first termination stub. The second transmission line comprises a second elongate conductor on the opposite side of the ground plate and has an end terminated with a second termination stub. The first transmission line is arranged to cross the slot at a point adjacent to the first termination stub, and the second transmission line is arranged to cross the slot at a point adjacent to the second termination stub.

Abstract: The disclosed embodiments include methods and systems for distributing a broadband wireless signal in a building. The disclosed methods and systems feature a wireless broadband transmitter associated with multiple base antennas, where the base antennas are inserted into one or more ducts of the ventilation system of the building. Communication between the transmitter and receivers within the building may be optimized by selecting, modifying or controlling a configuration parameter of at least one of the multiple base antennas to enhance distribution of the wireless broadband signal within the ducts of the ventilation system and between the transmitter and device receivers.

Abstract: The present invention discloses a Cassegrain satellite television antenna comprising a metamaterial plate. The metamaterial plate comprises a core layer. The core layer comprises core sublayers. Each core sublayer comprises a circular area and a plurality of annuli distributed around the circular area. According to the Cassegrain satellite television antenna of the present invention, the traditional parabolic antenna is replaced with a sheet-like metamaterial plate which is easier to process and has a lower cost. In addition, the present invention also provides a satellite television receiving system equipped with the above-mentioned Cassegrain satellite television antenna.

Abstract: In a microwave heating device of the present invention, a heating-chamber input portion is adapted to direct, to a heating chamber, microwaves having propagated through a waveguide tube and having passed through the positions where microwave radiating portions are formed, thereby realizing a state where progressive waves are dominant among the microwaves propagating through the waveguide tube, so that the microwave radiating portions are caused to radiate, to the inside of the heating chamber, microwaves based on the progressive waves propagating through the waveguide tube. This enables uniformly heating an object to be heated, without using a rotational mechanism.

Abstract: Described herein are devices, systems, and methods for wireless power transfer utilizing a midfield source and implant. In one variation, a midfield source may be realized by a patterned metal plate composed of one of more subwavelength structures. These midfield sources may manipulate evanescent fields outside a material (e.g., tissue) to excite and control propagating fields inside the material (e.g., tissue) and thereby generate spatially confined and adaptive energy transport in the material (e.g., tissue). The energy may be received by an implanted device, which may be configured for one or more functions such as stimulation, sensing, or drug delivery.

Abstract: Various exemplary embodiments relate to an antenna feed configured to receive a signal having a wavelength. They antenna feed may include a cylindrical body and four pin groups. Each pin group may include two pins in close proximity extending across the center of the cylindrical body. One of the two pins may be rotated approximately 22.5° from the angle of the other pin. Each pin group may be spaced approximately one quarter of a wavelength away from each other, and may be rotated approximately 22.5° from the angle of the previous pin group.

Abstract: A board connection structure includes an opening, which is formed at a perimeter of a waveguide in a first board, and an opening, which is formed at a perimeter of a waveguide in a second board. The openings are connected to each other. The first board and the second board are connected with an insulation film disposed therebetween. The insulation film has a thickness of 60% or less of a waveguide width that determines a propagation mode in at least one of the waveguide in the first board and the waveguide in the second board.

Abstract: Provided is an input/output structure for a dielectric waveguide, comprising a rectangular-parallelepiped-shaped dielectric block, a plate-shaped dielectric plate, and a feeder line comprising a line-shaped electrically conductive foil sandwiched between the dielectric block and the dielectric plate.

Abstract: An artificial impedance surface for rotating a surface wave on the artificial surface about a point along a circumferential path relative to said point in a phase preserving manner along said circumferential path. A method of guiding a transverse electric or transverse magnetic surface wave bound to an artificial impedance surface along a non-linear path comprising: smoothly rotating a principal axis of a surface tensor impedance matrix of the artificial impedance surface as a function of space, so the a propagation wavevector of the transverse electric or transverse magnetic surface wave rotates along with it, remaining aligned with the direction of the principal axis; and tailoring a surface wavenumber in a propagation direction of the non-linear path in such a way as to maintain a constant-phase for a wavefront of the transverse electric or transverse magnetic surface wave.

