250MHZ单边带接收机前端电路的设计与实现

为了有效地抑制各种干扰,提高甚高频单边带接收机性能,关键是有一个性能良好的前端电路.就这一问题,文章介绍了前端电路在甚高频单边带接收机中的作用和研制250MHZ单边带接收机前端电路的设计方法,同时给出了实验结果,结果表明各种干扰被有效地抑制了.     

超外差接收机的噪声系数

分别讨论了在理想假设和实际情况下超外产左接收机的双边带噪声系数和单边带噪声系数,给出了单边带接收机的某些设计方案。     

单边带通信接收机中高中频方案的研究与实现

单边带信号在短波频段内十分拥挤,因此要接收单边带信号就需要一个高抗干扰的通信接收机,过去由于器件的落后,直接影响先进方案的实施.当今先进的器件已经出现,根据用户的需求设计了采用一次变频、高中频方案的单边带通信接收机.文中对该方案的抗干扰特点进行了分析,具体设计中遇到匹配、高增益中放级联、抗干扰的工艺技术等棘手问题,并提出了解决办法,最后给出了系统的测试结果.     

单边带移动通信的单音导频

在国外,移动通信发展得很快,频谱很紧张,故单边带移动通信的呼声很高,不久的将来我国也必然会出现类似的情况。单边带要应用于甚高频甚至于超高频频段,必需插入导频。本文首先介绍了单边带的优点和几个有争议的问题,得出单边带是用于移动通信的一种好的调制方式的结论。然后主要就几种单音导频的插入方案进行了比较,并提出了部分音频频谱倒置的带内单音导频方案。     

新型五频段语言保密器

谭多脱克(Datotek)近来提供一种在电话电路上,单边带或甚高频/特高频无线电路上语言绝对保密的动态变更的五频段语言保密器。     

甚高频民用移动电台的单边带调制

鉴于甚高频移动电台通信的日益普及,可用频率分布越来越拥挤,这正成为某些地区的主要问题。有人提出,在比较窄的波道间隔内采用单边带调制来解决这一问题。本文简要地研究了这一解决办法的实质,比较了单边带调制与其它通用调制方式的主要特点,同时,讨论了单边带的实施问题。     

高效甚高频线性放大器——用于松鸡系统无线线路

引言在无线电频谱中,引进了有效带宽的调制系统(如单边带),使晶体管在高频—30兆赫频段中进行有效线性功率放大的能力得到提高。目前,很多新设计的甚高频通讯线路所采用的调制系统能提供恒定的带宽,但设备复杂。已发现的适用于甚高频的这样一种调制     

单边带和独立边带技术(二)

三、单边带接收机1.有八个频段及其他扩展频段的短波调谐器的电路概述在格龙迪希公司的“卫星—2000”型仪器中的短波—调谐器把,5～30MHz的短波置于八个频段中交叠,其中无线电广播覆盖整个频段。     

宽带镜频抑制混频器设计及实现

雷达和通信接收系统中,采用镜频抑制混频器能够有效抑制镜像频率,提高系统的抗干扰能力.在介绍镜像干扰原理的基础上,给出了一种镜频抑制混频器的框图,该结构既能在接收机中作为镜频抑制混频器,还能在发射机中作为单边带调制器.设计制作了一个S频段镜频抑制混频器,测试结果显示在S频段内镜频抑制度大于20 dB,单边带抑制度大于20 dB,很好地抑制了镜像频率以及边带.     

频带压缩和扩张系统

在发射机和接收机的整个系统中,音频信号调制一个射频信号,已调信号经滤波产生一个具有给定频宽的单边带信号,采用单边带信号同只有该信号频宽几分之一的信号混频、外差的方法,对单边带频宽进行压缩,由此获得的频带被压缩了的单边带信号经由线路传输到接收机.在接收机里,采用一个较高频率的信号同接收到的单边带信号混频外差的方法以及采用从接收机输入端得到的一个信号同该较高频率信号混频、外差方法,把单边带信号的频宽扩展到原来未被压缩时的信号频宽.这个系统容许传输一个频宽为最初调制信号频宽1/4的单边带信号.     

Phase-Locked Transparent Tone-in-Band (TTIB): A New Spectrum Configuration Particularly Suited to the Transmission of Data Over SSB Mobile Radio Networks

The paper describes a new pilot tone SSB configuration, transparent tone-in-band (TTIB), which may be used in mobile radio systems from low-band VHF to microwave frequencies. By utilizing audio signal processing techniques in the transmitter and receiver, the pilot reference tone may be positioned centrally within the RF channel bandwidth without losing the property of data transparency and also retains the many system advantages of tone-in-band SSB over the pilot carrier and tone-above-band schemes. Besides speech transmissions, results are presented for noncoherent FSK and DPSK data formats under white noise and Rayleigh fading conditions. Finally, a new technique utilizing TTIB is suggested to facilitate the use of coherent data systems.     

