Propagation measurements for UHF spread spectrum mobile communications

The U.S. Army is currently developing a number of spread spectrum radio systems to support its needs for more survivable and efficient mobile UHF data distribution on the tactical battlefield of the 1990's and beyond. The analysis and prediction of the performance of these systems in mobile tactical environments has been met with a great deal of uncertainty relating to the applicability of narrow-band propagation models and the effects of terrain irregularity and vegetation on broad-band signals. An overview is presented of an ongoing Army program utilizing wide-band pulse response measurements to characterize ground mobile tactical UHF spread spectrum propagation channels. Recently acquired experimental data are used to demonstrate the potential of this program for improving available tools for prediction and analysis of tactical UHF spread spectrum systems employing bandwidths of hundreds of MHz.     

Rayleigh fading channels in mobile digital communication systems.I. Characterization

When the mechanisms of fading channels were first modeled in the 1950s and 1960s, the ideas were primarily applied to over-the-horizon communications covering a wide range of frequency bands. The 3-30 MHz high-frequency (HF) band is used for ionospheric communications, and the 300 MHz-3 GHz ultra-high-frequency (UHF) and 3-30 GHz super-high-frequency (SHF) bands are used for tropospheric scatter. Although the fading effects in a mobile radio system are somewhat different than those in ionospheric and tropospheric channels, the early models are still quite useful to help characterize fading effects in mobile digital communication systems. This tutorial addresses Rayleigh fading primarily in the UHF band. That affects mobile systems such as cellular and personal communication systems (PCS). Part I of the tutorial itemizes the fundamental fading manifestations and types of degradation     

全集成低噪声CMOS宽带分数分频频率综合器

设计了一款应用于CMMB数字电视广播接收的全集成低噪声宽带频率综合器。采用三阶ΣΔ调制器小数分频器完成高精度的频率输出,使用仅一个低相位噪声的宽带VCO输出频率范围覆盖900~1 600 MHz,产生的本振信号覆盖UHF的数字电视频段(470~790 MHz)。设计中的频率综合器能在所有的频道下保证环路的稳定以及最小的环路性能偏差。测试结果表明,整个频率综合器的带内相位噪声小于-85 dBc/Hz,并且带外相位噪声在1MHz时均小于-121 dBc/Hz,总的频率综合器锁定时间小于300μs。设计在UMC 0.18μm RFCMOS工艺下实现,芯片面积小于0.6 mm2,在1.8 V电源电压的测试条件下,总功耗小于22 mW。     

3 300~3 400 MHz频段无线电定位与LTE室内 覆盖系统同频共存分析

2015年世界无线电大会（WRC-15）的1.1议题（AI 1.1）正在开展关于新增频谱用于未来移动通信的相关研究。3 300~3 400 MHz频段具有较宽带宽,此频段适于移动宽带系统在密集城区提供高速数据传输业务,满足移动宽带系统对于频谱容量的需求。我国在这一频段目前主要存在无线电定位业务。本文分析了如果在3 300~3 400 MHz频段引入IMT室内系统,保护已有无线电定位业务所需的隔离要求。     

Channel Requirements for a Cordless Telephone Spectrum Allocation

Planning for a permanent cordless telephone spectrum allocation requires that the number of channels necessary to meet the long-term needs of cordless telephones be estimated. To provide the analytical basis for such an estimate, we determine the relationship between the number of channels available to cordless telephones and their performance in a suburban residential environment. Multiple cordless telephones in a community can use the same channel simultaneously, so performance ultimately will be limited by cochannel interference. We therefore develop a mathematical model of the carrier-to-interference ratio. This model accounts for shadowing, polarization, and multipath propagation effects observed in field measurements, as well as the random locations of cordless telephones. A performance measure is developed and evaluated for cordless telephones that can access all available channels and are operating in a suburban residential environment. The results indicate that for carrier frequencies in the low UHF band (300 MHz to 1 GHz), an allocation of 30-40 duplex channels can accommodate universal use of cordless telephones in that environment. For lower carrier frequencies, shadowing is less severe and fewer channels would be necessary. For example, at 50 MHz, 20 duplex channels would suffice.     

