Showing papers on "Radio wave published in 2001"

Cardiovascular magnetic resonance

Abstract: Cardiovascular magnetic resonance (CMR) creates images from atomic nuclei with uneven spin using radio waves in the presence of a magnetic field. Full details of the physical principles can be found elsewhere [1]. For clinical purposes, MR is performed using hydrogen-1, which is abundant in water and fat. Radiofrequency waves excite the area of interest to create tissue magnetization, which decays (relaxation) and after a short period is induced to release energy as a radio signal. These echoes are converted using Fourier transformation into images of spatially resolved radio signals. Relaxation is quantified in spatially orthogonal directions as T1 and T2, which allows tissue characterization, thus creating a powerful clinical tool. A CMR scanner consists of a superconducting magnet, a radiofrequency transmitter and receiver connected to radio aerials, and gradient coils driven by powerful pulses of electricity to create transient magnetic fields. The imaging computer triggers to the electrocardiogram and runs scanning sequences that coordinate the complex processes.

Antenna apparatus and electronic toll collection system and electronic toll collection method using the same

Abstract: In an antenna apparatus and the electronic toll collection (hereinafter, abbreviated to an ETC) system using it, an antenna apparatus ( 2 ) is provided in a space over a lane ( 3 ) through which an automobile ( 1 ) having ETC on-vehicle equipment ( 10 ) passes. An antenna which the antenna apparatus has radiates a radio wave having a radio beam emitted area ( 21 ) of a radio wave to communicate with the ETC on-vehicle equipment and, thereby, electronic toll collection is performed for the passing automobile. It is an object of the present invention to provide an antenna apparatus which is controllable so that the ETC on-vehicle equipment is in the center of the radio beam emitted area of the antenna apparatus, and also to provide an ETC system using it. The antenna apparatus integrates an antenna and a light emitting unit. The light emitting unit emits a visible light ( 31 ) to the radio beam emitted area for communicating with the ETC on-vehicle equipment 10 mounted on the automobile along the center line within the radio beam emitted area. A sensor ( 40 ) can detect the automobile and can determine an emitted period of the visible light.

Development and use of a GPS ionospheric scintillation monitor

Abstract: Global Positioning System (GPS) satellite signals provide convenient radio beacons for ionospheric studies. Among other propagation phenomena, the ionosphere affects GPS signal propagation through amplitude scintillations that develop after radio waves propagate through ionospheric electron density irregularities. This paper outlines the design, testing, and operation of a specialized GPS receiver to monitor L-band amplitude scintillations: the Cornell scintillation monitor. The Cornell scintillation monitor consists of a commercial GPS receiver development kit with its software modified to log signal strength from up to 12 channels at a high data rate (50 samples/s). Other features of the receiver include the optional assignment of a channel to monitor the receiver noise level in the absence of signal tracking and the means to synchronize measurements between nearby independent receivers to perform drift measurements and correlation studies. The Cornell scintillation monitor provides characterization of the operational L-band scintillation environment and additionally permits study of the multipath environment of a static antenna, GPS scintillation monitors can provide information about the state of ionospheric irregularities for pure research purposes as well. Their strength lies in the fact that they are inexpensive and compact and therefore can he readily proliferated. Even a single scintillation monitor can supplement radar spatial coverage of irregularities in a limited way because it monitors several satellite lines of sight simultaneously.

Noninvasive measurements of chemical substances

Abstract: A contact device (2) placed on the eye in order to detect physical and chemical parameters of the body as well as the non-invasive delivery of compounds according to these physical and chemical parameters, with signals being transmitted continuously as electromagnetic waves, radio waves, infrared and the like.

