Showing papers on "Radio wave published in 2003"

Development and performance analysis of an intra-body communication device

Abstract: Personal area networks would benefit from a wireless communication system in which a variety of information could be exchanged through wearable electronic devices and sensors. Intra-body communication using the human body as the transmission medium enables wireless communication without transmitting radio waves through the air. A human arm phantom is designed and used to reduce uncertainty in experiments with the human body. The phantom exhibits transmission characteristics similar to those of the human body at frequencies between 1 MHz and 10 MHz. A 10.7 MHz frequency modulation (FM) intra-body transmitter and receiver are developed which allow transmission of analog sine waves even in the presence of external noise. Digital data transmission at 9600 bps was also achieved using newly fabricated 10.7 MHz frequency shift keying (FSK) transmitter and receiver devices. The carrier frequency of 10.7 MHz, which is the intermediate frequency in FM radio receivers, means that a wide selection of commercial radio frequency (RF) devices is available.

Gigantic jets between a thundercloud and the ionosphere.

Abstract: Transient luminous events in the atmosphere, such as lighting-induced sprites and upwardly discharging blue jets, were discovered recently in the region between thunderclouds and the ionosphere. In the conventional picture, the main components of Earth's global electric circuit include thunderstorms, the conducting ionosphere, the downward fair-weather currents and the conducting Earth. Thunderstorms serve as one of the generators that drive current upward from cloud tops to the ionosphere, where the electric potential is hundreds of kilovolts higher than Earth's surface. It has not been clear, however, whether all the important components of the global circuit have even been identified. Here we report observations of five gigantic jets that establish a direct link between a thundercloud (altitude approximately 16 km) and the ionosphere at 90 km elevation. Extremely-low-frequency radio waves in four events were detected, while no cloud-to-ground lightning was observed to trigger these events. Our result indicates that the extremely-low-frequency waves were generated by negative cloud-to-ionosphere discharges, which would reduce the electrical potential between ionosphere and ground. Therefore, the conventional picture of the global electric circuit needs to be modified to include the contributions of gigantic jets and possibly sprites.

Ionospheric electron heating, optical emissions, and striations induced by powerful HF radio waves at high latitudes: Aspect angle dependence

Abstract: radio-induced aurora showed that the enhancement caused by the HF radio waves also remained localized near the field-aligned position. Coherent HF radar backscatter also appeared strongest when the pump beam was pointed field-aligned. These results are similar to some Langmuir turbulence phenomena which also show a strong preference for excitation by HF rays launched in the field-aligned direction. The correlation of the position of largest temperature enhancement with the position of the radio-induced aurora suggests that a common mechanism, upper-hybrid wave turbulence, is responsible for both effects. Why the strongest heating effects occur for HF rays directed along the magnetic field is still unclear, but self-focusing on field-aligned striations is a candidate mechanism, and possibly ionospheric tilts may be important. INDEX TERMS: 2403 Ionosphere: Active experiments; 6929 Radio Science: Ionospheric physics (2409); 7839 Space Plasma Physics: Nonlinear phenomena; KEYWORDS: HF-heating, ionospheric modification, electron heating, EISCAT, striations, aspect angle

Improving HF Radar Surface Current Measurements with Measured Antenna Beam Patterns

Abstract: A high-frequency (HF) radar system is deployed on the New Jersey continental shelf as part of a coastal ocean observatory. The system includes two remote transmit‐receive sites in Brant Beach and Brigantine, New Jersey, and a central processing site in Tuckerton, New Jersey. The system uses radio waves scattered off the ocean to measure the radial velocity, range, and bearing of the scattering surface. Calculation of the bearing for HF radar systems depends on the actual beam pattern of the receive antennas. A series of antenna beam pattern measurements conducted on the New Jersey system shows that these patterns are often distorted when an antenna is deployed in the field. Tests indicate that the local environment, not system hardware, causes the most significant distortion of the pattern from the theoretical shape. Correlation with an in situ acoustic Doppler current profiler (ADCP) indicates that the beam pattern distortion can bias the bearing estimate. It is shown that this bias can be removed if the measured beam patterns are used to estimate the bearing.

