Showing papers on "Radio wave published in 1998"

Indoor non-volatile radio wave repeater

Abstract: PROBLEM TO BE SOLVED: To provide a non-directional indoor radio wave repeater for radio communication, which is easily prepared and low priced and further improves appearance while protecting an antenna in simple structure, for enabling radio communication without being disturbed by a radio wave obstacle even when at least one of rooms to be mutually communicated on both the sides of the radio wave obstacle is surrounded so as to disable communication by shielding radio waves for radio communication as it is. SOLUTION: In this indoor non-volatile radio wave repeater 1 composed of two antennas 2, a coaxial cable 3 and a connector 4 or the like so as to enable communication on both the sides of an indoor radio wave obstacle 5 such as a floor, wall or partition to shield radio waves, at least one of antennas 2 is provided inside an antenna box. The antenna box can be made into parallelopiped or prism. COPYRIGHT: (C)1999,JPO

The Observed Size and Shape of Gamma-Ray Burst Afterglow

Abstract: The detection of delayed emission in X-ray, optical, and radio wavelength, or "afterglow," following a γ-ray burst can be described as the emission of a relativistic shell decelerating upon collision with the interstellar medium. We show that the observed radiation surface has well-defined bright edges. We derive an explicit expression for the size as a function of time, and obtain the surface brightness distribution. This might be directly observed if the burst occurs at a small redshift so that its radio signal can be resolved. The size and shape are relevant for detailed analysis of scintillation or microlensing. We show that the effective Lorentz factor depends on the observed frequency and that it is higher for frequencies above the synchrotron typical frequency (optical and X-ray) than for low frequencies (radio). Consequently, transition to nonrelativistic evolution will be observed first in low frequencies and only a factor of ~2 later in the high frequencies.

Characterization of UHF radio propagation channels in tunnel environments for microcellular and personal communications

Abstract: Narrowband and wideband propagation measurements have been conducted in five tunnels. The effects of pedestrians, vehicles, and curvature on propagation are included in the characterization. The narrowband propagation is characterized in terms of power distance law, slow fading, and fast fading statistics: wideband propagation, rms delay spread, and its statistics. The results show that the power distance law is insensitive to the location of the transmit antenna in the cross section of a tunnel, but not to the antenna insertion loss. The lognormal distribution basically fits the slow variation of the received signals, whereas the Rician distribution, the fast fading in the straight empty sections of the tunnels. In the curved tunnel sections, the Rayleigh distribution does not fit the fast fading variation as is expected. Tunnel radio propagation channels are dependent strongly upon frequency. Higher frequency signals exhibit more severe fluctuations and larger rms delay spread. The rms delay spreads are found to be generally less than 25 and 103 ns for the emptied and occupied tunnel conditions, respectively. One can conclude that the tunnel channels have a broad coherent bandwidth and can support the data rate up to 1 Mb per second without equalization.

Propagation of the GPS Signals

Abstract: The Global Positioning System is a one-way ranging system. The GPS satellites emit signals — complex modulated radio waves — which propagate through space to receivers on or near the earth’s surface.1 From the signals it intercepts, a receiver measures the ranges between its antenna and the satellites. In this chapter, we will examine the nature of the GPS signals. After a brief review of the fundamentals of electromagnetic radiation, we will describe the structure of the GPS signals. Since the signals, in propagating to a receiver, must travel through the ionosphere and the neutral atmosphere, we will examine the effect these media have on the signals. Finally, we will look at the propagation phenomena of multipath and scattering and the effects they have on the measurements made by a GPS receiver.

Remote radio operating system, and remote operating apparatus, mobile relay station and radio mobile working machine

Abstract: A remote radio operating system provided with a radio mobile working machine (1), a remote operating apparatus (6A) and a mobile relay station (7), and further with first two-way communication means (31, 71) with a strong radio wave directivity and first automatic tracking means (32, 71A) between the working machine (1) and the mobile relay station (7), and second two-way communication means (63, 76) with a strong radio wave directivity, second automatic tracking means (63A, 76A), and emergency spread spectrum two-way communication means (64, 87) that permit two-way communication between the remote operating apparatus (6A) and the mobile relay station (7) in case communication by the second two-way communication means (63, 76) is impossible between the remote operating apparatus (6A) and the mobile relay station (7). This configuration allows the working machine (1) and the mobile relay station (7) to perform minimum required works even when communication between the working machine (1) and the mobile relay station (7) is impossible, and even anyone not skilled in the actual operation of the working machine (1) can remotely operate the machine easily.