Calibration of low-frequency radio telescopes using the galactic background radiation

Abstract: We consider the calibration of flux densities of radio bursts from decametric to kilometric wavelengths using ground-based and space-based data. The method we derive is applicable to low-frequency radio telescopes where galactic background radiation is the principal contribution to system temperature. It can be particularly useful for telescopes of low angular resolution observing spectra of radio bursts from the Sun and the planets because absolute calibration of these telescopes is very difficult with conventional techniques. Here we apply the method to observations from about 7 to 47 MHz that were made on the ground with the Bruny Island Radio Spectrometer located in Tasmania, Australia, and those from about 20 kHz to 13.8 MHz were made with the radio experiment WAVES on the WIND spacecraft. The spectrum of the galactic background radiation from $ 30$ MHz has been carefully measured with low-resolution telescopes, starting more than a decade ago. We use this known spectrum to calibrate both BIRS and WAVES on an absolute scale. The accuracy we achieve is about a factor of two, whereas the flux densities of solar and planetary radio sources vary by many orders of magnitude. Our method permits inter-calibration of ground-based and space-based observations, and allows corrections to be made for instrumental uncertainties on both radio experiments. In addition, on the ground, it allows the spectra to be corrected for ionospheric absorption and partial ground reflections. As an application we show the spectrum of a solar type III burst observed from 47 MHz to 20 kHz. Its flux density was largest, $S\approx 10^{-17}$ W m -2 Hz -1 , at about 3 MHz, while at 60 kHz and at 47 MHz it was lower by a factor of about 300.

Measuring, modeling, and characterizing of indoor radio channel at 5.8 GHz

Abstract: Wide-band indoor radio channel characterization for broadband radio access networks and unlicensed national information infrastructure has been performed at 5.8 GHz, and results are given in this paper. Delay spreads of 8.8 and 17.2 ns and coherence bandwidths of 9.6 and 4 MHz have been found for line-of-sight (LoS) and obstructed line-of-sight (OLoS) situations, respectively. Results have been compared with predictions made using a ray-tracing tool. To get accurate predictions, a good description of the electromagnetic properties of the obstacles present in the environment is needed. Several experiments were made in order to characterize the electromagnetic parameters of six typical building materials. Transmission and reflection coefficients were measured using the free-space technique. A multiple successive internal reflection model was used to estimate the permittivity and conductivity by comparing the measured and predicted values of the coefficients. Several samples of each material were measured, and the results vary from sample to sample. This variation has been characterized by the calculation of confidence bands for the parameters. The influence of both the dielectric parameters and the order of reflections considered in the ray-tracing tool has been analyzed. The effect is reduced on narrow-band predictions but is more important on wide-band parameters as the delay spread. It is shown that the measured delay spread cumulative distribution function falls within the band predicted using the measured maximum and minimum values of permittivity.

Mobile communication system

Abstract: A mobile communication system including a plurality of base stations arranged in a communication area each for emitting a radio wave inherent thereto and a mobile station moving in the communication area and communicating with respectives of the base stations via the transmitted radio waves. There is previously stored a location correlation data group including correlation data representing correlation situations of a plurality of arriving radio waves produced by the transmitted radio waves at respectives ones of a plurality of sampling locations within the communication area as location correlation data in correspondence with the respective locations. Upon reception of the arriving radio waves at a current location of the mobile station, there is calculated current correlation data representing correlation situations among the received arriving radio waves for the respective mobile station. There are compared the location correlation data in the location correlation data group and the current correlation data, and then the current position of the mobile station is determined in accordance with a result of the comparison and the determined current position data is generated.

System for determining the heading and/or attitude of a body

Abstract: A system for determining the heading and/or attitude of a body receives radio waves from a plurality of position-fixing satellites using at least three antennas fixedly mounted at different positions of the body. To reliably obtain integer ambiguity solutions of carrier phases of the radio waves in a shorter time, the system directly determines integer ambiguities from attitude angle data obtained by an IMU attitude processing section when the integer ambiguities are to be redetermined in the event of an interruption of the received radio waves or a change in the combination of satellites to be used. This system provides a user with highly accurate uninterrupted heading and/or attitude angle information.

Antenna apparatus and portable communication apparatus

Abstract: In an antenna apparatus proposed by the present invention, two inverted-F antennas having the same characteristics are supplied with power with phase difference of 180 degrees respectively. Therefore only radio wave of polarized wave in a predetermined direction can be radiated and deterioration in antenna characteristics due to leak currents can be prevented.

