一种北斗三号RDSS性能实时监测的实现方法

随着北斗三号系统应用的逐步推广,北斗RDSS功能在边防、气象、交通、航空和应急搜救等行业中应用越来越广泛,因此北斗RDSS性能监测是推动北斗RDSS服务应用的重要途径。设计了一种北斗三号RDSS性能实时监测的系统实现方案,系统具备安全性、高可靠性和易扩展性,满足数据采集、接收、存储、处理和管理监控等各个功能的基础支撑需求;针对RDSS的性能评价内容进行了设计,包含通信内容查询、接收信号类型、波束数量和波束功率、通信成功率、定位精度及通信时延等功能指标。最后,通过在对天环境条件下的实际测试验证,分析了测试结果数据,验证了方案的可行性。提出的方案具备RDSS性能监测实时性强、连续监测、及时预警和远程推送的特点,可以通过网络向相关用户推送相关信息,使用户能够方便快捷地掌握RDSS使用性能,为用户RDSS应用提供保障。     

S频段GNSS信号兼容性及性能分析

随着全球导航卫星系统（GNSS）的建设和发展,L频段的信号越来越拥挤．扩展新的频率资源迫在眉睫。S频段（2483．5-2500MHz）与其他频段相比,更易于实现移动通信和导航定位服务的融合．S频段和L频段的复用能够提高接收机的电离层校正能力。从而提高卫星导航系统的定位授时能力：S频段和L频段的联合定位更加有益于整周模糊度的求解．可以提高精密单点定位的鲁棒性和精度。最小频移键控（MSK）调制方式具有包络恒定、相位连续、功率谱旁瓣衰减快等特点,并且实现简单．易与二进制偏移载波（BOC）调制方式相结合,非常适用于带宽窄且兼容性要求高的S频段。本文评估了北斗二号在S频段采用MSK-BOC调制信号时与S频段中的北斗一号、Globalstar系统之间的干扰．分析了其码跟踪误差和多径误差包络,论证了其在兼容性和跟踪精度方面的优越性．研究结果对我国北斗二号S频段信号体制设计和工程实现具有定的参考价值。     

参数调制多载波雷达通信共享信号设计

雷达通信一体化是减少电子平台体积与电磁干扰的一种有效途径,而共享信号的研究是实现雷达通信一体化的关键技术。该文提出了一种基于Chirp信号的多载波雷达通信共享信号,其主载波采用唯一Chirp信号实现雷达功能,副载波通过改变调频率和初始频率参数组合的Chirp信号调制通信信息。分析了共享信号的模糊函数以及参数设计方法,并对其处理过程及系统性能进行了研究。仿真结果表明,该信号具有较低误码率和高稳健性特性,使用该共享信号可在微量降低雷达性能的前提下实现通信数据的传输。      

AltBOC恒包络调制及Matlab仿真

Alt BOC(Alternate Binary Offset Carrier)首先在伽利略E5频段上被提出,该调制信号具有频谱利用率高,跟踪精度好及抗多径等性能,目前北斗导航系统也计划采用这种调制信号。文章首先介绍了Alt BOC的基本原理,然后详细阐释了恒包络Alt BOC调制的实现方法,特别是用查表法来方便地实现Alt BOC恒包络调制,最后在Matlab中对查表法进行了仿真。     

“北斗”B2频段导航信号伪码跟踪性能分析

与传统卫星导航信号体制不同,新一代“北斗”B2频段导航信号采用了交替二进制偏移载波调制（AltBOC）体制,因此伪码跟踪性能也与传统信号体制有较大差异。首先介绍了AltBOC调制信号原理及特点,然后根据码跟踪精度理论比较了新型调制信号与传统信号体制的性能差异,分析了不同鉴相器时B2频段信号的码跟踪误差,并对不同相关器间隔、环路带宽、前端带宽、载噪比环境条件下的伪码跟踪误差进行了仿真分析。仿真结果表明,提高信号载噪比、射频前端带宽或减小相关器间隔、环路带宽均能减小码跟踪误差。研究结果对新一代“北斗”导航信号新体制性能的评估以及“北斗”导航接收机的系统设计具有一定指导意义。     

一种成像雷达的通信一体化信号设计与分析

雷达与通信系统一体化可以最大限度地利用雷达设备, 使雷达的优良性能为通信服务.根据信号共享的原则, 在保持成像雷达和通信各自功能实现的前提下, 设计了一种基于随机频率步进调制的成像雷达通信一体化信号.该信号的设计方法是对发送的通信数据进行随机编码处理, 然后将其调制到雷达载波的频点上发送出去, 实现通信功能; 而引入压缩感知理论后, 采用这种信号仍能获得高分辨率的雷达图像, 在一定功能上实现了成像雷达和通信的一体化.     

