Design of Ultrawideband Planar Monopole Antennas of Circular and Elliptical Shape

An efficient approach is described for designing ultrawideband (UWB) antennas in the form of planar monopoles of elliptical and circular shape. To avoid the time consuming trial-and-error approach presented in other works, simple design formulas for this type of radiators are described and their validity is tested via electromagnetic analysis and measurements. Full electromagnetic wave investigations are performed assuming three types of substrates with wide range of dielectric constant and thickness. The presented results show that the proposed method can be applied directly to design planar antennas that cover the ultrawide frequency band from 3.1 GHz to more than 10.6 GHz. Four types of monopole antennas were manufactured using RT6010LM substrate and their operation was tested in terms of return loss, radiation pattern characteristics, gain, and time domain response. The developed antennas feature UWB behavior with near omnidirectional characteristics and good radiation efficiency. The time domain transmission tests between two identical elements show that the manufactured circular monopoles offer better performance in terms of distortionless pulse transmission than their elliptically shaped counter parts. These antennas are also assessed in terms of fidelity factor. The manufactured antennas show a high fidelity factor which is more than 90% for the face-to-face orientation.     

集成鳍线为脊的新型圆锥及方锥TEM喇叭及其在目标瞬态特性中的应用

发明了一种共面波导到鳍线的宽带过渡结,采用该结构方式馈电,研制了一种新型超宽带集成鳍线辐射器,把此种鳍线作为圆锥ＴＥＭ喇叭或者方锥ＴＥＭ喇叭的脊,成为超宽带鳍线加脊的ＴＥＭ喇叭,该种喇叭及其脊的形式均为国内外首创。     

A New Type of Ultra-Wide Band Conical Antenna Ridged with a Novel Finline Radiator

A new type of ultra-wide band(UWB) conical antennas ridged by a novel taper finline radiator(TFR) used as radiation and receiving of the short pulse are developed. In which, a new UWB feed structure of a coplanar waveguide to finline and a TFR ridge are used initially. The experiment results show the characteristics of high fidelity, high efficiency, and high gain compared with some common broad-band antennas such as the biconical antennas, V-conical antennas, logarithm periodic antennas, and the other TEM horns.     

新型集成超宽带开槽天线的研制及其应用

研制出一种用于超宽带短脉宽射和接收的新型集成超宽带槽天线，该天线采用共面波导到槽线的宽带过渡方式馈电，实验结果显示了其高保真的宽带特性及高增益高效益特性。利用所研制的ＵＷＢ天线建立起超宽超带雷达实验系统，测量几种简单目标特性及涂层目标特性，证明了该种天线可用作实际的ＵＷＢＲ天线。     

On the performance of using multiple transmit and receive antennas in pulse-based ultrawideband systems

This paper presents an analytical expression for the signal-to-noise ratio (SNR) of the pulse position modulated (PPM) signal in an ultrawideband (UWB) channel with multiple transmit and receive antennas. A generalized fading channel model that can capture the cluster property and the highly dense multipath effect of the UWB channel is considered. Through simulations, it is demonstrated that the derived analytical model can accurately estimate the mean and variance properties of the pulse-based UWB signals in a frequency-selective fading channel. Furthermore, the authors investigate to what extent the performance of the PPM-based UWB system can be further enhanced by exploiting the advantage of multiple transmit antennas or receive antennas. Numerical results show that using multiple transmit antennas in the UWB channel can improve the system performance in the manner of reducing signal variations. However, because of already possessing rich diversity inherently in the UWB channel, using multiple transmit antennas does not provide diversity gain in the strict sense [i.e., improving the slope of bit error rate (BER) versus SNR] but can possibly reduce the required fingers of the RAKE receiver for the UWB channel. Furthermore, because multiple receive antennas can provide higher antenna array combining gain, the multiple receive antennas technique can be used to improve the coverage performance for the UWB system, which is crucial for a UWB system due to the low transmission power operation.     

Ultrawideband Circularly Polarized Spiral Antenna Using Integrated Balun With Application to Time-Domain Target Detection

The design of a wideband circularly polarized (CP) equiangular spiral antenna is described. Contrary to the conventional spiral antenna using the coaxial line or the vertically connected feeding structure, a tapered microstrip balun is fully integrated into one spiral arm of the proposed antenna and hence this construction can be realized completely planar. The measured results show that the return loss is better than 10 dB from 3.75 to 18.6 GHz, the axial ratio is below 3 dB from 3 to 14.5 GHz, the radiation is bidirectional with opposite polarization, and the antenna peak gain is 3.5 to 7 dBic. The time-domain characteristic of the transmitting/receiving system using the proposed ultrawideband (UWB) CP antennas is investigated by transient response. The pulse distortion is insignificant and is verified by the measured antenna performance with high signal fidelity ($geq 0.89$) and low variation of group delay ($leq 0.1~{rm ns}$ ). The transmitting/receiving antenna system using the proposed antennas is constructed to demonstrate the CP characterization and to detect the target position.      