Semiconductor module having antenna element therein

Abstract: A semiconductor module having a compact antenna element capable of providing desired directivity therein has been disclosed. When an electromagnetic-wave radiation window has the capability of a lens, directivity can be set arbitrarily. For improving directivity, a convergent lens for converging millimeter waves or quasi millimeter waves is employed. For impairing directivity, a divergent lens is employed. In the case of the convergent lens, a direction in which radio waves are radiated or received by the antenna element can be set by deviating the center axis of the lens from the center of the antenna element.

Mobile radio communication device provided with functions for detecting and informing interference

Abstract: A mobile radio communication device for performing communication with a base station comprises an interference detection measure for detecting occurrence of interference to the downlink frequency and/or the uplink frequency, and an interference informing measure for transmitting information about the occurrence of the interference to the base station. The base station which received the information about the interference assigns the mobile radio communication device new time slots or a new communication carrier frequency. The mobile radio communication device has a transmission system and two reception systems which are composing a post-detection selective space diversity system, and each of the two reception systems is composed of a double superheterodyne system, in the same way as general conventional mobile radio communication devices. Interference to the downlink frequency is detected utilizing the data error rate in the demodulated reception signal in one reception system, and interference to the uplink frequency is detected utilizing the field intensity of a radio wave having the uplink frequency received by an antenna of the other reception system. The detection and informing of interference is realized by addition of a simple circuit composed of a circulator, a high frequency amplifier, a mixer and a switch to a general conventional mobile radio communication device.

Electron beams and radio waves of solar Type III bursts

Abstract: Using the radio wave and energetic particle experiments on the Wind spacecraft, we examine how the radio flux density of interplanetary type III bursts depends on the flux and energy of the energetic electrons. We derive the relationship between them, first by giving detailed radio and electron characteristics of one type III burst, and then using the results of similar analyses of 10 bursts. The times of commencement of the radio waves from decametric to kilometric wavelengths, in relation to the onset time of Langmuir waves, demonstrate forcibly that the initial type III radiation is at the fundamental and not the harmonic. Near and after the time of peak flux density the radiation could be either at the fundamental or the harmonic. In our theoretical analysis we examine this point, i.e., how the emissivity of the fundamental and harmonic at the time of peak flux density depends on the beam properties. The data of the 10 events are in good accord (rc ≈ 0.9) with the theoretical relation for fundamental emission, but in disaccord with the theoretical relation for harmonic radiation. For the 10 bursts we find poor correlation between the radio flux density and the electron flux N(E‖) at the energy E‖ estimated to be that of the two-stream instability. However there is excellent correlation when N(E‖) is weighted by E‖ to a high power. From the best fit, we find rc ≈ 0.96 when N(E‖) is replaced by . Finally, we infer the efficiency of energy conversion from the kinetic energy of the electron beam to fundamental emission, and examine the attenuation of the peak emission within the source.

The thermal self-focusing instability near the critical surface in the high-latitude ionosphere

Abstract: A fully nonlinear development of the thermal self-focusing instability of high power radio waves in the ionosphere in the region near the critical surface is the subject of the present study. In the simulation model studied, a high-powered radio wave in the frequency range 5 - 10 MHz, with a 1% amplitude modulation, is launched vertically. In the high latitude geometry this represents a direction antiparallel to the magnetic field which is almost vertically downwards. The modulated wave undergoes strong self-focusing at the critical surface, where the group velocity of the wave goes to zero. The scale size of the structures transverse to the magnetic field is controlled by the wave intensity and the diffraction effects. The large parallel thermal conduction leads to the diffusion of these irregularities into the underdense and overdense plasma in narrow filaments. The depletion in the density in the overdense plasma allows propagation of the wave to higher altitude above the original critical surface and hence into the overdense plasma.

