共查询到19条相似文献,搜索用时 109 毫秒
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交替二进制偏移载波(AltBOC)调制信号的自相关函数具有多峰性,导致全球导航卫星系统(GNSS)接收机同步阶段容易产生误捕和模糊跟踪。针对此问题,首先建立了AltBOC信号的模型,并在此基础上提出了一种基于合成相关函数的AltBOC(15,10)信号无模糊跟踪方法。该方法通过设计两路本地辅助信号的波形,与接收AltBOC信号进行相关运算,构造出无边峰的合成相关函数,实现无模糊跟踪。理论分析与仿真结果表明,该方法能够完全消除AltBOC信号自相关函数边峰,保持了主峰的宽度,有效地提高了码跟踪的可靠性,同时具有较好的多径抑制能力。 相似文献
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GNSS信号接收机是GNSS导航卫星的用户设备,是实现GNSS卫星导航定位的终端仪器。它是一种能够接收、跟踪、变换和测量GNSS卫星导航定位信号的无线电接收设备,既具有常用无线电接收设备的共性,又具有捕获、跟踪和处理弱达3.5E-16W~2.5E-17W卫星微弱信号的特性。为此,GNSS信号接收机的构件必须满足这种捕获、跟踪和测量GNSS信号的需求。 相似文献
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GNSS的发展大大增加了导航信号数量,因此开发可接收多个星座信号的GNSS接收机具有很大的意义。本文设计实现了一种简单灵活的新型接收机,主要包括利用MAX2769作为射频前端实现多星座信号覆盖,可重配置的FPGA实现多星座信号的捕获跟踪与数据传输,导航与数据后处理由计算机实现。同时为了兼容多种GNSS信号,设计了通用跟踪环路。测试结果表明设计的GNSS接收机具有体积小、实时性好和兼容性强等特点,满足实际应用需求。 相似文献
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为解决星载GNSS接收机具备高动态信号的跟踪与锁定功能,基于自行研发的星载GPS导航接收机,通过软件升级使其能够工作在LEO、GEO和更高轨道高度上,实现更快的信号捕获能力和对微弱信号的跟踪能力。文中给出了接收机的软硬件架构及功能描述,以及低轨道高动态条件下的模拟器测试结果,通过测试表明,文中给出的接收机具有高动态、微弱GNSS信号的捕获跟踪性能,具备星载搭载条件。 相似文献
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针对高动态GNSS导航接收机跟踪环节中动态性和噪声性能的问题,该文提出一种基于信号参数估计结构的扩展卡尔曼跟踪环。该文首先对高动态GNSS信号进行建模,使用扩展卡尔曼参数估计来实现载波跟踪,并用载波多普勒辅助码环,有效地提高了高动态导航接收机的跟踪性能。仿真结果表明,相比传统上的锁频环辅助锁相环,该文提出的环路具有更小的跟踪误差以及更好的噪声特性。 相似文献
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Abou-Khousa M. Ghrayeb A. El-Tarhuni M. 《Wireless Communications, IEEE Transactions on》2007,6(8):2776-2781
In conventional CDMA receivers, the detection of multipath components and RAKE finger management is normally based on the received signal energy per path. These schemes essentially overlook the interference component contaminating the total received power. Consequently, they exhibit poor multipath detection capability especially at low signal-to-interference-plus-noise ratio (SINR). In this paper, we present a new scheme for multipath detection that takes into consideration the interference level in each resolved path individually. Specifically, the proposed scheme is devised to estimate and cancel the interference per path before detection. To account for the hardware limitations of the receiver, we propose a low complexity version of the above scheme which can be easily incorporated into the receiver structure. Our results show that the proposed scheme provides significant improvements in the detection probability of multipath components over the energy-based schemes. 相似文献
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This paper investigates the constructive use of multipath reflections of Global Positioning System (GPS) signals for navigation in urban environments. Urban navigation applications are generally characterized by a significant presence of multipath signals. In order to maintain reliable and accurate navigation capabilities, it is critical to distinguish between direct signal and multipath. At the same time, multipath reflections can be exploited as additional measurements for those cases where the number of direct path satellites is insufficient to compute the navigation solution. The paper develops a method for the identification of multipath reflections in received satellite signals: i.e., multipath is separated from direct signal and a line-of-site between the GPS receiver and a multipath reflecting object is determined. Once multipath reflections are identified, they can be used constructively for navigation. The method presented in the paper exploits an open-loop batch-processing GPS receiver, laser scanner and inertial navigation system (INS) to identify multipath reflections in received satellite signals. Experimental GPS, inertial and laser scanner data collected in real urban environments are applied to demonstrate identification of multipath reflections. 相似文献
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Identification of the Absence of Direct Path in ToA-Based Indoor Localization Systems 总被引:1,自引:0,他引:1
Mohammad Heidari Kaveh Pahlavan 《International Journal of Wireless Information Networks》2008,15(3-4):117-127
Ultra-wideband (UWB) indoor positioning systems based on time of arrival (ToA) techniques are considered to be the high precision alternatives to those employing received signal strength (RSS) or angle of arrival (AoA) due to their superior time-domain resolution. However, the performance of such systems may easily be degraded by the blockage of the direct path (DP) and occurrence of undetected direct path (UDP) condition. By erroneous detection of the other multipath components (MPCs) as DP, which is the indicator of the true distance between the transmitter and the receiver, substantial localization errors will be introduced into the system. Hence, detection of DP categorizes the receiver locations into two main classes of detected direct path (DDP) and undetected direct path (UDP). The real challenge is to be able to identify the class of the receiver location; therefore, to remedy the ranging measurement in UDP condition. In this paper we propose a methodology to identify and mitigate the UDP conditions, which can substantially improve the overall indoor positioning accuracy. 相似文献
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The binary offset carrier (BOC) modulated signal can improve the positioning accuracy and increase the multipath resistance in global navigation satellite system (GNSS), and it may cause potential ambiguity in the process of signal acquisition and code tracking. In this paper, a simple but efficient unambiguous receiver is firstly proposed for multiple side‐peaks mitigation by implementing correlation of the received BOC signal with local sine wave instead of square wave used at the transmitter. Moreover, the potential degradation of sharpness of the nonlinear correlation induced by the sine wave is well compensated by optimizing the early‐to‐late spacing. The other reason leading to ambiguity is the multipath propagation, so we further propose a maximum likelihood (ML) estimator with Newton iteration method, where the received GNSS signal is modeled via the line‐of‐sight (LOS) component and the first‐arrived non‐line‐of‐sight (NLOS) component. Finally, the analytical expression of multipath propagation Cramer‐Rao bound is derived for the designed ML estimator. Simulation results indicate that compared with the conventional BOC modulation, the proposed sine wave receiver can achieve unambiguous and more precise code tracking performance and thus turns out to be more robust to multipath propagation. 相似文献
