双音多频通信接口的设计

介绍了一种利用双音多频(DTMF)信号进行数据通信的接口电路,具体阐述了该电路的组成原理以及软硬件的实现方法.     

Design and Performance of a Digital Multifrequency Receiver

An experimental multifrequency receiver for recognition of digitally encoded multifrequency signaling was designed, constructed and tested. The receiver is based on a quadrature detection technique that consists of digital demodulation followed by second-order, lowpass digital filtering. The post filtering processing produces an estimate of the amplitude of each of the six multifrequency tones and provides suitable information for thresholding and timing measurements. The receiver performs correctly even when subjected to severe environmental conditions including an analog signal range of 23 dB, 10 ms signal interruptions ('hits') and 20 ms signal spacings. The receiver's operation demonstrates the robustness of the digital signal processing techniques employed. The design of the receiver exploits the use of subsampling techniques to increase the efficiency of the hardware through greater multiplexing. When using subsampling, 128 multifrequency receivers with 16-bit words are realized with 6.5 dual-in-line packages per receiver; commercial TTL logic circuits, a 4-bit serial-parallel pipeline multiplier circuit, serial data and a 16.384 MHz clock are assumed.     

An Algorithm for an Adaptive Multifrequency Receiver

This paper presents a simple and effective algorithm for an adaptive multifrequency receiver that can be used for several types of multifrequency signals. This algorithm uses the ability of frequency detection of signal processing using extreme and zero-crossing points in the multifrequency signals and an adaptive second-order notch filter.     

差分相干同步CDMA信道中的一种新的抗多址干扰接收机

本文考虑加性白噪声环境中的同步ＣＤＭＡ通信系统，给出了一种新的线性非相干解调接收机，同时给出了这种抗多址干扰接收机的误码率及渐近效率。结果表明，对于使用Ｇｏｌｄ码作特征码的ＣＤＭＡ系统，当用户数不大于特征码长度时，这种接收机的最小渐近效率是０．５     

扩频通信接收系统的软件无线电实现方法

主要论述了直扩系统的软件无线电的接收结构。提出了接收系统的模型框图，然后给出了一种实用的硬件实现结构，最后对此系统的抗噪性能进行了分析。     

堆叠H形多频段微带天线

结合分形树理论和H形贴片结构,设计了一种堆叠式多贴片的微带天线.该天线主要由1个馈电单元和4个H形寄生贴片组成,具有5个工作频段,每个频段的辐射方向图一致性好.H形结构的应用,使得该天线比常规矩形贴片天线的尺寸小.此外,用传输线模型理论分析了该天线,给出了谐振频率的计算公式,并对天线进行建模、仿真、分析和实测,实测结果和仿真结果吻合.     

Study of Coniferous Forests Using Multifrequency Polarimetric Synthetic-Aperture Radar

Journal of Communications Technology and Electronics - Specific features of radio reflection of coniferous forest in decimeter- and meter-wavelength ranges are considered. The study is stimulated...     

基于USRP的DVB-T接收机实现

为提高地面数字电视广播(DVB-T)接收机的实现灵活性,基于由通用软件无线电外设(Universal Software Radio Peripheral,USRP)和通用计算机组成的软件无线电平台,实现DVB-T接收机。接收机以USRP作为射频前端,在通用计算机中完成全部基带信号处理、视频解码与显示等。测试结果表明,接收机可实现对DVB-T信号的接收,为接收机算法开发、验证与评估提供了更为灵活的方法。     

一种同步Nyquist折叠接收机参数估计算法

由于在同步Nyquist折叠接收机结构中使用了多分量本振及对应的数字信号处理算法,单个双通道模数转换器所接收的信号频率范围可超过其Nyquist采样带宽。针对同步Nyquist折叠接收机结构,提出了基于Wigner-Hough变换的参数估计算法。对算法的理论分析表明,对不同本振周期信号的Wigner-Hough变换进行积累,能有效提高Nyquist区域检测性能。最后,仿真结果证实了提出的算法在输入信噪比优于-15 dB后,能获得准确的频率估计结果。     

基于注频锁相和非线性振荡器的接收波束形成

本文提出以注频锁相技术为基础接收窄带信号的非线性振荡器波束形成器,给出了注频锁相现象的Adler方程及非线性振荡器的动力微分方程.并提出了零陷多波束形成算法,推导权矢量,并通过仿真分析该算法的信号波达图效果.     

A Linearization Technique for RF Receiver Front-End Using Second-Order-Intermodulation Injection

A linearization technique is proposed in which low-frequency second-order-intermodulation $({rm IM}_{2})$ is generated and injected to suppress the third-order intermodulation $({rm IM}_{3})$. The proposed linearization technique is applied to both a low-noise amplifier (LNA) and a down-conversion mixer in an RF receiver front-end (RFE) working at 900 MHz. Fabricated in a 0.18$ mu{hbox{m}}$ CMOS process and operated at 1.5 V supply with a total current of 13.1 mA, the RFE delivers 22 dB gain with 5.3 dB noise figure (NF). The linearization technique achieves around 20 dB ${rm IM}_{3}$ suppression and improves the RFE's ${rm IIP}_{3}$ from $-$ 10.4 dBm to 0.2 dBm without gain reduction and noise penalty while requiring only an extra current of 0.1 mA.      

