Showing papers on "Radio wave published in 2010"

Sensitive Broadband ELF/VLF Radio Reception With the AWESOME Instrument

Abstract: A new instrument has been developed and deployed for sensitive reception of broadband extremely low frequency (ELF) (defined in this paper as 300-3000 Hz) and very low frequency (VLF) (defined in this paper as 3-30 kHz) radio signals from natural and man-made sources, based on designs used for decades at Stanford University. We describe the performance characteristics of the Atmospheric Weather Electromagnetic System for Observation, Modeling, and Education (AWESOME) instrument, including sensitivity, frequency and phase response, timing accuracy, and cross modulation. We also describe a broad range of scientific applications that use AWESOME ELF/VLF data involving measurements of both subionospherically and magnetospherically propagating signals.

Observation of Ultrahigh-Energy Cosmic Rays with the ANITA Balloon-Borne Radio Interferometer

Abstract: We report the observation of 16 cosmic ray events with a mean energy of 1.5x10{sup 19} eV via radio pulses originating from the interaction of the cosmic ray air shower with the Antarctic geomagnetic field, a process known as geosynchrotron emission. We present measurements in the 300-900 MHz range, which are the first self-triggered, first ultrawide band, first far-field, and the highest energy sample of cosmic ray events collected with the radio technique. Their properties are inconsistent with current ground-based geosynchrotron models. The emission is 100% polarized in the plane perpendicular to the projected geomagnetic field. Fourteen events are seen to have a phase inversion due to reflection of the radio beam off the ice surface, and two additional events are seen directly from above the horizon. Based on a likelihood analysis, we estimate angular pointing precision of order 2 deg. for the event arrival directions.

Properties of Saturn kilometric radiation measured within its source region

Abstract: On 17 October 2008, the Cassini spacecraft crossed the southern sources of Saturn kilometric radiation (SKR), while flying along high-latitude nightside magnetic field lines. In situ measurements allowed us to characterize for the first time the source region of an extra-terrestrial auroral radio emission. Using radio, magnetic field and particle observations, we show that SKR sources are surrounded by a hot tenuous plasma, in a region of upward field-aligned currents. Magnetic field lines supporting radio sources map a continuous, high-latitude and spiral-shaped auroral oval observed on the dawnside, consistent with enhanced auroral activity. Investigating the Cyclotron Maser Instability (CMI) as a mechanism responsible for SKR generation, we find that observed cutoff frequencies are consistent with radio waves amplified perpendicular to the magnetic field by hot (6 to 9 keV) resonant electrons, measured locally.

Creation of artificial ionospheric layers using high‐power HF waves

Abstract: : We report the first evidence of artificial ionospheric plasmas reaching sufficient density to sustain interaction with a high-power HF pump beam produced by the 3.6 MW High-Frequency Active Auroral Program (HAARP) transmitter in Gakona, Alaska. The HF-driven ionization process is initiated near the 2nd electron gyroharmonic at 220 km altitude in the ionospheric F region. Once the artificial plasma reaches sufficient density to support interaction with the transmitter beam it rapidly descends as an ionization wave to approximately 150 km altitude. Although these initial artificial layers appear to be dynamic and highly structured, this new ability to produce significant artificial plasma in the upper atmosphere opens the door to a new regime in ionospheric radio wave propagation where transmitter-produced plasmas dominate over the natural ionospheric plasma and may eventually be employed as active components of communications, radar, and other systems.

New method for the time calibration of an interferometric radio antenna array

Abstract: Digital radio antenna arrays, like LOPES (LOFAR PrototypE Station), detect high-energy cosmic rays via the radio emission from atmospheric extensive air showers. LOPES is an array of dipole antennas placed within and triggered by the KASCADE-Grande experiment on site of the Karlsruhe Institute of Technology, Germany. The antennas are digitally combined to build a radio interferometer by forming a beam into the air shower arrival direction which allows measurements even at low signal-to-noise ratios in individual antennas. This technique requires a precise time calibration. A combination of several calibration steps is used to achieve the necessary timing accuracy of about 1 ns. The group delays of the setup are measured, the frequency dependence of these delays (dispersion) is corrected in the subsequent data analysis, and variations of the delays with time are monitored. We use a transmitting reference antenna, a beacon, which continuously emits sine waves at known frequencies. Variations of the relative delays between the antennas can be detected and corrected for at each recorded event by measuring the phases at the beacon frequencies.

