Showing papers on "Radio wave published in 2014"

Optical detection of radio waves through a nanomechanical transducer

Abstract: A room-temperature nanomechanical transducer that couples efficiently to both radio waves and light allows radio-frequency signals to be detected as an optical phase shift with quantum-limited sensitivity Many applications, from medical imaging and radio astronomy to navigation and wireless communication, depend on the faithful transmission and detection of weak radio-frequency microwaves Here Eugene Polzik and co-workers demonstrate a completely new capability in this area — the conversion of weak radio waves into laser signals using a nanomechanical oscillator The oscillator, a membrane made from silicon nitride, can couple simultaneously to radio signals and light reflected off its surface and this feature can be used to measure the radio signals as optical phase shifts, with quantum-limited sensitivity Compared to existing detectors, this approach has the advantage of working at room temperature, and the signals produced can be readily transferred into standard optical fibres Low-loss transmission and sensitive recovery of weak radio-frequency and microwave signals is a ubiquitous challenge, crucial in radio astronomy, medical imaging, navigation, and classical and quantum communication Efficient up-conversion of radio-frequency signals to an optical carrier would enable their transmission through optical fibres instead of through copper wires, drastically reducing losses, and would give access to the set of established quantum optical techniques that are routinely used in quantum-limited signal detection Research in cavity optomechanics1,2 has shown that nanomechanical oscillators can couple strongly to either microwave3,4,5 or optical fields6,7 Here we demonstrate a room-temperature optoelectromechanical transducer with both these functionalities, following a recent proposal8 using a high-quality nanomembrane A voltage bias of less than 10 V is sufficient to induce strong coupling4,6,7 between the voltage fluctuations in a radio-frequency resonance circuit and the membrane’s displacement, which is simultaneously coupled to light reflected off its surface The radio-frequency signals are detected as an optical phase shift with quantum-limited sensitivity The corresponding half-wave voltage is in the microvolt range, orders of magnitude less than that of standard optical modulators The noise of the transducer—beyond the measured Johnson noise of the resonant circuit—consists of the quantum noise of light and thermal fluctuations of the membrane, dominating the noise floor in potential applications in radio astronomy and nuclear magnetic imaging Each of these contributions is inferred to be when balanced by choosing an electromechanical cooperativity of with an optical power of 1 mW The noise temperature of the membrane is divided by the cooperativity For the highest observed cooperativity of , this leads to a projected noise temperature of 40 mK and a sensitivity limit of Our approach to all-optical, ultralow-noise detection of classical electronic signals sets the stage for coherent up-conversion of low-frequency quantum signals to the optical domain8,9,10,11

Probing the radio emission from air showers with polarization measurements

Abstract: The emission of radio waves from air showers has been attributed to the so-called geomagnetic emission process. At frequencies around 50 MHz this process leads to coherent radiation which can be observed with rather simple setups. The direction of the electric field induced by this emission process depends only on the local magnetic field vector and on the incoming direction of the air shower. We report on measurements of the electric field vector where, in addition to this geomagnetic component, another component has been observed that cannot be described by the geomagnetic emission process. The data provide strong evidence that the other electric field component is polarized radially with respect to the shower axis, in agreement with predictions made by Askaryan who described radio emission from particle showers due to a negative charge excess in the front of the shower. Our results are compared to calculations which include the radiation mechanism induced by this charge-excess process.

Constraints on the emission geometries and spin evolution of gamma-ray millisecond pulsars

Abstract: Millisecond pulsars (MSPs) are a growing class of gamma-ray emitters. Pulsed gamma-ray signals have been detected from more than 40 MSPs with the Fermi Large Area Telescope (LAT). The wider radio beams and more compact magnetospheres of MSPs enable studies of emission geometries over a broader range of phase space than non-recycled radio-loud gamma-ray pulsars. We have modeled the gamma-ray light curves of 40 LAT-detected MSPs using geometric emission models assuming a vacuum retarded-dipole magnetic field. We modeled the radio profiles using a single-altitude hollow-cone beam, with a core component when indicated by polarimetry; however, for MSPs with gamma-ray and radio light curve peaks occurring at nearly the same rotational phase we assume that the radio emission is co-located with the gamma rays and caustic in nature. The best-fit parameters and confidence intervals are determined using a maximum likelihood technique. We divide the light curves into three model classes, with gamma-ray peaks trailing (Class I), aligned (Class II) or leading (Class III) the radio peaks. Outer gap and slot gap (two-pole caustic) models best fit roughly equal numbers of Class I and II, while Class III are exclusively fit with pair-starved polar cap models. Distinguishing between the model classes based on typical derived parameters is difficult. We explore the evolution of magnetic inclination angle with period and spin-down power, finding possible correlations. While the presence of significant off-peak emission can often be used as a discriminator between outer gap and slot gap models, a hybrid model may be needed.

