Abstract: A mode filter for connecting two electromagnetic waveguides with different cross-sections includes a tubular section (4) with openings at both ends. The cross-sections of the openings match the cross-sections of the two different waveguides, while the interior space (11) of the tubular section (4) transitions from one cross-sectional shape into the other cross-sectional shape. Undesirable modes of the electromagnetic waves which are to be transmitted, are minimized by flat elements (14, 15) protruding radially inwardly into the transition region and extending axially along the tubular section (4). The flat elements (14, 15) are made of a material with a high electrical conductivity. The elements (14, 15) are arranged diametrically opposed from each other and aligned in the same plane and separated by a gap (16). The axial length of the flat elements is short in relation to the length of the tubular section (4).

Abstract: A low profile, low cost receiver/transmitter system includes a planar waveguide-to-microstrip adapter, a dielectric loaded waveguide fed slot array antenna, and a downconverter all formed on a single dielectric substrate made of polytetrafluoroethylene. The waveguide antenna includes a set of slots disposed in a surface thereof to receive/transmit a microwave/millimeter wave signal. The waveguide-to-stripline adapter is connected to the waveguide antenna and includes a taper section attached to a microstrip line. The taper section, which may be linear or may follow some other more complex taper function such as a Chebyshev function, adapts a signal propagating within the waveguide antenna to the microstrip line or vise versa.

Abstract: A radiating element for an antenna incorporating a patch launcher, a bandpass filter and a polarizer all in one waveguide without the need for interconnecting individual components. The waveguide has at least one coaxial input having a patch launcher attached thereto. The inside diameter of the waveguide has a plurality of spaced apart irises that act as a bandpass filter followed by a plurality of spaced apart pins that act as a polarizer.

Abstract: A dual mode horn reflector antenna for providing an antenna pattern having symmetrical beamwidths over a bandwidth of approximately 40%. An input TE.sub.10 rectangular mode signal is provided to the dual mode horn reflector antenna which generates a first TE.sub.11 circular mode signal from the input TE.sub.10 rectangular mode signal. A first TE.sub.10 square mode signal and a first TE.sub.01 square mode signal are generated from the first TE.sub.11 circular mode signal. The first TE.sub.10 square mode signal and the first TE.sub.01 square mode signal are combined generate a resultant signal. The resultant signal is incident upon a reflecting structure which generates an antenna pattern having approximately equivalent beamwidths in perpendicular planes, and reduced sidelobes.

Abstract: A method for designing an aperiodic grating structure for mode conversion and control which is based upon an inverse scattering optimization procedure. In accordance with this method, no predetermined shape or material variation of the grating structure is assumed. A constrained domain of all surfaces and material variations is searched to find an optimum aperiodic conversion surface profile for maximum conversion efficiency into the required output mode(s) or optimum control. Accordingly, the present method results in the design of rough surfaces or non-homogeneous structures for mode conversion and control. Because this method relies on scattering produced by short, forceful field perturbations, it is possible to achieve very small conversion lengths which are much less than one grating period.

Abstract: An electromagnetic wave matching element makes it possible to reduce the cost of a transmission system to a great degree. An electromagnetic wave matching element is adapted to allow electromagnetic wave beams incident from an entrance to be reflected by using plural mirrors to couple these reflected electromagnetic wave beams to an external transmission system through an exit. Mirrors are used that have a shape adapted to receive the plural electromagnetic waves in a beam form and to output electromagnetic wave beams having a predetermined distribution in which the number of the output electromagnetic waves is different from the number of the received electromagnetic waves.

Abstract: A micro-wave mixing circuit produces producing a stable frequency conversion characteristic against a dispersion of output voltage of a local oscillation signal tapped off from a local oscillator. A micro-wave signal fed into a micro-wave signal input can be converted into an intermediate frequency signal of 1 GHz bandwidth where a stable frequency conversion characteristic is maintained against a dispersion of an output voltage of a local oscillation signal, by supplying bias current from a bias supply circuit to an anode of a Schotkky barrier diode responsive to a local oscillation output which is supplied from a local oscillator.

Abstract: A coupling is presented for coupling two electromagnetic hollow conductors (waveguides) with different cross-sectional shapes. The coupling includes steps (S1-S3) arranged sequentially in the axial direction, having an essentially rectangular cross section and rounded corners as well as different clearances. The dimensions of all steps (S1-S3) are purposely designed so that other modes in addition to the basic mode are able to propagate therein. Because of the dimensions of coupling (3), only modes intended to conduct signals propagate in the joined waveguides, while those which are not intended to conduct signals are essentially cancelled by superposition.