A real zero SSB transceiver for land mobile radio: A simple method of demodulating SSB signals without an envelope

A real zero single sideband (RZ SSB) transceiver is newly proposed for mobile radio services. The necessary transmission bandwidth of RZ SSB is similar to that of a conventional SSB. In this new transceiver, an amplitude limiter, which can remove the amplitude impairment, can be used without degrading the quality of detected output signals in the receiver. Furthermore, since RZ SSB signals possess FM-like characteristics, they can be demodulated with frequency detection as well as product detection.     

Theoretical and experimental investigation of feedforward signal regeneration as a means of combating multipath propagation effects in pilot-based SSB mobile radio systems

A technique is described, feedforward signal regeneration (FFSR), to combat the effects of multipath propagation on VHF and UHF pilot tone single sideband (SSB) mobile radio systems. Unlike feedforward automatic gain control (FFAGC), FFSR suppresses both the random amplitude and phase fluctuations in the received signal. Extensive laboratory and field tests have shown that the operation of SSB at UHF frequencies is a viable proposition for both speech and data communication.     

一种超宽带雷达系统接收前端的实验研究

较详细地介绍了一种VHF/UHF频段超宽带接收前端的设计,实验系统带内具有良好的线性相位和幅度平坦特性,文中给出了接收前端及主要部件研制结果的性能指标。     

Interference-free assignment grids. I. Basic theory

A mathematical method using linear algebra is developed for generating interference-free simplex channel assignment grids for base stations in the VHF land mobile band for large urban areas. The frequency assignment model checks for interference from adjacent channels, desensitization, transmitter intermodulation, and receiver intermodulation. The basic philosophy of the model is presented, and the required electromagnetic compatibility computations are reviewed. Both single-frequency and multiple-frequency (sharing) assignment strategies are described     

A 200-350-GHz Heterodyne Receiver

A low-noise heterodyne receiver for the 200-350-GHz region has been developed and used in astronomical observations. Two-room temperature mixers cover this range, with local oscillator (LO) power provided by frequency multiplied klystrons. A single crossed waveguide multiplier design covers the entire range, and is found to provide adequate output power by either doubling or tripling. Signal-LO diplexing is done with a quasioptical diplexer based on a Martin-Puplett interferometer. The best system sensitivities obtained with the two mixers have been 2100 K SSB at 242 GHz and 2900 K at 285 GHz.     

一种船舶自动识别系统甚高频信道的低成本设计

随着船舶自动识别系统(AIS)市场竞争的日益激烈,低成本化是AIS产品研制的必然趋势。根据国际海事组织(IMO)有关标准,给出了一种AIS甚高频(VHF)信道的低成本设计方案。介绍了AIS工作原理及其VHF信道的工作过程,给出了简洁实用的发射机和接收机设计,并对调制器、VHF功放、解调器等核心单元设计方法、器件选择进行了详细阐述。测试和外场实用表明该VHF信道各项指标均已达到规定要求,并且该VHF信道硬件成本低,性能可靠。     

Superconductor-Insulator-Superconductor Mixers for the 2 mm Band (129-174 GHz)

We present the design, construction and performance of backshort-tuned Single Side Band (SSB) and of fixed-tuned Double Side Band (DSB) Superconductor-Insulator-Superconductor (SIS) mixers covering the frequency range of 129-174 GHz (2 mm band). Receivers employing these SSB mixers have been continuously operated for astronomical observations on the six antennas of the IRAM Plateau de Bure Intereferometer (PdBI) since 2007 and on the IRAM 30 m Pico Veleta (PV) radio telescope since 2009. The DSB version of the mixer was employed in a prototype of a four-element focal plane array that was tested on the IRAM 30 m radio telescope. Both SSB and DSB mixers employ the same chip and are based on a wideband single ended probe transition from WR6 full-height waveguide to thin-film microstrip line and on a series array of two Nb/Al-AlO_x/Nb junctions. The measured receiver noise for the four-element DSB mixer array pumped by a Gunn oscillator cascaded with a frequency doubler was in the range 25-35 K across the 135-168 GHz LO band. The PdBI and PV receivers equipped with the SSB mixers have measured noise temperatures in the range of 30 K to 60 K and an image sideband rejection below -10 dB over the 129-174 GHz RF band. The measurement results agree well with the predictions obtained through detailed simulations of the SIS receivers based on the standard theory of quantum mixing.     

Low Altitude Propagation Effects — A Validation Study of the Advanced Propagation Model (APM) for Mobile Radio Applications

VHF signal strength data from two NOAA weather radio transmitters, located in southern California and southwestern Arizona, were collected over a wide range of topography ranging from relatively flat to mountainous terrain. Signal strength data were collected using a mobile receiver traveling from 20 km to over 100 km, with the receiving antenna at a constant height of 2.2 meters above the ground. Meteorological information was obtained from local radiosonde measurement stations at Miramar (NKX) and Yuma Proving Ground (1Y7). This data is used as the basis for a validation study of the Advanced Propagation Model (APM) to determine its applicability for low altitude mobile radio communications applications over terrain.