Partial adaptive nulling on a monopulse phased array antenna system

A partial phase-only nulling (PPON) algorithm has been developed and evaluated on a 496-element monopulse phased array antenna system which employs five-bit phase shifters. Using this PPON algorithm allows nulls in the far-field pattern to be steered to the desired directions for a phased array equipped with low-resolution phase shifters to perform simultaneous nulling in the sum and two difference patterns in the environment of multiple jammers. Simulated and experimental patterns are illustrated     

Determination of far-field antenna patterns from near-field measurements

In many cases, it is impractical or impossible to make antenna pattern measurements on a conventional far-field range; the distance to the radiating far field may be too long, it may be impractical to move the antenna from its operating environment to an antenna range, or the desired amount of pattern data may require too much time on a far-field range. For these and other reasons, it is often desirable or necessary to determine far-field antenna patterns from measurements made in the radiating near-field region; three basic techniques for accomplishing this have proven to be successful. In the first technique, the aperture phase and amplitude distributions are sampled by a scanning field probe, and then the measured distributions are transformed to the far field. In the second technique, a plane wave that is approximately uniform in amplitude is created by a feed and large reflector in the immediate vicinity of the test antenna. And in the third technique, the test antenna is focused within the radiating near-field region, patterns are measured at the reduced range, and then the antenna is refocused to infinity. Each of these techniques is discussed, and the various advantages and limitations of each technique are presented.     

Tracking error of phased array antenna

The tracking error of a phased array antenna between transmitting and receiving frequencies was measured by in-flight experiments using a geostationary satellite. The tracking error was found to depend on beam-scanning angle and the ratio of transmitting and receiving frequencies. Measured results agreed well with a theoretical prediction. An effective method to eliminate the tracking error is proposed     

相控阵天线实验系统设计

介绍了一种新颖的相控阵天线实验系统。首先给出了系统的组成和设计原理,然后介绍了系统的软件实现过程以及多用户教学功能的实现。所设计的实验系统实现了相控阵天线设计教学过程,具有操作简单、实验真实直观等特点,取得良好效果。     

Prediction of far-field from uniform and non-uniform under-sampled near-field data in planar near-field antenna measurements

In near-field antenna measurements various forms of uniform and non-uniform sampling techniques have been widely deployed. Considering the fact that the near-field pattern of any antenna is a spatially quasi-band-width-limited function of space coordinates, Shannon's theorem simply defines the sampling frequency. Based on the sampling theorem, in order to precisely reconstruct a band-limited signal from its samples, the sampling frequency must be at least twice as much as the signal's bandwidth. Through the simulations and theoretical evaluations this research shows that if the near-field pattern is either uniformly or non-uniformly under-sampled due to any practical reasons, yet a good estimation of far-field pattern can be obtained especially if the antenna under test (AUT) is a directive high-gain or super high-gain antenna. Also the time efficiency of far-field prediction from under-sampled near-field data is discussed and the advantages and disadvantages are highlighted.     

二元相控阵手机天线分析

现代移动通信的迅猛发展迫切要求进一步研究移动终端智能天线技术。对手机用二元相控阵天线进行了研究,使用矩量法对该天线进行了电磁仿真。通过改变天线阵二单元激励源的相位,实现了方向图主波束扫描的功能,表明了该天线方案作为手机智能天线具有良好的应用前景。     

A flat four-beam compact phased array antenna

This paper presents a flat four-beam compact phased array antenna. The low-cost and compact phased array antenna is designed using a circular array of four circular microstrip antennas made of low-cost material and four 1-bit phase shifters. The main beam of the antenna can be switched in four directions with the gain of about 4 dBi in each main-beam direction. More than 90° half-power beamwidth and over 10 dB F/B ratio are obtained. In addition, the diversity performance is considered and the diversity performance of this antenna can be provided with the envelope correlation about 0.6     

Microstrip adaptive array antenna

A planar adaptive array of three microstrip patch antennas consisting of a central active microstrip antenna and two symmetrical lateral passive antennas is used to steer the beam. An electronic beam scanning of ±20° can be achieved with the control of reactive loads located into the lateral patches     

Tamed adaptive antenna array

The adaptive array under directionaily constrained minimization of power (DCMP) algorithm is improved by adding a "pseudonoise." It is effective to protect the desired signal from cancellation or distortion in such cases as 1) where a coherent interference is incident, or 2) where the desired signal direction for the constraint contains some pointing error, or 3) when the desired signal is broad band, The optimum amount of pseudonoise to be added is also discussed and its formula is given. This system is named "tamed adaptive antenna" since its killing capability is somewhat moderated so as not to hurt the desired signal.     

Planar near-field to far-field transformation using an array ofdipole probes

A method is presented for computing far-field antenna patterns from measured near-field data measured by an array of planar dipole probes. The method utilizes the near-field data to determine some equivalent magnetic current sources over a fictitious planar surface which encompasses the antenna. These currents are then used to find the far fields. The near-field measurement is carried out by terminating each dipole with 50 Ω load impedances and measuring the complex voltages across the loads. An electric field integral equation (EFIE) is developed to relate the measured complex voltages to the equivalent magnetic currents. The mutual coupling between the array of probes and the test antenna modeled by magnetic dipoles is taken into account. The method of moments with Galerkin's type solution procedure is used to transform the integral equation into a matrix one. The matrix equation is solved with the conjugate gradient-fast Fourier transformation (CG-FFT) method exploiting the block Toeplitz structure of the matrix. Numerical results are presented for several antenna configurations to show the validity of the method     

Two-dimensional scanning leaky-wave antenna by utilizing the phased array

An aperture-fed patch antenna array is connected to the open end of a short leaky-wave antenna (LWA) to demonstrate the two-dimensional beam-scanning capability in this paper. This design not only offers another radiation path of the reflected wave, but also creates another scanning radiation pattern on the back plane of the substrate. The reflected wave of the LWA is equally separated by a power divider, modulated by each varactor-tuned phase shifter, and injected into two radiating aperture-coupled antennas. The operated frequencies are tuned to control the LWA main position in the elevation plane; meanwhile, by tuning the phase difference between two phase shifters, the main beam of the aperture-coupled antenna array can be scanned in the backside E plane. Experimental result shows that the suppression of the reflected wave can be 7 dB at 10.0 GHz with a short LWA length of 6 cm (two wavelengths). The H-plane and backside E-plane scanning radiation patterns have great potential in many applications and provide more flexibility to traditional designs.     