MAGIC gamma-ray and multi-frequency observations of flat spectrum radio quasar PKS 1510 089 in early 2012

Abstract: Aims. Amongst more than fifty blazars detected in very high energy (VHE, E> 100 GeV) γ rays, only three belong to the subclass of flat spectrum radio quasars (FSRQs). The detection of FSRQs in the VHE range is challenging, mainly because of their soft spectra in the GeV-TeV regime. MAGIC observed PKS 1510−089 (z = 0.36) starting 2012 February 3 until April 3 during a high activity state in the high energy (HE, E> 100 MeV) γ-ray band observed by AGILE and Fermi. MAGIC observations result in the detection of a source with significance of 6.0 standard deviations (σ). We study the multi-frequency behaviour of the source at the epoch of MAGIC observation, collecting quasi-simultaneous data at radio and optical (GASP-WEBT and F-Gamma collaborations, REM, Steward, Perkins, Liverpool, OVRO, and VLBA telescopes), X-ray (Swift satellite), and HE γ-ray frequencies. Methods. We study the VHE γ-ray emission, together with the multi-frequency light curves, 43 GHz radio maps, and spectral energy distribution (SED) of the source. The quasi-simultaneous multi-frequency SED from the millimetre radio band to VHE γ rays is modelled with a one-zone inverse Compton model. We study two different origins of the seed photons for the inverse Compton scattering, namely the infrared torus and a slow sheath surrounding the jet around the Very Long Baseline Array (VLBA) core. Results. We find that the VHE γ-ray emission detected from PKS 1510−089 in 2012 February-April agrees with the previous VHE observations of the source from 2009 March-April. We find no statistically significant variability during the MAGIC observations on daily, weekly, or monthly time scales, while the other two known VHE FSRQs (3C 279 and PKS 1222+216) have shown daily scale to sub-hour variability. The γ-ray SED combining AGILE, Fermi and MAGIC data joins smoothly and shows no hint of a break. The multi-frequency light curves suggest a common origin for the millimetre radio and HE γ-ray emission, and the HE γ-ray flaring starts when the new component is ejected from the 43 GHz VLBA core and the studied SED models fit the data well. However, the fast HE γ-ray variability requires that within the modelled large emitting region, more compact regions must exist. We suggest that these observed signatures would be most naturally explained by a turbulent plasma flowing at a relativistic speed down the jet and crossing a standing conical shock.

Radio emissions from pulsar companions: a refutable explanation for galactic transients and fast radio bursts

Abstract: Context. The six known highly dispersed fast radio bursts are attributed to extragalactic radio sources that are of unknown origin but extremely energetic. We propose here a new explanation that does not require an extreme release of energy and involves a body (planet, asteroid, white dwarf) orbiting an extragalactic pulsar. Aims. We investigate a theory of radio waves associated with such pulsar-orbiting bodies. We focus our analysis on the waves emitted from the magnetic wake of the body in the pulsar wind. After deriving their properties, we compare them with the observations of various transient radio signals to determine whether they could originate from pulsar-orbiting bodies. Methods. The analysis is based on the theory of Alfven wings: for a body immersed in a pulsar wind, a system of two stationary Alfven waves is attached to the body, provided that the wind is highly magnetised. When they are destabilised through plasma instabilities, Alfven wings can be the locus of strong radio sources that are convected with the pulsar wind. By assuming a cyclotron maser instability operating in the Alfven wings, we make predictions about the shape, frequencies, and brightness of the resulting radio emissions. Results. Because of the beaming by relativistic aberration, the signal is seen only when the companion is perfectly aligned between its parent pulsar and the observer, as is the case for occultations. For pulsar winds with a high Lorentz factor (≥10 4 ), the whole duration of the radio event does not exceed a few seconds, and it is composed of one to four peaks that last a few milliseconds each and are detectable up to distances of several Mpc. The Lorimer burst, the three isolated pulses of PSR J1928+15, and the recently detected fast radio bursts are all compatible with our model. According to it, these transient signals should repeat periodically with the companion’s orbital period. Conclusions. The search of pulsar-orbiting bodies could be an exploration theme for new- or next-generation radio telescopes.