Abstract: An outdoor satellite broadcast receiving converter including a waveguide into which a broadcast electric wave enters and in which the broadcast electric wave travels in an axial direction as a first linearly polarized wave and a second linearly polarized wave. A first probe is disposed at a predetermined position and extends perpendicular to the axial direction into the waveguide for detecting the first linearly polarized wave. A substrate is disposed in the waveguide approximately 1/4 wavelength from the first probe and arranged to extend across an open end of the waveguide. A first shorting terminal for reflecting the first linearly polarized wave is formed on a first side of the substrate, and a second probe for detecting the second linearly polarized wave is formed on an opposing second side of the substrate. A metallic case is connected over the open end of the waveguide such that the substrate is positioned between a closed bottom of the metallic case and the first probe.

Abstract: On a terminal end plane of a circular waveguide, metal columnar blocks and a cross shaped branching transforming unit for branching two orthogonal linear polarized waves and transforming from circular TE.sub.11 mode to rectangular TE.sub.10 mode are disposed, and two rectangular waveguides are composed so as to form an angle of 45 degrees to the vertical axis and horizontal axis, that is, symmetrically to the axial center of the circular waveguide, in an electric field direction of the first linear polarized wave and an electric field direction of the second linear polarized wave. In this constitution, the orthogonal polarized wave branching filter of the microwave band for satellite communications can be reduced in size, and moreover the principal components can be formed integrally by an injection molding process.

Abstract: A travelling wave coupler autotracking system 10 controls the pointing of an antenna aboard an orbiting satellite by generating tracking signals covering a wideband frequency. The system 10 comprises a waveguide manifold 22 for exciting circular TE.sub.11 and TM.sub.01 modes covering a wideband frequency range, coupling arm waveguides 24, 26 for propagating signals having a phase velocity of TE.sub.10 mode that is the same as the phase velocity of TM.sub.01 mode, and couplers 30 for transforming microwave energy of the TM.sub.01 mode of the circularly polarized microwave signals into TE.sub.10 modes in the coupling waveguide. The system 10 can further comprise 180.degree.-hybrid 20 for combining the TE.sub.10 modes in the coupling waveguides in phase and for generating one or more error signals at different frequencies.

Abstract: The present invention comprises a microwave mode convert having a cylindrical waveguide input. Attached to the waveguide input is a transition section which gradually changes from the elliptical or cylindrical waveguide input. The output section is also an elliptical waveguide. The output section may also have an elliptical or cylindrical waveguide attached to it. The mode converter of the present invention has input a TM.sub.01 mode microwave energy from a cylindrical waveguide and outputs TE.sub.11 or TEM mode microwave energy which is an elliptical or circular pencil beam of radiation with high directivity.

Abstract: An electron beam generated by an electron gun is oscillated in a cavity resonator and output as a millimeter electromagnetic wave. The output electromagnetic wave is transmitted to a cylindrical mode converter. The inner wall surface of this mode converter has a plurality of sets of ridges and grooves spirally formed at equal pitches so as to gradually change the degree of corrugation in the transmission direction of the electromagnetic wave. The mode converter separates the input electromagnetic wave from the cavity resonator into a plurality of electromagnetic waves having the same power distribution. The output electromagnetic waves from the mode converter are transformed into wave beams by mirror systems and output to the outside of a gyrotron from output windows provided in a one-to-one correspondence with these electromagnetic waves.

Abstract: A microwave antenna comprises a single moded metal waveguide tapering inwardly to a cutoff dimension near the distal end thereof. The antenna also comprises a first solid dielectric waveguide mounted coaxially within the distal end portion of the metal waveguide and tapering outwardly toward the inwardly tapering portion of the metal waveguide. The first dielectric waveguide extends beyond the distal end of the metal waveguide in the axial direction. The antenna also comprises a second dielectric waveguide surrounding the first dielectric waveguide beyond the distal end of the metal waveguide and having a dielectric constant lower than the dielectric constant of the first dielectric waveguide. A distal end portion of the first dielectric waveguide tapers inwardly toward the axis thereof, to launch signals propagating toward the distal end of the first dielectric waveguide into the second dielectric waveguide.

