Radio Wave Transmission Research Articles

Radio wave back‐propagating in polar coordinates: A linear filter in the time‐frequency angle‐frequency domain

The Comet Nucleus Sounding Experiment by Radio Wave Transmission (CONSERT) is a tomography of a comet nucleus for the ROSETTA mission, which consists of the transmission of electromagnetic waves between a lander on the comet nucleus surface and an orbiter through the nucleus to study its internal structure. The data inversion requires back‐propagating the electric field from the orbit to the nucleus surface. In order to take into account the circular geometry of the boundary conditions, we propose a back‐propagation in the angle‐frequency time‐frequency domain. This new method is described in this paper. We analyze similarities and differences with classical methods in Cartesian coordinates in terms of dispersion equations and evanescent waves; and we used this study to stabilize our back‐propagating filter. This method is then tested on CONSERT synthetic data.

A two dimensional simulation of the CONSERT experiment (radio tomography of comet Wirtanen)

We simulate two-dimensional (2-D) maps of the internal permittivity of comet Wirtanen from CONSERT (Comet Nucleus Sounding Experiment by Radiowave Transmission) phase measurements. We study the influence of a priori covariance matrices on the mapping process through Tikhonov or linear regression inverse formulas. We show that this a priori information permits a smooth imaging of the internal permittivity, sometimes affected by ghosts (false anomalies). Accounting for indirect propagation paths through the comet material (rays totally reflected by the comet surface) can alleviate this problem.

Transmission of UHF radiowaves through buildings in urban microcell environments

Results are presented of high-resolution time delay and angle-of-arrival measurements behind a large building in an urban microcell. It is demonstrated that in this particular case the electromagnetic field is dominated by contributions resulting from transmission through the building. The associated loss over free-space loss is < 30 dB. This makes clear the importance of modelling propagation through buildings surrounding the base station in the planning stage of urban microcells.

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

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

The ancient and modern history of EM ground-wave propagation

Radio-wave transmission over the surface of the Earth is a subject of enquiry going back to the beginning of the century. In this review, an attempt is made to describe the ground-wave mechanism that is omni-present. We first call attention to the early analytical contributions of Zenneck and Sommerfeld, based on a flat-Earth model. The subsequent controversies, particularly with regard to the role of the Zenneck surface wave, are outlined. Further developments by other pioneers, such as van der Pol, Fock, Bremmer, Norton, and Millington, are reviewed, and an attempt is made to put these in a modern context. We also show that the trapped surface wave can be a significant contribution to the total ground-wave field, when the Earth boundary is sufficiently inductive. Mixed-path theory and confirming model tests by Ray King are described briefly, along with calculated propagation curves for twoand three-section paths. The bibliography includes references to related topics, such as tropospheric refraction and topographic influences.

Comet nucleus sounding experiment by radiowave transmission

We describe the radio science experiment proposed for the Rosetta cometary mission. The experiment consists in the transmission of electromagnetic waves between the landers and the orbiter through the comet to study its internal structure. In the paper, the electromagnetic model of the comet is presented and used to evaluate the potentiality of the experiment. Various modellings of the radio wave propagation are discussed. Finally, a description of the experiment and the instrument is made.

建物によるテレビ電波反射障害防止用電波透過型カーテンウォール

建物によるテレビ電波反射障害防止用電波透過型カーテンウォール

Solar control coatings containing a sputter deposited SiWO x film

A two-layer SiWO x /Al 2O 3 film was deposited on a quartz glass substrate by rf reactive sputtering using Si 10W 90 and Al targets for use as a solar control glazing. The resistivity of the SiWO x film is 2.26 Ω·cm, indicating that it allows transmission of radio waves. This film shows wide absorption bands in the 500–1600 nm region and high transmittance in the 300–500 nm region, and its solar energy and visible transmittances are 50% and 58%, respectively. This film also exhibits good thermal stability. The two-layer film can be used as an effective solar control glazing that allows the transmission of radio waves and is thermally stable.

