A NEW DESIGN METHODOLOGY FOR PRINTED LOG-PERIODIC MONOPOLE ANTENNA

In theory,Log-Periodic Antenna (LPA) is a linearly polarized antenna with frequency independent properties on the input impedance and gain patterns.Owing to these characteristics,LPA has gained researc...     

UWB TEM HORN ANTENNA FOR THE ASPHALT PAVEMENT INVESTIGATION简

A simple Ultra-WideBand （UWB） exponentially-tapered Transverse ElectroMagnetic （TEM） horn antenna is presented for the asphalt detection based on Ground Penetrating Radar （GPR） In order to reduce the reflections from the antenna aperture, some absorbing material is loaded on the outer surface of the conductor. Comparing with the traditional TEM horn antenna, the proposed antenna has a small size and a large impedance bandwidth. Simulated and measured results show that the proposed TEM horn antenna has a low Voltage Standing Wave Ratio （VSWR） below 2 over the whole band from 0.35 GHz to 12 GHz, good radiation characteristics, and small late-time ringing, which can perfectly meet the requirements of the GPR application.     

Truly balanced pulse generator using microwave transistor and SRD

A novel efficient circuit for Ultra-WideBand (UWB) balanced sub-nanosecond monocycle pulse generation is presented. The pulse generator employs wideband bipolar transistor, step recovery diodes, Schottky diodes, and simple charging and discharging circuitry. Simple transient analysis and design of the circuit are presented along with their operating principle. The pulse generator produces truly balanced monocycle pulse with 500 ps pulse-width and 800 mV peak voltage. The generated monocycle pulse also has very symmetrical positive and negative portions and low ringing level. The presented pulse generator can be used as both a transmitter feeding UWB balanced antennas without broadband baluns and a balanced switching pulse generator that used in UWB receiver.     

A high performance UWB LFM waveform generator

In this paper, the design and implementation of a high performance Ultra-WideBand （UWB） Linear Frequency Modulation （LFM） waveform generator at Very High Frequency/Ultra High Frequency （VHF/UHF） band are introduced. Firstly, the design ideas for a high performance UWB LFM waveform generator are described. Then, a generation scheme for UWB LFM waveforms is presented according to the baseband digital generation method combining with the bandwidth extension method via frequency doubling. An experimental system has been implemented and tested. The results show that the UWB LFM waveform generator achieves very high performance.     

P N IFFT FOR OFDM-BASED UWB SYSTEM

In this letter, P × N-point IFFT is proposed to replace the N-point IFFT and analog frequency conversion in an Orthogonal Frequency Division Multiplexing (OFDM)-based Ultra-WideBand (UWB) system, and a new algorithm, named fast P × N-point IFFT, is designed to reduce the complexity of the P × N-point IFFT in the proposed scheme.     

The TR-UWB receiver based on spatial diversity

This paper presents a new Transmitted Reference (TR) Ultra-WideBand (UWB) receiver based on Spatial Diversity (SD), which employs Multi-Antenna Technology (MAT) to improve the performance of TR-UWB receiver. According to the amplitude of correlator output of every antenna branch, this paper analyzed the performances of the proposed TR-UWB receiver employing three different kinds of combina-tion strategies, i.e., Maximum Ratio Combination (MRC), Equal Gain Combination (EGC), and Selective Combination (SC), which are different from conventional ones, and theoretically proved that the performance of EGC is better than MRC. Simulation results verify that when EGC is adopted and BER=10–3, increasing three antennas provides Signal to Noise Ratio (SNR) gain of about 3 dB in CM4 channel and SNR gain of about 2 dB in CM2 channel.     