Effect of sporadic E clouds on GPS radio occultation signals

Abstract: [1] In this study the effects of sporadic E (Es) clouds on GPS radio occultation (RO) signals are investigated by modeling wave propagation and analyzing observational GPS RO data. It has been shown that when the Es clouds are aligned with the propagation direction, they cause defocusing of the GPS RO signal, accompanied by scintillation above and below the defocusing region (due to the interference of direct and refracted radio waves). These effects result in specific U-shape structures in the amplitude of the GPS RO signals. When Es clouds are tilted with respect to the propagation direction, the effects reduce and disappear with the increase of the tilt angle. The U-shape structures are clearly identified in the observed GPS RO signals mainly at tangent point (TP) heights 90–120 km, but also at much lower TP heights. The latter indicates that some Es clouds are tilted with respect to the local horizon (this has also been shown in other studies). The distributions of the observed U-shape structures in latitude, local time, tilt angle, and vertical thickness of the cloud are evaluated in this study based on one month of COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) RO data in July 2009.

Beam Efficiency of Wireless Power Transmission via Radio Waves from Short Range to Long Range

Abstract: Wireless power transmission (WPT) is useful technology in near future. There are some kinds of the WPT technologies, WPT via radio waves, resonance coupling, and inductive. Especially the WPT via radio waves is used for multi-purposes from short range to long range application. However, unfortunately it is misunderstood that it is low efficiency and low power. In this paper, I show the theory of beam efficiency between transmitting antennas and receiving antennas and also show some high efficient applications of the WPT via radio waves. Especially, I pick up a wireless power charging system of an electric vehicle and show the experimental results. I show difference between the theory of beam efficiency and the experimental results of short range WPT. I indicate that reasons of poor beam efficiency in the experiment are (1) change of impedance caused by mutual coupling between transmitting antennas and receiving antennas, (2) oblique direction of microwave power to receiving antennas caused by short distance.

RF communications in underwater wireless sensor networks

Abstract: We investigate the propagation of radio waves underwater and between water and air to facilitate setting up hybrid wireless sensor networks with both surface and subsurface nodes. Our investigation includes signal attenuation, antenna radiation patterns, multipath due to reflections from the surface and substrate, noise, and reflection losses transmitting from one medium to another.

The Lunar Radar Sounder (LRS) Onboard the KAGUYA (SELENE) Spacecraft

Abstract: The Lunar Radar Sounder (LRS) onboard the KAGUYA (SELENE) spacecraft has successfully performed radar sounder observations of the lunar subsurface structures and passive observations of natural radio and plasma waves from the lunar orbit. After the transfer of the spacecraft into the final lunar orbit and antenna deployment, the operation of LRS started on October 29, 2007. Through the operation until June 10, 2009, 2363 hours worth of radar sounder data and 8961 hours worth of natural radio and plasma wave data have been obtained. It was revealed through radar sounder observations that there are distinct reflectors at a depth of several hundred meters in the nearside maria, which are inferred to be buried regolith layers covered by a basalt layer with a thickness of several hundred meters. Radar sounder data were obtained not only in the nearside maria but also in other regions such as the farside highland region and polar region. LRS also performed passive observations of natural plasma waves associated with interaction processes between the solar wind plasma and the moon, and the natural waves from the Earth, the sun, and Jupiter. Natural radio waves such as auroral kilometric radiation (AKR) with interference patterns caused by the lunar surface reflections, and Jovian hectometric (HOM) emissions were detected. Intense electrostatic plasma waves around 20 kHz were almost always observed at local electron plasma frequency in the solar wind, and the electron density profile, including the lunar wake boundary, was derived along the spacecraft trajectory. Broadband noises below several kHz were frequently observed in the dayside and wake boundary of the moon and it was found that a portion of them consist of bipolar pulses. The datasets obtained by LRS will make contributions for studies on the lunar geology and physical processes of natural radio and plasma wave generation and propagation.

