4-element planar array antenna for UWB application

A novel low-cost 4-element planar array antenna directly fed by a coaxial cable for Ultra-WideBand(UWB) application is presented. The proposed antenna consists of 2×2 bowtie elements and a simple 1:4 power divider feeding network. Compared to the basic bowtie element, the impedance bandwidth of the array antenna has a significant improvement that the low cut-off frequency is extended from 6 GHz of the bowtie element to 2 GHz. The measured results show that the proposed antenna has a large bandwidth of 2 GHz to 11 GHz for Voltage Standing Wave Ratio(VSWR)2, and exhibits a bidirectional radiation pattern and a modest gain across the operating band and a peak gain of about 9 dBi at 11 GHz.     

基于TDC的无死区频率测量技术研究

在精密时频测控领域中,高分辨率、无死区的时间间隔和频率测量非常关键,而时间数字转换器(Timeto Digital Converter,TDC)是时间频率测量的常用手段.该文研制了基于ACAM公司生产的时间数字转换芯片TDC-GP21和Altera公司FPGA芯片EP4CE6E22C8N的时间频率测量设备,实现了高分辨...     

一种通用的时间数字转换器码密度校准信号产生方法及其实现

该文提出一种通用的时间数字转换器(TDC)码密度校准信号产生方法,该方法基于相干采样理论,通过合理设置TDC主时钟和校准信号之间的频率差,结合输出信号保持电路,产生校准用的随机信号,在码密度校准过程中,随机信号均匀分布在TDC的延时路径上,实现对TDC的bin-by-bin校准。基于Xilinx公司的28 nm工艺的Kintex-7 现场可编程门阵列(FPGA)内部的进位链实现一种plain TDC,利用该方法校准plain TDC的码宽(抽头延迟时间),研究校准了2抽头方式下的TDC的性能参数,时间分辨率(对应TDC的最低有效位,Least Significant Bit, LSB)为24.9 ps,微分非线性为(–0.84～3.1)LSB,积分非线性为(–5.0～2.2)LSB。文中所述的校准方法采用时钟逻辑资源实现,多次测试考核结果表明,单个延时单元的标准差优于0.5 ps。该校准方法采用时钟逻辑资源代替组合逻辑资源,重复性、稳定性较好,实现了对plain TDC的高精度自动校准。该方法同样适用于其他类型的TDC的码密度校准。     

Design of CPW-fed asymmetric slot UWB antenna for wireless application

A compact Ultra-WideBand(UWB) slot antenna is presented in this paper. The slot is modified rectangular in shape and asymmetrically cut in the ground plane. A hexagonal patch with two stepped CoPlanar Waveguide(CPW) feed is used to excite the slot. Wider impedance bandwidth is achieved due to the extra inductive reactance created by the asymmetric slot which neutralizes the capacitive reactance of the hexagonal patch. The measured impedance bandwidth of the proposed antenna is 11.85 GHz(2.9–14.75 GHz). The radiation patterns of the proposed antenna are obtained and found to be omni-directional in H-plane and bi-directional in E-plane.     

基于压缩感知的超宽带信道估计方法的研究

压缩感知(Compressed Sensing, CS)理论可以从较少的观测样本中恢复稀疏信号。针对超宽带(Ultra- WideBand, UWB)信道的稀疏特性,将压缩感知理论应用于UWB系统的信道估计中,能够有效地降低系统的采样速率。该文针对UWB信道的特点对过完备字典库和观测矩阵进行设计,提出了一种滤波矩阵估计算法。然后,分别利用丹茨格选择器(Dantzig Selector, DS),基追踪降噪(Basis Pursuit De-Noising, BPDN)算法和正交匹配跟踪(Orthogonal Matching Pursuit, OMP)算法实现信号检测,进一步给出UWB信道估计中CS重建算法的选择建议。基于IEEE 802.15.4a信道模型的仿真结果表明,该算法同随机观测算法的检测结果相比,能够在较低的采样速率下获得更好的误码率性能。     

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.     

