Toward Improved Control of Medium Wave Directional Arrays

Relatively few types of variable power division circuits have been used in medium wave directional antenna feed systems, most of which suffer phase variation as the power division is adjusted. This paper discusses a class of circuits which can be used to implement a phase invariant adjustable power divider. Also discussed are variable phase shifters which have limited effect on power distribution. These features can simplify the original tuning and possible periodic maintenance. A computer analysis of the probable performance of such devices is presented. The associated problem of system analysis is discussed, particularly the inclusion of the effects of the antenna element coupling. To this end a lumped passive element model for a generalized linear reciprocal N port is presented.     

Design of wide-band aperture-stacked patch microstrip antennas

A variation of the aperture-coupled stacked patch microstrip antenna is presented, which greatly enhances its bandwidth. Bandwidths of up to one octave have been achieved. The impedance behavior of this antenna is compared with that of other wide-band microstrip radiators. Matching techniques for the antenna are presented and their relative merits discussed. The effects of varying several key physical parameters of the antenna are investigated, lending some insight into its wide-band operation. Variations on the design such as incorporation of additional patches are also discussed     

平面反射阵列天线相移特性分析

本文中采用十字交叉振子为单元分析其移相特性.利用Floquet模展开分析了任意平面波照射下的交叉振子阵列的场分布,计算出其反射系数的相位变化情况.通过数值仿真,分别给出了在不同介质、介质厚度以及入射角度下,详细对比了相位对于振子长度的变化曲线,有助于反射阵列大线的精确设计.     

SAR天线监测的正交编码研究

通过分析天线内监测的原理框架图,结合SAR卫星的自身设备系统提出了SAR天线监测的数学模型,分析耦合和传输对监测带来的影响。根据监测网络编码正交性的要求给出了适用于该监测网络的相位码,提出了受T/R组件移相精度的影响而相位码码长不足的问题,给出了分块和迭代两种解决方法。最后,用计算仿真实验说明了相位码的有效性和监测模型的可行性。     

Design method of Yagi-Uda two-stacked circular loop array antennas

A design method which works as a single balanced feed antenna is presented for the Yagi-Uda two-stacked circular-loop array antenna. The antenna is analyzed with a theoretical model consisting of loop elements and feeder sections. The results are compared with experiments. By using the computed and measured antenna currents, the gain enhancement of the antenna is confirmed to be due to both the stacked-loop-array and endfire-array effects. A method of compensation for the reflection loss and a design procedure are discussed in detail. A graphical method is given to estimate the optimum size of the antenna without detailed numerical calculations, and the performance of the designed antenna is demonstrated by experiments. Experimental results are presented for several antennas arranged with different numbers of loops in the endfire and broadside directions     

Design of Dielectric Grating Antennas for Millimeter-Wave Applications

At theoretical procedure well suited for generating design data on dielectric grating antennas for the millimeter-wave region is presented. The procedure utilizes the effective dielectric constant (EDC) method to determine the phase constant of the leaky modes supported by the antenna structure of finite lateral width. The radiation or leakage constant of these modes is obtained from the relatively simple boundary value problem of dielectric grating antennas of infinite width. For single-beam radiation, the practicably interesting case, the phase and leakage constants completely determine the field distribution in the antenna aperture, from which the directivity gain and radiation pattern are then calculated. The dependence of the antenna characteristics on the dimensions of the radiating structure is presented and discussed for epsilon = 12, the dielectric constant of typical millimeter-wave materials, such as silicon and GaAs.     

Design of a minimum-loss series-fed foldable microstrip

The design and analysis of a series-fed, low-loss, inverted microstrip array antenna, operating at 1.413 GHz is presented. The array antenna is composed of two subarrays consisting of an equal number of microstrip patches connected together through a series microstrip line. The subarrays are coaxially fed 180/spl deg/ out of phase. This approach ensures a symmetric radiation pattern. The design approach for obtaining a low sidelobe ratio and a low loss microstrip array is accomplished using the IE3D code. Experimental and simulated data are presented and discussed.     

Center-fed microstrip patch antenna

A novel feeding scheme for microstrip patch antennas is presented, which consists of a coaxial probe and shorting pin separated by a narrow slot centrally cut at the radiating patch. The impedance and radiation characteristics of a conventional probe-fed microstrip patch antenna and the proposed microstrip patch antenna are experimentally examined and compared. The effects of the slot length on the antenna operation are also discussed.     

雷达导引头天线技术发展趋势探讨

基于现代雷达技术的发展和应用,详细分析了雷达导引头天线技术的发展趋势。由于雷达导引头对天线性能的特殊需求,在回顾反射面天线技术的发展过程的基础上,着重探讨了阵列天线技术,包括波导裂缝阵天线技术、有源相控阵天线技术以及共型天线阵技术在雷达导引头中的应用,从而对其发展趋势进行了探讨和分析,非线性有源天线阵技术的出现将会极大地推动导引头相控阵天线技术的发展。     

Short-pulse characteristics of the conical spiral antenna

The short-pulse charactersitics of the conical spiral antenna are examined in detail. The antenna is anlyzed using a time-domain integral equation. Various peculiarities associated with the numerical solution procedure are discussed, including the effects of a highQ, low-frequency resonance and impedance loading of the antenna. Special attention is directed to the radiated-pulse properties of the antenna for different types of time-varying excitation. Also presented is a quantitative assessment of the antenna's fidelity under pulsed conditions and an approach for obtaining the desired radiated-pulse shape by tailoring the time variation of the applied antenna voltage.     

