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1.
在卫星信号接收的过程中,量化是模数转换的重要环节,信号量化会带来能量损失,对于信号后续的处理产生影响,根据信号特性选取合适的量化位数和系统基准功率可以有效改善这种损失.本文采用量化前后信号信噪比(signal to noise ratio,SNR)对比的形式来直观表示量化损耗,并给出了一般性分析公式.说明了自动增益控制(automatic gain control,AGC)模块在信号量化中的作用,结合量化损耗公式,通过确定最佳增益系数给出了一种基准功率的选取方式,使得不同SNR的信号量化损耗明显降低.仿真结果表明：在低位量化时,该方式对卫星导航信号的量化损耗能改善约1.5 dB.该分析对于接收机的设计以及工程实现具有一定的参考意义. 相似文献
2.
现阶段导航接收机设计的基本架构是FPGA＋DSP或者FPGA＋ ARM 的工作方式。接收机存在研发时间长,研发难度较大的特点,且DSP/ARM 处理环路跟踪的同时需处理协议上的许多操作,在实现上较为复杂,实时性不高。基于SOC技术,利用Xilinx公司提供的协处理器软核代替DSP部分功能,用于在单片FPGA内实现导航接收机的跟踪环路,并根据实际情况,设计了硬件加速器和相关值预处理模块,利用时分复用的方式节约了硬件资源,在单片FPGA上实现了跟踪环路的设计,降低了硬件成本,为高性能导航接收机芯片设计提供了一种思路。 相似文献
3.
在GPS接收机中,对GPS信号的捕获是最为关键的第一步。对GPS信号中伪码的初始相位和信号载频的估计是捕获的两个基本任务。在某些特定的环境下,比如室内、城市街道、树林,对信号的捕获变得困难。针对这个困难可以通过提高估计精度以减少估计误差带来的相关损失。但是信号累积和估计精度的提高都需要极大地增加运算量。本文提出了将CORDIC算法引入到GPS接收机,在保证大运算量的情况下,实现快速的计算时间。介绍了GPS信号捕获的基本原理,讨论了使用CORDIC算法的必要性以及实现方法。最后通过仿真验证了CORDIC算法能够有效提高GPS接收机的捕获速度。 相似文献
4.
针对对导航信号信息传输速率有更高要求的信号,如精密定位信号,提出二进制相移键控-码移键控(BPSK-CSK)联合调制方法,以解决传统的码移键控(CSK)调制信号在接收端对相关器资源需求量大、解调计算复杂度高的问题. 本文方法将分组调制的电文再分为极性位与码相位,使得接收端由原本通过相关求和进行解调,转变为通过较少相关求和运算与子码匹配两步完成电文解调,减少了接收机解调电文所需相关器的数量并降低参与运算的数据量级. 所提方法在极性位数为1或2时,与传统CSK相比,可以实现在电文解调误比特性能损耗可忽略不计的情况下,计算复杂度降低为原来的50%或25%. 当极性位数大于2时,该方法以解调性能为代价降低计算复杂度,但此时结合信道编码,BPSK-CSK仍可实现等计算复杂度下的误比特率降低. 相似文献
5.
载波数字振荡器(NCO)是导航接收机中对接收信号进行载波剥离处理的关键部分. 在接收机的基带数字信号处理模块中,NCO通过量化位宽和地址字长分别对本地载波信号的幅值和频率进行量化,即通过存储器数据的位宽和深度设计本地载波. 在给定输入信号/干扰动态范围下,根据本地载波的特点,优化设计了载波NCO中只读存储器(ROM)的幅值量化位宽和地址字长,使其适应实际工程需求,在保证信噪比(SNR)损耗和频率误差的条件下避免了本地载波存储的冗余. 实验结果表明:从需求出发设计导航接收机本地载波的最优位宽和深度,可保证数字下变频SNR损耗小于0.1 dB,本地载波实际输出频率相对误差小于0.1%,且最优位宽和深度小于优化前,减小了存储资源占用率,有效地提高了本地载波输出信号在动态信号和干扰下的适应性. 相似文献
6.
针对欺骗干扰评估场景复杂、反欺骗策略繁多等所导致的量化评估难度大的问题,建立了欺骗对抗场景到欺骗对抗效果的评估模型和映射过程,并从欺骗对抗场景中的功率空间和欺骗对抗效果中的欺骗有效概率出发,设计了基于欺骗有效功率可行域的评估方法与指标。仿真结果表明,该评估方法可以实现不同反欺骗策略之间性能的量化对比,能够为接收机反欺骗算法选择和优化提供量化评估方法。 相似文献
7.