High TX-to-RX Isolation in UHF RFID Using Narrowband Leaking Carrier Canceller

Ultra-high frequency (UHF) radio frequency identification (RFID) system suffers from large leakage of the carrier due to insufficient TX-to-RX isolation. A narrowband leaking carrier canceller (LCC) for UHF RFID is proposed to enhance the isolation. Hardware realization is carried out based on simulation model in ADS (Advanced Design System). Measurement results indicate that the TX-to-RX isolation is improved from 20 dB to above 40 dB within UHF RFID frequency band of 920–925 MHz. Upper limit of increase in isolation versus amplitude and phase distortion are also presented and discussed.      

UHF television interference associated with cellular mobile telephone systems

An investigation is made into two types of interference which may occur between UHF television and 850 MHz cellular mobile telephone systems: 1) ITV--interference to the cellular mobile telephone receivers, created by a UHF TV transmitter; 2) TVI--interference to the UHF TV receiver, created by the cellular system mobile transmitters. In the case of ITV it has been determined that TV transmitters operating on TV channels 65 through 69 may produce third-order intermodulation, within a radius of about 0.5 mi, to certain telephone channels assigned to mobiles operating in a cellular system fringe area. A judicious choice of telephone channel assignments would mitigate this type of degradation. Alternatively, in the case of TVI, it is shown that within a minimum grade B television service area, it is possible for cellular mobile telephones to at times produce image interference to present-day UHF TV receivers tuned to channels 58 through 61. However, because of cellular telephone subscriber density and channel position (and loading) the probability of interference is expected to be low. An increase of TV receiver image rejection by 20 dB would essentially eliminate all likelihood of this interference.     

The NHTSA emergency medical services communications program

The expansion of emergency medical services is limited by residual problems of inadequacy of communications systems developed using insufficient and inadequate VHF frequency channels. The promise of correcting these inadequacies by making available a block of UHF channels for use with a common frequency allocation structure is being diluted by short-sighted planning permitted by inadequacies in applicable FCC rules. There is a need to revisit Docket 19880 to consider issuance of additional rules needed to foster the most effective use of the block of UHF frequency channels available for emergency medical services. Technology is available which offers promise for application to expand the coverage of EMS communications with appropriate concessions to cost-effectiveness. Before much additional investment is made, in improving or expanding EMS communications, it is necessary that the coordination of system planning is improved. Improved coordination in federally funded projects is required but is not sufficient to prevent unnecessary and detrimental diversity in EMS communications systems implementation. There is also a need for state level supervision of local level EMS communications system planning and implementation to assure that all elements of the system, regardless of funding source, are compatible, interoperable, and in compliance with statewide plans.     

Terrestrial Broadcasting Changes at the 1979 World Administrative Radio Conference

Because all of the countries attending the 1979 World Administrative Radio Conference (WARC-79) are substantially involved in broadcasting, the discussion of broadcasting and related subjects at WARC-79 developed top level interest. The changes in the terrestrial broadcasting bands as the result of the WARC-79 negotiations were for the most part positive. Objectionable interference was removed from the LF band; the MF band in Region 2 was expanded by 110 kHz; the FM Aural broadcasting band in Region 1 was expanded by 8 MHz; some of the less usable frequencies in the Low VHF TV band were eliminated, but TV broadcasting frequency allocations were added to the High VHF band to compensate. In the use of the UHF TV band, the United States proposal to share the band on a primary basis with fixed and mobile services created substantial controversy, which lead to a reservation on the part of the United States Government. In addition to the expansion of the MF band by 110 kHz in Region 2, a proposal was made to the Region 2 MF Regional Administrative Radio Conference to adopt a 9-kHz channel spacing so the channel spacing in all three Regions would be identical. It was the proposal of the USA to use the additional channels generated by 9-kHz spacing for minority ownership, educational ownership, and to provide full-time schedules for daytime-only stations. The controversy over this change is far from being resolved, and it can be expected to be an important topic of the second meeting of the Region 2 MF Administrative Radio Conference. Plans for a High Definition broadcasting system at 12.0 GHz are also discussed.     