Abstract: Electromagnetic slow wave structures (SWS) comprised of arrays of conductive obstacles are formed inside conductive parallel-plate waveguides These SWS may be formed using, for example, MEMS manufacturing processes at the wafer level on substrates including ceramic and silicon. An effective relative permittivity in the range of 15 to 40 may be obtained at millimeterwave frequencies. The SWS can be made absorptive by incorporating resistive losses in a plate of the PPW. Applications of these slow wave structures include delay lines and bootlace lens beamformers for microwave and millimeterwave antenna systems.

Abstract: An isothermal terminator system is provided. The isothermal terminator includes a waveguide formed to define a propagation channel through which electro-magnetic (EM) radiation is directed and a terminator including a body having an exterior surface and an interior surface opposite the exterior surface. The terminator is disposed in the propagation channel such that the EM radiation is incident on the exterior surface to raise a temperature of the body. The body is substantially isothermal with the EM radiation incident on the exterior surface.

Abstract: This topic is related to a waveguide propagation apparatus, converting microstrip propagation to waveguide propagation, providing hermeticity on the mounting area, eliminating the cabling component causing degradation on the overall performance, involving at least a microwave module (2), and comprising a combination of a base part (3) and a cover part (4).

Abstract: In a gap-mode waveguide embodiment, an interior gap in a tubular waveguide principally condenses a dominant gap mode near the interior gap, and an absorber dissipates electromagnetic energy away from the gap mode. In this manner, the gap mode may dissipate relatively little power in the absorber compared to other modes and propagate with lesser attenuation than all other modes. A gap mode launched into a gap-mode waveguide may provide for low-loss, low-dispersion propagation of signals over a bandwidth including a multimode range of the waveguide. Gap-mode waveguide embodiments of various forms may be used to build guided-wave circuits covering broad bandwidths extending to terahertz frequencies.

Abstract: A waveguide coupler comprising: a first coupling portion arranged to couple with a first waveguide and a second coupling portion arranged to couple with a second waveguide so as to connect the first waveguide and the second waveguide together; wherein arranged between the first and second coupling portions is a wave modulation portion arranged to modulate wave signals transferred between the first waveguide and the second waveguide.

Abstract: An object of the present invention is to provide an interface apparatus which can suppress leakage of electromagnetic waves and supply electromagnetic waves efficiently without limiting applications or mounting positions. An interface apparatus (200) is provided that supplies electromagnetic waves to a sheet-shaped electromagnetic wave transmission medium for propagating electromagnetic waves and includes a first conductor surface, a second conductor surface disposed in an opposed state to and substantially parallel with the first conductor surface, electromagnetic wave supplying means (230) configured to supply electromagnetic waves to a gap between the first and second conductor surfaces, a first structure (240), and a second structure (250).

Abstract: Various embodiments provide for waveguide assemblies which may be utilized in wireless communication systems. Various embodiments may allow for waveguide assemblies to be assembled using tools and methodologies that are simpler than the conventional alternatives. Some embodiments provide for a waveguide assembly that comprises a straight tubular portion configured to be shortened, using simple techniques and tools, in order to fit into a waveguide assembly. For instance, for some embodiments, the waveguide assembly may be configured such that the straight portion can be shortened, at a cross section of the portion, using a basic cutting tool, such a hacksaw. In some embodiments, the straight portion may be further configured such that regardless of whether the straight tubular portion is shortened, the waveguide assembly remains capable of coupling to flanges, which facilitate coupling the straight tubular portion to connectable assemblies, such as other waveguide assemblies, radio equipment, or antennas.

Abstract: The design and use of a simplified, highly efficient, waveguide-based wireless distribution system are provided. A low-loss waveguide is used to transport wireless signals from a signal source or sources to one or more receiver locations. One or more adjustable signal coupling devices partially insert into the waveguide at predetermined locations along the length of the system to provide variable, controlled extraction of one or more wireless signals. Low-loss impedance matching circuitry is provided between the waveguide coupling devices and output connectors to maintain high system efficiency and the capability of supplying signals of high strength and quality to a large number of receivers in a wide wireless coverage area via a plurality of signal radiators. Some embodiments of the system are adaptable for wireless distribution service in HVAC plenum spaces while others disclose the combined functions of fire extinguishing and waveguide wireless distribution.

