General TE/sub 011/-Mode Waveguide Bandpass Filters

A new structure for high-Q TE/sub 011/-mode circular waveguide cavities is introduced and shown to realize the most general bandpass-filter transfer functions. Methods of improving the mode purity and suppressing the degenerate TE/sub 111/ mode are presented. Several experimental narrow-bandpass filters having finite attenuation poles have been constructed; their measured responses show excellent agreement with theory. Average realizable unloaded Q's of 20000 and 16000 have been achieved at 8 and 12 GHz, respectively.     

Circular TE/sub 011/Mode, Trapped-Mode Band-Pass Filters

Band-pass filters are described which utilize a novel type of resonator which has been named a "'trapped-mode resonator." This type of resonator uses a structure which is open on its sides so that energy in all but a single desired mode tends to radiate out to energy-absorbing material. However, energy in the desired resonator mode is trapped within the structure and a high-Q resonance occurs, such as is typical of conventional microwave cavity resonators. The use of resonators of this type makes possible the design of band-pass microwave filters which have a pass band similar to that of other multiresonator microwave filters, but without the many unwanted pass bands which are typical of microwave filters. The particular type of filter discussed utilizes the circular TE/sub 011/ mode. Several experimental filter structures of this type were constructed, and the results of laboratory tests are described.     

Improved Selectivity in Cylindrical TE/sub 011/ Filters by TE/sub 211/TE/sub 311/ Mode Control

A new method is presented for the design of low loss cylindrical TE/sub 011/-mode resonators whereby transmission nulls can be placed near the TE/sub 011/, resonance by controlling the TE/sub 211/, and TE/sub 311/, modes that are naturally excited in the same resonator. The frequencies at which the nulls occur are controlled by the angular offset of the sidewall coupling apertures and the relative amplitude of the TE/sub 011/ mode compared to the TE/sub 211/ and TE/sub 311/ modes. It is also shown that a lumped constant circuit model can be used to accurately represent the multimode response of the resonator.     

TE Sub/011 Mode Sectorial Circular Cylindrical Cavities Filters

This paper presents a new cavity resonator for the TE /sub 011/ circular mode which allows a compact mechanical structure for a multiple-cavity filter and retains many electrical characteristics of larger filters. Theoretical values of Q are obtained, mode separation is demonstrated, and a 4-cavity experimental model with an elliptic transfer function is described.     

Cylindrical TE/sub 011/ /TM/sub 111/ Mode Control by Cavity Shaping

An appropriate modification of the shape of a cylindrical filter cavity has been used to separate the degenerate TM/sub 111/ (doublet) modes while at the same time providing a slight increase in the already high unloaded Q of the desired TE/sub 011/ mode. Experimental results of mode frequencies and unloaded Q's are tabulated for a family of shaped cavities. Two low-loss filters utilizing these cavities are discussed. The general correspondence between modes of spherical, cylindrical and rectangular cavities and waveguides is described in order to place the performance of intermediate shapes in perspective.     

Circular TE/sub 0n/ Mode Filters for Guided Millimeter-Wave Transmission

A millimeter-wave circular TE/sub 01/ mode waveguide generates undesired circularly symmetric modes (TE/sub 02/, TE/sub 03/ modes, etc.) in bends or at discontinuities along a waveguide line. This paper describes the theory and experiment on the TE/sub 02/ and TE/sub 03/ mode filters developed for guided millimeter-wave transmission. The experimental results of two improved TE/sub 03/ mode filters show that the attenuation of the TE/sub 03/ mode is more than 16 dB for one type over the 40-70-GHz range. The TE/sub 01/-mode insertion loss of another type is about 0.2 dB over the 40-80-GHz range. The present mode filters can be applied to various high-speed guided rnillimeter-wave systems currently under development.     

Temperature Compensation of TE/sub 011/-Mode Circular Cavities (Short Papers)

This short paper describes a novel method for temperature compensation of TE/sub 011/-mode circular-waveguide cavities. Implementation and experimental results on a single cavity are presented.     

TE /sub 11/ to HE /sub11/ Cylindrical Waveguide Mode Converters Using Ring-Loaded Slots

A theoretical parameter study is given of a TE/sub 11/ to HE/sub 11/ mode converter consisting of a section of cylindrical corrugated waveguide with ring-loaded slots. The analysis, using modal field-matching techniques to determine the scatter matrix of the converter, allows the return loss to be computed accurately. For a wide range of waveguide sizes it is shown that a bandwidth ratio of 1.5 with a return loss better than 30 dB is possible. The low-frequency performance of the converter is limited by the deterioration in return loss, while at high frequencies the generation of a small amount of unwanted EH/sub 12/ mode is the restriction. If the effects of this mode can be neglected, operation over a wider bandwidth is possible, particularly for larger waveguide size.     

Slot-Coupled T-junction of TE/sub 11/ Coaxial to TE/sub 10/ Rectangular Waveguide

A solution is presented to the problem of a slot-coupled T-junction of a TE/sub 11/ -mode coaxial to a TE/sub 10/ -mode rectangular waveguide. A variational technique is employed which combines the reaction concept with the field representation of a waveguide slot and leads to a closed-form solution for the junction scattering matrix. Numerical examples illustrate the characteristics of such a junction in practical applications. Good agreement between theory and experiment is obtained. Design criteria and examples are presented and discussed.     