ULF waves with drift resonance and drift-bounce resonance energy sources as observed in artificially-induced HF radar backscatter

Abstract: . HF radar backscatter which has been artificially-induced by a high power RF facility such as the EISCAT heater at Tromso has been demonstrated to provide ionospheric electric field data of unprecedented temporal resolution and accuracy. Here such data are used to investigate ULF wave processes observed by the CUTLASS HF radars. Within a short period of time during a single four hour experiment three distinct wave types are observed with differing periods, and latitudinal and longitudinal phase evolution. Combining information from the three waves allows them to be divided into those with a large-scale nature, driven externally to the magnetosphere, and those with small azimuthal scale lengths, driven by wave-particle interactions. Furthermore, the nature of the wave-particle interactions for two distinct small-scale waves is revealed, with one wave interpreted as being driven by a drift resonance process and the other by a drift-bounce resonance interaction. Both of these mechanisms with m ≈ -35 and proton energies of 35–45 keV appear to be viable wave energy sources in the postnoon sector. Key words. Ionosphere (active experiments; wave-particle interactions) – Magnetospheric physics (MHD waves and in-stabilities).

Position detection system

Abstract: PROBLEM TO BE SOLVED: To detect the position of a radio transmitter indoors with high precision, in a system for specifying the position of the moving radio transmitter. SOLUTION: This system is constituted from one or more transmitting stations having means for modulating a radio wave having a frequency determined beforehand, and transmitting a characteristic label number, three or more transmitting/receiving stations having means for modulating the radio wave having the frequency determined beforehand with the characteristic label number, and transmitting it, means for receiving the transmitted radio wave, means for measuring the reception electric field intensity of the received radio wave, and means for discriminating the characteristic label number from the received radio wave, and installed on the known positions determined beforehand, a data management means connected to the three or more transmitting/ receiving stations, for managing the reception electric field intensity and data of the characteristic label number as a pair, and a position calculation means for calculating the positions of the transmitting stations by using the data managed by the data management means.

Radio wave absorber

Abstract: There is disclosed a thinner-layered radio wave absorber having high absorption performance for a high frequency electromagnetic wave. The radio wave absorber, even when having a magnetic layer of not more than 1 mm in thickness, achieves satisfactory absorption characteristics for the high frequency electromagnetic wave by adopting a structure that a conductor is fixedly attached to a face opposite to an electromagnetic-wave incident face of the magnetic layer of single-layered structure, and also arranging the magnetic layer to have values of a real part μ′ and an imaginary part μ″ of complex relative magnetic permeability of the magnetic layer satisfying an expression of μ″≧mμ′−n (m: real number of m>0, n: real number of n≧0) outside an impedance mismatching region.

Joint EUV/Radio Observations of a Solar Filament

Abstract: In this paper we compare simultaneous extreme ultraviolet (EUV) line intensity and microwave observations of a filament on the disk. The EUV line intensities were observed by the CDS and SUMER instruments on board SOHO and the radio data by the Very Large Array and the Nobeyama radioheliograph. The main results of this study are the following: (1) The Lyman continuum absorption is responsible for the lower intensity observed above the filament in the EUV lines formed in the transition region (TR) at short wavelengths. In the TR lines at long wavelengths the filament is not visible. This indicates that the proper emission of the TR at the filament top is negligible. (2) The lower intensity of coronal lines and at radio wave lengths is due to the lack of coronal emission: the radio data supply the height of the prominence, while EUV coronal lines supply the missing hot matter emission measure (EM). (3) Our observations support a prominence model of cool threads embedded in the hot coronal plasma, with a sheath-like TR around them. From the missing EM we deduce the TR thickness and from the neutral hydrogen column density, derived from the Lyman continuum and He i absorption, we estimate the hydrogen density in the cool threads.

