Radio Repeater Research Articles

간섭제거기를 적용한 디지털 RF 시스템에 관한 연구

본 논문은 이동 통신 시스템에서 서비스 품질을 개선하고 기지국의 서비스 영역을 확장하기 위한 중계기 시스템 중 기존 RF 중계기가 가지고 있는 간섭 및 궤환 신호를 제거하기 위해 간섭 제거기를 적용한 디지털 RF 시스템에 관한 연구를 수행하였다. RF(Radio Frequency) 중계기에 DSP(Digital Signal Processing)와 FPGA(Field Programmable Gate Array)를 이용한 디지털 엔진을 탑재하여 간섭 및 궤환 신호를 제거하는 새로운 방식의 무선 중계기를 제안하였다. DSP와 FPGA로 이루어진 디지털 ICS(Interference Cancellation System) 엔진은 RF 회로와 일체형으로 설계되었으며, 디지털 플랫폼을 통해 하드웨어를 개발한 뒤 최적에 중계기 시스템에 적용하기 위해 일체형으로 설계 및 제작하였다. 논문에 적용된 간섭 및 궤환 신호 제거 기법으로는 LMS(Least Mean Square) 알고리즘을 적용한 적응형 IF(Intermediate Frequency) 방식을 적용하였으며, 개선된 수렴 속도와 성능을 가지게 되었다. In this paper, in order to improve a service quality and to broaden the service coverage in the mobile communication system a study on a digital RF repeater employed with an Interference Cancellation System(ICS) is performed. The digital RF repeater employed with an ICS is implemented to remove interference and feedback signals which are disadvantages of a conventional(or general) RF repeater. This thesis presents the design and experiments of the new wireless repeater. The proposed wireless repeater consists of a RF repeater mounted with digital engine. The digital ICS engine consists of a DSP and FPGA. The digital engine and RF circuit are designed into a one-piece. After developing hardware through the digital platform they are also designed and fabricated into a one-piece in order to apply a best performance repeater system. The method of removing interference and feedback signals is an adaptive IF technique employed with a LMS algorithm. The powerful performance and fast convergence speed is obtained by using this method.

An Interference Cancellation Scheme for Mobile Communication Radio Repeaters

An interference cancellation (ICAN) scheme for mobile communication radio repeaters is presented. When a radio repeater has a gain that is larger than the isolation between its transmit and receive antennas, it oscillates due to feedback interference signals. To prevent feedback oscillation of a radio repeater, we first formulate a feedback oscillation model of the radio repeater and then derive an ICAN model from that model. From the derived ICAN model, we show that the stability and the signal quality of the repeater depend on the repeater's gain and delay, the propagation delay on feedback paths, feedback channel characteristics, and the capability of the feedback channel estimation algorithm. It is also shown that the stability condition of the repeater does not guarantee the quality of the repeater's output signal. To guarantee repeater's stability and signal quality, an ICAN scheme based on an iterative algorithm is subsequently proposed. The simulation results confirm the relationship between the stability and signal quality of the repeater and the impact of the aforementioned factors. Using the proposed ICAN scheme, a mean error vector magnitude (quality indicator) of about 6.3% for the repeater's output signal was achieved.

Connectivity, Power, and Energy in a Multihop Cellular-Packet System

In this paper, we study a large network of subscriber stations (SSs) with certain common wireless capabilities and base stations (BSs) having direct connections to the wired infrastructure in addition to common wireless capabilities. SSs can communicate with the outside world only through the BSs. Connections to SSs without a direct (i.e., a single hop) wireless connection to any BS are established, if possible, through other SSs serving as wireless repeaters. The locations of the SSs and the BSs follow independent homogeneous planar Poisson processes. The propagation channels exhibit signal attenuation with distance and log-normal shadowing. We evaluate exactly the probability of an SS to have a direct wireless connection to any of the BSs and a lower bound on the t-hop (t arbitrary) outage probability of an SS. We then define the minimal hop-count routing algorithm and calculate the mean number of hops for routes connecting SSs to BSs, when a maximum hop-count constraint is imposed. We compute next the probability distribution of the transmit power under the assumption of perfect power control. We conclude by calculating a bound for the total mean transmit energy required to transfer a data packet from an SS to a BS over a minimal hop-count route and show that this energy is significantly lower than the corresponding value in a single-hop network operating at the same outage probability

Integrated maritime portable acoustic scoring and simulator control and improvements

The invention comprises an improved portable maritime scoring and simulation system that comprises three or more buoys that are deployed in an area of water selected for maritime combat training. Attached to each buoy are a GPS receiver, an RF radio system, an acoustic analysis system, and a microprocessor. The acoustic analysis system is designed to capture an acoustic signature of ordnance impacting the water with predetermined characteristics. The system includes an RF radio repeater system linked to a system controller to control and monitor the elements of the system. When an acoustic signature is captured by the acoustic analysis system, the RF radio system transmits the time of the capture and the GPS location of the buoy to the RF radio repeater linked to the system controller. When three or more buoys transmit a captured acoustic signature, the system controller computes the location of impact using a location process.

