Analysis of microstrip antennas using moment methods

The method of moments is used to analyze microstrip antennas of rectangular and nonrectangular shape. Surface currents are used to model the microstrip patch and volume polarization currents for the dielectric slab. The method requires unusually precise computation of the impedance matrix but is capable of accurately predicting currents, impedance, and resonant frequency of the antenna.     

Design of multiple edge blinders for pyramidal horn reflector antennas

The design of multiple edge blinders for pyramidal horn reflector antennas is discussed. The blinders eliminate high sidelobes in the azimuthal plane near90degfor horizontal polarization at 4, 6, and 11 GHz. The successful design of multiple edge blinders for simultaneous operation in each of the three common carrier bands depends upon the suppression of an off-axis major lobe at 4 GHz and grating lobes which typically appear at 6 and 11 GHz. Using the blinder array factor and element pattern, it is shown that these lobes can be suppressed by properly choosing the blinder tilt anglebeta_{c}, the inclination of an individual blinder edgedelta, and an adequate number of edgesN.     

Near-field patterns from pyramidal horn antennas: numericalcalculation and experimental verification

The electromagnetic field close to a pyramidal horn antenna has been predicted using a numerical technique assuming a spherical phase front in the aperture of the horn. Comparison with experimental results using an infrared imaging technique has shown that the best fit is for a phase front that is 1.25 times more curved than a sphere. The infrared imaging method has been demonstrated to be very useful for mapping the fields in a region that is sensitive to the introduction of metallic probes     

Analysis of elliptical and circular microstrip antennas using moment method

A method of calculating the input impedance of either a circular or a slightly ellipitcal microstrip antenna excited by a coaxial probe is presented. Using the reaction integral equation and the exact dyadic Green's function, the finite substrate thickness is taken into account in the formulation. Good agreement with experimental results for an elliptical patch is obtained and a design procedure for a circularly polarized antenna is presented.     

Numerical modeling of ultrawide-band dielectric horn antennas using FDTD

A detailed characterization of the input impedance of ultrawide-band (UWB) dielectric horn antennas is presented using the finite-difference time-domain (FDTD) technique. The FDTD model is first validated by computing the characteristic impedance of two conical plate transmission lines (including planar bow-tie antennas) and comparing the results to analytical solutions. The FDTD model is next used to calculate the surge impedance of dielectric horn antennas using the conical plates as launchers. Design curves of the surge impedance for different choices of geometries and dielectric loadings are provided. The modeled antennas are particularly attractive for applications such as UWB ground penetrating radars (GPR) applications.     

Phase centers of horn antennas using Gaussian beam mode analysis

The power of Gaussian beam mode analysis to accurately describe the propagation of electromagnetic beams and the location of a horn antenna phase-center is illustrated. By way of example, the case of a compensated pyramidal horn fitted with fins to produce a less abruptly tapered E-plane field distribution is discussed, and the results obtained are compared with those from an alternative method published in the literature. Excellent agreement is found     

Analysis of rectangular horn antennas via uniform asymptotic theory

Approximate analytic expressions for the far-field radiation pattern and modal reflection coefficient of the three-dimensional horn antenna have been developed. Based upon a multiple-image model of the two-dimensional horn-waveguide structure, this approach offers greater generality than previously proposed ray analyses with comparable complexity and accuracy. The uniform asymptotic theory (UAT), which is employed throughout, provides information when this approach is valid for a desired degree of accuracy in the solution. It is demonstrated that, in most cases, the far-field pattern of the horn is reducible to the pattern of a simple slit in an absorbing screen illuminated by an array of patterned line sources. The measured patterns of several horns are convincingly recovered by the prediction of the analytical model. The same model is used to calculate the modal reflection coefficient of the horn-waveguide structure and, again, comparison with measured results is excellent.     

Soft and hard horn antennas

Horn antennas with soft and hard boundaries are analyzed. A soft boundary which exists in classical hybrid-mode horns gives zero field intensity at the wall. A hard boundary corresponds to a uniform field distribution over the horn aperture. Soft and hard horn antennas are compared with respect to directivity, sidelobes, and beamwidth. The dependency between the edge taper directivity, and sidelobes is also calculated based on the solution to the spherical hybrid modes in a conical horn with arbitrary wall impedances. This makes it possible to study how to compromise between directivity and sidelobes. Also discussed is how the different wall impedances may be realized, and some preliminary experimental work on hard horns is presented     

Gain enhancement of a pyramidal horn using E- and H-plane metalbaffles

A technique for enhancing the gain of a wide-flare angle pyramidal horn is described. The gain of the antenna is increased by placing simple metal strips or baffles inside the horn near its throat. Two baffles, an E- and an H-plane baffle, are described and analyzed. The baffles are first analyzed through two-dimensional (2-D) numerical calculations and then through measurements in an experimental X-band horn. Each baffle enhances the antenna's gain in the respective plane. When the baffles are implemented together the gain enhancement is additive in decibels. The numerical calculations and measurements show that baffles can he used to significantly reduce the size of pyramidal horn antennas     

New types of dielectric-loaded horn antennas

This paper presents low-loss dielectric loading techniques for improving some of the radiation characteristics of H-plane horn antennas. Specifically, the paper reports experimental results over new horns loaded with dielectric in the transverse and longitudinal planes with and without air gaps between the dielectric layers or between the dielectric and metallic walls. Sample results are presented showing improvements in the beam width, axial gain, input voltage standing wave ratio (VSWR) at the expense of new or increased side lobe level at some frequencies within the passband. Results are also presented to show that the main beam of a novel dielectric-loaded horn can almost be scanned from one wall of the horn to the other in synchronism with frequency sweep within the passband. Finally, a line-of-sight portable communication device employing the characteristics of dielectric-loaded horn antennas is proposed for further research and development.     

