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# 1989 Sixth International Conference on Antennas and Propagation, ICAP 89 (Conf. Publ. No.301)

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Displaying Results 1 - 25 of 211
• ### Radiation from small hemispherical lenses

Publication Year: 1989, Page(s):390 - 393 vol.1
| | PDF (212 KB)

The authors show that efficient radiation from the substrate side of the dipole can be achieved by using shaped lenses and matching layers. A theoretical model based on the solution to the half-space problem is presented. Approximate expressions for the electromagnetic fields on the hemispherical surface are derived and the far-field obtained by integration over that surface. Comparison is made wi... View full abstract»

• ### The effects of phased-array antennas on the performance of radars utilizing pseudo-random noise coding

Publication Year: 1989, Page(s):50 - 54 vol.1
| | PDF (376 KB)

The authors examine how the phased-array antenna affects the radar's performance when pseudo-random noise (PRN) coded waveforms are used. Issues of dispersion loss, compressed pulse shapes, and suppression of wideband sidelobes, or grating lobes are considered. Each of these three performance parameters and their interdependencies are considered for systems using PRN coded waveforms. It is shown t... View full abstract»

• ### A computer-based system for radio propagation model management

Publication Year: 1989, Page(s):387 - 391 vol.2
| | PDF (364 KB)

Describes an initial design study for an intelligent (computer-based) model management system for radio propagation prediction on Earth-space links. The system includes deep knowledge' about the relationships between the fundamental concepts used by radio propagation experts. It manages application of the models in particular regions of the world and is able to provide intelligent database suppor... View full abstract»

• ### Performance statistics of a tropospheric scatter radio link between Hong Kong and Taiwan

Publication Year: 1989, Page(s):49 - 53 vol.2
| | PDF (216 KB)

A tropospheric scatter radio link designed to meet the CCIR class 2 performance recommendations was installed in 1967 between Hong Kong and Taiwan. Since the system was commissioned in 1967, chart recorders had been used to monitor the received signal levels. The annual statistics were obtained from these monitorings and the worst month was determined. A datalogger was then installed to collect th... View full abstract»

Publication Year: 1989, Page(s):441 - 445 vol.1
| | PDF (328 KB)

Most wire antennas for tactical HF (1.6-30 MHz) applications are narrowband and therefore require some means of adjustable impedance matching (using the so-called antenna tuning unit, ATU) in order to function effectively across that bandwidth or at least a reasonable portion of it. The author presents a method of modifying the driving-point impedance of the antenna by feedpoint resistive loading ... View full abstract»

• ### Field strength forecasting with the parabolic equation: wideband applications

Publication Year: 1989, Page(s):461 - 465 vol.2
Cited by:  Papers (1)  |  Patents (1)
| | PDF (568 KB)

The desire to make field strength predictions for the more complex structures that give rise to surface and elevated ducts (such as coastal advection and subsidence inversions) has led to a renewal of interest in an alternative full-wave method of solving Maxwell's equations-the parabolic equation method. Although introduced into radiowave propagation by Leontovich and Fock (1946), it was not purs... View full abstract»

• ### Amplitude and phase scintillation at sub-auroral latitudes

Publication Year: 1989, Page(s):201 - 205 vol.2
| | PDF (320 KB)

The authors study the occurrence and behaviour of scintillations in the vicinity of the sub-auroral boundary. The experimental set-up and techniques are described, and the results discussed. Model studies are outlined View full abstract»

• ### Method for measuring impedance of monopole antennas in the range 10-100 MHz

Publication Year: 1989, Page(s):478 - 481 vol.1
| | PDF (324 KB)

A method is proposed for measuring impedances of monopole antennas and for checking the accuracy of the antenna design which does not require a large ground plane. Instead, it is proposed that the impedance measurements be performed for the antenna above a system of radial wires of relatively small length (of the order of one quarter wavelength or shorter at the lowest frequency of interest). Thes... View full abstract»

• ### Propagation modelling-past, present and future

Publication Year: 1989, Page(s):263 - 267 vol.2
| | PDF (356 KB)

Propagation models are used to represent the wealth of information available about a propagation phenomena. Models are developed from physical analyses and statistical analyses of experimental observations. The modeling process is iterative. As one's understanding of a particular phenomenon improves, so do the models used to describe that phenomenon. Several models that describe propagation throug... View full abstract»

