Space-fed subarrays using displaced feed

An antenna system with an objective lens and phase shifters at each output radiating element, combined with a multiple beam feed network, is known to provide a set of overlapped subarrays for broadband beam steering. Such systems require extremely high dynamic range from any T/R module used at the front-face of the feed. Here, it is shown that by displacing the feed array and refocusing the individual subarrays, the dynamic range and power distribution problems can be avoided.     

Electromagnetic scanning three element array with integral phaseshifters

A structure is presented for a three element beam scanning array where integrated phase shifters are fabricated on ferrite plugs inserted into a microstrip feed network. A combination of permanent magnets and electromagnets are used to achieve beam steering of 30° with coil drive currents of 2A     

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.     

Voltage-controlled ferroelectric lens phased arrays

A new concept for phased arrays is proposed using a voltage-controlled ferroelectric lens. The ferroelectric lens concept uniquely incorporates bulk phase shifting-the array does not contain individual phase shifters-using ferroelectric material. This will reduce the number of phase shifters from (n×m) to (n+m), where n is the number of columns and m is the number of rows in a phased array. The number of phase shifter drivers and phase shifter controls is also significantly reduced by using row-column beam steering. Thus, the ferroelectric lens concept can potentially lead to low-cost phased arrays. This paper presents the ferroelectric lens concept, theoretical analysis and design, and experimental results. The results indicate that the ferroelectric lens concept is viable and sound. Various phased-array configurations using ferroelectric lens are included. A discussion on ferroelectric materials is included along with information on a US Department of Defense program to improve ferroelectric materials     

一种基于压控移相技术的低成本相扫天线

研制了一种基于铁电体压控移相技术的低成本相扫天线阵列,该天线采用空间馈电透镜型式,省去复杂的馈电网络,减少移相器/TR组件数量,能显著降低相控阵天线的制造成本。介绍了空馈铁电体透镜相控阵天线系统的组成及其特点。对透镜天线关键部件的设计作了详细阐述,给出了12列铁电体空馈透镜天线阵列的实验结果,结果表明:在X波段,研制的铁电体透镜天线阵列在10%频带内可实现天线波束±45°的电控扫描,各扫描状态的输入驻波比小于1.4。     

Analysis of phased array lenses

An equivalent network representation of a feedthrough lens array, which takes into account mutual coupling between the array elements, is presented. The model is employed to predict performance characteristics, which include element mismatch, peak voltage loading of the phase shifters, element currents, and transmitted power. Both analog and digital phase shifters are treated in the analysis. It is shown that, irrespective of the type of phase shifter, the mismatch from element to element at a fixed scan angle is not identical. This variation is explained in terms of the multiple reflections that take place between the two surfaces of the lens. Further, as a function of scan angle, the element mismatch for a digitally phased array lens does not vary in a smooth manner but exhibits a decided ripple.     

Piezoelectric transducer controlled multiple beam phased array using microstrip Rotman lens

A simple and low-cost multiple beam phased array is designed using a microstrip Rotman lens and multi-line phase shifter controlled by a piezoelectric transducer (PET) at Ka-band. A microstrip Rotman lens with five beam ports and nine array ports is used as a feed for a multiple beam antenna array to generate five beams centered at the angles of 0/spl deg/, /spl plusmn/15/spl deg/, and /spl plusmn/30/spl deg/. The lens fed nine-element patch array shows the antenna gain of 10 dBi and sidelobe suppression of 10 dB. Each beam is steered over /spl plusmn/8/spl deg/ using two PET-controlled phase shifters, and the five beams cover /spl plusmn/38/spl deg/ from the broadside.     

Electrically Steerable Single-Layer Microstrip Traveling Wave Antenna With Varactor Diode Based Phase Shifters

The design of electrically steerable traveling wave microstrip antenna arrays is presented. Varactor diode based phase shifters implemented on the same metallic layer as the patch elements are used to provide a variable progressive phase shift in the array. Two antennas for the 5.8 GHz ISM band, manufactured as single layer printed designs on a standard PTFE soft substrate, are demonstrated. A ten-element beam-tilting vertical array using transmission type phase shifters is realized, yielding between 11.8 to 13.9 dBi gain for the 0deg to 11deg beam tilt tuning range. Using wide phase tuning range reflection type phase shifters a five-element horizontally scanning array with -32deg to 32deg steering range and 10.9-11.3 dBi gain has been realized.     

遗传算法在天线阵自适应算法中的应用

本文采用一种新的基于遗传算法的天线阵列的自适应算法。根据实际的硬件限制,不改变阵列的幅度加权,而通过遗传算法对相位加权作全局优化。为减小对天线方向图的破坏,并希望在干扰源来波方向实时置零,因而采用只优化搜索数字移相器的最后几位。计算机模拟结果证实了这种方法的有效性。     

Feasibility study on beam-forming technique with 1-D mechanical beam steering antenna using niching genetic algorithm

Recently, mechanical beam steering microstrip patch array antenna was fabricated using MEMS technology, and its pattern measured by experiment. As one of its applications, the authors propose a new beam-forming method without phase shifters. Based on the radiation pattern of the element antenna, niching genetic algorithm adopting restricted competition selection (RCS) is used for the optimal synthesis of the desired radiation pattern. The proposed method successfully generates the desired beam pattern by controlling the current and angle of the element antenna.     