Fingerprints of galactic loop i on the cosmic microwave background

Abstract: We investigate possible imprints of galactic foreground structures such as the "radio loops" in the derived maps of the cosmic microwave background. Surprisingly, there is evidence for these not only at radio frequencies through their synchrotron radiation, but also at microwave frequencies where emission by dust dominates. This suggests the mechanism is magnetic dipole radiation from dust grains enriched by metallic iron or ferrimagnetic molecules. This new foreground we have identified is present at high galactic latitudes, and potentially dominates over the expected B-mode polarization signal due to primordial gravitational waves from inflation.

Electrodynamics and Propagation of Radio Waves

Abstract: This workbook provides theoretical basis on the subject of “Propagation of radio waves”. The radiators and wave-guiding ducts, super high frequency units, devices and other systems have been described. Multiple case studies have been shown relating to the operating principles and characteristics of the mentioned systems. At the same time physical processes of radio waves propagated in the terrestrial atmosphere and in the vicinity of the ground surface have been reviewed in this workbook. Multiple practical data have been provided. Radio waves propagation properties in various ranges,including optical and infrared ranges, as well as terrestrial and space radio lines operational properties have been reviewed. The issue of radio waves electromagnetic coupling has been studied. Mathematical results are followed by broad descriptions in this workbook. The workbook is designated for students and graduates receiving education in the area of maintenance of radio equipment, telecommunication and technical domestic services. The workbook can be also useful for researchers, production experts and other reader audience.

Radio emissions from pulsar companions : a refutable explanation for galactic transients and fast radio bursts

Abstract: The six known highly dispersed fast radio bursts are attributed to extragalactic radio sources, of unknown origin but extremely energetic. We propose here a new explanation - not requiring an extreme release of energy - involving a body (planet, asteroid, white dwarf) orbiting an extragalactic pulsar. We investigate a theory of radio waves associated to such pulsar-orbiting bodies. We focus our analysis on the waves emitted from the magnetic wake of the body in the pulsar wind. After deriving their properties, we compare them with the observations of various transient radio signals in order to see if they could originate from pulsar-orbiting bodies. The analysis is based on the theory of Alfven wings: for a body immersed in a pulsar wind, a system of two stationary Alfven waves is attached to the body, provided that the wind is highly magnetized. When destabilized through plasma instabilities, Alfven wings can be the locus of strong radio sources convected with the pulsar wind. Assuming a cyclotron maser instability operating in the Alfven wings, we make predictions about the shape, frequencies and brightness of the resulting radio emissions. Because of the beaming by relativistic aberration, the signal is seen only when the companion is perfectly aligned between its parent pulsar and the observer, as for occultations. For pulsar winds with a high Lorentz factor, the whole duration of the radio event does not exceed a few seconds, and it is composed of one to four peaks lasting a few milliseconds each, detectable up to distances of several Mpc. The Lorimer burst, the three isolated pulses of PSR J1928+15, and the recently detected fast radio bursts are all compatible with our model. According to it, these transient signals should repeat periodically with the companion's orbital period. The search of pulsar-orbiting bodies could be an exploration theme for new- or next-generation radio telescopes.

Radio Tomography for Roadside Surveillance

Abstract: Radio tomographic imaging (RTI) has recently been proposed for tracking object location via radio waves without requiring the objects to transmit or receive radio signals. The position is extracted by inferring which voxels are obstructing a subset of radio links in a dense wireless sensor network. This paper proposes a variety of modeling and algorithmic improvements to RTI for the scenario of roadside surveillance. These include the use of a more physically motivated weight matrix, a method for mitigating negative (aphysical) data due to noisy observations, and a method for combining frames of a moving vehicle into a single image. The proposed approaches are used to show improvement in both imaging (useful for human-in-the-loop target recognition) and automatic target recognition in a measured data set.

