Sidelobe suppression in an E-plane sectoral horn antenna

A finite-difference method is used to design a sectoral horn antenna that uses corner channel inserts to produce a tapered aperture amplitude distribution in the E-plane. The channel inserts effectively suppress sidelobe levels in the radiation pattern. Good agreement is found between predicted and experimental far-field distributions.<>     

Near-field analysis of E-plane sectoral solid dielectric horn antennas

An approximate analysis of the aperture field of an E-plane sectoral solid dielectric horn antenna is described using the TE to x mode. The analysis is based on the solution of Maxwell's equations after making some simplifying assumptions. The electric and magnetic fields inside the horn core are matched to those outside at appropriate boundaries to yield transcendental equations which are then solved on a computer for the ropagation constants and field configurations. The theoretical results so obtained are in agreement with experimental results. Characteristic equations for the TM to x mode are also calculated and the results are compared with those of Marcatili, Goell, Eyges and Morita     

Radiation pattern of E-plane sectoral solid dielectric horn antennas

Radiation patterns of an E-plane sectoral solid dielectric horn excited by a rectangular metallic waveguide are predicted and compared with patterns measured at 9-37 GHz.     

Microstrip line directional couplers with high directivity

Novel uniplanar backward directional couplers are analysed and designed. Microstrip parallel coupled lines and asymmetrical delay lines enable a multi-sectioned coupler to enhance directivity as well as the coupling. Single and multi-sectioned couplers at 1.8 GHz have been designed and measured, providing excellent directivity.     

Comprehensive analysis for E-plane of horn antennas by edge diffraction theory

Edge diffraction theory is used in analyzing the radiation characteristics of typical horn antennas. The far-sidelobe and backlobe radiation has been solved without employing field equivalence principles which are impractical in the problem. A corner reflector with a magnetic line source located at the vertex is proposed as a model for the principalE-plane radiation of horn antennas. A complete pattern, including multiple interactions and images of induced line sources, is obtained in infinite series form. Diffraction mechanisms are used for appropriate approximations in the computations. The computed patterns are in excellent agreement with measured patterns of typical horn antennas. Radiation intensity of the backlobe relative to mainlobe intensity is obtained as a back-to-front ratio and plotted as a function of antenna dimensions.     

Radiation characteristics of a dielectric sphere loaded corrugated E-plane sectoral horn

The experimental results of the radiation characteristics of a dielectric sphere in front of a corrugatedE-plane sectoral horn together with the design aspects of the horn are reported. The experiments were carried out with the test antenna system consisting of dielectric (paraffin wax) spheres kept offset at the minimum input VSWR position in front of the horn excited in the balanced HE11mode. The test results have shown that such a feed system produces radiation patterns with reduced sidelobe levels and increased on-axis gain with reduced 3-dB beamwidths as compared to the same horn radiating in free space. The feed system may also produce a low input VSWR and can be used as a variable beamwidth feed for praraboloidal reflectors.     

Short cylindrical antennas with enhanced radiation or high directivity

The feasibility of enhancing the radiated power or improving the directivity of a short cylindrical antenna by double impedance loading is investigated. An approximate solution for the current on a doubly loaded short antenna is developed, and typical current dlstributions, impedances, and radiation patterns of antennas appropriately loaded to implement enhanced radiation or high directivity are presented. Significant improvements in radiated power or directivity can be achieved with optimum impedance loadings. Theoretical predictions are verified by the results of an experimental study.     

Optimization of the symmetric E-mode horn profile for a performance directivity pattern

The rigorous theory of excitation of an irregular electrodynamic system is used to formulate and solve the problem of determining the profile of a horn operating on symmetric E modes that provides a required mode structure at the output and an optimum directivity pattern.     

A synthesis of array antennas for high directivity and low sidelobes

By application of a Gegenbauer polynomial, pattern synthesis of array antennas which have high directivity and low sidelobe level is investigated. A Chebyshev or uniform-amplitude array is included as a special case of the result obtained. The current amplitudes of the array elements are represented by a Jacobi polynomial and are easily calculated. It is shown by numerical calculations for a linear array and a hexagonal planar array that there is an optimum directivity for a specified sidelobe level within a class of Gegenbauer-polynomial patterns.     