用于超短脉冲辐射和接收的新型平面集成天线辐射元

研制出一种用于超宽带短脉冲辐射和接收的新型平面集成超宽带（UWB）天线辐射元，该天线辐射元采用共面波导到槽线的宽带过滤方式馈电，超短脉冲辐射和接收的实验结果显示了其高保真宽带及高增益、高效率的特性。     

超宽带脉冲天线的补偿技术研究

针对超宽带通信系统中脉冲信号传输保真度的问题, 分析了保真度与脉冲天线的相频特性、增益-频率特性的关系, 提出通过调整天线的增益特性来对信号在自由空间产生的传输损耗进行平衡补偿的技术.通过对一款高保真印刷半锥形单极天线(Half-Printed Tapered Monopole Antenna, Half-PTMA)增益-频率特性的仿真分析, 以及将此补偿技术应用到一款超宽带平面单极天线的设计改进, 改进后保真度提高了5%, 验证了文中补偿技术的有效性, 为超宽带脉冲天线的高保真设计提供了有价值的设计依据.     

A compact CPW fed slot antenna for ultra wide band applications

A printed compact coplanar waveguide fed triangular slot antenna for ultra wide band (UWB) communication systems is presented. The antenna comprises of a triangular slot loaded ground plane with a T shaped strip radiator to enhance the bandwidth and radiation. This compact antenna has a dimension of 26 mm × 26 mm when printed on a substrate of dielectric constant 4.4 and thickness 1.6 mm. Design equations are implemented and validated for different substrates. The pulse distortion is insignificant and is verified by the measured antenna performance with high signal fidelity and virtually steady group delay. The simulation and experiment reveal that the proposed antenna exhibits good impedance match, stable radiation patterns and constant gain and group delay over the entire operating band.     

频率可重构超宽带天线研究

超宽带天线和可重构天线是当今天线领域研究的热点。将可重构天线技术应用到超宽带天线设计中,讨论了频率可重构超宽带天线的设计思路。以印刷单极子椭圆天线为原型,给出了两个可重构天线的具体结构,并对天线进行了可重构带阻设计,避免与相关频段之间的干扰。仿真结果表明:重构后天线Ⅱ的低频获得了扩展,其相对尺寸的长和宽分别减小到最大工作波长的0.116倍和0.087倍,工作频段为0.174～10.9GHz,可重构阻带为5.1～5.95GHz,带宽比可高达62:1.     

Methods for Ultra-Wideband Pulse Generation Based on Optical Cross-Polarization Modulation

Optical methods for different type ultra-wideband (UWB) pulse generation based on cross-polarization modulation (CPM) are proposed and demonstrated in this paper. Two polarity-reverse pulses can be obtained by CPM and birefringence time delay to form a monocycle pulse. A semiconductor optical amplifier (SOA) is placed after the monocycle pulse process for doublet pulse generation. These two kinds of pulses can be employed in single-band impulse radio UWB (IR-UWB) systems. Two kinds of multi-band UWB pulses can be generated based on monocycle pulse train with proper apodization profiles, realized by hybrid photonic microwave filter and synchronous polarization modulation respectively. Experimental results show that these pulses can be used in multi-band UWB (MB-UWB) over fiber systems.      

A study of pulse radiation from several broad-band loaded monopoles

Five previously proposed designs for broad-band monopole antennas are evaluated for pulse radiation. These designs use continuous resistive loading and/or discrete capacitive loading to increase the bandwidth over that of a simple, metallic monopole. The parameters for each of the designs are scaled so that the designs can be compared on a common basis (frequency range). Each of the antennas is analyzed numerically, and quantities characteristic of their pulsed performance are computed. These quantities include the reflected voltage in the feeding transmission line, radiated electric field, radiating efficiency, time-domain gain, fidelity, and symmetry when the monopoles are excited by a differentiated Gaussian pulse. In addition, the input reflection coefficient and gain at broadside for monochromatic excitation are shown. Explanations are provided for the differences in performance for these designs     

Group Delay Equalized UWB InGaP/GaAs HBT MMIC Amplifier Using Negative Group Delay Circuits

A negative group delay (NGD) circuit has been employed to equalize a group delay variation in a broadband ultra-wideband (UWB) InGaP/GaAs heterojunction bipolar transistor (HBT) monolithic microwave integrated circuit (MMIC) amplifier. Using the NGD circuit, a part of a salient group delay characteristic in the operation band of broadband amplifiers can be suppressed without an increase of the entire group delay. The MMIC amplifier has a steep group delay increase in the lower frequency region of the full-band UWB band (3.1-10.6 GHz) due to the sum of phase variations near the cutoff frequencies of the HBTs. The NGD circuit has been inserted to reduce this increase of the group delay in the UWB band. By adding a three-cell NGD circuit while considering input and output matching at the input side of the MMIC amplifier, the group delay variation is decreased by 78%. However, gain was also decreased by insertion of the multistage NGD circuit. In an attempt to avoid this decrease in gain, a one-cell NGD circuit was inserted into the feedback loop of the MMIC amplifier, and as a result, we were able to decrease the group delay variation by 79%, with minimal gain deterioration.     