Non-Ionizing Radiations - Sources, Biological Effects, Emissions and Exposures

Abstract: Non-Ionizing radiation (NIR) refers to radiative energy that, instead of producing charged ions when passing through matter, has sufficient energy only for excitation. Nevertheless it is known to cause biological effects. The NIR spectrum is divided into two main regions, optical radiations and electromagnetic fields. The optical can be further sub-divided into ultraviolet, visible, and infra-red. The electromagnetic fields are further divided into radiofrequency (microwave, very high frequency and low frequency radio wave).

Peripheral monitor for monitoring periphery of vehicle

Abstract: The invention solves a problem of fluctuation in performance in the conventional peripheral monitor for monitoring periphery of a vehicle that measures a distance to other vehicle or any other object by transmitting radio waves and informs a driver of the distance due to variation in environmental conditions such as water drop sticking onto the cover. A peripheral monitor 1 including a transmission antenna 2 for radiating transmission waves through the cover, a receiving antenna 3 for receiving reflected waves through the cover, and a data processor for measuring a distance to any object are disposed together in a cover 7 . A transmission frequency at which reflected wave quantity is minimized is detected by detecting a first reflected signal level from the cover 7, and this frequency is a command to a variable frequency oscillator to conduct a transmission at this frequency at all times.

Radio Engineering for Wireless Communication and Sensor Applications

Abstract: Introduction to radio waves and radio engineering fundamentals of electromagnetic fields transmission lines and waveguides impedance matching microwave circuit theory passive transmission line and waveguide devices resonators and filters circuits based on semiconductor devices antennas propagation of radio waves radio system applications biological effects and safety standards.

A semiempirical model of the normalized radar cross section of the sea surface, 2. Radar modulation transfer function

Abstract: [1] Multiscale composite models based on the Bragg theory are widely used to study the normalized radar cross section (NRCS) over the sea surface. However, these models are not able to correctly reproduce the NRCS in all configurations. In particular, even if they may provide consistent results for vertical transmit and receive (VV) polarization, they fail in horizontal transmit and receive (HH) polarization. In addition, there are still important discrepancies between model and observations of the radar modulation transfer function (MTF), which relates the modulations of the NRCS to the long waves. In this context, we have developed a physical model that takes into account not only the Bragg mechanism but also the non-Bragg scattering associated with radio wave scattering from breaking waves. The same model was built to explain both the background NRCS and its modulation by long surface wave (wave radar MTF problem). In part 1, the background NRCS model was presented and assessed through comparisons with observations. In this part 2, we extend the model to include a third underlying scale associated with longer waves (wavelength ∼10–300 m) to explain the modulation of the NRCS. Two contributions are distinguished in the model, corresponding to the so-called tilt and hydrodynamic MTF. Results are compared to observations (already published in the literature or derived from the FETCH experiment). As found, taking into account modulation of wave breaking (responsible for the non-Bragg mechanism) helps to bring the model predictions in closer agreement with observations. In particular, the large MTF amplitudes for HH polarization (much larger than for VV polarization) and MTF phases are better interpreted using the present model.

Photovoltaic Technologies Beyond the Horizon: Optical Rectenna Solar Cell, Final Report, 1 August 2001-30 September 2002

Abstract: ITN Energy Systems is developing next-generation solar cells based on the concepts of an optical rectenna. ITN's optical rectenna consists of two key elements: (1) an optical antenna to efficiently absorb the incident solar radiation, and (2) a high-frequency metal-insulator-metal (MIM) tunneling diode that rectifies the AC field across the antenna, providing DC power to an external load. The combination of a rectifying diode at the feedpoints of a receiving antenna is often referred to as a rectenna. Rectennas were originally proposed in the 1960s for power transmission by radio waves for remote powering of aircraft for surveillance or communications platforms. Conversion efficiencies greater than 85% have been demonstrated at radio frequencies (efficiency defined as DC power generated divided by RF power incident on the device). Later, concepts were proposed to extend the rectennas into the IR and optical region of the electromagnetic spectrum for use as energy collection devices (optical rectennas).