Radio wave propagation along mixed paths through a four-layered model of rain forest: an analytic approach

Abstract: This paper presents a novel full-wave analysis of the radio waves that are excited from a dipole antenna located in the trunk layer and propagate inside a four-layered forest medium The dyadic Green's functions for the four-layered geometry are applied first to derive the integral expression of the electric fields The closed form of the electric fields is then obtained by using the quasi-static approximation, saddle-point technique, and branch-cut integrations in the complex plane and, hence, expressed in terms of direct waves, multiple reflected waves, and lateral waves Two kinds of images, ie, the quasi-dynamic and complex images, are considered in the integration in the complex plane Among those waves excited by a dipole antenna in the four-layered medium, it is shown theoretically and numerically that the lateral wave along the upper-side air-canopy interface plays a role of dominant modes The propagation mechanism of other lateral waves due to the air-canopy, canopy-trunk, and trunk-ground interfaces is also discussed and analyzed so as to gain an insight into the wave characteristics Transmission losses of the lateral waves are calculated numerically

On the generation of auroral radio emissions at harmonics of the lower ionospheric electron cyclotron frequency: X, O and Z mode maser calculations

Abstract: Electron cyclotron maser emission has been suggested as a possible explanation of ground-based observations of auroral radio waves at twice and three times the lower ionospheric electron cyclotron frequency (2ƒce and 3ƒce). Preliminary theoretical work concluded that direct maser excitation at the first and second harmonics of the free space extraordinary mode (X2 and X3) could exceed collisional ionospheric damping rates, although growth rates were low. Recently, however, ground-based observations indicate that these emissions are predominantly O mode polarized. Therefore a reassessment of the lower ionospheric cyclotron maser as an emission mechanism is necessary. In this paper, kinetic cyclotron maser instability calculations are extended to include the trapped Z mode for varying thermal energies and auroral potential drops within the context of a realistic ionospheric electron distribution model. It is found that when the local upper hybrid frequency is in the close vicinity of 2ƒce or 3ƒce, harmonic Z mode (Z2 and Z3) growth rate is shown to be exceedingly high. This finding suggests that an indirect mechanism that involves linear or nonlinear mode conversion of the excited harmonic Z mode into the ordinary (O) mode is a possible emission mechanism.

Tire air pressure monitoring device using the wheel or a coil wound around the stem as the transmitter antenna

Abstract: A device for monitoring the air pressure of a wheel. The device prevents a decrease in the transmission level of radio waves caused by impedance mismatch between an antenna, which radiates the radio waves, and a circuit, which produces signals that are to be radiated as the radio waves. The device includes a valve stem through which air is charged. The valve stem extends through a vehicle wheel. A transmitter is secured to the wheel to transmit a signal representing the air pressure of the wheel to a receiver installed in the vehicle. The device further includes a case attached to the wheel. The case is connected to the valve stem. An electric circuit is accommodated in the case to detect the air pressure and convert the detected pressure to an electric signal. An antenna radiates the signal produced by the electric circuit and is arranged about the valve stem. A conveying mechanism conveys the signals produced by the electric circuit to the antenna.

Multifrequency inverted F-type antenna

Abstract: A multifrequency inverted F-type antenna which can receive multifrequency band radio waves without the enlargement of its shape. A cut-out part (12b) is formed in an emission conductor (12) one end of which is connected to a short-circuit plate (13) planted in a ground conductor (11) and which has a feeding point (12a) to form on the emission conductor (12) a first emission conductor (12-1) and a second emission conductor (12-2) which resonate at respective frequency bands different from each other. By this construction, the radio waves of two different frequency bands, i.e. a first frequency band determined by the shape of the first emission conductor (12-1) and a second frequency band determined by the shape of the second emission conductor (12-2), can be received.