Optical feed for a phased array microwave antenna

Microwave signals for all array elements in a phared array microwave antenna are simultaneously generated by spatial sampling of a moving sinusoidal interference pattern formed between two frequency-offset injection-locked laser diodes. The offset and radar frequency of 3.2 GHz were generated by a Bragg cell. A nearly distortionless antenna beam pattern and 180° steering are demonstrated in a linear seven-element array.     

Microstrip antenna phased array with electromagnetic bandgap substrate

Uniplanar compact electromagnetic bandgap (UC-EBG) substrate has been proven to be an effective measure to reduce surface wave excitation in printed antenna geometries. This paper investigates the performance of a microstrip antenna phased array embedded in an UC-EBG substrate. The results show a reduction in mutual coupling between elements and provide a possible solution to the "blind spots" problem in phased array applications with printed elements. A novel and efficient UC-EBG array configuration is proposed. A probe fed patch antenna phased array of 7/spl times/5 elements on a high dielectric constant substrate was designed, built and tested. Simulation and measurement results show improvement in the active return loss and active pattern of the array center element. The tradeoffs used to obtain optimum performance are discussed.     

宽带星载DBF相控阵天线设计与实现

针对低轨卫星通信天线波束"等通量"覆盖的赋形要求,采用遗传算法对天线阵列进行了多目标平衡优化综合.根据SHA阵和波束覆盖的空间旋转对称性,在波束空间和阵元空间内进行阵元分组,将波束形成矩阵自由度降为1/3,简化了遗传算法参数数量,为波束形成因子复用奠定基础.针对16波束宽带输入,利用DFT滤波器组、复用式波束形成网络、单音闭环校正等算法设计了分布式数字波束形成器和幅相校正单元,运算量降为原来的4.5%,节省硬件资源80%.最后首次完成了16波束61阵元星载DBF相控阵天线样机的研制,暗场测试结果表明波束增益达到等通量覆盖要求,验证了以上算法和工程设计的正确性与有效性.     

相控阵天线时域有限差分计算中激励源分析

在时域有限差分(FDTD)方法用于偶极阵列天线数值计算时,采用带有内电阻的缝隙馈电激励源模型,及选择自由度较大的调制高斯脉冲信号,来提高数值算法迭代计算的收敛速度;在各馈电单元的时域信号中通过引入合适时间延迟,实现对相应单元相位的控制。用二元相控阵列天线模型,验证了算法和程序是正确的;用六元相控圆形阵列天线,分析了该算法在实际相控阵天线问题分析中的应用。     

An optically driven phased array antenna utilizing heterodynetechniques

An optically driven phased array antenna system that utilizes heterodyne techniques to generate the microwave carrier frequency and phases is proposed. The heterodyning at each antenna element requires three injection-locked lasers. The microwave carrier frequency is determined by the order of the modulated sideband used in the injection-locking scheme. A design is also presented for an integrated optical fast Fourier transform (FFT). This device can perform the necessary phase processing for both beam steering and detection-of-arrival angle. Recent results on the noise properties of injection-locked semiconductor lasers are applied to the proposed antenna system. The effect of noise on the gain, signal-to-noise ratio, and the bandwidth of the antenna system is examined. It is shown that the performance degradation of the system, due to the noise in the lasers, is minimal, and therefore the bandwidth promise of optical drive could well be achieved with the use of heterodyne laser locking techniques     

一种宽带低剖面相控阵单元天线

为满足宽带定向低剖面相控阵设计要求,提出了一种立体和平面结构、寄生单元和激励单元相结合、网络和阵列环境相结合的锥形复合定向新颖高增益偶极天线,其单元指标为增益约6~8 dBi、阵面高度为0.135λmax,由该单元组成的阵列的计算结果表明：该天线可以满足3个倍频程、30°扫描要求,为实现低剖面定向超宽带天线提供一种技术路线,为超宽带系统应用提供了有力支持.     

Generation of dual beams from spherical phased array antenna

An active X-band spherical phased array developed for transmitting high bit rate data from remote sensing satellites to two ground stations simultaneously is presented. Resolution of the dual phase adjustment of the phase shifters, which are common to generate two beams, is discussed.     

Ka频段双圆极化相控阵天线设计

设计了一个8×8的Ka频段双圆极化相控阵天线。该天线单元采用正交缝隙耦合馈电的多层贴片微带天线,并由一个小型化宽带3 d B枝节电桥实现双圆极化。为提高天线圆极化性能,依次旋转天线单元,形成2×2双圆极化天线子阵。以天线子阵为基础,扩展成8×8相控阵天线。HFSS仿真结果表明,天线在方位360°俯仰±60°范围内进行双圆极化扫描,轴比小于3 d B,且轴比带宽达30%。该研究结果可应用于卫星通信的双圆极化相控阵天线的设计。