Indoor short-range radio propagation measurements at 60 and 70 GHz

Abstract: Millimeter-wave radios operating at unlicensed 60 GHz and licensed 70 GHz bands are attractive solutions to realize short-range backhaul links for future flexible network deployment. In this work, we report directional radio channel sounding performed at 60 and 70 GHz in large indoor short-range scenarios such as offices, a shopping mall, and a railway station. Initial channel characterization is reported through propagation path detection and analyses on diffuse scattering power and delay spread. The characterization reveals that specular mechanisms represented by propagation paths dominate over diffuse scattering in the measured scenarios because of the large area size of physical environments. The results furthermore show that the delay spread does not change much between 60 and 70 GHz, suggesting that the same channel model framework can be used for modeling the radio channels at the two frequencies.

Outflow structure of the quiet sun corona probed by spacecraft radio scintillations in strong scattering

Abstract: Radio scintillation observations have been unable to probe flow speeds in the low corona where the scattering of radio waves is exceedingly strong. Here we estimate outflow speeds continuously from the vicinity of the Sun to the outer corona (heliocentric distances of 1.5-20.5 solar radii) by applying the strong scattering theory to radio scintillations for the first time, using the Akatsuki spacecraft as the radio source. Small, nonzero outflow speeds were observed over a wide latitudinal range in the quiet-Sun low corona, suggesting that the supply of plasma from closed loops to the solar wind occurs over an extended area. The existence of power-law density fluctuations down to the scale of 100 m was suggested, which is indicative of well-developed turbulence which can play a key role in heating the corona. At higher altitudes, a rapid acceleration typical of radial open fields is observed, and the temperatures derived from the speed profile show a distinct maximum in the outer corona. This study opened up a possibility of observing detailed flow structures near the Sun from a vast amount of existing interplanetary scintillation data.

Information processing apparatus, information processing method, and program

Abstract: [Solution] An information processing apparatus according to the present disclosure includes: a radio wave information learning section configured to record a plurality of pieces of radio wave information detected in a house and learn radio wave information of a plurality of terminals supposed to be in the house on a basis of the recorded radio wave information; and a control section configured to compare newly detected radio wave information and the radio wave information of the plurality of terminals supposed to be in the house based on a result of the learning, and perform processing for changing an operating state of a system that manages the house in a case where none of the plurality of terminals supposed to be in the house were detected for a prescribed time or more

Phenomena in the High-Latitude Ionospheric F Region Induced by a HF Heater Wave at Frequencies Near the Fourth Electron Gyroharmonic

Abstract: We present the results of multi-instrument studies of the phenomena in the high-latitude ionospheric F region stimulated by high-power HF O-mode radio waves injected towards the magnetic zenith when the ratio of the heater frequency to the cutoff frequency of the F2 layer is near the fourth electron gyroharmonic. Based on the stimulated electromagnetic emission (SEE), spectral observations in the kilohertz and hertz frequency bands of detunings relative to the heater wave frequency, the behaviors of different parameters of the ionospheric plasma and small-scale artificial field-aligned irregularities are compared and analyzed. The coexistence of the thermal (resonance) parametric instability (TPI) and parametric decay (striction) instability (PDI) was found in the vicinity of the fourth gyroresonance harmonic.

Accuracy vs. Resolution in Radio Tomography

Abstract: Radio tomographic imaging (RTI) has recently been proposed for tracking object location via radio waves without requiring the objects to transmit or receive radio signals. The position is extracted by inferring which voxels are obstructing the various radio links in a dense wireless sensor network. This paper derives an analytic expression for the image accuracy (error per voxel) for each of 5 published RTI system models. The formulae show the effects of weight model choice, voxel size, number of sensors, and degree of regularization on the Cramer-Rao Lower Bound (CRLB). This enables analysis of the tradeoffs between these parameters in system design, particularly between image accuracy and image resolution. The theoretical results agree well with simulations, and the new theory is used to interpret an experimental scenario.

