Large-signal characterization of dual-gate field effect transistorsusing load-pull measurements

An automated injected signal load-pull measurement system has been designed to operate from 8 to 12 GHz, with a range of injected signal power extending to 4 W. The system has been shown to be as accurate as the HP8510 network analyzer. The large signal intrinsic drain-to-source resistance of an 1800 μm dual-gate FET was measured on the load-pull system, and subsequently a variable power amplifier was designed using the load-pull data. The output phase variation of the variable power amplifier was 10° when operating at 31.3 dBm     

Digital terrestrial television (COFDM 8K system) field trials andcoverage measurements in Spain

This article presents the results of the first digital terrestrial television field trials and coverage measurements in Spain. First of all the VIDITER project is presented. The main objective of this work is to study the behavior of a whole digital terrestrial television network, from source coding up to the final signal reception. At this point, the experimental network installed in Madrid is described. Next, the measurement campaign is explained, first, by describing the network configuration used for these first field trials, and then, paying attention to the criteria used to select the measurement points and the parameter set to be tested. Some of the results obtained are shown as a first approach to the figures needed to develop and plan a fully operational digital terrestrial television service     

Frequency-resolved measurements for the characterization of MOSFETparameters at low longitudinal field

A new technique is presented to extract the main parameters required for transistor modeling at low longitudinal fields (parasitic resistance, intrinsic conductivity factor, threshold voltage, and body factor k) from a single MOSFET. The method makes use of easy-to-perform AC frequency-resolved measurements to overcome repeatability and accuracy problems encountered with DC data. The technique has been satisfactorily validated on MOSFET's down to 0.8 μm channel length     

广播电视四题断想

一、生产力与生产关系 从2000年起．广播电视曾一度以组建集团为抓手，大力推进体制改革。     

Local-area field strength variation measurement of the digitalterrestrial television signal (COFDM 8K) in suburban environments

This paper presents the results of a field measurement campaign at the experimental COFDM 8K digital terrestrial television network developed by the partners of the VIDITER project in Madrid (Spain). This article focuses on the field strength spatial variation distribution inside small coverage areas. Due to the fact that the distribution parameters strongly depend on the survey area type, during this first stage the only environments taken into account have been those traditionally considered as suburban     

Channel characterization using bispectral analysis

A method of characterizing a slowly varying linear channel in the presence of white Gaussian noise is proposed. The method uses a non-Gaussian probing signal and performs a bispectral analysis of the received signal     

数字水印技术分析及其在电视领域的应用

数字水印是多媒体版权保护的一种有效技术手段。介绍数字水印技术的基本原理,阐述了视频数字水印应具有的特点,讨论压缩域视频数字水印算法。在此基础上,提出数字水印在电视领域的应用方案。该技术为电视版权管理的有效实施具有一定的借鉴作用。     

数字水印技术分析及其在电视领域的应用

数字水印是多媒体版权保护的一种有效技术手段.介绍数字水印技术的基本原理,阐述了视频数字水印应具有的特点,讨论压缩域视频数字水印算法.在此基础上,提出数字水印在电视领域的应用方案.该技术为电视版权管理的有效实施具有一定的借鉴作用.     

Electric field measurements in klystron cavities

A qualitative comparison is made between computed and measured electric fields in typical TM010klystron cavities. The computer code LALA is shown to apply effectively to cavities with offset gaps which are difficult to solve analytically, and a bead-pull technique using a highly directive perturbing needle is utilized to verify the theoretical results. The magnitude of the radial field components is discussed as well as the shape of the axial field resulting from shaping the drift tube noses and offsetting the gap.     

Standard probes for electromagnetic field measurements

Discusses various standard antennas for measuring radio-frequency electric and magnetic fields. A theoretical analysis of each antenna's receiving characteristics is summarized and referenced. The standard probes described are an electrically short dipole, a resistively-loaded dipole, a half-wave dipole, an electrically small loop, and a resistively-loaded loop. A single-turn loop designed for simultaneous measurement of the electric and magnetic components of near-fields and other complex electromagnetic environments is also described. Each type of antenna demonstrates a different compromise between broadband frequency response and sensitivity     

