基于升降HFM组合的高分辨抗混响波形设计

双曲调频（Hyperbolic Frequency Modulation, HFM）波形是传统主动声呐常用的信号波形,具有多普勒不变性。HFM信号虽然便于匹配,但无法进行准确的测速、测距。升降HFM组合的V型双曲调频（V-Hyperbolic Frequency Modulation, V-HFM）脉冲信号,可以解决HFM的距离-速度耦合模糊问题,但在多目标情况下会有虚假亮点干扰问题。受V-HFM组合方式启发,文章提出一种新的HFM组合方法：N型双曲调频（N-Hyperbolic Frequency Modulation,N-HFM）组合信号。该信号形式可以降低虚假亮点出现的概率。水池实验表明：在多目标情况下,N-HFM脉冲信号可以实现距离和速度二维检测的较高分辨力,以及较强的抑制虚假目标的能力。     

新型梳形抗盐聚合物的流变性

进行了不同条件下聚丙烯酰胺和梳形抗盐聚合物溶液的粘度及流变性测定,发现根据不同条件下聚合物溶液的流变参数可以定性地判断三次采油用聚合物的抗盐能力大小和趋势。聚合物的流变性分析可作为评价聚合物抗盐性能的一条新途径,具有一定的实用价值。     

光纤光栅梳状滤波器的设计和制作

光纤光栅梳状滤波器的设计和制作     

电压调谐梳状线带通滤波器的设计

研究用梳状线滤波器的原理设计可调谐带通滤波器的问题,通过改变加载的变容二极管的电容,实现该带通滤波器中心频率的变化。仿真优化设计了一个950MHz-1450MHz的电压调谐带通滤波器。     

扩声系统中的梳状滤波失真

扩声系统为满足覆盖区要求,增加声压级或解决声场均匀度等问题,通常需要使用多个扬声器箱供声。但这些安装在不同位置的扬声器辐射相干的宽频带声波相遇时,由于各声波之间存在着时间差(相位差),会发生有些频率的振幅相加,有些频率的振幅抵消,使原来平坦的频响特性出现很多峰—谷相间的,如图1那样的“梳状滤波器”特性。这种特性破坏了系统的音质。     

新型梳状聚氨酯缔合型增稠剂的合成及性能研究

将中间含不同长度烷基的疏水性二醇引入到聚氨酯预聚体链段中,得到一系列链段中带悬挂基团的梳状聚氨酯缔合型增稠剂,并用FTIR和GPC对其结构进行了表征。着重研究了疏水性二醇与总羟基(疏水性二醇与聚乙二醇)的摩尔比以及中间疏水基的大小对增稠剂增稠效果的影响。结果表明,疏水基团是决定增稠剂增稠效果的决定性因素,随着疏水性二醇所占比例的增大,增稠效果显著加强;同样中间烷基链段的碳原子数的增多,缔合作用加强,增稠效果变好。     

新型任意波形信号发生器的设计

系统利用直接数字频率合成技术(DDS)完成任意波形信号发生器的设计.它采用单片机(MCU)+复杂可编程逻辑器件(CPLD)的双控制芯片架构,由MCU管理人机接口、与上位机通信以及产生DDS控制信号等,基于CPLD实现DDS各数字功能模块.实验表明:本系统除能产生参数可调的标准信号(如正弦、方波、三角波等)外,还可以实现...     

微带与腔体梳状线可调带通滤波器设计

主要介绍梳状线可调滤波器设计的两种结构形式,平面结构采用微带线,使用ADS软件仿真设计;三维结构采用同轴腔体,使用HFSS软件仿真设计。梳状线滤波器因其具有结构紧凑的特性,在小型化滤波器的应用场合中较为常见,就两种以梳状线滤波器的工作原理,采用不同的传输线形式进行设计,并进行成本,性能等方面的对比。     

星座卫星通信系统前向链路梳状滤波器补偿设计

针对星座卫星前向链路数字上调频部分最后一级梳状滤波器(CIC滤波器)频谱特点,设计了一个低通补偿滤波器,它能有效弥补CIC滤波器通带内的频谱衰减,两者合成一个较理想的低通滤波器,与前一级基带成形滤波器配合能有效抑制码间干扰,整体阻带旁瓣也较小.最后将该补偿滤波器与基带成形滤波器合成一个滤波器,与后面CIC滤波器组成二级...     

