一种新型雷达天线方位转台

提出一种全新的雷达天线方位转台结构方案。由于所有功能都集中在一台新型的少齿差行星减速器上，所以该方位转台结构紧凑、体积小、重量轻、精度高以及承载能力强，而且有利于模块化设计。     

A deep parametric study of resistor-loaded bow-tie antennas for ground-penetrating radar applications using FDTD

Resistor-loaded bow-tie antennas are analyzed thoroughly to find out their performance on ground-penetrating radar (GPR) applications. The analysis is done with the finite-difference time-domain (FDTD) technique. The antenna is pulse driven and enclosed in a rectangular conducting cavity. The ability to detect a buried conducting sheet using two such identical antennas for transmitting and receiving is investigated. Simulations are carried out for various antenna parameters like end resistor values, flare angle, and antenna length. The gap between the two antennas and their height above the ground are also varied. Moreover, the results are obtained for different sizes, depths, and positions of the buried sheet. It is studied how the broadband impedance characteristics and better target discrimination with low clutter can be achieved by optimally selecting these antenna parameters. Also, it is shown that apart from the total parallel end resistance, the individual end resistor values and the number of resistors connected have no significant effect on the input impedance and the received signal.     

An ultrawide-bandwidth tapered resistive TEM horn antenna

A novel stable beamwidth, ultrawide-bandwidth low-scattering antenna is presented. This antenna is a modified version of the conducting slotline bowtie hybrid (SBH) antenna with resistive sheets (Rcards) introduced into the guiding structure design. Since the resistive sheets can attenuate creeping wave fields, much smaller rolled edges are needed in the Rcard SBH antenna. Moreover, due to the Rcard's partially transparent nature with respect to electromagnetic fields, the radar cross section (RCS) associated with this new antenna is smaller than the original conducting rolled edge one. By employing an optimization process based on the concept of the genetic algorithm, one can easily design the Rcard SBH antenna to obtain a very stable antenna beamwidth and phase center in both the E- and H-planes across the entire operating frequency bandwidth. Because of its constant beamwidth, low RCS, and broad-band features, the Rcard SBH antenna is an ideal antenna for many applications such as a compact range feed. Calculated and measured results are presented to demonstrate the performance of this new antenna     

Complex image model for ground-penetrating radar antennas

A method of combining the complex image method with the constant Q assumption is derived, which enables the calculation of complex image parameters once for the whole frequency range in the general half-space case. The mixed potential method of moments is then used to model horizontal wire dipoles near a lossy half-space, using pulse-basis functions and point matching. The method is demonstrated by the modeling of two types of wire dipole. A conductive half-wave dipole shows excellent agreement with NEC-S. The current distribution of a 3.4 m resistively loaded dipole across the frequency range 0-512 MHz is also calculated and transformed to the time domain. The result agrees with published measurements. The time required on a workstation was reduced to 4/s per frequency point     

超宽带探地雷达自动目标识别研究

超宽带探地雷达由于回波信号信息丰富的特点,特征向量的选取成为了自动目标识别的关键.首先利用宽相关处理进行滤波和典型数据提取.提取纵向和横向典型数据用于目标形状识别;提取典型回波道数据进行功率谱分析用于目标材质识别,并利用RBF网络从而实现目标的自动识别.实测数据处理表明:该方法可有效的完成管状物和球状物、铝和铁的识别.     

W-band high gain lens antenna for metrology and radar applications

A W-band high gain lens antenna has been realised and measured. A hyperbolic lens made in ECCOSTOCK 0005 is associated to an optimised modified circular horn related to a circular-to-rectangular waveguide transition in order to fit the WR-10 standard waveguide. The antenna provides more than 30 dBi gain between 75 and 110 GHz. It is competitive in several fields of applications: first, obstacle detection radar application (at 77 or 94 GHz), secondly metrology, for example, in order to measure radar cross-sections over the whole W-band with a single antenna.     

A numerical study of buried biomass effects on ground-penetrating radar performance

It is widely acknowledged that tree roots and other forms of buried biomass can have an adverse effect on the performance of ground-penetrating radars (GPRs). In this paper, we present analyses that examine that effect for ground-contacting GPR systems. A test site containing extensive root infiltration at Eglin Air Force Base, Florida, was excavated, and the root structure and soil were thoroughly characterized. A numerical simulator based on the discrete dipole approximation, which is an integral-equation-based method, was developed, validated, and subsequently used to compute scattering from root structures modeled by an ensemble of buried cylinders. An examination of the results is presented that quantifies the potential for false alarms and increased clutter due to buried roots.     

