小波变换在S模式二次雷达信号分析处理中的应用

为提高二次雷达(Secondary Surveillance Radar,SSR)信号分析处理能力,针对傅里叶变换在时频域分析的局限性,利用小波信号奇异性检测特点,通过对S模式询问、应答信号进行小波分解,计算第一层高频系数,得到信号脉冲持续时间,实现了信号报头检测,并比较高频系数模极大值,提取出信号调制信息,实现了基于小波变换的二进制差分相移键控(DPSK)和二进制振幅键控(ASK)解调,验证了小波变换技术分析处理二次雷达信号的可行性.     

多进制chirp-rate键控调制及分数傅里叶变换法解调

基于chirp信号chirp-rate和中心频率参数与其分数傅里叶变换特性之间的明确关系,提出了一种采用分数傅里叶变换法解调的多进制chirp-rote键控调制方式,该方式具有恒包络,并具有优于MPSK的误码性能.进而,将多进制chirp-rate键控与MFSK联合使用,通过参数调整,能够获得误码率性能与频谱效率间的折中.     

用离散傅里叶变换方法实现n路移频键控调制解调

本文提出一种适用于卫星通信的、用离散傅里叶变换(DFT)方法实现n路码元同速的移频键控(FSK)调制解调。详细讨论了这种调制解调原理、实现的基本条件与方法,分析了干扰误差及抗干扰能力,采用这种方法可以有效地利用带宽、增加通信容量和避免制作带通滤波器的困难。     

快速傅里叶变换在OFDM系统中的应用

本文简要分析了未来OFDM数字通信系统的基本模型和可能采用的信号调制与解调的方法,在此基础上详细地解析了数据序列经过快速傅里叶逆变换 /快速傅里叶变换 (IFFT/FFT)后的输出结果与M进制数字调制解调之间的联系,并给出了能够实现OFDM调制解调的合适的IFFT/FFT算法,实际仿真结果表明快速傅里叶变换及反变换在未来OFDM技术中具有一定的实用价值。     

一种基于DSTFT解调FSK信号的改进方法

提出了一种基于离散短时傅里叶变换（DSTFT）来实现FSK信号数字解调的方法，给出了解调原理和码元同步算法，仿真表明效果良好。     

基于LFM-BPSK 信号的距离像成像方法

针对雷达通信一体化系统中雷达成像与通信共享信号的设计,分析了常见的一体化信号设计模式。首先,利用线性调频信号相位调制传递通信信息,设计了一种基于线性调频—二进制相移键控(LFM-BPSK)调制的雷达通信一体化信号,并给出了运动扩展目标的回波信号表达式;其次,通过计算单脉冲回波信号采样的逆离散傅里叶变换或离散傅里叶变换,提出了基于一体化信号合成高分辨距离像方法;然后,依据相位因子对傅里叶变换的影响,分析了多普勒效应对一体化信号合成距离像的影响;最后,对一体化信号的雷达成像性能进行了仿真计算。     

基于声表面波延迟线的相位解调器设计

该文提出了一种基于声表面波延迟线的相位解调器,其原理是利用声表面波延迟线将调相信号转换为调幅信号,并采用“延迟相加”的方法进行解调。该延迟线实现了频率2.695～3.000 GHz内1μs的延迟时间,解调器可以实现调制速率为500 kHz和1 MHz的二进制相移键控(BPSK)调制信号的解调。     

基于DDS的广电FSK调制解调系统

一 背景 FSK是载波频率随数字信号而变化,利用基带数字信号离散取值特点去键控载波频率以传递信息的一种数字调制技术。最常见的是用两个频率承载二进制1和0的双频FSK系统。本设计就是基于这种2FSK的调制解调技术．FSK是最为常见的一种调制方式,     

基于神经网络的ASK解调器及性能研究

文中介绍了一种基于ELMAN型神经网络的振幅移位键控（ASK）信号解调器,并研究了该解调器的相关性能。与传统解调器相比,它有一些很重要的特点：第一,神经网络算法用于解调处理,其抗干扰性能优于传统方法;第二,神经网络解调器有和传统解调器相似的处理单元,但在神经网络中,这些功能被整合在多个神经元中,无需对每个处理单元和功能进行单独设计,这些处理功能都是在其学习过程中自己获得的;第三,解调系统为并行结构,所以处理速度比传统速度更快。由MATLAB的仿真结果可以看到,该解调器有效且性能优良。     

卫星通信中连续相位QPSK调制的带宽效率分析

连续相位调制(CPM)是一种带宽效率很高的调制技术,适用于卫星非线性信道。在将正交相移键控(QPSK)表示成CPM的基础上,提出了一种基于离散傅里叶变换(DFT)的谱密度计算公式。利用MATLAB的快速傅里叶变换(FFT)运算仿真了连续相位QPSK(CPQPSK)的功率谱,结果表明CPQPSK较QPSK具有更高的带宽效率。     

Research on Properties of Devices for Shaping and Processing of Signals Based on Amplitude Modulation of Many Components

Devices for shaping and processing of signals based on known varieties of digital amplitude-phase modulation are considered. Their disadvantages are exposed during realization of modulation and demodulation of the signals that are characterized by non-rectangular signal constellations. There are explored properties of devices for shaping and processing of signals based on a new variety of signal modulation, namely amplitude modulation of many components (AMMC). The results of carried out researches show that advantages of proposed AMMC modulator are simplification of phase modulated or amplitude-phase modulated signal shaping, in particular AMMC signal shaping, and improve of modulator internal interference protection. Advantages of AMMC demodulator are simplification of phase modulated or amplitude-phase modulated signal processing, in particularAMMC signal processing, and improve of demodulator internal interference and zero drift protection at its practical realization. The proposed AMMC modulator and demodulator can be applied for shaping and processing of signals based on known and new varieties of amplitude-phase modulation.     

