DTV (COFDM) SFN signal variation field tests in urban environments for portable outdoor reception

The paper presents the measurement results obtained in an extensive field test campaign developed in two large cities of Spain (Madrid and Bilbao) with the aim of characterizing the portable outdoor reception of digital terrestrial television (COFDM - coded orthogonal frequency division multiplexed) and continue the studies carried out by the authors during the past years.     

Field measurement based characterization of the wideband urban multipath channel for portable DTV reception in single frequency networks

This paper presents a study developed to obtain several parameters of the small scale fading of the wideband propagation channel applied to the portable and mobile reception of Digital Terrestrial Television (DTV) services in an urban Single Frequency Network (SFN) environment. The study is focused on the calculation of some relevant parameter values related to the multipath behavior of the channel, using field data collected in a real network. Mean values for the Root mean square Delay Spread (RDS) and the frequency domain Level Crossing Rate (LCR) are given, together with an analysis of the influence of the specific environment and network (SFN) features.     

Height gain measurements for DTV reception in Singapore

Very few height-gain measurements have been made especially in built-up areas. Measurements made in Singapore confirm that the height-gain is different in different locations and depends on the local clutter, ground reflection and the radiation pattern of the transmitting antenna. In high rise HDB (Housing Development Board) estates, height loss is observed instead of gain.     

The performance of antenna amplifiers used for terrestrial DTV reception

Measurements were made on currently available commercial antenna-mounted amplifiers to ascertain their effects on DTV reception. Data regarding amplifier gain and noise figure is presented, followed by data illustrating the effects of intermodulation within the tested amplifiers as shown by the change in the D/U interference ratio of a control DTV receiver, and ending with observations regarding amplifier environmental sensitivity. Also presented are the inconsistencies between the performance of commercially available amplifiers, advertised to the public for use with television, and the performance claims made by the manufacturers of such amplifiers.     

Planning factors for fixed and portable DTTV reception

The transition plan from the analog (NTSC) to digital terrestrial television (DTTV) in the USA was based on a simplified version of the Longley-Rice service prediction algorithm, and a link budget that mimicked the traditional planning factors for NTSC. It is now clear that the service prediction and the link budget both have serious shortfalls. This paper provides the formalism required for the development of realistic link budget and service grades for fixed and portable DTTV reception.     

Single frequency networks in DTV

Single Frequency Networks (SFNs) offer many advantages including better coverage, less interference, less power, and higher reliability. SFNs can also free up extra TV channels, resulting in more efficient use of the spectrum. The paper presents an overview of the advantages of SFNs and some basics about how to implement them. The significantly improved Signal to Interference performance and less radiated power in SFNs are derived from simple propagation models. Some potential problems that must be considered are discussed, including limitations due to receiver performance. Several simple formulas that should be helpful in quickly estimating and evaluating an SFN system are also presented. Finally, the likely implications of SFNs are covered, in particular the need for changed FCC rules and increased competition through a higher frequency reuse. The idea of the FCCs only limiting the power outside of the service area and letting the broadcasters decide on transmitter locations, number of transmitters and power levels is proposed.     

Using on-channel repeater to improve reception in DTV broadcasting service area

The paper presents the results of a series of tests performed by the Communications Research Centre Canada (CRC), to investigate the possibility of improving reception, by using an on-channel repeater (OCR), in areas already covered by an 8-VSB digital television transmitter. The results are then compared with those obtained at the same test locations using DVB-T transmission at various bit rates to study the impact of OCR versus reduced bit rate transmission. The results should show under which conditions it might be possible to use an OCR, instead of reducing the bit rate, to improve reception in parts of the coverage area of a main transmitter.     

Diversity reception in a multihop packet radio network

The performance improvement which results from the use of multiple antennas at each node in a multihop packet radio network is examined. Four transmission strategies based on three previously proposed routing schemes and one new routing scheme, MTP, are studied. It is found that the use of two antennas can improve the performance of all four transmission strategies by about 25% in a Rayleigh fading environment. The transmission strategy based on the MTP routing scheme is shown to be generally superior to those based on the other three routing schemes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Single-VCO multi-band DTV frequency synthesizer with a divide-by-3 frequency divider for quadrature signal generation

A multi-band frequency synthesizer for In-phase and Quadrature (I/Q) LO signal generation in Digital TV tuners is presented. Using divisor numbers other than powers of 2 (2 ⁿ ) for quadrature generation, reduces the required frequency range of the VCO, hence the number of VCO circuits, in multi-band frequency synthesizers. In the proposed synthesizer, VHF, UHF and L-band frequencies are covered with only one VCO. This is achieved by using a novel divide-by-3 circuit which produces precise I/Q LO signals. The VCO tuning range in this design is 2,400–3,632 MHz which is covered by a 6-bit switched-capacitor bank. A fast adaptive frequency calibration block selects the closest VCO frequency to the target frequency by setting the coarse-tuning code prior to the start of phase lock. A programmable charge pump is used to reduce variations in PLL characteristics over the frequency range. The synthesizer has been fabricated in a 0.18 μm CMOS technology and the die area is 1.7 × 1.6 mm². It consumes 27 mA from a 1.8 V power supply. Measurement results show operation of the proposed divide-by-3 circuit over the entire VCO frequency range. The synthesizer quadrature output phase noise for UHF and VHF bands is <−131dBc/Hz at 1.45 MHz offset.     