• ### Sodar echograms and correlation with microwave propagation characteristics in a hilly terrain

Publication Year: 1989, Page(s):234 - 238 vol.2
Cited by:  Papers (1)
| | PDF (436 KB)

An attempt has been made to correlate sodar structures with line-of-sight microwave propagation characteristics. A vertically pointing monostatic sodar system was set up at SV University, Tirupati, India, in order to study the thermal structure of the lower atmosphere to a height range of 1 km. The principle of monostatic acoustic sounding systems is straight forward: a burst of sound wave is proj... View full abstract»

• ### Gaussian beamwaist and radiation pattern measurements of a quasi-optical radiometer

Publication Year: 1989, Page(s):383 - 389 vol.1
Cited by:  Papers (2)
| | PDF (412 KB)

The authors present Gaussian beamwaist and radiation pattern measurements of the breadboard high frequency subsystem (HFSS) of the advanced microwave sounding unit-B (AMSU-B) instrument. The AMSU is a 20 channel microwave radiometer providing temperature and humidity soundings. Channels 16 to 20 which cover the frequency range from 86 GHz to 192 GHz form the basis of AMSU-B which is being provided... View full abstract»

• ### Satellite antenna subsystem using shaped reflector and multiple feed gridded reflectors

Publication Year: 1989, Page(s):60 - 64 vol.1
Cited by:  Papers (2)
| | PDF (272 KB)

Satellite antennas are usually required to provide radiation patterns which match an irregularly shaped coverage zone. The two main techniques for achieving this shaping are multiple feeds or shaped reflectors. The authors discuss a proposed 12/14 GHz subsystem design which makes appropriate use of both a dual shaped reflector and a dual gridded reflector system. The application of the two technol... View full abstract»

• ### Tropospheric communication in arid zone with space diversity

Publication Year: 1989, Page(s):46 - 48 vol.2
| | PDF (100 KB)

Describes the results of a series of experiments conducted on a 158 Km path between IIT Delhi and CEERI Pilani. Most of the path towards the Pilani side is almost desert while it is rocky and inhabited towards the Delhi end and can be broadly classified as a mix desert and continental subtropical climate path. The system operates in 4.4 GHz to 5 GHz band, and has the capability of two way communic... View full abstract»

• ### Low profile antennas and arrays for satellite navigation

Publication Year: 1989, Page(s):131 - 134 vol.1
| | PDF (240 KB)

The Global Positioning System (GPS or Navstar) is a highly accurate navigational aid, which relies on receiving circularly polarised signals at 1575 MHz (L1) 1227 MHz (L2) from a number of satellites scattered across the upper hemisphere. The signal bandwidth is 20 MHz at both L1 and L2, with a relatively flat pass band response, so that the 3 dB bandwidth of the antenna is significantly greater t... View full abstract»

• ### The wideband feed system on the Australia Telescope

Publication Year: 1989, Page(s):163 - 167 vol.1
| | PDF (396 KB)

From the outset the Australia Telescope has been designed to permit operation over a very wide frequency range covering frequency bands within the range 1.25-116 GHz. The lower end of this range is determined by the requirement to observe red shifted hydrogen which has a line at 1.42 GHz while the upper limit is to encompass the carbon monoxide line at 115.3 GHz. Extending the operation of the tel... View full abstract»

• ### Temperature dependence of molecular absorption in the atmospheric transparency window at 340 GHz

Publication Year: 1989, Page(s):439 - 440 vol.2
| | PDF (136 KB)

Recent laboratory measurements made by Furashov and Katkov (1985) confirmed that the nonlinearity of air humidity dependence of the atmospheric water vapour absorption coefficient in the transparency windows centred at 340 and 410 GHz exceeds essentially the theoretical one which is associated with the self-broadening of H2O monomer spectral lines. Data testifying to a stronger dependen... View full abstract»

• ### Boundary-condition-transfer method for two-dimensional resonant scattering by lossy dielectric cylinders of arbitrary cross-section

Publication Year: 1989, Page(s):458 - 462 vol.1
| | PDF (236 KB)

