Showing papers in "IEEE Transactions on Vehicular Technology in 1975"

A computer generated multipath fading simulation for mobile radio

Abstract: A brief description is presented of a computer simulation of the Rayleigh distributed fast fading encountered in mobile radio. This simulation should be of interest to all those whose studies involve parameters of a mobile system that interact strongly with the radio environment.

Computer prediction of field strength in the planning of radio systems

Abstract: The application of a method of predicting the field strengths from mobile radio base station transmitters and in radio links is presented, and the extension of the method to facilitate frequency assignment is outlined. The topographic data for a country are stored in a computer and programs are provided which predict the signal levels produced by a specific transmitter at points spaced 0.5 km apart. A further program enables a plotter to be used to derive signal level contours which can be overlaid on a map. The field strength prediction method is proving valuable in the siting of VHF base stations, in the reduction of field testing required for mobile systems, and in the study of possible areas of cochannel interference. It has also been extended to effect path calculations for point-to-point radio links. An extension of the cochannel interference study in which channel assignments are made by a logical procedure so as to maintain co-channel interference below some chosen level while making the minimum demands on the spectrum is outlined. The method described has potential applications in national frequency planning.

High capacity personal rapid transit system developments

Abstract: High capacity personal rapid transit (HCPRT) is a system concept which utilizes small, 4 to 6 passenger, vehicles at very short headways on exclusive guideway networks. The automatic operation of small vehicles at headways of 1 s or less presents a major technical problem which is amenable to a combination of design approaches. This paper explores the effect of basic parameters such as vehicle length, reaction time, emergency and failed vehicle deceleration rates, and emergency jerk rate on potential minimum operating headway. The results of this analysis are then discussed in the context of five HCPRT programs.

Optimum inductive loading of short whip antennas

Abstract: Short whips (monopoles) are often used on vehicles when a quarter wavelength is too long. It is common knowledge that a loading coil located in series with the whip improves narrow band performance. This series inductive loading of monopole (dipole) antennas is analyzed by a piecewise sinusoidal moment method. When loaded to resonance, the current rises from the feed value to a peak slightly beyond the load point with decay to zero at the end. Radiation resistance improvement factors as large as 5 have been calculated. The resonant loading reactance is shown to vary inversely with the antenna length for most lengths. Efficiency varies slowly with load point and peaks at roughly 0.4 (of the whip length) from the feed in contrast to earlier approximate theory that predicted higher efficiency for loads farther out toward the end. The curves allow a tradeoff between slightly reduced efficiency and larger input resistance (to allow easier matching) to be made. For this case, a 2/3 loading point may be a good compromise. The length for which efficiency is 50 percent is a useful design guide. This length varies slowly with Q and h/a and is in the range 0.06 to 0.09λ. Thus shorter monopoles will have low efficiency. Extensive graphical data are presented.

Mobile antenna gain at 900 MHz

Abstract: A program has been initiated to investigate the effect of the urban multipath environment on mobile antennas at 900 MHz. The program involves the constructuion of several mobile antennas, careful measurement of these antennas on an antenna range to determine their characteristics in a controlled environment, then measurement of their characteristics in the multipath environment of cities. Measured results are compared to computed results to permit generalized conclusions to be reached. This paper presents the results of the first phase of the program; measurements made in the controlled pattern range environment.

An ultrashort pulse radar sensor for vehicular precollision obstacle detection

Abstract: An ultrashort pulse radar sensor was designed, developed, and fabricated for an automotive hazard evaluation program. Tests verified that this unique system, which had a pulse duration of approximately 1 ns, did meet its design goals. Reflectivity characteristics of several road surfaces and RF scattering cross sections of selected highway objects were measured. Experiments verified the capability of the system to identify one object from another, even for a multiple object environment. An analytical model was developed that describes the Fresnel region scattering characteristics of simple objects.

Monitoring the combustion quality in internal combustion engines using the spark plug as a plasma probe

Abstract: A method of monitoring the quality of combustion in spark ignition gasoline engines using the spark plug's center electrode as a plasma probe is presented. Due to the ionized species remaining in the burned gases after combustion, a current is induced in a network attached to the spark plug's center electrode. The time dependence of this induced current is shown to correlate with the presence or absence and the time of occurance of the pressure component due to combustion in pressure transducer signals recorded simultaneously. Based on these correlations, three types of burns could be recognized from plasma probe signals: good burns, slow burns, and misfires. The specific correlation between the absence of a pressure component due to combustion and a corresponding absence of a plasma probe signal was used to form the basis for the operation of a one-channel engine misfire monitoring circuit.

A common momentum error in auto accident reconstruction

Abstract: Reconstruction of auto accidents can be performed in a number of ways, depending upon the experience and background of the reconstructionist. Two fundamental laws of physics can theoretically be used: conservation of energy and consemation of momentum. It has been the practice of some engineers to use both these laws when- ever possible, and in so doing they have neglected the transfer of mo- mentum to the earth immediately after impact before the impacted vehicle has changed ita motion. For example, consider one vehicle standing still while another crashes into it. During the first several hundredths of a second both vehicles will experience a crunching of metal structure, but only the moving vehicle will change its motion by slowing down somewhat as the stsnding-still vehicle remains motionless. The reawn for this standing vehicle not moving during the first several hundredths of a second is that the change in momentum of the moving vehicle is transferred through the wheels of the stationary vehicle to the earth because of the friction between tires and roadway. Equations for this two-car collision using conservation of both energy and momentum would be as follows:

Speed measurement through analysis of the Doppler effect in vehicular noise

Abstract: An alternative method of speed detection is presented based on the Doppler effect in vehicular noise. A procedure is developed to correlate the noise frequency spectrum as the vehicle approaches an observer with the spectrum as it moves away. Limitations of the technique are evaluated using empirical data obtained under typical traffic conditions. These results demonstrate that the Doppler shift can be extracted from automotive noise and related to the vehicle's speed. Although sources of inaccuracy are significant at lower speeds, a resolution of ±5 percent was easily achieved at 60 mph. Such a technique may be found useful in large scale traffic speed and density monitoring systems.

A practical approach to radio propagation measurements—As used in the design of mobile radio communications systems

Abstract: The design of a mobile or portable radio communications system requires the consideration of a number of unique engineering factors which do not necessarily apply to the design of a fixed, or point-to-point system. The design procedure is a combination of theoretical and empirical methods, which when taken with measured data, produce a system design meeting the required specifications. This paper will treat that portion of the system design pertaining to radio frequency propagation and system coverage. It stresses a realistic measurement program which will provide coverage data in support of the system design.