宽带雷达信号调制模块设计与实现

现代宽带高分辨雷达为适用各种复杂的环境,要求其信号调制方式具有多样化和灵活性。采用单片机串口通信接收命令,FPGA高速配置DDS和射频调相器,实现了一种支持连续波调频调相和脉内调频调相的雷达信号调制模块。通过代码控制解决了脉内调频较难同步的技术难题。整个调制模块载波中心频率为1.6 GHz,调频波形有正、负锯齿波和三角波,调频带宽可达600 MHz,调相序列有巴克码、伪码L和M序列。测试结果表明,系统输出信号稳定,可靠性高。     

Development and Comparative Analysis of a Pulse-Width Modulation Strategy

A pulse-width modulation (PWM) strategy used to generate a control signal for an electronic switching inverter is described. A triangular timing wave of frequency f=6?N?F is used where F is the reference wave frequency, and N? 1 is an integer. The polarity of the timing wave is the same as the polarity of the half period of the reference wave. A comparative analysis is presented of the PWM signal generated with this strategy with respect to a similar signal generated by means of a "traditional" triangular modulation strategy.     

Broad-Band Varactor-Tuned Impatt-Diode Oscillator (Short Papers)

A varactor-tuned IMPATT-diode oscillator with a continuous and monotonic tuning bandwidth of 27 percent and a potential tuning range in excess of 40 percent is described. The results of a computer program which optimizes the tuning bandwidth of the equivalent circuit of the voltage-controlled oscillator (VCO) are presented. The VCO consists of two varactors located symmetrically on each side of an IMPATT diode all mounted in a ridged waveguide with two matched outputs into 50-Omega coaxial. Experimental results on bandwidth, power output, frequency linearity, and FM noise are presented.     

Study and Fabrication of a Frequency Divider-Multiplier Scheme for High-Efficiency Microwave Power

The design, fabrication, and experimental evaluation of an exploratory 8.2 W, microwave FM power amplifier for the 4-GHz band are presented. It operates on a frequency divide, amplify, and multiply scheme receiving about 2-4 dBm of FM signal in the 4-GHz band, divides the frequency coherently by two, amplifies the modulated signal to about 10.4 W, and doubles the frequency coherently, yielding about 8.2 W into standard 50-ω 4-GHz load, with an overall efficiency of about 30 percent. Frequency halving is accomplished by a wideband regenerative frequency divider yielding about 1-2 dBm of signal at 1995 MHz. The signal is amplified by commercial class C amplifiers and is restored to the 4-GHz band by a stacked varactor containing two 0.32 ω, 15-pF chips in a coaxial embodiment. This entire ensemble, with a total breakdown of 160 V, serves as a frequency doubler.     

一种温度不敏感频率范围宽的三角波振荡器

本文介绍了一种由双比较器型施密特触发器构成的三角波振荡器电路,它通过对电容恒流充放电产生对称三角波;此电路的优点是其产生的三角波的频率稳定且具有很高的精度,并对温度和电源的变化不敏感;文章最后给出了电路的Hspice仿真结果。     

对称三角线性调频连续波信号的检测与参数估计

结合低截获概率雷达中常用的对称三角线性调频连续波信号的特点,提出了基于Radon-Ambiguity变换（RAT）和分数阶傅立叶变换（FRFT：Fractional Fourier Transform）的对称三角线性调频连续波信号的检测与参数估计新算法。该方法不仅给出了对称三角线性调频连续泼信号的调频率和初始频率的参数估计,并且推导出了调制带宽估计的表达式。通过仿真验证了该方法的有效性并具有很好的估计性能。     

基于DSP芯片SPWM控制的双Buck组合式三相逆变电路的研究

文中以大功率逆变电源为出发点，以组合式三相双降压半桥逆变电路为研究对象，提出了双极性三角波加中频正弦波的正弦脉宽调制控制技术，介绍了利用数字处理器TMS320LF2407实现SPWM的具体方法。试验结果证明，该方案实用可行，试验波形良好，谐波畸变THD〈1%。     

基于非合作照射源的无源雷达直达波抑制技术

利用非合作照射源对目标探测的雷达具有良好的“四抗”性能,是目前电子对抗研究的一个热点。文中首先介绍了该体制雷达对目标进行有效探测的技术瓶颈———直达波干扰抑制;然后提出了相应的一系列解决方案;最后给出了以调频广播信号为非合作照射源的一个实验系统,并利用该实验系统采集的数据进行仿真,仿真结果验证了上述方法的有效性。     

Surface transverse wave based FM modulator/demodulator

An FM modulator/demodulator system employing three identical surface transverse wave (STW) resonators is described. It operates at a centre frequency of 1012 MHz and can transmit data at over 100 kbit/s. This low cost system has a low noise and can detect FM signals with a deviation of less than 0.1 ppm.<>     

对称三角线性调频连续波信号模糊函数分析

本文从对称三角线性调频连续波雷达体制的特点出发,导出了对称三角线性调频连续波信号模糊函数,分析了它的特点;阐明了它与单斜率线性调频连续波信号和脉冲LFM信号模糊函数的区别;从模糊函数的角度分析说明了采用对称三角线性调频连续波信号相对于单斜率线性调频连续波信号可以大大提高目标的分辨力,并能消除多目标环境中运动目标的距离速度耦合现象.     