Bluetooth radio wave zero calibration and timing system and method

Abstract: The invention provides a Bluetooth radio wave zero calibration and timing system and method. The system comprises a display portion, an MCU circuit, an electric motor and a BLE communication module, wherein the display portion is an LCD display screen or a time indicating pointer and the LCD display screen, the BLE communication module is a Bluetooth module or a BLE module, the MCU circuit is adopted as a control circuit, the time calibration structure of most traditional radio wave clocks can be removed, cost can be reduced, meanwhile, the clocks can be made to be more durable, timing and calibration can be automatically achieved for a long time at regular intervals, the daily rate can be corrected, a precise deviation rectification mechanism can be built in an internal chip of each clock, labor cost and labor intensity can be greatly reduced, and the clocks with the low cost can obtain the time precision identical to that of a clock with the high cost. The problem that the radio wave clocks cannot accurately display time under the state without the radio wave signals is solved, and meanwhile the aim that when a user reaches different countries, adjustment of different time zones can be performed is easily achieved.

Short-duration radio bursts with apparent extragalactic dispersion

Abstract: We present the results of the longest yet undertaken search for apparently extragalactic radio bursts at the Bleien Radio Observatory covering 21,000 hr (898 days). The data were searched for events of less than 50 ms FWHM duration showing a ν{sup –2} drift in the spectrogram characteristic of the delay of radio waves in plasma. We have found five cases suggesting dispersion measures between 350 and 400 cm{sup –3} pc while searching in the range of 75-2000 cm{sup –3} pc. Four of the five events occurred between 10:27 and 11:24 a.m. local civil time. The only exception occurred at night with the full Moon in the beam. It was an event that poorly fits plasma dispersion, but had the characteristics of a solar Type III burst. However, we were not able to confirm that it was a lunar reflection. All events were observed with a log-periodic dipole within 6800 hr, but none with a more directional horn antenna observing the rest of the time. These properties suggest a terrestrial origin of the 'peryton' type reported before. However, the cause of these events remains ambiguous.

Harmonic waves and sheath rectification in type III solar radio bursts

Abstract: In type III solar radio bursts and planetary foreshocks, Langmuir waves are produced by electron beams and converted partially to radio waves by linear and nonlinear processes. Lower amplitude second harmonic electric fields are observed simultaneously during the most intense Langmuir wave events in type III source regions. The electric fields at the harmonic frequencies can arise from various mechanisms, such as radio wave emission by either coalescence or antenna mechanisms, nonlinear currents, harmonics of Langmuir waves, electron trapping in Langmuir wave potentials, and Langmuir wave rectification at the sheath surrounding the spacecraft, or they can result from instrumental harmonics. In this paper the relative powers and electric field vectors of Langmuir waves and the harmonic fields are compared for multiple events. The structure of the harmonic field is shown to be determined by the Langmuir waveform, but the harmonic field direction is typically closely aligned with the solar wind flow. The magnitude, structure, and orientation of the harmonic fields is used to determine which processes are responsible. It is shown that the dominant process generating the observed harmonic fields is Langmuir wave rectification at the sheath surrounding the spacecraft. Key Points Intense Langmuir waves and harmonic fields are observed simultaneously Harmonic fields are primarily produced by sheath rectification Some evidence for nonlinear currents is found

Semiempirical Model for Ionospheric Absorption based on the NRLMSISE-00 atmospheric model

Abstract: The strength of high-frequency radio signals, when refracted by the ionosphere, can be strongly influenced by ionospheric absorption Accurate modeling of the amount of this absorption is a vital part of many studies of radio waves propagating in the ionosphere We have developed a new, flexible model of ionospheric absorption, the Semiempirical Model for Ionospheric Absorption based on the NRLMSISE-00 atmospheric model (SiMIAN) This article describes the methods and formulae used by SiMIAN, a comparison of SiMIAN with an older absorption model, and validation work performed by simulating the power returned in vertical incidence soundings of the ionosphere and comparing the results with real soundings

Vehicle to vehicle wireless communication apparatus with potential crash warning

Abstract: A wireless communication device for vehicle-to-vehicle communication includes a vehicle positioning module that uses sensors and detects a current position and a direction of the vehicle. In a map matching, pre-calculated route information and road network information based on the current position are retrieved from map data and a current link of the vehicle is identified and a potential signal pattern is determined regarding a position of next intersection and the road network information based on the current position, the direction of the vehicle and the current link. Based on the potential signal pattern, radio characteristics including a level of intensity, a frequency, and a direction are assigned. A transmitter produces a radio signal of the radio characteristics carrying the current position, the speed and the direction of the vehicle. An antenna module converts the radio signal from the transmitter into radio waves and radiates the radio waves.

