Lu Jiaguo

Active phased array antenna based on DDS

The use of active phased-array antenna in communication system can bring about not only improved system performance, but also extended functions, so it has found its ever-broadly applications in communication system. This paper introduces an active phased-array antenna system that has eight antenna elements without RF phase shifters. The antenna system consists of planar array, digital T/R modules, receiving DBF; system control /analysis software, etc. Its basic theory is that in transmitting channel, the traditional RFphase shifter and attenuator are replaced by direct digital synthesizer (DDS). As the operating frequency of DDS available is not sufficiently high, the upper frequency converter is used to convert the frequency to required system operating frequency (2.0 GHz). In transmitting mode, through controlling DDS, the amplitude and phase weights needed for transmit beam formation and the LO signals needed for upper frequency conversion are produced. In receiving mode, through controlling DDS, the LO signals is needed for down frequency conversion for the received signal are produced. The resultant digital I/Q signals are used to form the receive beam. This paper introduces in detail the ways and results of an experiment on an active phased array antenna based on DDS. Through the research on the eight-element active phased array antenna based on DDS, the notable virtues of DDS technology in phased array antenna, and the potential applications of the phased array antenna in communications are proven.

The development of DBF phased array radar system

This paper presents the basic concept and implementation of an 8 element DBF (digital beamforming) phased array radar. The real transmitting patterns with various frequencies, weights and nullings are shown. The receiving pattern is also given.

Design Considerations of The Active Scalable Array Antenna

Based on the developing requirements of universality, multifunction, modularization and low-cost of modern radar, this paper presents a new architecture of active scalable array antenna (ASAA), describes the function characteristics, and gives two potential structures and the corresponding configurations, design rules and design requirements. Also, a developed fabricated X-band RF scalable array module (SAM) is reported in this paper

Algorithm of target classification based on target decomposition and support vector machine

Since Huynens original work, there have been many other proposed target decomposition theorems. In this paper, we provide a review of the different approaches used for target decomposition theory in radar polarimetry and classify three main types of theorems: those based on Mueller matrix, those using an eigenvector analysis of the coherency matrix, and those employing coherent decomposition of the scattering matrix. Support vector machine (SVM), as a novel approach in pattern recognition, has demonstrated a success in many fields. Here we first extract scattering mechanisms of radar targets by target decomposition and color composite. Then we propose a new algorithm of target classification by combining target decomposition and support vector machine. We conduct the experiment on the polarimetric synthetic aperture radar data. Experimental results show that: it is feasible and efficient to target classification by designing SVM classifiers using target decomposition, and the effects of kernel functions and its parameters on the classification efficiency are significant.

A New Algorithm of Target Classification Based on Maximum and Minimum Polarizations

The polarization signature of a given pixel in a radar image represents scattering mechanisms from various scattering elements. This paper presents an analysis of maximum and minimum polarizations of five kinds of polarization signatures: co-polarized, cross-polarized, completely polarized, completely unpolarized, and total available power signatures. We propose a new algorithm of target classification based on these maximum and minimum polarizations, then, conduct the experiment on the measured polarimetric SAR data. Experimental results show that this algorithm is robust to pixel-by-pixel target classification in radar images

Analysis on beam pointing error of RDA for LFM signal repeater jamming

Retrodirective array (RDA) is a new type of array antenna with automatically backtracking function, which has special application value in radar countermeasures. When it is used to jam the linear frequency modulation (LFM) pulse compression radar, the bandwidth of the backtracking signal is broadened by the jamming modulation, resulting in the beam pointing error. A model of repeater jamming using the phase conjugate array is established, and the influences on the beam pointing error of the bandwidth variety, the number of array element, the scanning angle and the leakage coefficient of the phase conjugate circuit are analyzed. The results show that the instantaneous frequency variety of the LFM signal has little effect on the beam pointing error, and the number of array element has a great influence on the beam pointing error. The more the number of array elements, the narrower the beam and the smaller the beam pointing error. With the scanning angle increasing, the beam pointing error is increasing. The variety of the leakage coefficient has a great influence on the sidelobe and gain of radiation pattern. Those results have important guiding significance for the use of RDA in radar countermeasures.

Research of P band circular polarization SAR

For space-borne P band Synthetic Aperture Radar (SAR) application, an airborne experimental circular&linear polarimetric SAR system is developed, this paper presents the instrument and airborne test result. Compared to linear polarization of P band, circular polarimetric SAR shows remarkable penetration efficacy in tropical jungle foliage covered region and subsurface targets detection. Besides, A new phenomenon of P band circular polarimetric SAR implies potential advantage in man-made linear object detection.