Forecasting low-latitude radio scintillation with 3-D ionospheric plume models: 2. Scintillation calculation

Abstract: [1] A three-dimensional model has been developed for the plasma plumes caused by interchange instabilities in the low-latitude ionosphere to describe the structure and extent of the radio scintillation generated by turbulence around and within the plumes. With the inclusion of the processes that determine the transport of plasma parallel to the geomagnetic field lines as well as transverse to them, the model can predict the extent in latitude of the plumes and their scintillation. Diagnostics presented here include illustrations of the spectral density of the density irregularities that develop within the plumes. An extrapolation of the density irregularity spectrum down into the wavelength regime effective for radio wave scattering permits a phase screen calculation of the amplitude scintillation caused by the plumes. The scintillation produced by the model has much the same character as measurements of scintillation do in terms of the time and rate of onset of scintillation, duration, and latitudinal extent.

GPS Total Electron Content (TEC) Prediction at Ionosphere Layer over the Equatorial Region

Abstract: Space weather is a fairly new field in science today and has very interesting effects on humans, environment and technology in general. Scientists are now studying space weather with a wide range of tools to try to learn more about the physical and chemical processes taking place in the upper atmosphere and beyond. One of these tools is Global Positioning System (GPS). GPS is currently one of the most popular global satellite positioning systems due to global availability of signal as well as performance. GPS is a satellite-based navigation radio system which is used to verify the position and time in space and on the Earth. GPS nowadays allows to measure positions in real time with an accuracy of few centimetres (Warnant et al., 2007). The advent of GPS has led to technical revolutions in navigation as well as in fields related to surveying. The GPS system - an all-weather satellite-based radio navigation system - can provide users on a world-wide basis with navigation, positioning, and time information which is not possible with conventional navigation and surveying methods. Apart from geodesy and geophysical interest, GPS has great importance in scientific applications. The GPS satellites that are orbiting the Earth, at altitudes of about 20,200 km, transmit signals that propagate through the ionosphere that exists at about 60 –1500 km above the Earth’s surface. The signals from the GPS satellites travel through the ionosphere on their way to receivers on the Earth’s surface. The free electrons populating this region of the atmosphere affect the propagation of the signals, changing their velocity and direction of travel as shown at figure 1. Due to the inhomogeneity of the propagation medium in the ionosphere, the GPS signal does not travel along a perfectly straight line (Ioannides & Strangeways, 2000). The effects of the ionosphere can cause range-rate errors for users of the GPS satellites who require high accuracy measurements (Bradford & Spilker, 1996). Ionosphere is highly variable in space and time (sunspot cycle, seasonal, and diurnal), with geographical location (polar, aurora zones, mid-latitudes and equatorial regions), and with certain solar-related ionospheric disturbances. Ionosphere research attracts significant attention from the GPS community because ionosphere range delay on GPS signals is a major error source in GPS positioning and navigation. The ionosphere has practical importance in GPS applications because it influences the transionospheric radio wave

Bridging the Gap Between Plasmonics and Zenneck Waves

Abstract: Due to the broad spectrum and versatility of electromagnetics, progress and new discoveries in this field have not made a uniform history. The same and similar phenomena are reinvented by researchers whose interests center on different frequency ranges. Surface waves make an illustrating example. Starting from the works of Sommerfeld and Zenneck, the theory of radio waves over ground was developed during the early and mid-20th century. In the latter part of the century, surface waves were independently studied from the point of view of localization of radiation, in connection with the optical properties of metals. The most-recent development of the present century is that plasmonics and terahertz applications meet microwave studies in the framework of the new discipline of metamaterials. The present article tries to bridge the gaps of surface waves over the various spectral ranges. The paper discusses the properties of the generalized Zenneck wave, including phase and attenuation characteristics of structures with different materials (dielectric, epsilon-near-zero, negative-permittivity plasmonic), backward-wave regimes, polarization properties, and singularities that take place when the ratio of the permittivities of the two media is -1.