Diversity reception in a multihop packet radio network

The performance improvement which results from the use of multiple antennas at each node in a multihop packet radio network is examined. Four transmission strategies based on three previously proposed routing schemes and one new routing scheme, MTP, are studied. It is found that the use of two antennas can improve the performance of all four transmission strategies by about 25% in a Rayleigh fading environment. The transmission strategy based on the MTP routing scheme is shown to be generally superior to those based on the other three routing schemes. This revised version was published online in June 2006 with corrections to the Cover Date.     

数字电视中的频域频率同步技术

提出了一种宽带数字电视地面广播（BDB-T）系统的同步解决方案，重点研究了频域中的频率同步部分，通过对各种算法的仿真分析比较，给出易于实现、节省资源的频域频率同步算法并完成了相应的FPGA硬件电路设计，经BDB—T功能样机在实际无线环境中的传输测试，证明了算法及其电路的良好实际工作性能。     

CMMB单频网接收端网络监测点选择的分析

本文首先从理论和实际两个方面综合分析了单频网发射端可能出现的故障,通过仿真软件模拟发射端各类型故障,观察接收端相应发生的变化和产生不良接收的区域,从而在应用中通过接收端的实际情况判断发射端是否出现故障,以及出现故障的种类。     

Smart, active, and concealable antenna array for portable television reception

This paper describes an array which is concealable with a TV set or set-top box. The array is made of small active antennas which can provide space and polarization diversity by phase switching alone. The array can be manually or automatically controlled to maximize the signal-noise ratio of the desired channel and minimize the interference from undesired channels. The combination of automatically adjustable dual diversity and small physical size makes this device suitable for mobile reception.     

优化铁路GSM-R单网交织覆盖网络频率配置的研究

精心的频率配置,可提高铁路GSM-R无线网络的容量。文章分析了GSM-R单网交织覆盖网络的特点和目前的频率配置情况,探讨了以MAP技术优化单网交织覆盖的频率配置方案。     

单频网组网优化方法及复杂度分析

首先介绍了单频网覆盖的判定准则,其次针对地面数字电视广播单频网的组网优化问题,提出了一种基于遗传算法的优化方法,并分析了算法的复杂度,着重探究算法参数对算法性能的影响,从而确保在得到最佳优化结果的同时付出最小的代价.     

Broadband dual frequency sleeve monopole antenna for DTV/GSM applications

A broadband dual frequency sleeve monopole antenna for application in digital television (DTV) systems and global system for mobile communications (GSM) is presented. A parasitic inverted L-shaped strip and dual planar sleeve structure are introduced in the back ground plane for expanding the frequency band. The simulated and measured results show that the impedance bandwidth covers the DTV (470? 862 MHz) band and GSM (824?960 and 1710?2170 MHz) band with VSWR less than 2.5. An omnidirectional radiation property is also shown.     

Call performance in a frequency reuse digital portable radio system

A discrete-event stochastic simulation of many concurrent calls was used to generate signal-to-interference ratio (S/I) time histories and statistics on a time-division multiple-access (TDMA) uplink. The simulation integrates portable radio multiple access, uplink/downlink signal modeling, and the traffic process. Calls were held to completion, enabling observation of the effects of cochannel interference on time-dependent S/I statistics. It was found that the improvement obtained from measurement-based time-slot assignment in uplink S/I at access partially erodes over the life of a call, if it retains the time-slot assigned at the start. The amount and speed of erosion of S/I at the first percentile suggests that good transmission quality can be maintained for stationary users, with low overhead in the fixed radio network     

Autonomous adaptive frequency assignment for TDMA portable radiosystems

A simple autonomous procedure performed by each radio port (base station) to determine its own transmitting frequency is proposed. This procedure consists of signal strength measurements and an algorithm which selects the frequency with minimum interference from other ports. The algorithm converges rapidly while adapting to changes of operational conditions, such as installing new ports, which changes the system configuration, or adding new buildings, which causes different shadow fading. This method is significantly superior to a random assignment method both in resultant channel quality and in traffic-handling capability. For a regular-grid configuration, this method performs nearly as well as an a priori optimal frequency assignment method. It is also found that this assignment algorithm is robust against short-term signal fluctuations and it can be performed completely autonomously by each radio port     

单频He-Ne激光器中纵向非均匀磁场的应用

作者用高气压加纵向非均匀磁场的方法作了一系列单频输出的试验，成功地试制出了两台一米单频He-Ne激光器。本文报导了这些试验的数据和测试结果，并从理论上作了初步探讨．     

一种便携式无线收发信机的低噪声频率源设计

文中介绍了一种基于锁相环的低功耗、低成本、高性能、小体积,适用于无线收发信机的频率源的设计,重点分析了优化的环路带宽设计、环路滤波器、VCO(压控振荡器)的设计以及参考晶振的选取,提出了降低锁相环频率源噪声的方法,并根据此方法设计的频率源在实际应用中取得了良好的效果。