Measurement and modeling of a microwave active-patch phased arrayfor wide-angle scanning

An active antenna consisting of an integrated oscillator with a passive radiator has been arrayed and beam-scanned using a new principle for phase shifting. The radiating elements consist of a transistor oscillator whose frequency is controlled by a rectangular microstrip patch antenna. Each oscillator is injection locked to an external source. The phase control of the radiated wave is achieved by varying the bias on the transistor. Individual element performance has been characterized for potential use as an array element and is comprehensively reported. Methods used to achieve configurations with full 360° phase control have been investigated utilizing novel configurations and cascaded oscillator pairs. Close to 360° of radiated phase control from each element has been achieved. Measured results on an experimental four-element S-band array indicate that beam scanning in excess of ±60° can be achieved. Mutual coupling effects on this new form of array are studied both experimentally and theoretically. A van der Pol (1934) model for the weak coupling that is occurring on the array is developed and used to qualitatively predict the phase offsetting on array elements. Reasonable agreement between theory and experiment is obtained and it is observed that good control of the coupling mechanism is essential to array performance within this new form of active integrated phase shifterless array     

A 16 element quasi-optical FET oscillator power combining arraywith external injection locking

The authors present analysis, design and experimental results of a 16 element planar oscillator array for quasi-optical power combining. Each element in the array consists of a single FET oscillator with an input port for injection of the locking signal and an output port which is connected to a patch radiator. The array is synchronized using a 16-way power dividing network which distributes the locking signal to the oscillating elements. The array is constructed using a two-sided microstrip configuration, with the oscillators and feed network on one side of a ground plane, and the patch radiators on the opposite side. An effective radiated power (ERP) of 28.2 W CW with an isotropic conversion gain of 9.9 dB was measured at 6 GHz. For an injected power of 10.3 dBm, a locking range of 453 MHz at a center frequency of 6.015 GHz was obtained; a bandwidth of 7.5%. Because of the simple nature of the individual oscillator elements, this approach is well suited to MMIC implementation     

Effect of Coupling Phase on Mutual Injection Locking Range in Coupled Oscillator Arrays

The performance of a coupled oscillator array depends critically on the coupling network. Determination of the optimal coupling phase depends on the oscillator equivalent circuit and the location of mutual coupling between the oscillators. In this paper, the authors examine the effects of coupling phase on the mutual injection locking range. Three element coupled oscillator arrays (COAs) were mutually coupled at two different locations, with each coupling location presenting a different resonance to the coupling network, and the optimal coupling phase required to generate a linear phase shift in the range of $-90^{circ}$ to 90$^{circ}$ was determined. For each coupling location, when the coupling phase was off by 180$^{circ}$ , the arrays were shown to lock with a limited range and operate in a mode other than the in-phase mode.      

Radiating and scattering analyses of a slot-coupled patch antennaloaded with a MESFET oscillator

In this paper, radiating and scattering analyses of a slot-coupled patch antenna loaded with a MESFET oscillator at free-running and injection-locked states are presented. This arrangement is a basic module of an injection-locked active array. With a small injection signal applied directly to the oscillator in a transmission-type mode or indirectly through a patch antenna to the oscillator in a reflection-type mode, the oscillator loaded antenna then becomes an injection-locked active antenna (ILAA) within the locking range. Simulation results yield the oscillating frequency and radiating power at the free-running state and the locking range and radiating power at the injection-locked state. Both radiating and scattering analyses are performed in a unified approach for the transmission-type and reflection-type operation modes of ILAA. Experiments show the validity of the developed theoretical analyses. These results can be applied in the ILAA array design     

约瑟夫森阵列振荡器的相位锁定分析

系统地研究了超导亚毫米波阵列振荡器的相位锁定问题。为使超导振荡器达到高工作频率、窄线宽和高稳定的性能，约瑟夫森结与结之间的相位必须相互锁定。相位锁定可以通过结与结之间的耦合电路得以实现。通过对振荡器的各种耦合电路的比较表明，蝴蝶领结天线结构是一个比较适合约瑟夫森振荡器相位锁定的耦合电路。本文提出了一种超导亚毫米波阵列振荡器模型并对其进行了模拟计算与分析，仿真得出了振荡器各项参数值，并给出了相位锁定的条件。     

A study of steering capability of a microstrip phased array using inter-injection locked oscillators

An innovative, phase coherent, power combining method, known as inter-injection locking applied to linear limited scan phased arrays is investigated. In this novel method, each antenna element in the array is supplied by power from a separate oscillator. However, the oscillator phases are allowed to be synthesized coherently by means of a coupling network and injection currents, being the input controls to the system of coupled phases oscillators. The inter-injection-locked phased arrays studied in this paper provide more design freedom than conventional phased arrays. They also result in systems more adapted to solid state monolithic integration technology.     