超宽带通信中模拟空时码的一种子空间检测方法

该文针对应用于超宽带(UWB)通信中的模拟空时码, 提出了一种基于子空间的盲检测方法。在接收端不需要估计信道,利用信号子空间和噪声子空间正交的性质,建立了一个二次型,最小化该二次型就可得到发送信号的估计。平坦衰落信道环境中的仿真表明,子空间方法能够实现和相关接收相同的分集增益;当多个连续的空时码联合解码时,其性能优于现有的非相关解码方法。     

A throughput-efficient adaptive transmit-receive scheme for indoor DS-UWB systems

In this paper, a novel adaptive transmit-receive scheme is presented for indoor Direct Sequence Ultra-WideBand （DS-UWB） systems. In the proposed scheme, a simple switch module is introduced to improve the system throughput. Furthermore, adaptive detection is implemented via an improved Least Mean Squares （LMS） algorithm. The convergence behavior and the Bit Error Rate （BER） performance of the proposed scheme are examined under the realistic channel models. Simulation results show that, nearly without loss of the BER performance, the proposed scheme can obtain at least 2/3 improvement in training overhead compared with the conventional approach.     

一种新的自适应窄带干扰抑制在直扩超宽带系统中的应用

基于目标函数的最优化问题与求解线性方程组的等价性,该文针对直扩超宽带(DS-UWB)系统提出了一种新的自适应窄带干扰抑制方案。该方案把最优化模型转化为线性方程组的形式,并用一种有效的迭代方法即共轭梯度(Conjugate Gradient, CG)算法来实现自适应滤波。理论分析及计算机仿真结果表明,与现有的窄带干扰抑制方案相比,该文提出的方案具有更高的性价比,因此在低功耗、低成本及简易实用的室内超宽带应用场合,适合作为一种可选的折衷方案。     

Low profile meander line Printed Quadrifilar Helix Antenna

In this paper, a new approach of meander line technique for Printed Quadrifilar Helix Antenna (PQHA) is studied. Compared with other meander line techniques, this approach has lowered the axial height of antenna greatly and improved the efficiency of model-building in simulation proc-essing. We have focused on the analysis of radiation pattern, axial ratio, and design graph for the Meander line Printed Quadrifilar Helix Antenna (MPQHA). Finally, we have reduced successfully 67% size in geometry compared with traditional PQHA method, and obtained rather reasonable results.     

一种新颖的宽带圆极化单极天线

该文设计了一种新颖的宽带圆极化单极子天线,该天线采用微带馈电模式。天线由C型贴片和改进的地板组成,整个天线尺寸仅为25×25×1 mm³。通过在C型贴片上切角和在地板上增加三角形微扰结构,可以有效增加天线的阻抗带宽和轴比带宽。该文给出了天线的设计流程,从表面电流分布分析了圆极化天线的工作机理。加工了天线实物,并对其进行了测量。仿真和实测结果表明天线具有超宽的阻抗带宽和轴比带宽。天线的工作频带为4.35～12 GHz(相对带宽为93.6%),3 dB轴比带宽为4.15～11.8 GHz(相对带宽为95.9%)。测量了天线的辐射性能和增益特性,实测结果与仿真结果吻合较好,证明了该天线的有效性。该天线可以应用于超宽带无线通信系统和卫星通信系统中。     

Effect of multipath channel models to the recovery algorithms on compressed sensing in UWB channel estimation

Multipath arrivals in an Ultra-WideBand (UWB) channel have a long time intervals between clusters and rays where the signal takes on zero or negligible values. It is precisely the signal sparsity of the impulse response of the UWB channel that is exploited in this work aiming at UWB channel estimation based on Compressed Sensing (CS). However, these multipath arrivals mainly depend on the channel environments that generate different sparse levels (low-sparse or high-sparse) of the UWB channels. According to this basis, we have analyzed the two most basic recovery algorithms, one based on linear programming Basis Pursuit (BP), another using greedy method Orthogonal Matching Pursuit (OMP), and chosen the best recovery algorithm which are suitable to the sparse level for each type of channel environment. Besides, the results of this work is an open topic for further research aimed at creating a optimal algorithm specially for application of CS based UWB systems.     

A new modulation scheme for IR-UWB communication systems

Since the poor performance of orthogonal binary Pulse Position Modulation (PPM) compared with binary Pulse Amplitude Modulation (PAM), this paper presents a new modulation scheme named Pulse Width Modulation (PWM) for Impulse Radio Ultra-WideBand (IR-UWB) communication systems. This modulation scheme uses pulses with equal amplitude and different widths to carry different information. The receiver employs differences between similarity coefficients among these pulses to distinguish different information. Bo...     

