Abstract: A waveguide bandpass filter employs a waveguide section and a printed cirt filter assembly having a dielectric substrate positioned in the waveguide between the narrow walls thereof and a row or array of half-wavelength conductive metal plate elements lying in a surface plane of the dielectric substrate that is oriented substantially parallel to narrow walls and orthogonal to broad walls of the waveguide. The half-wavelength conductive metal plate elements, defining a parallel resonant array, are spaced in non-conductive relation from one another and from the broad and narrow walls of the waveguide so as to divide and transform a dominant waveguide propagation mode into a transformed propagation mode that approximates upper and lower microstrip sections interconnected by a metallic conductor.

Abstract: A dielectric waveguide-type filter is fabricated by vapor depositing or coating all but one of the four sides extending in the axial direction of a six-sided dielectric block that is long in its axial direction lying perpendicular to its width and height with a conductive material and either leaving the fourth side surface open or forming it with a conductive pattern depending on whether the filter characteristics to be obtained are high-pass characteristics, band-pass characteristics or band-rejection characteristics, the conductive pattern, if formed, being formed in a configuration and distribution depending on the filter characteristics to be obtained. A pair of electrode patterns for electrical connection with an exterior circuit are provided by patterning of conductive material on the opposite axial end surfaces of the dielectric block or on the open surface at positions near the opposite axial end surfaces.

Abstract: Arrays of printed circuit elements are placed in the E-plane inside waveges to reflect and pass selected bands of frequencies. The elements make no contact with the guide walls but are suspended on dielectric substrates and are held in place with foam dielectric.

Abstract: By combining four hexagonal ferrite spheres under the same electromagnet structure, a magnetically tuneable bandpass filter can be built in waveguide yielding high off resonance isolation, while keeping insertion loss to a reasonable value. Implementations of this filter in A, Q, U, and V bands have typical off resonance isolation greater than 70 dB and insertion loss less than 13 dB for full-band tuning. The filter can be utilized as a preselector for swept-frequency signal analyzers, for example.

Abstract: A nearly square waveguide below cutoff has a microstrip substrate disposed diagonally therein. A first shunt capacitance is provided by either a conductor formed on the microstrip substrate or a conductor disposed in the waveguide perpendicular to the microstrip substrate. A dielectric window is disposed in the end to provide a shunt capacitance at the opposite end of the waveguide.

Abstract: A two, three or four channel multiplexer can be operated in the TE.sub.01.delta. or HE.sub.11.delta. modes, each channel of the multiplexer has one bandpass filter, with each filter usually having a plurality of cavities. One cavity of each filter is a common cavity with all of the other filters of the multiplexer. The common cavity contains one independent dielectric quarter-cut or half-cut image resonator for each filter representing a channel of the multiplexer. Each resonator is mounted on a suitable support the common cavity provides a common junction and contains a loop coupling to couple electromagnetic energy between the various channels. The multiplexer has at least one input and at least one output. Previous microwave multiplexers have a plurality of bandpass filters arranged on a coaxial manifold. With the multiplexer of the present invention, the manifold can be eliminated.

Abstract: An improved transmission line filter element allows a higher difference between even and odd mode impedances than previously obtainable from planar structures. The filter element comprises a U-shaped gap formed in the strip conductor of a strip line transmission line, a microstrip structure or a suspended strip line structure. The internal transmission line filters can be cascaded to produce electromagnetic energy filters with deeper notches and steeper skirts than previously obtainable from other planar structures with the same number of elements.

Abstract: A waveguide filter (100) is provided for functioning as a cable feed-through for previously terminated cables (50). Waveguide filter feed-through (100) includes a housing (110) of predetermined length having a plurality of bores (130, 140) extending therethrough. One of the bores (140) being centrally located, with each of the other bores (130) being located radially about the central bore (140). Each of the radially located bores (130) form an individual waveguide when a plug (120) is inserted within the central bore (140). Each of the waveguide passages (130) include a longitudinal passage extending the full length of housing (110) and opening into the central bore (140).

Abstract: A waveguide band-pass filter has at least two resonators each consisting of a high-impedance section and a low-impedance section. The resonators are cascade-connected at intervals of .lambda.g/4 in a waveguide.

