Baoyan Duan

Analysis of performance of active phased array antennas with distorted plane error

The analysis of the degradation of electromagnetic performance of active phased array antennas (APAA) with distorted plane error is an important factor for manufacturing high-performance antennas. To obtain the relation between the plane distortion and electric index to provide significant guidance for the engineer, a coupled structural-electromagnetic model of an APAA is developed, which describes the effect on the performance of the distorted plane error caused by the bent and bowl shape distortion in the radiated element position. The application of the model to a planar APAA demonstrates the degradation of the sidelobe level and gain of antenna with different distortion grades. The satisfactory results provide a theoretical guidance for the engineer to determine the structural tolerance.

Mechatronics design of stiffness enhancement of the feed supporting system for the square-kilometer array

Design and implementation of stiffness enhancement of a feed supporting system for the square-kilometer array (SKA) using electrorheological (ER) variable damper is presented in this paper. The feed supporting system consists of a large parallel cable manipulator and a fine-tuning Stewart platform. Hence, the feed supporting system is a large delay system and sensitive to the influence of wind. Furthermore, the adjustment of the fine-tuning Stewart platform will affect the coarse tracking control. Therefore, in order to suppress these disturbances and realize the independent control of the two parallel manipulators, it is necessary to enhance the stiffness of the feed supporting system. The proposed ER variable damper is designed and directly attached to the shaft of the servomotor of the feed supporting system to achieve high servo stiffness and trajectory tracking accuracy. The model of the feed supporting system is first derived, the structure of the variable-viscous ER damper is presented, and then the damping coefficient model is developed. The validation of this stiffness enhancement design of the feed supporting system is demonstrated with position PD control of the feed supporting system. This result has built a solid base for the accomplishment of the high-accuracy requirement of the SKA.

On the performance of array antennas with mechanical distortion errors considering element numbers

ABSTRACT Mechanical distortion errors in active phased-array antennas (APAA) include both random error and mechanical distortion. Random error is generated during the manufacturing and assembly process, and mechanical distortion is caused by external loads such as high thermal difference, vibration and impact loads. The combination of random error and mechanical distortion results in unexpected and significant degradation of the antenna electromagnetic performance, which has become an obstacle to development of high-performance APAA. After introducing the mechanical distortion errors into the antenna electric field as an additional phase factor, a coupled structural-electromagnetic model of the planar rectangular APAA was developed to describe the coupling relationship between mechanical distortion error and electromagnetic performance. The combined influences of the radiated element numbers, mechanical distortion and element position random error on the antenna electromagnetic performances are analysed, and valuable results for engineering application are discussed.

Homology Parameters for Large Axisymmetric Shaped Dual-Reflector Antennas

We extend the concept of best-fitting paraboloids for large single and dual reflectors with conic-section surfaces to best-fit shaped surface for large dual reflectors shaped for uniform amplitude distribution. The point focus of the paraboloidal main reflector is replaced by focal lines for the main reflector and the primary subreflector focus, whereas the secondary subreflector point focus at the feed is kept. The reflector surfaces are shaped, and all rays from the main-reflector aperture to the feed meet an equal-path-length condition. This condition may be represented by a set of “homology parameters” determined by a least-squares method. Finally, we calculate the homology parameters and the root mean square of surface errors for an 8-m dual-reflector system including gravity effects for the antenna pointed toward zenith and the horizon.

A New Interval Pattern Analysis Method of Array Antennas Based on Taylor Expansion

In this communication, a new Taylor expansion-based interval pattern analysis method is developed to predict the impact of the small excitation amplitude uncertainty on the radiated array pattern. The dependence problem of the classical interval arithmetic, which may lead to overestimation of performance intervals, is addressed in this communication. The proposed method approximates by approximating the antenna power values to the first order with respect to the uncertain amplitude. The new method is simpler and can produce more accurate bounds of the antenna pattern and the pattern features than the existing techniques. Several representative numerical examples are investigated to demonstrate the validity and efficiency of the proposed method.

Study of Stepped Amplitude Distribution Taper for Microwave Power Transmission for SSPS

A novel stepped amplitude distribution (SAD) taper for microwave power transmission for space solar power satellite is proposed in this paper. The SAD taper is described by the summation of the Heaviside step functions. Through optimizing the “height” and “radius” of each step of the descriptive function, the maximal beam collection efficiency (BCE) with and without constraints on the radiation levels can be obtained. A large set of numerical experiments on continuous apertures and discrete antenna arrays are carried out. The results show that the obtained BCEs can be close to or even higher than those of the 10-dB Gaussian ones, which shows the superiority of the method. In addition, only several kinds of amplifiers are required in this method, and therefore, the cost and complexity of the system can be greatly reduced.

Shape pre-adjustment of deployable mesh antennas considering space thermal loads

On-orbit space deployable antennas withstand periodic thermal loads, which will degrade the antenna surface accuracy. Thus, it is necessary to preliminarily adjust the antenna before launch to make it adapt to the space temperature environment as much as possible. Aiming at this problem, a pre-adjustment method based on min-max concept is presented in this study. First, according to the force equilibrium equation of the cable element, the incremental equilibrium equation of the cable mesh antenna is derived, and the incremental expressions of the reflectors surface displacement and cable tension with respect to cable length variation and element temperature variation are also developed. Then, the optimization model for shape pre-adjustment is established using min-max method, and the pre-adjustment process is implemented by sequence planning strategy. Finally, an AstroMesh antenna is employed to demonstrate the validity of the method.