Abstract: An ultrathin, low cost, beamformer with excellent RF performance and robust coaxial connections is disclosed. The beamformer includes a dielectric substrate sheet with a beamformer circuit, a preform sheet adjacent to the substrate sheet, and a conductive backing plate sandwiching the preform as well as an RF absorber. The beamformer also includes robust input and output coaxial connections in which the heads of the coaxial input and output pins are captured between the conductive backing plate and the substrate sheet and ground shrouds are attached to the dielectric substrate sheet.

Abstract: [Technical Problem] In a dielectric waveguide input/output structure for performing conversion from a dielectric waveguide through a microstrip to a coaxial line, the conversion is performed once to the microstrip line, and then further to the coaxial line, resulting in a greater loss. Thus, there has been a problem that degradation in performance is unavoidable. Further, the microstrip is required to have a certain level or more of length so as to prevent reduction in size of the printed circuit board. This has been an impediment to downsizing of the input/output structure. [Solution to the Problem] Provided is an input/output structure for a dielectric waveguide, comprising a rectangular-parallelepiped-shaped dielectric block, a plate-shaped dielectric plate, and a feeder line comprising a line-shaped electrically conductive foil sandwiched between the dielectric block and the dielectric plate.

Abstract: A horn antenna is formed within a multilayer substrate and has a generally trapezoidal shaped top plate and bottom plate formed in different layers of the multilayer substrate. A set of densely spaced vias form two sidewalls of the horn antenna by coupling adjacent edges of the top plate and the bottom plate. The horn antenna has a narrow input end and a wider flare end. A microstrip line is coupled to the top plate and a ground plane element is coupled to the bottom plate at the input end of the horn antenna.

Abstract: Disclosed are various embodiments for transmitting energy conveyed in the form of a guided surface-waveguide mode along the surface of a terrestrial medium by exciting a polyphase waveguide probe.

Abstract: Certain exemplary embodiments can provide a rectangular waveguide and backshort adapted for using/studying millimeter and/or submillimeter waves. Exemplary sliding shorts can exhibit relatively low loss, relatively smooth phase variation with frequency and movement, and/or relatively good repeatability. Certain exemplary embodiments can resist transmission of power by reflecting substantially all power from an incident signal.

Abstract: A microwave device having a narrow gap between two parallel surfaces of conducting material by using a texture or multilayer structure on one of the surfaces. The fields are mainly present inside the gap, and not in the texture or layer structure itself, so the losses are small. The microwave device further comprises one or more conducting elements, such as a metal ridge or a groove in one of the two surfaces, or a metal strip located in a multilayer structure between the two surfaces. The waves propagate along the conducting elements. At least one of the surfaces is provided with means to prohibit the waves from propagating in other directions between them than along the ridge, groove or strip. At very high frequency the gap waveguides and gap lines may be realized inside an IC package or inside the chip itself.

Abstract: A heat insulating transmission line includes a first waveguide with a first aperture end, a second waveguide with a second aperture end, and a reflector. The second waveguide is arranged coaxially with the first waveguide. The second aperture end faces the first aperture end through an air gap. The reflector is provided outside the air gap, and controls radiation power from the air gap. In addition, the reflector is substantially parallel to a portion of a virtual plane connecting an inner wall of the first aperture end of the first waveguide and an inner wall of the second aperture end of the second waveguide. When a mean frequency of a signal transmitting through the heat insulating transmission line is expressed as ?, a distance between the virtual surface and the reflector is not less than N×?/2?0.05? and not more than N×?/2+0.2? (N is a positive integer).

