Conjugate ESPRIT (C-SPRIT)

In this paper, we present an algorithm to estimate the direction of the arrival angles (DOAs) from noncoherent one-dimensional (1-D) signal sources such as binary phase shift keying (BPSK) and M-ary amplitude shift keying (MASK). The proposed algorithm can provide a more precise DOA estimation and can detect more signals than well-known classical subspace-methods MUSIC and ESPRIT for the 1-D signals. The complexity is the same as that of ESPRIT since the proposed algorithm uses the same array geometry and subarray processing that ESPRIT does. The main differences between the proposed algorithm and the ESPRIT algorithm are as follows: 1) the number of overlapping array elements between two subarrays is equal to M in the proposed algorithm, while in ESPRIT the maximum number of overlapping elements is M-1, where M denotes the total number of array elements, and 2) the proposed algorithm employs the conjugate of rotation matrix (CRM) /spl Phi//sup */ while ESPRIT uses /spl Phi/ with no conjugate for the second subarray geometry.     

半导体光放大器相位共轭光的产生及其应用

本文介绍了在半导体光放大器中,利用四波混频产生相位共轭光的机理、方式以及影响因素;偏振态对共轭光的影响及解决方法及产生有频移和无频移的相位共轭光的方式;并简要介绍了它们在光通信中的应用。     

Circularly symmetric RF commutator for cylindrical phased arrays

A new feed concept is described which greatly simplifies the problem of commutating the RF distribution system of a cylindrical phased array. The feed consists of a circular parallel-plate radial transmission line with a central set of probes and a ring of peripheral probes. The array of probes in the center can be phased to produce an amplitude distribution in the parallel-plate line in any given direction. Proper setting of only two phase shifters connected to the central probes can cause any sector of the peripheral probes to be excited with the proper amplitude distribution necessary to produce a directive pattern with low sidelobes as well as a monopulse difference pattern when the peripheral probes are connected, through collimating phase shifters, to the active radiating elements of a cylindrical array. The cylindrical array can be scanned through360degin fine increments by continued indexing of the amplitude distribution generated by the central probes. ExperimentalLband hardware, built to prove the feed technique, is described. Nine central probes in a 0.25-inch thick 21-in diameter model produced a cardioid distribution and an orthogonal figure-eight distribution which could be commutated together by adjustment of two phase shifters. Measured insertion loss between the central probes and 48 peripheral probes showed only 0.1-dB loss over a 6-percent band. Coupling measurements between the three available central terminals indicated isolation between the various ports of 23-35 dB. The minimum insertion loss and the corresponding transmission phase between the central feed and the peripheral probes was shown to be independent of the setting of the two control phase shifters which were set to have conjugate phase shift.     

Coherent Array of Nonlinear Regenerative Fiber Amplifiers

A coherent array of high power fiber amplifiers (lasers) with a nonlinear refractive index is described and discussed. By adding reflectivity to the inputs of the fibers, each fiber laser is transformed into a regenerative amplifier, with an internal circulating power that varies depending on the round trip phase shift of the field within the fiber. The variation of the internal circulating power results in a preferential shift in the output phase of each amplifier due to the high nonlinearity within the fiber. The resulting phase shift is predicted to substantially compensate for the inherent randomness in the output phase distribution usually associated with the long lengths of fiber amplifiers. The individual outputs of the coherent array are shown to exhibit a ldquofuzzyrdquo phase distribution that can be partially quantified based on a statistical analysis and is dependent on the parameters of the array. A simple example is given of a coherent array of fiber lasers in a Self-Fourier cavity and the degree of coherence is predicted under simplifying assumptions.     