Abstract: A microwave coupler with improved efficiency receives microwave energy in a principal mode TEm,n (m and n being whole numbers and n being not zero) and gives a quasi-optical energy beam. It comprises a mode converter that receives energy in the principal mode and converts a part of it into an auxiliary mode TEp,q (with p and q being whole numbers, q close to one and not zero, p greater than q). The energy in the principal mode and in the auxiliary mode get propagated in a radiator and emerge in the form of the quasi-optical beam by an aperture that coincides with a minimum electrical field resulting from the electrical field of the principal mode and the electrical field of the auxiliary mode. The disclosure has applications notably to the field of gyrotubes.

Abstract: A monopulse comparator receives an incoming RF signal through a multimode antenna and splits it into a first-half signal that corresponds to the incoming RF signal as received by one half of the antenna and a second-half signal that corresponds to the incoming RF signal as received by the other half of the antenna. A folded magic tee selectively separates an unsymmetric mode component signal and a symmetric mode component signal from the first-half signal. In one embodiment, the unsymmetric mode component signal is the TE.sub.2,0 mode and the symmetric mode component signal is the TE.sub.1,0 mode. The energy of the TE.sub.2,0 mode signal is dependent on .DELTA.AZ information of the incoming RF signal relative to the antenna's boresight. The TE.sub.1,0 mode contains the .SIGMA. and .DELTA.EL signals. A second folded magic tee selectively separates the corresponding unsymmetrical and symmetrical mode component signals of the second-half signal. Waveguide-to-microstrip transition circuits transition the TE.sub.

Abstract: A measuring jig which is used to measure characteristics of a device with a nonradiative dielectric waveguide which operates in a microwave band or in a millimeter wave band. The measuring jig has a mount section on which a device with a nonradiative dielectric waveguide is to be mounted, and a converting section which connects the device to an external circuit. The converting section has a couple of parallel conductors, a dielectric strip which is disposed between the conductors and propagates a high-frequency electromagnetic wave in a specified mode, and an end surface which is formed on an end of the conductors so as to be vertical to a traveling direction of the electromagnetic wave propagated in the dielectric strip and on which an end of the dielectric strip is exposed.

Abstract: A stripline to waveguide transition device efficiently and simply converts he TEM stripline mode to the TE.sub.10 rectangular waveguide mode. A stripline is inserted longitudinally, end-to-end, into a waveguide. A conductive strip extends from the conductive strip of the stripline into the waveguide passing between two metallic plates, which separate the waveguide from the stripline terminal end and establish a TE.sub.10 boundary condition. The conductive strip is orthogonally coupled at its distal end to a broad interior wall of the waveguide to provide a transition area supporting both TEM and TE.sub.10 modes.

Abstract: Multiple radio frequency (RF) outlet ports are provided along the side of a slow wave tube to establish a distributed RF output in response to the transmission of an e.sup.- beam through the tube. The tube has a periodically rippled inner surface, and the outlet ports are spaced along the tube by substantially integral numbers of ripple periods. When implemented as a backward wave oscillator, RF power is extracted during a single pass through the tube; a travelling wave tube amplifier implementation is also possible. The separation of the RF extraction from the absorption of the e.sup.- beam at the end of the tube eliminates RF reflections and permits water cooling of the e.sup.- beam absorber. The RF extraction ports are also preferably configured as built-in mode converters from a TM.sub.01 cylindrical tube mode to a TE.sub.10 rectangular extraction mode, with four symmetrically arranged rectangular extraction waveguides at each extraction location combining their energies into a single TE.sub.10 output.

Abstract: A magnetron transition apparatus is provided which permits transmission of a microwave RF signal between a magnetron and an output waveguide. The transition apparatus is connected to the magnetron and receives the RF signal from the magnetron, while maintaining a substantially vacuum environment therein. The transition apparatus further comprises an RF interface between the substantially vacuum environment and a non-vacuum environment within the output waveguide. The microwave RF signal from the magnetron is transmitted through the transition apparatus into the output waveguide. The transition structure comprises an adapter having a first portion of generally circular cross-section and a second portion of generally rectangular cross-section. A conductive loop electrically connected to an anode structure of the magnetron is disposed within the first portion and inductively couples the RF signal from the magnetron into the transition apparatus.