Abstract: The present invention relates to a tunable microwave arrangement (100) comprising a waveguide arrangement and tuning elements comprising a number of varactors for tuning an electromagnetic signal input to the waveguide arrangement. It comprises a substrate (1), a layered structure (20) comprising at least two conducting layers (2,3) and at least one dielectric layer (4) which are arranged in an alternating manner. The layered structure is arranged on the substrate (1) such that a first of said conducting layers (2) is closest to the substrate (1). It also comprises at least one surface mounted waveguide (5), a second of the conducting layers (3), most distant from the substrate, being adapted to form a wall of the surface mounted waveguide (5), which wall incorporates said tuning elements which are arranged to enable control of surface currents generated in said wall, hence loading the waveguide (5) with a tunable, controllable impedance.

Abstract: An apparatus includes: an electromagnetic waveguide and an iris structure providing an iris in the electromagnetic waveguide. The iris structure defines an iris hole. The apparatus further includes an electric field rotation arrangement configured to establish a 2N-pole electric field around a circumference of the iris hole, wherein N is an integer which is at least two. The electric field rotation arrangement may include at least four iris slots, each in communication with the iris hole, wherein a first one of the iris slots is further in disposed at a first side of the iris hole and a second one of the iris slots is disposed at a second side of the iris hole which is opposite the first side.

Abstract: Dielectric waveguide comprising a circular input/output electrode on its bottom surface and surrounded by an exposed dielectric portion thereof around which a conductor film is disposed. A short stub crosses through the exposed dielectric portion to couple the electrode and film together. The printed circuit board has a front surface formed with a generally-circular island-shaped electrode surrounded by a front surface-side ground pattern in a spaced-apart relation thereto, and a back surface formed with a strip line surrounded by a back surface-side ground pattern in spaced-apart relation thereto. An approximate center of the island-shaped electrode and one end of the strip line are coupled together, and the front surface-side ground pattern and the back surface-side pattern are coupled together. The input/output electrode of the dielectric waveguide and the island-shaped electrode of the printed circuit board are coupled together.

Abstract: A waveguide member assembly includes a side plate and a waveguide member. The side plate defines an opening. The waveguide member includes a main body molded integrally by plastic. The main body includes a core portion and a mounting plate extending out from edges of a side of the core portion. The core portion includes a number of waveguide tubes aligning with the opening. A metal layer is coated on an outer side of the main body and inner sidewalls of the waveguide tubes. The mounting plate is fastened to the side plate.

Abstract: A waveguide for transmission of data signals therealong. Data signals are typically received from and/or transmitted to a remote location and subsequently passed to or emitted from the apparatus which allows the data to be processed. The waveguide includes a channel which has a cross-sectional shape, the angular orientation of which is changed at least one point along the length of the same so as to provide a waveguide which is less sensitive to interferences. The waveguide, in one embodiment, can also include recessed portions and/or ridges along the length of the channel which ensures that the waveguide can be formed in a more reliable and controlled manner.

Abstract: An electronic system. The electronic system includes a waveguide structure having a first waveguide-coupling point and a second waveguide-coupling point and an active electronic circuit having a first circuit-coupling point and a second circuit-coupling point. The second waveguide-coupling point is coupled to the first circuit-coupling point; the system is capable of receiving an input signal at the first waveguide-coupling point and transmitting an output signal at the second circuit-coupling point and/or receiving the input signal at the second circuit-coupling point and transmitting the output signal at the first waveguide-coupling point; the input signal and the output signal have frequencies in a terahertz frequency range; and the system is fabricated as a monolithic integrated structure having the waveguide structure fabricated by micromachining and the circuit fabricated monolithically.

Abstract: A substrate integrated waveguide (10) comprises a top conductive layer (14) and a bottom conductive layer (15) provided on either sides a substrate (11). At least one wall (12, 13) of conductive material is provided in the substrate (11) to define, together with the top and bottom layers (14, 15), the waveguide. The at least one wall (12, 13) comprise a multitude of thin conductive wires densely arranged close to each other in the substrate (11) and having respective short ends connected to the top and bottom layers (14, 15). The high number of wires per surface unit in the wall (12, 13) effectively prevent significant amount of power leakage through the wall (12, 13) during operation of the substrate integrated waveguide (10).