Spectral characteristic of the coherent millimeter-wave radar echoes from humans in motion

Results of an experimental investigation of coherent 2-mm wave band signals reflected from a moving human are considered. It is shown that the reflected spectrum is characterized by two maxima located in the vicinity of zero and the mean Doppler frequency. Data are presented on radio wave transmission and reflection factors for some kinds of clothes, as well as statistical characteristics of the reflected spectrum for different directions and magnitudes of the target velocity.

テレビジョン年報 無線・光伝送

テレビジョン年報 無線・光伝送

Radar Investigation of Mars, Mercury, and Titan

Radar astronomy is the study of the surfaces and near surfaces of Solar System objects using active transmission of modulated radio waves and the detection of the reflected energy. The scientific goals of such experiments are surprisingly broad and include the study of surface slopes, fault lines, craters, mountain ranges, and other morphological structures. Electrical reflectivities contain information about surface densities and, to some extent, the chemical composition of the surface layers. Radar probes the subsurface layers to depths of the order of 10 wavelengths, providing geological mapping and determinations of the object’s spin state. Radar also allows one to study an object’s atmosphere and ionic layers as well as those of the interplanetary medium. Precise measurements of the time delay to surface elements provide topographic and powerful information on planetary motions and tests of gravitational theories such as general relativity. In this paper, we limit our discussion to surface and near-surface probing of Mercury, Mars, and Titan and review the work of the past decade, which includes fundamentally new techniques for Earth-based imaging. The most primitive experiments involve just the measurement of the total echo power from the object. The most sophisticated experiments would produce spatially resolved of the reflected power in all four Stokes’ parameters. Historically, the first experiments produced echoes from the Moon during the period shortly after World War II (see e.g. Evans 1962), but the subject did not really develop until the early 1960s when the radio equipment was sufficiently sensitive to detect echoes from Venus and obtain the first Doppler strip maps of that planet. The first successful planetary radar systems were the Continuous Wave (CW) radar at the Goldstone facility of the Caltech’s Jet Propulsion Laboratory and the pulse radar at the MIT Lincoln Laboratory. All of the terrestrial planets were successfully studied during the following decade, yielding the spin states of Venus and Mercury, a precise value of the astronomical unit, and a host of totally new discoveries concerning the surfaces of the terrestrial planets and the Moon. This work opened up at least a similar number of new questions. Although the early work was done at resolution scales on the order of the planetary radii, very rapid increases in system sensitivities improved the resolution to the order of 100 km, but always with map ambiguities. Recently, unambiguous resolution of 100 m over nearly the entire surface of Venus has been achieved from the Magellan spacecraft using a side-looking, synthetic aperture radar. Reviews of the work up to the Magellan era can be found in Evans (1962), Muhleman et al (1965), Evans & Hagfors (1968, see chapters written by G Pettengill, T Hagfors, and J Evans), and Ostro (1993). The radar study of Venus from the Magellan spacecraft was a tour de force and is well described in special issues of Science (volume 252, April 12, 1991) and in the Journal of Geophysical Research (volume 97, August 25 and October 25, 1992). Venus will not be considered in this paper even though important polarization work on that planet continues at Arecibo, Goldstone, and the Very Large Array (VLA). In this paper we review the most recent work in Earth-based radar astronomy using new techniques of Earth rotation, super synthesis at the VLA in New Mexico (operated by the National Radio Astronomy Observatory), and the recently developed techniques at the Arecibo Observatory in Puerto Rico (operated by Cornell University). [Note: It was recently brought to our attention that the VLA software doubles the flux density of their primary calibrators. Consequently, it is necessary to half the radar power and reflectivity numerical values in all of our published radar results from the VLA/Goldstone radar.] The symbiotic relationship in these new developments for recent advances in our understanding of Mercury and Mars is remarkable. VLA imaging provides for the first time, unambiguous images of an entire hemisphere of a planet and the long-code technique makes it possible to map Mars and Mercury using the traditional range-gated Doppler strip mapping procedure [which was, apparently, developed theoretically at the Lincoln Laboratory by Paul Green, based on a citation in Evans (1962)]. Richard Goldstein was the first to obtain range-gated planetary of Venus as reported in Carpenter & Goldstein (1963). Such a system was developed earlier for the Moon as reported by Pettengill (1960) and Pettengill & Henry (1962). We first discuss the synthesis mapping technique.

