Showing papers on "Radio wave published in 2005"

Radio interferometric geolocation

Abstract: We present a novel radio interference based sensor localization method for wireless sensor networks. The technique relies on a pair of nodes emitting radio waves simultaneously at slightly different frequencies. The carrier frequency of the composite signal is between the two frequencies, but has a very low frequency envelope. Neighboring nodes can measure the energy of the envelope signal as the signal strength. The relative phase offset of this signal measured at two receivers is a function of the distances between the four nodes involved and the carrier frequency. By making multiple measurements in an at least 8-node network, it is possible to reconstruct the relative location of the nodes in 3D. Our prototype implementation on the MICA2 platform yields an average localization error as small as 3 cm and a range of up to 160 meters. In addition to this high precision and long range, the other main advantage of the Radio Interferometric Positioning System (RIPS) is the fact that it does not require any sensors other than the radio used for wireless communication.

Radio and plasma wave observations at Saturn from Cassini's approach and first orbit.

Abstract: We report data from the Cassini radio and plasma wave instrument during the approach and first orbit at Saturn. During the approach, radio emissions from Saturn showed that the radio rotation period is now 10 hours 45 minutes 45 ± 36 seconds, about 6 minutes longer than measured by Voyager in 1980 to 1981. In addition, many intense impulsive radio signals were detected from Saturn lightning during the approach and first orbit. Some of these have been linked to storm systems observed by the Cassini imaging instrument. Within the magnetosphere, whistler-mode auroral hiss emissions were observed near the rings, suggesting that a strong electrodynamic interaction is occurring in or near the rings.

A size of ∼1 au for the radio source Sgr A* at the centre of the Milky Way

Abstract: Although it is widely accepted that most galaxies have supermassive black holes at their centres, concrete proof has proved elusive. Sagittarius A* (Sgr A*), an extremely compact radio source at the centre of our Galaxy, is the best candidate for proof, because it is the closest. Previous very-long-baseline interferometry observations (at 7 mm wavelength) reported that Sgr A* is ~2 astronomical units (au) in size, but this is still larger than the 'shadow' (a remarkably dim inner region encircled by a bright ring) that should arise from general relativistic effects near the event horizon of the black hole. Moreover, the measured size is wavelength dependent. Here we report a radio image of Sgr A* at a wavelength of 3.5 mm, demonstrating that its size is ~1 au. When combined with the lower limit on its mass11, the lower limit on the mass density is 6.5 × 10^21 M_⊙ pc^-3 (where M_⊙ is the solar mass), which provides strong evidence that Sgr A* is a supermassive black hole. The power-law relationship between wavelength and intrinsic size (size proportional to wavelength^1.09) explicitly rules out explanations other than those emission models with stratified structure, which predict a smaller emitting region observed at a shorter radio wavelength.

Nanoantennas for Light Emission

Abstract: Radio antennas have long been used to increase the amount of radiated power and modify the emission direction of the radio waves. In his Perspective, Greffet discusses recent attempts to apply these ideas to the design of optical antennas, which could find applications in quantum information processing and spectroscopy of nanometer-scale objects. The author highlights the report by MA¼hlschlegel et al. , who show that although optical antennas face challenges that are not encountered at radio wavelengths, radio antenna designs can nevertheless be reproduced successfully at optical wavelengths. Many other designs are being investigated in this rapidly expanding field.

Radio frequency IC tag and method for manufacturing same

Abstract: A small radio frequency IC tag which can obtain sufficiently long communication distance with radio wave in the microwave band even if an antenna is made small and the radio frequency IC tag is embedded in metal material. An O-shaped antenna is formed to narrow the width of a neck part in which an IC chip is mounted and widen the width of radiating electrodes constituting radiating part of radio wave. The radiating electrodes are formed into offset structure on right and left sides of the feeding point so that areas of right and left radiating parts of the feeding point in which the IC chip is mounted are unsymmetrical. Further, a ground electrode is provided so that a dielectric body is held between the radiating electrodes and the ground electrode and the radiating electrode is connected to the ground electrode at the side of the dielectric body.