Antenna-coupled microwave phase shifters using GaAs varactors

Electronic beam steering using a space-fed array of antenna coupled phase shifters is reported. The principle of phase shifter operation is described, and typical results are presented.<>     

Adaptive nulling in monopulse antennas

Theoretical and experimental results are presented for phase-only nulling in low-sidelobe monopulse antennas. Both results are based on a gradient search algorithm that simultaneously searches for a minimum in the sum and difference channel output powers. The array's beam steering phase shifters double as the adaptive weights. Each element in the gradient is found by changing phase shifter setting by ΔΨ (the phase shifter stepsize) and measuring the change in output power. Then the phase shifter is restored to its original value, and the process repeated for all the remaining array phase shifters. The algorithm iterates as long as each new adaptive weight setting reduces the total output power. If the output does not go down, then ΔΨ is decremented by one setting and the iteration is started again. The algorithm stops when ΔΨ=0. The adaptive weights act as random perturbations to the phase taper of the array. Consequently, the sidelobe level is proportional to the size of the phase perturbations and inversely related to the number of elements. By keeping the adaptive phase shifts small, the average sidelobe level and the main beam gain do not drastically change     

Null steering in phased arrays by controlling the positions of selected elements

A new technique is presented that is capable of steering s in the antenna pattern in the directions of strong interference signals without affecting the main beam. The technique is based on the element position perturbations of selected elements of the antenna array. This technique frees the phase shifters to be used solely for steering the main beam toward the direction of the desired signal. It also freezes the positions of those elements that have insignificant contributions to the s. Our results have shown to be comparable to the results obtained from the method of controlling the positions of all elements.     

Phase-interpolation locking: new technique for beam-steered active antennas

A new method of phase control for beam steering an active antenna array is suggested. Only half the normal number of phase shifters are needed, but there is a limit to he angle throught whih the beam ca be steered by this technique.     

Concept of an interlaced phased array for beam switching

A novel concept is described for feeding and phasing a large linear array of N antenna elements using only three or five feed points and phase shifters and still achieving beam switching. The idea consists of drastically reducing the number of input points by interlacing a small numer of serially fed subarrays which are suitably phased. This so-called interlaced phased array (IPA) concept was tested using an array of 15 four-element Yagi antennas with a spacing equal to 0.8 wavelengths and found feasible. Some of the distinct advantages of the IPA in comparison with a conventional system of beam switching are reduced power loss, reduced phasing errors, reduced cost, increased reliability resulting from greatly reduced number of phase shifters, and better symmetry of off-zenith beams     

Nonlinear antenna technology

Nonlinear antennas combine advances in nonlinear dynamics, active antenna design, and analog microelectronics to generate beam steering and beam forming across an array of nonlinear oscillators. Nonlinear antennas exploit two phenomena typically shunned in traditional designs: nonlinear unit cells and interelement coupling. The design stems from nonlinear coupled differential equation analysis that by virtue of the dynamic control is far less complex than the linear counterparts by eliminating the need for phase shifters and beam forming computers. These advantages arise from incorporating nonlinear dynamics rather than limiting the system to linear quasisteady state operation. A theoretical framework describing beam shaping and beam forming by exploiting the phase, amplitude, and coupling dynamics of nonlinear oscillator arrays is presented. Experimental demonstration of nonlinear beam steering is realized using analog microelectronics     

Improvement for the steering performance of liquid crystal phased array

Optical phased array technology is introduced and the steering performances of liquid crystal phased array are discussed, several factors affecting the beam steering performances are analyzed completely, also simple models for some typical factors are developed. Then, a new method based on iterating and modifying the output phase pattern of liquid crystal phase shifters is proposed. Using this method, the modified voltages applied on electrodes of liquid crystal phase shifters can be obtained, after applying the voltages, the influence of factors can be compensated to some extent; the steering angle accuracy and efficiency with liquid crystal phased array can be improved. Through the simulation for the angle range from 0° to -1 °, the error of steering angle can be reduced three orders of magnitude, and the efficiency can be increased almost 30% after several iterations.     

Sidelobe-reduction techniques for phased arrays using digital phase shifters

Through the introduction of a new parameter the radiation pattern of a phased array using digital phase shifters for beam steering can be made periodic, and pattern considerations can be confined to a very narrow range of the scan angle. Arrays designed on the basis of a least mean-square pattern error are shown to require the smallest absolute values of a phase-index function. A systematic and easy-to-apply method is developed for reducing the peak sidelobes of nonreciprocal phased arrays by one-step phase adjustments in certain elements. The amount of possible sidelobe reduction depends on the scan angle and the size of phase-quantization steps. Typical examples for 4-bit phase shifters show that reductions in excess of 9 dB are possible for certain main-beam directions.     

A beam-forming network for a circular switched-beam phased arrayantenna

This paper reports on the design and development of a dividing/phasing network for a compact switched-beam array antenna for land-vehicle mobile satellite communications. The device is formed by a switched radial divider/combiner and 1-bit phase shifters and generates a sufficient number of beams for the proper satellite tracking     

X‐Band Phased Array Antenna Using Ferroelectric (Ba,Sr)TiO3 Coplanar Waveguide Phase Shifter

A phased array antenna was fabricated using four‐element ferroelectric phase shifters with a coplanar waveguide (CPW) transmission line structure based on a Ba0.6Sr0.4TiO3(BST)/MgO structure. Epitaxial BST films were deposited on MgO (001) substrates by pulsed laser deposition. To attain the large differential phase shift and small losses for a ferroelectric CPW phase shifter, an impedance‐matching‐part adding technique between the effective transmission line and connecting cable was used. The return loss and insertion loss for this technique‐adapted BST CPW device were improved with respect to those for a normal BST CPW device. For an X‐band phased array antenna system consisting of ferroelectric BST CPW phase shifters, power divider, dc block, patch antenna, and programmed dc power, the steering beam could be tilted by 15° in either direction.