Effect of segmentation of conductive coatings on the radio wave transmission through solar control sheet glass

It is a well known phenomenon that the amplitude of radio waves propagating through solar control glass is greatly reduced, because the electrical conductive film on the surface of solar control glass reflects the incident radio waves with frequencies lower than that of the plasma oscillation of free electrons in the conductive film. As a result of the moment method analysis of the scattering problem in the spectral domain, it was found that the amplitude of radio waves was not damped when the conductive film was divided into discontinuous segments with a periodic array because the motion of free electrons induced by the magnetic field of incident radio waves is restricted in the divided film. The effect of dividing the conductive film of solar control glass has been examined experimentally in the television wave region.

特集 テレビジョン年報 無線・光伝送

特集 テレビジョン年報 無線・光伝送

特集 テレビジョン年報 ８． 無線・光伝送

特集 テレビジョン年報 ８． 無線・光伝送

Excitation of artificial airglow by high power radio waves from the “SURA” Ionospheric Heating Facility

The SURA facility for generation of high power radio waves, located near the village of Vasil'sursk USSR, operates between 4.5 and 9.0 MHz and has a maximum effective radiated power (ERP) of 300 MW. Nonlinear interactions between the HF radio waves and F‐layer plasma occur near the electromagnetic wave reflection point. Energetic electrons are accelerated out of the interaction regions by the electrostatic waves. Ambient oxygen atoms collisionally excited by these suprathermal electrons yield enhanced airglow. Low‐light‐level, optical measurements were made at SURA during September 1990. Images of enhanced red‐line (630 nm) emissions were recorded during radio wave transmissions at 4.786, 5.455, and 5.828 MHz. The antenna radiation pattern, ionospheric irregularities, and the magnetic field orientation affected the shape of the observed airglow structures. The airglow clouds drifted across the night sky, disappeared, and reformed at the zenith of the antenna array. This has been interpreted in terms of radio beam refraction in drifting plasma irregularities and bifurcation when the beam is split between two density cavities. Subject to clear skies, our experience indicates that the low‐light‐level‐imaging technique is a reliable method to study large scale irregularities and electron acceleration with high‐power HF transmitting facilities.

The scope of impedance boundary conditions in radio propagation

The surface impedance boundary condition is a useful concept when dealing with the analysis of radio wave transmission over inhomogeneous surfaces. The justification for the method is not rigorous but confidence is gained by examining a number of canonical problems where exact solutions are obtainable. The scope of the surface impedance postulate is reviewed, and its relevance in radiowave propagation and related applications, such as magnetotelluric probing of the subsurface, is indicated.

Field test measurement for 128 kbit/s QPSK signal transmission and delay time spread in 1.5 GHz-band land mobile radio

High-speed digital signal transmission is a promising new field of communication services. In land mobile radio communication, transmission quality severely suffers from frequency selective fading under multipath radio wave transmission environments. Field test measurement results for 128 kbit/s QPSK signal transmission and delay time spread in the Tokyo metropolitan area are presented. The two-branch diversity reception method was adopted to combat fading. Bit error rate (BER) performance is obtained as a function of delay time spread.