FDFD analysis of electromagnetic scattering in anisotropic mediausing unconstrained triangular meshes

A method using finite differences in the frequency domain (FDFD) for modeling field interaction and propagation in anisotropic media with generalized tensor permittivity and permeability, and with complex geometry, is presented. The method uses an unconstrained mesh with triangular cells, which provides an efficient discrete approximation of curved surfaces. The two-dimensional problem with transverse field excitation is studied. Computed results comparing this algorithm to published data for the former case show excellent agreement. The analysis provides information for all view angles simultaneously at a single frequency. The method can be adapted to a time-domain formulation to analyze the effects of wave pulses and multiple frequencies at a single observation angle     

Simultaneous broadcasting of analog FM and digital audio signals bymeans of adaptive precanceling techniques

A method for broadcasting digital audio simultaneously with existing analog frequency modulation (FM) radio is presented. The method is based on precomputing the response of the host analog FM signal at the digital receiver and precanceling it at the transmitter. As a result, the digital transmission is free from interference from analog FM. We select the rate and power level of the digital transmission in a manner that the interference the digital data incur on the analog FM signal remains at acceptably low levels. The digital transmission is based on adaptive orthogonal frequency-division multiplexing (OFDM) (adaptive multicarrier). The frequencies and number of carriers of the digital multicarrier modem are judiciously selected in a time-varying fashion so as to cause a negligible distortion in a standard receiver for analog FM. Simulations based on conservative nonoptimized signal design indicate that data rates up to about 130 kb/s inside the 200-kHz FM channel are achievable for acoustic test signals. We present a number of numerical examples where the average digital data use up to 50% of the 200-kHz power spectrum with digital signal power levels 25-35 dB below the analog signal. Due to the resulting variable-rate digital transmission, a control channel is required. A method of precanceling with multiple orthogonal direct-sequence spread-spectrum schemes is also presented     

调频激励器的设计与实现

数字调频激励器是调频发射机的信息处理核心,直接决定发射机性能的优劣。另一方面,它又部分承担发射机故障处理及报警的职责,即调频激励器应对自身及发射机整机进行监控。在发射机运行出现故障时需进行自身调整,从而保证发射机运行的正常和安全。阐述了采用直接数字式频率合成器（DDS）软件调频方式对模拟信号进行调制。DDS产生的信号频率精度很高,且与晶体振荡器的稳定度相同,可达10-6以上。其单片机控制可以随意切换载波频率,频偏,调制度等,并且可以容易地实现。该系统的测试结果令人满意。     

Spectral density function of multilevel continuous-phase FM

Compact formulas are derived for the spectral density function of an ensemble of continuous-phase constant-envelope multilevel FM waves. The results are general and are presented in terms of averages of elementary functions. Both continuous and discrete spectra are treated, and conditions in terms of the modulation parameters are given under which lines in the spectrum are present. The formulas are applicable in the study ofN-ary FM data transmission systems as well as in pulse frequency modulation.     

Broad-Band Power Amplification with Gunn-Effect Diodes

Coherent single-frequency amplification has been obtained from supercritically doped (n/sub 0/l >10/sup 12/ cm/sub -2/) Gunn-effect devices biased above threshold. Heavy circuit loading was employed such that the diodes oscillated weakly near the transit-time frequency. A sufficiently strong input signal suppressed the self-oscillation and was amplified. Useful amplification was obtained in the saturation region with the output power comparable to that obtainable from the diode as an oscillator. The frequency response and saturation characteristics of a reflection amplifier in X band are described. Useful bandwidths from 1 to 16 percent with power gains from 11 to 4 dB were observed for a single diode. FM and AM noise spectrum measurements are also presented.     

基于MSP430F499的波形合成器

以MSP430F499为核心,主要由方波振荡电路、分频与滤波模块、移相电路、放大电路、加法器等组成。将方波振荡器的信号分频滤波产生不同频率的正弦波,经移相放大等处理后,分别根据方波三角波谐波组成关系,再合成方波和三角波。滤波模块对同一信号进行二次滤波,先用开关电容滤波器滤波,再经三阶巴特沃斯低通滤波器滤波,降低了高次谐波对信号的影响同时保证了通带内信号的平坦。可通过按键进行波形切换以及合成阶数切换,人机交互灵活,界面友好,操作简单。     

LFMCW雷达目标运动补偿新方法

针对对称三角线性调频连续波（STLFMCW）雷达体制，分析了目标运动对回波信号的影响，提出了基于距离像峰值偏移估计和脉组相位差分的径向运动参数估计方法，较好地解决了目标运动的补偿问题。仿真结果表明，该方法估计精度高，抗噪性能好，运算量低，便于系统实时处理。     

BPSK system with sounder to combat Rayleigh fading in mobile radio communication

A simple method is proposed to remove random FM from a fast Rayleigh faded binary phase shift keying (BPSK) signal and the great improved performance of reducing the irreducible error is presented. In the mobile radio environment, there happens inevitably a fast Rayleigh fading which causes random FM. The phase error of the reference signal due to random FM will degrade the bit error rate (BER) performance, even if the signal-to-noise ratio is sufficiently high. In the realization of reliable mobile communication, removal of this random FM is an unavoidable theme. Proposed strategy is to transmit a sounding continuous wave (CW) together with a BPSK signal, each phase being kept orthogonal and each power being kept the same. This CW wave is also used as the reference signal in coherent reception. The BER performance of this system is worse by 3 dB than that of the coherent BPSK in a slow Rayleigh fading environment.     

副载波对广播信号的频谱和模糊函数的影响

根据调频立体声广播中副载波的产生原理,针对广播信号的频谱和模糊函数图进行分析,指出:有副载波的广播信号的模糊函数图的零距离切面在导频信号的二分频的整数倍上出现相关峰、多普勒切面则由无副载波的广播信号的模糊函数图的多个多普勒切面加权相加而成;同时带宽较窄的有副载波的广播信号的模糊函数图的相关峰呈现多峰.最后给出了消除多峰的方法和实录信号的处理结果.