Spectrum Conservation and Characteristics of Single-Sideband Phase Modulation

Phase modulation with an analytic signal, which is a Gaussian random process, is examined in order to determine the amount of spectrum conservation that may be achieved by using single-sideband phase modulation (SSB-PM) rather than conventional phase modulation (PM). The autocorrelation function is derived and found to be an analytic signal in terms of the autocorrelation function of the actual modulating signal and its Hilbert transform. When the modulating signal strength is very low, the sideband spectral distribution is the same as that of the actual modulating signal or single-sideband amplitude modulation. As the modulating signal mean-square value is increased, the sideband spectrum broadens and approaches a Gaussian shape. The average power output of an SSB-PM system increases exponentially with input modulating signal strength, while the carrier power remains constant. For the same modulating signal mean-square value, a greater fraction of power is in the one sideband of an SSB-PM system than in the two sidebands of conventional PM. Single-sideband phase or frequency modulation always effectuates spectrum conservation in the continuum when it is compared with conventional phase or frequency modulation on the basis of equal relative sideband power. A Fourier transform computer program is used to generate SSB-PM spectral distributions with varying modulating signal mean-square values, when the modulating signal spectrum is a low-pass rectangular spectrum, a narrowband pass spectrum, and the shape of an average voice spectrum. These examples illustrate the power series formulation of the output spectrum as well as the theoretical analysis of bandwidth.     

Measurement of Bandwidth of Microwave Resonator by Phase Shift of Signal Modulation

Bandwidth is measured by transmission of a signal with sine-wave modulation through a microwave resonator under test. The modulation frequency is adjusted so that the envelope is delayed 45/spl deg/ with respect to the input, indicating that the two sideband frequencies are separated by the half-power bandwidth. The resonance ratio (Q) is then equal to the ratio of carrier frequency over twice the modulation frequency. This depends on observations of these frequencies and the modulation phase shift, but not on the amplitude. It is insensitive to detuning or incidental frequency variation of the resonator or the signal. In a resonant cavity tested, an observed bandwidth of 30 kc at 700 mc indicated that Q =23,300.     

Super Wide Deviation Phase Modulator

A phase modulator is described which can directly deviate a crystal-controlled carrier by 1000 rad or more. Frequency multiplication or auxiliwry automatic frequency control (AFC) circuits are therefore not required. The modulator uses an accurate frequency source, a wide-band voltage controlled oscillator, a delay line, and two mixers The achievable phase deviation is proportional to the time-bandwidth (TB) product of the delay line, while the modulation bandwidth is inversely proportional to the time delay. Suitable delay lines are available using either bulk wave or surface acoustic wave transnission. Signal-to-noise ratio (SNR) and distortion are compatible with requirements for broadcast service. Design examples are given for monophonic and stereophonic FM broadcast modulators.     

Analysis of a frequency-modulated reflex klystron with minimum incidental amplitude modulation

Simultaneous modulation of the reflector and beam voltages of a reflex klystron will produce frequency modulation with minimum incidental amplitude modulation. The required variation of reflector voltage with beam voltage, for constant output power, is derived from the fundamental equations of the reflex klystron. Experimental verification of this analysis is presented. Reflex klystron oscillators which can be frequency modulated with minimum incidental amplitude modulation find application in FM Doppler radars, communications systems, and as signal sources for microwave testing.     

基于直接数字频率合成技术的FM/PM的实现

直接数字频率合成（DDS）是一种可以实现多种调制的新的频率合成技术。调频和调相统称为角度调制。调频是根据调制波的幅度去改变载波的频率;调相是根据调制波的幅度去改变载波的相位。本文在数字电路中实现了模拟调制,大大提高了可移植性和可控性。文章首先介绍了用DDS实现FM、PM调制的基本原理,然后在通用的基带调制硬件平台基础上,给出了一种基于DSP和FPGA实现FM、PM调制的具体方法。最终通过DAC电路,在输出端口得到最终的输出,并且在频谱仪上得到了设定的满足设计要求的所频谱。     