Correlation of solar energetic protons and polar cap absorption

Abstract: This study shows the results of a model of polar cap absorption events (PCAs) using solar energetic proton flux as an input. The proton data are recorded by the Charged Particle Measurement Experiment (CPME) on board the IMP 8 satellite and are collected by the Applied Physics Laboratory at Johns Hopkins University. The IMP 8 satellite orbits the Earth at distances between 30 and 35 Earth radii, which places it in the solar energetic particle environment throughout most of its orbit. It has been shown in previous studies that these solar energetic particles have direct and immediate access to the polar atmosphere [Reid, 1970]. Our model shows that the majority of the ionization resulting from the influx of solar energetic protons occurs in the altitude range from ∼ 50–90 km. Excess ionization at these altitudes causes enhanced absorption of cosmic HF radio waves. The levels of absorption used for comparison in this study were measured directly by the riometer at South Pole station, Antarctica. The results show a very strong correlation between the incident proton flux and measured path-integrated cosmic HF radio noise absorption for significant events, involving absorptions greater than 1.0 dB. For absorption levels lower than this it is obvious that other phenomena dominate. For HF radio waves the primary contributors to PCA are protons with energies near 20 MeV. This study extends the correlated observations of interplanetary particles and PCA throughout a 9-year period. The close quantitative agreement between the measured and calculated values of absorption supports the validity of the assumptions and suppositions made by this model. The data also suggest a method by which the path-integrated cosmic noise absorption may be used to probe the E and D layers of the ionosphere to determine the effective ion-electron recombination coefficients within these regions.

Method and apparatus for perforating a well

Abstract: A method and apparatus for perforating tubular members coaxial outside and inside surfaces with a continuous wall extending therebetween attaches at least one explosive charge in direct contact with the wall of the tubular with at least one detonation device in communication with the explosive device. A control station in wireless and cableless communication with the at least one detonation device selects from radio waves, infrared waves, acoustic waves, optical light waves, seismic waves, and combinations thereof to activate the at least one detonation device.

Authenticating method for short-distance radio devices and a short-distance radio device

Abstract: The invention provides a method for making mutual authentication between short-distance radio devices automatically or after confirmation by users, and a short-distance radio device for realizing the method. In a condition where a plurality of radio devices exist, each of the radio devices comprising a data communicating unit for performing short-distance radio communication and an authenticating unit for performing authentication of the radio device, the authenticating unit performs mutual authentication between two radio devices automatically or after confirmation by users of the radio devices when the two radio devices come closer to each other to such an extent that coverage areas of radio waves generated by the radio devices overlap with each other.

Gamma-Ray Pulsars

Abstract: In 1967 a new radio telescope was commissioned in England. A group of astronomers under the direction of Anthony Hewish at the University of Cambridge had completed this receiver system to study the newly discovered quasi stellar radio sources and the rapid scintillations that result when radio waves from distant cosmic point sources pass through the turbulent interstellar and interplanetary plasma. One goal was to study the properties of these cosmic plasma clouds, and the sensitive receiver at 81.5 MHz was therefore fitted with a high-speed recorder. The intensity of celestial sources passing over the fixed field of radio receivers was recorded on strip charts and had to be analyzed by visual inspection. This task fell naturally to the graduate student of the group, Jocelyn Bell. On August 6, 1967, she first noticed a peculiar train of radio signals when the sky at right ascension 19hl9min passed through the field of view. What could have caused such a transient periodic signal? The first suspicion was of course interference from some electric equipment, like the ignition of a passing car or a satellite. But to the surprise of Bell the signal appeared again at about the same time of day.

Tire condition monitoring apparatus and method

Abstract: In detecting which transmitter of several of transmitters has transmitted a radio signal based on digital data from an RF circuit, a main controller of a receiver consecutively sends activation commands to each of several control circuits such that only one of the control circuits is activated at a time. The main controller detects which of the antennas corresponds to the control circuit that was activated when the voltage level signal from the RF circuit was lowest, and judges that the detected antenna is closest to the transmitter that transmitted the radio wave. As a result, the power consumption is reduced, and the transmitter that transmitted the radio wave is accurately detected.