一种面向卷烟包装新型超高频rfid标签天线设计

本文设计了一种新型的抗金属无源UHF射频识别(RFID)印刷标签天线.该天线可以应用在卷烟包装上,仿真和实测数据证明,在915MHz处天线的阻抗为(20+j149)Ω,能和Alien Higgs -2芯片很好的实现共轭匹配.该标签天线的工作带宽为31MHz,通过RFID阅读器实测表明,所设计的标签天线读取距离可达到0.8m.     

UHF Integrated Power Amplifiers

This paper describes the development of integrated UHF power amplifiers using thin-film lumped elements and UHF power-transistor chips. Single-stage hybrid amplifier modules capable of delivering output powers up to 20 watts CW in the frequency range of 225-400 MHz are reported. In addition, broad-band hybrid amplifiers are discussed with 1-dB bandwidths of up to 40 percent in the same 225-400 MHz band. These amplifiers are presently housed in a three-terminal stud-mounted module, 0.8-inch high, 0.65-inch wide, and 0.35-inch deep. The module has a 50-ohm-impedance input lead, a 50-ohm-impedance output lead, and a dc lead (grounding is through the stud). Gain and output powers significantly greater than those available from a single module are obtained by cascading and/or paralleling individual modules at their 50-ohm terminals, either directly or by means of power combiners and power dividers. By use of the latter approach, a 76-watt amplitier having a gain of 15.8 dB at an operating frequency of 350 MHz has been constructed.     

Error correction/masking for digital voice transmission over theland mobile satellite system

The development of a 2400-b/s speech digitizer which provides an acceptable level of intelligibility and quality over land mobile satellite channels is described. Performance tests over simulated channels in the UHF band (800 MHz) are presented. The voice digitizer is a linear prediction (LPC) vocoder which uses a channel error correction and concealment procedure tailored to error statistics for a minimum-shift keyed (MSK) downlink to a moving vehicle. The error-handling technique is based on perceptual criteria and utilizes the parametric nature of LPC representation of speech. A single-error-correcting, single-burst-detecting (28, 20) fire code is shown to be the best choice for the application. The intelligibility of the vocoder is measured and compared to the standard LPC-10 algorithm. The major remaining sources of speech quality degradation due to channel errors are determined and ranked     

Design of an Ultra‐Compact UHF Passive RFID Tag Antenna for a Medical Sample Tube

In this letter, a small‐sized ultra‐high frequency (UHF) RFID tag antenna for a medical sample tube is proposed. The RFID tag antenna is designed and fabricated based on the circular loop antenna used in the UHF band (Korea standard, 917 MHz to 923.5 MHz). The tag antenna size is reduced using a circular meander stub. The antenna has a physical size of 8 mm, which is about λ/40 in electrical length. The proposed tag antenna is molded into a medical sample and multitag identification is performed.     

Deployment of Cognitive Radio in India

Cognitive radio is much talked as solution to limited spectrum resource. Provisions for deployment of cognitive radio have already been made in most of the EU countries, USA and Canada. It has not yet been introduced in India. This paper describes the frequency allocation for different services in Indian national frequency allocation plan. and frequency bands in which cognitive radio can be permitted in India. This paper gives an overview about what initiatives should be taken by the regulator to introduce cognitive radio in India. The paper concludes that UHF band (300 MHz–3 GHz) is good candidate for cognitive radio system.     

室分系统的动态频谱共享方案

动态频谱共享为运营商在室分系统低频段下实现5G NR覆盖层创造了无限可能,同时,室分系统的动态频谱共享还为运营商免去了频谱重耕或购买新频谱许可证的高昂成本,有助于将LTE用户群平稳过渡到5G,并更快推出独立组网模式.探讨了动态频谱共享的背景、部署以及关键技术方案,主要技术方案有MBSFN子帧方案、LTE打孔方案和NR打...     

