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A broadband waveguide slot filtenna array with low cross polarization and high efficiency is presented for dual-polarization applications. The vertical polarization radiation is achieved by offsetting longitudinal slots on the ridged waveguide, while the horizontal polarization radiation is achieved by V-shaped slots on the ridged waveguide. Two polarization ridged waveguide linear arrays combine to obtain dual-polarized radiation with cross-polarization levels under −43 dB in wide angles. To extend the bandwidth of the array, each $1 \times 16$ -element linear array is separated into two $1 \times 8$ -element arrays, which are fed by a two-way ridged waveguide divider via H-shaped slot couplings. The evanescent-mode ridged waveguide filters are integrated into a two-way ridged waveguide divider that suppresses the out-of-band signal interference. The signals of the interference bands are suppressed effectively, which are −25 dB lower than that of the operation band. Furthermore, 16 pairs of dual-polarized linear arrays are designed, fabricated, and measured. The results show that the array has perfect properties such as bandwidth, polarization purity, efficiency, and immunity to interference.

The low permeability of unconventional gas reservoir makes it difficult to achieve good development effect. Hydraulic fracturing technology and multi-lateral well technology are usually adopted to increase the gas production. What's more, the permeability may change dynamically during the production process because of the effective stress, gas slippage and matrix shrinkage effect. In this paper, we first establish the productivity equation of radial multi-branch horizontal (RMBH) well in unconventional natural gas reservoirs, considering the dynamic change of permeability during the production process. Then, the productivity equation of radial horizontal well with 2 branches is compared with fractured vertical well and conventional horizontal well productivity equations proposed by former researchers. Finally, main factors influencing the productivity of unconventional natural gas RMBH well are analyzed, including well structure parameters, gas formation properties and production stage. Results show that the productivity equation of degenerated RMBH well with 2 branches is proven to be reasonable by comparison with those of vertically fractured well and horizontal well. RMBH well shows more advantage in the formation with relatively large difference between maximum and minimum stresses, indicating that this type of well configuration may be an alternative technique for improving gas production in unconventional gas reservoirs. Sensitivity analyses demonstrate that the gas production rate of RMBH well is sensitive to branch length, branch number, build-up section horizontal distance, and stress dependence effect. The radial horizontal well with 4 branches can achieve a best development effect and economical benefit.

A novel waveguide slot filtering antenna with an embedded metamaterial is presented. This filtering antenna consists of a common waveguide slot antenna with longitudinal slots cut on the top broad wall of its rectangular waveguide and a metamaterial surface embedded in the bottom broad wall. The metasurface replaces the conventional metal plane in the form of a bed of nails. In the operating frequency band, the metasurface works as a perfect electric conductor, so the antenna radiates as the traditional waveguide slot antennas. While in the stopband, the metasurface performs as a perfect magnetic conductor to suppress the propagation of electromagnetic wave in the waveguide cavity, so the interference signal is rejected and a filter function is achieved. To show the design process and verify its feasibility, a filtering antenna prototype working in the $C$ -band and having a stopband in the $X$ -band is designed, fabricated, and tested. A good agreement between simulation and measurement is obtained, demonstrating efficient radiations in the working band and a strong suppression of more than 35 dB in the stopband.

There has been a great development of antenna for synthetic aperture radar (SAR) applications in China in the past dozen years. The active phased array is applied to airborne and space-borne SAR system. As an important component of an array, a brief review on microstrip patch and waveguide slot antenna is presented in this paper mainly.

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.

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.

The different approaches used for target decomposition (TD) theory in radar polarimetry are reviewed and three main types of theorems are introduced: 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 success in many fields. A new algorithm of target classification, by combining target decomposition and the support vector machine, is proposed. To conduct the experiment, the polarimetric synthetic aperture radar (SAR) data are used. Experimental results show that it is feasible and efficient to target classification by applying target decomposition to extract scattering mechanisms, and the effects of kernel function and its parameters on the classification efficiency are significant.

A novel antenna consisting of a C band dual polarized waveguide slot antenna and an L band slot antenna with shared apertures is presented. The antenna meets the requirement of a dual band SAR application.

For the retailing, the shelf space allocation is a key issue which impacts on the retailer's product sales and profits directly. For the small-scale supermarket, due to the small store and the product variety, the traditional “format style” shelf space layout is not appropriate. To solve this problem, a shelf space allocation solution based on data mining techniques is proposed in this paper. With the introduction of association distance, we realize the description of the relevance between two any items purchased together in transaction database. With the concept of promotions coefficient, we get the description of the promotions ability of two items. Based on these concepts, with the cluster analysis techniques and the association rule mining technique, we propose a resolution based on “island style”, and get the optimization and automation of shelf space allocation in the small-scale supermarket.

Taking the journal office automation system as an example, the structure and technologies of development of WWF-Based office automation system are introduced in this paper. The main function, process designing, database designing and key technologies are described in detail in this paper. By this system, the author, editor and expert can process journal papers collaboratively. Also the journal efficiency and paper quality are improved greatly.

Since Huynen's 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.

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.

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.

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.

This paper gives an introduction to a new wideband, high efficiency widebeam, two dimensional shaped beam antenna, and presents the results of a model of this kind of antenna over a 15 percent frequency band on the S-band. The beamwidth (-1.5 dB) of the radiation patterns in the two orthogonal planes are O/sub E//spl ges/50/spl deg/, O/sub H//spl ges/120/spl deg/, respectively. The rippled level at the top of the main beam is better than /spl plusmn/1.0 dB, and input VSWR of the antenna is /spl les/1.20.

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.