Radio communication system, base station, mobile station, transmission control method and program storage medium

Abstract: PROBLEM TO BE SOLVED: To provide a radio communication system which uses both PDMA and CSMA methods and can improve the frequency usage efficiency. SOLUTION: While a base station 2 transmits a second radio wave Scs towards the incoming direction of a first radio wave Sup, mobile stations 3 conduct carrier-sensing to the second radio wave Scs, and transmit the first radio wave Sup only when they do not receive the second radio wave Scs. According to this arrangement, simultaneous transmission by mobile stations 3 each other, which cannot separate signals because of small direction difference from the base station 2, is prevented, and space division multiplex is conducted to mobile stations 3 each other, which have large direction difference from the base station 2. Hence, the frequency usage efficiency can be improved. COPYRIGHT: (C)2003,JPO

Possible mechanism of the over-horizon reception of FM radio waves during earthquake preparation period

Abstract: Kushida noticed anomalous over-horizon reception of FM radio waves (-80MHz) before earthquakes when epicenters were in a certain sensitive region. The suggested method of earthquake prediction recognizes precursors in supposedly back-scattered waves from the ionosphere several days or few weeks before the seismic events. We try to clarify the possible underlying physical mechanism for this method within the framework of existing notions on the lithosphere-atmosphere-ionosphere coupling. Gravity waves in the atmosphere are speculated to be generated by quasi-periodic movements of tectonic blocks or yield of gases along faults. Conversion of large-scale gravity waves above a seismically active region into ionospheric disturbances involves formation of sporadic E-layer. The sporadic E-layer in turn may be regarded as a free energy source of generation of small-scale (a few meters) ionospheric plasma irregularities, presumably due to the modified gradient-drift plasma instability. These meter-range irregularities could be the reason for the back-scattered VHF radio waves. Some experimental tests for verification of this hypothesis are suggested.

Cosmic birefringence within the framework of heterotic string theory

Abstract: Low energy string theory predicts the existence of an axion field which can lead to cosmic birefringence. We solve the electromagnetic wave equations in the presence of such an axion and a dilaton field in order to determine their effect on the polarization of light. We find that the presence of dilaton field leads to a nontrivial modification of the final result. We comment on the possibility of discovering such an effect by observations of radio wave polarizations from distant radio galaxies and quasars. We have also determined the limits on the string theory parameters that are imposed by the current radio polarization data.

Alien Vision: Exploring the Electromagnetic Spectrum with Imaging Technology

Abstract: This work takes readers on a visual tour of the electromagnetic spectrum beyond the range of human sight, using imaging technology as the means to see invisible light. It explains the light spectrum - from gamma rays to the longest radio waves, and including visible light - and the technologies that create images from the spectrum. Applications ranging from fire fighting and law enforcement to botany and medicine are discussed in detail.

Portable telephone set

Abstract: PROBLEM TO BE SOLVED: To provide a portable telephone set provided with an antenna which reduces the influence of radio waves on a human body and suppresses a polarization loss due to the difference of planes of polarization of incoming radio waves even in the case of an actual speech communication. SOLUTION: This portable telephone set has the first antenna part 16 which has a radio part inside a housing 11 having a microphone 13 and a speaker 12 and is fixedly arranged at the upper part of the housing 11 and where the first antenna element that is connected to the radio part and has the electrical length of about 1/4 wavelength in an operation frequency, and a plate-shaped antenna part 17 to be excited which is arranged slidably on the rear side face of the housing 11, crossing almost orthogonally with respect to the arrangement direction of the microphone 13 and the speaker 12 and has internally the second antenna element having the electrical length of about 1/2 wavelength, and when the second antenna element is pulled out, the second antenna element is excited by being subjected to capacitance coupling with the first antenna element.

