Orthogonal wideband hybrid-coding radar waveforms design

To obtain wideband orthogonal waveforms of radar systems with high-range resolution and good correlation properties, this paper proposes two types of orthogonal wideband hybrid-coding waveforms, polyphase discrete frequency (PDF) waveforms and polyphase signed-chirp (PSC) waveforms. Using an intra-pulse hybrid modulation, high-range resolution can be obtained, and good correlation properties between different waveforms are easier to optimize within a larger optimization space. Specifically, good correlation properties of the PDF waveforms are indeed easier to achieve without a loss of range resolution, as occurs with a discrete frequency coding waveform. Compared with polyphase coding waveforms, the signal bandwidth of each PSC waveform is twice as large as that of sub-pulse chirp signals, and superior correlation properties are obtained. Finally, various designed waveforms optimized by the genetic algorithm are provided to demonstrate the effectiveness of these proposed wideband hybrid-coding waveforms.     

超宽带圆盘形定向天线阵列波形的优化

本文分析了超宽带(UWB)脉冲波形对圆盘形天线阵列的角度分辨率的影响，对UWB圆盘形定向天线阵列中的波形进行了优化。文中给出了具体的例子，得出了优化波形。优化波形比相应的Gaussian波形在角度分辨性能上得到了明显的提高。     

基于编码项补偿的OFDM信号SAR成像

该文探讨了正交频分复用(OFDM)波形在SAR中可能的应用,重点讨论了基于该信号体制的SAR成像。OFDM波形改变了传统线性调频信号平坦的频谱,给高分辨成像带来了新的问题。该文深入分析了OFDM波形的信号特点,推导了其2维频谱,提出了一种适合OFDM SAR精确成像的方法。该成像算法利用对编码项的补偿,实现了OFDM波形下的距离迁徙校正,有效降低了编码信号对旁瓣的影响,充分提高了OFDM波形的成像性能。仿真结果验证了所提方法的有效性。     

Observation of the internal waveforms in high-speed high-density LSIs using an EOS prober

Electron beam (EB) probing has been used to observe the internal waveforms in ULSLs. However, as the speed of LSIs increases and their power consumption decreases, the temporal and voltage resolution of EB probing is going to be inadequate for measuring these waveforms. Electro-optic sampling (EOS) probing is expected to overcome this limitation, provided its spatial resolution can be improved. In this paper, forming a via on the interconnection under test is proposed for practically improving spatial resolution. The effectiveness of this method and the dependence of the detected signal level on testing pad area are clarified by simulation. To verify these results, vias are formed in ECL SRAMs by focused ion beam trimming, and waveforms with frequency as high as 100 MHz and swing as small as 30 mV are successfully observed. Using this technique, the dependence of the detected signal level on testing pad area is verified, and it is confirmed that the amplitude change below 10 mV and the delay time below 100 ps can be measured. With the improved spatial resolution, EOS probing enables us to observe high-frequency and small-swing waveforms even in high-density fine interconnections. In future, this technology will be crucial for observing internal waveforms in LSIs.     

MIMO Radar Ambiguity Properties and Optimization Using Frequency-Hopping Waveforms

The concept of multiple-input multiple-output (MIMO) radars has drawn considerable attention recently. Unlike the traditional single-input multiple-output (SIMO) radar which emits coherent waveforms to form a focused beam, the MIMO radar can transmit orthogonal (or incoherent) waveforms. These waveforms can be used to increase the system spatial resolution. The waveforms also affect the range and Doppler resolution. In traditional (SIMO) radars, the ambiguity function of the transmitted pulse characterizes the compromise between range and Doppler resolutions. It is a major tool for studying and analyzing radar signals. Recently, the idea of ambiguity function has been extended to the case of MIMO radar. In this paper, some mathematical properties of the MIMO radar ambiguity function are first derived. These properties provide some insights into the MIMO radar waveform design. Then a new algorithm for designing the orthogonal frequency-hopping waveforms is proposed. This algorithm reduces the sidelobes in the corresponding MIMO radar ambiguity function and makes the energy of the ambiguity function spread evenly in the range and angular dimensions.      