Door approach communication apparatus and door lock control apparatus

Abstract: A door approach transmission apparatus comprises an outside door handle 20 having a conductor with a slit 23 disposed in the door handle surface. A slot antenna 21, 23, 24, 25 is disposed at the slit 23 , and includes feeding points 24, 25 installed on the conductor. The apparatus also includes a transmitter 26 for applying voltage for radio wave oscillation to the feeding points 24, 25 . The above-described door approach transmission and reception apparatus can be used in a door lock control apparatus where a search radio wave is emitted from a vehicle, a portable wireless device 10 receives the search radio wave, and returns an ID signal. An electrically driven door lock apparatus 40 is driven to unlock the door when the returned ID signal coincides with a registered ID signal. The search radio wave is irradiated from the slot antenna. Either of a transmitter 26 and a receiver 33 is selectively connected to the feeding points 24, 25 . By virtue of the above-described features, the emission and reception of radio waves is realized, and in the case of a door handle made of a metal, the number of parts for emission and reception of the radio waves are reduced.

Propagation of medium frequency (1–4 MHz) auroral radio waves to the ground via the Z‐mode radio window

Abstract: Recent ground-based observations of auroral radio waves have identified narrowband emissions near 2 and 3 times the lower ionospheric electron cyclotron frequency (fce) known as auroral roars. In this paper the propagation of these waves in the auroral ionosphere is investigated by means of a ray-tracing technique. We model one particular scenario in which a large-scale (tens of kilometers) horizontal density structure, based on density structures observed with the Sondrestrom radar at times of auroral roar emissions, plays a crucial role in both guiding the waves to the ground and enabling mode conversion. The location and the mode characteristics of the initial waves are determined on the basis of local stability properties, which suggests that Z-mode wave excitation is favored near 2fce. However, since Z-mode cannot propagate to the ground they must first undergo a mode conversion to one of the free-space modes (X and O). It is found that for a narrow range of frequencies and initial wave phase angles the trapped Z mode can be converted to O mode via the Ellis radio window. This finding is consistent with the fact that auroral roar emissions are nearly 100% O-mode polarized. However, it is important to note that the evaluation of the damping of the Z-mode waves along the ray path is not considered within the context of this preliminary study and will be critical for eventually determining the exact physical scenario of the auroral roar generation mechanism.

Antenna system for circularly polarized radio waves including antenna means and interface network

Abstract: An antenna system for a radio communication device, in particular a hand-portable telephone, having communication circuits and to be operating by circularly-polarized radio waves. In the system (1) there is provided a radiation means, preferably helical elements (2, 3, 4), a feeding network (8) having first coupling means (9) adapted for coupling to said communication circuits and second coupling means coupled to said helical elements (2, 3, 4). The interface means includes a closed resonator means (14), which has at least a first portion associated with said first coupling means (9), and having separated at least second (11), third (12) and fourth (13) portions forming said second coupling means (11, 12, 13).

Non-contact ic card reader-writer

Abstract: PROBLEM TO BE SOLVED: To eliminate the need of individually designing a radio wave output circuit and to prevent the leakage of unrequired electromagnetic waves and the influence of the electromagnetic waves from the outside by contriving the structure of the case body with respect to a non-contact IC card reader-writer. SOLUTION: An antenna 10a printed on an antenna substrate 10 and an electronic circuit 40a mounted on a printed wiring board 40 are arranged inside the case body 30 provided with an electromagnetic wave shielding function. Then, in order to discharge the electromagnetic waves outputted from the antenna 10a from the case body 30 only in a direction required for communication with a non-contact card, an electromagnetic wave shielding pattern 10b is printed on the antenna substrate 10 fixed to the opening part of an upper case body member 30u for constituting the case body 30 and an electromagnetic wave passing port for discharging the electromagnetic waves is formed.