Magnetic zenith enhancement of HF radio-induced airglow production at HAARP

Abstract: [1] Airglow production at various beam positions relative to the magnetic field was investigated as part of an optics campaign at HAARP in February 2002. Strong emissions up to several hundred Rayleigh at 630.0 nm and more than 50 R at 557.7 nm were produced in a small spot approximately 6° in diameter located near the magnetic zenith when the transmitter beam was directed up the magnetic field. This effect was observed hundreds of times over a wide range of frequencies and ionospheric conditions. The spot at HAARP appears on average just equatorward of the nominal magnetic field direction, deflects somewhat toward the beam center when the beam is scanned, and varies slightly in size with transmitter frequency. Red-to-green ratios as low as 3 were observed, with both wavelengths showing significant onset delay. Identifiable enhancements in red-line emission were produced down to 2 MW ERP in a power ramp experiment. INDEX TERMS: 0310 Atmospheric Composition and Structure: Airglow and aurora; 2403 Ionosphere: Active experiments; 2483 Ionosphere: Wave/particle interactions; 2487 Ionosphere: Wave propagation (6934); 2494 Ionosphere: Instruments and techniques. Citation: Pedersen, T. R., M. McCarrick, E. Gerken, C. Selcher, D. Sentman, H. C. Carlson, and A. Gurevich, Magnetic zenith enhancement of HF radio-induced airglow production at HAARP, Geophys. Res. Lett., 30(4), 1169, doi:10.1029/2002GL016096, 2003.

Attitude angle detecting apparatus

Abstract: An attitude angle detecting apparatus receives radio waves transmitted from a plurality of position-fixing satellites with multiple antennas located at specific positions of a mobile unit, determines relative positions of the antennas and detects the heading and attitude of the mobile unit by determining carrier phase ambiguities quickly and accurately. When it is needed to redetermine integer ambiguities after recovery from an interruption of the radio waves from the position-fixing satellites or as a result of a change in combination of the position-fixing satellites, for example, the attitude angle detecting apparatus redetermines the integer ambiguities by using attitude angles and an attitude angle error covariance obtained from previous observation. This enables the attitude angle detecting apparatus to uninterruptedly obtain information on the heading and attitude of the mobile unit.

Energy and time-lag spectra of galactic black-hole X-ray sources in the low/hard state

Abstract: Most, probably all, accreting binaries that are believed to contain a black-hole emit radio waves when they are in the low/hard state. Whenever this radio emission has been resolved, a jet-like structure has become apparent. We propose that Compton upscattering of low-energy photons in the jet can explain both the energy spectra and the time lags versus Fourier frequency observed in the low/hard state of black-hole systems. The soft photons originate in the inner part of the accretion disk. We have performed Monte Carlo simulations of Compton upscattering in a jet and have found that for a rather wide range of values of the parameters we can obtain power-law high-energy X-ray spectra with photon-number index in the range 1.5-2 and power-law time lags versus Fourier frequency with index ∼0.7. The black-hole source Cyg X-1 in the low/hard state is well described by our model.

Radio communication system

Abstract: PROBLEM TO BE SOLVED: To provide a radio communication system by which scattering of signals can be prevented and the signals can be effectively used SOLUTION: The RFID system 1 has an interrogator 11, an interrogator antenna 12 which is connected with the interrogator 11 and transmits signals, an approximately elliptic radio wave reflector 14 which reflects the signals emitted from the interrogator antenna 12 and radio tags 13 which receive the signals from the interrogator antenna 12 through at least the approximately elliptic radio wave reflector 14 and respond for performing communication with the interrogator 11 The interrogator antenna 12 is arranged in such a way that the reflecting surface 15 is oriented to a first focal point 16 of the reflecting surface 15 of the approximately elliptic radio wave reflector 14 and the radio tags 13 are arranged in the proximity of a second focal point 17 of the reflecting surface 15 of the approximately elliptic radio wave reflector 14 Since the interrogation signals emitted from the interrogator antenna 12 are reflected by the approximately elliptic radio wave reflector 14 and a region in which the interrogation signals are intensive is formed at the second focal point 17, the communication accuracy of the radio tag 13 positioned at the second focal point 17 with the interrogator 11 is improved COPYRIGHT: (C)2004,JPO

Energy and time-lag spectra of black-hole systems in the low state

Abstract: Most, probably all, accreting binaries that are believed to contain a black-hole emit radio waves when they are in the low/hard state. Whenever this radio emission has been resolved, a jet-like structure has become apparent. We propose that Compton upscattering of low-energy photons in the jet can explain both the energy spectra and the time lags versus Fourier frequency observed in the low/hard state of black-hole systems. The soft photons originate in the inner part of the accretion disk. We have performed Monte Carlo simulations of Compton upscattering in a jet and have found that for a rather wide range of values of the parameters we can obtain power-law high-energy X-ray spectra with photon-number index in the range 1.5 - 2 and power-law time lags versus Fourier frequency with index ~ 0.7. The black-hole source Cyg X-1 in the low/hard state is well described by our model.

