Communications: radio wave antennas – Antennas – Measuring signal energy
Reexamination Certificate
2000-05-18
2001-09-25
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Measuring signal energy
C343S786000
Reexamination Certificate
active
06295032
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
“Not Applicable”
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
“Not Applicable”
BACKGROUND OF THE INVENTION
1. Field of the Invention
This application relates to electromagnetic radiating structures suitable for use as antennas and in electromagnetic field test facilities used for observing the behaviour of equipment in the presence of strong electromagnetic fields and for detecting radiation from the equipment.
Continuous Wave (cw) measurement of electromagnetic susceptibility and radiated interference have been carried out using multiple antennas whose electromagnetic properties must be well known in the near field or using TEM cells whose volume and/or frequency limits make them unsuitable for broadband testing of large electronic sub-systems more than a few meters in height.
2. Background Information
Electromagnetic field test facilities described as “simulators” are disclosed in U.S. Pat. No. 5,440,316 issued Aug. 8, 1995 and U.S. Pat. No. 5,982,331 issued Nov. 8, 1995 both to Podgorski. The structure shown in FIGS. 1 and 2 of U.S. Pat. No. 5,982,331 is an electromagnetic field test facility employing vertically polarized electromagnetic waves in the test area and the structure shown in FIG. 3 of U.S. Pat. No. 5,982,331 is an electromagnetic field test facility employing horizontally polarized waves in the test area of a semi-anechoic chamber. The structure shown in FIGS. 9 and 10 of U.S. Pat. No. 5,982,331 is an electromagnetic field test facility employing vertically polarized electromagnetic waves in the test area and the structure shown in FIG. 12 of U.S. Pat. No. 5,982,331 is an electromagnetic field test facility employing horizontally polarized waves in the test area of an anechoic chamber.
Recently issued Bellcore's Generic Requirements Criteria GR 1089-CORE, for telecommunications equipment, indicates the need for apparatus to perform E-field (electric field) radiated immunity and emission testing from 10 kHz to 10 GHz, and H-field (magnetic field) radiated emission testing from 60 Hz to 30 MHz.
The current requirement for the standard size of testing facilities is a distance between the test antenna and the tested object of 3 m, 5 m, and 10 m with the size of testing area limited to 1.5 m×1.5 m. The broadband Gigahertz field electromagnetic field test facility of U.S. Pat. No. 5,982,331 can fulfil the standard facility size requirements with the frequency of operation from DC to 5 GHz. If the size of the testing area is limited to 0.5 m×0.5 m, the existing configuration of the broadband Gigahertz field facility allows it to exceed the upper frequency limit of 10 GHz dictated by Bellcore GR 1089-CORE.
BRIEF SUMMARY OF THE INVENTION
This application relates to broadband antennas and to broadband Gigahertz field test facility structures using the antennas to produce and to measure electromagnetic fields (E-field and H-field) in the test area. Antennas at different orientations can be used simultaneously to produce an electromagnetic field net polarization that can be controlled electrically, allowing for automated control and thereby reducing the testing time.
Low frequency of operation of a horn antenna is limited by the size of the antenna aperture (mouth of the antenna) and the upper frequency of operation is limited by the angle of the angular opening of the horn antenna. The emission and immunity testing of objects requires that not only the frequency of testing be followed, but as well in case of immunity testing, a specific power density must be attained. With a significant increase in the test frequency, there is a need for increasing the upper frequency of operation of horn antennas. With the increasing upper frequency limit of the horn antenna, the antenna beamwidth is decreased, resulting in a smaller area of illumination of the tested object. To maintain the required illumination of the tested object at higher frequencies, the following two approaches are used:
for limited size of tested objects and limited power densities, use of a single antenna with a lens if necessary. In a single antenna, if a lens is installed, the lens can either be converging (if higher power is needed) or diverging (if larger objects at low power are to be tested).
for testing of very large size objects at very high power densities, the use of antenna arrays is required. The antenna array can have individual antenna beams uniform, converging or diverging. Individual antennas can be equipped with either diverging or converging lenses or be without any lenses.
In its antenna aspect the invention relates to an antenna comprising, a horn having a septum therein adjacent one wall thereof and electrically isolated from the horn, the end of the septum outside the mouth of the horn curving towards the adjacent wall, an electromagnetic absorbing array surrounding the mouth of the horn, and resistive coupling between the forward edge of the septum and the wall of the horn adjacent to it to absorb low frequency electromagnetic energy propagated between the septum and its adjacent wall.
In an electromagnetic field test facility aspect the invention relates to an electromagnetic field test facility consisting of a semi-anechoic or anechoic chamber with inwardly facing horn antennas at opposite facing walls, the antennas being connected to conducting arrays extending forwardly into the chamber and defining a test volume therein, having the improvement comprising a pair of inwardly directed antenna arrays located at corners of the chamber to illuminate the test volume whereby high frequencies can be tested at selected polarization.
In another electromagnetic field test facility aspect the invention relates to a electromagnetic field test facility comprising a closed conducting reverberation chamber, first and second pairs of opposed arrays of conductors orthogonally arranged adjacent opposed walls of the chamber and defining a test volume therebetween, a radiating horn assembly positioned in an end wall of the assembly to establish an electromagnetic field in the test volume, and means terminating the arrays of conductors to establish a selected polarization of said electromagnetic field.
In order to perform the tests required by GR 1089-CORE, E-field radiated immunity and emission testing from 10 kHz to 10 GHz, (and if required in the future up to 100 GHz), in the standard size of testing facilities 3 m, 5 m, 10 m or larger, and for the size of testing area 1.5 m×1.5 m (or larger), the present application teaches a further modification to known broadband Gigahertz field test facility.
Although the broadband Gigahertz field test facility of U.S. Pat. Nos. 5,440,316 and 5,982,331 operates from DC, it has now been found that with suitable alteration in terminating connections the facility can also be used to perform H-field (magnetic field) radiated emission testing from 60 Hz to 30 MHz—as required by Bellcore GR 1089-CORE.
REFERENCES:
patent: 5440316 (1995-08-01), Podgorski
patent: 5982331 (1999-11-01), Podgorski
Jones Tullar & Cooper PC
Wimer Michael C.
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