多级锐化的梳状抽取滤波器

针对传统的递归型级联积分-梳状抽取滤波器(CICDF)频响特性不理想、功耗较大、最大电路速率受限等问题,提出了一种多级锐化的梳状抽取滤波器(MSCDF)。该滤波器利用降序素数分解和部分多相分解相结合的方法将CICDF转化为多级多相结构以降低功耗和放宽对电路速率的限制,并从第二级开始逐级进行锐化处理从而使抽取器的频响得到改善。仿真结果表明,在抽取因子为非素数的情况下,MSCDF不仅能够有效地改善CICDF的通带衰减和混叠抑制性能,而且与频响相近的完全锐化抽取器(FSCDF)相比,功耗更小,最大电路速率更高。     

四川旅游纪念梳创新设计研究

目的以四川旅游纪念品的开发及四川省文化特色的发扬为出发点,研究四川省旅游纪念梳的创新设计方法,以改善目前市面上所售卖的旅游纪念梳加工粗陋且造型图案同质化严重的现状,从而促进四川省旅游创意文化产业的发展。方法主要采取实地调查法与问卷调查法,对四川省旅游纪念品售卖点进行现有旅游纪念梳实际售卖情况的考察与消费者对纪念梳需求意向的资料收集及分析。结论通过分析提出材料浑然一体、造型抚今追昔、工艺传承开拓三种创新设计方法,并将这三种方法运用于旅游纪念梳的创新设计实践中。力图通过理论研究和设计实践为四川旅游纪念梳的开发提供参考,使之具有较高品质和文化内涵,这些方法对今后相关的设计也可提供一定理论支持。     

探测尾流自导鱼雷主动声呐的波形设计

为了实现对不同速度尾流自导鱼雷的稳定探测,建立尾流自导鱼雷典型弹道模型,对运动平台主动声呐混响和鱼雷目标回波的多普勒特性进行分析。研究结果表明对于探测尾流自导鱼雷的主动声呐来说,当鱼雷速度小于2倍平台速度时目标多普勒较小且不稳定,仅依靠多普勒滤波难以完全避开混响干扰并实现稳定探测。提出使用宽带多普勒敏感信号与CW信号的组合形式来探测尾流自导鱼雷。仿真给出了组合信号的距离、速度分辨力和混响抑制能力,证明了其性能良好。     

An Efficient Genetic Hybrid PAPR Technique for 5G Waveforms

Non-orthogonal multiple access (NOMA) is a strong contender multicarrier waveform technique for the fifth generation (5G) communication system. The high peak-to-average power ratio (PAPR) is a serious concern in designing the NOMA waveform. However, the arrangement of NOMA is different from the orthogonal frequency division multiplexing. Thus, traditional reduction methods cannot be applied to NOMA. A partial transmission sequence (PTS) is commonly utilized to minimize the PAPR of the transmitting NOMA symbol. The choice phase aspect in the PTS is the only non-linear optimization obstacle that creates a huge computational complication due to the respective non-carrying sub-blocks in the unitary NOMA symbol. In this study, an efficient phase factor is proposed by presenting a novel bacterial foraging optimization algorithm (BFOA) for PTS (BFOA-PTS). The PAPR minimization is accomplished in a two-stage process. In the initial stage, PTS is applied to the NOMA signal, resulting in the partition of the NOMA signal into an act of sub-blocks. In the second stage, the best phase factor is generated using BFOA. The performance of the proposed BFOA-PTS is thoroughly investigated and compared to the traditional PTS. The simulation outcomes reveal that the BFOA-PTS efficiently optimizes the PAPR performance with inconsequential complexity. The proposed method can significantly offer a gain of 4.1 dB and low complexity compared with the traditional OFDM.     