An analysis of a super wide–band FM line discriminator

This paper presents a dynamic analysis of an extremely wide-band FM line discriminator consisting of a pair of transmission lines and coupling resistors. The relationship between the harmonic distortion of the output waveform of the discriminator and the permissible frequency deviation of the input signal is analyzed in detail by the method of Fourier transform. It is shown that the coupling resistor constant γ (see Fig. 1) should be set at unity from the viewpoint of the sensitivity of the discriminator and the constant input impedance of the discriminator over the frequency deviation of the input signal. Theoretically, an FM signal having 100 per cent frequency deviation could be detected by this discriminator with 2.67 per cent harmonic distortion while the input impedance of the discriminator remains constant (equal to characteristic impedance of the transmission line Z0) during the frequency deviation. Experimental results are presented to verify the theoretical results obtained. The characteristic curve of the discriminator is linear for 40 per cent frequency deviation from the carrier frequency 85.5 Mc, and its input impedance remains within ±14 per cent of the idea value Z0.     

A discrete-time method of demodulating large deviation FM signals

A method of enhancing the performance of a numerical FM discriminator in specific receive signal conditions, using frequency feedback techniques, is developed and evaluated. The receive signal conditions of interest are: (1) frequency deviations that are large relative to the bandwidth of the message signal; (2) a low-uniform (complex) sample rate commensurate with the bandwidth; and (3) noise strengths that yield values of input carrier-to-noise ratio of the order of 10 dB or more. Through computer simulation, observed phase cycle-slip counts and phase noise variance estimation are used to compare the enhanced demodulator to the performance of a numerical FM discriminator baseline. Based upon the theoretical analyses and simulation results, the presented method of numerical FM demodulation is shown to be a viable technique for enhancing the performance of numerical FM discriminators under the given modulation conditions     

大动态PCM/FM遥测信号的非相干解调

针对大动态低码率PCM/FM遥测信号的可靠接收问题展开研究,给出了一种基于连续相位调制（CPM）信号原理的载波频偏矫正及差分序列检测的非相干接收方案。针对限幅鉴频、多符号检测及差分序列检测等3种非相干解调算法,介绍了各自应用于PCM/FM信号的算法原理,并比较了3种算法的解调性能及对大动态环境的适应能力。计算机仿真表明,在无残留频偏情况下,2符号相位差分序列检测性能最好;但在0.05倍码速率的残留频偏下,1符号相位差分序列检测的性能更好,优于2符号相位差分序列检测、限幅鉴频检测和多符号非相干检测。对PCM/FM信号的讨论包含了几种典型的非相干解调,对大动态环境下的PCM/FM接收有重要的参考价值。     

一种载边比可调单边带全双工光载无线系统

理论分析了一种基于双平行马赫曾德尔调制器(MZM)的2倍频光单边带调制方案,仿真研究了基于该方案的载波重用全双工光载无线(RoF)通信系统性能.合理设置射频驱动信号相移及双平行MZM主调制器偏置电压产生单边带信号,再调整调制指数以实现光载边比ROCS的连续可调谐.讨论了射频信号相移、主调制器偏置电压、双平行MZM消光比...     

A Novel Direct Detection Microwave Photonic Vector Modulation Scheme for Radio-Over-Fiber System

This letter demonstrates the feasibility of a novel direct detection microwave photonic vector modulation scheme for the radio-over-fiber (RoF) system. Unlike the traditional double-sideband with optical carrier suppression modulation scheme, which can carry only the on-off keying data format, the proposed scheme encodes the electrical vector signal on either the upper sideband (USB) or the lower sideband (LSB) only and a pure optical subcarrier on the other sideband. Therefore, phase and amplitude information will be preserved after direct detection. A frequency doubling scheme is employed to reduce the cost of RoF systems. Additionally, the relative intensity between USB and LSB can be easily tuned by adjusting the individual power of electrical driving signals to optimize the performance of the optical radio-frequency signals. A proof-of-concept experiment is conducted by using a 1.25 Gb/s BPSK signal at a carrier frequency of 20 GHz. After transmission over 50-km single-mode fiber, the receiver sensitivity penalty is less than 0.5 dB.     