Abstract: The rotor of the joint includes two rectangular waveguide ports, carrying two separate signals. The stator has two corresponding rectangular waveguide ports. The ports are coupled with a circular waveguide, which comprises two relatively rotatable stub-cylinders, disposed co-axially in-line on the axis of rotation. Signal A is transmitted through the circular waveguide, across the joint, in the TM01 propagation mode, while signal B is transmitted across the joint in the TE01 mode. These circular-symmetrical modes, with mutually orthogonal field distribution, are able to cut cross-talk interference, since the mode transducers of these modes maintain good mutual isolation, even though the signals are present together in the circular waveguide, and at the same or similar frequency. The TM01 mode (signal A) is excited, and received, by means of slots formed in the end wall of the circular waveguide stubs. The port for signal A communicates with the circular waveguide through the two slots.

Abstract: A simulation device is provided for testing autotrack antennas. The device includes a mode coupler and transmit horn which are identical to the mode coupler and transmit horn of the antenna to be tested. The mode coupler has a plurality of waveguide input ports for transmitting voltage signals which are complex conjugates of signals occurring under receiving conditions. The device then generates a signal that simulates the far-field, plane-wave testing environment and applies this signal to an antenna to be tested.

Abstract: A mode coupler for vertically polarized modes comprises a first waveguide (32) having a relatively small rectangular cross-section and a second waveguide (22) having a relatively large rectangular cross-section. The first small cross-section waveguide has a wall (300) formed in common with a portion (400) of a wall (200) of the second large cross-section waveguide. The common wall portion contains a series of circular apertures (202) extending in a longitudinal direction of both waveguides. The centers of the apertures are displaced a first distance (.tau..sub.1) from a center line of a wall of the first waveguide and a second distance (.tau..sub.2) from a center line of the wall of the second waveguide. In this case, a fundamental TE.sub.01S mode of the first waveguide is in phase synchronism and couples equally to the two degenerate TE.sub.11L and TM.sub.11L higher order vertically polarized modes of the second waveguide.

Abstract: In accordance with the present invention, a traveling wave coupler generates tracking signals from a circularly polarized microwave signal and includes a waveguide manifold for exciting circular TM.sub.01 and TM.sub.11 modes of said circularly polarized microwave signal. The waveguide manifold includes an input port, a propagation length, and an output port. A coupling arm waveguide includes an auxiliary input port and an auxiliary output port and is aligned and connected to the waveguide manifold along a portion of the propagation length. A coupler located between the waveguide manifold and the coupling arm transforms microwave energy of a TM.sub.01 mode of the circularly polarized microwave signal into a rectangular TE.sub.10 mode in the coupling arm waveguide. The coupling arm waveguide and the coupler generate a difference signal, used to generate the tracking signals, at the auxiliary output port related to the coupled TE.sub.10 mode.

Abstract: A TE.sub.21 coupler having at least two auxiliary rectangular waveguides asymmetrically disposed around the center line of a TE.sub.21 circular waveguide, the waveguides sharing common walls in which coupling slots are disposed, the slots providing for rectangular TE.sub.10 mode propagation coupling to orthogonally aligned TE.sub.21 modes in the circular waveguide.

Abstract: The mode convertor employs two intermediate modes, a coaxial TEM and a rectangular waveguide TE.sub.10 mode, in the transition between the TM.sub.01 and TE.sub.11 circular waveguide modes. The coaxial line provides isolation while acting as a mode filter between the device input and output ports. The rectangular waveguide provides a wide mode separation ratio between the TE.sub.10 and TM.sub.11 modes. The TE.sub.10 mode then transitions into the TE.sub.11 in the circular output waveguide. The coaxial section keeps the output TE.sub.11 mode from scattering back to the input, and the rectangular section keeps the TM.sub.01 from being excited in the output.

Abstract: A modulated bunched electron beam incident on the inner conductor 16 of a coaxial structure launches TEM waves that are distributed to multiple radial waveguides 22 around the outer conductor 14 of the coaxial structure. A tuning piston 32 may be moved axially within the outer conductor for matching the impedance of the coaxial structure to the waveguide array.

Abstract: A dual mode waveguide orthomode transducer has a section of circular waveguide (12) and a transition (16) from circular waveguide to rectangular waveguide disposed coaxially along a longitudinal axis (38). A terminus of the transition (16) opposite the circular waveguide (12) serves as a straight port (46) for input signals, and at the opposite end of the circular waveguide there is a front port (14) for outputting electromagnetic signals. A side port (48) connects via a tapered rectangular waveguide (40) perpendicularly to the longitudinal axis (38) to connect with the circular waveguide (12), and to couple electromagnetic energy into the circular waveguide (12) via a window (50) disposed in a sidewall (42) of the circular waveguide. A plane of polarization of a wave in one input port is perpendicular to a plane of polarization of a wave in the other input port.