基于频带分割的超宽带雷达脉冲压缩方法

本文研究了基于频带分与多通道综合的超宽带雷达脉冲压缩方法,并对该方法进行了性能分析。     

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。     

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...     

UWB的调制技术及其应用前景

UWB(超宽带)技术是继CDMA技术之后迅速发展的一种宽带传输技术,将经过信息调制的基带脉冲进行直接发送,脉冲宽度一般为ns级,因此它的信号能量分布在从DC到几GHz范围。它相对常规窄带传输方式而言有低功率谱、低截获、抗干扰能力强、可高速数据传输、多径分辨能力强和共享频谱等优点。主要介绍了UWB的几种调制技术,包括:TH-PPM、DS-UWB、TH-PAM和TH-OOK。分别阐述了它们的信号调制与解调,并分析比较了它们的性能,得出TH-PPM功率效率最高,是一种最优方案,最后以一种简明方式分析了UWB的应用和未来发展前景。     

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.     

一种用于UWB系统的高斯脉冲发生器

提出了一种新型的用于超宽带系统的高斯脉冲发生器.该脉冲发生器采用阶跃恢复二极管,结构简单,且易于实现.电路中加入一个放大器,以便阻止反射波对阶跃恢复二极管的影响,较好地抑制了脉冲尾部的波动,并使用共面波导实现.该极窄高斯脉冲的脉宽仅为300ps,且有很好的对称性.     

窄带干扰抑制的一种新型频率编码正交UWB脉冲设计

文中提出一种基于正交载波和伪随机序列的新型频谱编码正交UWB脉冲设计方法，该方法是在频域中利用PN序列对经过频移的子脉冲进行编码来产生正交脉冲．在IR-UWB（脉冲无线电超宽带）中引入了正交载波和PN序列，使其不仅具有传统IR—UWB和多频带CB-UWB（基于载波的超宽带）优点，而且提高了UWB信号发射的瞬时频谱和瞬时能量的效率．脉冲的自相关和互相关特性皆优于传统的脉冲。另外，借助于认知无线电技术，可保证发送信号满足FCC的UWB频谱规划，避免与其他传统窄带系统干扰。仿真结果表明该脉冲设计方法能够有效的抑制窄带干扰，并降低复杂度。     

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.     

UWB通信信号选择与系统性能仿真

本文通过对具有相同能量和相同脉宽的不同 UWB( Ultra Wide Band)脉冲信号在脉位调制 ( PPM,Pulse Position Modulation)和脉幅调制 ( PAM,Pulse Amplitude Modulation)方式下的抗噪声性能的理论分析与仿真对比 ,研究了在 AWGN( Additive White Gaussian Noise,加性高斯白噪声 )条件下 ,不同调制方式下脉冲波形的选择与系统性能之间的关系     

一种适应复杂地下环境的导航增强型脉冲超宽带通导一体自组网体制设计研究

超宽带(UWB)技术以其大宽带、低功率、高精度等优点广泛应用于室内定位。然而其本质上是一种通信信号体制,复杂环境下组网困难,所以UWB系统在复杂地下环境中仍有挑战。为此该文在UWB标准信号体制的基础上提出了导航增强型超宽带(Hnav-UWB),通过优化通信信息的冗余度简化帧结构,同时降低脉冲发送频率增加单个脉冲的能量,采用改进的跳时二进制相移键控(TH-BPSK)调制方式提高了信号的多用户和抗多径能力。另外,该文设计了动态重构节点网络适应复杂环境,该网络没有主从节点之分,通过双向测距获得两两距离,根据多维尺度变换(MDS)算法自建相对位置坐标,根据分布式协作定位(DCL)算法提高精度,最后根据最小二乘(LS)法利用某已知点在地图的位置进行地图匹配。基于自建的脉冲超宽带(IR-UWB)仿真系统试验,结果显示相同条件下Hnav-UWB的误码率比对照组降低10倍,定位精度提升3倍。经1000次蒙特卡罗模拟,动态重构网络匹配准确率达95%。     

