Liu Qi-zhong

Optimal design of smart antenna array

This letter investigates an efficient design procedure integrating the Genetic Algorithm (GA) with the Finite Difference Time Domain (FDTD) for the fast optimal design of Smart Antenna Arrays (SAA). The FDTD is used to analyze SAA with mutual coupling. Then, on the basis of the Maximal Signal to Noise Ratio (MSNR) criteria, the GA is applied to the optimization of weighting elements and structure of SAA. Finally, the effectiveness of the analysis is evaluated by experimental antenna arrays.

Analysis and simulation of system phase errors in planar near-field measurements on ultra-low sidelobe antennas

System phase errors are one of the main error sources to influence the precision of planar near-field antenna measurements, especially for planar near-field measurements on ultra-low sidelobe antennas. In this paper, the effect of system phase errors on the results of planar near-field measurements on ultra-low sidelobe antennas is studied by means of theoretical analysis and computer simulation. The analytical expression of the error spectrum in the sidelobe region due to system phase errors is derived and some basic laws and useful results are obtained.

Application of the Window Function in Bistatic Planar Near-Field Scattering Measurements

The cosine window function is introduced and applied in the planar near-field scattering measurements. Based on the basic principle of which, the bistatic planar near-field scattering measurement technique is computer simulated with the infinite long ideal conductor cylinder as the target under test. The calculation results show that in bistatic planar near-field scattering measurements, the finite scanning plane truncation errors of the far-field RCS of the target under test obtained by near-field to far-field transformation can be reduced greatly by the weighting process of the measured scattering near-field with the cosine window function, which proves the validity and applicability of the near-field data processing method by means of the cosine window function in the bistatic planar near-field scattering measurements.

Application of the Window Function in the Plane Wave Synthesis Technique

The cosine window function is introduced and applied in the plane wave synthesis technique. With the infinite long current filament as the scanning probe, the plane wave synthesis technique is computer simulated. The calculation results show that in the plane wave synthesis technique, the uniform degree of the amplitude and phase of the quasi-plane wave synthesized in the body under test zone can be improved greatly by weighting process of the current distribution of the array elements with the cosine window function, which proves the validity and applicability of the weighting method by means of the cosine window function in the plane wave synthesis technique.

Efficient optimization of flat-top patterns using genetic algorithm for the deep space detection application

The optimization of a flat-top pattern of planar 2-D array antenna is proposed in this paper. The shaped-beam planar array is employed to be an element of very large array for the deep space detection. A conventional genetic algorithm is chosen for the optimization. However, the synthesis of a flat-top shaped beam using a planar 2-D array is difficult because of the inherently large number of degrees of freedom involved in the algorithm (in generally, the amplitude and phase of each element must be determined). Therefore, a sub-array rotation method, which lies on the flat-top pattern synthesis itself, is proposed in this study to resolve the design problem. A 10times10 (100) element array is employed, and the results of the optimized flat-top pattern are shown to illustrate the validity and high efficiency of the technique.

Plane wave synthesis based on the Least Square Method

A novel method of plane wave synthesis is presented with the application of the least square method in the plane wave synthesis technique. With the rectangular planar array made up of the half-wavelength dipole elements as the theoretical model of plane wave synthesis, the novel method is used to seek optimum amplitude and phase distribution of array element so as to make the uniform degree of the amplitude and phase of quasi-plane wave synthesized to be the best. The calculation results show that the method presented in this paper requires smaller probe array than the traditional methods in order to ensure the quality of quasi-plane wave synthesized, which proves the correctness and validity of the novel method.

Facet noise in RCS prediction

The facet noise in RCS prediction is studied in this paper. Faster speed of computation and higher accuracy is obtained with a proper facet model build. The number of facets needed to model a target increases with the size of the target and the frequency of the incident wave. The criterion of facetization is discussed and some helpful results are obtained.

Study of self-transmitting and self-receiving monostatic planar near-field scattering measurements

The technique of self-transmitting and self-receiving (STSR) monostatic planar near-field scattering measurements is studied and computer simulated. Calculation results indicate the relative value of monostatic RCS obtained by means of self-transmitting and self-receiving monostatic planar near-field scattering measurements has good engineering precision in an angle range near the outward normal direction of the scanning plane. Finally, several problems that need to be further studied are pointed out.

Application of the Least Square Method in the Plane Wave Synthesis Technique

A novel method of plane wave synthesis is presented with the application of the least square method in the plane wave synthesis technique. With the linear array made up of the infinitely long current filament as the theoretical model of plane wave synthesis, the novel method is used to seek optimum amplitude and phase distribution of array element so as to make the uniform degree of the amplitude and phase of quasi-plane wave synthesized to be the best. The calculation results show that in the case that the size of the region under test remains unvaried, the method presented in this paper requires smaller probe array than the traditional methods in order to ensure the quality of quasi-plane wave synthesized, which proves the correctness and validity of the novel method.

Study of planar near-field measurements methods for determining the gain of the antenna

The coupling equation and the formulas of the far-field pattern of the AUT determined from the near-field data in the case of considering all important proportional factors with the influence of the probe (i.e. the probe compensation) considered are given. Based on this, two methods for determining the gain of the antenna by means of planar near-field measurements, i.e. the absolute method and the comparative method are presented and the corresponding measurement principle and the calculation formulas are given