Abstract: A dually polarized monopulse feed system for processing radar signal information from a target so the target may be identified and tracked includes a symmetrical multimode input waveguide, a coupler for separating polarized modes of signal waves to identify and track the target, waveguides for rejecting and terminating selected polarized modes of signal waves, and a backshort for reflecting selected polarized modes of signal waves.

Abstract: A device for the filtering of electromagnetic waves propagating in a main rotational symmetrical waveguide element comprising at least one filtering section constituted of a rectangular waveguide section inserted in being spliced into the main waveguide element, each transition between said main waveguide element and each of said filtering sections being made by metal walls which are substantially perpendicular to said axis of symmetry, the number and the geometrical and dimensional characteristics of the filtering sections being chosen so as to constitute a filter with a pre-determined filtering profile. The device can be applied especially in dual band filtering, for example for the making of dual band or bi-polarization duplexers.

Abstract: An antenna system for producing a millimeter wave beam having a Gaussian distribution uses a high power source and a partial mode converter operatively coupled to the source and reviving from the source a T.sub.m,n mode wave which might either be TE.sub.m,n or TM.sub.m,n'. The converter delivers a mixture of modes including the mode T.sub.m,n at a relative power rate of 70 to 85% and at a relative phase 0, and at least one of the following additional modes, namely T.sub.m,n-1 at a relative power rate of 10 to 20% and at relative phase .pi., and TE.sub.m,n+1 at a relative power rate of 10 to 20% and at relative phase .pi.. The mixture of modes is applied to a collimation reflector (3, 10), having a concentration point (5) constituting the antenna system outlet. The antenna system can convert any T.sub.m,n mode into a linearly polarized narrow beam of very high power (about 1 MW) and and of high frequencies above 100 GHz.

Abstract: The invention is a mode converter and power splitter device for electron tubes, particularly gyrotrons and tubes of similar categories. These tubes have an output cavity 2, which is a circular form about a centerline, and a hollow electron beam 1 which propagates along the same centerline. The device complying with the invention is a structure which comprises secondary wave guides 6, symmetrical in azimuth around the same centerline as the outlet cavity, each guide 6 containing coupling apertures 7 on its outer wall (that furthest from the centerline), these apertures 7 being arranged to excite a given mode in the guide. One important embodiment of the invention is that the electron tube operates in a TE.sub.m,n mode with a high azimuth index m and the number of secondary guides 1=m. Another important embodiment of the invention is that secondary guides 6 are trapezoidal in section. Another important embodiment of the invention is that secondary guides 6 are excited in the fundamental mode.

Abstract: There is provided a gyrotron including a quasi-optical mode converter wherein a solid dielectric layer such as silicon carbide for absorbing unnecessary millimeter waves generated by diffraction of the quasi-optical mode converter is arranged in annular shape in the periphery of the quasi-optical mode converter, and millimeter absorption fluid can be supplied to the periphery of the mode converter in a predetermined direction through vacuum barrier walls formed by a dielectric member, thereby efficiently absorbing the diffracted millimeter wave which is the cause of generating heat.

Abstract: A mode converter for converting transverse electric modes into hybrid modes of type EH.sub.mn and including a circular waveguide provided with corrugations extending in a circumferential (azimuth) direction that become deeper toward its end and are continued in a subsequent helically outlined aperture antenna with constant depth. The emitted radiation is circularly polarized and, by the use of suitable reflectors for the emitted radiation, may be cause to be linearly polarized. The emitted radiation no longer has any sidelobes in the far field and its characteristic has a Gaussian profile over the azimuth angle.

Abstract: A transition element for electromagnetic waveguides of the type designed to provide for the transition between a circular waveguide and a coaxial waveguide, constituted by a circular external guide cooperating with an internal conductor forming an end portion of the central conductor of the coaxial waveguide, the internal conductor having at least one intermediate transition step with a substantially constant section throughout its length. The device can be applied notably to the making of two-band duplexers.