一种基于OFDM-chirp的雷达通信一体化波形设计与处理方法

雷达通信一体化波形设计是近年来的研究热点.有学者提出利用正交频分复用(OFDM)信号的奇偶载波分别调制雷达与通信功能来实现一体化.但OFDM通信系统一般采用循环前缀(CP)来避免多径效应带来的载波间干扰(ICI)和符号间干扰(ISI),这会降低能量利用率,并会形成虚假目标,影响雷达性能;此外,传统的OFDM一体化信号对...     

基于频率调制的多载波Chirp信号雷达通信一体化研究

为了减少电子战平台的体积和电磁干扰,一种有效的途径就是实现雷达与通信的一体化.该文针对雷达通信一体化信号设计中存在的不兼容和互干扰问题,根据信号能量共享的原则,提出了基于频分准正交多载波Chirp 信号的雷达通信一体化波形及其相应的系统实现方法.并采用宽带模糊函数对多载波一体化信号特性进行了详细分析,进一步研究了一体化信号的处理过程以及其系统性能.在均衡子载波准正交性和通信频谱效率下,通过理论分析和仿真结果表明在多载波频谱重叠率为20％的情况下,一体化信号能够满足雷达的常规探测,并且具有较低的误码特性.     

一种获取北斗卫星信号新方法的研究

北斗导航卫星系统作为兼容、独立、开放和全球的导航系统,被设计用于执行导航和控制任务。该系统在现实环境中的成功运行必须克服众多挑战,其中主要是提高北斗卫星信号的捕获成功率。旨在减轻调制码处理方式带来的混叠伪像,提高北斗定位接收机定位性能,提高捕获成功率,文中提出了一种使用信号平方的捕获卫星信号的方法。实验结果表明,相对于传统方法,该方法具有更好的北斗信号捕获性能。     

一种四进制连续相位调制新方法

为简化连续相位调制信号的相干解调,提出了一种四进制连续相位调制方法。在发送端,信号调制器根据发送的前后两组比特信息从一个预先设计的基带信号集合中选择对应的基带信号作为调制信号。该调制方法使信息码元由基带信号某一时刻的绝对相位值表示,当完成相位和载波同步后,在接收端其接收处理和传统QPSK信号一致,可以直接使用IQ路的采样值解调信息比特。仿真表明,调制信号的相干解调误比特性能与QPSK信号的相干解调相同。由于调制信号具有准恒包络和连续相位的特点,更适合应用于使用非线性功放的功率受限通信系统中。     

A New Transceiver Scheme for OFDMA System Based on Discrete Cosine Transform and Phase Modulation

A high peak-to-average power ratio of the transmit signal is a major drawback of multicarrier transmissions, such as orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiple access (OFDMA). An alternative approach to mitigate the peak-to-average power ratio (PAPR) problem is based on signal transformation using phase modulation (PM). A phase modulation based systems have the advantage of constant envelope (CE) signals and the ability to improve the diversity of multipath channels. In this paper, a different implementation of discrete Fourier transform DFT-OFDMA system which is based on discrete cosine transform (DCT) is proposed. The DCT-OFDMA system is then used to develop a new transceiver system called DCT-OFDMA-PM which refers to discrete cosine OFDMA with phase modulation. The PM input signal to be modulated must be real which can be produced using DCT-OFDMA with pulse amplitude modulation (M-PAM). The new system involves a signal transformation prior to amplification. This gives the advantage of CE (i.e. 0 dB PAPR). The proposed system is implemented with frequency domain equalization (FDE) to obtain high diversity gains over the frequency multipath channel. Simulation the PM-based systems with multipath fading can outperform that with single path fading.     

Multicarrier constant envelope OFDM signal design for radar applications

Orthogonal frequency division multiplexing (OFDM) radar signals have been introduced for high range resolution radars. These signals have prominent properties such as favorable ambiguity function, high bandwidth efficiency, and possibility of use in dual mode radar/communication systems. But the large amplitude fluctuations of the OFDM signal make it susceptible to system nonlinearities. To alleviate this problem, constant envelope OFDM (CE-OFDM) signal has been introduced which combines orthogonal frequency division multiplexing and phase modulation or frequency modulation. Although several works have been reported on OFDM radar signal design, there is no a systematic approach for designing CE-OFDM signals for radar applications. In this paper we will focus on CE-OFDM signal design for radar applications. Two different methods for designing a CE-OFDM signal with favorable ambiguity functions are introduced. The first one is based on modulating a complementary set of sequences on different sub-carriers while the second is based on using a proper single carrier coded signal and then extracting its most similar multicarrier OFDM or CE-OFDM coded signal.     

