信标信号频谱在接收机跟踪性能分析上的应用

接收机锁定卫星信标后,经过二次或三次变频将C频段信标转变为70 MHz中频,然后通过解调单元从中频中提取误差信号。通过分析比较信标信号、L频段频率、70 MHz中频信号频谱使跟踪系统的性能指标层次化,从信标频谱中提取有用信息,全面判断数字接收机跟踪性能,对单脉冲跟踪体制下的接收机故障排查具有一定的指导意义。     

衰落信道下基于接收机信标感知的频谱共享

理想的主、次系统频谱共享应尽量使次级用户发射机与主用户接收机处于互为对方的保护边界和干扰边界的临界状态。本文基于此临界状态对信标感知灵敏度和次级用户发射功率的要求,通过分析信道衰落和双向信道非对称性引起的临界干扰概率,首次针对基于接收机信标感知的频谱共享方法,给出了衰落信道下满足主用户干扰约束的次级用户发射功率约束机制。针对单个工作频段存在多个主用户接收机的（广播）场景,以距次级用户发射机最近的主用户接收机为干扰保护目标,通过分析信标的多个衰落副本的累积作用对信标感知的影响,进一步给出了这种场景下的次级用户发射功率约束与主用户临界干扰概率的关系。      

PD雷达抗距离-速度同步拖引干扰的频谱识别法

分析了存在距离-速度同步拖引干扰时的信号频谱特征,研究了一种脉冲多普勒(PD)雷达抗距离-速度同步拖引干扰的方法。该方法在高速可编程DSP芯片所构成的距离-速度跟踪系统中,通过对接收机AGC电压和对信号的频谱分析,实现对距离-速度同步欺骗干扰的辨别和对抗。     

转发欺骗干扰对卫星导航接收机载波环的影响研究

本文研究了转发欺骗干扰对卫星导航接收机载波跟踪环的影响。推导出在存在转发欺骗条件下卫星导航接收机载波跟踪环输出的相位误差公式，分析了不同强度的转发欺骗干扰对卫星导航接收机跟踪环路的作用，得出了使卫星导航接收机跟踪环路失锁转发欺骗干扰所需的最小功率强度。通过试验验证了本文分析结论的正确性。     

宽带接收和高精度被动跟踪伺服跟踪系统

为了对星载合成孔径雷达进行侦察和跟踪，在雷达侦察设备中使用了压缩接收机。通过介绍压缩接收机的基本原理，推导出采用脉压接收机后雷达侦察接收机的信噪比将改善D倍，因而灵敏度也改善了1／D倍，并且推出跟踪误差电压与目标偏角θ的数学模型。同时，分析了雷达侦察接收机灵敏度提高和角跟踪死区减小l／√D倍的机理，得出在雷达侦察中采用压缩接收机可提高侦察距离和提高角跟踪精度。     

数据字长对GPS信号捕获跟踪性能影响分析

数据字长对GPS接收机性能和硬件资源消耗有着重要影响,以循环相关捕获算法为例,利用线性方法建立GPS接收机各部分量化误差模型,讨论算法实现中各模块数据字长对信噪比的影响,给出了误差表达式,确定了系统性能与资源消耗的最优结合点.软件接收机仿真测试结果表明,该方法分析结果正确有效,能够为捕获跟踪电路的FPGA实现提供工程设计参考.     

电力系统谐波检测全相位频谱分析研究

为了解决电力系统谐波检测中存在的检测精度低的问题,提出一种改进的全相位时移相位差频谱校正算法,消除了相位值对采样中心样点的依赖性。将该算法用于电网含有谐波以及间谐波的测量分析,结果表明该算法在中高信噪比情况下相位误差小于1°,具有估计精度高且稳定性好的特点。     

一种双通道跟踪接收机的实现方法

针对射电星、高速调制等宽频谱信源的天线跟踪问题,提出了一种双通道跟踪接收机的实现方法。该方法采用宽频谱中的一段频谱进行和通道与差通道的双通道传输、变频和放大,进行模拟数字转换后在数字信号中完成跟踪角误差的提取与归一化,并在数字上完成高精度的相位校正。仿真结果表明,该方法可适用于各种类型信源的跟踪角误差的解调。     

对GPS M码信号的噪声调频干扰参数优化研究

GPS M码信号采用二进制偏移载波(BOC)调制,实现了频谱分离,带宽更大,原有针对C/A码、P码的干扰参数设置无法对其进行有效干扰。文中采用可形成较大带宽的噪声调频干扰样式,结合GPS软件接收机码跟踪环路工作原理,以接收机码跟踪误差为干扰评价指标,对特定干信比下的干扰频偏和干扰带宽进行参数优化,通过综合比较得出针对M码信号的噪声调频干扰高效干扰参数设置。     

GNSS智能相干跟踪欺骗干扰方法及效能分析研究

针对叙利亚战场和美军伊朗战场发生的多起无人机被欺骗干扰诱捕事件,本文分析说明了 GNSS 生成式和转发式两种不同欺骗干扰的方法、实现机理及效能,提出智能相干跟踪欺骗方法。通过智能相干跟踪欺骗干扰机理及其对卫星导航用户接收机的影响分析,研究了该欺骗干扰对用户接收机的智能跟踪和相关牵引效果。最后完成了仿真和实际场景模拟试验,验证了该欺骗干扰的诱骗能力、破坏性及隐蔽性。     