Abstract: A gyrotron having a mode converter located in the path of a wave passing passage, the mode converter comprising a means for mode-converting electromagnetic wave into a radiating electromagnetic wave having an annular-shaped power distribution in a plane perpendicular to the direction in which the electromagnetic wave propagates, a ring-shaped mirror (annular mirror) for reflecting the radiating electromagnetic wave which has been converted by the mode converting means, and a waveguide tube having a kerf (i.e., a cutting portion of the tube) opposed to the annular mirror to receive the electromagnetic wave reflected by the annular mirror.

Abstract: In a gyrotron having an annular collector for an expanded e-beam and a gyrotron output waveguide with an annular gap for passing the expanded e-beam is provided with a mode converter between the resonator and the gap to shift more energy to the waveguide central axis to decrease EM field leakage coupling through said gap.

Abstract: A compact waveguide bend structure having high power handling capability, particularly designed for use with TE.sub.01 circular overmoded waveguide, comprises a transition from circular overmoded waveguide to rectangular overmoded waveguide (using the TE.sub.20 mode), followed by a TE.sub.20 mode rectangular waveguide bend, and a transition back to circular overmoded waveguide.

Abstract: Quasi-optical stripline devices for forming and controlling a beam of radio waves are described. The devices include a strip transmission line having a pair of mutually parallel flat outer conductors and a flat center conductor with a dielectric between them. The center conductor has a narrow channel region, a wide expansion region and a tapered region smoothly connecting the regions. A beam of radio waves propagates freely in the expansion region and can be controlled in a quasi-optical manner by the pattern of the center conductor. The quasi-optical nature facilitates easy visualization of the devices for easy design and manufacture.

Abstract: An optical converter for efficient conversion of millimeter wavelength whispering-gallery gyrotron output into a linearly polarized, free-space Gaussian-like beam. The converter uses a mode-converting taper and three mirror optics. The first mirror has an azimuthal tilt to eliminate the k.sub..phi. component of the propagation vector of the gyrotron output beam. The second mirror has a twist reflector to linearly polarize the beam. The third mirror has a constant phase surface so the converter output is in phase.

Abstract: A dual band feed arrangement for a microwave antenna provides microwave communication in a lower band and in a substantially widened upper band to provide simultaneous microwave communication for three signals. One signal in the lower band propagates between the outer and inner conductors of a coaxial waveguide in the TE.sub.11 coaxial mode, and two signals in the upper band propagate in the inner conductor in TE.sub.11 circular waveguide mode. A combiner, having a conically shaped section with a plurality of irises through its sidewall, is coupled to the coaxial waveguide to provide a transformation from the TE.sub.11 modes to the HE.sub.11 waveguide modes for each of the three signals. A dielectric rod extends from within the inner conductor and into the horn antenna for propagating the second signal out of and into the antenna.

Abstract: A field-twisting waveguide junction (20) for electromagnetic microwaves (S1) has a rectangle-like cross-section at one end (21) thereof. This cross-section deviates from a true rectangular shape, by virtue of an inwardly projecting ridge (22). The other end (23) of the junction (20) has a rectangular cross-sectional shape, and the cross-section of a central section (F-F) of the junction has an L-shape. The junction (20) comprises sections, in the illustrated embodiment six sections, the cross-sectional shapes of which are changed step-wise between the sections. The width direction (B2) of the rectangular cross-section (23) has the same directional sense as the height direction (h1) of the inwardly projecting ridge (22). The junction (20) is intended for connecting a rectangular waveguide to a ridge waveguide and transfer the microwaves (S1). The microwave has an electrical field vector (E) whose direction is rotated through one-quarter of a revolution during transfer of the microwave.

Abstract: The present invention is directed to a mode transformer for a microwave energy transmission circuit. This transformer is interposed between an electromagnetic wave source, operating in a predetermined frequency band, and a waveguide transmitting energy. This waveguide is excited by the electromagnetic wave source in a single chosen mode. The transformer has the shape of a conical tube whose large end is connected to the waveguide. The electromagnetic wave source is connected to the conical tube by a lateral opening. In the region of the conical tube where the excitation takes place the cross-section of the conical tube is smaller than that of the waveguide. At the center of the lateral opening, the cross-section of the conical tube is that which would be that of a waveguide of the same shape whose cut-off frequency, for the chosen mode, would be the central frequency of the working frequency band.

