Modified Microwave Sampling Beamformer for Fast Weighting Control and Image Rejection

Abstract

Fig. 6. Radiation patterns before compared to after calibration of an antenna. bracket is important for calibration. The double-line should be tightened and in parallel with the antenna by adjusting the bracket, so as to ensure stable measurements. V. EXPERIMENTAL RESULTSA calibration system with the transmission double-line was used to measure each element phase of a test X-band active phased-array antenna which is composed of 256 (32 2 8) elements in the case of H = 3 mm and L = 0 mm. In the test antenna, there is only one excited column-the middle column of 32 elements. The phase of each element was measured respectively by moving the double-line with an electric slide, and switching T/R modules for the purpose of that one element receives test signal and the others do not work. In addition, the phase-array antenna was calibrated with the measurement phases by T/R modules.Radiation patterns before compared to after calibration at the frequency of 9.50 GHz are shown in Fig. 6. The amplitude attenuation and phase shift of each T/R module is controlled to be equal in the process of phase measurement, therefore, the calculated pattern sidelobe is 013.3 dB without any error. In Fig. 6, the pattern sidelobe before calibration is more than 05 dB, and that after calibration through compensating the measured phase errors with T/R phase shifters is less than 012 dB. Experimental results show that the antenna has a poor phase uniformity before calibration and a good performance after calibration. VI. CONCLUSIONThe proposed transmission double-line can be used in the calibration of X-band active phased-array antennas. It has the properties of low attenuation and low VSWR, and the amplitude of transfer function is larger than 040 dB corresponding to the height of several millimeter. A calibration system with the transmission double-line was used to measure each element phase of a test X-band active phased-array antenna. The comparison of the performance before and after calibration indicates that the method may be useful for array calibration. To achieve low sidelobe patterns it is, however, likely that the accuracy of the positioning of the double line needs to be improved. REFERENCES[1] A. M. Shitikov and A. V. Bondarik, "Multi-element PAA calibration with REV method," in

Signal‐to‐noise ratio and time‐modulated signal spectrum in four‐dimensional antenna arrays

“…is the floor function, T is the total modulation time, t k and t k represent the normalised switch-on instant and switch-on duration for the kth element. In fact, U k (t) can be seen as a periodical rectangular pulse train with a duration of T, t k is the start time of the pulse and t k is the duty cycle for each period T p [4,23]. www.ietdl.org…”