On the generation of ELF/VLF waves for long‐distance propagation via steerable HF heating of the lower ionosphere

Abstract: [1] ELF/VLF radio waves (300 Hz to 30 kHz) have been successfully generated via modulated HF (3–10 MHz) heating of the lower ionosphere in the presence of natural currents, most recently with the HAARP facility in Alaska. Generation is possible via amplitude modulation or via two techniques involving motion of the HF beam during the ELF/VLF cycle, known as beam painting and geometric modulation, described and measured by Cohen et al. (2010b). In this paper, we describe a theoretical model describing the HF heating and ionospheric responses, followed by a full-wave calculation of ELF/VLF propagation, and utilize this end-to-end model to derive the predicted radiated ELF/VLF pattern up to 1000 km from the HF heater in the Earth-ionosphere waveguide. We quantitatively compare the generated ELF/VLF signals on the ground from various generation techniques and find it to be generally in agreement with earlier measurements. We apply a simplified ELF/VLF propagation model to quantify the contribution of the ELF/VLF phased array in the radiation pattern resulting from geometric modulation and find this contribution to be significant. We also use a limited HF heating model to quantify the degree to which the current power level of HAARP is sufficient for the beam painting technique, since this technique requires high HF power densities at high altitudes.

Recent results of zebra patterns in solar radio bursts

Abstract: This review covers the most recent experimental results and theoretical re- search on zebra patterns (ZPs) in solar radio bursts. The basic attention is given to events with new peculiar elements of zebra patterns received over the last few years. All new properties are considered in light of both what was known earlier and new theoretical models. Large-scale ZPs consisting of small-scale fiber bursts could be explained by simultaneous inclusion of two mechanisms when whistler waves "high- light" the levels of double plasma resonance (DPR). A unique fine structure was ob- served in the event on 2006 December 13: spikes in absorption formed dark ZP stripes against the absorptive type III-like bursts. The spikes in a bsorption can appear in ac- cordance with well known mechanisms of absorptive bursts. The additional injection of fast particles filled the loss-cone (breaking the loss-co ne distribution), and the gen- eration of the continuum was quenched at these moments. The maximum absorptive effect occurs at the DPR levels. The parameters of millisecond spikes are determined by small dimensions of the particle beams and local scale heights in the radio source. Thus, the DPR model helps to understand several aspects of unusual elements of ZPs. However, the simultaneous existence of several tens of the DPR levels in the corona is impossible for any realistic profile of the plasma density an d magnetic field. Three new theories of ZPs are examined. The formation of eigenmodes of transparency and opac- ity during the propagation of radio waves through regular coronal inhomogeneities is the most natural and promising mechanism. Two other models (nonlinear periodic space - charge waves and scattering of fast protons on ion-sound harmonics) could happen in large radio bursts.

Location determination using radio wave measurements and pressure measurements

Abstract: A method and apparatus for determining a location of a wireless device using radio waves and pressure measurements is disclosed. In one embodiment, a plurality of Radio Signal Strength (RSS) measurements are used to trilaterate an approximate location of the wireless device. The wireless device also takes pressure measurements that are compared with a second pressure measurement made by at least one other pressure sensor at a known elevation and in a local area near the wireless device. This comparison is used to generate an accurate estimate of the elevation of the wireless device. The accurate estimate of elevation may be combined with the RSS measurements to yield an accurate estimate of the location of the wireless device.

Wireless communication system

Abstract: A radio communication system according to the present invention includes a scatterer configured to reflect, refract, or transmit a radio wave radiated primarily from a transmission side apparatus to radiate the radio wave secondarily to a desired area and a metamaterial is used for the scatterer.

Radio-Wave Propagation Into Large Building Structures—Part 1: CW Signal Attenuation and Variability

Abstract: We report on our investigation into radio communications problems faced by emergency responders in disaster situations. A fundamental challenge to communications into and out of large buildings is the strong attenuation of radio signals caused by losses and scattering in the building materials and structure. Another challenge is the large signal variability that occurs throughout these large structures. We designed experiments in various large building structures in an effort to quantify continuous wave (CW) radio-signal attenuation and variability throughout twelve large structures. We carried radio frequency transmitters throughout these structures and placed receiving systems outside the structures. The transmitters were tuned to frequencies near public safety, cell phone bands, as well as ISM and wireless LAN bands. This report summarizes the experiments, performed in twelve large building structures. We describe the experiments, detail the measurement system, show primary results of the data we collected, and discuss some of the interesting propagation effects we observed.