Near-ground channel measurements over line-of-sight and forested paths

Abstract: Near-ground radio-wave propagation is of interest for emerging military applications such as battlefield sensor networks and for wireless communication between dismounted soldiers. Narrowband and wideband channel measurement results at 300 and 1900 MHz are presented for near-ground propagation, characterising the effect of antenna heights, radiation patterns and foliage environments. An additional set of channel measurements was performed to study the effect of rain on near-ground propagation at 1900 MHz in a forest environment. Measured power–delay profiles indicate significant multipath propagation with the multipath components becoming stronger relative to the direct path for decreasing antenna heights. In the LOS measurements, the RMS delay spread decreased with the use of directional antennas and increasing antenna heights, and increased with distance. This effect was not evident in the forest measurements, suggesting a larger angle spread of the multipaths. Measurement results indicate that leaves and wet foliage do not contribute significantly to the scattering of radio waves. Foliage effects are more significant at 1900 MHz than 300 MHz. Results from near-ground sensor measurements demonstrate that path-loss varies inversely with the square of the receiving antenna height, as in the plane-Earth and Egli models.

Radio wave propagation in potato fields

Abstract: Reliable communication is crucial for successful deployment of wireless sensor networks. Therefore, it is important to understand the impact of environmental conditions on the performance of the radios (Chipcon CC1000 transceivers) used in typical sensor nodes. This paper reports on an extensive set of measurements taken in a potato field, where the foliage has an important effect on the propagation of radio waves. The influence of the growth stage of the potato crop is significant. We observed a reduction of 15 dB in signal strength at 15 m between nodes, when a flowering crop is compared to a crop on its return. This effectively reduces the radio range from 23 m to 10 m. Another important result is that radio waves propagate better in conditions with a high humidity (i.e., at night and during rain). We attribute this to changes in the reflection coefficient of the top of the potato canopy.

Electron beams generated by shock waves in the solar corona

Abstract: Beams of energetic electrons can be generated by shock waves in the solar corona. At the Sun shock waves are produced either by flares and/or by coronal mass ejections (CMEs). They can be observed as type II bursts in the solar radio radiation. Shock accelerated electron beams appear as rapidly drifting emission stripes (so-called “herringbones”) in dynamic radio spectra of type II bursts. A large sample of type II bursts showing “herringbones” was statistically analysed with respect to their properties in dynamic radio spectra. The electron beams associated with the “herringbones” are considered to be generated by shock drift acceleration. Then, the accelerated electrons establish a shifted loss-cone distribution in the upstream region of the associated shock wave. Such a distribution causes plasma instabilities leading to the emission of radio waves observed as “herringbones”. Consequences of a shifted loss-cone distribution of the shock accelerated electrons are discussed in comparison with the observations of “herringbones” within solar type II radio bursts.

Deflection of Pulsar Signal Reveals Compact Structures in the Galaxy

Abstract: We have detected a strong deflection of radio waves from the pulsar PSR B0834+06 in scintillation observations. Interference between the undeflected pulsar image and deflected subimages allows single-dish interferometry of the interstellar medium with submilliarcsecond resolution. We infer the presence of scattering structure(s) similar to those that are thought to cause extreme scattering events in quasar flux monitoring programs: size ~0.2 AU (an angular size of 0.1 mas) with an electron overdensity of 103 compared to the warm ionized medium. The deflectors are nearly stationary in a scattering screen that is thin (5% of the pulsar-observer distance in extent), is located 70% of the way from the Earth to the pulsar, and has been seen consistently in observations dating back 20 years. The pulsar scans the scattering screen at a velocity of 110 km s-1 with a detection radius of 15 mas. Pulsar observations such as these—particularly with a new generation of low-frequency radio telescopes with large collecting areas—hold promise for improving constraints on the poorly understood physical characteristics and space density of the deflecting structures. Such observations may also prove useful in correcting deviations that the deflectors produce in high-precision timing of millisecond pulsars.