Abstract: A duplexer for use in a feed network for a satellite communications antenna is made in waveguide form and comprises two plate halves each with a pattern of channels on one surface, the pattern on one half being the mirror image of the pattern on the other. When the two halves are assembled with the patterned faces juxtaposed, a receive filter and a transmit filter with receive, transmit and common ports are obtained. Each filter has a main waveguide and several short-circuited half wavelength stubs in serial connection to the main waveguide. The joint between the two halves bisects the waveguide broadwall and is, therefore, of no electrical significance. The simplicity of the design lends itself to fabrication as part of a bigger integral assembly consisting of duplexers and other feed components. After manufacture, no further tuning is necessary.

Abstract: The dielectric resonator apparatus is characterized in that electric walls exist on one plane or two including the central axis of the electromagnetic field distribution in the using mode of a dielectric resonator, a dielectric resonator with either of dielectrics between the electric wall being removed in shape is provided by plurality, an equivalent axis is common to the central axis of each of the dielectric resonators, with the dielectric resonators being inductively coupled in the axial direction. A dielectric resonator which prevents the current from being concentrated on the central axis of the electromagnetic field distribution, is collectively smaller in the Joule loss and is higher in Q. The dielectric resonator of the present invention is characterized in that the dielectric close to the central axis is removed, wherein electric walls exist on one plane or two including the central axis of the electromagnetic field distribution in a dielectric resonator using, for instance, a TE.sub.01.delta.

Abstract: A wideband balanced diplexer splits an incoming wideband microwave frequency signal into separate upper and lower frequency outputs and possesses a sharp band cut-off to increase effective bandwidth. The diplexer includes a pair of waveguide assemblies for separating the upper frequency band from the incoming signal. Each waveguide assembly includes a tuneable, ridged waveguide phase shifter for shifting the phase of the lower frequency band, a reference waveguide for inserting a delay onto the upper frequency signal in order to compensate for the effects of the phase shifter in the other waveguide assembly, and a high pass filter. The high pass filter includes a ridged waveguide having tapered ends of a shape comprising an exponential function raised to a cosine squared power to increase the bandwidth of the upper frequencies and to provide a sharper frequency cut-off.

Abstract: The present invention relates to an E-plane type wideband composite filter comprising a conductive screening body (11, 12) having an elongate cavity (14) therein with a blade cut into a ladder shape disposed longitudinally therein. Said body comprises two portions held against each other on either side of a separation plane along which said ladder (15) is disposed, with two irises (16, 17) being disposed transversely at the inlet and at the outlet of said cavity (14), each closing off a portion thereof.

Abstract: A quadruple mode bandpass filter has at least one cavity resonating in four independent orthogonal modes simultaneously. Preferably, the filter has two cavities, one cavity being a quadruple mode cavity and the remaining cavity being either a single mode, dual mode, triple mode or quadruple mode cavity. By introducing a resonant feedback coupling into filters of the present invention, the number of transmission zeros produced by the filter is equal to the order of the filter. Previous filters have cavities resonating in either a single, dual or triple mode and the maximum number of transmission zeros is equal to the order of the filter minus two.

Abstract: A filter system is composed of two identical filters coupled between an input waveguide and an output waveguide to provide a 4-port directional filter characteristic operable with quasi-elliptic linear modes of electromagnetic propagation within each of the filters. Each of the filters may be constructed of a plurality of cavities arranged serially, one behind the other, with one of the cavities in each of the filters being employed for coupling electromagnetic power between the two waveguides. The coupling is accomplished by use of a transverse slot and a longitudinal slot in each of the waveguides, the slots extending through sidewalls of the waveguides into walls of the cavity in each of the filters for symmetric and antisymmetric coupling, respectively, of longitudinal and transverse components of a transverse electric wave in each of the waveguides.

Abstract: A probe coupled waveguide multiplexer is provided including a first waveguide which serves as a multiplexing manifold; a second waveguide, having a cavity, typically a filter, which is probe coupled to the first waveguide; and a third waveguide which has a cavity and is probe coupled to the first waveguide such that the probe of said third waveguide is diametrically opposed to the probe of said second waveguide and the second and third waveguides are mounted in the same transverse plane in co-planar relation. The probe coupling method and apparatus disclosed herein allows the waveguide filters to be mounted on the manifold in a close physical relation thereby minimizing the length of the manifold and associated costs.

