交叉相位调制所致啁啾的研究

推出了存在光纤损耗时交叉相位调制效应所产生的啁啾的解析表达式 .利用计算机模拟了啁啾演变过程 ,并分析了啁啾与光纤损耗系数、群速度失配的关系 .结果表明 ,啁啾受光纤损耗影响很小 ;受群速度失配影响较大 ;啁啾经过一段光纤演变后趋于稳定 .     

线性调频信号DDS频率合成源的设计与实现

介绍了直接数字频率合成源的基本原理及其一种专用芯片AD9854的功能特点，提出了利用可编辑逻辑器件(CPLD)控制AD9854产生基带线性调频信号的设计方案，并具体分析了CHD和AD9854产生调频信号的工作原理。最后给出了设计方案的测试结果。经实用达到了比较满意的效果。     

A Spread-Spectrum Concept Combining Chirp Modulation and Pseudonoise Coding

This paper investigates the combination of chirp modulation and pseudonoise phase shift keying for spread-spectrum transmission of digital data. Data encoding is accomplished by assignment of positive and negative dispersive slope chirps for binary ones and zeros. Each chirp is then modulated by one period of a PN signature sequence. The performance in additive white Gaussian noise is analyzed, measures of performance being mean acquisition time, mean hold-in time, and bit error probability. Calculated and experimental results are presented for a 105 kbit/s modem. In the test system, SAW dispersive delay lines with a bandwidth of 16.4 MHz and 9.5 μs dispersion time serve for the key operations of chirp generation and pulse compression, and the signature codes are 127 bitm-sequences.     

基于QBOK调制的chirp超宽带系统设计与FPGA实现

基于Chirp扩频技术的超宽带（UWB）通信系统目前有两种调制方式：二进制正交键控（Binary Orthogonal Keying,BOK）调制和直接调制（Direct Modulation,DM）,基于BOK调制的超宽带系统实现简单,可靠性高,但信息传输速率不高。本文采用了一种改进的BOK调制方法——四进制双正交键控（Quaternary Bi—Orthogonal Keying,QBOK）,解决了BOK调制时一个Chirp波形只携带i比特信息而导致信息传输速率较慢的问题。本文论证了QBOK算法的可行性,并且在现场可编程门阵列（FPGA）硬件平台上实现了基于QBOK调制的ChirpUWB系统,实验结果表明,相比BOK来说,基于QBOK调制的ChirpUWB系统可以使信息传输速率提高一倍。     

数字调制信号接收技术

为了实现对多种数字信号的解调,设计了一种全数字接收机体制。对通用环载波同步方法及内插滤波码元同步方法进行了深入分析和设计。仿真结果表明,在误比特率为10-4时,所需Eb/N0比理论值高2 dB。基于通用环和内插定时技术的全数字接收机适用于对PSK,QAM数字调制信号的接收解调,满足数字VSLI硬件实现高集成度、小型化接收机的要求。     

Digital Single-Sideband Modulation

This paper considers digitized Weaver modulators for single-sideband modulation that can be used in radio communications and telemetering. A system of 12 such modulators to process 12 analog signals digitally is replaced by six multiplex modulators at the cost of additional computation at the input but with an overall reduction in computation time and a higher degree of accuracy. A unique digital filter is developed that can interpolate and output samples at multiples of the input sampling rate and exhibits a passband that occurs above the Nyquist frequency with no apparent distortion effects. A discussion of the Fortran simulation of a combined modulator-demodulator structure is included to verify the effectiveness of this scheme.     

使用直接数字频率合成的雷达线性调频信号产生技术

使用直接数字频率合成技术产生合成孔径雷达中宽带线性调频信号,系统结构简单,信号相位噪声小,易于实现合成孔径雷达中多模式的线性调频信号输出。文章详细介绍了基于AD9854的DDS芯片的硬件与软件的设计与实现,并且给出了最终的输出信号指标。     

数字电视的数字调制技术

主要介绍数字有线电视网下行、上行信道频谱的划分,各种数字调制方法、性能特点和优缺点比较.     

GMSK Modulation for Digital Mobile Radio Telephony

This paper is concerned with digital modulation for future mobile radio telephone services. First, the specific requirements on the digital modulation for mobile radio use are described. Then, premodulation Gaussian filtered minimum shift keying (GMSK) with coherent detection is proposed as an effective digital modulation for the present purpose, and its fundamental properties are clarified with the aid of machine computation. The constitution of modulator and demodulator is then discussed from the viewpoints of mobile radio applications. The superiority of this modulation is supported by some experimental test results.     

Delta-Sigma Modulation for Direct Digital Frequency Synthesis

This paper compares different $DeltaSigma$ modulation techniques for direct digital frequency synthesis (DDS). $DeltaSigma$ modulators such as MASH, feedforward, feedback, and error feedback have been implemented in both the phase and frequency domains in a CMOS DDS prototype IC fabricated in a 0.35-$mu$m CMOS technology with core area of $1.7times 2.1 {hbox {mm}}^{2}$ and total current consumption of 75 mA. Measured DDS performance demonstrates that the frequency domain $DeltaSigma$ modulation technique achieves better output spectrum purity than the phase domain method. Moreover, a programmable feedforward $DeltaSigma$ modulator is proposed to achieve different in-band and out-band noise shaping effects for DDS applications.      