The scatterers are taken as infinitely long lossy dielectric cylinders of arbitrary cross-section. The excitation is either a TM polarized (Ez is the only electric field component) or a TE polarized (Hz is the only magnetic field component) plane wave or a line-source. A plane wave incident obliquely on the cylinder can be decomposed into its TM and TE polarized components. T... View full abstract»

• ### Loop and spiral line antennas at microstrip substrate surface

Publication Year: 1989, Page(s):196 - 200 vol.1
Cited by:  Papers (3)  |  Patents (1)
| | PDF (280 KB)

Radiation elements printed on a dielectric material have not been fully addressed due to difficulties in determining the current distributions on the radiation elements. The authors describe some new aspects of the radiation characteristics of a loop antenna. Special attention is paid to generation of a circularly polarised wave with a single voltage source. The numerical results show that a loop ... View full abstract»

• ### Atmospheric radio noise measurements in India

Publication Year: 1989, Page(s):36 - 39 vol.2
| | PDF (280 KB)

Atmospheric radio noise (ARN) also called static is caused by the naturally occurring intercloud electrical discharge in thunderstorms accompanying electric flashes in the Earth's atmosphere. They are spread over a wide range of radio spectrum and their intensity bears an inverse ratio to the frequency. Their effects are significant up to 30 MHz which includes the broadcasting bands. In any radioc... View full abstract»

• ### The satellite: an ideal test range for accurate Earth station antenna measurements'

Publication Year: 1989, Page(s):473 - 477 vol.1
Cited by:  Papers (1)
| | PDF (440 KB)

EUTELSAT, the European Telecommunication Satellite Organization, whose mission is to provide and operate telecommunication satellites currently has four satellites in orbit. There exists a wide range of techniques for antenna measurements for satellite telecommunications, but the author first very briefly demonstrates the domain of antenna measurements by converging the experimental capabilities o... View full abstract»

• ### Investigation of a variable peripheral cavity feed for front-fed reflector antennas

Publication Year: 1989, Page(s):263 - 267 vol.1
Cited by:  Papers (1)
| | PDF (300 KB)

Presents experimental results obtained for a variable peripheral cavity waveguide feed during the investigation of small reflector antenna configurations suitable for sequential lobing and continuous beam steering tracking operation. The presented results, detailing primary and secondary, copolar, cross-polar and phase characteristics, extends the work previously published and highlights the opera... View full abstract»

• ### Optimised aperture distribution for satellite antennas with maximum edge gain

Publication Year: 1989, Page(s):122 - 125 vol.1
| | PDF (348 KB)

The optimum shape of the pattern of a satellite antenna depends on the objective of the satellite and on restrictions derived from international agreements, launcher limitations and cost budget. Frequently high-performance reflector antennas are required which exhibit the capability of almost homogeneous illumination of the coverage area, low spillover in neighbouring areas, small dimensions, low ... View full abstract»

• ### Rain attenuation of millimeter waves observed simultaneously by radiometer and bistatic radar

Publication Year: 1989, Page(s):234 - 237 vol.1
| | PDF (192 KB)

Millimeter wave propagation depends mainly on the meteorological parameters like temperature, pressure, humidity and rain rate. The major difficulty in such measurements is that a sufficiently large number of sensors are needed for a reliable estimate of such effects. The results for a long path can show up only the integrated effect of attenuation but cannot reveal the finer structure of the atte... View full abstract»

• ### Diversity gain and rain height statistics for slant paths from radar measurements

Publication Year: 1989, Page(s):340 - 344 vol.2
Cited by:  Papers (1)
| | PDF (268 KB)

A dual polarized S-band radar was used in a year long experiment to study the prediction of slant path attenuation from radar data. As a part of this experiment, a large number of RHIs (vertical radar scans) were made during rain events. The data from these events has been analyzed to determine the statistics of rain height and melting layer thickness. Diversity gain statistics can be obtained fro... View full abstract»

• ### Software tools for the planning of VHF, UHF and microwave systems

Publication Year: 1989, Page(s):382 - 386 vol.2
Cited by:  Papers (1)
| | PDF (320 KB)

Propagation software tools are an essential part of the planning capability of the GEC-Marconi Research Centre. Several tools have been developed driven by demand for computer assistance with major planning activities. These tools are used for planning area coverage systems and fixed links in the VHF, UHF and microwave bands. All the tools calculate either interactively or in batch mode on a minic... View full abstract»