Experimental study of a flange mounted waveguide as a device for square radiation pattern

A slotted flange mounted on a waveguide has been studied for use as a feed with deep reflectors. TheE-plane patterns have large beamwidths and are reasonably square. A comprehensive device, consisting of a slotted flange mounted on a square aperture, has been designed and fabricated using the optimum slot width values of the slotted flange waveguide system. The amplitude, phase, and bandwidth characteristic of this device satisfy the requirements of a feed for deep reflectors.     

Radiation pattern computation of cavity-backed and probe-fedstacked microstrip patch arrays

In this paper, two different methods based on Floquet's harmonic expansion of the electromagnetic field in half-space are proposed to determine the active element pattern of infinite planar arrays. They allow us to obtain the radiating characteristics without the limitations of the conventional method from the active reflection coefficient. Both are applied to analyze the scan performance in the case of probe-fed and cavity-backed microstrip arrays from its generalized scattering matrix (GSM), computed previously with a full wave numerical procedure. Numerical results are presented and compared with other techniques     

Dipole antenna coaxially mounted on a conducting cylinder

The problem of a cylindrical dipole antenna symmetrically mounted on a conducting coaxial cylinder is analyzed both theoretically and experimentally. The theoretical approach is based on the Fourier transform solution for thin wire antennas, equivalence and image principles, point matching, and numerical optimization. The basic idea is that the modified dipole structure can be replaced by an equivalent system (as far as exterior fields are concerned) consisting of a simple perfectly conducting rod excited by an array of magnetic ring sources. The coefficients of these sources are then adjusted to match boundary conditions on the cylindrical modification surface. For the locations of the match points and sources, three gauges involving weighted integrals of the tangential electric fields are used to optimize the solution. Good agreements between measurement and theory have been obtained for the input admittances, resonance properties, and radiation patterns. Results are also presented for a dipole on a sphere to contrast effects due to change in modification shape.     

Radiation pattern synthesis for arrays of conformal antennas mounted on arbitrarily-shaped three-dimensional platforms using genetic algorithms

A domain-decomposition/reciprocity procedure is presented which allows the radiation patterns of microstrip patch antennas mounted on arbitrarily-shaped three-dimensional perfectly electric conducting (PEC) platforms to be computed accurately as well as efficiently. The utility of this technique is demonstrated by considering an example consisting of a nine-element conformal array of microstrip patch antennas mounted axially along a finite-length PEC circular cylinder. It is shown that the elements close to the ends of the cylinder have significantly different patterns than those close to the center of the cylinder. The results from this example suggest that the common practice where all the individual element patterns are assumed identical is not always valid and, in fact, can lead to significant performance degradation in the design of conformal phased arrays. This observation is supported by the fact that an attempt to steer the main beam of the nine-element conformal array to an angle /spl theta//sub 0/=60/spl deg/ using a standard uniform progressive phase shifting technique proves unsuccessful. Next a genetic algorithm (GA) synthesis procedure is introduced that is capable of determining the optimal set of element excitation phases required to yield a desired or specified far-field radiation pattern. The results of this GA phase-only optimization are shown to yield the desired main beam steered to the correct angle for this nine-element linear array mounted on a circularly cylindrical platform. The GA radiation pattern synthesis procedure introduced appears to be a highly effective means of correcting for platform effects on the individual element patterns of a conformal phased array.     

双极化方形微带天线的阻抗特性

在方形微带贴片的相邻两边电可以辐射双极化波。文中结合平面电路技术,腔模理论,用Ｇｒｅｅｎ函数法导出了双边馈电方形微带天线输入阻抗与互阻抗的计算公式,分析了Ｘ波段双极化方形贴片天线输入阻抗,Ｓ参数和电压驻波比在谐振频率附近的变化情况,以及馈电点位置与宽度和εｒ对这些特性参数的影响。文中的计算方法可靠而简捷,可用于此类天线的设计,这种天线容易形成阵列结构,并易于有源集成。     

Radiation from a homogeneous sphere mounted on a waveguide aperture

The results of an experimental and theoretical study of the effects of placing a dielectric sphere over the aperture of a circular waveguide are presented. A dielectric sphere excited by a Huygens' source is used us the theoretical model to interpret the experimental results. Calculations based on this model show good overall agreement with experimental patterns and directivity measurements. It is concluded that dielectric loaded antennas such as the dielectric sphere excited by a waveguide can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of two wavelengths or less. Measurements of the coupling between these antennas show that they, in general, are not as closely coupled as plain apertures without dielectric object loading.     

Monopolar square patch antennas with wideband operation

The design of a wideband patch antenna with monopole-like conical radiation patterns is presented. The antenna has a square patch that is shorted to the ground plane through two shorting walls and is excited by a top-loaded coaxial feed centred below the square patch. Several prototypes with various antenna heights are implemented and measured. A prototype with impedance bandwidth of about 50% is achieved when its height is less than 0.09 free-space wavelengths.     