Communication by radio waves and optical waveguides

Abstract: The invention relates to improvements to full-duplex bi-directional opto-electrical transducers, primarily for use in radio-over-fiber installations, such as remote-antenna installations for cellular radio apparatus. The transducer is of the kind based on an electroabsorption modulator, and the first improvement consists in biasing it by means of a constant-current source rather than conventionally by directly setting a bias voltage. With appropriate selection of the EAM, a preset constant current source is considered adequate, but its setting may be adjusted to operating conditions by a control algorithm if found desirable. A second improvement consists in increasing the effective load impedance of the EAM by using an inductive load that forms a tuned circuit with the internal capacitance of the EAM, resonant at a frequency in the operating range.

Radio ic tag device and rfid system

Abstract: PROBLEM TO BE SOLVED: To provide a radio IC tag device which is simple in configuration, has high sensitivity, and can be mounted even on a metallic object or the like. SOLUTION: A radio wave polarization conversion resonance reflector D1, in which two patch conductors 2A and 2B and a grounding conductor 3 are formed on a dielectric substrate 1, is combined with a radio IC tag 4 to strengthen a current flowing through the tag antenna of the radio IC tag 4 by the plane resonance effect of the two patch conductors, thereby obtaining the compact and high-sensitive radio IC tag device. Further, the grounding conductor 3 is formed on the lower surface (mounting surface) of the dielectric substrate 1 to eliminate the radiation of radio waves (electric field components) to the side of the grounding conductor 3, thereby mounting the radio IC tag device T1 even on the metallic object, a container, in which liquid is stored, or the like. COPYRIGHT: (C)2007,JPO&INPIT

Tag device, antenna and portable card

Abstract: To perform high quality wireless communication in which radio wave radiation/reception characteristics do not deteriorate even in the vicinity of a human body and communication of other IC tags is not impeded. A main loop section (11) is a metal foil of elongated loop-shape having an area smaller than the area of a dielectric substrate (30), and mounted to contain the dielectric substrate (30) while covering the surface and side face thereof in the horizontal direction relative to the surface of the dielectric substrate (30) in order to transmit/receive a radio wave. A capacitive load section (12) is a metal foil provided, respectively, at both ends of the main loop section (11) covering the front surface of the dielectric substrate (30) and both ends of the main loop section (11) covering the back surface of the dielectric substrate (30) and has a load of capacitance component. A control section (20) is connected with the main loop section (11) and controls information through a radio wave.

Reversals of Radio Emission Direction in PSR B1822?09

Abstract: The pulse profile of pulsar B1822-09 exhibits a very peculiar kind of mode changing: a "precursor" appearing just in front of the main pulse (MP) exhibits periods of nulling, during which an interpulse (IP) becomes detectable at a rotation phase separated by roughly 180° from the precursor. We propose that this bizarre phenomenon, which requires an information transfer between the two components, occurs by means of a reversal of the direction of coherent radio emission generated in the same emission region. This interpretation naturally explains the lack of weak radio emission in the off-pulse regions, as well as the problem of information transfer between emission regions associated with the MP precursor and the IP. The reversals also imply nulling. The model has profound physical implications: (1) the mechanism of coherent radio emission must allow radiation into two, opposite, intermittently changing directions; and (2) the radio waves must be able to propagate through inner regions of the neutron star magnetosphere with strong magnetic field. Most importantly, the model implies inward radio emission in the pulsar magnetosphere.

Artificial optical emissions at HAARP for pump frequencies near the third and second electron gyro-harmonic

Abstract: Part of Special Issue "Atmospheric studies by optical methods" Abstract. High-power high-frequency radio waves beamed into the ionosphere cause plasma turbulence, which can ac- celerate electrons. These electrons collide with the F-layer neutral oxygen causing artificial optical emissions identi- cal to natural aurora. Pumping at electron gyro-harmonic frequencies has special significance as many phenomena change their character. In particular, artificial optical emis- sions become strongly reduced for the third and higher gyro- harmonics. The High frequency Active Auroral Research Program (HAARP) facility is unique in that it can select a frequency near the second gyro-harmonic. On 25 Febru- ary 2004, HAARP was operated near the third and passed through the second gyro-harmonic for the first time in a weakening ionosphere. Two novel observations are: firstly, a strong enhancement of the artificial optical emission in- tensity near the second gyro-harmonic, which is opposite to higher gyro-harmonics; secondly, the optical enhance- ment maximum occurs for frequencies just above the sec- ond gyro-harmonic. We provide the first experimental evi- dence for these effects, which have been predicted theoret- ically. In addition, irregular optical structures were created when the pump frequency was above the ionospheric critical frequency.