Abstract: A waveguide component encapsulation device may include a housing having first and second surfaces, the housing defining a channel extending through the first and second surfaces, a micromachined waveguide component configured to be positioned in the channel, the waveguide component having first and second ends extending outside the channel and beyond the first and second surfaces of the housing by a finite length, and a pair of spacing members configured to align and stabilize the waveguide component within the channel.

Abstract: Provided is an electronic device including a high-frequency signal waveguide configured to transmit a high-frequency signal in a housing. An addition unit to which a communication device is able to be added is provided in the high-frequency signal waveguide. When a second module having a communication function is added to the addition unit and coupled to the high-frequency signal waveguide, data transmission is possible between the first module and the second module via the high-frequency signal waveguide.

Abstract: A compact thermoelastic actuator includes at least two identical force pieces and a securing piece, the securing piece having a coefficient of thermal expansion less than the coefficient of thermal expansion of the force pieces. The force pieces are mounted head-to-tail one beside the other parallel to a longitudinal axis Y and are linearly offset relative to one another, along the longitudinal axis Y. The securing piece has two ends respectively linked to external ends of each force piece and internal ends of each force piece are positioned under a median region of the securing piece. The actuator and device is applicable to waveguides of multiplexers incorporated in space equipment for satellites.

Abstract: A waveguide includes a waveguide body which is hollow inside and made from a shape-retentive material, and a conductive inner coating layer which is electrically conductive and provided on an inner surface of the waveguide body. The waveguide uses an inner space of the conductive inner coating layer as a transmission path to transmit electromagnetic waves as signals. Two electric wires provided along the outer surface of the waveguide body serve respectively as a power line and a ground line to transmit electric power.

Abstract: A heat insulating transmission line includes a first waveguide with a first aperture end, a second waveguide with a second aperture end, and a reflector. The second waveguide is arranged coaxially with the first waveguide. The second aperture end faces the first aperture end through an air gap. The reflector is provided outside the air gap, and controls radiation power from the air gap. In addition, the reflector is substantially parallel to a portion of a virtual plane connecting an inner wall of the first aperture end of the first waveguide and an inner wall of the second aperture end of the second waveguide. When a mean frequency of a signal transmitting through the heat insulating transmission line is expressed as ?, a distance between the virtual surface and the reflector is not less than N×?/2?0.05? and not more than N×?/2+0.2? (N is a positive integer).

Abstract: A co-axial microwave bolometer architecture is disclosed that uses thick-film processes to construct very small thermistors on a substrate that is selected for low heat transfer. Thermal isolation is further enhanced by making the planar electrodes from a metal with lower heat transfer than typical electrical metals. Furthermore, a resistor with very strong temperature coefficient (thermistor), is arranged such that connecting metal paths are arranged axially, and as generally flat, thin, planar conductors. Additionally, the substrate of the thermistor is selected to have very low conductivity of heat, so the thermistor element itself is well isolated thermally from its surroundings.

Abstract: A radial power combination system is provided. The system comprises a radial divider comprising ports in the form of rectangular waveguides on the periphery, a radial combiner superposed on the radial divider, comprising ports in the form of rectangular waveguides on the periphery, a first, input transition transmitting a first signal to the center of the radial divider, a second, output transition capturing the first signal amplified to the output of the radial combiner, at least two amplifying channels comprising a third, input transition capable of interacting with the guides, a fourth, output transition capable of interacting with the guides and at least one amplifier, and means for adjusting the positioning of the amplifying channels, thus making it possible to adjust the phase shift of the various channels.

Abstract: A right circular cylindrical body of an isotropic dielectric such as a cross-linked styrene copolymer, has respective pluralities of mutually parallel grooves formed in its axial end faces, spaced apart by an intermediate portion whose dimension c is a half wavelength. The axial lengths a, b of the grooves are such that when a wave passes through the body, a quarter wavelength phase difference is produced between a component of a wave having its E-vector parallel to the grooves and a component of the wave having its E-vector orthogonal to the grooves. Alternatively the plate may consist of two or more discrete bodies whose grooves are dimensioned to produce a total differential phase shift of one quarter wavelength.