Using frequency hopping spread spectrum technique to combatmultipath interference in a multiaccessing environment

The purpose of this paper is to conduct performance analysis for a frequency-hopped spread spectrum multiaccess network which is subject to the threat of multipath interference. Baseband modulation is done through frequency shift keying and signal detection is accomplished by a noncoherent type receiver. The quality of a signal is affected by the channel noise, multiuser interference, and multipath interference. Performance analysis is conducted on the basis of bit error rate. Due to the sophistication of the system exact analysis is not feasible. The accuracy of approximation is checked against simulations. One major discovery Is that when signal-to-noise ratio is low, multipath interference on the contrary may help to enhance the quality of the signal. Another discovery is that when signal-to-noise ratio is high enough, multipath/multiuser interference becomes the bottleneck of performance. The effect of channel noise can be eliminated by maintaining a large signal-to-noise ratio while spread spectrum technique is employed to reduce the effect of multipath/multiuser interference     

四象限精跟踪光轴检测模型与误差分析

研究了四象限精跟踪光轴检测模型,推导出大气环境下系统固有分辨精度与细分精度的关系,在此基础上指出提升检测系统固有分辨率的方法,有效降低光强闪烁影响;同时,讨论了大气湍流误差、背景光学误差、电子干扰误差产生的原因以及与系统信噪比之间的关系,针对不同误差给出相应补偿办法并进行仿真。仿真结果表明,背景光误差与信标光信噪比、光轴偏差量直接相关;减小系统滤波器带宽,可抑制电子干扰误差;弱大气湍流条件下,增大接收光学口径,能有效抑制信号衰落。     

GPS射频干扰浅析

论述信号噪声比和信号噪声密度比的概念，分析了射频干扰(RFI)对GPS接收的影响，最后说明了直接检测RFI的方法以及RFI源的定位。     

Spectrum efficiency of a frequency-hopped MFSK spread spectrum mobile radio system

The spectrum efficiency of a frequency-hopped multilevel frequency-shift keying (FH-MFSK) spread spectrum modulation technique proposed for use in mobile radio systems is evaluated. The analysis assumes randomly chosen address vectors, a perfect synchronization at the receiver, and noncoherent detection. With perfect transmission where the only degradation is due to mutual interference, the efficiency is 0.262, 0.295, and 0.345 at an average bit error rate of 10^-3for 1.64, 3.41, and 20 MHz bandwidth. However, with transmission impairments consisting of additive white Gaussian noise and frequency selective Rayleigh fading, which characterize the mobile radio channel, the efficiency depends on the average signal-to-noise ratio (SNR), and on the average bit error rate.     

Interference suppression for DS/CDMA

A direct-sequence spread spectrum (DS/SS) receiver for suppressing multiple-access interference in direct-sequence code-division multiple-access (DS/CDMA) communication systems is introduced. The proposed receiver does not require knowledge of other users' spreading codes, timing, or phase information. Moreover, the receiver allows the number of taps to be chosen independently of the processing gain and, hence, is easily applicable to CDMA systems employing either a small or a large processing gain. Performance analysis, including average probability of error and signal-to-noise ratio, is provided, and results are presented for systems varying from lightly loaded (for example, eight user/255 chip) to heavily loaded (for example, 50 user/200 chip). Performance results indicate that the proposed receiver outperforms the linear correlation receiver and, in many cases, it does so by a considerable margin     

干扰环境下BPSK接收机跟踪--检测联合性能分析

本文分析了干扰环境中噪声和干扰对接收机的跟踪性能和检测性能的联合影响。主要分析了存在噪声和带内单频干扰情况下BPSK接收机的误码率性能和Costas环的跟踪性能。     

Interference cancellation in GPS receiver using noise subspace tracking algorithm

In this paper, we address the problem of interference cancellation in global positioning system (GPS) receiver using a two-step approach: subspace projection technique and maximum signal-to-noise ratio (MSNR) beamforming. The interference signals can be effectively suppressed by projecting the received signal on the noise subspace. Here noise subspace tracking algorithm is employed to estimate the noise subspace directly. We then apply a beamformer to maximize the signal-to-noise ratio of the interference-free signal. Simulation results show that our approach can effectively eliminate the strong interference and enhance the performance of the GPS receiver.     

Joint design of precoder and receiver in cognitive radio networks using an MSE criterion

We consider a single-user multiple-input multiple output (MIMO) transmission from secondary base station (SBS) in cognitive radio network where there is one primary user to which spectrum is licensed. It is assumed that coexistence of secondary network is allowed if interference power from the secondary network measured at primary user (PU) can be kept below a given threshold. In this paper, joint design problem of precoder and receiver is treated using mean-squared error (MSE) criterion between transmitted signal and its estimate at the receiver. Due to constraint on interference power measured at the PU, it is not possible to find an optimal solution in closed form. Therefore, a suboptimal solution with low complexity is proposed in closed form. Simulation results show that the MSE and bit error rate (BER) performances of the proposed scheme are 1.5-4.0 dB better than those of a conventional capacity-maximization scheme when the received signal-to-noise ratio (SNR) is high, and they converge to their lower bounds, i.e., those of an MSE-based scheme without considering the PU interference constraint, as the received SNR increases.