Abstract: A microwave filter composed of a plurality of cylindrical cavity resonators each having a side wall extending parallel to the direction of wave propagation in the resonator, wherein the cavity resonators are disposed with their side walls in contact with one another in a compact cylinder pack arrangement so that the side wall of each cavity resonator is in contact with the side wall of the maximum number of other mutually adjacent resonators, and coupling structures connecting resonators whose side walls are in contact, via the contacting side walls, for coupling electromagnetic energy between the resonators.

Abstract: An arrangement for the equalization of attenuation and time delay in a microwave filter utilizing waveguide technology. An equalizer composed of a multi-circuit cavity resonator is coupled via a first coupling aperture to a waveguide which is connected to the filter. The resonator includes at least two individual waveguide sections coupled to each other via a second coupling aperture. The coupling apertures are dimensioned so that the resonator is critically coupled with respect to time delay characteristics. The resonator includes a power-absorbing tuning device for tuning all of the waveguide sections to substantially the same quality factor. The second coupling aperture presents a stepped cross section defining a first area and a second area having a larger cross section than the first area. The resonator further includes at least two screws arranged symmetrically with respect to the longitudinal axis of the resonator and protruding laterally into the second area of the second coupling aperture.

Abstract: A waveguide filter is provided which comprises a plurality of waveguide resonators arranged in series in the longitudinal direction of the filter with each contacting tightly with adjacent ones, each of the waveguide resonators being composed of a rectangular dielectric having a length and a permittivity complying with the center frequency of a bandpass filter, on the periphery of which a metal film is provided except on the portions of induction windows of its two sides mutually opposed in the longitudinal direction.

Abstract: Circularly polarized radiation is tapped off from an input waveguide through a input iris into an entry cavity, where it is resolved into two orthogonal linearly polarized components. These respectively proceed along two discrete paths to an exit cavity. In each path six independently tunable resonances--traversed by both direct and bridge couplings--provides enough degrees of freedom for quasi-elliptic filter functions. In the exit cavity the resultants from the two paths are combined to resynthesize circularly-polarized radiation, which traverses another iris to the output waveguide. In one layout, four resonant tri-mode cavities form a rectangular array--with entry and exit cavities at diagonally opposite corners and intermediate cavities for the two discrete paths in the two remaining corners.

Abstract: A waveguide-microstrip line converter for mode conversion in transmitting signals from a waveguide to a microstrip line or in the reverse, which comprises a dielectric body, a probe formed integrally with and within the dielectric body, and a conductive layer formed over the surface of the dielectric body excluding a surface to be brought into contact with a waveguide and an area surrounding the connecting part of the probe. The conductive layer is formed over the entire surface of the dielectric body, and then part of the conductive layer is removed by etching to provide the uncoated surface to be brought into contact with the waveguide and the probe. Thus the probe is continuous with the conductive layer and is an integral part of the dielectric body, so that the performance of the probe is unaffected by vibration and the high frequency resistance across the short-circuit waveguide is reduced to reduce signal transmission loss.

Abstract: A waveguide filter comprises waveguides with length corresponding to the center frequency of a band pass filter, and shunt plates. Each shunt inductor plate has sufficient size to cover an opening of the wave guide and includes an induction window smaller than the opening, and each opening is opposed to each induction window. The waveguides and the shunt inductor plates are alternately arranged in close contact state, and the center frequency of the filter scarcely deviates.

Abstract: A waveguide-microstrip line coverter to be used in combination with a waveguide, for mode conversion in transmitting a signal from the waveguide to a microstrip line. A probe for receiving a signal transmitted through the waveguide is formed by forming a conductive layer over the inner surface of a hole formed in a cuboidal dielectric body and is connected directly to the microstrip line to avoid needless induction of inductance. Since the hole can be formed accurately in size and position in the cuboidal dielectric body and the probe is formed in the hole, the probe is formed accurately in size and position and is highly resistant to vibration.

Abstract: An apparatus that utilizes a solid, dielectric-filled waveguide filter in a microstrip circuit is dislosed. The microstrip circuit couples directly into and out from the waveguide filter through slot openings in waveguide filter walls without penetrating the interior of the waveguide. Adjustment of the coupling is accomplished through varying the length of the slot. Resonant frequency tuning of the filter is accomplished using additional slots, or by removing metallic plating from metallized cavities which extend into the waveguide core from a central region of a waveguide broad wall.