MIMO天波雷达非连续谱正交相位编码波形设计

为提高MIMO天波雷达的发射波形的距离分辨力,以减小检测单元尺寸,改善信杂比和目标定位精度,针对MIMO天波雷达工作环境恶劣,干扰较多,寂静频带非连续的情况,用几个不连续的寂静频带来合成大的有效带宽,给出了两种非连续谱条件下正交相位编码波形的设计方法。采用产生满足特定频谱约束的相位编码信号的循环迭代算法生成,利用算法对初值的敏感性,设定不同随机初值,即可生成一组发射波形,仿真证明了该方法的有效性。通常谱约束越强,波形性能（自相关、互相关和分辨力等）越差,调节谱约束的强弱,即可得到满意的正交相位编码波形,所设计的波形充分利用了频谱资源,大幅提高了发射波形的距离分辨力。      

利用多普勒分辨的FMCW SAR成像算法

调频连续波合成孔径雷达(FMCW SAR)具有低成本、低功耗的优势,小型或微小型SAR普遍采用FMCW工作体制。目前已有的FMCW SAR成像方法均是依靠发射宽带信号获取距离向高分辨,本文给出一种新的FMCW SAR成像算法。该算法除了利用距离分辨外,还可通过利用脉内多普勒频率,有效利用连续波较好的多普勒分辨率,使FMCW SAR在近距离成像时,距离向的分辨率可以不仅受带宽限制,在FMCW带宽较窄时也能够提供良好的距离向分辨率。在算法流程、成像视线方向和分辨率三方面,与基于距离分辨率的传统FMCW SAR成像算法进行对比,分析给出的成像算法的性能,并通过仿真实验进行验证。      

跳时序列调制超宽带正交Hermite脉冲串雷达信号分析

超宽带正交Hermite脉冲是一类非常适合表征超宽带(UWB)穿墙探测雷达工作波形的脉冲,具有设计灵活、频谱利用率高、实现简单、波形存在解析表示方便理论分析等特点。该文从定义出发推导了跳时调制超宽带(TM-UWB)Hermite脉冲串波形的模糊函数解析表达式,仿真分析了模糊特性与跳时序列的自相关特性、序列周期以及与Hermite脉冲平均重复时间间隔,脉冲的阶数和时间尺度因子的关系,并探讨了在穿墙探测环境下该波形作用的旁瓣抑制和杂波抑制等关键技术。     

随机多元码脉位调制和脉间二元序列相位调制的混合波形设计

本文提出了一种利用随机多元码脉位调制（ＰＰＭ）和脉间伪随机或随机二元序列相位调制（ＰＭ）相结合的混合波形设计方法．推导并分析了这种混合波形的平均模糊函数．结果表明这种混合波形不仅具有结构简单、易于处理等特点，而且具有良好的测距和测速性能，以及良好的ＥＣＣＭ性能．     

雷电流波形的观测及沿通道时空分布的数值模拟

 2005年夏季在山东利用人工引发雷电技术,在放电通道底部测量到了微秒量级的10次回击电流波形.基于Diendorfer and Uman(DU)模式,本文对雷电回击电流波形沿通道的时空分布特征进行了数值模拟.结果表明,如果合理的选取参数,基于DU模式的模拟结果与光学观测结果基本一致;与其他模式相比,DU模式是更合理的.     

Electronically adjustable delay for Josephson technology

An electronically adjustable time delay circuit for superconducting technology is reported. In conjunction with a superconducting sampler on the same chip, the delay circuit has allowed measurement of waveforms with an apparent resolution of 8.5 ps. The delay circuit permits flicker-free oscilloscope displays of fast waveforms, and provides the circuitry needed for further speed advances in superconducting sampling and other ultra-fast measurement techniques.     