Phased array antenna analysis with the hybrid finite element method

A new analysis technique for infinite phased array antennas was developed and demonstrated. It consists of the finite element method (FEM) in combination with integral equation radiation conditions and a novel periodic boundary condition for 3-D FEM grids. Accurate modeling of rectangular, circular and circular-coaxial feeds is accomplished by enforcing continuity between the FEM solution and several waveguide modes across an aperture in the array's ground plane. The radiation condition above the array is enforced by a periodic integral equation in the form of a Floquet mode summation, thus reducing the solution to that of a single array unit cell. The periodic boundary condition at unit cell side walls is enforced through a matrix transformation. That mathematically “folds” opposing side walls onto each other with a phase shift appropriate to the array lattice and scan angle. The unit cell electric field is expanded in vector finite elements. Galerkin's method is used to cast the problem as a matrix equation, which is solved by the conjugate gradient method. A general-purpose computer code was developed and validated for cases of open-ended waveguides, microstrip patches, clad monopoles and printed flared notches, showing that the analysis method is accurate and versatile     

采用双相位共轭干涉法测定光折晶体中折射率光栅相移的原理

在理论上证实了采用双相位干涉法直接测定光折晶体内折射率光栅相对于光强分布的相位移和非线性介质三次非线性极化率相位的可能性。     

Experimental Investigation of a Retro-Focusing Microwave Hyperthermia Applicator: Conjugate-Field Matching Scheme

A seven-element array of dielectric-loaded open-ended waveguides totally immersed in a water tank is tested as a possible hyperthermia applicator. Experimental results show a substantial increase in focusing ability of the array if a conjugate matching scheme is used to adjust the phase of each element excitation. This scheme could offer a practical procedure for operating a focused hyperthermia applicator in a living patient.     

Electromechanical controlled phased array dumbbell EBG beam steerer

A steerable phased array antenna driven mechanically is realized by utilizing the variation of dumbbell electromagnetic bandgap (EBG) structures. The variation takes place under the feed line of a 4-element array that gives the change in relative phase shift. The phase shift achieved from different shaping combinations of EBGs shifting under the feed lines. The feed lines are connected with four microstrip patches to yield a 4-element phased array antenna. The mechanical controlled pattern shapes of phase array antenna are simulated in electromagnetic (EM) software Zeland IE3D. Finally the design is fabricated with the help of optical lithography. It can be seen that the beam steering angle can be controlled mechanically without phase shifter and PIN switches.     

A new Millimeter-wave printed dipole phased array antenna using microstrip-fed coplanar stripline tee junctions

A new millimeter-wave printed twin dipole phased array antenna is developed at Ka band using a new microstrip-fed CPS tee junction, which does not require any bonding wires, air bridges, or via holes. The phased array used a piezoelectric transducer (PET) controlled tunable multitransmission line phase shifter to accomplish a progressive phase shift. A progressive phase shift of 88.8/spl deg/ is achieved with the 5 mm of perturber length when the PET has full deflection. Measured return loss of the twin dipole antenna is better than 10 dB from 29.5 to 30.35 GHz. Measured return loss of better than 15 dB is achieved from 30 to 31.5 GHz for a 1/spl times/8 phased array. The phased array antenna has a measured antenna gain of 14.4 dBi with 42/spl deg/ beam scanning and has more than 11 dB side lobe suppression across the scan.     

A 20 GHz Steerable Array Antenna Using 3-bit Dielectric Slab Phase Shifters on a Coplanar Waveguide

A simple steerable array antenna is designed and developed using a movable dielectric phase shifter. The change of effective dielectric constant at different dielectric slab positions on a coplanar waveguide is used as the phase shifter. The impedance matching and desired phase shift conditions are satisfied at two slab heights, and the reflection is designed to be minimized at these slab positions. The low-loss dielectric material is used as the dielectric slab and is placed close to a coplanar transmission line with airgap. The 4times4 steerable array antenna with the phase shifters is designed and fabricated at 20 GHz. The H-plane radiation patterns are measured at different phase shift positions and compared with the expected results     

A new phase-shifterless beam-scanning technique using arrays ofcoupled oscillators

A method for electronic beam scanning in linear arrays of antenna-coupled oscillators is introduced which eliminates the need for phase shifters. It is shown that a constant phase progression can be established by slightly detuning the peripheral array elements, while maintaining mutual synchronization. This unusual nonlinear behavior is explained using coupled Van der Pol equations. A stability analysis provides theoretical limitations on the achievable interelement phase shift. When the phase of the coupling is zero, the theory predicts an interelement phase shift that can be varied continuously over the range -90°>Δ&thetas;<+90° and is independent of the number of oscillators in the array. An experimental four-element planar MESFET array was built, operating at 10 GHz with close to zero coupling phase, giving a measured phase progression that was continuously variable over the range -88°<Δ&thetas;<66°     

An antenna beam steering technique comprised of constant-phase array elements

Beam steering is normally achieved by the use of phase shifters at each element of an array. The phase taper thereby produced causes a shift of the far-field pattern in sin θ space. An alternate approach to beam steering is presented in which a pair of interleaved arrays are employed. One array of the pair is fed entirely by currents of zero phase, while the other array is fed entirely by currents of quadrature phase. Beam steering is done by control of amplitude at each element. An example of this technique is presented and discussed.     

