Communications: radio wave antennas – Antennas – Measuring signal energy
Patent
1998-08-27
2000-02-29
Wong, Don
Communications: radio wave antennas
Antennas
Measuring signal energy
342351, 364455, 370281, 455 121, 455427, G01S 302
Patent
active
060314982
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a process and device for measuring an antenna diagram.
STATE OF PRIOR ART
Measurement methods are necessary to characterize antennas in order to: "approximate" models; these models when there is a doubt about the physical meaning of some of the calculation results.
The purpose of the measurement equipment is to record the antenna radiation and matching characteristics: reception) as accurately as possible, by using long external bases (far field) or compact bases (plane wave recreated at short distance in an anechoic chamber); surrounding the antenna and by calculating the radiated far field; vectorial network analyzer, preferably in an anechoic chamber or in free space to prevent any coupling of the antenna with the measurement laboratory.
In a measurement base in far field like that shown in FIG. 1, the antenna to be measured 10 is placed in a direction determined with respect to a transmission antenna 11 perfectly calibrated in gain and in emitted power. The antenna to be measured, which may be protected by a radome, is connected to a device 12, for example measuring the power and the phase of the received signal. The distance D between the two antennas must be sufficient so that the waves received by the antenna to be measured are plane waves. A positioner 13 rotates the antenna 10 to be measured in different directions, for example in rotation .phi. and in sighting direction .theta.. The disadvantage of this type of measurement base is that it requires a large site, the size of which depends on the wave length. The length of this site may be several hundred meters.
In a compact base such as that shown in FIG. 2, which may be located inside a building, the waves emitted by an antenna 21 transmitting hemispheric waves are reflected by a reflector 22 that transforms the spherical waves into plane waves that are received by the antenna to be measured 23, which reduces technical effects due to distance. The disadvantage of this type of base is that uses accurate but expensive means, and furthermore which are more difficult to perfect.
In a near field base like that shown in FIG. 3, the signal power and phase in the near field emitted by a source 24 are measured, and antenna theory is applied in detail in order to obtain the characteristics of the antenna to be measured 25, using a measurement device 26. The disadvantage of this type of base is that very accurate and very precise measurement probes and sophisticated computer facilities are necessary.
In the space domain, the satellite localization
avigation sector is developing very quickly. The American G.P.S. (Global Positioning System) is an existing worldwide positioning system using a large number of satellites, that a navigator can use to determine his position and speed. The USSR has developed an equivalent system called GLONASS.
Other telecommunications satellite constellations with land mobile and/or navigation mobiles will be launched in the future, for example:
References [1] and [2] describe methods of measuring the attitude of a satellite using a GPS antenna.
Reference [3] describes how to use the signal
oise ratio for correction of errors due to multiple paths in GPS differential (or interferometric) phase measurements.
Reference [4] studies the use of GPS receivers and GPS/GLONASS receivers. This article illustrates the fact that this type of receiver is now in widespread use.
References [5] and [6] contain a technical description and characteristics of the global navigation system using the GLONASS-M satellite.
The purpose of this invention is to provide a means of making measurements of antenna diagrams, without the need for expensive measurement systems, making use of the satellites in a given constellation.
DESCRIPTION OF THE INVENTION
This invention proposes a process for measuring an antenna diagram in which:
The antenna is connected to a receiver capable of outputting measurements of the C/No ratio, which is the ratio of the useful signal power to the noise power spectral density. This
REFERENCES:
patent: 4684955 (1987-08-01), Adams, Jr. et al.
IEEE Antennas and Propagation Society Int. Symp., vol. 4, Jul. 20-24, 1992, Chicago, US, pp. 2060-2063, XP000340085, Ekelman et al.: "On-site station antenna verification".
IEE Proc. A, vol. 127, No. 7, Sep. 1980, Stevenage, pp. 417-433, XP002005327, Keen: "Satellite-antenna measurement techniques".
IEEE 1988 Int. Symp. on Electromagnetic Compatibility, Aug. 2, 1988, Seatle, US, pp. 290-294, XP000015319, Demarinis: "Quality control of antenna calibration".
Lectronics and Communications in Japan, Part I, vol. 70, No. 8, Aug. 1987, New York, US, pp. 119-126, XP000159280, Kondou: "Radiation characteristics of reflector antenna".
Centre National d'Etudes Spatiales
Clinger James
Wong Don
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