A Coaxial Wavewide Commutator Feed for a Scanning Circular Phased Array Antenna

A coaxial waveguide amplitude commutation feed system has been developed for application to the scanning circular array antenna problem. A dominant TEM mode and a pair of orthogonal TE/sub 11/ modes suitably excited at the input of a coaxial waveguide feed are employed to generate a simply commutatable low-sidelobe discrete amplitude distribution at the peripheral output ports of the coaxial circular array feed. The major advantages of the coaxial commutator feed compared to other circular array feed types are the broad bandwidth and small insertion loss simultaneously achieved with a simple feed geometry. The design and measured performance capability of a 30-percent RF bandwidth low-sidelobe coaxial commutator feed are described in detail.     

Circularly polarised mode-converting antenna

A novel mode converter that transforms coaxial transverse electromagnetic mode into circularly polarised coaxial TE/sub 11/ mode is proposed by inserting several metal plates into the coaxial waveguide. A circularly polarised mode-converting antenna with length of 36 cm and aperture diameter of 30.8 cm is designed by combining the mode converter with a special conical horn. The antenna has a gain of 19.2 dBi with an aperture efficiency of 50% and an axial ratio of 1.2 at 4 GHz. Measured results agree well with the simulated ones.     

High-performance circular TE/sub 01/-mode converter

This study presents the design and cold testing of a Ka-band TE/sub 01/-mode converter. A wave is efficiently converted from the TE/sub 10/ rectangular waveguide mode into the TE/sub 01/ circular waveguide mode. This converter comprises a power-dividing section and a mode-converting section. The field pattern and the working principle of each section are analyzed and discussed. A prototype was built and tested. Back-to-back transmission measurements exhibit excellent agreement to the results of computer simulations. The measured optimum transmissions are 97% with a 1-dB bandwidth of 5.8 GHz centered at 34.0 GHz. The angle-independent transmissions manifest high mode purity and the field pattern is directly demonstrated on a temperature-sensitive liquid-crystal sheet. In addition to exhibiting a high conversion efficiency, high mode purity, and broad bandwidth, this converter is also easy to construct and is structurally simple.     

A Novel TM$_01$–TE$_11$Circularly Polarized (CP) Mode Converter

A novel mode converter that converts a$hboxTM_01$mode to a CP$hboxTE_11$mode was developed. In the converter, the$hboxTM_01$mode is transformed into a coaxial transverse electric and magnetic (TEM) mode first, then the coaxial TEM mode is split in space into multiple$hboxTE_11$sector waveguide modes by eight plates in the coaxial waveguide, which further subject the$hboxTE_11$sector waveguide modes to different signal paths and hence effectively convert the TEM mode into a CP$hboxTE_11$mode. A mode converter at 4GHz was designed. The conversion efficiency of$hboxTM_01$-to-$hboxTE_11$is 99% at center frequency with an axial ratio of 0.7dB. Over the frequency range of 3.8–4.3GHz, the conversion efficiency exceeds 90%, and the axial ratio is less than 2.7dB. A good agreement between experiments and simulations was observed.     

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   

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.     

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.     

Input Impedance of Coaxial Line to Circular Waveguide Feed

The expressions for the real, imaginary parts of the input impedance seen by a coaxial line driving a thin cylindrical probe in a dominant TE/sub 11/ mode circular waveguide are derived. The analysis is carried out by assuming that the cylindrical post is replaced by a curvilinear strip having maximum width equal to the diameter of the probe. Theoretical results on input VSWR and input impedance seen by a coaxial line are in close agreement with experimental data.     

An L-Band Loop-Type Coupler (Correspondence)

The design of loop couplers for various loop length has been reported by Lombardini, Schwartz and Kelly. This device is useful for many applications as the over-all length can be held to about 6 inches, whereas a com-parable multihole coupler must be on the order of several feet long. The loop-type device couples a TE/sub 10/ waveguide mode from a RG-69/U to a TEM mode in a 3/8-inch coaxial line. A comb-type coupler, for coupling a coaxial line to TE/sub I0/ waveguide, was reported by Lombardini and Schwartz. This device made use of a multiple-capacitive probe situated in a longitudinal slot in the top wall of the waveguide.     

Resonant Frequency of Open-Ended Cylindrical Cavity

The TE/sub 011/ mode of oscillation in an open-ended circular cylindrical microwave cavity is analyzed. The cavity consists of a circular waveguide that is terminated at each end with a thin cylindrical partition coaxial with the circular waveguide. The resonant frequency of the cavity is computed by using Laplace transform and Wiener-Hopf techniques. Numerical values for the resonant frequency are presented.     