Vehicular occupant motion detection system using radar

Abstract: System and method for determining occupancy of a vehicle in which a radar system emits radio waves into an interior of the vehicle in which objects might be situated and receives radio waves and a processor coupled to the radar system determines the presence of any repetitive motions indicative of a living occupant in the vehicle based on the received radio waves such that the presence of living occupants in the vehicle is ascertainable upon the determination of the presence of repetitive motions indicative of a living occupant. Repetitive motions indicative of a living occupant may be a heart beat or breathing as reflected by movement of the chest. The processor may be programmed to analyze the frequency of the repetitive motions based on the received radio waves whereby a frequency in a predetermined range is indicative of a heartbeat or breathing.

Radio communication unit

Abstract: PROBLEM TO BE SOLVED: To transmit/receive radio waves with high directivity and to shield the radio waves especially to the head direction of a user, when a radio communication unit is applied to a portable telephone set. SOLUTION: The radio communication unit which transmits and receives radio waves is provided with a wiring board for mounting antenna 1, a chip antenna device 50, having a loop antenna-like conductor 23 and is mounted on the antenna fitting position 5 of the wiring board 1 and a shielding member 30, arranged on the wiring board 1 side of a face confronting the conductor 23 of the chip antenna device 50. The radio waves from the conductor 23 to the direction of the wiring board 1 can be shielded, and the radio waves can be transmitted/received with high directivity.

Observations of 50- and 12-MHz auroral coherent echoes at the Antarctic Syowa station

Abstract: Data on 50- and 12-MHz E region coherent echoes from approximately the same directions and in a broad range of azimuths are available for 1995–1997 radar observations at the Antarctic Syowa station. One event of such observations is considered to compare power and Doppler velocity of echoes at these significantly different frequencies. For the considered event, Doppler velocities of more than 600 ms−1 (as recorded at both radar frequencies) were observed. We show that even though the 50-MHz echoes exhibit strong flow angle variation of the power, the 12-MHz echoes do not. Apparent aspect angle power attenuation is found to be 10 and 2.5 dBdeg−1 at 50 and 12 MHz, respectively. Measured Doppler velocities along specific radar directions are found to be comparable in spite of the significant difference in radar frequencies, with the velocity ratio V50MHz/V12MHz being in between 1.6 and 0.9 for high velocities of more than 400 ms−1. The velocity ratio varies with slant range and azimuth of observations. Ionospheric propagation effects for radio waves and plasma physical effects for irregularities are considered in an attempt to explain several observed features, for example, the echo power and velocity ratio variations with slant range.

Antenna for reducing unwanted radiation

Abstract: PROBLEM TO BE SOLVED: To transmit only electric waves of the necessary frequency and attenuate radio waves of unwanted frequency in an antenna for reducing unwanted radiation SOLUTION: A frequency selective plate material 1 is arranged on the front surface of an array antenna 20 In the frequency selective plate material 1, a plurality of holes are opened in an array form and a metal piece 11 is fitted thereinto Of signals S0 input to the array antenna 20, radio waves S1 of a use frequency is transmitted through a dielectric plate material 12 for radiation, and unwanted frequencies of the radio waves of frequencies and the are reflected or absorbed by a plurality of metal pieces 11 for attenuation, to form a significantly reduced radial pattern S3 as compared to a conventional radiation S2

Portable radio device

Abstract: A portable radio device which effectively prevents the property of transmission of radio waves from being degraded due to the user's body, is disclosed. A housing of the portable radio device has a lower end portion shaped to protrude from the major surface of the housing and taper down towards the lower end of the housing. An antenna is provided within the lower end portion.

Radio communication apparatus, radio communication system and stationary station

Abstract: In a mobile radio communication system, a base station is provided for executing radio communication with a radio communication apparatus. The radio communication apparatus includes a signal transmitting/receiving apparatus for mobile communication, which transmits and receives a signal to and from the base station. The apparatus also includes a Bluetooth unit for short-range radio data communication using relatively week radio waves. When the radio communication apparatus is located at a distance communicable with a stationary station based on the Bluetooth system, the radio communication apparatus can acquire, from the stationary station, position information indicative of its position, and shop information related to the position information, etc. Thus, the short-range radio data communication system using week radio waves enables the mobile radio communication system for mobile phones to calculate the position of the user of the radio communication apparatus, and also to distribute information relevant to the position.