有源相控阵天线远场测试系统设计

为解决某型有源相控阵天线辐射特性测试占机时间长、系统不稳定、交付能力不满足生产需求等问题,开展了有源相控阵天线辐射特性校准与测试技术研究。针对被测产品体积小、频段高、天线单元多以及交付数量大的特点,选择了较为合适的远场测试系统的设计方案。测试系统硬件构成复杂,包含微波暗室、接收转台、发射扫描架、测控单元、水冷系统等;测试软件涉及项目多,包含幅度相位校准、方向图测试、指向精度补偿测试、等效全向辐射功率（EIRP）测试、有源增益测试等。重点对微波暗室尺寸设计、高精密转台精度分析、幅度相位校准算法和波束指向误差补偿技术进行了详细论述,完成了该型有源相控阵天线远场测试系统的软、硬件设计。测试系统精度高、动态范围大、运行稳定。该设计方案具有较好的推广价值。     

Phase‐only synthesis of planar arrays using autocorrelation matching method

Autocorrelation matching method is proposed for phase‐only synthesis of power pattern of planar antenna arrays. This method is based on equating the autocorrelation coefficients of a planar array having a specified amplitude of excitations to those of a conventionally designed planar array. The effectiveness of the proposed method is verified by synthesis of pencil‐beam and flat‐top patterns.     

星载SAR卫星天线扰动对波束中心指向的影响

天线波束中心指向稳定度是星载合成孔径雷达（SAR）天线的一个重要指标,影响天线波束中心指向稳定度的因素很多。该文以星载合成孔径雷达等间距均匀分布平面相控阵天线为分析对象,通过建立天线振动模型,分成多个阵元位移、天线阵面偏移、天线阵面振动等三种典型情况,对卫星天线在外力扰动情况下的天线方向图和回波相位变化情况进行分析,推导卫星天线稳定性对天线波束中心指向稳定度的影响,并进行了仿真,简要讨论了天线波束中心指向变化对SAR成像的影响。     

Two dimensional coupled oscillators array with rhombus structure and its application in active antenna array

Beam scanning and forming can be achieved by coupled oscillators array without phase shifter. Active antenna array based on coupled oscillators array has the virtue of low cost, high integration, and high efficiency. Traditional two dimensional coupled oscillators array has been arranged on rectangular lattices, and phase difference of adjacent elements is limited to [-90°, 90°]. Therefore, the beam scanning range is limited to [-30°, 30°] from normal for half wavelength element spacing. A new two dimensional coupled oscillators array with rhombus structure is presented. Phase control method and phase error of the array are also provided. Stability of the array is analyzed, and stable condition is given. When this coupled oscillators array with rhombus structure is used in active antenna array, theoretical results show that phase difference of adjacent elements reach the limit of [-180°, 180°] along the horizontal and vertical directions. Therefore, it has wider beam scanning range than that of a rectangular lattice structure.     

3-D Unitary ESPRIT: Accurate attitude estimation for unmanned aerial vehicles with a hexagon-shaped ESPAR array

Accurate estimation of the attitude of unmanned aerial vehicles (UAVs) is crucial for their control and displacement. Errors in the attitude estimate may misuse the limited battery energy of UAVs or even cause an accident. For attitude estimation, proprioceptive sensors such as inertial measurement units (IMUs) are widely applied, but they are susceptible to inertial guidance error. With antenna arrays currently being installed in UAVs for communication with ground base stations, we can take advantage of the array structure in order to improve the estimates of IMUs via data fusion. In this paper, we therefore propose an attitude estimation system based on a hexagon-shaped 7-element electronically steerable parasitic antenna radiator (ESPAR) array. The ESPAR array is well-suited for installment in the UAVs with broad wings and short bodies. Our proposed solution returns an estimation for the pitch and roll based on the inter-element phase delay estimates of the line-of-sight path of the impinging signal over the antenna array. By exploiting the parallel and centrosymmetric structure in the hexagon-shaped ESPAR array, the 3-dimensional Unitary ESPRIT algorithm is applied for phase delay estimation to achieve high accuracy as well as computational efficiency. We devise an attitude estimation algorithm by exploiting the geometrical relationship between the UAV attitude and the estimated phase delays. An analytical closed-form expression of the attitude estimates is obtained by solving the established simultaneous nonlinear equations. Simulations results show the feasibility of our proposed solution for different signal-to-noise ratio levels as well as multipath scenarios.     