ELF/VLF wave generation via ionospheric HF heating: Experimental comparison of amplitude modulation, beam painting, and geometric modulation

Abstract: [1] Generation of ELF/VLF radio waves (300 Hz to 10 kHz) is achievable via modulation of natural currents in the lower ionosphere with high-power HF (2–10 MHz) heating Recently, Cohen et al (2008b) put forth an alternative to conventional amplitude HF power modulation, therein referred to as geometric modulation, in which the HF ionospheric heating beam is geometrically steered at the desired ELF/VLF frequency, and found 7–11 dB enhanced amplitudes, and ∼14 dB directional dependence for the thus generated ELF/VLF waves, compared to vertical amplitude modulation In this paper, we quantitatively compare amplitude modulation, geometric modulation, and a previously proposed technique known as beam painting, wherein the HF beam is rapidly moved over a wide area during the on portion of amplitude modulation in order to create a larger heated region in the ionosphere We experimentally analyze both the total generation and the directionality, ie, the suitability of each technique to direct signals along a chosen azimuth Among the three methods, geometric modulation is found to be uniquely well suited for both goals We also conduct experiments to investigate two particular physical effects and their role in generation efficacy: that of heat-cool duty cycle and the oblique angle of the HF heating beam It is found that both duty cycle and the oblique angle of the beam have small but counteracting impacts, consistent with the notion that the primary physical process responsible for generation enhancement in geometric modulation is that of formation of an effective multielement phased array

A Forecasting Ionospheric Real‐time Scintillation Tool (FIRST)

Abstract: [1] Transionospheric radio waves propagating through an irregular ionosphere with plasma depletions, or “bubbles,” are subject to sporadic enhancement and fading commonly referred to as scintillation. Knowledge of the current ionospheric condition allows system operators to distinguish between compromises due to the radio environment and system induced failures, while a forecast of the same provides the opportunity for operators to take appropriate actions to mitigate the effects and optimize service. This paper describes a technique that uses the readily accessible ionospheric characteristic h′F from ground-based ionospheric sounder data near the geomagnetic equator to forecast the occurrence or nonoccurrence of low-latitude scintillation activity in VHF/UHF bands. We illustrate the development of the Forecasting Ionospheric Real-time Scintillation Tool and its real-time capability for forecasting scintillation activity. Finally, we have found that there exists a threshold in the h′F value at 1930 LT that corresponds to the onset of scintillation activity in the Peruvian longitude sector, which is found to decrease with decreasing F10.7 cm fluxes in a linear manner.

3.125 Gb/s Impulse Radio Ultra-Wideband Photonic Generation and Distribution Over a 50 km Fiber With Wireless Transmission

Abstract: A 3.125 Gb/s photonic impulse radio ultra-wideband signal is created using the incoherent optical field summation resulting from the cross gain modulation of an uncooled distributed feedback laser injected with an external cavity laser. After 50 km of fiber and wireless transmission over 2.9-3.3-m, successful detection using a digital signal processing receiver is achieved.

Anomalous pre-seismic transmission of VHF-band radio waves resulting from large earthquakes, and its statistical relationship to magnitude of impending earthquakes

Abstract: SUMMARY To confirm the relationship between anomalous transmission of VHF-band radio waves and impending earthquakes, we designed a new data-collection system and have documented the anomalous VHF-band radio-wave propagation beyond the line of sight prior to earthquakes since 2002 December in Hokkaido, northern Japan. Anomalous VHF-band radio waves were recorded before two large earthquakes, the Tokachi-oki earthquake (Mj= 8.0, Mj: magnitude defined by the Japan Meteorological Agency) on 2003 September 26 and the southern Rumoi sub-prefecture earthquake (Mj= 6.1) on 2004 December 14. Radio waves transmitted from a given FM radio station are considered to be scattered, such that they could be received by an observation station beyond the line of sight. A linear relationship was established between the logarithm of the total duration time of anomalous transmissions (Te) and the magnitude (M) or maximum seismic intensity (I) of the impending earthquake, for M4-M5 class earthquakes that occurred at depths of 48–54 km beneath the Hidaka Mountains in Hokkaido in 2004 June and 2005 August. Similar linear relationships are also valid for earthquakes that occurred at different depths. The relationship was shifted to longer Te for shallower earthquakes and to shorter Te for deeper ones. Numerous parameters seem to affect Te, including hypocenter depths and surface conditions of epicentral area (i.e. sea or land). This relationship is important because it means that pre-seismic anomalous transmission of VHF-band waves may be useful in predicting the size of an impending earthquake.