A novel antenna for ultra-wide-band applications

An ultra-wideband antenna based on a slotline feed structure, a bowtie horn, and a rolled edge termination was developed, analyzed, and measured. Empirical data showed that its beamwidths and bandwidth are dependent on its physical dimensions which are easily controllable by an antenna designer. Measured patterns of models with various radiation properties are shown to substantiate these design rules. A flat plateau-like main beam, low voltage standing-wave ratio (VSWR), the ability to produce both wide (60°) and narrow (30°) half-power beamwidths, low sidelobes and backlobe (40-50 dB down), low cross-polarized levels (20-25 dB down), and independent control of E- and H-plane beamwidths over an ultra-wide bandwidth, say 2-18 GHz, are some of the strong points of this antenna type     

A compact antenna for ultrawide-band applications

A novel compact and ultrawide-band (UWB) antenna is presented in this paper. The basis for achieving such an UWB operation is through proper magnetic coupling of two adjacent sectorial loop antennas in a symmetrical arrangement. A large number of coupled sectorial loop antennas (CSLA) with different geometrical parameters are fabricated and their measured responses are used to experimentally optimize the geometrical parameters of the antenna for achieving the maximum bandwidth. Through this optimization process an antenna with a VSWR of lower than 2.2 (S/sub 11/<-8.5 dB) across an 8.5:1 frequency range is designed. The maximum dimension of this antenna is smaller than 0.37/spl lambda//sub 0/ at the lowest frequency of operation and provides an excellent polarization purity. Furthermore, the antenna exhibits a relatively consistent radiation pattern. Modified versions of the CSLA are also designed to reduce the overall metallic surface and weight of the antenna while maintaining its wide-band characteristics. This allows modifying its dimensions to design low frequency light-weight UWB antennas.     

一种用于WSN的微小型UWB雷达天线设计

超宽带雷达不受雨、雪、声、风等自然环境的干扰,可用于无线传感器网络并全天候工作;在通信领域,超宽带雷达可避免多径干扰问题,解决无线传感器网络在复杂多径环境中的应用局限问题。故超宽带雷达可以与无线传感器网络形成天然的结合。为满足无线传感器网络低功耗、体积小的要求,设计了一种微小型超宽带雷达天线。该天线为共面波导方式馈电的贴片式微带天线。仿真结果表明,天线具有体积小、带宽广(1.78~2.38 GHz)、全向性好的优点,满足无线传感器网络应用需求,并可避免与已用无线通信频段的干扰,具有广阔的应用前景。     

A switched pattern radar antenna array

A procedure to design a switched pattern antenna array is developed and demonstrated on a 16- and eight-element array. The variable spacing of elements allows us to reduce the number of switchable elements to a minimum and to reduce the sidelobes of the effective pattern. Based on this design we have built and tested an eight-element prototype array. Measurements demonstrate the feasibility of the pattern switching concept for improved sidelobe performance.     

伪随机序列编码脉冲信号在探地雷达中的应用研究

超宽带编码雷达探测地下介质时,回波信号不可避免地受到噪声影响,这会对数据解释带来一定困难. 频率-波数（f-k）滤波方法可以有效滤除部分噪声,但其对高频段的滤波效果欠佳. 针对此问题,本文提出一种改进的f-k滤波方法,即根据频率和波数的分布情况,设置不同的视速度阈值进行分段处理,提高高频段的视速度阈值,有效滤除了高频段的噪声. 实验结果表明,经本文方法处理后的图像熵较传统方法处理后的图像熵减小了6%,具有良好的噪声抑制效果.

     

A novel array antenna for MSAT applications

The issue of reducing the cost of phased array vehicle antennas through the use of a lens feeding arrangement instead of phase shifters at each element is addressed. In particular, the economic viability of a mobile satellite system (MSAT) is largely dependent on the efficient use of the allocated scarce spectrum and orbit as well as the satellite power. The type of vehicle antenna used will play a critical role in achieving this efficiency. A standard design approach for an electronically steered array uses phase shifters at each element to provide beam steering. A method for reducing the required number of phase shifters by using an R-KR lens feed network is outlined. The authors briefly discuss the phase shifter approach to beam steering, examine various lens feed techniques, and describe the R-KR lens approach. The lens feed network architecture is examined, a computer model for simulation of the array is presented, and the results of analysis of a suggested design for the MSAT application are given. In addition, satellite acquisition and tracking considerations are investigated     

A low cost-low loss broadband integration of a CMOS transmitter and its antenna for mm-wave FMCW radar applications

A 60 GHz low-loss wideband interconnection of a CMOS transmitter and its antenna is presented in this paper. The integrated transmitter consists of an all-digital phase-locked loop (ADPLL) IC chip and a U-slot patch antenna connected through wire bonding and compensation matching circuit to operate in the 57–63 GHz frequency band. The system is implemented on a sandwiched printed circuit board (PCB) comprising FR4 to embed the ADPLL and the high-frequency Rogers laminate RO4350B for the antenna and the matching network. The matching circuit is designed in two configurations microstrip and grounded coplanar waveguide (GCPW) to compensate for the wire bond inductance. The capability and sensitivity of these two topologies considering the wire bond geometry variations are compared which points out that GCPW is more robust to wire bonding parasitic effects. Finally, the GCPW matching circuit is fabricated and interconnected to the ADPLL die and its performance is examined using hybrid simulation/measurement data.     

