Communications: radio wave antennas – Antennas – Wave guide type
Patent
1994-01-27
1995-08-08
Wimer, Michael C.
Communications: radio wave antennas
Antennas
Wave guide type
343703, H01Q 1302, G01R 2908
Patent
active
054403162
DESCRIPTION:
BRIEF SUMMARY
This application relates to electromagnetic radiating structures suitable for use as antennas or as electromagnetic simulators. An electromagnetic simulator is a type of test equipment used for checking the behaviour of equipment in the presence of strong electromagnetic fields.
Continuous Wave (cw) measurement of electromagnetic susceptibility and radiated interference can be 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 (few meters in height) electronic sub-systems.
Pulse measurements of electromagnetic susceptibility are currently conducted using parallel line simulators, G-TEM cells or distributed load conical simulators. The parallel line simulators suffer from high frequency limitations. The use of G-TEM cells limits the volume of the tested object and the conical simulator suffers from frequency limitations.
U.S. Pat. No. 4,546,358 issued Oct. 8, 1985 to Edlin et al. discloses a test cell formed in the space between a parallel plate conductor and ground plane which together form a transmission line. The parallel plate conductor is fed by a tapered line section from a coaxial feed, in order to maintain a constant impedance, and the parallel plate conductor terminates in a fluted edge to avoid reflections.
Canadian Patent No. 1,273,060, issued Aug. 21, 1990 to BBC Brown, Boveri & Company, Limited, (U.S. Pat. No. 4,837,581) discloses an EMI testing device using a wave guide of pyramidal shape but with added features. The test device disclosed in this patent has an intermediate plate conductor suspended in the wave guide at a distance of about one quarter of the total height of the wave guide from the top surface. This defines a test volume between the intermediate plate and the wave guide lower surface. Uniform field strength in the test volume is achieved by a complex termination arrangement consisting of a curved wall of high frequency energy absorbing material coupled to the intermediate plate by a number of terminal resistors. The impedance of the line formed by the intermediate plate and the ground plane can be slightly varied, if required for fine tuning, by altering the spacing of the intermediate plate from the upper surface of the wave guide.
Such equipment is unsuitable for the testing of large pieces of electronic equipment. The apparatus described in the present application can be expanded to accommodate larger objects without degradation of the bandwidth.
Generally, the simulator described in this application launches an electromagnetic wave from a high frequency coaxial feed line into an expanding rectangular horn containing a plate conductor forming an asymmetrical parallel line within the horn. The parallel line extends beyond the horn by means of a forwardly extending conducting plate section which functions as a radiating element and establishes a test volume in the space between itself and a ground plane extending forwardly from the lower surface of the horn. The forwardly extending plate section is connected to the parallel line either directly or through a network of parallel inductance and capacitance. Two modes of propagation occur in the horn giving a complete coverage of the relevant frequency spectrum.
Specifically, in one aspect the invention relates to a broadband electromagnetic field simulator comprising: an open horn waveguide and a ground plane conductor formed as a forward extension of the lower surface of the horn. A source of r.f. energy is coupled to the apex of the horn and a relatively narrow conducting plate positioned to form a septum between the upper and lower surfaces of the horn. A plate section of similar configuration to the septum is coupled thereto and extends forwardly from the mouth of the horn. The plate section extends initially substantially parallel to the ground plane and then curves downwardly to terminate adjacent to it. The space between the forwardly extending plate section and t
REFERENCES:
patent: 3938159 (1976-02-01), Ajioka et al.
patent: 4119951 (1978-10-01), Garon et al.
patent: 4157549 (1979-06-01), Davis
patent: 4546358 (1985-10-01), Edlin et al.
patent: 4605916 (1986-08-01), Tehori
patent: 4905013 (1990-02-01), Reindel
Gibson Gary A.
Podgorski Andrew S.
Podgorski Andrew
Wimer Michael C.
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