Localized superluminal solutions to the wave equation in (vacuum or) dispersive media, for arbitrary frequencies and with adjustable bandwidth

Abstract: In this paper we set forth new exact analytical superluminal localized solutions to the wave equation for arbitrary frequencies and adjustable bandwidth. The formulation presented here is rather simple and its results can be expressed in terms of the ordinary, so-called “X-shaped waves”. Moreover, by the present formalism we obtain the first analytical localized superluminal approximate solutions which represent pulses propagating in dispersive media. Our solutions may find application in different fields, like optics, microwaves, radio waves, and so on.

A novel method of studying total body water content using a resonant cavity: experiments and numerical simulation.

Abstract: A novel electromagnetic method of obtaining total body water is proposed, in which the water content is obtained from the dielectric properties as measured by a resonant perturbation technique. A screened room acts as a radio-frequency cavity, in our case resonating at 59 MHz, a frequency at which both real and imaginary parts of the complex permittivity of tissues are correlated to their moisture content. The presence of a human subject in the room leads to both a negative shift in the room's resonant frequency and a reduction in its Q-factor. We simulated the room and the body using the transmission line matrix (TLM) method, a computational electromagnetic code which models the problem in the time domain. Experiment and numerical model showed good agreement for two orientations of the subject. The sensitivity of the technique was investigated by measuring the response before and after the subject drank a small quantity of water, less than 2% of body mass. The resulting change in the resonant frequency was significant, and was also predicted by the numerical model. The proposed technique for studying body composition is simple, non-invasive and employs non-ionizing radio waves at low power.

Adaptive antenna radio communication device

Abstract: A device for estimating a direction-of-arrival of a radio wave, the device comprising an array antenna including a plurality of antenna elements for receiving a high frequency signal, a demultiplexer for demultiplexing the received high frequency signal for each of the plurality of antenna elements to generate a plurality of frequency component signals and a direction estimating unit for estimating the direction-of-arrival of the radio wave by using two or more of the plurality of frequency component signals which are contiguous in a frequency direction.

Localized superluminal solutions to the wave equation in (vacuum or) dispersive media, for arbitrary frequencies and with adjustable bandwidth q

Abstract: In this paper we set forth new exact analytical superluminal localized solutions to the wave equation for arbitrary frequencies and adjustable bandwidth. The formulation presented here is rather simple and its results can be expressed in terms of the ordinary, so-called ‘‘X-shaped waves’’. Moreover, by the present formalism we obtain the first analytical localized superluminal approximate solutions which represent pulses propagating in dispersive media. Our solutions may find application in different fields, like optics, microwaves, radio waves, and so on.

Vehicle periphery monitoring device

Abstract: PROBLEM TO BE SOLVED: To solve the problem of having large fear of deadening a battery due to an increase in electric power consumption by simultaneously operating a keyless entry system and a security device SOLUTION: A transmission wave of a radar radio wave (a periphery monitoring sensor 105) for monitoring the vehicle periphery, is modulated to a pulse by an identification code of a keyless entry unit 103, and this radio wave is used as a calling radio wave of the keyless entry unit 103 A transmission interval of the radar radio wave for monitoring the periphery, and a transmission interval of the calling radio wave of the keyless entry system, are controlling based on a distance to an object approaching a vehicle detected by this radar radio wave Electric power consumption of the periphery monitoring sensor 105 and the keyless entry system, is reduced by lengthening the transmission interval when the distance is large COPYRIGHT: (C)2005,JPO&NCIPI

Radio wave transmitter search system, cellular phone communication terminal apparatus, and radio wave transmitter search method by radio wave transmitter search system