Planar antenna beam deflection using low‐loss metamaterial for future 5G applications

A method to tilt the beam of a planar antenna in the E‐plane is demonstrated by implementing a metamaterial (MM) structure onto the antenna substrate at the fifth‐generation (5G) band of 3.5 GHz. The beam tilting is achieved due to the phase change that occurs when the electromagnetic (EM) wave traverses through two media with different refractive indices. A new adjacent square‐shaped resonator (ASSR) structure is proposed to achieve the beam tilting in a dipole antenna. This structure provides a very low loss of ?0.2 dB at 3.17 GHz. The simulation and measurement results illustrate that the radiation beam of the dipole antenna is tilted by +25° and ?24° depending on the position of the ASSR array onto the dipole antenna substrate. In addition, no degradation in the gain is observed as in the conventional beam‐tilting methods; in fact, gain enhancement values of 3 dB (positive deflection) and 2.7 dB (negative deflection) are obtained compared with that of a dipole antenna with no ASSR array. The reflection coefficient of the dipole antenna with ASSR array has a good agreement with that of the dipole antenna with no ASSR array. The measured results agree well with the simulated ones.     

High gain substrate integrated waveguide beam scanning antenna with sub‐array elements

A method to enhance the gain of substrate integrated waveguide (SIW) beam scanning antenna is proposed in this article. 2 × 2 SIW cavity‐backed sub‐arrays are employed in array design. The antenna is constructed on two layers. The top layer places four SIW cavity‐backed sub‐arrays as radiating elements and the bottom layer is an SIW transmission line to feed the sub‐arrays. Beam scanning feature can be obtained due to the frequency dispersion. Moreover, through separating radiators to the other layer and using 2 × 2 SIW cavity‐backed sub‐arrays as radiating parts, the antenna gain is improved significantly. For a linear array, 4.1 to 6.8 dB gain enhancement is achieved compared to a conventional SIW beam scanning antenna with the same length. Then, the linear array is expanded to form a planar array for further gain improvement. A 64‐element planar beam scanning array is designed, fabricated, and tested. Experimental results show that the proposed planar array has a bandwidth from 18.5 GHz to 21. 5 GHz with beam scanning angle from ?5° to 11.5° and gain in the range of 20.5 to 21.8 dBi. The proposed high gain beam scanning antennas have potential applications in radar detection and imaging.     

Beam pointing errors of phased arrays for digital switched beam acoustic radars

Phased array antennas and corresponding driving electronics units have been introduced in Atmospheric Acoustic probing. Using modern microprocessor systems in conjunction with suitable digital electronics, it is possible to implement an acoustic probing system, with full beam switching capabilities.

The radiation pattern of a planar M × N phased array acoustic radar equipped with digital phase shifting circuits for the beam switching, is examined and all the necessary formulas are presented. For a given accuracy of phase quantization, the set of beam pointing directions which can be achieved without deterioration, due to this quantization, is computed and diagrams showing the mapping of the available beam pointing directions throughout space are presented. The relation between the cardinal number of this set of directions and the accuracy of the phase quantization is also presented.

The beam pointing errors, due to the accuracy of the phase quantization and the dissimilarities among the array's elements are analysed using simulation techniques     

AgileDARN雷达内定标的方法与实现

AgileDARN雷达系统是一种基于全数字相控阵技术的灵敏型地基相干高频雷达系统,实现对中高纬度电离层的探测。雷达系统的幅度和相位不一致将会导致雷达发射波束和接收波束的波束指向偏移,副瓣电平抬高和天线增益下降,最终影响雷达的探测精度。针对AgileDARN雷达系统幅度和相位不一致性展开研究,提出了一种基于FPGA和C++软硬件相结合的内定标方法。在发射探测信号之前,分别发送接收定标信号和发射定标信号,通过雷达系统的各个接收和发射通道后,计算各个通道之间的幅度和相位差异,用补偿因子来实现对雷达多通道幅度和相位不一致性的校正。实测数据表明:校正后各通道间幅度误差小于0.2 dB,相位误差小于1°。在满足系统一致性要求的前提下,既保证了实时性,又节省了雷达系统成本。     