A parametric study of the numerical simulations of triggered VLF emissions

Abstract: This work is concerned with the numerical modelling of VLF emissions triggered in the equatorial region of the Earth’s magnetosphere, using a well established 1D Vlasov Hybrid Simulation (VHS) code. Although this code reproduces observed ground based emissions well there is some uncertainty regarding the magnitude of simulation parameters such as saturation wave amplitude, cold plasma density, linear growth rate and simulation bandwidth. Concentrating on emissions triggered by pulses of VLF radio waves from the transmitter at Siple Station, Antarctica (L=4.2), these parameters, as well as triggering pulse length and amplitude, are systematically varied. This parametric study leads to an understanding of the physics of the triggering process and also of how the properties of these emissions, particularly their frequency time profile, depend upon these parameters. The main results are that weak power input tends to generate fallers, intermediate power input gives stable risers and strong growth rates give fallers, hooks or oscillating tones. The main factor determining the frequency sweep rate - of either sign - turns out to be the cold plasma density, lower densities giving larger sweep rates.

Wireless power supply system

Abstract: PROBLEM TO BE SOLVED: To provide a system capable of supplying power wirelessly into a predetermined space. A power transmission system including an electromagnetic wave generating device that generates an electromagnetic wave having a predetermined frequency and intensity and an antenna that radiates the electromagnetic wave is installed at a predetermined position. The above problem can be realized by receiving the radiated electromagnetic wave by a power receiving system including a rectenna and converting it into electric power. If various electrical devices have rectennas, they will be able to solve the power supply problem that has been a drag on the realization of a ubiquitous society. Note that the frequency of electromagnetic waves is preferably in the ISM band, and the power density must be in accordance with the radio wave protection guidelines. [Selection] Figure 1

Creation of visible artificial optical emissions in the aurora by high-power radio waves.

Abstract: The powerful radio transmitter array at the HAARP observatory near Gakona, Alaska, is designed to transmit a narrow beam of powerful radio signals into the sky. The response to this intervention reveals details of the chemistry and physics of the ionosphere. One such experiment carried out in March 2004 had an unexpected outcome, inducing artificial optical emissions bright enough to be seen as small speckles by the naked eye. This occurred not in the quiet ionosphere, but in the midst of a pulsating aurora, and represents features much smaller and brighter than ever observed previously. Generation of artificial light in the sky by means of high-power radio waves interacting with the ionospheric plasma has been envisaged since the early days of radio exploration of the upper atmosphere, with proposed applications ranging from regional night-time street lighting to atmospheric measurements1. Weak optical emissions have been produced for decades in such ionospheric ‘heating’ experiments, where they serve as key indicators of electron acceleration, thermal heating, and other effects of incompletely understood wave–particle interactions in the plasma under conditions difficult to replicate in the laboratory2. The extremely low intensities produced previously have, however, required sensitive instrumentation for detection, preventing applications beyond scientific research. Here we report observations of radio-induced optical emissions bright enough to be seen by the naked eye, and produced not in the quiet mid-latitude ionosphere, but in the midst of a pulsating natural aurora. This may open the door to visual applications of ionospheric heating technology or provide a way to probe the dynamics of the natural aurora and magnetosphere.

Magnetic-Zenith Effect

Abstract: We develop a theory of the magnetic-zenith effect (MZE) observed upon the ionosphere modification by powerful radio waves. The dependences of MZE on main parameters, such as the magnetic-field inclination angle, pump-wave frequency and power, and angular width of HF beam are obtained. The optimal elevation angle of pump-wave beam is predicted.