一种小尺寸极化阵列及其高精度定位波束形成

提出一种偶极子天线单元构成的极化敏感阵列用于全球卫星导航信号的接收,经过阵列信号波束形成后,在抗干扰的同时保留卫星导航信号中载波相位测量值的准确性,可用于基于载波相位测量的高精度差分定位。与传统的圆极化天线阵列相比,该阵列具有阵元构造简单、尺寸小的特点。通过建立极化阵列接收信号模型,分析了天线极化和波束形成算法对卫星导航信号相位的影响,给出了相适应的相位中心稳定的数字波束形成算法。仿真验证了分析的正确性和算法的有效性。     

一种新的宽带Chirp信号到达角估计

提出了基于空问聚焦的宽带信号到达角(DOA)估计算法。该算法利用对称阵子和双线性变换可将多个宽带信号聚焦至各自的瞬时频率,再通过傅立叶变换,在信号各自的瞬时频率上构造相关矩阵,由此构造MUSIC空间谱可获得信号的DOA。分析了阵元通道幅相不一致对算法的影响,并给出了基于相关矩阵Toeplitz性的校正算法。计算机仿真结果表明算法的正确性。     

Low Profile GALILEO Antenna Using EBG Technology

A dedicated low profile antenna for geodesic applications is presented. This type of antenna requires mitigation of multipath signals to achieve sub-centimeter level of precision. Typically, bulky and heavy choke ring structures have been used to reduce the effects of multipath interference. The antenna presented here consists of a low temperature co-fired ceramic (LTCC) patch antenna immersed in an electromagnetic bandgap (EBG) substrate. The EBG substrate reduces the effects of multipath by blocking the propagation of surface waves. The result is an antenna showing good multipath rejection and a stable phase center. The advantage of printed EBG substrates is that they can be realized in a low-weight, low-price, and low-profile fashion. First prototypes have been manufactured and tested, and its performance has been compared to that of a more classical choke ring antenna.     

Circularly polarised dielectric resonator antenna excited byperturbed annular slot with backing cavity

The circularly polarised dielectric resonator antenna excited by a perturbed annular slot is investigated experimentally. A backing cavity is placed beneath the slot to block undesirable backside radiation. The effects of varying the slot on the return loss and axial ratio are discussed. The radiation patterns and antenna gain of the configuration are also presented     

Basic theory of probe-compensated near-field measurements

The general problem concerning the interaction of a probe antenna with the near field of an arbitrary antenna is considered. The application of the Lorentz reciprocity theorem to the problem of determining antenna characteristics, including the far-field pattern, is presented. The data required to correct for the directional effects of the probe, the effect of probe correction on the measured data, and the attendant mathematical computations in rectangular systems are described. Extensions to cylindrical and spherical systems are discussed.     

Wide-band microstrip antenna with an H-shaped coupling aperture

Theoretical and experimental results of a wide-band planar antenna are presented. This antenna can achieve a wide bandwidth, low cross-polarization levels, and low backward radiation levels. For wide bandwidth and easy integration with active circuits, it uses aperture-coupled stacked square patches. The coupling aperture is an H-shaped aperture. Based on the finite-difference time-domain method, a parametric study of the input impedance of the antenna is presented, and effects of each parameter on the antenna impedance are illustrated. One antenna is also designed, fabricated, and measured. The measured return loss exhibits an impedance bandwidth of 21.7%. The cross-polarization levels in both E and H planes are better than 23 dB. The front-to-back ratio of the antenna radiation pattern is better than 22 dB. Both theoretical and experimental results of S parameters and radiation patterns are presented and discussed     

Radiating dipole antenna with tapered impedance loading

The far-field radiated waveform and field pattern from a thin dipole antenna in the transmission line approximation are considered when the antenna is driven by a voltage generator of waveformV_{0}u(t), whereu(t)is the unit step function. The antenna is loaded with a tapered form of loading and is permitted to include reactance as well as resistance. Analytical and numerical solutions for the far-field pattern and waveform are discussed. In particular, the effects of parallel resistive and inductive loading are presented.     

Printed Planar Antenna for Wideband Applications

A compact planar antenna operating at a frequency range of 3–16 GHz is presented for wideband applications. The antenna is composed of a square patch fed by a microstrip line and a partial ground plane with a rectangular slot. The proposed antenna is very easy to be integrated with microwave circuitry for low manufacturing cost. The flat antenna has a compact structure and the total size is 29 mm × 22 mm. The result shows that the measured impedance bandwidth (VSWR≤ 2) of the proposed antenna is 3.2–15.44 GHz, with a notch from 4.7 to 5.8 GHz. The effects of the structure parameters on impedance bandwidth are also investigated. Details of the proposed compact planar antenna design are presented and discussed.     

Antenna with multibeam applications

The design of a dual-reflector antenna that focuses an inclined incident plane wave to a point away from the axis of symmetry of the reflector is discussed. A useful application of such a system would be as a multibeam antenna for use in communication via satellites. Curves of path-length errors are presented for the feed positioned on the axis of symmetry, and the effects of refocusing are shown.     

Analysis of phase-focused near-field testing for multiphase-centeradaptive radar systems

Airborne or spaceborne radar systems often require tests before deployment to verify how well the system detects targets and suppresses clutter and jammer signals. The radar antenna diameter can be large and thus the conventional far-field test distance is impractical to implement. The theory and simulations of phase-focused near-field testing for adaptive phased array antennas is discussed. With near-field source deployment, standard phased-array near-field phase focusing provides far-field adaptive nulling equivalent performance at a range distance of one aperture diameter from the adaptive antenna under test. Both main beam clutter sources and sidelobe jammer sources are addressed. The phased array antenna elements analyzed are one-half wavelength dipoles over the ground plane. Bandwidth, polarization, array mutual coupling, and finite array edge effects are taken into account. Numerical simulations of an adaptive antenna that has multiple displaced phase centers indicate that near-field and far-field testing can be equivalent