High‐sensitivity stethoscopic system and method

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Studying the effects of solar flares by slant probing of the ionosphere

satisfactory coincidence between the theoretical and experimental relationships between changes in field strength and range. The authors would like to thank V. B. Belyanskii for his useful discussions of the ques- tion pertaining to antenna directivity patterns in the experiment [2]; furthermore, we express our gratitude to M. Ichinose, the author of [i], for providing us with much additional ma- terial relating to [i], and also to T. A. Ivanov, V. V. Radul, and G. M. Smirnov, for their assistance in preparing this paper. i. 2. 3. 4. 5. 6. 7. LITERATURE CITED M. Ichinose, Y. Kuratani, and I. Y. Yamazaki, J. Radio Res. Lab., 32, No. 136, 61 (1985). I. A. Tushentsova, D. I. Fishchuk, and E. E. Tsedilina, Preprint IZMIRAN, No. 12(701), Moscow (1987). M. No Fatkullin et al., Empirical Models of the Middle-Latitude Ionosphere [in Russian], Nauka, Moscow (1981). N. I. Manaenkova and E. E. Tsedilina, Izv. Vyssh. Uchebn. Zaved., Radiofiz., 25, No. 5, 508 (1982). Monthly Forecast of Maximum Utilized Frequencies (MUF); November 1981, December 1981 [in Russian], Gidrometeoizdat, Moscow (1981). V. Ya. Vovk, Author's Abstract of Candidate's Dissertation, IZMIRAN, Moscow (1985). I. Kuriki, I. Kasuya, H. Hojo, and K. Tanohata, J. Radio Res. Lab., 21, No. 105, 161 (1974). STUDYING THE EFFECTS OF SOLAR FLARES BY SLANT PROBING OF THE IONOSPHERE N. F. Blagoveshchenskaya, V. A. Bubnov, and V. T. Ustinovich UDC 550.388.2 We examine the results obtained in a study of the effects of solar flares by means of a method of slant probing of the ionosphere (SPI) along a subauroral path some 9.0 thousand km long throughout 1981-1982. The SPI data are com- pared against results obtained in recording sudden ionospheric disturbances of the SWF, SPA, SEA, and SFD types, as well as against the parameters of the solar radio emissions in the 650-15,000 MHz waveband. The increase in the intensity of x-ray and ultraviolet emissions during solar flares leads to an elevated concentration of electrons in the ionosphere. The immediate effects of solar flares on the ionosphere (sudden ionospheric disturbances) are recorded in a variety of ways that yield information as to changes in the state of the ionosphere at various alti- tude levels. We know [i] that solar flares produce minimal increases in the pulse reflection frequen- cy fmin, as well as a change in the critical frequencies of the E and F2 layers when the ionosphere is probed vertically. Measurements of fmin over more frequent probing periods can be used both to monitor absorption as well as for quantitative estimates. Nevertheless, because of the smallness of Afmin, the use of fmin as an absorption indicator is limited. From this point of view, of considerably greater potential is the method of slant probing of the ionosphere (SPI). When radio waves are emitted obliquely, the trajectories in the ionosphere are considerably longer than in the case of vertical emissions. Consequently, the direct effects of solar flares in the case of slant probing must become more clearly defined. In this case, the amplitudes of the disturbances, estimated in terms of the maxi- mum deviation of the lowest observed frequencies (LOF) from the undisturbed level along the radio-wave transmission path covered by a slant probing system, will be significantly greater than in the case of vertical probing emissions. Moreover, observations along the radio trans- Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. i, pp. 17-21, January, 1989. Original article submitted April 14, 1987; revision submitted September 8, 1987. 0033-8443/89/3201-0013512.50 9 1989 Plenum Publishing Corporation 13

Telemetry in Power Systems

Modern power systems have gradually grown from small isolated systems to vast interconnected grids. Several benefits result from those large interconnected grids and a price that has to be paid for those benefits is investment in telemetry systems and digital computers or micro-computers.In this paper we shall concern ourselves with data acquisition and telemetry for power system applications such as those for load despatch centres.The communication media, i.e., PLCC, microwave transmission or radiowave transmission are mentioned in passing. More stress, however, is put on the transmission format and protocol, making the treatment contemporary with regard to the proliferation of micro-computers.