在传统基于FPGA+DSP架构的导航接收机中,跟踪模块处于开环处理模式,存在实时性和可靠性差的问题,同时现场可编程逻辑门阵列(FPGA)和数字信号处理(DSP)之间大量的数据通信导致了IO资源和功耗的增加. 基于片上系统(SoC)架构提出了一种卫星导航接收机的闭环跟踪环路方案,整个跟踪处理过程在FPGA内实现了完整的闭环处理,有效地解决了开环跟踪存在的问题,极大地减少了FPGA与CPU之间的数据通信量. 此外,所有跟踪通道通过时、分复用的方式共用一个跟踪环路处理模块,有效节约了硬件资源,降低了成本,为小型化、低功耗卫星导航芯片的设计与发展奠定了基础. 相似文献
8.
随着我国北斗导航系统“全球组网”序幕的拉开,设计实现接收机的兼容互操作功能已变成接收机设计领域的一个研究热点。文中针对GNSS双频兼容互操作接收机信号捕获环节设计中遇到的处理时间长、捕获精度低、硬件资源消耗大、兼容性差等问题,设计一种基于频域处理的信号捕获算法。该算法在传统频域捕获的基础上,优化频域转换资源利用与遍历方式,在能量累加方面加入相干与非相干累加方式,达到微弱信号捕获。借助Xilinx软件Vivado及其仿真工具,对整个捕获系统进行了仿真实现,验证了算法设计的准确性,本算法可以捕获信号功率-135 dB以上的信号,可捕获的载波多普勒频率范围满足实际工程需求。在实际工程验证中,本算法能较好地满足工程应用性能要求。 相似文献
9.
针对民航飞机利用陆基增强系统(GBAS)进行精密进近着陆过程中,GBAS机载甚高频数据广播(VDB)接收机所受到的同频干扰问题,提出采用盲信号分离算法,对VDB接收机所接收到的期望信号与同频干扰信号进行分离,并通过识别解码数据中的机场标识(ID),得到所需期望信号,从而抑制同频干扰信号. 分析并仿真了基于快速固定点(Fast ICA)算法、自然梯度算法和等变自适应分离(EASI)算法,对VDB接收机接收到的混合信号进行分离的机理和同频干扰抑制的实现. 仿真结果表明,这三种算法均能有效分离期望信号与同频干扰信号,进而进行同频干扰抑制,并通过比较三种算法的收敛速度、串音误差和误码率,得出 Fast ICA算法更适合用于VDB信号的同频干扰抑制. 相似文献
10.
BOC(binary offset carrier)信号自相关函数存在多值性,BOC信号的捕获不能简单地移植GPS信号捕获算法。在分析经典并行码相位算法和BOC信号互相关特性基础上,仿真分析了并行码相位搜索算法对BOC信号进行捕获的有效性,并针对经典算法在低信噪比条件下捕获信号存在的不足,对经典算法进行了改进设计,并利用改进算法对多种BOC信号进行了仿真分析。结果表明,本文提出的改进捕获算法适用于BOC(pn,n)信号(p为整数),扩展了经典算法的适用范围,且与经典算法相比,改进捕获算法对所给定BOC信号能够改善捕获信噪比10dB,可显著提高接收机捕获灵敏度,对接收机BOC信号捕获算法设计具有重要意义。 相似文献
11.
针对传统导航信号捕获算法资源消耗大、多普勒分辨率低的问题,提出了一种基于预平均处理的变系数匹配滤波的快速捕获方法. 该方法将经过预平均处理后的导航中频信号和本地信号主码存入相应存储器,然后经变系数匹配滤波器完成相关累加,再经快速傅里叶变换(FFT)频率估计器完成数据的频谱分析,最后利用验证模块对FFT输出结果的最大值进行二次验证,完成捕获检测. 所提方法在达到相同积分时间的同时节省了50%硬件资源,能够提高捕获多普勒分辨率以提高转跟踪成功率,通过软件灵活配置可以实现多系统多频点全球卫星导航系统(GNSS)信号的兼容处理. 相似文献
12.
Sergey S. Pospelov Andrey L. Botchkovski Peter A. Krauss Stefan Berberich 《GPS Solutions》2000,4(1):48-55
Software Global Navigation Satellite Systems (GNSS) receivers are those that implement signal correlation processing not in
hardware, but in their software. The main problem for the development of real-time software (SW) multichannel GNSS receivers
is the tremendous amount of calculations to perform signal correlation.