Principles of space-time array processing for ultrawide-bandimpulse radar and radio communications

The emerging ultrawide-band (UWB) impulse technology has found numerous applications in the commercial as well as the military sector. The rapid technological advances have made it possible to implement (cost-effective, short-range) impulse radar and impulse-radio communication and localization systems. Array beamforming and space-time processing techniques promise further advancement in the operational capabilities of impulse radar and impulse-radio communications to achieve long-range coverage, high capacity and interference-free quality of reception. We introduce a realistic signal model for UWB impulse waveforms and develop the principles of space-time array processing based on the signal model. A space-time resolution function (STRF), a space-frequency distribution function (SFDF) and a monopulse-tracking signal are derived for impulse waveforms received by a self-steering array beamforming system. The directivity peak-power pattern and energy pattern of the beamformer are also derived. Computer plots of the STRF, SFDF and the beam patterns are obtained. The directivity beam patterns of impulse waveforms are sidelobe-free and, therefore, there is no need for sidelobe suppression via amplitude weighting of the array elements. Also, the resolution angle for the beam patterns is derived as a decreasing function of array size and frequency bandwidth. Electronic beamsteering based on slope processing of monopulse waveforms is described     

基于OFDM的太赫兹通感一体化波形设计与性能分析

针对当前正交频分复用(OFDM)通信系统,开展了基于二维快速傅里叶变换(2D-FFT)的一体化波形研究。探究了太赫兹OFDM波形感知特性,通过理论和仿真计算相结合,分析不同频率和带宽下波形参数设计的影响,以指导太赫兹OFDM通信感知一体化(ISAC)系统设计。理论和仿真计算分析表明,太赫兹OFDM通信感知一体化系统具有多目标感知能力,太赫兹大带宽特性使其感知距离分辨力高达厘米级,速度分辨力可达分米每秒级,且低感知信噪比情况下仍能解析出目标的位置与速度信息,证明了OFDM通信感知一体化波形能够支撑太赫兹窄波束移动通信。     

High-resolution alignment of sampled waveforms

Waveforms are often sampled faster than the Nyquist rate to obtain desired temporal resolution, even though, theoretically, oversampling adds no information and should not be necessary. This paper shows how high resolution can be achieved efficiently from data sampled at the Nyquist rate by working with coefficients of the Fourier-series expansion of the continuous interpolating waveform. Practical algorithms are presented for aligning and comparing waveforms, locating peaks, resolving superimpositions, and averaging overlapping waveforms. The algorithms prove to be more accurate, and to require fewer computations and less storage than techniques which employ continuous oversampling in many signal-processing applications, particularly template matching.     

107 cm全色AC-PDP驱动波形的设计和比较

介绍两组提高AC—PDP的发光效率、对比度和亮度的驱动波形。首先给出了传统的驱动波形,然后讨论了两组新的驱动波形。在PDP的每个子场中,驱动过程可分为三个时期：初始期、寻址期和维持期。在初始期,新的初始波形能提高对比度和分辨率,也能降低寻址电压。在维持期,新波形的脉冲可以减少自擦除放电,从而提高发光效率。文中简要介绍了PDP的工作原理并对不同驱动波形的比较作了相应的讨论。最后给出了采用该驱动波形的107cmPDP测得的实验结果,证实了这两种新波形的可行性。     

Write and erase waveforms for high-resolution AC plasma display panels

The successful operation of ac plasma display panels (PDP) depends on the optimization of panel parameters such as chamber gap, gas pressure, line width, and the use of half or full-select cancellation techniques. As resolution increases, however, so does the importance of the write and erase waveforms. A unique set of write and erase waveforms which are specifically designed to optimize the performance of high-resolution PDP's are discussed.     