Photovoltaic/wind turbine - a comparative study for coastal areas

Wind and solar energy are both to a large extent affected by the changes in the weather ie they are weather dependent, especially wind. Other factors which have an influence are the change in the earth's declination angle combined with the atmosphere. More regional phenomenon having an effect are features such as mountains and the sea. To determine the effects of different factors a dual system was established to monitor the effectiveness of a photovoltaic array and a wind-driven generator system. This aim was achieved by simulating a radio repeater.

Early warning system for aftershocks

A prototype early warning system to provide San Francisco and Oakland, California a few tens-of-seconds warning of incoming strong ground shaking from already-occurred M ≧ 3.7 aftershocks of the magnitude 7.1 17 October 1989 Loma Prieta earthquake was operational on 28 October 1989. The prototype system consisted of four components: ground motion sensors in the epicentral area, a central receiver, a radio repeater, and radio receivers. One of the radio receivers was deployed at the California Department of Transportation (CALTRANS) headquarters at the damaged Cypress Street section of the I-880 freeway in Oakland, California on 28 October 1989 and provided about 20 sec of warning before shaking from the M 4.5 Loma Prieta aftershock that occurred on 2 November 1989 at 0550 UTC. In its first 6 months of operation, the system generated triggers for all 12 M > 3.7 aftershocks for which trigger documentation is preserved, did not trigger on any M ≦ 3.6 aftershocks, and produced one false trigger as a result of a now-corrected single point of failure design flaw. Because the prototype system demonstrated that potentially useful warnings of strong shaking from aftershocks are feasible, the USGS has completed a portable early warning system for aftershocks that can be deployed anywhere.

Long‐range recording of vibroseis data: Simulation and experiment

Long‐range recording of COCORP vibrators was undertaken in the Adirondacks using a radio repeater to retransmit the vibrator start‐up code at ranges up to 100 km. A number of events were recorded at a range of 47 km; these events correspond to reflections from depths of about 9, 13, 16, 20, and 24 km and a possible Moho reflection from 40 km might be present. Simulation of VIBROSEIS recording demonstrates that low‐level signals with a S/N as low as 0.05 may be extracted from noise even though reflections have amplitudes less than the least significant bit. Such wide‐angle VIBROSEIS recording is practical and necessary in crustal reflection studies for defining the Moho and other deep reflectors.

Thin-film injection-locked oscillators and negative-resistance amplifiers for 2-GHz radio repeater

Injection locked oscillators (ILO) used as amplifying stages in a solid-state FM microwave radio repeater are presented. Circuit performances needed for such an application and design criteria used to obtain these performances are given. Two ILO modelling possibilities are analyzed and compared. Similarity between positive feedback model and negative conductance model is shown for circuits with a single resonator. Then the equivalence is extended to a more complex arrangement useful to increase the performances of the practical realization. The first model is still used to study the ILO overall performance and the second model to design the actual circuit. Tunnel-diode ILO with second-order passive network is described giving circuit design criteria and experimental results. Transistor negative conductance linear amplifiers are presented with a procedure for computer aided design of the passive network imbedding the active device. The result of the entire active network is a one-port circuit exhibiting a negative conductance constant with frequency in the whole tuning band. Transistor ILOs are obtained by means of a matching network between circulator and the negative conductance amplifier. Mention is made to the active stages implementation into thin-film microstrip configuration referring alumina thin-film technology.

Frequency division with low FM distortion

The FM distortion properties of a fast frequency dividing flip-flop are measured and are found to be very low and suitable for use in a new type of solid-state microwave radio repeater.

Ultra reliable submerged repeaters : W. J. Archibald, Electron. Equip. News. February (1968), p. 46

Although still expensive, silicon solar cell arrays are becoming increasingly common for some specialised remote area applications. Within Australia solar photovoltaic generators are being used to provide power for microwave radio repeater stations, VHF subscriber radiotelephone systems, UHF small capacity radio systems, as well as many other professional and commercial applications. In all of this plant it is vital to be able to provide reliable low maintenance primary power. A new generation of low power consumption communication equipment has made it possible to completely power broadband radio relay repeaters using only the solar source with power storage being provided by storage batteries of the pure-lead positive pasted-plate type. Several years of operational experience in remote locations have now been obtained with this solar generating equipment.

100A Protection Switching System

The 100a protection switching system is intended to ensure continuity of service in TD Microwave Radio Relay Systems by transferring service from a failed working channel to a standby protection channel. Switching is done at IF on a switching section basis. A switching section may contain up to ten radio repeater stations, with the average section containing three to four repeaters. A fully equipped 100A system provides means to replace any one of ten regular channels with either of two protection channels. Two regular channels may be switched simultaneously to the two protection channels. The circuit interruption due to a fade initiated or a maintenance switch is less than 10 microseconds. The interruption due to an equipment failure is less than 35 milliseconds, a time short enough to prevent false operations in the telephone switching plant. The control information necessary to sequence the operation of the switches at the transmitting and receiving ends of the switching section consists of coded voice-frequency tones. These may be transmitted over any reliable voice-frequency facility having suitable transmission and delay characteristics. All of the active devices in the system are solid state. The system requires sources of both +24 and −24 volt power.