A Submillimeter Measurement System Using a Harmonic Mixing Superheterodyne Receiver

A measurement system for use in the submillimeter wavelength region has been assembled and evaluated. This system utilizes two 70-Gc klystron sources and operates as high as the sixth harmonic. One of these sources provides the fundamental input power for a crystal harmonic generator which serves as the transmitter. The other klystron serves as a fundamental local oscillator for the harmonic mixing receiver. Incorporation of harmonic mixing techniques provides identification and selection of individual harmonics and simultaneously affords improved sensitivity over crystal video detection. The dynamic range of the measurement system is here defined as the difference (in db) between the maximum signal level at a specified harmonic, and that level for which the signal-to-noise ratio is unity. Dynamic ranges were measured to be 61 db at 210 Gc, 46 db at 280 Gc, 32 db at 350 Gc, and 29 db at 420 Gc, selection of any of these frequencies is accomplished by inserting an appropriate filter in the receiver's IF amplifier. Techniques are described which can be used to improve substantially the dynamic range at the above-mentioned frequencies. The system is suitable for many types of measurements in the short millimeter and the submillimeter region, and has good possibilities for frequency extension by increasing the frequency of the fundamental signal. Some data are included on measured transmission losses of dominant mode, and oversized, overmoded waveguide. The latter type is seen to offer advantages of reasonably low loss and simple construction when transmission over moderate path lengths is needed.     

A V-Band Communication Transmitter and Receiver System Using Dielectric Waveguide Integrated Circuits

A V-band communication transmitter and receiver is described. Both units make extensive use of passive microwave components fabricated rising millimeter-wave insular line integrated circuits (MILIC's). These components consist of rectangular dielectric rod antennas, a MILIC ferrite isolator, a bandpass ring filter, a directional coupler, and sections of dielectric insular waveguide. The passive insular waveguide components are integrated together, along with split block metal waveguide mounts for the active devices, in order to form the RF circuitry of the transmitter and receiver.     

A Multiuser Detection Receiver Using Blind Antenna Array and Adaptive Parallel Interference Cancellation

In this paper, the problem of multiuser detection for synchronous code division multiple access systems in both additive white Gaussian noise and multipath channels is addressed. A new multiuser detection receiver that uses an adaptive blind array along with an adaptive parallel interference canceler is proposed. The replacement of a conventional antenna array with a two-dimensional RAKE receiver is also considered for frequency selective Rayleigh fading channels. By using a constrained optimization criterion along with the gradient-projection algorithm, a blind algorithm for the adaptation of the array response vector is proposed. The new algorithm is superior to a few typical blind algorithms in the literature in terms of both performance and computational complexity. The proposed receiver has the ability to cancel very strong multiple access interference coming from the same direction as the desired signal. Simulation results are presented to show the excellent performance of the proposed combination scheme in comparison to that of using either a multiuser detection or adaptive antenna arrays in a severe near-far situation.     

采用ZVS条件控制的DC-DC同步整流技术

以Buck结构DC-DC为例,结合仿真波形分析了DC-DC一个开关周期4个阶段的电流电压情况,证明由ZVS条件控制MOS管的导通和断开是损耗最小的。由此提出了两种实现ZVS控制的电路拓扑：同步反馈控制以及由程序综合的控制电路。并与自适应控制进行了比较。同步反馈控制利用时钟和ZVS条件,结合MUX实现了导通和关断的理想波形。由程序综合的控制电路以PWM控制和ZVS控制为目标,并由时钟同步,实现了对驱动波形的控制。     

MMSE Multiuser Receiver for Uniformly Quantized Synchronous CDMA Signals in AWGN Channels

We analyze and design the minimum mean-square error (MMSE) multiuser receiver for uniformly quantized synchronous code division multiple access (CDMA) signals in additive white Gaussian noise (AWGN) channels. The input-output relationship of the quantizer is represented by the gain-plus-additive-noise model. Based on this model, we derive the weight vector and the output signal-to-interference ratio (SIR) of the MMSE receiver. The effects of quantization on the MMSE receiver performance is characterized in a single parameter named "equivalent noise variance" which is a function of the sum of each active user's signal-to-noise ratio (SNR), processing gain, and the number of quantization levels. The optimal quantizer stepsize which maximizes the MMSE receiver output SNR is also determined. Simulation results validate the accuracy of our analysis.     

Digital MF Receiver Using Discrete Fourier Transform

In a digital toll switching office a digital multifrequency (MF) receiver may be more economical than the present analog MF receiver. This paper suggests an algorithm that could be used for digital implementation of such a receiver. The algorithm employs discrete Fourier transform and leads to more efficient design than a system using second-order digital bandpass filters. The presented results of computer simulation of the digital MF receiver employing this method indicate satisfactory performance and good immunity to random noise interference.     

用于双星时差频差定位体制的宽频接收机设计

针对双星时差频差定位体制要求,提出了一种宽频带接收机设计方法。介绍了整机架构设计方案和模块划分方法。重点阐述了影响双星时频差体制定位精度的关键指标:时延差一致性、频率差一致性、幅度差一致性的工程实现方式及各项技术指标的加速老化试验方式。接收机测试结果表明,接收机时延差一致性优于1.54 ns、频率差一致性优于1 Hz、幅度差一致性优于0.5 dB。并通过老化试验验证接收机指标变化情况满足在轨5年实际工程应用需求。     

利用编解码芯片的无线收发电路

无线数字信号传输由于抗干扰性强,在电子产品中得到广泛应用,若配以编码和解码功能,便可以更好地处理工程中经常遇到的多点测量需要区分不同探点的问题。介绍一种利用编解码芯片PT2262／2272的单片机控制电路,并分析了电路构建中所传输数据时序的处理过程,以利于编制软件时进行正确的设置,加快程序的编写速度;结合无线收发模块F05C／J04E的使用及实际电路设计中遇到的问题,给出了设计中需要重点关注的技术环节和电路调试时需要注意的事项。