Analysis of transmit beamforming performance on multiple-transmit binary ZCZ waveforms

The Transmit BeamForming (TBF) technology, applied in a multiple-transmit radar system, is studied in this paper, where multiple elements of antenna array transmit binary Zero Correlation Zones Orthogonal Signals (ZCZ-OS) independently. For each Direction Of Arrival (DOA) with respect to the transmitting array, the analysis on the gain and sidelobe level of TBF output is presented. This paper focuses on the range sidelobes performance within the main beam (in angle domain). For the normal direction, due to the inherent phase property of ZCZ-OS, the TBF output has part zero sidelobes area, of which the distribution is discussed. For the other directions, a systematic search algorithm to optimize the transmission order of signals is proposed for an optimal relationship chart of DOA and transmission order. The range sidelobe performance within the main beam can be improved as the optimal transmission order is adopted.     

Research on performance influence of direct-path signal for DVB-S based passive radar

Passive radar detects moving targets by Cross Ambiguity Function (CAF), which is based on the cross correlation process of the direct-path signal in reference channel and echo signal in receive channel. Thus, the performance of direct-path signal is important to system performance for this type of radar. While the Signal to Noise Ratio (SNR) of direct-path signal is low, it will deteriorate the detection performance. In this paper, how SNR of direct-path signal induces degradation on the SNR of CAF, and how the integration gain affects by integration time are analyzed, both with theoretical analysis and numerical simulation, which are valuable for the R&D of passive radar.     

A new data extrapolation algorithm for high resolution ISAR imaging

A new data extrapolation algorithm for high resolution radar imaging is presented. The backscattered data are modeled as an autoregressive process where the prediction coefficients are computed using 1D least-square lattice filters. Unlike the well-known Burg or modified covariance methods, least square lattice modeling yields different prediction coefficients for forward and backward directions. The proposed method does not need to satisfy Levinson recursion, i.e. does not suffer from the limitations of the Burg method such as spectral splitting or bias in the locations of the scattering centers. Moreover, due to its lattice structure it does not need any matrix inversion like the modified covariance method. Results obtained for an experimental target are included to confirm the proposed algorithm.     

Range-Based Sleep Scheduling (RBSS) for Wireless Sensor Networks

Sleep scheduling in a wireless sensor network is the process of deciding which nodes are eligible to sleep (enter power-saving mode) after random deployment to conserve energy while retaining network coverage. Most existing approaches toward this problem require sensor’s location information, which may be impractical considering costly locating overheads. This paper proposes range-based sleep scheduling (RBSS) protocol which needs sensor-to-sensor distance but no location information. RBSS attempts to approach an optimal sensor selection pattern that demands the fewest working (awake) sensors. Simulation results indicate that RBSS is comparable to its location-based counterpart in terms of coverage quality and the reduction of working sensors.

雷达伺服系统船摇隔离度的模拟测试方法

船载雷达伺服系统在跟踪目标的同时,还要消除船体摇摆的影响。利用陀螺稳定回路构成的二轴稳定系统是伺服系统消除船摇影响、保持稳定跟踪的一种有效方法。采用隔离度的概念来衡量伺服系统抵消船体姿态扰动、保持天线指向的能力。文中通过模拟速率陀螺敏感的船摇引起的天线方位或俯仰角的变化速率,叙述一种在地面上进行船摇隔离度的测量方法,并通过计算机仿真说明该方法的可行性。     

高频雷达机动目标的时频图像处理方法研究

高频雷达机动目标检测实为复杂外部环境和强地海杂波下的非平稳弱信号处理,针对非平稳特征提出了基于时频分析和图像处理的方法.首先应用时频分析方法得到机动目标的时频谱,进而在时频谱上进行频率维的恒虚警检测并形成目标像、在时间维应用区域生长技术提取目标的速度时变脊线.时频图像处理方法经频率维和时间维的多级处理、在保证系统检测性能的情况下可精确提取机动目标的速度时变信息.实测数据的处理验证了其有效性.     

光速量化取值对有源雷达校准的影响

针对采用有源雷达校准仪对雷达校准时偶有距离误差且呈现规律变化的现象,通过分析雷达有源校准技术原理和校准技术方法,提出了一种校准数据实时修正算法,可用于消除雷达光速量化取值导致的这种雷达距离系统误差影响。经实际验证,满足工程实际应用需求。     

箔条干扰显示建模与实现

分析了箔条雷达散射截面,讨论了箔条干扰在平面位置显示器（PPI）上的显示,建立了箔条干扰显示模型,最后实现了箔条干扰PPI动态显示,并对显示的有效性进行了验证。     

Loopus opens a new dimension in satellite communications

Without any doubt the geostationary orbit is for many applications the most suitable orbit because of the apparent standstill of its satellites. Unfortunately geostationary satellites cannot illuminate the polar regions and furthermore the number of orbit positions is limited. With satellites on certain, dependent on the system, circular or elliptical orbits inclined against the equatorial plane, it is possible to form, off the geostationary orbit, loop-shaped quasi-positions—referred to as Loopus positions—which are served by satellites of alternate identity. The basic idea is to employ in shift several satellites along the same apparent track which, in the alternate play with the earth's rotation, form small loops at the celestial sphere. Change-over takes place at the loop intersection point where a collision of the two satellites is just avoided. Thus a system with for example three satellites, which serve two Loopus positions, allows uninterrupted (quasi-)stationary communication via earth-stations in two coverage zones.     

An angular distribution function for the sputter-depositing atoms and general equations describing the initial thickness profile of a thin film deposited inside a via and trench by sputtering

We developed an angular distribution function that describes the distribution of directional sputter-depositing atoms: g(θ) = (k sin²θ + k⁻¹cos²θ)⁻², where k is a directionality factor that determines the directionality of depositing atoms and θ is the incident angle of a depositing atom. The thickness profiles of the sputtered films deposited inside a vertical trench were simulated using the ballistic transport reaction model in conjunction with the angular distribution function, g(θ). The simulated thickness profile agreed well with the experimentally measured thickness profile. General equations that describe the thickness profile of sputter-deposited films inside vias and trenches were derived. The initial film thickness profile could be predicted by substituting the directionality factor, k, and the geometric parameters of the via or trench in the general equations. An optimum directionality factor, defined as the directionality factor that maximizes the sidewall coverage of a vertical pattern, was obtained by solving the general equations. An ideally-tapered via that maximizes sidewall coverage was identified by optimizing the directionality factors and aspect ratios of the vias.