Indirect Controlled Phased Source

We propose here a novel phase controllable oscillator to realize phase shift for the phased array. The phase of the oscillator is controlled by the phase of reference frequency of a phase locked loop. Since the reference frequency is usually lower than 100MHz, the phase shifting can be much easier, have a lower cost, and be more accurate than that in microwave phase shifters. A four-element scanning array antenna using this novel phase control technique is demonstrated with a scanning range of plusmn40deg in this letter     

TR组件S参数自动测试软件的设计和应用

为了实现TR组件S参数测试的自动化,分别建立了接收和发射S参数自动测试系统,使用VISA-COM和SCPI命令对仪器进行编程,重点阐述了在脉冲状态下实现TR组件移相和衰减全自动化测试的方法,并介绍了TR组件移相数据处理软件的设计。该方法在有源相控阵天线的自动化测试上得到成功应用,论述了在有源相控阵天线配相自动化测试系统的应用情况。该自动化测试技术具有准确方便快速等特点,在工程实践中取得了良好的效果。     

相控阵雷达激励器的设计

介绍相控阵雷达移相器的激励控制原理和方法，依据移相器的控制特点提出设计要点，以提高激励器的可靠性、降低激励器的功耗。     

Phase Shifter for a 915 MHz Phased Array Hyperthermia System

This paper describes a design for an analog phase shifter operating at 915 MHz and suitable for use in a phased array microwave hyperthermia system. Here, the major operating constraint was minimization of amplitude variation over a 1800 phase shift, whereas previous phase shifters were designed to obtain a linear relationship between phase and control voltage. The result is a simple, inexpensive hybrid coupler phase shifter that operates over a narrow bandwidth and provides 180°of continuous phase shift with input powers up to 1 W.     

Predicted performance of magnetized semiconductor phase shifters for millimeter-wave microstrip array antennas

The tunable phase shift of a planar magnetized semiconductor phase shifter is presented, suitable for an integrated environment due to its miniature size, low-biasing requirements, and lower material related problems at millimeter-wave frequencies. A linear microstrip phased array antenna with an integrated semiconductor phase shifter is designed and the calculated beam steering properties are tabulated. The design process is verified by simulating similar ferrite-based linear phased array antennas.     

一种基于共轭矩阵的阵列扩展技术

提出了一种新的基于共轭矩阵的阵列扩展技术,该技术可以对阵列的信号子空间进行扩展,从而可以估计更多的信号波达方向(DOA)。该方法首先对接收的阵列信号进行二阶统计量预处理,利用自相关函数的性质获得导向矩阵的共轭矩阵,然后构造出一个新的伪快拍扩展矩阵,通过对该矩阵运用MUSIC-like算法可以比传统的MUSIC-like算法估计出的波达方向个数多50％,理论分析和仿真实验证明了本文结论。     

基于线阵CCD阵列的在线检测方法

利用矩形光栅离焦投影,产生正弦光场,通过三个严格排列的线阵 ＣＣＤ阵列对物体三维轮廓进行扫描采样测量,一次扫描就可以获得三幅相位图。利用三步相移技术即可解调高度信息,避免测量过程中的相移操作。本文重点讨论了该方法的原理和特点,并给出试验简图及实际测量结果。     

宽带相控阵雷达的波控系统设计

宽带相控阵雷达要求波控系统不仅能完成窄带方式下的移相控制,还应具有宽带方式下的延时控制,实现雷达系统高分辨探测.文中采用了"广播式传输、分布式运算"的波控系统方案,设计了基于数字信号处理器(DSP)的波束控制器,完成波束的实时运算和相位控制,在子阵级和单元级实现了宽带方式下延时控制算法,并在工程上得到了验证.