基于HMM和平衡二叉树递归搜索的宽带频谱感知

为了使得二级或无许可证用户在给定宽带上获取空闲的子带以供使用,针对认知无线电中的宽带频谱感知技术进行研究,提出一种有效的宽带频谱感知算法。算法采用隐马尔可夫模型(HMM)对初级用户的动态行为进行建模,以克服目前宽带感知技术的局限性;其次,利用现有窄带感知技术,将感知频带划分为较小的频道,将其建模为一棵平衡二叉树,并对频谱孔洞进行递归搜索。如果检测到有孔洞在频率上相邻,则将它们合并成一个单一的频谱孔洞,使得认知二级用户的容量在整个频带上最大化。仿真实验结果表明,与现有宽带频谱感知方法相比,提出的宽带频谱感知算法具有更好的感知性能增益和更强的鲁棒性。     

Low loss and high performance SAW filters for 800 MHz mobile telephone transceiver

Low loss surface acoustic wave (SAW) filters have been developed for use in the radio frequency circuits of the mobile telephone transceiver. Both the UHF (800 MHz) and VHF (90 MHz) band-pass filters have exhibited high performance, and the employment of the SAW filters has shown advantages in UHF/VHF circuit integration for mass production.     

基于UHF频段及微波段分型天线研究

针对工作在UHF频段和微波频段的RFID系统(射频识别系统)要求,设计满足915MHz和2.45GHz多频特性的分型天线,提出采用方形Sierpinski毯结构。针对目前分型天线谐振频率所成的1∶3∶9的特性分析,并对天线部分参数改变,并对二阶毯型贴片天线进行开槽分析研究,提高天线性能,对高频部分降频以达到系统所要求915MHz和2.45GHz的中心频率,达到谐振频率的同时并保证理想的10dB回损带宽。     

Macro cellular network transition from traditional frequency range to 28 GHz millimeter wave frequency band

The target of this article is to analyze the impact of transition from cellular frequency band i.e. 2.1 GHz to Millimeter Wave (mmWave) frequency band i.e. 28 GHz. A three dimensional ray tracing tool “sAGA” was used to evaluate the performance of the macro cellular network in urban/dense-urban area of the Helsinki city. A detailed analysis of user experience in terms of signal strength and signal quality for outdoor and indoor users is presented. Indoor users at different floors are separately studied in this paper. It is found that in spite of considering high system gain at 28 GHz the mean received signal power is reduced by almost 16.5 dB compared with transmission at 2.1 GHz. However, the SINR is marginally changed at higher frequency. Even with 200 MHz system bandwidth at 28 GHz, no substantial change is witnessed in signal quality for the outdoor and upper floor indoor users. However, the users at lower floors show some sign of degradation in received signal quality with 200 MHz bandwidth. Moreover, it is also emphasized that mobile operators should take benefit of un-utilized spectrum in the mmWave bands. In short, this paper highlights the potential and the gain of mmWave communications.     

Omnidirectional transmitter combining antenna

Historically, it has been difficult to combine transmitters which are closely spaced in frequency onto the same omnidirectional antenna. Two principal techniques have been used: cavity combining and transmission line hybrid combining. When using cavities, the minimum separation is limited by the amount of insertion loss that is acceptable and by the frequency stability of the cavities. In the 800- MHz land mobile frequency band, cavity combining has been used to combine transmitters as closely spaced as 0.5 MHz with 3 dB of insertion loss. When combining transmitters separated less than 0.5 MHz, hybrid combining has been used. When two transmitters are combined using this technique, half of the power of each is dissipated into a matched load. Further, each time the number of transmitters being combined is doubled, an additional 3 dB is added to the insertion loss. A new technique has been developed which utilizes transmission line hybrids to combine the transmitters, but which does not suffer from large insertion loss. The power that was previously dissipated in the resistive load is radiated in a manner that produces an omnidirectional pattern. The antenna and network that accomplish this combine signals with 90° phase shifts. Measurements show that it is possible to combine eight transmitters arbitrarily close in frequency with 35 dB of isolation between adjacent channels, less than 0.5 dB insertion loss, and with horizontal pattern circularity better than ±3 dB. Additionally, this technique can be combined with cavity combining to maintain high isolation between additional tranmitters.