Theoretical model for long time stimulated electromagnetic emission generation in ionospheric radio modification experiments

Abstract: Experimental evidence points toward magnetic-field-aligned small-scale plasma density striations as responsible for the long time features of stimulated electromagnetic emissions (SEE) in ionospheric radio modification experiments. This paper emphasizes that such striations act as resonators for the generation of trapped upper hybrid oscillations. The sidebands observed in long time SEE experiments are associated with nonstationary behavior, such as parametric instabilities, of these trapped oscillations. A theoretical model for this is formulated and studied numerically. Source spectra for SEE generation, consistent with the main properties of observed downshifted maximum and broad continuum features, will be presented. The first is associated with a trapped oscillations decay instability, while the latter is associated with cavitation in the pre-formed striations.

Radio Wavelength Constraints on the Sources of the Far-Infrared Background

Abstract: The cosmic far-infrared background detected recently by the COBE-DIRBE team is presumably due, in large part, to the far-infrared (FIR) emission from all galaxies. We take the well-established correlation between FIR and radio luminosity for individual galaxies and apply it to the FIR background. We find that these sources make up about half of the extragalactic radio background, the other half being due to active galactic nuclei (AGNs). This is in agreement with other radio observations, which leads us to conclude that the FIR-radio correlation holds well for the very faint sources making up the FIR background and that the FIR background is indeed due to star formation activity (not AGNs or other possible sources). If these star-forming galaxies have a radio spectral index between 0.4 and 0.8 and make up 40%-60% of the extragalactic radio background, we find that they have redshifts between roughly 1 and 2, which is in agreement with recent estimates by Madau et al. of the redshift of peak star formation activity. We compare the observed extragalactic radio background to the integral over the log${r log}$ -->${r log}$ -->N-log${r log}$ -->${r log}$ -->S curve for star-forming radio sources and find that the slope of the curve must change significantly below about 1 μJy. At 1 μJy, the faint radio source counts predict about 25 sources per square arcminute, and these will cause the Space Infrared Telescope Facility to be confusion limited at 160 μm.

Random pulse type radar apparatus

Abstract: A random pulse type radar apparatus sends out as an output signal a spectrum spread radio wave including a pseudo random signal-less period and receives echoes in this signal-less period to thereby significantly reduce transmission peak power. The random pulse type radar apparatus comprises a transmitter for generating a hybrid type spectrum spread signal by simultaneously using two kinds of modulations which are phase shift keying modulation for selecting a phase of a transmission radio wave in accordance with a pseudo noise digital code and outputting the transmission wave, and time hopping modulation for stopping transmission of a radio wave at random in accordance with the pseudo noise digital code; a receiving unit for selectively detecting an echo of a transmission signal radio wave, generated by the transmitter, from a target with a time delay; at least one a common antenna unit for use both for transmission and reception or antenna units installed close to each other and respectively serving single functional units; and a reception control unit for stopping an action of the receiving unit in a time zone in which the transmitter is outputting radio waves in accordance with the time hopping modulation, whereby a spatial distribution of an intensity of an echo of a transmitted radio wave is measured through computation of a cross-correlation function of a transmission signal and a reception signal.

Radio wave absorber

Abstract: PROBLEM TO BE SOLVED: To ensure superior radio wave absorbing characteristics by imparting a compsn. consisting of a specified mol% of Na2 O and the balance alumina with inevitable impurities. SOLUTION: A mixture of alumina powder of >=99% purity with 3-10mol% Na2 O or compd. capable of forming Na2 O at the time of firing is compacted in a prescribed shape by die pressing or other method. The resultant compact is fired at 1,550-1,750 deg.C for 2-10hr in an oxidizing atmosphere to obtain the objective radio wave absorber made of an alumina sintered compact consisting of Na2 O, alumina and inevitable impurities and having >=95% relative density, a specific gravity of =4200MPa four-point bending strength and >=20dB attenuation constant of radio waves having 1-20GHz frequency.