Abstract: Dielectric-filled longitudinal slots in the common wall of concentric circular and coaxial dielectric-lined waveguides allow microwave energy to be efficiently coupled therethrough. Such couplers are used with megawatt level gyrotrons for varied applications. One application provides a double seal waveguide vacuum window with low reflections over a wideband of frequencies. Another application provides an output coupler and window for quasi-optical gyrotrons. Still another application provides a waveguide mode converter for converting high order microwave modes, as are commonly found in waveguide cavities of high power gyrotrons, to lower-order modes suitable for low-loss transmission, such as the HE.sub.11 mode.

Abstract: Conversion from a whispering gallery or volume mode to a more useable mode, such as the HE.sub.1,1 mode is achieved in a waveguide mode converter that includes input and output sections. The input section includes overlapping circular and coaxial waveguides. Microwave energy in a whispering gallery or volume mode within the circular waveguide is coupled through an array of N equally spaced axial slots placed in the common wall separating the circular waveguide and the coaxial waveguide to coaxial TE and TM modes. Helical grooves placed in one of walls of the coaxial waveguide convert the coaxial mode to a quasi parallel plate mode wherein the common wall separating the inner circular waveguide from the outer coaxial waveguide functions as one plate, and the outer wall of the coaxial waveguide functions as the other plate. The quasi parallel plate mode propagates microwave energy spirally through the coaxial waveguide in a direction k, where k makes an angle .theta. to the waveguide axis.

Abstract: A waveguide low pass filter is composed of an assembly of an outer waveguide, an inner waveguide shorter in length than the outer waveguide, and a printed circuit filter substrate. The outer and inner waveguides have split block constructions. The inner waveguide is mounted within the outer waveguide so as to form a constriction within the outer waveguide limiting propagation of energy within the outer waveguide to the fundamental TE.sub.10 waveguide mode. The printed circuit filter substrate is mounted to extend longitudinally between the assembled split halves of the respective outer and inner waveguides, and is constructed of a substantially planar dielectric substrate element and upper and lower conductive plate elements on the substrate and lying in the plane thereof. The conductive plate elements define a tapered dual ridge transformer section. The lower plate element has longitudinally spaced vertical slots formed therein defining an open stub slotted filter array.

Abstract: Disclosed is a microwave load in a small-length oversized waveguide form. It comprises a body in waveguide form, made of an absorbent material with both its ends open. An oversized waveguide propagating low loss microwaves that have to be attenuated is connected to the end of the load. The cross section of the interior of the body is substantially equal to or greater than the cross section of the interior of the oversized waveguide. A mode reflecting and converting device closes the end of the load.

Abstract: A waveguide mode converting apparatus especially of the TM.sub.01 to TE.sub.11 converting type and usable in circuit waveguide apparatus with desirable high efficiency and relatively small physical size is disclosed. The mode converter employs the combination of an asymmetrically shaped conical frustum waveguide segment together with a radially disposed fin having tapered input and output or ramp surfaces. Details of a 1.3 gigahertz embodiment of the mode converter including dimensions are included along with the results of efficiency measuring and indications of alternate arrangements of the invention.

Abstract: A hollow waveguide includes a conductive peripheral wall arrangement centered on a longitudinal axis. The waveguide is short-circuited at a first transverse plane. A center conductor is connected to the short-circuit and extends along the longitudinal axis to an abrupt open circuit termination at a second transverse plane. The arrangement is fed at a location between the first and second transverse planes to produce both a fundamental waveguide mode and a center-conductor coupled mode. The fundamental mode has an amplitude taper in the horizontal direction but not in the vertical direction. At the abrupt termination, a higher-order waveguide mode is generated which, when phase-shifted by 180.degree., provides an amplitude taper in a vertical direction. A radiating aperture located near the 180.degree. phase shift point produces a radiation pattern which is similar in both the verticla and horizontal planes.

Abstract: During multipath fading in a terrestrial digital radio system, off-axis arrival of signals excites higher-order modes in a horn reflector antenna. In the disclosed system specified ones of these higher-order modes and the fundamental mode are allowed to propagate in a main waveguide connected to the antenna. At least one of the higher-order modes is abstracted from the main waveguide and fed to a standby receiver while the fundamental mode is propagated intact to a main receiver.Error occurrences in the fundamental and higher-order modes due to multipath fading are substantially uncorrelated. Hence, upon detecting an error in the signals delivered to the main receiver, the system switches to the standby receiver thereby to provide in a single-antenna a significant improvement in performance against multipath fading.