Compact amplifier integration in square patch antenna

A packaged microwave bipolar transistor has been integrated directly onto a rectangular microstrip patch to obtain extra power gain and to reduce power losses. The radiating element geometry has been modified to incorporate the active devices. This active antenna uses a small number of components and takes the same place as a passive antenna. An extra gain of 8 dB is obtained at 1.68 GHz.<>     

新型的方形贴片双模微带带通滤波器

提出了一种新型的方形贴片双模微带带通滤波器。该滤波器结构有一个切角,并且在贴片中心处开了一个两臂等长的十字槽,采用正交直接馈电方式,并在每条馈线上引入了一节与谐振腔有一定耦合的开路短截线。该结构在上下阻带都产生衰减极点,馈线上引入的微带线有效地抑制了寄生通带,提高了阻带抑制特性。仿真结果表明,该滤波器在中心频率2.9 GHz处,回波损耗优于–30.9 dB,通带内最小插入损耗为–0.1 dB,与实测结果基本一致。     

Compact active polarisation-agile antenna using square patch

A polarisation-agile active patch antenna with a compact layout has been developed. Comprising a square patch with an overlay, it has two transistors in the common base configuration, connected on adjacent sides to excite orthogonal modes of oscillation. Circular polarisation of either sense, and linear polarisation parallel to either patch side or diagonal, can be radiated     

Radiation properties of terahertz dipole antenna mounted onphotonic crystal

Initial measurements are presented of a dipole antenna mounted on top of a photonic crystal structure at terahertz frequencies. The configuration and test setup are described. The dipole on top of the photonic crystal has higher directivity in contrast to a single dipole element. The ability of this technology to suppress surface waves is noted     

Experimental analysis of corner-fed printed square patch antennas

An experimental analysis is developed for the corner-fed printed square patch antenna, taking into account the width of the feeding junction and the proximity of the microstrip feedline. New accurate design relations for resonance frequency and input impedance are deduced, directly usable for the computer aided design of printed antenna arrays.<>     

Radiation frequencies of ferrite patch antennas

The radiation frequencies of rectangular microstrip patch antenna deposited on ferrite substrate have been measured. Two different radiation modes were found whose frequencies behaved differently under the application of a biasing magnetic field. These two modes of radiation have been identified with a transverse mode whose radiation frequency increased with increasing magnetic field and a longitudinal mode whose radiation frequency decreased with the applied magnetic field. A theoretical model has been formulated for radiation of these two modes based on a multidomain configuration of the ferrite substrate.<>     

Radiation modes in circular patch antennas

We have formulated exact solutions of the normal modes in the microstrip patch antenna possessing circular geometry. The theory makes use of a new Green's function in conjunction with current potential analysis. The calculations demonstrate that the magnetic wall confinement boundary conditions as formulated in past theories hold approximately true if the surface wave loss is minimal compared to other losses: dielectric loss, conductor loss, and radiation loss. For practical path antennas the normal modes are not confined locally near the microstrip patch. Rather, they are composed of propagation surface waves which extend far beyond the region containing the patch antenna. We term these normal modes as leaky modes, since they resemble the leaky modes found in dielectric image guides. Measurements by us of the radiation mode frequencies and the intrinsic Q-values of the microstrip patch antennas compared very well with theory     

Radiation characteristics of slotted oversize patch antennas

A novel integrated antenna with low loss and medium gain is designed. It is composed of a driven oversize slotted patch, backed by a metallic ground plane. Its radiation occurs from the slots and some of its edges. By a suitable optimisation, an excellent field distribution over the antenna aperture is obtained, that provides high gain and low crosspolarisation at far field     

Analysis and measurements of conformal patch array antennas on multilayer circular cylinder

In this paper, we present a method of moments (MoM) program to analyze different configurations of arrays of cylindrical-rectangular patches. The patches can be located inside or on the surface of a multilayer circular-cylindrical structure and can be arbitrarily rotated. The antenna structure is rigorously taken into account by using proper Green's functions, and the array is analyzed by using an element-by-element approach. The elements of the MoM matrix are calculated in the spectral domain, and special attention is given to their numerical treatment when analyzing cylindrical antennas with large radii. A laboratory model is built to test different configurations of patches and to validate calculated results. The agreement between measurements and calculations is very good.     

Equivalence of radiation properties of square and circularmicrostrip patch antennas

The radiation properties of a circular microstrip antenna are compared with those of an equivalent square microstrip antenna. On the basis of this comparison, a simple method of computing the far field of a circular microstrip antenna is suggested     

Radiation from multiple circumferential slots on a conductingcircular cylinder

Electromagnetic wave radiation from multiple circumferential slots on a conducting circular cylinder is theoretically investigated. The Fourier transform/series technique is used to represent the continuous and discrete modes of the scattered field. The mode matching is utilized to constitute a set of simultaneous equations for the discrete modal coefficients. The residue calculus is applied to transform the scattered field integral representations into fast-converging series forms, thereby facilitating the numerical computations. Numerical computations illustrate the behavior of radiation in terms of the slot geometry, the incident mode, and the operating frequency     

Circularly polarised truncated-corner square patch microstriprectenna for wireless power transmission

A circularly polarised rectenna using a truncated-corner square-patch microstrip antenna has been developed for wireless power transmission at 5.8 GHz. The gain and axial ratio achieved were 8.5 dBi and 0.5 dB at 5.82 GHz respectively. A GaAs Schottky barrier diode was employed for microwave to DC conversion with a maximum conversion efficiency of 60%