Error floors in the satellite and land mobile channels

In a satellite mobile channel (SMC) and land mobile channel (LMC) because of fading and nonlinear power amplifiers, constant envelope modulation and noncoherent detection methods may outperform other schemes. It is shown how to compute the error floor for four noncoherent digital communication systems in satellite and land mobile channels. Differential phase shift keying (DPSK) with differential phase detection (DPD) or frequency shift keying (FSK) with DPD, limiter discriminator integrator detection. (LDID), or limiter discriminator detection (LDD) are studied. The error floor is the residual error probability when SNR is infinity, i.e. the error probability in the system is limited by the error floor. The error floor is computed as a function of Doppler frequency, modulation index, and ratio of powers in the specular and diffuse signal components for DPSK-DPD, FSK-DPD, FSK-LDID and FSD-LDD systems     

连续相位调制信号的二阶循环平稳特性分析

连续相位调制(CPM)信号以其恒包络和优良的频谱特性在现代卫星通信和移动通信中越来越受到人们的重视,然而这一大类调制信号的循环平稳特性却较少有人关注。该文根据连续相位调制信号在不同调制指数下的基带循环谱,推导了其相应带通循环谱的表达式, 并对这些表达式的详细分析,得出了不同调制指数情况下循环频率与载频、码元宽度和峰值频偏之间的关系式。仿真实验证明这些结论是正确的。     

低频信道调制方案研究

低频信道是功率受限型信道。低频信道具有噪声大、频带窄、辐射效率低的特点,因此,低频通信的实施难度极大。对比分析了在低频信道条件下的几种编码调制方式的性能优劣,进而提出了一种将卷积编码和CPFSK相结合的解决方案。该方案具有功率利用率高、频率利用率高、相位连续、包络恒定、复杂度低等优点。从理论分析和计算机仿真结果可以看出,该低频信道编码调制方案经济可行、性能良好。     

Complete alternative binary offset carrier modulated signals (AltBOC signals) with variable and constant envelopes for new-generation satellite radio navigation systems

The formation and structure of four- and eight-component complete alternative binary offset carrier modulated signals (AltBOC signals) for new-generation satellite radio navigation systems (SRNSs) (in particular, the Galileo and BeiDou-2 SRNSs) are considered. A four-component complete AltBOC signal has a time-variable envelope, while the envelope of an eight-component complete AltBOC signal is constant. The envelopes and phases of such AltBOC signals are analyzed for various values of the multiplicity coefficients of meander pulses. The combination components of an eight-component complete AltBOC signal are plotted, and the features of these components that ensure the time constancy of the envelope are revealed. A classification of AltBOC signals is proposed. Practical characteristics are analyzed on the basis of the AltBOC (15, 10) modulation, which is typical of the Galileo and Compass SRNSs.     

Multifrequency minimum shift keying

A new modulation scheme that produces a constant envelope continuous phase signal set with a compact power spectrum and power efficiency better than that of MSK is proposed. The scheme can be implemented by quadrature-carrier multiplexing of two frequency/phase modulated signals of the type NFSK/2PSK, both with the same frequency in each transmission interval, and with sinusoidal symbol shapes. The generated signal can be viewed in each transmission interval as an MSK signal at one of the N frequencies and is referred to as multifrequency minimum shift keying (MF MSK). Modulation, demodulation, and synchronization circuits are described, and the spectral properties and power efficiency on the AWGN channel are analyzed. Combining a number of attractive attributes such as constant envelope, excellent spectral properties, high power efficiency, and self-synchronization capability, the proposed modulation format lends itself to a variety of applications, one of them being the digital satellite link     

基于现代GNSS信号的通信综合实验设计

本文针对通信综合实验教学,设计了一种以现代卫星导航信号为研究对象的综合实验项目。该项目依托通信主体理论进行模块化设计,将伪随机序列、新型调制方法、恒包络复用技术和信道编码等核心概念通过现代GNSS信号呈现,以前沿技术为导向,培养学生工程实践能力。实践表明,该实验能够加强学生对基础理论的学习兴趣,增长运用理论知识解决实际问题的能力。     

Method for superimposing data on amplitude-modulated signals

The principles of a new modulation scheme are described which permit an additional data channel to be superimposed on conventional DSBAM signals without increasing band-width or envelope distortion. This scheme, named zero synchronous frequency modulation (ZSFM), requires additional signal processing and provision for combined AM/FM at the transmitter. At the receiver, the data signal is detected by a simple frequency demodulator, while envelope detection of the AM signal is performed in the usual way.     

基于可见光通信的停车场泊车自动导航系统

为满足车辆定位需求并实现高效率停车场泊车导航,设计基于可见光通信的停车场泊车自动导航系统,系统的车位信息监测模块通过结合泊车位上方LED照明装置和车位地面的光敏电阻形成光电检测装置,获取停车场车位状态信息后,经STM32单片机产生频率差异显著方波信号;可见光信号调制模块依据可见光通信原理,将方波信号经信号调制电路转换成电信号,驱动停车位的LED灯光源,传输光信号至定位导航模块;定位导航模块利用内置摄像头接收可见光定位信号,经信号解析、定位等步骤获取可见光信号来源位置信息,实现停车场泊车自动导航。实验结果表明,该系统可有效满足车辆定位需求,车辆定位误差控制在0.20 m范围内,且泊车导航所需时间较短,具备较高泊车导航效率。