The article reviews recent developments of SW GNSS receivers. The emphasis is made on the computationally effective correlation
processing algorithms and the optimization of processing allocation to the receiver's hardware (HW) and SW.
An architecture is suggested that implements the PRN signals despreading in a special HW preprocessor while all the other
correlation processing functions are still kept in SW. The combination of the most time-consuming processing in HW, and all
signal structure-dependent processing in SW, enables unique flexibility of sophisticated GNSS receiver design based on inexpensive
digital signal processors. ? 2000 John Wiley & Sons, Inc. 相似文献
13.
随着全球卫星导航系统(GNSS)及物联网技术的不断发展,GNSS多模接收机的应用越来越广泛．信号捕获作为接收机信号处理的第一步,其信号捕获能力的强弱直接影响着接收机的整体性能．本文针对多模接收机在捕获模块设计中遇到的快速傅里叶变换(FFT)算法兼容性差、运算时间长、资源占用大等问题,提出了一种优化方法.该方法通过加入原位运算、截位运算、模块重复利用、流水线结构等设计,以解决上述问题．经仿真验证,该方法在资源占用、运算时间、兼容性方面都有明显的改善． 相似文献
14.
Vinh T. Tran Nagaraj C. Shivaramaiah Thuan D. Nguyen Eamonn P. Glennon Andrew G. Dempster 《GPS Solutions》2018,22(1):24
The sampling frequency of a digitized intermediate frequency signal has a strong effect on the measurement accuracy of Global Navigation Satellite System (GNSS) receivers. The delay-locked loop tracking error is significant when the sampling frequency is an integer multiple of the code chipping rate, the so-called commensurate sampling frequency, and the number of distinct instantaneous residual code phases is low. This results in distortions of the correlation shape and discriminator functions that lead to a significant accuracy degradation. These effects are most pronounced when the sampling frequency is low. Notwithstanding, it is generally good for receivers to keep the sampling frequency to a minimum owing to the processing load and power consumption. It creates a challenge for existing GNSS signal processing techniques. Random, sine and sawtooth jitters have been found to mitigate these distortions considerably. A software algorithm and two hardware receiver implementations of these solutions are proposed. A register-based architecture can be directly applied to the conventional receiver architecture, while the increase in resource and power consumption is insignificant. A RAM-based design cannot only considerably minimize utilized resources but also slightly reduce the power consumption compared to the conventional architecture. 相似文献
15.
Indoor GNSS signals are typically received with poor signal-to-noise ratio, which impairs the acquisition stage of common
global positioning system (GPS) receivers. Extending the coherent integration time increases the acquisition sensitivity,
but the data-bit-rate limits the maximum achievable performance. Non-coherent processing also improves the detection performance,
but indoor signals require a large amount of accumulations resulting in significant squaring loss. Moreover, both strategies
have high computational complexity which fixes demanding requirements for stand alone mass-market terminals operating in real
time. A sensitivity–complexity trade-off is therefore mandatory. Assisted-GPS, which is included in 3GPP specifications, reduces the overall acquisition complexity and enhances sensitivity. In this paper
we describe a low-complexity-assisted data-wipe-off technique that enables the high-sensitivity acquisition of GPS signals.
The method is based on the acquisition of the strongest signal in order to obtain information that eases the acquisition of
the weaker ones. The analysis also addresses sources of sensitivity loss, such as Doppler effects and local oscillator inaccuracies.
A test campaign with real signals and integration times up to 2 s validates the method, demonstrating the effectiveness of
the proposed technique in indoor environments. 相似文献
16.
电离层闪烁是引起GNSS接收机性能降低甚至失锁的重要环境干扰因素。利用实测数据,比较分析了不同电离层闪烁活动强度下,不同GNSS系统（BD和GPS）接收机的定位性能。结果表明：电离层闪烁较弱时（S4〈0．3）,两种接收机均可以实现基本的定位功能;电离层闪烁较强（S4〉0.7）,且持续时间较长时,不同GNSS接收机将出现定位结果的抖动、跳变或失去定位能力;GNSS接收机应对电离层闪烁影响的能力与接收机设计相关。研究结果可作为抗闪烁接收机开发或闪烁影响分级的参考。 相似文献
17.