AgileDARN雷达内定标的方法与实现

AgileDARN雷达系统是一种基于全数字相控阵技术的灵敏型地基相干高频雷达系统，实现对中高纬度电离层的探测。雷达系统的幅度和相位不一致将会导致雷达发射波束和接收波束的波束指向偏移，副瓣电平抬高和天线增益下降，最终影响雷达的探测精度。针对AgileDARN雷达系统幅度和相位不一致性展开研究，提出了一种基于FPGA和C++软硬件相结合的内定标方法。在发射探测信号之前，分别发送接收定标信号和发射定标信号，通过雷达系统的各个接收和发射通道后，计算各个通道之间的幅度和相位差异，用补偿因子来实现对雷达多通道幅度和相位不一致性的校正。实测数据表明:校正后各通道间幅度误差小于0.2 dB，相位误差小于1°。在满足系统一致性要求的前提下，既保证了实时性，又节省了雷达系统成本。     

基于遗传算法的多板天线时延相位补偿技术

关于动中通系统中普遍采用抛物面天线,可使得系统小型化难度增加,为优化最佳天线方案,采用平板天线取代抛物面天线可以部分改善.为促进动中通技术在车载平台中的应用,提出了超低轮廓相控阵天线方案,使得平板相控阵天线的高度进一步降低.针对孔径效应和孔径渡越时间限制问题,给出了时延相位两级补偿的方法,有效扩展了天线系统的工作带宽;同时采用遗传算法调整天线阵因子相位,对多板相控阵天线方向图的副瓣高度实现了优化.仿真结果表明,多板天线方案可以实现性能对平板天线的逼近,并很好的适应了车载平台对天线高度的严格要求,有较高的工程实用价值.     

Design of multi‐beam antenna based on Rotman lens

A planar Rotman lens antenna that generates multiple beams is presented over a wide angular range. The proposed multi‐beam antenna consists of a Rotman lens and a ten‐element printed Yagi antenna array. By properly comparing optical aberrations, expressing as the normalized path length errors Δl, the suitable ratio of on‐axis to off‐axis focal length (g = G/F) is acquired so as to minimize phase errors for the array elements. Ten dummy ports are employed to reduce the performance deterioration caused by energy reflection. A prototype with seven input ports was fabricated and measured, covering a wide scanning angle of 60° (–30°, 30°). The measured beam patterns show that the seven beam gains are distributed from 11.9 to 13.6 dBi under operating of 8.15 GHz. Both the simulated and measured results are used to verify the design approach.     

相位激励赋形多波束形成算法分析及仿真实现

数字波束形成是天线技术与数字信号处理技术结合的产物,是智能天线实现空分多址的关键技术.采用相位激励赋形多波束形成技术,给出了智能天线数字多波束形成的优化算法,利用该算法对均匀圆环阵天线各单元权值进行计算,仿真实现了均匀圆环阵天线多波束方向图,在不同方向上同时得到了多个波束.该算法计算复杂度低,空间隔离度好.阵元呈圆环状分布,具有全向搜索特性,克服了直线阵搜索的缺点.该方法还可用于任意单元构成的不均匀阵列天线,以及波束展宽和扇形波束的形成.     

The low-cost polarization reconfigurable phased array based on high-precision full 360° phase shifter

In this article, to adapt the various polarization of user terminal, a 1 × 4 C-band high-integrated polarization reconfiguration phased array based on phase shifter matrix is presented. The phased array combined with polarization reconfiguration antenna elements exhibits the desired beamforming patterns and achieves beam polarization reconfiguration simultaneously. Based on the technique of the shunted microstrip open-stub and equalizing resistor, a high-precision reflection-type phase shifter with full 360° continuous phase tuning range is designed for this phased array in this article. The prototype of the polarization reconfiguration phased array is designed and fabricated. Measured results show that proposed phased array works at 5.8 GHz and achieves 21.4% (1.2 GHz) impedance bandwidth and 14.3% (800 MHz) 3 dB axial ratio bandwidth. The beam coverage range at 5.8 GHz is more than 64° with 0.2° beam steering resolution.     