Voltage-comparator-based measurement of equivalently sampledsubstrate noise waveforms in mixed-signal integrated circuits

This paper describes measurement of substrate noise waveforms in mixed-signal integrated circuits. This method uses wide-band chopper-type single-ended voltage comparators as on-chip noise detectors. By analyzing equivalently sampled comparator outputs in synchronized operation, the noise voltage in the auto-zero and compare modes can be measured separately, and noise waveforms were experimentally reconstructed to within 0.5-ns accuracy. The noise transmission path was analyzed, and this showed that the noise sampled at the auto-zero mode of the comparator can be used to reconstruct substrate noise waveforms with high resolution. The results also explain the influence of noise coupling on analog circuits widely used in on-chip analog-to-digital converters     

Ambiguity functions of laser-based chaotic radar

The ambiguity functions of a newly developed laser-based chaotic radar (CRADAR) system are studied. In the CRADAR system, the chaotic waveforms can be generated either by an optically injected (OI) semiconductor laser, or a semiconductor laser with optoelectronic feedback (OEF). The ambiguity functions of the chaotic pulsation and chaotic oscillation waveforms obtained experimentally from the CRADAR system with the respective OEF and the OI schemes are examined and compared. In the cross-ambiguity functions, both types of the chaotic waveforms demonstrate their excellent capabilities in the electrical counter-countermeasures (ECCM) that civilian and military applications desire. In the auto-ambiguity functions, the chaotic oscillation waveform shows better unambiguous detection quality than the chaotic pulsation waveform that an ideal thumbtack-like ambiguity function with minimal sidelobes is found. Moreover, variations in the peak value and the full width at half-maximum of the auto-ambiguity function of the chaotic oscillation waveform along the principal axes are also investigated. By having the features of both ultrawideband radar and random signal radar, the chaotic oscillation waveform of the CRADAR system with the OI scheme is shown to possess the advantages of high range resolution, excellent ECCM capability, ideal thumbtack-like ambiguity function, and uncoupled range and range rate resolution functions.     

用Chirp—z变换获得雷达目标回波波形特征

探讨了高分辨率雷达视频回波波形特征．提出对回波信号作Ｃｈｉｒｐ－ｚ变换，以提高频谱的分辨率．还对两类实测毫米波高分辨率雷达目标回波波形进行了Ｃｈｉｒｐ－ｚ变换及Ｆｏｕｒｉｅｒ变换，并对两类结果进行了比较，结果证明对雷达回波波形作Ｃｈｉｒｐ－ｚ变换获得的视频波形特征既满足同一目标特征稳定性，又容易区分两类不同目标．     

集中式MIMO雷达研究进展：正交波形设计与信号处理

集中式多输入多输出（Multiple Input Multiple Output,MIMO）雷达通常利用正交波形增加发射波形自由度,采用数字阵列拓展空间收发自由度,使得雷达接收机的天线孔径获得明显扩展,最终带来空间分辨率、测角精确度、杂波抑制能力等大幅度提升。但是,这些性能提升的前提是发射波形具有正交特性。事实上,在实际应用中,在不牺牲时域/频域资源情况下,受限于时宽带宽积,无法获得完全正交的波形集合,从而限制了MIMO雷达系统性能。本文对集中式MIMO雷达正交波形复用的技术原理进行了系统回顾,分别归纳了三种快时间发射波形设计方法：时分复用（Time Division Multiplexing, TDM）、码分复用（Code Division Multiplexing,CDM）和频分复用 （Frequency Division Multiplexing, FDM）,以及两种慢时间发射波形设计方法：多普勒分复用（Doppler Division Multiplexing,DDM）和随机相位编码波形,并对其优缺点进行对比。同时,对快时间MIMO和慢时间MIMO的信号处理流程进行归纳综合,给出基于匹配滤波的集中式MIMO雷达统一信号处理框架。为了展示不同波形对成像性能的影响,本文给出了基于三维匹配滤波的MIMO雷达成像结果。最后,结合实际应用问题,指出当前MIMO雷达面临的技术难点和发展趋势。