满足FCC辐射掩模的UWB信号设计算法及性能分析

脉冲波形设计是超宽带无线通信技术研究中的重要内容。以满足联邦通信委员会(FCC)辐射掩模为前提,采用两次迭代的算法逐步对脉冲波形参数进行优化,设计了一种低复杂度、能够最大限度提高UWB系统的辐射功率的UWB信号。同时,研究了经过加性高斯白噪声(AWGN)信道,在跳时扩频脉位调制(TH-PPM)UWB系统中使用该窄脉冲的系统性能。仿真结果表明,该UWB通信系统比通常使用Manchester窄脉冲或Scholtz窄脉冲的UWB系统误码性能更优。这对于UWB系统的实际运用有很好的指导意义。     

Fast symbol-level synchronization for TR-UWB signals using double hybrid DS-TH spreading

A Transmitted Reference （TR） Ultra WideBand （UWB） signal with double hybrid Direct Sequence and Time Hopping （DS-TH） spreading is proposed and its symbol-level synchronization scheme is designed and analyzed. The proposed signaling format can significantly reduce the search space while reducing the spectral lines and eliminating inter-frame interference and multi-user inter- ference. Detailed analysis of the proposed scheme is carried out. Synchronization performance of the proposed signaling format in multipath channel is derived and supported by computer simulation. The search step which is closely associated with the delay of data modulated pulses is analyzed. Using the TH code, the proposed signaling format and synchronization scheme especially works well in moderate and low data rate systems.     

应用于CMOS图像传感器的高速全差分两步式ADC设计方法

由于传统的单斜式模数转换器(SS ADC)以及改进的各种架构串行两步式SS ADC普遍存在速度瓶颈问题,均无法满足工业界高帧率CMOS图像传感器的发展需求,该文提出一种应用于高帧率CMOS图像传感器的高速全差分两步式ADC设计方法。该ADC设计方法基于差动斜坡与时间数字转换(TDC)技术,将差动量化嵌套在两步式的量化中,形成了区别于串行量化的并行量化模式,不仅提升了数据量化的速率,而且保证了系统的一致性和鲁棒性;针对传统TDC技术与单斜式ADC的匹配性问题,提出了一种基于电平编码的TDC技术,在ADC量化的最后一个时钟周期内,在不提升系统时钟的情况下,完成时间数字转换,实现了更高精度的量化。该文基于55 nm 1P4M CMOS实验平台完成了所提方法的电路设计、版图设计和测试验证。在模拟电压3.3 V、数字电压1.2 V、时钟频率100 MHz、动态输入范围1.6 V的设计环境下,该文ADC设计精度为12 bit,转换时间仅有480 ns,列级功耗低至62 μW,DNL以最低有效位(LSB)计为+0.6/–0.6,INL以最低有效位(LSB)计为+1.2/–1.4,信噪失真比(SNDR)达到70.08 dB,与现有的先进单斜式ADC相比,ADC转换速度提高了52%以上,可以有效压缩行处理时间,为高帧率大面阵CMOS图像传感器的实现提供了有效的解决方案。     

基于高斯二阶导数组合的UWB脉冲波形设计

提出了一种基于高斯二阶导数组合的UWB脉冲波形设计方法.依据FCC对超宽带各频段带宽划分的不同及各频段辐射限制的差异来选取基函数,利用最小均方误差准则(LSE),以FCC室内辐射掩蔽为规范选取一组加权系数对基函数进行线性组合.再通过调整基函数参数脉冲形成因子和搬移因子,对波形进一步优化.仿真结果表明,文中设计脉冲实现了在全频段对辐射掩蔽的高效逼近,与基于随机系数选择的组合脉冲比较:方法简单,具有更高的频谱利用率.