Domain decomposition FDTD algorithm for the analysis of a new type of E-plane sectorial horn with aperture field distribution optimization

In this paper, a universal and efficient approach of domain decomposition finite-difference time-domain FDTD (DD-FDTD) is presented for the analysis of a new type of horn antenna-E-plane sectorial horn with field amplitude taper and phase correction in the aperture. The power fed into the horn is redistributed to achieve the optimal field amplitude distribution in the aperture, and meanwhile the field phase is corrected by metal lens. Compared with conventional E-plane sectorial horns, the new horn antenna takes the advantages of low sidelobe level, short physical length and wide flare angle etc. Moreover, the most important property of this horn is the weak coupling with each other when it is used as the element of a phased array antenna. The field analysis of such a horn antenna is an extremely complicated three-dimensional EM boundary value problem. The domain decomposition FDTD method is presented in this paper to break through the drawback. The whole horn is decomposed into several subdomains and the meshes are created in local coordinates. In the iteration procedure of FDTD, the data are exchanged between adjacent subdomains with overlapped meshes. The aperture field distribution, voltage standing-wave ratio and pattern calculated by the DD-FDTD method are in good agreement with the experimental data.     

Directional coupler with high directivity using metallic cylinders on microstrip line

A directional coupler with high directivity performance using metallic cylinders on the microstrip line is presented. By using two rows of periodic metallic cylinders on a microstrip coupler, the odd-mode phase velocity is slowed down, and thus the directivity can be greatly improved for equal odd- and even-mode phase velocities. The parameters of metalised cylinders, which have an effect on the coupler performance, are investigated. A 12 dB coupler at 2.41 GHz has been designed and measured, providing excellent directivity. Theoretical and experimental results are presented.     

一种平面结构的宽带E面全向天线

设计了一种平面结构的宽带天线,此天线由四个改进的T型偶极子加馈电网络构成,在其辐射的E平面可以实现全向特性,在3～5.5 GHz范围内其回波损耗小于-10 dB,实测方向图E面不圆度小于3 dB,且增益大于0dBi.     

Optimized E-plane bandpass filters with improved stopbandperformance

A computer-aided synthesis technique for E-plane bandpass filters with improved stopband performance is developed. An optimization procedure based on equal ripple optimization is adopted. The design of a symmetrical E-plane bandpass filter with improved stopband performance is considered; higher order mode interaction between E-plane discontinuities is included in the design. The predicted filter performance shows improved stopband performance and reduced filter dimensions compared with conventional E-plane bandpass filters. The validity of the method is confirmed by the measurement of a fabricated five resonator E-plane bandpass filter with improved stopband performance     

A high gain dielectric loaded biconical horn for circular polarization

The experimental results of the radiation characteristics of a dielectric loaded biconical horn which radiates circular polarization are presented. The test horn was designed to radiate circular polarization in theXband. It is seen that the pattern directivity of the biconical horn in the vertical plane is significantly increased due to dielectric loading, and a desired beamwidth in the vertical plane may be obtained by a suitable dielectric loading.     

A simplified CAD of millimeter-wave diplexer with E-plane T-junction and all-metal insert filters

An equivalent circuit theory design of a class of rectangular waveguide E-plane T-junction diplexer with E-plane all-metal insert filters is presented. Element values of equivalent circuit models of E-plane T-junction proposed in [1] are computed and approximated. The parameters of the filters designed by [2] are also given. By use of the network combining technique, the scattering matrix of the diplexer is obtained and optimized according to the diplexer specification with a novel objective function. The experimental results show a fairly good agreement with the computed results.     

Microstrip couplers with improved directivity

Backward wave microstrip couplers with weak coupling reach small values for the directivity. This is caused by the unequal phase constants of the even and odd modes of the line waves. A very simple compensation method is shown by loading the coupler with additional coupled lines.     

A universal method for directivity synthesis

A completely new synthesis method, the successive approximation method, is developed. By introducing a control function and a step-by-step approach program various directivity functions can be obtained in which the peaks of the sidelobes and specified zeros fit within a specified curve. This method is applicable to any form of array. Numerical calculations have been done to illustrate its applications: determining optimum current distribution of linear arrays, unequally spaced arrays, steering the main beam through current excitation, etc.     

E-plane cross junction loaded with central metallic post

The Least-Squares Boundary Residual Method is utilized in the present paper for the analysis of the E-plane cross junction that has a centrally located metallic post. The computer model thus developed (which is able to yield numerical accuracies of ±0.5%) has thereafter been used to design a prototype that has the same electrical characteristics over the 26–40 GHz bandwidth as the H-plane cross junction reported earlier by Suet al in [1].     

Compact W-band E-plane Waveguide Filter with High Selectivity

Journal of Infrared, Millimeter, and Terahertz Waves - In this letter, an E-plane substrate is inserted into the W-band standard waveguide to construct a bandpass filter (BPF) with high...     

Shaped wire antennas with maximum directivity

The optimum shape of a wire antenna for maximum directivity is obtained by applying the method of moments and the simplex method for function minimisation. Antenna shape is approximated by piecewise parabolas, and the effects of wire radius on current distribution are considered.