Quadruple ridge-loaded circular waveguide phased arrays

An equivalent circuit representation of quadruple ridge-loaded waveguide arrays is presented which is useful for synthesis and optimization of array performance. The validity of this technique has been verified by simulator measurement.     

Aperture matching of a dielectric loaded circular waveguide elementarray

An X-band phased array with dielectric-loaded circular waveguide elements was investigated. The aperture was designed to provide balanced scan characteristics for both the E- and H-planes. The results of an experimental study are presented in which the active impedance of the radiating element was matched by introducing a circumferential groove onto the dielectric plug. Both the aperture junction and the matching groove were measured to derive their respective equivalent circuits for `look-in' and `look-out' impedance transformations. The groove size and its location from the aperture were then optimized by a hybrid approach wherein the measured data and computer simulations were used to greatly reduce the shop time, lab tests, and the number of trials in the hardware development     

EBG对圆波导介质棒相控阵扫描特性的改善

将电磁带隙(EBG)结构应用到圆波导介质棒相控阵列中,利用EBG结构所具有的表面波带隙特性有效消除了相控阵中的扫描盲区.比较了无限阵列的扫描特性和有限阵列中心单元方向图在EBG加载前后的变化.仿真分析表明,以EBG结构作为圆波导介质棒相控阵的地平面,能有效消除扫描盲区,扩展扫描范围.     

E-mode cutoff wave number of circular waveguide loaded with dielectric sector

The E-mode cutoff wave numbers of circular waveguide loaded with dielectric sectors were evaluated theoretically using the null-field formulation. These values are found to agree closely with cutoff wave numbers measured by using the transverse resonance technique.<>     

EBG结构在介质覆层波导缝隙相控阵中的应用

针对加载天线罩对于波导端头缝隙相控阵的天线性能和扫描盲点起到的恶化作用,提出了在阵面缝隙单元间加载EBG周期单元结构的方案,该方案结合了加载天线罩阵列缝隙之间的耦合特性以及EBG周期结构的抑制表面波特性,通过典型实例的数值仿真验证,消除了加载天线罩阵列的扫描盲点,展宽扫描范围,改善了天线阵的性能.     

Analysis of periodic arrays of waveguide apertures on conducting cylinders covered by dielectric

The analysis of infinite arrays of waveguide apertures on cylinders covered by a dielectric is approached by enforcing the continuity of the EM fields at the air-dielectric and at the dielectric-cylinder interfaces. The continuity of the EM fields at the first interface is enforced by representing the fields in the air and in the dielectric by an orthonormal set of modes LSE and LSM with respect to the radial direction. The matching of the fields at the second interface is performed by resorting to the "eigenexcitation" method [1]. The fields external to the cylinder are represented by a set of space harmonics matching the symmetry of the excitation of the array and the fields in the waveguides by a superposition of normal waveguide modes. The continuity of the fields is approximately enforced by using Galerkin's method. The rigorous analysis of these structures leads to rather involved expressions for the element driving point admittance and for the far fields. An approximate analysis is introduced to simplify the design of these structures for cylinders of large radius. Numerical examples illustrate the good approximation given by the simplified analysis. Numerical results are presented for the case of an array on a cylinder with radius approximately100lambda. The array element pattern shows the presence of resonance dips much more pronounced than the notches due to grating lobe phenomena.     

Propagation and radiation characteristics of dielectric loaded corrugated dual-frequency circular waveguide horn feeds

Based on a systematic analysis the design and experimental studies on a composite dual-frequency feed with a single radiating aperture are presented. The criterion for selecting the ratio of the diameter of the corrugated guide excited at the lower frequency in the dominant mode to that of the dielectric rod, axially located within the guide and excited at the higher frequency in the dominant mode, is discussed. The constructional features of a typical dual-frequency feed designed for operation atSandXbands (with 2.68 GHz and 9.375 GHz as center frequencies, respectively) are outlined. The measured radiation patterns show good symmetry and sidelobe suppression over 20-percent bandwidth inSandXbands and are in good agreement with calculated patterns.     

Multielement phased array waveguide simulator for circular polarization

An extension of the principles of multimode phased array waveguide simulators to triangular spaced array antennas is presented. It is also shown how such a simulator can be used for any polarization of excitation, if the radiating elements are circular symmetric. Contour plots of the reflection and the transmission coefficients are shown for circular polarization of excitation. The radiating elements are open-ended circular waveguides in a triangular lattice. A comparison between the simulator technique and the small test array technique to approximate the infinite array performance is also given.     

矩形波导有限相控阵单元的阵中特性

利用矩时法对以矩形开口波辐射单元的有限相控的单元阵中方向图及口面磁流分布进行了计算。讨论了不同位置开口波导在不同扫描角时互耦对口面分布的影响。     

Analysis of circular waveguide arrays on cylinders

An analysis is given of the mutual coupling effects in a finite array antenna of circular waveguide elements on a conducting cylinder. The array is described in terms of a scattering matrix and the multimode aperture fields of the elements are solved for by moment methods. Mutual coupling through wave propagation along the surface is treated according to GTD, since for most cases of interest the surface curvature is small in terms of wavelength. Appropriate asymptotic expansions for the magnetic field Green's function are derived for the two basic cases of an axial and a circumferential magnetic current element on the cylinder, the latter being a new case. The method, which allows the array elements to be nonuniformly spaced, applies to cylinders with radii>2lambdaand thus also includes planar arrays. Illustrative numerical examples and comparisons with infinite cylindrical and planar arrays are included.     