一种FSK反正切差分解调方法

针对频移键控在通信系统应用中其调制解调技术在一定程度上直接影响通信系统的性能,提出了一种FSK数字解调方法,称作反正切差分解调.该方法基于正交反正切算法,正交信号直接相除消除了幅度调制成分.新的方法适用于窄带和宽带的FSK信号并适合于数字接收机.仿真结果表明,该技术能有效解调FSK信号,并适合于多种制式的FSK信号.     

Distortion in the Frequency Demodulator Using Feedback

The response of a frequency demodulator using feedback (FMFB) to a frequency modulated signal is analyzed. Canonical equations of operation are obtained. Harmonic distortion is calculated for the case of a sinusoidal modulating signal. Intermodulation distortion is calculated assuming a noise-like modulation. Design curves are presented. The special case of harmonic and intermodulation distortion in a discriminator is also presented. It is shown that the results obtained in this paper by treating the discriminator as a degenerate FMFB compare favorably with those obtained by other authors. However, the results presented here do not require digital computation.     

A 75-mW 128-MHz DS-CDMA baseband demodulator for high-speedwireless applications [LANs]

A DS-CDMA demodulator uses analog sampled-data signal processing to achieve a 75-mW power dissipation and a 128-MS/s processing rate in a 1.2-μm double-metal double-poly CMOS process. To demodulate the signal, a low-power passive correlation technique is introduced that eliminates the integrating opamp with its associated power and settling time overhead. In a prototype demodulator, six 64-chip correlators recover the 2-Mb/s data stream from the doubly modulated [pseudorandom noise (PN) and Walsh] quadrature input signal. An on-chip 10-b pipelined ADC sampling at 8 MS/s follows the analog correlation to permit digital implementation of the acquisition and tracking algorithms     

Suspended sediment and dye concentration measurements using a digital technique

This paper presents a new digital technique for measuring the concentration of the suspended sediment and dye materials in fluids. The method is based on the measurement of the attenuation of a sinusoidally modulated light beam penetrating a small sample volume of the fluid. The method of direct digital synthesis is used to produce a sine wave in the input stage, giving a high stability in the amplitude and frequency of the light-beam modulating waveform. This sinusoidal waveform drives six infrared or colour light emitting diodes, depending on the material to be detected. The system facilitates optical fibres to transfer the optical signal to and from the sampling point. The collected light is converted through photodiodes to an attenuated sinusoidal electrical signal. In contrast to the conventional optical sediment detection devices, here synchronous amplitude demodulation is used instead of conventional analogue low-pass filters. Therefore, the information concerning the amplitude is pure and a very high signal to noise ratio can be achieved. The use of a sinusoidal waveform instead of rectangular pulses having high harmonic content results in less influence on the receiver from higher frequencies. The above improvements resulted in a high resolution instrument.     

A Discrete‐Amplitude Pulse Width Modulation for a High‐Efficiency Linear Power Amplifier

A new discrete‐amplitude pulse width modulation (DAPWM) scheme for a high‐efficiency linear power amplifier is proposed. A radio frequency (RF) input signal is divided into an envelope and a phase modulated carrier. The low‐frequency envelope is modulated so that it can be represented by a pulse whose area is proportional to its amplitude. The modulated pulse has at least two different pulse amplitude levels in order that the duty ratios of the pulse are kept large for small input. Then, an RF pulse train is generated by mixing the modulated envelope with the phase modulated carrier. The RF pulse train is amplified by a switching‐mode power amplifier, and the original RF input signal is restored by a band pass filter. Because duty ratios of the RF pulse train are kept large in spite of a small input envelope, the DAPWM technique can reduce loss from harmonic components. Furthermore, it reduces filtering efforts required to suppress harmonic components. Simulations show that the overall efficiency of the pulsed power amplifier with DAPWM is about 60.3% for a mobile WiMax signal. This is approximately a 73% increase compared to a pulsed power amplifier with PWM.     

一种用于信号分析的数字正交解调电路设计

阐述了数字正交解调的原理以及与传统模拟正交解调相比所体现出的优越性。详细介绍了一种用于信号分析的数字正交解调电路设计方案和工作原理,并结合信号分析类仪器的特点和要求说明电路的硬件和软件设计方法。通过对数字滤波环节的仿真和在具体应用中所得到的实验结果说明设计电路的优越性。     

基于FPGA的超声信号数字正交解调器

利用FPGA设计用于检测微弱超声信号的数字正交解调器.将经高速A/D采样的数字信号分为两路正交的基带信号,通过数字混频、低通滤波和数据抽取,最后从两路正交基带信号中提取出超声回波信号的幅度信息.本文对数字正交解调进行了理论分析,并分别利用FPGA中的内建RAM实现数控振荡器,内嵌乘法器实现数字混频,IP核实现低通滤波器,及宏模块实现数学运算.对玻璃杯的扫描成像实验结果,证明了设计的正确性.     

2比特移相电路非理想时间调制的谐波特性研究

围绕宽带高频高效率时间调制阵列天线,研究了基于2比特移相电路的非理想时间调制的谐波特性.首先建立梯形波和升余弦波时间调制的数学理论模型,以此分析射频开关调制波形的变化对2比特移相电路输出信号各次谐波分量的能量占比、幅度、相位的影响,再进一步分析2比特移相电路各种状态的幅度和相位偏差对输出信号各次谐波分量的能量占比、幅度、相位的影响.该研究可为基于2比特移相电路的时间调制阵列提供更为精确的幅度和相位调控技术.