Luxemburg-Gorky effect in a granular medium: Probing perturbations of the material state via cross-modulation of elastic waves

Abstract: A nonlinear effect consisting of transfer of modulation from one amplitude-modulated elastic wave, the "pump" wave, to the second initially monochromatic probe wave has been recently introduced in nonlinear acoustics by analogy with radio waves. For the first time, this effect is applied to probe perturbations of the state of a granular material induced by shocks, "seismic events". The experiments indicate a much stronger variability of the nonlinearity-induced modulation sidelobes in comparison with changes in the components at the fundamental frequencies of the probe and pump waves. Another new feature revealed in the experiments is that the transitional shock-induced variations in the amplitudes of the modulation sidelobes are several times stronger than the relaxed, residual values of the changes. The effects observed suggest interesting possibilities to application in active acoustic/seismic monitoring schemes.

Electron temperature enhancement effects on plasma irregularities associated with charged dust in the Earth's mesosphere

Abstract: [1] Recently, experimental observations have shown that Polar Mesospheric Summer Echoes (PMSE) may be modulated by radio wave heating the irregularity source region with a ground-based ionospheric heating facility. It is clear from these past investigations that the temporal behavior of PMSE during ionospheric heating shows promise as a diagnostic for the associated dust layer. To investigate the temporal behavior of plasma irregularities thought to produce PMSE, this work describes a new model that incorporates both finite diffusion time effects as well as dust charging. The hybrid model utilizes fluid ions described by continuity and momentum equations, electrons whose behavior is determined from quasi-neutrality, and charged dust described by the standard Particle-In-Cell (PIC) method. The model has been used to investigate the temporal behavior of charged dust associated electron irregularities during electron temperature enhancement associated with radio wave heating. The model predicts that the temporal behavior of the irregularities depends on the ratio of the electron-ion ambipolar diffusion time to the dust particle charging time τdif/τchg. The results indicate that typically for τdif/τchg ≪ 1, an enhancement in electron irregularity amplitude occurs for a period after turn-off of the radio wave heating. The work also predicts that for τdif/τchg ≫ 1, an enhancement in electron irregularity amplitude occurs for a time period after the turn-on of the radio wave heating. Owing to the dependence of τdif on irregularity scale size, these results have important implications for observations of PMSE modification at different radar frequencies. Therefore new possibilities may exist for diagnosing the dust layer with radio wave heating which are discussed.

Reverse Shock Emission as a Probe of GRB Ejecta

Abstract: We calculate the reverse shock (RS) synchrotron emission in the optical and the radio wavelength bands from electron-positron pair enriched gamma-ray burst ejecta with the goal of determining the pair content of GRBs using early time observations. We take into account an extensive number of physical effects that influence radiation from the reverse-shock heated GRB ejecta. We find that optical/IR flux depends very weakly on the number of pairs in the ejecta, and there is no unique signature of ejecta pair enrichment if observations are confined to a single wavelength band. It may be possible to determine if the number of pairs per proton in the ejecta is > 100 by using observations in optical and radio bands; the ratio of flux in the optical and radio at the peak of each respective reverse-shock light curve is dependent on the number of pairs per proton. We also find that over a large parameter space, RS emission is expected to be very weak; GRB 990123 seems to have been an exceptional burst in that only a very small fraction of the parameter space produces optical flashes this bright. Also, it is often the case that the optical flux from the forward shock is brighter than the reverse shock flux at deceleration. This could be another possible reason for the paucity of prompt optical flashes with a rapidly declining light curve at early times as was seen in 990123 and 021211. Some of these results are a generalization of similar results reported in Nakar & Piran (2004).

Wireless device with distributed load

Abstract: A wireless device (100) includes a first circuit board (102), a second circuit board (104), and a distributed load (106) having an inductive coupling (112) and a capacitive coupling (114). The inductive coupling (112) and the capacitive coupling (114) form a parallel resonance at predefined frequencies of interest. The second circuit board (104) includes an antenna (116) for receiving and transmitting radio waves.