A Single-Ridged Coaxial Hybrid TE011 Coupler with High Mode Purity

We design a single-ridged coaxial hybrid coupler which excites a TE₀₁₁ mode of high mode content in a cylindrical cavity, resonating at 28.2GHz. The coupler consists of a WR-28 rectangular waveguide, a coaxial TE_n11 cavity, and a cylindrical TE₀₁₁ cavity. Both TE₃₁₁ coaxial cavity and TE₄₁₁ single-ridged coaxial cavity are analyzed to examine the TE₀₁₁ mode purity in the central cavity. Mode purity analysis is performed by a field expansion method using Fourier-Bessel orthonormal basis functions. Numerical calculations predict that the TE₄₁₁ single-ridged coaxial cavity excites the TE₀₁₁ mode with mode purity of 98.6%, which is improved by 3% higher compared with the TE₃₁₁ coaxial cavity. Measurements on the single-ridged coaxial coupler show a resonant frequency at 28.078GHz and ohmic and external Qs of 1560, 473 respectively, which are in good agreement with the simulated results of a 3-D finite element electromagnetic code.     

TE/sub 01/ Mode Components in the 3-mm Region

In the 3-mm region (94 Gc) it is desirable to use waveguide components operating in the low loss TE/sub 01/ mode in circular waveguide rather than in fundamental-mode rectangular waveguide. Because this is a higher mode, mode purity is of major concern. A method of identifying undesired modes and their amplitudes is by means of radiation patterns from the end of the waveguide. Components developed to operate in this mode include a transition from rectangular to circular waveguide, standing wave detector, variable attenuator, directional coupler, flexible waveguide, fixed 90/spl deg/ bend and rotary joint.     

Quarter-Wavelength Coupled Dielectric Plate Resonators for High Selectivity TE/sub 10/-Mode Filters

An analysis of high selectivity TE/sub 10/-mode filters with quarter-wavelength coupled resonators formed by axially spaced dielectric plates is presented and shows that high-loaded quality factors of individual resonators can be obtained by placing the resonant frequency close to the waveguide cutoff frequency and by using low-loss Iow-dielectric constant materials. Design equations for Butterworth and Chebyschev filters are presented and employed in a three-cavity Butterworth filter having 30-MHz bandwidth at resonant frequency at 7250 MHz. Experimental results show that filter performance can be well predicted.     

Analysis and Design of TE/sub 11/-to-HE/sub 11/ Corrugated Cylindrical Waveguide Mode Converters

A theoretical parametric study is given of a TE/sub 11/-to-HE/sub 11/ mode converter consisting of a section of cylindrical corrugated waveguide with varying slot depth. The analysis makes use of modal field-matching techniques to determine the scatter marks of the mode converter from which we deduce its propagation properties. It is shown that a mode converter consisting of only five slots achieves a return loss better than 30dB over the band 2.7相似文献   

Calibrated Reflection Coefficient Standards for the Circular TE/sub 01/ Mode

This paper describes simple reflection coefficient standards for use with the circular TE/sub 01/ mode. They consist of circular irises inserted directly into the flange connection of a "matched" termination. The reflection coefficient of an iris is formulated exactly and then evaluated to any desired degree of approximation with a digital computer. The results of a 30-mode approximation are presented and shown to agree with 24 GHz measurements of the modulus and phase of /spl rho/ of 7 irises to within about 0.008 relative units and 0.02 radians, respectively.     

A Compact, Wide-Tuning Range, Dual TE/sub 111/ Mode Preselector

This paper describes the development of a dual TE/sub 111/ mode cavity preselector that is centrally loaded with a large, nonferrous, metallic perturbation plug. The cavity tunes over the 6 to 8 GHz range. Dual mode operation reduces the size of the cavity to one-half the size of a conventional cavity. The perturbing plug increases the separation between the desired TE/sub 111/ mode and the undesired, next higher TM/sub 011/ mode from 15 Percent to 33 Percent. The result is a 29 percent tuning range that is free from unwanted modes. The preselector exhibits a 3 dB bandwidth of 60 MHz, a 40 dB bandwidth of about 400 MHz, and an insertion loss that is no more than 1 dB.     

The Susceptance of an Annular Metallic Strip in a Circular Waveguide with Incident TE/sub 01/ Mode

The principal aims of this paper are twofold: 1) to solve the problem of the scattering of a thin, perfectly conducting aonular strip suspended in a multimodal circular waveguide in which any number of TE/sub 0n/ modes can propagate, and with the aid of this result, 2) to give the susceptance of the thin annular strip in monomodal circular guide with an incident TE/sub 01/ mode. These are treated with a variational approach. Applying the appropriate Green's functions to the continuity equations for the transverse electric field yields a variational expansion for the scattering matrix elements. This is treated with a Rayleigh-Ritz procedure and matrix methods. Curves of normalized susceptance as a function of the free-space wavelength and the size of the annular metallic strip are shown. These results are in good agreement with experimental data. Tables of the scattering coefficients for a typical wavelength versus strip size are also included.     

A More Accurate Model of the TE/sub10/ Type Waveguide Mode in Suspended Substrate

An analytical model of the suspended substrate transmission Iine which includes the grooves used to support the substrate is presented. The model predicts a lower cutoff frequency of the TE/sub 10/ type waveguide mode than that without the grooves. The analysis is confirmed by experiments.     

Spatial and Temporal Coherence of a 35-GHz Gyromonotron Using the TE/sub 01/ Circular Mode

The characteristics of a 35-GHz oscillator operating with the TE/sub 01/ circular waveguide mode are described. The device produced 147 kW, with an efficiency of 31 percent at 100 kW. The total radiated energy was 2 kJ/pulse. The spectral coherence appears to be equal to those of other high-quality microwave tubes. The mode purity is greater than 95 percent.