Pattern analysis of corrugated horn antennas

The corrugated horn has been established as an antenna with low sidelobes and backlobes, rotationally symmetric patterns (for square pyramidal and conical horn shapes), and broad-band performance [1]-[9]. These properties make this horn useful for many applications. Previous studies have used conventional aperture integration techniques to evaluate the patterns of the corrugated horn. In general, the near axisE-plane radiation pattern of a pyramidal corrugated horn may be adequately predicted from standard analysis established for theH-plane patterns of conventional horn geometries [3]. This method, however, fails to predict the far-out sidelobe and backlobe radiation levels. The work presented here uses a knowledge of the aperture fields to predict the pattern using aperture integration and diffraction theory. The assumptions made concerning the aperture fields were verified by probing the internal fields and aperture fields of anXband corrugated horn. The results of this field probing are contained in the Appendix. The method of solution used in this paper parallels that used in previous publications [10]-[12]. Specifically, the pattern in the main beam region is computed using conventional aperture integration procedures, the contribution of theH-plane edges is found using a slope diffraction analysis, and the contribution of theE-plane edges is found by use of duality.     

The phase center of horn antennas

The calculation of phase centers for rectangular and diagonal horns is presented. The calculation is based on a vector approach, by deriving the phase center from the expressions for the far field. Different expressions are derived for the phase center of theEandHplanes. The phase center for an arbitrary plane is calculated from theE-andH-plane phase centers. Graphs are presented showing the dependence of the phase centers on horn dimensions.     

Radiation characteristics of dielectric-loaded horn antennas

The radiation characteristics of electromagnetic horns loaded with curved transverse dielectric slabs and radial dielectric strips are investigated experimentally. It is shown that the axial directivity and halfpower beamwidth of horn antennas may be significantly improved with such schemes of dielectric loading.     

Integrated horn antennas for millimeter-wave applications

The development of integrated horn antennas since their introduction in 1987 is reviewed. The integrated horn is fabricated by suspending a dipole antenna, on a thin dielectric membrane, in a pyramidal cavity etched in silicon. Recent progress has resulted in optimized low- and high-gain designs, with single and double polarization for remote-sensing and communication applications. A full-wave analysis technique has resulted in an integrated antenna with performance comparable to that of waveguide-fed corrugated-horn antennas. The integrated horn design can be extended to large arrays, for imaging and phased-array applications, while leaving plenty of room for the RF and IF processing circuitry. Theoretical and experimental results at microwave frequencies and at 90 GHz, 240 GHz, and 802 GHz are presented     

94 GHz integrated horn monopulse antennas

A monolithic azimuthal monopulse antenna for 94-GHz applications has been developed. The structure consists of a single dipole suspended in one plane of an integrated horn cavity to obtain the sum pattern, and an antiparallel pair of dipoles suspended in a different plane of the same horn cavity to achieve the difference pattern. Pattern measurements of microwave models and on the millimeter-wave antennas show good agreement with theory and exhibit symmetry with a sharp -30-dB null at broadside for the difference antenna. Microwave model measurements show input impedances close to 50 Ω, with greater than -25-dB isolation between sum and difference antennas across a 10% bandwidth     

Integrated horn antennas for millimeter-wave applications

This paper reviews the development of integrated horn antennas since their introduction in 1987. The integrated horn is fabricated by suspending a dipole antenna on a thin dielectric membrane in a pyramidal cavity etched in silicon. Recent progress resulted in optimized low and high-gain designs with single and double-polarizations for remote-sensing and communication applications. A fullwave analysis technique have resulted in an integrated antenna with performance comparable to that of waveguide-fed corrugated horn antennas. The integrated horn design can be easily extended to large arrays for imaging and phased array applications while still leaving plenty of room for the rf and w processing circuitry. Theoretical and experimental results at microwave frequencies and at 90, 240 and 802 GHz will be presented.     

92 GHz dual-polarized integrated horn antennas

A dual-polarized two-dimensional imaging array was designed for millimeter-wave applications. The dual-polarized design consists of two dipoles perpendicular to each other and suspended on the same membrane inside a pyramidal cavity etched in silicon. The dual-polarized antenna is fully monolithic with room available for processing electronics. The IF or video signals are taken out through a novel bias and feeding structure. The measured polarization isolation is better than 20 dB at 92 GHz, and the orthogonal channels show identical far-field patterns. The antenna is well suited for millimeter-wave polarimetric synthetic aperture radars (SARs) and high-efficiency balanced-mixer receivers     

宽频带角锥脊喇叭天线的设计方法

主要研究了角锥脊喇叭天线的工作原理,给出了脊波导的截止波长、特性阻抗;提出了一种脊喇叭天线的设计方法,并运用该方法给出了设计实例。最后给出了实际测试曲线,验证了设计的正确性。