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31.
In this paper, an Ultra-Wideband (UWB) planar antenna is proposed for the reinforced concrete detection, which consists of a pair of planar waterdrop arms, a microstrip to coplanar par- allel-strips transition and a shallow rectangular cavity. In order to overcome the disadvantages of the shallow cavity, some absorbing material is loaded to weaken the narrow-band effect of the cavity and the crosstalk interference. The simulated and measured results show that the proposed antenna has a large bandwidth from 0.48 GHz to 3.6 GHz with Voltage Standing Wave Ratio (VSWR) below 2 and a fractional bandwidth about 200% under the center frequency of 1.6 GHz, directional radiation char- acteristics and small late-time ringing in the time domain, which can be suitable for nondestructive detection of the reinforced concrete. 相似文献
32.
Burak Yılmaz Serhat Erküçük 《AEUE-International Journal of Electronics and Communications》2013,67(11):926-936
Cognitive radios (CRs) may be sharing multiple frequency bands with primary systems if the CR is a wideband or an ultra wideband (UWB) system. In that case, the CR should ensure all the coexisting primary systems in these bands are detected before it can start data transmission. In this work, we study the primary system detection performance of a wideband CR assuming that there are multiple coexisting primary systems and that these primary systems may be jointly active. Accordingly, we consider the implementation of energy detection scheme in multiple bands followed by two detection methods: (i) a maximum-a-posteriori (MAP) based detection (i.e., joint detection) that takes into account the statistics of simultaneously operating systems in independent bands and (ii) a Neyman–Pearson (NP) test based detection that optimizes the threshold values independently in each band (i.e., independent detection). For a simpler implementation of the independent detection, we show that the threshold values obtained from joint detection can be used in order to achieve the optimum NP test based independent detection results. In addition to quantifying the gain of joint detection over independent detection in terms of probabilities of false alarm and detection for practical scenarios, we also present the operation capability of CRs in terms of the fractions of time the CR can access the channel without interfering with the primary systems. The results are important for the practical implementation of multiband detection when the primary systems are known to be interdependent. 相似文献
33.
Zhonghua Liang Li Jin Xiaodai Dong 《International Journal of Communication Systems》2011,24(6):732-744
Transmitted reference pulse cluster (TRPC) signaling was recently proposed for low data rate ultra‐wideband communications. Compared with the conventional transmitted reference (TR), TRPC has a more compact and uniform spacing for the reference and data pulses and therefore solves the implementation problem posed by the long delay line requirement in the conventional TR. In this paper, downlink multiple access issue is further investigated for TRPC systems. According to the TRPC signaling structure, both code division multiple access (CDMA) and time division multiple access (TDMA) methods are discussed. Theoretical analysis and simulation results show that TDMA outperforms CDMA in both bit error rate performance and throughput. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
34.
无线通信技术发展趋势 总被引:1,自引:0,他引:1
文章对无线通信产业现状以及当前无线通信领域的六大热点进行了讨论,然后从WLAN、WiMAX、UWB等宽带接入技术互补、频谱资源配置、3G技术演进以及宽带接入技术发展等方面,提出了无线通信未来中期的发展趋势。 相似文献
35.
In this paper,the impact of the interference from multiple ultra wideband(UWB) transmitters to a 3rd-generation(3G) terminal is evaluated under UWB emission power limit regulations of federal communications commission(FCC),european telecommunications standards institute(ETSI) and Japan respectively.A three-dimensional interference model is presented where a discrete spatial distribution of UWB transmitters is considered.It is assumed that a mobile terminal and a large number of UWB devices exist in one room simultaneously.A parameter which characterizes the link budget degradation at the victim receiver is defined to measure the UWB interference to 3G systems.The maximum acceptable density of UWB transmitters and the minimum acceptable distance between UWB transmitters and the 3G terminal are analyzed under different link budget degradations.The simulation results demonstrate that the performance of time division-synchronous code division multiple access(TD-SCDMA) is the best,the one of code division multiple access 2000(CDMA2000) is the worst and the one of wideband code division multiple access(WCDMA) lies between them in presence of UWB interference. 相似文献
36.
超宽带无线接入系统在矿井通讯中应用的研究 总被引:3,自引:0,他引:3
本文介绍一种超宽带无线接入技术的特点和接收、发射部分的基本结构。通过对矿井下的具体环境和UWB无线接入系统在井下应用存在问题的分析,证明该技术在煤矿井下应用的实际可行性。 相似文献
37.
在混沌超宽带信号中使用高维复杂混沌系统可以增强信号的安全性,但是降低了混沌系统的易实现性。针对混沌超宽带中所用的混沌系统的复杂性与易实现性的矛盾,利用两种易实现的一维混沌映射基于混沌分支切换并嵌套的方式设计了一种低维易实现的混沌系统,采用Lyapunov指数分析验证了这种系统在较宽的参数范围内具有混沌性。分析表明这种系统所产生的信号无法反映确定的映射关系,不仅增强了混沌信号的复杂度,而且系统又不失易实现性。分析也表明这种混沌信号也具有良好的相关性,因此将这种混沌系统用来设计产生更加安全的混沌跳时超宽带信号。通过对这种混沌超宽带信号与一般的伪随机序列跳时超宽带信号的功率谱对比分析,它所包含的能够对其他传输系统产生干扰的强度较大的离散谱数量更少,故这种混沌超宽带信号将会具有更加广泛的应用领域。 相似文献
38.
39.
研究了在室内多径衰落信道下直接序列超宽带(DS-UWB)系统的时间延迟估计问题,提出了一种基于子空间的高分辨率、低复杂度的时延估计方法。该方法将滑动相关输出的时间平均相关矩阵分解成信号和噪声子空间,然后用MUSIC谱计算,再通过最大值搜索获取时延估计。将滑动相关的时间分辨率与传统相关MUSIC方法的计算复杂度进行了对比。计算机仿真结果表明,在多径时延差接近一个切谱(Chip)周期情况下,新的算法能够有效分辨出多径时延,性能明显高于传统的滑动相关方法。 相似文献
40.