Abstract: A microwave radial power divider/combiner device having desirably broad bandwidth response over a selected frequency range. The device includes a radial waveguide that has a number of adjoining annular sections, each of selected radial length and axial height, to provide lumped circuit parameters closely euqivalent to those of an ideal filter with the desired passband characteristics. The ideal filter is first designed using conventional synthesis techniques, then modified, if necessary, to allow its realization in radial waveguide form. The waveguide sections are selected to have lengths and uniform heights to approximate the lumped circuit parameters of the filter, and the dimensions are then optimized to provide the closest approach to the desired performance characteristics.

Abstract: A thin plate member of electrically conductive material is disposed within a rectangular waveguide. The plate member has the thickness less than one tenth of the wavelength of a frequency to be suppressed, an opening whose maximum dimension is less than the length of the short side of the waveguide, and a gap formed between two opposite projections extending from the edge of the opening. The plate member is arranged, in said rectangular waveguide, parallel with the electric field and perpendicular to the magnetic field.

Abstract: A triple mode dielectric loaded bandpass filter has at least one cavity resonating in three independent orthogonal modes. A triple mode cavity can be mounted adjacent to either single, dual or triple mode cavities. Inter-cavity coupling is achieved through the iris having two separate apertures that together form a T-shape. The cavities can be planar mounted. The filter is designed for use in the satellite communication industry and results in substantial savings in weight and size when compared to previous filters.

Abstract: In a microwave push-pull frequency converter having the form of a waveguide for effecting frequency conversion of a broadband microwave signal, which converter includes a converter module composed of a waveguide section and a pair of semiconductor mixer elements disposed in the waveguide section for effecting frequency conversion between a high frequency microwave signal and a low frequency microwave signal without intermediate frequency conversion, the converter further including a waveguide filter for the low frequency microwave signal connected to one side of the module, the waveguide filter includes a plurality of ridged waveguide sections and a plurality of blocking waveguide sections interposed between, and coupling, the ridged waveguide sections, and the converter module includes fastening devices supporting the semiconductor mixer elements and configured to give the coverter module the form of a ridged waveguide which permits the high and low frequency microwave signals to pass in a single mode.

Abstract: A dual mode filter has a hollow cylindrical longitudinal outer body which is divided by transversely extending disk-like separation walls into a plurality of internal cavities. At least one coupling opening in each separation wall permits coupling of energy from one cavity to another. Said coupling opening being preferably an arcuate opening, in each separation wall, which extends along a constant radius at the outer periphery of the separation wall and over a limited angular span. When the openings are two, they are spaced 180.degree. apart, i.e. opposite one another. Adjacent separation walls are rotatably displaced 90.degree. with respect to each other so that their respective coupling opening(s) is (are) misaligned by 90.degree.. One respective adjustment screw is provided for each separation wall which penetrates through a hole in the outer body into one of the coupling openings in the given separation wall.

Abstract: An odd order bandpass filter has at least one cavity resonating at its resonant frequency in three independent orthogonal modes. The filter has at least one feedback coupling that is made to resonate and change sign at a center frequency. When the filter has two cavities, one being a triple cavity and the other being a dual mode cavity, the filter can be operated to achieve an elliptic function response. Also, the filter of the present invention can achieve a weight and volume reduction when compared to six-pole dual mode filters.

Abstract: A bandpass filter has a plurality of cascade waveguide cavities each resonating in three independent orthogonal modes. The cavities can be cylindrical or have a square cross-section. Where the cavities are circular, each cavity resonates in TE.sub.111 or TE.sub.010 modes simultaneously. Where the cavities have a square cross-section, each cavity resonates in TE.sub.011 and TM.sub.110 modes simultaneously. Between each triple-mode cavity, there is located an iris having an aperture with four separate radial slots that are offset from a center of the iris. The filter is capable of producing an elliptic function response. In a variation of the invention, an allpass filter has an output that is short circuited and, when used in conjunction with a circulator, it functions as a group delay equalizer. Previous triple-mode filters are not capable of producing an acceptable result relative to dual-mode filters.

Abstract: A low-loss bandpass microwave filter is disclosed which enables filter size reduction in the frequency range of 1-5 GHz. The filter includes a main ceramic body member which is notched or drilled and coated over all exposed surfaces except for opposite end portions. Coupling terminals are attached to the opposite end portions to provide microwave input and output coupling to the filter.