Abstract: PROBLEM TO BE SOLVED: To provide an RFID tag search system for exhibiting information serving as a clue for acquiring a position of an RFID tag to a user, when the user searches the RFID tag. SOLUTION: This RFID tag search system 1 detects the maximum value of radio wave intensity, by an antenna 12 for receiving radio wave emitted from the RFID tag, an intensity detecting part 14 for detecting the radio wave intensity received by the antenna 12, a difference computing part 15 for calculating a difference in the radio wave intensity detected by the intensity detecting part 14, and a difference change detecting part 16 for detecting a change in the difference calculated by the difference computing part 15. When the RFID tag search system 1 detects the maximum value of the radio wave intensity, the system 1 displays the detection on a display 18 by a searched result processing part 4. COPYRIGHT: (C)2005,JPO&NCIPI

The Whisper Relaxation Sounder Onboard Cluster: A Powerful Tool for Space Plasma Diagnosis1, 2 around the Earth

Abstract: The WHISPER relaxation sounder that is onboard the four CLUSTER spacecraft has as its main scientific objectives to monitor the natural waves in the 2 kHz–80 kHz frequency range and, mostly, to determine the total plasma density from the solar wind down to the Earth's plasmasphere. To fulfill these objectives, the WHISPER uses the two long double sphere antennae of the Electric Field and Wave experiment as transmitting and receiving sensors. In its active working mode, the WHISPER works according to principles that have been worked out for topside sounding. A radio wave transmitter sends an almost monochromatic and short wave train. A few milliseconds after, a receiver listens to the surrounding plasma response. Strong and long lasting echoes are actually received whenever the transmitting frequencies coincide with characteristic plasma frequencies. Provided that these echoes, also called resonances, may be identified, the WHISPER relaxation sounder becomes a reliable and powerful tool for plasma diagnosis. When the transmitter is off, the WHISPER behaves like a passive receiver, allowing natural waves to be monitored. This paper aims mainly at the resonance identification process description and the WHISPER capabilities and performance highlighting.

Apparatus for measuring specific absorption rate based on near magnetic field for use in radio apparatus

Abstract: In an apparatus for measuring a specific absorption rate (SAR) for use in a radio apparatus, a first near magnetic field of a radio wave radiated from a reference radio apparatus is measured in free space, and an SAR of the radio wave radiated from the reference radio apparatus by using a predetermined phantom according to a predetermined measurement method. A transformation factor α is calculated by dividing the measured SAR by a square value of the measured first near magnetic field, and a second near magnetic field of a radio wave radiated from a radio apparatus to be measured is measured in free space. Then an SAR of the radio wave radiated from the radio apparatus to be measured is estimated and calculated by multiplying a square value of the measured second near magnetic field by the calculated transformation factor α.

Scattering of VHF radio waves from within an ice sheet containing the vertical-girdle-type ice fabric and anisotropic reflection boundaries

Abstract: Abstract We studied the scattering of radio waves off strata within the ice sheet at Mizuho station, Antarctica, to determine the most plausible scattering mechanisms at this location. We measured the effects of birefringence and anisotropic scattering boundaries on the return signal using the following set of experimental conditions: (1) co-polarization and cross-polarization antenna arrangements, (2) all orientations of the antenna system, (3) 60 and 179 MHz frequencies, and (4) pulse lengths of 150–1000 ns. Analyses of the propagated radio waves suggested that the signal is dominated by anisotropic scatter-ingboundaries at 179 MHz, but effects from birefringence also occurred. At depths of 250– 750 m, the scattering was stronger when the polarization plane was along the flowline. In contrast, at depths of about 900–1500 m, scattering was stronger when the polarization plane was perpendicular to the flowline. We suggest that the scattering below about 250 m is related to a layered ice stratum of crystal-orientation fabrics with different types or different cluster strengths. Although our study was at a single site, similar remote measurements over wider regions should provide valuable information about the physical structure of this vast ice sheet.

Global mapping of attenuation at Ku- and Ka-band

Abstract: The propagation of radio waves for Earth-space slant path at C-band and higher frequencies is dominated by precipitation in the atmosphere. At a given frequency, attenuation depends on the length of the radio path, the size distribution, and the phase state of the hydrometeor profile. Using the observations from the Tropical Rainfall Measuring Mission (TRMM) spaceborne Ku-band (13.8 GHz) radar at low Earth orbit of 350 km above Earth, global attenuation maps are produced at the Ku-band frequency. A simple microphysical model for precipitation developed using hydrometeor size distributions and thermodynamic phase state is used to estimate attenuation and reflectivity observations at Ka-band (35 GHz) where numerous high-bandwidth satellite applications are being planned including the next-generation space-based radar for the Global Precipitation Mission (GPM). Differences in the microphysical structure in convective and stratiform precipitation are also incorporated in the model. The results show substantial attenuation variation in a 12-month period at both Ku- and Ka-bands over the various regions of the globe, including the contrast between land and ocean. The estimates of attenuation made at Ku- and Ka-band will be useful in the design and development of spaceborne systems.