Chung-Liang Chang 《GPS Solutions》2016,20(2):201-213
Pre-processing traditional navigation signals in global navigation satellite system (GNSS) receivers includes the conversion of an analog-to-digital sample and acquisition following the basic principle of Nyquist sampling theory. This condition inevitably increases the system computation time and cost of a modern wideband receiver. In recent years, the compressive sensing (CS) approach has been proven to effectively reduce the number of measurement samples required for digital signal acquisition systems. This method gives new potential to this modern design. In this study, a modified compressive sensing algorithm for the acquisition of a GNSS signal that is contaminated by an interfering signal is presented. The proposed method attempts to combine CS demodulation and the subspace projecting method to enhance GNSS signal acquisition performance with interference present. First, the received signal is sub-sampled and aliased from a compressive sampling process. This operation maintains the restricted isometry property (RIP) condition of the second sampling process using a Toeplitz-structured sensing matrix, which replaces a conventional random sensing matrix. The matrix ensures that distances between desired signals on the set of sparse space are not influenced by the sampling process. Next, the interference is eliminated through the orthogonal feature between the interference signal and the desired signal using the subspace projecting method. This also preserves the RIP of the projecting matrix to ensure that the original structure of the linear projection of the signal is preserved. After this, an iterative least-square method is utilized to recover the correlator output from the reception samples taken by the CS demodulator. In addition, the signal detection performance in the presence of co-channel interference using a CS demodulator is analyzed and evaluated. Finally, the relationships between signal detection probability, compressive factor and signal bandwidth are also illustrated. Several numerical results are presented to verify the theory. 相似文献
18.
伪距多路径误差是影响GNSS导航定位精度的主要误差源之一。多路径误差与接收机周围环境有关,在实际应用中难以建立有效的多路径误差模型进行改正。对于多频GNSS接收机可以通过多频观测值组合估计伪距多路径,但该方法不适用于价格低廉的单频接收机,而导航中使用的大多数为单频接收机。因此,开展单频GNSS伪距多路径误差提取研究具有重要的工程应用价值。本文基于小波分析对单频GNSS接收机伪距多路径误差估计开展研究,首先验证了小波分析用于单频GNSS伪距多路径误差估计的可行性;其次,研究了采用不同的小波基和分解层次对多路径误差估计的影响;最后,研究了改正多路径误差对GNSS定位的影响。实验结果表明不同的小波基和分解层次对多路径误差提取效果没有明显的差别,但小波分解层次较低时定位误差分布相对更加集中,同时,经过多路径误差改正后在NEU3个方向RMS平均改善率达到20.4%、25.1%、16.4%。 相似文献
19.
M_DCB: Matlab code for estimating GNSS satellite and receiver differential code biases 总被引：6，自引：4，他引：2
Global navigation satellite systems (GNSS) have been widely used to monitor variations in the earth’s ionosphere by estimating total electron content (TEC) using dual-frequency observations. Differential code biases (DCBs) are one of the important error sources in estimating precise TEC from GNSS data. The International GNSS Service (IGS) Analysis Centers have routinely provided DCB estimates for GNSS satellites and IGS ground receivers, but the DCBs for regional and local network receivers are not provided. Furthermore, the DCB values of GNSS satellites or receivers are assumed to be constant over 1?day or 1?month, which is not always the case. We describe Matlab code to estimate GNSS satellite and receiver DCBs for time intervals from hours to days; the software is called M_DCB. The DCBs of GNSS satellites and ground receivers are tested and evaluated using data from the IGS GNSS network. The estimates from M_DCB show good agreement with the IGS Analysis Centers with a mean difference of less than 0.7?ns and an RMS of less than 0.4?ns, even for a single station DCB estimate. 相似文献
20.
Software receivers have had a discernable impact on the GNSS research community. Often such receivers are implemented in a compiled programming language, such as C or C++. A software receiver must emulate the digital signal processing (DSP) algorithms executed on dedicated hardware in a traditional receiver. The DSP algorithms, most notably correlation, have a high computational cost; this burden precludes many software receivers from running in real time. However, the computational cost can be lessened by utilizing single instruction multiple data (SIMD) operations found on modern ×86 processors. The following demonstrates how C/C++ compatible code can be written to directly utilize the SIMD instructions. First, an analysis is carried out to demonstrate why real time operation is not possible when using traditional C/C++ code is carried out. Secondly a tutorial outlines how to write and insert ×86 assembly, with SIMD operations, into C/C++ code. Performance gains achieved via SIMD operations are then demonstrated, and pseudo code outlines how SIMD operations can be employed to perform correlation. Finally, a C/C++ compatible SIMD enabled arithmetic library is added to the GPS Toolbox for use in software receivers. 相似文献