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Characterization of ultra-wide bandwidth wireless indoor channels: a communication-theoretic view 总被引:24,自引:0,他引:24
An ultra-wide bandwidth (UWB) signal propagation experiment is performed in a typical modern laboratory/office building. The bandwidth of the signal used in this experiment is in excess of 1 GHz, which results in a differential path delay resolution of less than a nanosecond, without special processing. Based on the experimental results, a characterization of the propagation channel from a communications theoretic view point is described, and its implications for the design of a UWB radio receiver are presented. Robustness of the UWB signal to multipath fading is quantified through histograms and cumulative distributions. The all RAKE (ARAKE) receiver and maximum-energy-capture selective RAKE (SRAKE) receiver are introduced. The ARAKE receiver serves as the best case (bench mark) for RAKE receiver design and lower bounds the performance degradation caused by multipath. Multipath components of measured waveforms are detected using a maximum-likelihood detector. Energy capture as a function of the number of single-path signal correlators used in UWB SRAKE receiver provides a complexity versus performance tradeoff. Bit-error-probability performance of a UWB SRAKE receiver, based on measured channels, is given as a function of the signal-to-noise ratio and the number of correlators implemented in the receiver. 相似文献
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Spread spectrum (SS) multiple access techniques have been proposed for third generation broadband wireless access. We develop an analytical framework to quantify the effects of spreading bandwidth on SS systems operating in dense multipath environments in terms of the receiver performance, receiver complexity, and multipath channel parameters. In particular, we consider wide-sense stationary uncorrelated scattering (WSSUS) Gaussian channels with frequency-selective fading. The focus of the paper is to characterize the combined signal of the RAKE receiver fingers tracking the strongest multipath components. Closed form expressions for the mean and the variance of the total RAKE receiver output signal-to-noise ratio (SNR) are derived in terms of the number of RAKE fingers, spreading bandwidth, and multipath spread of the channel. The proposed problem is made analytically tractable by transforming the physical RAKE paths into the virtual path domain. A representative result indicates that for SS systems with 5 MHz signal bandwidth operating in a channel with constant power delay profile having 5 μs spread, the average SNR gain from increasing the number of RAKE fingers from one to three is 3.8 dB and from three to five is 1.5 dB. Furthermore, the reduction in the variation of SNR is 1.1 dB and 0.4 dB for the same increments in the number of fingers 相似文献
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A beam-space adaptive nulling technique that has potential for applications in communication circuits degraded by multipath signals is described. The technique is based on a well-known vector relationship in beam space. A linear transformation is used to prevent the degradation of the desired signal reception. Results are presented from tests of the technique that were conducted using real multipath data. The data used in these tests were recorded using a 32-element sampled aperture antenna (SAMPAR). These measurements were carried out on an over-water path. The direct signal, i.e. the signal that propagates via the shortest path from the transmitter to the receiver antenna, is selected as the desired signal; its reception is enhanced by suppressing the unwanted signals, i.e. the multipath signals that propagate via a reflection from the surface of the water. Examples are given in which the wanted and unwanted signals are separated by less than a beamwidth 相似文献
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Modeling of the TOA-based distance measurement error using UWB indoor radio measurements 总被引:3,自引:0,他引:3
Time of arrival (TOA) estimation used with ultra wideband (UWB) transmission is currently the most popular technique for accurate indoor geolocation. Due to severe indoor multipath conditions, these techniques often suffer from significant inaccuracy in location estimation. In this paper, we introduce a model for the error in estimated distance as measured from the estimated TOA of the direct path (DP) in a typical multipath indoor environment. The TOA estimation error has two components, (1) the errors caused by the multipath dispersion affecting any signal path and (2) the errors caused by undetected direct path (UDP) conditions. The statistical behavior of this error is also a function of the system bandwidth. The empirical data from UWB indoor measurements in an office building are used to design a model for the distance measurement error. This model relates the behavior of the two components of the TOA estimation error to the bandwidth of the system. 相似文献
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The effect of a secondary path signal on the detectability of the symbol rate spectral line of a binary phase-shift keyed (BPSK) signal by a delay and multiply receiver is investigated. The measure of detectability used is the rate line signal-to-noise ratio. The parameters that define the secondary path signal are initially modeled as deterministic quantities; the phase of the secondary path signal is then taken to be a random variable independent and uniform on (0, 2π). It is found that, with deterministic path parameters, the presence of a secondary path can seriously affect the detectability of BPSK rate lines. When the phase is taken to be uniform on (0, 2π) over the receiver observation time, then the delay and multiply receiver performs as if no multipath is present. In this case, a noncoherent power addition of the primary and secondary path signals occurs 相似文献