Linear mode conversion in inhomogeneous magnetized plasmas during ionospheric modification by HF radio waves

Abstract: [1] The propagation of high-frequency (HF) radio waves in an inhomogeneous magnetoactive plasma and generation of plasma waves at the resonance layer near the reflection layer of the ordinary mode are studied using one-dimensional (1-D) and two-dimensional full-wave codes. The characteristics of the mode-conversion process are investigated in linear and parabolic density profiles as the angle of incidence is varied. We present the 1-D results for the wave propagation relevant to the high-latitude heater facility at Tromso and the midlatitude facility at Arecibo. For the facility at Arecibo, the 2-D wave propagation in a plasma density approximating an overdense sporadic-E patch is investigated to determine the localized regions of amplified intensity, where plasma waves can facilitate acceleration of fast energetic electrons, resulting in observed enhanced airglow.

Mobile robot capable of autonomously recovering radio wave status

Abstract: PROBLEM TO BE SOLVED: To provide a mobile robot that can continue operations even after moving beyond the reach of radio waves by autonomously returning within the reach of radio waves and can extend a communication range in cooperation with a plurality of mobile robots. SOLUTION: Mapping means 19 autonomously map radio statuses in advance at mobile robot introduction or in a standby state without an operation command, and store them in storing means 16. Returning means 17, after an operation in an area with a poor radio status, move the mobile robot to the nearest communication range according to the mapping information. When another mobile robot enters an area with a poor radio status, radio relaying means 12a amplify field strength to extend the communication range, so that an operator and the mobile robot in the communication-disabled area can communicate. The radio relaying means may be replaced with command relaying means. COPYRIGHT: (C)2005,JPO&NCIPI

Thermal self‐focusing instability in the high‐latitude ionosphere

Abstract: [1] A model for the linear theory of the overdense thermal self-focusing instability, as generated by high power radio waves, in the high-latitude F-region ionosphere is developed. We treat self-focusing-driven irregularities with scale sizes, perpendicular to the geomagnetic field, on the order of a kilometer and smaller. We find that E-region coupling leads to nonambipolar perpendicular diffusive effects. The conducting E-region is shown to increase the threshold for the thermal self-focusing instability. Growth rates of the thermal self-focusing instability are computed, including E-region conductivity effects, for a range of radio wave amplitudes.

Tire monitoring system

Abstract: PROBLEM TO BE SOLVED: To provide a tire monitoring system capable of receiving a radio wave with high gain transmitted from a sensor device provided in each tire by one antenna connected to a monitoring unit. SOLUTION: The antenna 50 connected to the monitoring unit and receiving a radio wave transmitted from the sensor device 30 provided in each tire 20 is provided in the window 11 of a vehicle 1. Preferably, the antenna 50 used herein includes a portion in which at least a part of an element can be extended in the vertical direction. A radio wave is radiated from the antenna 50, and the shape and the disposition of the antenna 50 that can maximize the field intensity at a position of each tire 20 are obtained by an actual measurement. Thus, a weak radio wave transmitted from each sensor device 30 can be received by the antenna 50 with high efficiency. COPYRIGHT: (C)2005,JPO&NCIPI

Radio wave reception device, radio wave clock, and repeater

Abstract: A received low-frequency standard radio wave, which is an amplitude modulation signal, is converted to an intermediate frequency signal Sa, and is output to a detection circuit (620) and an AGC circuit (618). The detection circuit (620) and AGC circuit (618) generates an RF control signal Sfl and IF control signal Sf2 from the input intermediate frequency signal Sa, and controls an RF control circuit (611) and IF control circuit (616) by outputting the generated RF control signal Sf1 and IF control signal Sf2 to the RF control circuit (611) and IF control circuit (616). By this a radio wave reception device (61) can speed up AGC operation. [Selected drawing] FIG.2