Analysis of finite phased arrays of circular microstrip patches

A method is presented for analyzing a finite planar array of circular microstrip patches fed by coaxial probes. The self- and mutual impedances between array elements are calculated using the method of moments with the dyadic Green's function for a dielectric layer on a ground plane. The patch circuits are determined by using the reaction integral equation. The active input impedance as well as the active element pattern of the array are computed from a knowledge of the resultant patch currents. The calculated results for two-element and eight-element linear arrays are in good agreement with experimental data. The active reflection coefficient and element pattern for the center and edge elements of a two-dimensional array as a function of scan angle are also presented     

Multiply driven and loaded coaxial circular loop arrays

Characteristics of single- or double-loaded coaxial loop arrays with arbitrary circumferences are studied when the sources or loads are located diagonally on the loops. For finite gaps at the deriving points and finite lengths of the loads, integral equations for the loop currents are obtained. These integral equations are then reduced to a matrix one by expanding the currents and the kernel in Fourier series of the azimuthal coordinate. For the special case of loaded Yagi arrays numerical results for the gain and the input impedance are presented. These results reveal that a capacitive loading of the array generally broadens the gain bandwidth of the array over which the gain remains essentially constant. A resistive loading of the exciter, on the other hand, yields a broadband characteristic for the driving-point admittance.     

Gain enhancement of dielectric resonator loaded waveguide antennas with dielectric overlays

The gain characteristics of a dielectric resonator loaded coaxial fed circular waveguide antenna (DRLWA) with overlaying parasitic discs have been investigated experimentally. Results indicate that, when properly spaced, the overlays can enhance the gain by more than 6 dB.<>     

基于时域有限差分法填充介质梯形脊波导研究

为了研究填充介质对脊波导截止特性的影响,文章采用FDTD(时域有限差分)法计算了填充介质梯形双脊波导在TE(横电波)模式下的截止特性随几何尺寸的变化,并给出了关系曲线。结果表明,脊间距越小,填充介质的相对介电常数越大,截止波长越长,单模带宽越窄。研究结果丰富了现存填充介质波导数据,有助于填充介质波导的设计和工程应用。     

90° dielectric polariser in circular waveguide

Experimental results for a 90° dielectric polariser in a circular waveguide are presented. A small slot notched into the circular waveguide wall, used for the accurate alignment of the dielectric plate, has led to a decrease in the relative phase shift by 15.7%. A new U-shape impedance matching structure results in bandwidth of 12.4%     

基于波导间隔余弦分布的光学相控阵研究

为了提高稀疏光学相控阵的精度和效率，采用输出波导间隔成余弦分布的结构，基于绝缘体上硅平台设计出1×16光学相控阵; 结合有效折射率法和2-D有限差分传播法进行了远场强度分布仿真模拟。结果表明，边瓣抑制比从89.72%减小到41.46%，主瓣半峰全宽从1.20°被压缩到0.81°; 这种设计方法能够显著抑制栅瓣，进一步压缩主瓣。该研究在机器人避障、无人驾驶、目标探测等光束偏转领域将有广泛的应用前景。     

Resonant frequency of circular microstrip antenna covered with dielectric superstrate

A simple design formulation to compute accurate resonant frequencies of circular microstrip antennas covered with dielectric superstrates is proposed. It alleviates the rigorous mathematical analyzes and large computational time of some earlier works. This theory is widely applicable to both high and low dielectric constant superstrates as verified with the experiments and other theoretical models. Of all theories, the present one shows the closest approximation with the measurements revealing average percent error as low as 0.52%. The extension of this formulation to predict the accurate design data for conventional microstrip circular antennas are also verified with different experiments and available improved theories for various sets of antenna parameters.     

Symmetrical N-port waveguide junction loaded with dielectric sleeveand metallic post

The present paper describes the development of a computer model that is able to predict the characteristics of the symmetrical N-port waveguide junction, which has a dielectric sleeve and metallic post inserted concentrically into its central cavity. Computational and experimental test results demonstrate that the resultant software package (which is compact enough to be run on an IBM 486 PC) can yield accuracies of ±0.5% for the scattering parameters of the junction     

A spherical scatterer inside a circular hollow dielectric waveguide

A theoretical investigation is presented of scattering characteristics of a perfectly conducting spherical object placed inside a quasi-optical transmission line of the millimeter and submillimeter waves in the form of a circular hollow dielectric waveguide (HDW). From the analytical expressions obtained, backscattering and extinction cross sections of this object are derived via the excitation coefficient of the dominantHE ₁₁ mode of the circular HDW and the HDW geometrical parameters. The agreement of the results with the corresponding data for the scattering of a plane homogeneous wave is shown.     

Element pattern approach to design of dielectric windows for conformal phased arrays

Modal analysis is presented for the realized element gainE- andH-plane patterns for a two-dimensional circular cylindrical arrays with concentric dielectric sleeve. Numerical results indicate presence of significant surface wave effects. A design method of dielectric windows to reduce the guided wave effects is proposed. The method, validated by direct evaluation of the element pattern for the optimized window geometries, shows significant reduction of surface wave effects.