基于空间分集的TH-UWB系统性能分析

为了提高UWB系统在低信噪比下的性能,利用IEEE 802.15.3a工作组建议的标准UWB室内信道模型,采用多个接收天线分析了二进制TH-PPM超宽带系统性能的改善。在理想功率控制下,分别采用不同数目的接收天线和不同SRake接收机选择路径数,对2PPM-TH-UWB系统性能进行了分析和仿真。仿真结果表明,随着天线数和选择路径数的增加,系统性能均明显提高,并且空间分集比路径分集对系统性能有更好的改善。     

Comparison of planar dipoles in UWB applications

The characteristics of four planar dipoles are studied and compared based on the design considerations of ultrawide-band (UWB) antennas. Their impedance matching, realized gain, and polarization over the UWB band are investigated. The current distributions on the dipoles are illustrated to interpret their different radiation characteristics. Furthermore, pulses radiated in different directions are presented for both single-band and multiband schemes in UWB applications.     

Path-loss and time dispersion parameters for indoor UWB propagation

The propagation of ultra wideband (UWB) signals in indoor environments is an important issue with significant impacts on the future direction and scope of the UWB technology and its applications. The objective of this work is to obtain a better assessment of the potentials of UWB indoor communications by characterizing the UWB indoor communication channels. Channel characterization refers to extracting the channel parameters from measured data. An indoor UWB measurement campaign is undertaken. Time-domain indoor propagation measurements using pulses with less than 100 ps width are carried out. Typical indoor scenarios, including line-of-sight (LOS), non-line-of-sight (NLOS), room-to-room, within-the-room, and hallways, are considered. Results for indoor propagation measurements are presented for local power delay profiles (local PDP) and small-scale averaged power delay profiles (SSA-PDP). Site-specific trends and general observations are discussed. The results for path-loss exponent and time dispersion parameters are presented.     

超宽带时域近距离高分辨ISAR成像

近距离目标超高分辨率微波成像技术在安全检测、非破坏性控制、生物医学等领域中有着非常重要的应用价值和广阔的应用前景。该文利用基于窄脉冲形式的超宽带时域雷达系统研究近距离目标的高分辨率ISAR成像,给出了仿真和实测结果。利用转台旋转目标,基于超宽带脉冲源和超宽带收发天线以及高性能取样示波器,配以同步触发脉冲和自行研发的数据采集软件,搭建了该时域雷达实验系统,提出了准确获取目标回波信息的实验条件,和实现回波延时精确校正的误差补偿方法。并针对采样时间窗内的杂波干扰,讨论了时域后向投影算法(Back Projection,BP)与背景对消技术相结合的成像算法,实现了分辨率为8 mm的近距离目标的成像,准确地反映了目标的位置、形状和大小等信息。     

UWB系统中天线性能对脉冲波形的影响

分析了超宽带无线系统中,天线在发射和接收过程中对基带脉冲信号波形的失真影响.采用了天线系统传递函数描述天线的辐射和接收特性,在暗室中对典型的超宽带印刷天线进行频域特性和时域特性的测量,给出了脉冲信号的辐射和接收过程.研究表明结合天线系统传递函数,可以设计出更符合FCC辐射功率掩蔽的脉冲信号,以及选取出波形保真系数最佳的本地模板信号,从而获得全局性能最优的超宽带系统.     

UWB对CDMA和Bluetooth的干扰研究

文章从时域角度分析了影响UWB高斯脉冲频谱幅度的参数,在频域给出UWB对CDMA和Bluetooth(蓝牙)的干扰表达式,推断出影响干扰的因素为脉冲宽度和脉冲幅度因子,脉冲幅度因子的平方与干扰功率成正比,脉冲宽度的合理选择,使干扰降到最低。经仿真并根据UWB功率谱密度对其进行解释,提出减少干扰的建议。     

两种宽缝超宽带天线的脉冲波形保真度比较

设计了两种小型宽缝结构超宽带天线,一种采用接地CPW馈电方式,另一种采用带状线馈电方式。结果表明这两种天线都有较宽的阻抗带宽。分析了两种天线的特性参数,并比较两种天线的增益和辐射特性,给出两种天线在远区场的脉冲波形比较,并得出不同天线结构对脉冲波形的保真度的影响,这对实际超宽带脉冲天线的设计与应用意义重大。