On the performance of analog multiuser detection in ultra-wideband transmitted-reference system

The detection performance is evaluated for our proposed analog multiuser receiver in Ul-tra-WideBand (UWB) transmitted-reference system. In the presence of dense multipath and multi-access signals, the performance analysis is difficult due to the complicated waveform of received impulse. We de-velop an approach to analyze the steady-state Signal-to-Interference-plus-Noise (SINR) of the detector out-put. The multipath-spread impulse is fitted to an exponentially decaying profile in the analysis. A closed-form expression of steady-state SINR is further deduced for the proposed Least Minimum Square (LMS) detector. The analysis is validated by simulations in Line-Of-Sight (LOS) and Non-Line-Of-Sight (NLOS) channel re-spectively. Based on the theoretical results, the multipath delay spread is employed to determine the optimal width of the integration window of the detector.     

穿透叶簇UWB雷达人造目标简化电磁模型

穿透叶簇的VHF／UHF超宽带(UWB)SAR具有相对带宽很宽,积累角大的特点,可同时获得距离、方位的高分辨能力,能用于探测叶簇隐蔽的军用车辆等人造目标而有着重要的军事应用价值。在VHF／UHF低频段,一般的人造目标可简单模化为目标主侧面与地表面之间形成的直二面角。本文详细推导了二面角人造目标光学区的散射场,建立了低频UWB雷达人造目标的光学区简化电磁模型,进而分析预测了二面角目标的散射特性。预测结果与外场试验分析得到的目标特性之间的一致性表明本文所建立的电磁模型是正确合理的。     

UWB SAR RFI suppression based on region of support in 2-D wavenumber domain

Radio Frequency Interference （RFI） degrades the quality of focused Ultra-WideBand Synthetic Aperture Radar （UWB SAR） images. From both the theoretical analysis and real data validation, it is concluded that target echo and RFI have different Region Of Support （ROS） in 2-D fasttime wavenumber and aperture wavenumber domain. Consequently, a novel adaptive filter is proposed according to the Wiener optimum criterion on the distinct ROS characteristics of target echo and RFI. Compared with the notch filter and the Least Mean Square （LMS） adaptive filter in previ- ous literatures, the proposed method is more computationally efficient with satisfactory suppression results. In terms of Signal-to-Interference Ratio Improvement （SIRI） and processing time, the performance of the proposed adaptive filter is verified with the field data collected with a UWB SAR system.     

A novel Ultra WideBand monopole antenna with band-notched characteristics

A simple and compact microstrip-fed Ultra WideBand(UWB) printed monopole antenna with band-notched characteristic is proposed in this paper.The antenna is composed of a square ring with a small strip bar,so that the antenna occupies about 7.69 GHz bandwidth covering 3.11～10.8 GHz with expected band rejection from 5.12 GHz to 5.87 GHz.A quasi-omnidirectional and quasi-sym-metrical radiation pattern is also obtained.This kind of band-notched UWB antenna requires no ex-ternal filters and thus greatly simplifie...     

A compact dual band-notched UWB circular monopole antenna with parasitic resonators

A compact dual band-notched Ultra-wideband (UWB) circular monopole antenna that has two parasitic resonators in the ground plane is presented in this paper. The Inverted–U and Iron shaped parasitic resonators are located on the back side of the radiating patch to achieve the band rejection characteristics from 5 to 5.4 GHz for WLAN and 7.8 to 8.4 GHz for ITU band respectively. By cutting a rectangular slot on the ground plane, additional resonance is excited at the higher frequency band, and hence much wider impedance bandwidth can be attained. Applications of the proposed dual band-notched ultra-wideband (UWB) antenna structure with 5.2 GHz and 8.2 GHz center frequencies are demonstrated experimentally. Measured and simulated results of the magnitude of S₁₁, radiation patterns and realized gains show good agreement.