垂直腔面发射激光器的内调制特性

面向芯片原子钟(Chip Scale Atomic Clock,CSAC)的垂直腔面发射激光器(Vertical Cavity Surface-Emitting Laser,VCSEL)通过微波调制产生具有特定光频差的相干激光,与原子作用后的跃迁谱线频率作为参考标准,最终可获取高精度的频率信号。因此,垂直腔面发射激光器在芯片原子钟系统中至关重要。介绍了VCSEL激光器的内调制原理,搭建了其内调制特性实验测试平台,开展了激光器对射频调制响应特性研究,记录了激光器边带信号随着注入电流和射频输出功率的变化情况,并分析了射频调制对激光器边带信号的影响特性以及Bogatov现象引起的边带不对称现象。实验结果显示:当射频信号频率为3.41734 GHz,注入电流为1.2 mA,射频输出功率为3.5 dBm时,可获得优化的高频调制光谱,为芯片原子钟提供优质的光源。     

A Microwave Ferrite Single-Sideband Modulator

A microwave single-sideband modulator has been designed utilizing two reflection types of Faraday rotation ferrite-balanced modulators. Power is fed to the two balanced modulators by means of a 3-db quadrature hybrid such that each modulator has equal incident power with a 90-degree phase difference. The output power of the balanced modulators is combined by means of a magic tee sum and difference circuit. It is shown that if the modulation signals applied to the balanced modulators are in phase quadrature, the upper sideband will appear at the output sum arm and the lower sideband will appear in the output difference arm. An analysis of the device relates the spurious and undesired sidebands to the conversion loss, and a method is proposed for minimizing carrier output. The drive power is reduced due to the use of reflection-type balanced modulators, and experimental data is presented for the modulation frequency impedance and drive power requirements. The temperature and frequency sensitivity of the undesired sidebands have also been measured. A number of applications of the device are discussed.     

Phase noise characterisation of planar magnetostatic wave oscillators

The phase noise performances of a planar configuration of a magnetostatic wave oscillator have been investigated. The behaviour of the output signal has been studied in terms of the single sideband power spectral density. Values as low as -100 dBc at 100 kHz of offset from the carrier frequency have been measured in the whole range of tunability, by using two different resonators.     

基于偏振调制器并联产生16倍频毫米波的研究

针对高倍频毫米波的产生问题,文章提出了一种基于4个偏振调制器并联产生16倍频毫米波的方案,利用相关光边带极性的不同,使合成光信号中只保留载波和8n阶边带。经过适当选取调制指数值和光电探测器拍频后,获得16倍频毫米波信号。文章理论分析了产生16倍频毫米波信号的原理,推导出方案所产生的±8阶光边带信号的光边带抑制比为61.72 dB,16倍频毫米波信号的射频杂散抑制比为55.70 dB。仿真实验获得的光边带抑制比和射频杂散抑制比分别为60和53 dB。同时分析了射频信号相位偏移及调制指数对抑制比的影响。实验结果与理论分析吻合,验证了所提方案的可行性。     

基于FPGA的FM信号发生器设计与实现

摘要：为提高FM信号发生器的频率准确度和稳定度,并使其相关技术参数可调,设计了一种基于FPGA和直接数字频率合成（DDS）技术的产生方法。系统以labwindows/cvi为上位机开发环境,实现FM信号调制参数的可调,并通过PCIE接口将上位机设置的FM信号控制字和波形数据传给FPGA,FPGA内部通过控制DDS核来实现FM信号的产生。测试结果表明,FM信号的频率精度高且稳定性好,最高输出载波频率达40MHz,幅度精度能达到5mV。该FM信号发生器在软件无线电、雷达目标特征识别和雷达距离探测等领域具有很高的应用价值和广阔的应用空间。     

Bias-Tuned Injection-Locked Discriminators

A new form of microwave FM discriminator using simultaneously the technique of injection synchronization and automatic bias tuning has been proposed. The present discriminator basically consists of an injection-synchronized Gunn oscillator and an arrangement for bias tuning of the oscillator in correspondence to a measure of the instantaneous phase/frequency error between the incoming signal and the Gunn oscillator output. A detailed analysis on the discriminator performance, which closely fits in with the experimental results, has been presented. The performance of the present discriminator is much better than that of the conventional one.     