Home telecare system using cable television plants - anexperimental field trial

To solve the inconvenience of routine transportation of chronically ill and handicapped patients, this paper proposes a platform based on a hybrid fiber coaxial (HFC) network in Taiwan, designed to make a home telecare system feasible. The aim of this home telecare system is to combine biomedical data, including three-channel electrocardiogram (ECG) and blood pressure (BP), video and audio, into a National Television Standard Committee (NTSC) channel for communication between the patient and the healthcare provider. Digitized biomedical data and output from medical devices can be further modulated to a second audio program (SAP) subchannel which can be used for second-language audio in NTSC television signals. For long-distance transmission, we translate the digital biomedical data into the frequency domain using frequency shift key (FSK) technology and insert this signal into an SAP band. The whole system has been implemented and tested. The results obtained using this system clearly demonstrated that real-time video, audio, and biomedical data transmission are very clear, with a carrier-to-noise ratio of up to 43 dB     

毫米波室内传播的场强测量

介绍了毫米波室内传播的场强测量。通过对测量的数据进行处理,可得无论使用全向天线还是定向天线作为接收天线,路径损耗指数都约等于２。慢衰落的累积概率分布符合对数正态分布。快衰落的累积概率分布在没有直达波的民政部下符合瑞利分布,而在有直达波的情况下,如果使用全向天线则趋向瑞利分布,使定向天线符合莱斯分布。     

Channel characterization and modeling for Ka-band very smallaperture terminals

An increasing number of commercial applications are being promoted for future Ka-band satellite communication systems. Many of these systems will involve low-margin very small aperture terminals (VSATs). These systems are subject to important atmospheric propagation degradations that affect the quality of transmission and the link availability. The objective of this paper is to characterize the Ka-band channel and evaluate the performance degradation in VSATs resulting from atmospheric propagation, impairments. In particular microwave propagation through a turbulent atmosphere is discussed, and the statistical characterization and modeling of tropospheric scintillation is reviewed. Moreover, the paper extends the method proposed by Filip and Vilar (1990) for the long-term characterization and modeling of the combined effect of rain impairments and scintillation. Specifically, the increase in noise temperature during rain events is added to the Filip-Vilar model. This leads to a five-parameter global fading distribution that is used to predict typical Ka-band satellite link outage time, the mathematical formalism is illustrated by applying the method to the selected case of the Advanced Communications Technology Satellite (ACTS)-Georgia Tech experimental downlink. Numerical results confirm that both rain impairments and scintillation are important factors in the design of Ka-band VSAT systems     

DVB-T BER measurements in the presence of adjacent channel andco-channel analogue television interference

This paper presents some laboratory tests carried out to measure the BER degradation caused by an analogue PAL-G television interference on a COFDM 8 K digital television signal. The tests made include co-channel and both upper and lower adjacent channel interference situations. Previously, the ITU-R has presented some protection ratios to be sought when planning DVB-T networks. The results of the work presented here include a wider range of power ratios and their effect on the BER rather than the limit protection values. The new digital services will share the same frequency bands as the conventional analogue television so the exact characterization of mutual interference is a major concern of broadcasters during the transition period when both systems have to co-exist     

An improved HF field strength prediction method

A multi-correlation process for reducing the RMS error between the field strength values predicted by the use of the method laid down in Report 894.2 (1991) and the values of Databank.D1 is described. Three functions are used. The first function has 1080 coefficients describing 10 distance ranges, 4 solar activity ranges, and 27 frequency to MUF ratio ranges. The second function covers 10 distance ranges and 24 local time data in the mid path with a total of 240 coefficients. The third function has 720 coefficients covering 10 distance ranges, 6 modified dip angle values, and 12 months. With the use of these functions, the final RMS error is 7.69 dB for the whole set of circuits of Databank.D1 database and 7.29 dB for short paths. The Report 894.2 method has a RMS error of 10.1 dB. Four plots are included to compare that method with the improved method     

Indoor field strength prediction based on FMM

1 Introduction With the popularization of personal communication service (PCS), indoor radio propagation has attracted more attention, especially for ultra-wideband (UWB) signals. Ultra-wideband communication systems have very high data rates (at least 10…     

Buried object detection and location estimation fromelectromagnetic field measurements

A translation property is derived describing the field scattered from a known buried object placed at distinct locations. The result is used to derive the optimum algorithm for detecting the known buried object and estimating its location from noisy scattered electromagnetic field measurements