First Light Detection of A Single Solar Radio Burst Type III Due To Solar Flare Event

Abstract: The eruption mechanism of solar flares and type III are currently an extremely active area of research, especially during the solar cycle is towards maximum. In this case, the total energy of solar burst type III is of the order of solar flare with the explosion of the energy can up to 10 15 ergs. The solar flare event is one of the most spectacular explosions that still be on-going study in the solar physics world. This event occurred at 2:000 UT on 15 th April 2012 is due to the explosion of the magnetic energy in from the chromosphere and converted into the heating, mass motion and particle acceleration which can be detected by solar radio burst type III. In this work, we will highlight our first light detection of very tiny solar radio burst type III, which has been observed at the National Space Centre, Banting, Selangor detected by the Compound Low Cost Low Frequency Transportable Observatories (CALLISTO) system at 5:53:23. The region of the data is from 150 − 400 MHz in radio region. This burst is drifted from 150 MHz till 260 MHz. It represents a total energy of 6.2035 × 10 -7 eV − 1.0753 × 10 -6 eV. This fast drift burst is a continuity of the acceleration of the particles which is intermittent, and can be observed since the explosion of the solar flare. Although the burst is very tiny, it is still significant because this burst is the first detection of a single type III burst from our site. Still, the acceleration of the particles can be detected from Earth in the radio region within 3 hours period of observation at the post stage of solar flare.

Short-duration Radio Bursts with Apparent Extragalactic Dispersion

Abstract: We present the results of the longest yet undertaken search for apparently extragalactic radio bursts at the Bleien Radio Observatory covering 21000 hours (898 days). The data were searched for events of less than 50 ms FWHM duration showing a $ u^{-2}$ drift in the spectrogram characteristic of the delay of radio waves in plasma. We have found five cases suggesting dispersion measures between 350 and 400 cm$^{-3}$ pc while searching in the range of 50 -- 2000 cm$^{-3}$ pc. Four of the five events occurred between 10.27 and 11.24 a.m. local civil time. The only exception occurred at night with the full moon in the beam. It was an event that poorly fits plasma dispersion, but had the characteristics of a solar type III burst. However, we were not able to confirm that it was a lunar reflection. All events were observed with a log-periodic dipole within 6800 hours but none with a more directional horn antenna observing the rest of the time. These properties suggest a terrestrial origin of the "peryton" type reported before. However, the cause of these events remains ambiguous.

Vehicle presence detection system

Abstract: A vehicle presence detection system for effectively detecting the presence of a vehicle in a location based upon a measured radio wave signal strength by a receiver. The vehicle presence detection system generally includes a main receiver adapted for receiving a radio wave signal from a transmitter and a control unit in communication with the main receiver that determines a signal strength of the radio wave signal received by the main receiver. The control unit determines that a vehicle is near the transmitter or the main receiver when the signal strength of the radio wave signal is reduced by a threshold loss.

Optimal throughput for cognitive radio with energy harvesting in fading wireless channel.

Abstract: Energy resource management is a crucial problem of a device with a finite capacity battery. In this paper, cognitive radio is considered to be a device with an energy harvester that can harvest energy from a non-RF energy resource while performing other actions of cognitive radio. Harvested energy will be stored in a finite capacity battery. At the start of the time slot of cognitive radio, the radio needs to determine if it should remain silent or carry out spectrum sensing based on the idle probability of the primary user and the remaining energy in order to maximize the throughput of the cognitive radio system. In addition, optimal sensing energy and adaptive transmission power control are also investigated in this paper to effectively utilize the limited energy of cognitive radio. Finding an optimal approach is formulated as a partially observable Markov decision process. The simulation results show that the proposed optimal decision scheme outperforms the myopic scheme in which current throughput is only considered when making a decision.