An Efficient Hybrid PAPR Reduction for 5G NOMA-FBMC Waveforms

The article introduces Non-Orthogonal Multiple Access (NOMA) and Filter Bank Multicarrier (FBMC), known as hybrid waveform (NOMA-FBMC), as two of the most deserving contenders for fifth-generation (5G) network. High spectrum access and clampdown of spectrum outflow are unique characteristics of hybrid NOMA-FBMC. We compare the spectral efficiency of Orthogonal Frequency Division Multiplexing (OFDM), FBMC, NOMA, and NOMA-FBMC. It is seen that the hybrid waveform outperforms the existing waveforms. Peak to Average Power Ratio (PAPR) is regarded as a significant issue in multicarrier waveforms. The combination of Selective Mapping-Partial Transmit Sequence (SLM-PTS) is an effective way to minimize large peak power inclination. The SLM, PTS, and SLM-PTS procedures are applied to the NOMA-FBMC waveform. This hybrid structure is applied to the existing waveforms. Further, the correlated factors like Bit Error Rate (BER) and Computational Overhead (CO) are studied and computed for these waveforms. The outcome of the work reveals that the NOMA-FBMC waveform coupled with the SLM-PTS algorithm offers superior performance as compared to the prevailing systems.     

Digital Walsh-Fourier Analysis of Periodic Waveforms

A digital process is described for obtaining the Walsh-Fourier series of a periodic waveform, which requires at most two cycles of the waveform under measurement. The first cycle of the periodic waveform is required for the determination of period. The coefficients of the Walsh-Fourier series are obtained during the second cycle only, and they are available at the end of the cycle. Given the Walsh-Fourier coefficients of the periodic wave, the individual sine and cosine components of its Fourier series may be obtained using conversion formulas. Special features of the process are that there are no theoretical low-frequency limitations, and for an instrument with an internal clock whose frequency lies in the range 1 Hz to 1 MHz, the fundamental frequency component of a signal that can be analyzed would be in the range 1 cycle in 11.6 days to 60 Hz. Also, whereas the digital processes required to obtain a Fourier series directly are complicated by the need to multiply sample values of voltage by sines and cosines, which are themselves functions of time, determination of Walsh-Fourier coefficients is achieved very simply by using gating circuits. Generation of the required Walsh functions for a periodic signal of any fundamental frequency within the design range has been achieved.     

时反处理抑制混响提高信混比实验室波导实验研究

1引言 时反镜及时反处理的研究已经受到了国内外众多科学研究者的密切关注.用时反镜所作的辐射信号场聚焦特性的研究[1]表明,声场是可建模预测的.声场的可预测性为匹配场处理(MFP)和时反处理(TRP)提供了基础.     

混响室法测量吸声系数的不确定度评价

通过对材料吸声系数混响室法测量分析,确定了该类方法测量结果不确定度的来源。对不确定度构成分量进一步分析,结果表明吸声系数的测量不确定度主要由混响时间测量的不确定度所决定,混响室体积、试件尺寸和声速测量的不确定度对吸声系数测量结果的不确定度贡献很小。混响时间测量结果的不确定度主要取决于混响室声场扩散程度,而测量装置本身引入的不确定度贡献较小。     

空时处理及在混响抑制中的应用

1.引言: 在水下反潜领域,为了有效对抗先进的安静型潜艇的威胁,低频拖线阵主动声纳逐渐受到重视.在浅水环境下,混响严重地影响了主动声纳的检测性能,因此混响干扰及其抑制是主动声纳在实际应用中必须面对的问题.已有的试验表明,浅海低频混响主要由海洋的地层结构所控制,这样,运动平台的混响场就具有特定的空时结构特性.