Abstract: In accordance with the present invention there is provided a bandpass T filter and power splitter for electromagnetic energy. It is composed of a plurality of resonant elements serially arranged to form a plurality of forward multi-pole bandpass filters. At least one resonant element is common to both signal paths. The common resonant element transfers energy from the common path to the independent signal paths to effect a power split. The two signal output paths are isolated from one another by a multi-pole bandpass filter. The resonant elements may be composed of either resonant waveguide cavities or dielectric resonators.

Abstract: A waveguide filter particularly well suited for use in the millimeter and submillimeter wavelength range of the spectrum. The filter includes a number of uniformly spaced gratings installed in a waveguide section and having grating strip patterns contoured to conform with a selected waveguide mode, such as the circular TE.sub.11 mode. The gratings are angularly oriented in the manner of a free-space plane-wave quasi-optical filter and provide similar desired frequency characteristics, but without the disadvantages of large size and the need for planewave launchers.

Abstract: There is provided a method and a corresponding apparatus for establishing the proper bandwidth at one frequency in a microwave, dielectric resonator waveguide filter.Bandwidth is determined by the product of the resonant center frequency and the interresonator coupling coefficient. The interresonator coupling coefficient has been found to vary depending upon the interresonator spacing as well as the position at which the resonators intercept the electromagnetic field distributed across the waveguide.This method establishes the proper combination of field-intercepting position and interresonator spacing such that the proper bandwidth is established at one frequency.

Abstract: A method and corresponding apparatus for maintaining constant bandwidth over a frequency spectrum in a microwave, dielectric resonator waveguide filter. Bandwidth is determined by the product of the resonant center frequency and the interresonator coupling coefficient. To maintain constant bandwidth while changing center frequency, the interresonator coupling coefficient must be chosen such that it varies inversely with changes in center frequency. The interresonator coupling coefficient is a function of the physical dimensions of the waveguide and the dielectric resonators, the dielectric constant and the spatial location of the resonators within the waveguide. Once the physical and spatial parameters have been established, the center frequency of the filter may be adjusted by altering the thickness of the resonators without changing the filter bandwidth.

Abstract: A microwave dielectric resonator is supported between plural laminated layers of polymeric material having relatively lower dielectric constant.

Abstract: A microwave dielectric resonator, e.g. for use in a microwave filter or oscillator, is provided with a tough low loss mount. The mount comprises a polymeric support layer 4, which is provided with an aperture 3 beyond which the resonator extends. About the first polymer layer 4 are a pair of polymeric retaining layers 2, 2'. These three polymer layers may be heat bonded together to secure the resonator. Interlayers 5 may be used between the three polymer layers 4, 2, 2' in order to effect a bond.

Abstract: A method and corresponding apparatus for maintaining constant bandwidth over a frequency spectrum in a microwave, dielectric resonator waveguide filter. Bandwidth is determined by the product of the resonant center frequency and the interresonator coupling coefficient. To maintain constant bandwidth while changing center frequency, the interresonator coupling coefficient must be chosen such that it varies inversely with changes in center frequency. The interresonator coupling coefficient is a function of the physical dimensions of the waveguide and the dielectric resonators, the dielectric constant and the spatial location of the resonators within the waveguide. Once the physical and spatial parameters have been established, the center frequency of the filter may be adjusted by altering the thickness of the resonators without changing the filter bandwidth.

Abstract: In a microwave receiving apparatus using a waveguide filter, the waveguide filter is disposed in parallel to a microwave reception circuit board mounted in a shield container.

Abstract: A dielectric filter (FIG. 16) for frequencies higher than VHF band comprising a closed conductive housing (112), a pair of input and output means provided at both the extreme ends of said housing (112), a dielectric body (111) with a plurality of linear parallel grooves (118) arranged in said housing (112), a plurality of conductive linear means (113) with the length of approximately 1/4 wavelength mounted in said dielectric body (111) between said grooves (118) so that one end of said resonators (113) is fixed to the common plane of the housing (112), a capacitor means (114, 115) provided between the other end of resonators (111,113,118) and said conductive housing (112) so that an electrode (115) of said capacitor may be trimmed by a laser beam to adjust the resonating frequency of each of said resonators (111,113,118) and a plurality of conductive rods (137) provided in said grooves (118) for improving the spurious characteristics of the filter.