Radio Wave Emission from the Outer Planets Before Cassini

Abstract: We review observations and theories of radio wave emissions from the outer planets. These include radio emissions from the auroral regions and from the radiation belts, low-frequency electromagnetic emissions, and atmospheric lightning. For each of these emissions, we present in more details our knowledge of the Saturn counterpart, as well as expectations for Cassini. We summarize the capabilities of the radio instrument onboard Cassini, observations performed during the Jupiter flyby, and first (remote) observations of Saturn. Open questions are listed along with the specific observations that may bring responses to them. The coordinated observations (from the ground and from space) that would be valuable to perform in parallel to Cassini measurements are briefly discussed. Finally, we outline future missions and perspectives.

Appliance control apparatus and electrical appliance

Abstract: Power is taken out from radio waves through an antenna and a power receiving unit. A signal receiver, a comparator, and an ID signal holder are operated with the taken-out power to compare an ID contained in a received signal with an ID read out from the ID signal holder. When both the ID's are matched with each other, a switch for a main power source is turned on. In trying to remotely operate household electrical appliances by utilizing the Internet that has become increasingly popular, standby power is consumed if the electrical appliances are kept in a standby state at all times. Since power is taken out from radio waves, the invention is able to cut the standby power in an environment where the radio waves are transferred via radio communication that is expected to be more and more prevalent in future.

Mobile device and radio interface arrangement method

Abstract: A transmitter/receiver 101 on a mobile body 10 utilizes a plurality of antennas 100. It is assumed that a plurality of the antennas 100 are distributed and arranged in a moving direction of the mobile body, and the antennas at both ends are away from each other at an extent that a distance between the antennas is not negligible as compared with an interval of the base station. A radio wave from the base station 102-1 is stronger in intensity in 100-1 than in the center, and the radio wave from the base station 102-2 is stronger in intensity in 100-2 than in the center, respectively, whereby the communication stabilization effect, which is larger as compared with the case that the antennas are locally located in the center, is expected. This enables the interval of the base station, which is broader than the conventional one, to be employed, yet both of a speed and a frequency of a hand-over process to be lowered, and in addition hereto, the bandwidth utilization efficiency, which is higher as compared with that of the conventional example, to be realized.

Radio communication system, radio communication device, and radio communication method

Abstract: A radio communication system performs data communication by a backscatter system using absorption and reflection of a received radio wave. In the system, a data reading device transmits an unmodulated carrier of frequency f O ; a data transmitting device subjects transmission data to primary modulation using a center frequency f S to obtain a primary modulated signal, and subjects the primary modulated signal to secondary modulation by multiplying the primary modulated signal by an input of the unmodulated carrier of the backscatter system to generate a reflected modulated wave in which one of frequencies f O +f S and f O −f S is suppressed; and the data reading device receives the reflected modulated wave from the data transmitting device.

Radio wave absorber

Abstract: PROBLEM TO BE SOLVED: To provide a radio wave absorber good in weather resistance, bending workability, productivity, etc SOLUTION: The transparent radio wave absorber comprises a transparent dielectric layer 1 between a transparent resistance film 3 containing very thin conductive fibers and a light-permeable radio wave reflector 2 The very thin conductive fibers in the resistance film disperse to mutually contact without cohesively aggregating, concretely, disperse separately one fiber from another or one bundle of a plurality of collected fibers from another and mutually contact The resistance film containing the very thin conductive fibers has a good transparency and a good weather resistance enough to eliminate fear of deteriorating for a short time to deteriorate the performance of the transparent radio wave absorber, and, if the transparent radio wave absorber is secondary-bending-worked later, the very thin conductive fibers keep mutually contacted enough to hardly raise the surface resistivity COPYRIGHT: (C)2006,JPO&NCIPI

Wind influence on radio waves propagating through vegetation at 1.8 GHz

Abstract: The impact of moving vegetation on propagating radio waves under the influence of wind had been investigated. It was found that the fast-fading component of the vegetation-shadowed signal, originating from a line-of-sight (LOS) transmitter, resembles a Rician distribution. From the measured data, a new empirical model at 1.8 GHz of the Rician k-factor has been proposed. The model characterizes the dynamic impact of the wind influence for radio waves propagating through vegetation. The proposed model was then assessed against a different set of measured data and was found to be in close agreement.