A compact single layer injection-locked linear scanning array

A compact, single layer, CPW-fed, patch scanning array architecture using injection locking at 9.83 GHz is presented. The patch antennas are printed on the front side of the substrate while the electronics are situated at the back side leading to a simple and compact design. The unit element for the array is a self oscillating active patch antenna with a GaAs FET centered behind the patch for tight packing. The feedback for the oscillator is provided through electromagnetic coupling using a twin-slot arrangement behind the patch. A low power control signal is injected through parasitic coupling at the CPW side of the circuit. Phase shifting of the elements is achieved by electronically adjusting the gate voltage of the GaAs FETs. A scan range of -12°- +9.5° is obtained for a four element prototype array     

Frequency stabilization of power-combining grid oscillator arrays

In this paper, we report the results of phase locking of grid oscillator arrays. First, a voltage-controlled grid oscillator array with a center frequency of 4.7 GHz and with a 300-MHz electric tuning range was locked to a frequency synthesizer through a phase-locked loop. Second, a 4 × 4 and a 6 × 6 grid oscillator arrays were locked by way of the injection locking. In both methods, a simple loop antenna mounted on the reflection mirror was used for taking/injecting signals from/to the array. Results show that the phase noise performance is improved significantly in the locked oscillator arrays     

Combination dielectric resonator, power combiner, and antenna

A rectangular dielectric resonator housed in a cutoff parallel-plate waveguide is used both as a radiating element and microwave power combiner. The resonator is excited by using tuned electrically short monopole antennas to induce a longitudinal electric operating mode. The resonator is then used in conjunction with free-running oscillators in order to provide, via mutual injection locking, stable in-phase power combining. Furthermore, the resonator is arranged such that one of its faces radiates a portion of the power-combined signal. Since the resonator is housed in a cutoff waveguide, the cross-polarization radiation from the antenna is suppressed. It was found that, for a single element, a gain in the azimuthal plane of 5 dB could be achieved and, for a two-element array, a gain of 7 dB was obtained with better than -25-dB cross polarization for each case. The oscillator power-combining efficiency for a single-element antenna (two oscillators) was 91%, and the spatial power-combining efficiency for a two-element antenna array, (four oscillators) was found to be 90%. In addition, it is shown that the presence of the dielectric inserts in conjunction with coupled oscillator dynamics provides moderate overall oscillator phase noise improvement     

互耦效应下端射阵机载雷达STAP方法研究

互耦效应是阵列天线一个固有的重要属性,而端射阵天线由于其特殊的主波束指向以及抑制栅瓣所要求的小阵元间距,其阵列间存在的互耦效应比侧射阵更加严重.本文首先分析了互耦效应对端射阵天线方向图的影响,构建了存在互耦效应下的天线方向图模型;然后给出了考虑互耦效应的杂波模型并分析了互耦对端射阵机载雷达杂波谱以及STAP（Space-Time Adaptive Processing）性能的影响;最后提出了一种基于杂波协方差矩阵重构的互耦效应补偿方法.计算机仿真验证了所提方法的有效性.     

Planar Radiating Oscillator Using Butterfly-Shaped Patch Element and Spatial Power-Combining Array

A planar radiating oscillator using a butterfly-shaped patch element is described. To obtain an injection-locking range that can be changed and low cross-polarization, we used a butterfly-shaped patch. The patch element was able to change the injection-locking range while maintaining low cross-polarization, and two types of patch were compared. As one application, we designed and fabricated 1x2, 2x1 and 2x2 spatial power-combining arrays by using radiative mutual coupling. The 2x2 array was successfully operated with a single-bias supply without using a 3-D (three-dimensional) Fabry-Perot cavity. An equivalent isotropic radiated power of 2.5 W was measured at X-band.     