Geophysical phenomena during an ionospheric modification experiment at Tromsø, Norway

Abstract: . We present an analysis of phenomena observed by HF distance-diagnostic tools located in St. Petersburg combined with multi-instrument observation at Tromso in the HF modified ionosphere during a magnetospheric substorm. The observed phenomena that occurred during the Tromso heating experiment in the nightside auroral Es region of the ionosphere depend on the phase of substorm. The heating excited small-scale field-aligned irregularities in the E region responsible for field-aligned scattering of diagnostic HF waves. The equipment used in the experiment was sensitive to electron density irregularities with wavelengths 12–15 m across the geomagnetic field lines. Analysis of the Doppler measurement data shows the appearance of quasiperiodic variations with a Doppler frequency shift, fd and periods about 100–120 s during the heating cycle coinciding in time with the first substorm activation and initiation of the upward field-aligned currents. A relationship between wave variations in fd and magnetic pulsations in the Y-component of the geomagnetic field at Tromso was detected. The analysis of the magnetic field variations from the IMAGE magnetometer stations shows that ULF waves occurred, not only at Tromso, but in the adjacent area bounded by geographical latitudes from 70.5° to 68° and longitudes from 16° to 27°. It is suggested that the ULF observed can result from superposition of the natural and heater-induced ULF waves. During the substorm expansion a strong stimulated electromagnetic emission (SEE) at the third harmonic of the downshifted maximum frequency was found. It is believed that SEE is accompanied by excitation of the VLF waves penetrating into magnetosphere and stimulating the precipitation of the energetic electrons (10–40 keV) of about 1-min duration. This is due to a cyclotron resonant interaction of natural precipitating electrons (1–10 keV) with heater-induced whistler waves in the magnetosphere. It is reasonable to suppose that a new substorm activation, exactly above Tromso, was closely connected with the heater-induced precipitation of energetic electrons. Key words. Ionosphere (active experiments; ionosphere · magnetosphere interactions). Radio science (nonlinear phenomena).

Radio communication network

Abstract: PROBLEM TO BE SOLVED: To provide a communication network for realizing inexpensive and easy data communication by using radio communication. SOLUTION: Radio terminals 2 are distributed and installed in a mesh shape with a specified interval and a radio mesh 1 is constituted. The radio terminals 2 adjacent to each other are communicable, and by transferring and relaying packet data between the adjacent radio terminals 2, data are transferred between optional terminals. Also, as a congestion processing, the radio terminal 2 changes a transmission speed corresponding to a data amount inside a network and changes a transfer speed by a transmission destination. Further, at the time of data transmission, directivity is provided. Also, for the collision of counter radio waves, plural channels are provided and the data are transmitted from the two or more channels. Further, the respective radio terminals 2 are provided with a function for selecting the closest one of plural connection points. Also, a server for maintenance management can be connected to the radio mesh 1 as well.

The WIND‐HAARP Experiment: Initial results of high power radiowave interactions with space plasmas

Abstract: Results from the first science experiment with the new HF Active Auroral Research Program (HAARP) in Alaska are reported. The objective was to study the effects of space plasmas on high power radiowave transmission to high altitudes in the magnetosphere. Reception was done by the NASA/WIND satellite. The data suggest that structured space plasmas along the propagation path impose a power law spectrum of fluctuations on the transmitted waves, resembling scintillations. Because the transmitted waves are near ionospheric plasma frequencies, other types of wave-plasma interactions may occur. Such measurements can provide a new diagnostic tool.

Order data management system

Abstract: PROBLEM TO BE SOLVED: To shorten a transmission waiting time, to reduce an electric wave collision and also to change arrangement, etc., at the time of changing the layout of customer seats or a kitchen, etc., at a low cost in a short time. SOLUTION: A system is provided with a radio portable terminal 33 for receiving order information so as to transmit it by radio wave, a POL(point of sales) terminal 32 for storing and managing sales information at a customer seat, a display/input device 34 for displaying order information and inputting an ordered article preparation end in the kitchen, a printing device 35 for printing a demand to a customer in the kitchen, a system controller 36 for managing information such as sales information or order information, etc., a communication controller 39 connected to it by a cable, radio terminals 41-43 connected to the POS terminal 32, to the display/input device 34 and to the printing device 35, and radio base stations 37 and 38 connected to a communication controller 39 by the cable so as to execute radio communication with the radio portable terminal 33 and the radio terminals 41-43 by whole double radio links. COPYRIGHT: (C)1999,JPO