Optimization of the transmitter-receiver separation in the ground-penetrating radar

The finite-difference time-domain method is applied to simulate three-dimensional subsurface-scattering problems, involving a ground-penetrating radar (GPR) model consisting of two transmitters and a receiver. The receiving antenna is located in the middle of the two identical transmitters, which are fed 180/spl deg/ out of phase. This configuration implies the existence of a symmetry plane in the middle of two transmitters and the cancellation of the direct signals coupled from the transmitters at the receiver location. The antenna polarizations and their separations are arbitrary. The transmitter-receiver-transmitter configured GPR model is optimized in terms of the scattered energy observed at the receiver by varying the antenna separation. Many simulation results are used to demonstrate the effects of the antenna separation and the optimal separation encountered for a specific target and GPR scenario.     

A new quasi-Yagi antenna for planar active antenna arrays

In this paper, a novel broadband planar antenna based on the classic Yagi-Uda dipole antenna is presented, and its usefulness as an array antenna is explored. This “quasi-Yagi” antenna is realized on a high dielectric-constant substrate, and is completely compatible with microstrip circuitry and solid-state devices. This antenna achieves a measured 48% frequency bandwidth for voltage standing-wave ratio <2, better than a 12-dB front-to-back ratio, smaller than -15 dB cross polarization, and 3-5-dBi absolute gain. Mutual coupling of the antenna in an array environment is investigated. Finally, three simple arrays are presented, demonstrating the usefulness of the antenna as an array element. This novel antenna should find wide application in wireless communication systems, power combining, phased arrays, and active arrays, as well as millimeter-wave imaging arrays     

A dielectric bifocal lens for multibeam antenna applications

An iteration technique is applied to the design of a bifocal dielectric lens antenna. A bifocal lens has two conjugate off-axis focal points and offers good off-axis scanning performance. A computer model was developed to aid in the design analysis and far-field performance evaluation of a bifocal lens. The computer simulation results demonstrate that the bifocal dielectric lens can provide a higher-gain radiation pattern for multibeam antenna (MBA) applications over a large field-of-view. The computer study also indicates that the quadratic phase error can be significantly reduced by constraining the feed along an optimized focal arc     

A miniaturized metamaterial slot antenna for wireless applications

A novel miniaturized five band metamaterial inspired slot antenna is reported. The proposed design consists of a ring monopole and metamaterial Rectangular Complementary Split Ring Resonator (RCSRR) as the radiating part, two L and one T–shaped slot as the ground plane, respectively. Miniaturization in the proposed design is accomplished by metamaterial RCSRR, and also, it helps the antenna to operate at 2.9 and 5.2 GHz frequency bands. The aforementioned miniaturization process leads to about 46.8% reduction in volume of the proposed design, as compared to the conventional antenna. The pass band characteristics of the metamaterial RCSRR through waveguide medium are discussed in detail. In order to enhance the operating abilities of the miniaturized antenna, slots are etched out in the ground plane, thereby making the miniaturized antenna further operate at 2.4, 5.6 and 8.8 GHz, respectively. The proposed design has an active patch area of only , with dB bandwidth of about 4.16% (2.35–2.45 GHz), 5.71% (2.63–2.76 GHz), 10.25% (4.44–4.92 GHz), 6.25% (5.42–5.77 GHz) and 2.39% (8.68–8.89 GHz) in simulation, and about 6.86% (2.25–2.41 GHz), 5.01% (2.55–2.7 GHz), 9.16% (4.58–5.02 GHz), 5.38% (5.79–6.11 GHz) and 5.42% (8.44–8.91 GHz) in measurement. The antenna has good impedance matching, acceptable gain and stable radiation characteristics across the operational bandwidths.     

A Chaucer microstrip fractal antenna for mobile applications

In this paper a Chaucer fractal patch antenna integrated with split ring structure is simulated using Ansoft’s (HFSS), as well as fabricated and tested using VNA. The obtained results indicate that the proposed antenna resonates at 2.4 GHz in the ISM band. In addition, the structure offers multi-band operation with the fair value of return loss, gain, and bandwidth, impedance and directivity in the entire range of frequency operation.