Low-Cost Pole-Mounted VHF Radio Station for Bonneville Power Administration

This paper describes what is believed to be the nation's first completely transistorized pole-mounted 10-watt VHF land mobile radio repeater station powered by a combination rechargeable battery and thermoelectric generator unit. Over 2 years of field experience has been accumulated since this Station was installed December 7, 1962. The Unique power supply, which has been an unqualified success, comprises a 12-watt thermoelectric generator, a thermomotor which diverts the waste heat into the radio equipment cabinet at temperatures below 40°F, and a nickel-cadmium battery supply.

Waveguide communication system for centralized railway traffic control

A new microwave communication system for centralized train traffic control, utilizing TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</inf> mode propagating circular waveguide as a transmission line is discussed. A new microwave communication system for The system was developed for control of 100 ultra-high-speed trains on a railroad 500 km in length. The aluminum waveguide of 132-mm ID, with measured attenuation of 2.0 db/km on 7500-Mc band, with a helical waveguide as a mode filter at 100 m intervals is laid alongside the railroad. Signal transmission to the running trains is achieved through directional couplers in the circular waveguide and auxiliary waveguides for radiation, without signal dropout. Radio equipment for the trains and radio repeater features special simultaneous amplification of incoming and outgoing signals by the same TWTs, and varactor diode multipliers. The system consists of a total of 600 telephone channels to provide 6 telephone channels to each train, to be used for high-speed data transmission and telephones. A new microwave communication system for Experiments made with a waveguide run of 1 km in length laid alongside the Hachiko Line of the Japanese National Railways have proved its capability for centralized train traffic control. Codes transmitted at speed of 2000 bauds during the test train running had no error, and a total of 573,000 characters was transmitted. Good TV transmission was also attained.

The TH Radio Microwave Carrier Supply System

The TH microwave carrier supply system furnishes all of the carrier frequencies required at a radio repeater station. All the frequencies are harmonically derived from a common, highly stable, 14.82593-MC crystal oscillator, to avoid interference problems. Total reliance on a common generator of carriers for an entire station calls for a highly reliable and adequately protected carrier supply. To this end, a complete standby supply is arranged with fast automatic switching to replace the regular supply when needed. Special emphasis is placed on conservative circuit design, careful selection of components, adequate monitoring and trouble detection facilities, and provisions for routine maintenance.

Waveguide as a Communication Medium

The circular electric wave in round metallic tubing has an attenuation coefficient which decreases as the frequency of operation is increased. A corollary to this behavior is the fact that any preselected attenuation coefficient can in theory be obtained in any predetermined diameter of pipe through the choice of a suitably high carrier frequency. The attenuation which is characteristic of microwave radio repeater links, about 2 db/mile, is in theory attainable in a copper pipe of about 2″ diameter using a carrier frequency near 50,000 mc. Scale-model transmission experiments, conducted at 9,000 mc, showed average transmission losses about 50 per cent above the theoretical value. These extra losses were due to (1) roughness of the copper surface and (2) transfer of power from the low-loss mode to other modes which can also propagate in the pipe. The latter effect may have serious consequences on signal fidelity because power will transfer (at successive waveguide imperfections) from the signal mode to unused modes and, after a time delay, back to the signal mode. This effect has been studied experimentally and theoretically, and it is concluded that (1) either mode filters must be inserted periodically to absorb the power in the unused modes of propagation, or (2) the medium itself must be modified to continuously provide large attenuations for the unused modes of propagation. The latter approach is attractive in that it also provides a solution to the problem of bending this form of low-loss guide.

Experimental radio bearer equipment for carrier telephone systems

Two types of frequency-modulated radio bearer circuits are described, one operating in the frequency range of 420 to 470 Mc/s, and the other in the frequency range 860 to 960 Mc/s. Both systems are crystal controlled with a frequency deviation of ±180 kc/s and each capable of carrying 12 to 17 telephone circuits.The description includes a radio repeater operating on the heterodyne principle which permits long distances to be traversed with a minimum of accumulated noise and distortion. The performance of both systems meets C.C.I.F. transmission specifications when used with the appropriate carrier equipment. Various aspects of supervisory and order-wire facilities, together with alarm and automatic change-over equipment are discussed.A typical installation, operating in the 420–470 Mc/s band and consisting of a transmitter, repeater and receiver, is described and its performance over a 100-mile circuit is given.

A Microwave Communication Relay System

This paper describes the design of a microwave radio relay repeater suitable for use in communication systems requiring low distortion repeaters. The modulation bandwidth is approximately 500 km for the illustrated design. The repeater employs negative feedback, and features extreme simplicity of electrical and mechanical design.