直接数字产生中频调频信号

介绍了直接数字合成中频调频脉冲信号的两种实现方法及其实验结果     

一种基于小数锁相环的高速遥测发射机

为了缩小遥测发射机的频率间隔而不影响其性能,使用基于小数锁相环的结构,在达到了非常小的频率间隔的同时,可以在整个2.2～2.4GHz通信频带内灵活调整工作频点.采用准两点调制结构使得系统在保持较低误码率水平下达到较高的数据传输率.采用该结构设计实现了频点间隔100kHz、速率为2Mb/s的小型化PCM/FM遥测发射机.     

噪声调频干扰信号对直扩系统误码率影响的仿真分析

分析了噪声调频干扰信号的性能,建立了干扰系统和噪声调频干扰信号的仿真模型,仿真出不同干扰频率和不同干扰带宽下噪声调频干扰信号对直扩系统影响的误码率曲线,结果证明了设计的噪声调频干扰模型能够有效的干扰扩频通信系统。     

FM103S-Ⅱ型全固态调频广播发射机的原理与维护

以陕西数字广播通讯设备有限公司生产的FM103S-Ⅱ型FM发射机为倒,介绍了10kW全固态调频广播发射机的基本结构、工作原理和维护方法。     

多工调频广播的探讨及其发射系统的数字化实现方案

多工调频广播在保持原调频广播射频带宽不变的情况下,插入多种业务信息,具有投入小、见效快的特点,近年来在无线数据传输等领域应用广泛。在介绍多工调频广播的基本原理、基带频谱结构和各种技术指标的基础上,提出了一个基于DDS和DSP技术实现其发射系统的全数字化方案。     

基于DDS的调频信号一次谐波新研究

基于DDS的直接数字调频(DDFM)信号被广泛应用,DDFM信号比标准FM信号多出谐波分量,谐波特别是一次谐波是造成DDFM信号失真的主要因素。首次得到了DDFM信号的频谱解析式,基于此,采用数值计算结果函数拟合方法得到了DDFM信号一次谐波失真(FHD)新的近似公式,新公式比文献公式有更好的适用性和精确度。     

串行FRAMFM25H20原理及其应用

介绍非易失性铁电存储器FM25H20的性能特点,内部结构和工作原理;给出单片机与FM25H20的写操作接口电路图.以及FM25H20的写操作流程图.归纳出任何一款8位数据总线宽度用于计算机系统时使用FM25H20的方法.从而实现大客量存储系统的扩展.     

Modifications of the Cubic Phase Function

By introducing a symmetric pair of time instants, a modification of the Cubic phase （CP） function, named as the Quartic phase （QP） function, is proposed to estimate the quadratic FM signal. The performance in terms of estimate bias and variance is presented via the first-order permutation principle. Two extensions are presented for multiple components and the cubic FM signals. Both theoretical analysis and numerical examples confirm that the QP function and its extensions provide a number of advantages, such as： （1） lower asymptotic Mean-square error （MSE） for the estimate of the third-order phase pa- rameter at high SNR; （2） a better capability of discriminating multicomponent signals; （3） a lower SNR threshold for the estimates of the cubic FM signal.     

Novel SREKF-based recurrent neural predictor for narrowband/FM interference rejection in GPS

The GPS provides accurate positioning and timing information that is useful in various applications. A new adaptive neural predictor for GPS jamming suppression applications is proposed. The effective and computationally efficient square-root extended Kalman filter (SREKF) algorithm is adopted to adjust the synaptic weights in the nonlinear recurrent architecture and thereby estimate the stationary and non-stationary narrowband/FM waveforms. Cholesky factorization is employed in Riccati recursion to improve numerical stability because of the propagation of round-off errors in conventional KF equations. The main characteristics of the proposed SREKF-based canceller are their rapid convergence and favorable tracking performance. Simulation results reveal that its SNR improvement factor exceeds the factors of conventional LMS, RLS, ENA and TLFN filters in single-tone CWI, multi-tone CWI, pulse CWI and FM jamming environments, respectively.     

Fluorescence lifetimes in BO2 (A2Πu)

Fluorescence lifetimes and fluorescence quenching rates are reported for several vibronic levels in the A²Π_u electronic manifold of BO₂. The relationship of these results to earlier Hanle-effect measurements is discussed.