Dynamic Range of Frequency Modulated Direct-Detection Analog Fiber Optic Links

A frequency modulated (FM) analog optical link using an FM discriminator is analyzed. Figures-of-merit are derived, including expressions for the second-order (OIP2) and third-order intercept points (OIP3), spurious-free dynamic range (SFDR) and noise figure (NF). It is found that a discriminator with linear field transmission and constant group delay will produce no third-order or higher-order distortions, and balanced detection will suppress the remaining second-order distortion. Low biasing the discriminator is found not to improve the NF of the link. Residual intensity modulation (IM) of the laser is shown to significantly increase the link's distortion. A discriminator using tenth-order finite-impulse response (FIR) filters implemented in planar lightwave circuits (PLC) is proposed and shown to improve OIP3 by 31 dB over a Mach-Zehnder interferometer (MZI) discriminator.      

调频遥测信号载波频率的精确估计

传统调频遥测信号载波频率估计算法对输入信号降采样后直接进行快速傅里叶变换，实现方法虽然简单，但测量精度较差，无法适应高动态、低信噪比等复杂场景。为此，提出了一种调频遥测信号载波频率的精确估计算法。两并联补偿支路先分别采用正、负调频频率对输入信号进行频率预先补偿，低通滤波后完成降采样处理，削弱调频频率的频谱影响；频率搜索状态对采样数据进行载波多普勒变化率的频率补偿，经过快速傅里叶变换、非相干积分和频谱重心搜索完成频率解算，提高载波频率的检测性能。试验与分析表明，所提算法在高动态、低信噪比等复杂场景下可显著提高调频遥测信号载波频率的估测性能。     

Implementation of PMOP phase transition detector based on DFD

The existing phase modulation on pulse (PMOP) phase transition detector which used on signal processing of electronic warfare system has a problem on its detection performance, especially with frequency and PMOP method. We analyze the problem on existing PMOP detection method and we propose new implementation method. This PMOP detector is based on digital frequency discriminator (DFD) which use delay line and I/Q mixer. The proposed method combine the radar signal phase change on I channel and Q channel. This method makes it possible to analyze frequency and phase modulation method which is not possible on existing PMOP detector. And from proposed PMOP detection method, we can miniaturize the PMOP detector by using the DFD I/Q output which designed with delay line and I/Q mixer.     

基于多频相位调制的光学单边带调制器研究

提出了一种基于多频相位调制技术实现光学单边 带调制信号产生的新型方案。当含有基频和谐波成分的多频调制信号施加到Mach-Zehnder( MZ)电光调制器上时,若驱动信号波 形选取合适,可使调制后的光信号功率集中在边带谱的一个频率成分上,其它频率成分被抑 制, 从而获得光学单边带调制信号的输出。以十频相位调制为例,计算了与之对应的光学单边带 调 制信号的光谱结构,其中信号能量利用率近88%,载波抑制比大于24dB,边频抑制比大于18 d B, 从理论上证明了本文所述方案的可行性。进一步的仿真结果显示,随着驱动信号谐波数的增 加, 载波抑制比、边频抑制比和信号能量利用率均逐渐增大。可见,为了获得优质的光学单边带 调 制信号,应在实际条件允许的情况下使用尽可能多的调制频率。此方案能量利用率相对较高 , 仅用到了一级商用MZ相位调制器,方案结构简单,是一种产生光学单边带调制信号的有效途 径。