Abstract: A signal modifying device comprises an elongate section of waveguide and a non-linear circuit element. A lateral through-hole is formed in a wall of the waveguide, and a rod-like conductive member is fitted in the hole and has one end presented towards the opposite wall region of the waveguide. The non-linear circuit element is secured to the rod-like member with one electrode connected in electrically conductive manner to the rod-like member and with a beam-like lead (which is connected to another electrode of the circuit element) extending towards the opposite wall region of the waveguide.

Abstract: A structure comprising a cascade of dual mode resonance cavities wherein each cavity has a pair of tuning screws located at 90.degree. to each other in a sectional plane of the cavity and a coupling screw located at 45.degree. to the tuning screws for coupling the two resonances supported by the cavity. Each cavity is coupled to the adjacent cavity by means of a coupling iris set at a determined angle relative to the angular position of the tuning screws of the cavity and the adjacent cavity is positioned at a determined angle relative to the angular position of the coupling iris which couples said cavity to the former one.

Abstract: A millimeter wavelength bandpass filter arrangement is produced by using a first dielectric waveguide as an input for a broadband signal to a ferrite circulator. This signal is delivered to a second dielectric waveguide having a bandstop filter formed therein. The bandstop filter reflects the desired bandpass frequency(s) back to the ferrite circulator where it is delivered to a third dielectric waveguide which is the output for the bandpass frequency(s).

Abstract: A circuit component for separating and/or combining two pairs of high-frequency signal waves lying in different frequency bands, the waves of each pair having the same frequency but mutually orthogonal planes of polarization, comprises two mutually identical and aligned 3dB couplers bracketing a filtering assembly between them. Each 3dB coupler has a central guide of square cross-section surrounded by four collateral guides, each connected with the central guide by a coupling guide letting only the waves polarized in one plane--regardless of frequency--pass therebetween. The filtering assembly has sets of baffles in line with the central and collateral guides of both couplers, these baffles defining slots giving passage to only the waves of one of the two bands while reflecting the others.

Abstract: A system is disclosed for coupling orthogonal polarized microwave signals from a reflector to signal processing circuits. The system includes successively a horn, a bandpass filter, a polarizer, a mode separator, and a housing for containing the circuits. The system is constructed from two half-shells. The horn, bandpass filter and polarizer form a waveguide portion which is coupled to the circuits by the mode separator.

Abstract: An insertion filter is described for existing waveguide without modification. The filter includes a resilient bifurcated dielectric member (11) which conforms to the internal geometry of the waveguide (21). The dielectric member secures the position of a dielectric resonator (15) and a tuning screw (17) and retains their relative positions. A stud (18) is mounted on one of the bifurcations of the dielectric member to compensate electrically for the presence of the member in the waveguide while the dielectric resonator attenuates waveguide energy in a prescribed frequency band.

Abstract: A waveguide structure carrying microwaves with two mutually orthogonal planes of polarization and in two different frequency bands, transmitted and received by an associated antenna, comprises two orthomode transducers in the form of coaxial cylindrical guide members of different inner diameters, the smaller-diameter transducer terminating in a short-circuiting end wall while the larger-diameter transducer, adjoining same at an annular shoulder, extends to a feed horn confronting a reflector. Each transducer is formed with two elongate peripheral access slots, opening onto respective rectangular-section branches, which are longitudinally bisected by mutually perpendicular axial planes while being relatively offset in axial direction.

Abstract: A wide band travelling wave amplifier including an input waveguide coaxia disposed about an interaction waveguide. Both waveguides are tapered with the same direction of increasing cross-section. The interaction waveguide is a high-pass filter while the input waveguide is a low pass filter. The input waveguide is positioned relative to the interaction waveguide so that each cutoff plane in the input waveguide corresponding to a given frequency, .omega..sub.c, is displaced in the direction of increasing cross-section from a cutoff plane in the interaction waveguide corresponding to .omega..sub.c where .omega..sub.c is any frequency in the frequency band of the amplifier. A slot, disposed between the cutoff planes corresponding to .omega..sub.c couples the .omega..sub.c frequency component of an input wave from the input waveguide to the interaction waveguide.

Abstract: A dual mode directionally coupled band reject filter apparatus having coaxially aligned first and second cylindrical cavity members which are asymmetrically mounted to the broadwall of a waveguide. Both cylindrical cavity members include a plurality of tuning screws to establish elliptic-type responses.