多波束天线通道幅相误差的自校正算法

多波束天线利用多信号分类(MUSIC)算法对目标参数进行精确估计时,存在多波束天线的通道幅度和相位误差的失配现象,使MUSIC算法的性能严重下降;针对基于MUSIC的数字波束通道不一致问题,给出了一种新的基于MUSIC算法的最小化代价函数的波束无源自校正算法,利用阵列结构的先验知识对接收数据进行预处理,得到校正矩阵后自校正,并根据多波束阵列天线形成网络天线实测参数,加入随机幅度和相位误差进行计算机模拟仿真,验证仿真算法的正确性。     

基于双焦点设计的平面波束扫描透镜天线研究

为了提升平面透镜天线的扫描性能,以实现波束扫描或多波束应用,首先研究设计了单焦点平面透镜天线,针对单焦点平面透镜天线在大角度扫描时增益降低太快的问题,引入了反射阵和传统介质透镜的双焦点设计方法。基于阵列天线合成理论,计算了双焦点透镜天线的辐射特性。采用多层金属孔阵列单元,建模了平面透镜天线模型,仿真对比了单焦点透镜和双焦点透镜天线的扫描辐射特性。结果表明,在扫描范围（0°-27°）内,双焦点透镜天线的最低增益相对于单焦点透镜天线有明显提升,而且大角度扫描方向图形状也有改善,证明了双焦点的设计方法有效提升了平面透镜的扫描性能。     

毫米波MIMO系统离散化混合预编码设计

为了提高毫米波大规模多输入多输出（MIMO）系统波束成形增益,降低天线与移相器的硬件成本,提出一种基于离散移相器的混合预编码设计方案。以最优化频谱效率为目标,该方案通过分析均匀直线阵列与均匀平面阵列的响应矢量,将毫米波信道的空间特性预编码的设计考虑为空间稀疏重构问题,采用离散化正交匹配追踪原理求出数字预编码与离散化的模拟预编码。仿真结果表明,同等条件下平面阵列的频谱效率优于直线阵列,同时所提出的离散化混合预编码方案中低精度移相器的性能近乎达到全精度移相器的性能增益。     

Two‐dimensional beam‐scanning using tapered slot antennas and piezoelectric transducers

A wideband phased array is demonstrated using antipodal exponentially‐tapered slot‐antenna (ATSA) arrays operated by piezoelectric transducer (PET)‐controlled phase shifters. A 4 × 4 ATSA array is designed to scan two‐dimensionally across the entire X‐band. The phase shifters for 2D scanning consist of two sets of multiline phase shifters controlled by the PET for scanning in both planes. The 2D phased array has an antenna gain greater than 8 dBi, including all losses due to the phase shifters and transitions, and shows a wide beam‐scanning capability greater than 30° in both the E‐plane and the H‐plane. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

多基线近场目标几何对消比相测角算法

针对目标距离多基线天线阵较近条件下,平行波相位模型失效的问题,提出了一种基于几何对消的多基线比相测角解模糊算法.首先根据多基线天线阵的布局特点与近场目标的回波特性,建立了近场目标回波的相位模型,结合近场目标回波的特点和平行波逐次递推解模糊测角算法,推导了几何对消测角算法,并给出了算法的实现步骤.该算法具有原理简单、性能稳健的特点,解决了平行波测角算法目标近场模型失配的问题,并且同样适用目标处于远场条件下.大量的计算机仿真试验结果表明,基于近场模型的几何对消测角算法在目标远近、静态及动态条件下均具有良好的测角性能和稳健性.     

A compact substrate‐integrated‐waveguide monopulse slot antenna array with TE20 mode

A compact substrate‐integrated‐waveguide (SIW) monopulse slot antenna array with T_E20 mode is proposed, manufactured, and tested in this communication. The TE₂₀ mode electric field distribution is used in this antenna design. The phase difference required by the monopulse system is constructed by changing the orientation of the end of the top microstrip feed line. The microstrip line implements not only the feed function, but also the function of a monopulse comparator. The design greatly reduces the size of the monopulse comparator and the feed network, and improves the aperture efficiency of the antenna. Our measurement shows that the operating frequency of the antenna is 10.4 GHz, and the maximum gain of the sum beam is 13.7 dBi, and the difference beam null depth is ?26 dB. The antenna has the advantages of simple structure, small size, and easy integration of planar circuits. This proposed idea can open new ways for monopulse antenna design.