On the Mode and Square Correspondence Between Circular Multimode Tapered Waveguides

In an axially straight multimode circular waveguide taper excited with a pure TE/sup /spl circle// /sub 11/ dominant mode, the first and only converted mode at and near cutoff is the TM/sup/spl circle// /sub 11/ mode. It is shown that in an axially straight multimode square waveguide taper excited with a pure TE/sup/spl square// /sub 10/ dominant mode, the TM/sup/spl square// /sub 12/ mode corresponding to the TM/sup/spl circle// /sub 11/ mode in circular case is not the only first converted mode at and near cutoff. The overall behavior or coupling mechanism of waveguides is similar whether the waveguide is rectangular, square, circular, or elliptical: i.e., the overall coupling coefficient at cutoff of a converted mode or modes approaches an ininfinity of the order 0/sup -1/4/.     

Theoretical investigation of an advanced launcher for a 2-MW 170-GHz TE/sub 34,19/ coaxial cavity gyrotron

This paper investigates the antenna waveguide (launcher), the main component of the quasi-optical mode converter of a 2-MW 170-GHz TE/sub 34,19/ coaxial cavity gyrotron, which is under development within the European Union. For coaxial gyrotrons operating in very high-order cavity modes like the TE/sub 34,19/, due to the ratio of the caustic to cavity radius of 0.323, the transformation of the high-order cavity mode into a nearly Gaussian distribution cannot be done as good as for gyrotron modes where the ratio of caustic to cavity radius is approximately 0.5. The simulation results for the TE/sub 34,19/ mode show that the average and peak values of the power density at the edges of the cuts of a conventional dimpled-wall launcher are approximately 32.3 W/cm/sup 2/ and 63.8, respectively, which will produce diffraction losses and reflection of power from the cuts. This paper reports on an advanced launcher for which average and peak values of power density of 1.9 and 5.4 W/cm/sup 2/ at the edges of the cuts are achieved, and a well-focused field at the aperture with a scalar Gaussian mode content of 94.8% is obtained.     

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 of an End Launcher for a Circular Cylindrical Waveguide

The analysis of an end launcher type of transition exciting dominant TE/sub 11/ mode circular waveguide from a coaxial line is presented. The expressions for real and imaginary parts of impedance seen by the coaxial line are derived for the general case of offset launcher using self reaction of the assumed current over the loop. The dimensions of combined electric and magnetic loops having low input VSWR are determined. There is satisfactory agreement between theoretical and experimental results.     

一种使用TE11为过渡模的TE01-HE11模式变换器设计

基于弯曲圆波导耦合理论和规则圆波导突变结构模式匹配法, 利用MATLAB软件编写的相关数值计算程序得到波导模式转换结构的优化参量, 最终使用CST软件对模型进行了仿真和验证.该系统主要由三部分组成: 一个TE01-TE01的过渡器, TE01-TE11和TE11-HE11的圆波导模式转换器.计算结果表明, 该TE01-HE11模式转换系统在24.13 GHz的频率有5%的带宽、转换效率超过了99%.计算结果、仿真结果和实物冷测结果是一致的.     

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 mode transformer using fin-line array for spatial power-combiner applications

A new TE/sub 10/-to-TE/sub 20/-mode transformer has been developed on the basis of a fin-line array for waveguide spatial power-combiner applications. The fin-line array is designed such that the input TE/sub 10/ mode is split in space into multiple segments, then subject to different signal paths, which effectively converts the TE/sub 10/ mode into a TE/sub 20/ mode, while eliminating the TE/sub 10/ mode at the output. Our Ku-band (14-15 GHz) design indicates that the proposed mode converter makes it possible to obtain the TE/sub 20/ mode with greater than 22-dB suppression of the TE/sub 10/ mode over the band of interest. This converter was used in the design of a waveguide spatial power amplifier involving four monolithic microwave integrated circuit power chips and an output power of 31 dBm has been obtained with a combining efficiency of 80%. A measurement technique has been also developed to measure the electric-field profile inside the rectangular waveguide. A good agreement between measured and simulated results has been observed, showing an effective suppression of the TE/sub 10/ mode, as well as a good TE/sub 20/-mode formation judging from its amplitude and phase.     

同轴TE_(11)~⊙模与矩波导TE_(10)模的耦合计算

首先建立同轴 TE1 1 ⊙ 模与圆波导 TE1 1 o 模的等效关系。进而将同轴 TE1 1 ⊙ 模与矩波导 TE1 0 模的耦合问题转化为其等效圆波导 TE1 1 o 模与矩波导 TE1 0 模的耦合问题。实验证明 ,理论计算与实测结果吻合     

Bandwidth Enhancement in Dielectric-Lined Circular Waveguides (Short Papers)

The increase in TE/sub 11/-TM/sub 01/ mode bandwidth obtained by inhomogeneously loading (dielectric lining) a circular waveguide is systematically documented. Maximum bandwidth is about 31.83 percent of center frequency (up from about 26.54 percent for fully filled or empty circular waveguides). This makes circular waveguides competitive with square waveguides (bandwidth/spl aprox/ 34.3 percent) as radiators in wide-band dual-polarization arrays. Certain interesting symmetries involving the TE/sub 21/-TM/sub 01/ modal inversion are also examined.     

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.