Methods of simulation of electromagnetic wave propagation in the ionosphere with allowance for the distributions of the electron concentration and the Earth’s magnetic field

Abstract: Methods of mathematical simulation of propagation of short radio waves in the Earth’s ionosphere are considered. Simulation is performed with allowance for new models of the Earth’s magnetic field, the electron concentration in the ionosphere, and experimental data obtained by means of the radio tomography method. Results of application of extended bicharacteristic system methods, the Maslov canonic operator method, and the catastrophe theory as the mathematical apparatus developed for the considered problems are described.

Radar for vehicle and method of operating the same

Abstract: Disclosed herein is a vehicle radar. The radar may include Tx antennas for a middle range, Tx antennas for a short range, Rx antenna columns for a middle range each configured to have a long shape vertically and be horizontally disposed, Rx antenna columns for a short range each configured to have a long shape vertically and be disposed between some of the Rx antenna columns for a middle range, and a control unit configured to process signals of radio waves that are reflected from a specific object after the radio waves are radiated by the Tx antennas for the middle range and that are received by the Rx antenna columns for the middle range or signals of radio waves that are reflected from a specific object after the radio waves are radiated by the Tx antennas for the short range and that are received by the Rx antenna columns for the short range.

Study on Characteristics of Human Body Shadowing in High Frequency Bands: Radio Wave Propagation Technology for Future Radio Access and Mobile Optical Networks

Abstract: To address the rapid increase in the volume of data traffic in mobile communication networks, small cells that enable data transmission at a high bit rate and use very high frequency bands (over 6 GHz) have been studied recently. Considering that the environment into which small cells are introduced is crowded and dominated by line of sight communications with very high data traffic loads, the characteristics of human body shadowing (HBS) are important propagation parameters. In this paper, we propose a method for analyzing HBS characteristics based on the uniform geometrical theory of diffraction and lossy dielectric flat plates. Calculated results are compared to measured results to show that the proposed method is effective in analyzing the HBS characteristics.

Spectral structures and their generation mechanisms for solar radio type-I burstS

Abstract: The fine spectral structures of solar radio type-I bursts were observed by the solar radio telescope AMATERAS. The spectral characteristics, such as the peak flux, duration, and bandwidth, of the individual burst elements were satisfactorily detected by the highly resolved spectral data of AMATERAS with the burst detection algorithm that is improved in this study. The peak flux of the type-I bursts followed a power-law distribution with a spectral index of 2.9-3.3, whereas their duration and bandwidth were distributed more exponentially. There were almost no correlations between the peak flux, duration, and bandwidth. That means there was no similarity in the shapes of the burst spectral structures. We defined the growth rate of a burst as the ratio between its peak flux and duration. There was a strong correlation between the growth rate and peak flux. These results suggest that the free energy of type-I bursts that is originally generated by nonthermal electrons is modulated in the subsequent stages of the generation of nonthermal electrons, such as plasma wave generation, radio wave emissions, and propagation. The variation of the timescale of the growth rate is significantly larger than that of the coronal environments. These results can be explained by the situation wherein the source region may have the inhomogeneity of an ambient plasma environment, such as the boundary of open and closed field lines, and the superposition of entire emitted bursts was observed by the spectrometer.

Array analysis of electromagnetic radiation from radio transmitters for submarine communication

Abstract: The array analyses used for seismic and infrasound research are adapted and applied here to the electromagnetic radiation from radio transmitters for submarine communication. It is found that the array analysis enables a determination of the slowness and the arrival azimuth of the wave number vectors associated with the electromagnetic radiation. The array analysis is applied to measurements of ∼20–24 kHz radio waves from transmitters for submarine communication with an array of 10 radio receivers distributed over an area of ∼1 km ×1 km. The observed slowness of the observed wave number vectors range from ∼2.7 ns/m to ∼4.1 ns/m, and the deviations between the expected arrival azimuths and the observed arrival azimuths range from ∼−9.7° to ∼14.5°. The experimental results suggest that it is possible to determine the locations of radio sources from transient luminous events above thunderclouds with an array of radio receivers toward detailed investigations of the electromagnetic radiation from sprites.