Radio communication device, and radio communication method

Abstract: PROBLEM TO BE SOLVED: To provide a radio communication device and radio communication method in which communication with excellent radio quality can be performed by transmitting a radio wave to another node while using the same antenna as an antenna that receives and selects a radio wave from the other node (an antenna having the best radio quality at a time point of reception). SOLUTION: The radio communication device 11 includes: a plurality of antennas 1 each for exchanging a radio wave with another node 12; an antenna selection section 2a for selecting one antenna 1 according to a radio wave strength from among the antennas 1 receiving radio waves from the other node 12; a route determination section 4a for making the one antenna 1 selected by the antenna selection section 2a correspond to the other node 12 whose radio wave is received by the one antenna 1; and an antenna-to-be-used determination section 4d for determining the antenna 1 to transmit the radio wave to the other node 12 on the basis of information about the other node 12 and the antenna 1 made correspondent by the route determination section 4a. COPYRIGHT: (C)2010,JPO&INPIT

Radio-Wave Propagation Into Large Building Structures—Part 2: Characterization of Multipath

Abstract: We report on measurements that characterize multipath conditions that affect broadband wireless communications in building penetration scenarios. Measurements carried out in various large structures quantify both radio-signal attenuation and distortion (multipath) in the radio propagation channel. Our study includes measurements of the complex, wideband channel transfer function and bandpass measurements of a 20 MHz-wide, digitally modulated signal. From these, we derive the more compact metrics of time delay spread, total received power and error vector magnitude that summarize channel characteristics with a single number. We describe the experimental set-up and the measurement results for data collected in representative structures. Finally, we discuss how the combination of propagation metrics may be used to classify different propagation channel types appropriate for public-safety applications.

Fog attenuation on V band terrestrial radio and a low-cost measurement setup

Abstract: This paper is focused on the attenuation of radio waves on fixed, V band terrestrial link due to fog. Besides of the V band, fog attenuation measurements on a parallel operating Ka band radio link will be also shown. First of all the appropriate ITU-R recommendation is applied to calculate fog attenuation between moderate and dense fog conditions for different path length and temperatures, and it will be compared with real measurement data. Afterwards a new, simple optical fog density measurement setup will be introduced. The correct operation of the fog sensor is demonstrated by measurements; furthermore the calibration process, which is based on the measured attenuation, will be also shown. It will be proved that the sensor is capable to measure the liquid water content (LWC) and the attenuation can be predicted from this value. The outcome of this research is the applicability of this new device in the design process of V or higher band radio and FSO (Free Space Optics) links.

Radio frequency positioning system for vehicles

Abstract: A positioning system for radio frequency devices includes a two-way radio antenna, for vehicles, having a transmitting and a receiving element. Reference antennas have retro-directive arrays which can shape the signal beams in elevation; polarize transmission and reception signals according to a circular or a linear polarization, the polarized transmission retro-directively reflecting signals having the same polarization as the incident ones in the case of circular polarization, or retro-directively reflecting signals having orthogonal polarization in the case of linear polarization. An encoder is included for transmitting an identification code of the reference antenna. A controller processes the spatial and temporal data resulting from communication through the radio waves transmitted and received by the vehicle antennas and reflected by the reference antennas. The controller calculates the distance of the vehicle from the reference antennas that have reflected the signal transmitted by the antennas.

Radar vehicle detection system

Abstract: A radar parking detection system with a Ultra Wide Band (UWB) detection and transmission system including a hardened radar device placed in the vicinity of a parking space to be monitored by using measurements of time delays observed in the reflection of radio waves reflected from objects in the proximity of the transmitted waves and further including a hardened electronic sensor using (UWB) frequencies to determine the presence or absence of a vehicle in the parking space at close range; and a radio transmitter using multiple data transmission to limit the amount of lost data and to communicate changes in status of the parking space.