一种适用于低信噪比的数字调制方式识别方法

针对低信噪比平坦衰落信道,本文提出了一种有效的数字调制方式自动识别的方法,该方法主要采用的技术包括噪声功率估计、构造高维特征矢量、使用基于人工神经网络的分类器.噪声估计有效地抑制了噪声影响,高维特征矢量的应用提高了不同调制信号的区分度,基于人工神经网络的分类器可以实现对高维特征空间较复杂的划分.仿真结果表明该方法显著地提高了低信噪比条件下数字调制方式的正确识别概率.     

DX-600数字调制发射机调制过程初探

ＤＸ－６００数字调制发射机调制过程初探孙旭广电部无线局７８３台ＤＸ－６００ｋＷ中波广播发射机是美国哈里斯（Ｈａｒｒｉｓ）公司生产的全固态数字化调制发射机，是集一大（大功率），三高（高效率、高可靠、高指标）、三化（固态化、数字化、自动化）于一体的新产品...     

应用于数字DC-DC转换器的高分辨率数字脉宽调制器设计

数字控制在电力电子领域的优势使得数字脉冲宽度调制的使用日益增加,然而其分辨率不足一直是制约开关电源领域中数字控制技术发展的主要因素之一。针对高分辨率数字脉冲宽度调制的应用需求,该文提出一种基于高速进位链结构的高分辨率数字脉冲宽度调制电路。该电路采用计数器、比较器、固定相移锁相环单元及高速进位链的混合结构,有效地提高了分辨率,并在Altera的Cyclone IV低成本现场可编程门阵列器件上实现。实验结果显示,当输入参考时钟工作频率为70 MHz时,该结构的分辨率可达到56 ps。此外,该电路还具有较宽的开关频率调节范围及较好的线性度等优点。     

具有饱和非线性的非克尔光纤中自相位调制效应所致啁啾

在考虑光纤损耗下,从理论上推导出具有饱和非线性的非克尔光纤中自相位调制效应产生啁啾的解析表达式;并在计算机上模拟了光纤中啁啾的演变过程。结果表明,非克尔光纤中的饱和效应越强,自相位效应所产生的啁啾越小;随着光纤传输,啁啾不断增大;而且啁啾与光纤损耗、入射脉冲的峰值功率等因素有关。     

数字调制技术的进展

本文简要介绍了数字调制技术的发展状况，目的在于对当代调制技术进行选择和开展进一步的研究，以提高通信的有效性和可靠性，数字调制技术的实现，促进了通信的飞速发展。     

衰落环境中数字调制识别仿真研究

调制方式的识别对于通信信号分析有着重要的作用。在现有有关调制识别的研究中,大部分都考虑的是加性高斯白噪声理想信道（AWGN）。文中通过仿真分析A．K．Nandi和E．E．Azzouz提出的数字调制识别算法（DMRAs）在衰落信道中的性能,详细研究了衰落信道特性对调制识别的影响。最后,得出了一些具有规律性的结论,对进一步深入研究衰落信道中调制识别技术具有一定的指导意义。     

A Digital Block-Processor for SSB-FDM Modulation and Demodulation

A new algorithm is proposed for the digital implementation of theM-channel SSB-frequency-division multiplexing (FDM) modulator and demodulator, which is computationally attractive and inherently insensitive to parameter quantization.     

Improved Frey Chaotic Digital Encoder for Trellis-Coded Modulation

In this brief, nonlinear digital filters with finite precision are analyzed as recursive systematic convolutional (RSC) encoders. An infinite-impulse-response (IIR) digital filter with finite precision (wordlength of N bits) is a rate-1 RSC encoder over a Galois field GF(2N). The Frey chaotic filter is analyzed for different wordlengths N, and it is demonstrated that the trellis performances can be enhanced by proper filter design. Therefore, a modified definition for the encoding rate is provided, and a trellis design method is proposed for the Frey filter, which consists of reducing the encoding rate from 1 to 1/2. This trellis optimization partially follows Ungerboeck's rules, i.e., increasing the performances of the encoded chaotic transmission in the presence of noise. In fact, it is demonstrated that for the same spectral efficiency, the modified Frey encoder outperforms the original Frey encoder only for N = 2. To show the potential of these nonlinear encoders, it is demonstrated that a particular nonlinear digital filter over GF(4) is equivalent to a GF(2) conventional optimum RSC encoder. The symbol error rate (SER) is estimated for all the proposed schemes, and the results show the expected coding gains as compared to their equivalent nonencoded and linear versions.     

模拟信号的数字化无线调制解调

以MCS-51系列单片机为核心，采用D／A转换器TLC5618，A／D转换器MAX197、无线数传模块PTR2000设计了一个模拟信号的数字化无线调翻解调系统。