基于小型阵列试验的相控阵单元互耦特性研究

相控阵天线辐射单元的互耦特性对天线整体性能有着重要影响,而互耦与具体单元形式相关,因此模型复杂, 难以精确计算和预测。在阵元的小型阵列试验过程中,采用互耦测试的方法,对准八木振子、微带贴片、Vivaldi 单元 等几种典型宽带相控阵单元的互耦特性进行了实验研究,结果表明互耦对不同类型的单元影响大不相同,对单元特性 不仅有传统认为的负面作用,还可能有改善性能的作用,分析结果可供相控阵天线设计时参考;同时,利用测试数据 分析了小型试验阵列的规模对结果的影响,提出了小型阵列的规模依据。     

Beam scanning characteristics of 64 element broadband volumetricarray

The broadband beam scanning characteristics of a 64 element volumetric array antenna are examined. Main beam patterns are synthesised from the measured embedded element patterns and therefore include the effects of mutual coupling. The performance of the array is examined over a wide angular range at frequencies between 8 and 12 GHz     

考虑互耦影响下的智能天线数字波束赋形

本文分析了阵列单元之间的互耦对智能天线阵列数字波束赋形（DBF）的影响。通过对天线子系统建立等效接收模型，对由理想半波振子组成的8单元圆阵（用于TD-SCDMA系统）进行矩量法（MOM）分析，得到表征单元之间互耦的广义阻抗矩阵，由此得到智能天线的互耦信息及其对天线性能（SINR）的影响。通过数值分析结果与试验的结果与对比可以看出互耦对副瓣电平和智能天线抑制干扰的能力有一定的影响。本文的分析对智能天线的研究具有一定意义。     

Waveguide cavity FET oscillator

A new single-tuned oscillator, applicable to power combining circuits, is described in which a probe antenna is used to provide coupling between an active device and the cavity. It is shown that output power, oscillation frequency and injection locking range of the oscillator can be controlled independently in the circuit design. The experiments with low-power FET oscillators demonstrate output power of 44 mW at 9.2 GHz and DC-RF conversion efficiency of 33.2% from a single-device oscillator and about 100% of power combining efficiency in the case of two- and three-device circuits.     

低互耦星载相控阵天线设计

介绍了一款工作于Ku频段的低互耦星载相控阵天线的设计方法, 采用在阵列单元周围加载金属腔体的方式降低阵列单元之间的互耦效应, 从而改善相控阵天线的方向图扫描特性.针对相控阵天线在二维±60°范围内低副瓣波束扫描的特点, 对5×5子阵和16×16阵列进行了研究, 验证了阵列的互耦降低方法的有效性和电性能.研究结果表明:相控阵单元间互耦小于-16 dB, 而相控阵单元在15.1~16.8 GHz电压驻波比小于2, 相对带宽11%;在频率为f₀±500 MHz范围内, E面3 dB波束宽度大于98°, 5 dB波束宽度大于113°, H面3 dB波束宽度大于113°, 5 dB波束宽度大于122°.在仿真设计的基础上, 研制了子阵天线试验样机, 测试结果与设计结果吻合良好, 证明了降低互耦方法的有效性, 天线单元方向图满足在±60°范围内波束扫描的要求, 可应用于相控阵雷达系统.     

Dual-Polarized Broadband Array Antenna With BOR-Elements, Mechanical Design and Measurements

A dual polarized broadband phased array antenna designed for the frequency range 6-18 GHz, a 45deg conical grating lobe free scan volume and equipped with BOR-elements developed by Saab is presented. The aim with this array element is to bring about a dual polarized broadband array antenna that is easy to assemble, disassemble and connect to active microwave modules. Disassembling may be important for maintenance and upgrade reasons. Mechanical design and electromagnetic performance in the form of active reflection coefficient, calculated from measured mutual coupling coefficients, and measured active gain element pattern for a central and an edge element is presented. Edge effects in the array, which may be severe in small broadband arrays, are considered in this paper     

Ring-coupled-oscillator sequentially rotated active antenna

In this paper, an active four-element patch antenna, backed by four GaAs monolithic-microwave integrated-circuit (MMIC) 4.4-GHz oscillators, self-locked by mutual coupling through a lumped capacitive ring MMIC network, has been designed, fabricated, and tested. The sequentially rotated arrangement given here when augmented with a lumped capacitive coupling network suggests that in-phase oscillator entrainment is guaranteed so that spatial power combination by the antenna array occurs with circular polarization characteristics     

Active antenna phase control using subharmonic locking

An investigation into using subharmonic injection locking to control the radiated phase or an active patch oscillator is presented. This technique is an attractive locking method and can result in an improved phase control range over fundamental locking. A significant phase control range >360° is experimentally achieved by using a novel element configuration. Results are described and some potential implementation difficulties are noted     

Feeding in-phase dipole arrays: a tutorial and a MATLAB program

Here, we revisit a textbook example of how to design a dipole array and its feed network. The effects of mutual coupling are taken into account, so that a desired set of in-phase excitations is fed to the antenna and radiated efficiently. A MATLAB M-code program, implementing the procedure and plotting the resulting radiation power pattern, is also provided.