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.     

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.     

General Extracted Pole Synthesis Technique with Applications to Low-Loss TE/sub011/ Mode Filters

A novel synthesis technique is developed for two-port networks which possess finite real frequency transmission zeros. The low-pass prototype is synthesized in the form of a network with complex conjugate symmetry where the real frequency transmission zeros are extracted from both ends and realized by simple resonators separated by phase shifters. The remaining transmission zeros are realized by the central part of the filter in the form of a cross-coupled double array. This prototype is particularly suitable for designing waveguides bandpass filters and each real frequency transmission zero is independently tunable. Furthermore, in the case of the most complex transfer function with all possible types of transmission zeros, the realization requires only one type of coupling which is necessary in the important case of TE/sub011/ cylindrical mode cavity resonators. The general synthesis technique is given and the process illustrated by a nontrival example. Additionally, from the results of a computer program based upon the synthesis techniques, the important differences between the possible prototype forms for the same transfer function resulting from extracting the transmission zeros in different orders are cited.     

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.     

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.     

Multiple Branch-Guide Directional Coupler Using TE/sub 01/-Mode Semicircular Waveguide (Short Papers)

This short paper describes experimental results derived from a newly devised branch-guide directional coupler using a TE/sub 01/-mode semicircular waveguide. The length of an experimental 0-dB coupler is about 150 mm, which is one-third shorter than the conventional coupled wave-type 0-dB coupler, and the loss is decreased in proportion to the reduction in length. Using this coupler, it is possible to manufacture more compact millimeter-wave diplexers with reduced insertion loss.     

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.     

Theory and Design of a Ku-Band TE/sub 21/-Mode Coupler

This paper describes a TE/sub 21/-more tracking coupler for satellite earth stations communications antennas which require autotrack capability. The paper covers theoretical coupler designs as well as laboratory test results from Ku-band hardware.     

Nonminimum-Phase Optimum-Amplitude Bandpass Waveguide Filters

The synthesis of narrow-bandpass waveguide filters having flat group delay and optimum-amplitude characteristics is described. The design utilizes either single- or dual-mode waveguide cavities. Experimental results for a 40-MHz-bandwidth filter centered at 4 GHz show excellent agreement with theory.     

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.     

Waveguide Bandpass Filters for Millimeter-Wave Radiometers

A fundamental requirement for most mm-wave heterodyne receivers is the rejection of the input image signal which is located close to the local oscillator frequency. For this purpose we use a bandpass filter, which for heterodyne receivers is also called an image rejection filter. In this paper we present a systematic approach to the design of a waveguide bandpass filter with a passband from 100 to 110 GHz and upper rejection bandwidth in the range from 113 to 145 GHz. We consider two non-tunable filter configurations: the first one is relatively selective with 11 sections (poles) whereas the second one is simpler with 5 sections. We used established design equations to propose an initial guess for the geometries of the filters, optimized the geometries, constructed the filters using two different milling methods, measured their transmission and reflection characteristics, and compared the measurements with numerical simulations. Measurements of both filters agree well with simulations in frequency response and rejection bandwidth. The insertion loss of the 11-pole filter is better than 10 dB and that of the 5-pole filter is better than 5 dB. The 11-pole filter has a sharper attenuation roll-off compared with the 5-pole filter. The upper out-of-band rejection is better than 40 dB up to 145 GHz for the 11-pole filter and up to 155 GHz for the 5-pole filter.     

TE011模高功率窄带带通滤波器设计

利用圆腔ＴＥ０１１模的高Ｑ值特性，设计了高直接耦合式窄带带通滤波器，并给出了具体的设计步骤和实例，理论与实验结果基本一致。     

Admittance of Irises in Coaxial and Circular Waveguides for TE/sub 11/-Mode Excitation

The admittance of irises in both coaxial and circular waveguides is deduced from a mode-matching technique. Design data for the effective admittance to TE/sub 11/ -mode excitation are given for a range of waveguide and iris dimensions.     

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.     

Design and Performance of Coplanar Waveguide Bandpass Filters

End-coupled resonator bandpass filters built in coplanar waveguide are investigated. The admittance inverter parameters of the coupling gaps between resonant sections are deduced from experiment, and bandpass filter design rules are developed. This allows easy filter synthesis from "prototype" low-pass designs. Measurements of single section resonator quality factors are used to predict filter insertion losses. Several examples of filters realized in coplanar waveguide are presented. Odd-mode coplanar waveguide filter elements that shortcircuit the even coplanar waveguide mode are investigated. Filter tuning, accomplished by adjusting the height of conducting planes above the resonant filter sections, is demonstrated.     

Circumferential Gap in a TE/sub 01/-Mode-Transmitting Multimode Circular Waveguide

Higher-order modes produced in a guide and fields radiated out of a guide by a circumferential gap in a multimode circular waveguide that is used for millimeter wave transmission, were investigated by means of fictitious equivalent magnetic current for the gap. These results were compared with the analysis obtained by Bethe's method, which was used for the problem of diffraction of fields by a small hole in a plane conducting sheet. The two results agreed well for narrow gap.     

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.     

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   

Design of Dielectric Waveguide Bandpass Filters Using Parallel-Coupled Gratings

Techniques for the design of narrow-band (of the order of a percent or so), bandpass filters using dielectric waveguide gratings are presented. These filters use both single, uncoupled gratings and parallel-coupled configurations of gratings to form multiresonator bandpass filter structures. Transmission-line equivalent circuits are used to model the dielectric waveguide gratings. Using this model, it is then shown how direct-coupled-resonator theory can be applied to such filter structures to synthesize a prescribed passband having Chebyshev or maximally flat characteristic. On the other hand, the parallel-coupled gratings give these filters broad and strong, absorptive stopbands, as is explained. Experimental results are presented which show good agreement between theoretical and measured results.