Communications: radio wave antennas – Antennas – High frequency type loops
Patent
1996-09-17
1998-11-17
Le, Hoanganh
Communications: radio wave antennas
Antennas
High frequency type loops
343866, 343742, H01Q 1112
Patent
active
058382836
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates generally to a loop antenna for radiating a circularly polarized wave, particularly to a loop antenna that is suitable for use in a terminal device for a communication system of a circularly polarized wave mode.
BACKGROUND ART
A loop antenna for circularly polarized waves having a thin and low construction is suitable as an antenna for being mounted on mobile facilities such as automobiles and aircraft, since projections made by the antenna being mounted cannot apparently be seen. There have been various proposals for such a circularly polarized antenna. One example is a "loop antenna having passive element, B-104" which was announced by Mr. Hisamatsu Nakano and three others, in the spring national conference of the Japan Electronic Information Communication Institute of 1994 and recorded in page 2-104. The abovementioned loop antenna for radiating a circularly polarized wave is shown in FIG. 5 through FIG. 7. FIG. 6 illustrates a C1-type loop antenna for circularly polarized wave as a first example, and FIG. 7 illustrates a C2-type loop antenna for circularly polarized wave as a second example.
FIG. 5 is a front elevation view of the circularly polarized wave antenna, and FIG. 6 is a top view of the C1-type loop antenna for circularly polarized wave.
The C1-type loop antenna for radiating a circularly polarized wave has a coaxial feeder loop element 100 placed in parallel to a ground plane 105, and a passive loop element 101 having a larger diameter than the coaxial feeder loop element 100 is placed above and in parallel to the coaxial feeder loop element 100 maintaining a concentric configuration thereto. The space between the ground plane 105 and the coaxial feeder loop element 100 is specified as H.sub.1, and the space between the ground plane 105 and the passive element 101 is specified as Hp.
In the circularly polarized loop antenna thus constructed, the coaxial feeder loop element 100 is fed such that one end of an I-shape conductor 104 is, as shown in FIG. 6, connected to the coaxial feeder loop element 100 and the other end of the I-shape conductor is connected to a feeder conductor 106. The feeder conductor 106 is connected to a central conductor of a coaxial line 102, as shown in FIG. 5.
The passive loop element 101 is provided with a cutoff part 103; an angle formed by the cutoff part 103 and the I-shape conductor 104, and a length of the cutoff part 103 are specified as .PHI.p, and .increment.g, respectively.
In this case, provided that the angle .PHI.p is specified to be close to +45.degree. or -135.degree., a left-handed circularly polarized wave will be radiated by the action of the cutoff part 103; provided that the angle .PHI.p is specified to be close to -45.degree. or +135.degree. a right-handed circularly polarized wave will be radiated by the action of the cutoff part 103. Thereat, a current of a virtually progressive wave flows in the coaxial feeder loop element 100 and the passive loop element 101. When the circumferential length of the coaxial feeder loop element 100, C1=1.lambda., the circumferential length of the passive loop element 101, C2=1.25.lambda., H.sub.1 =0.0667.lambda., Hp=0.0792.lambda., .increment.g=0.0104.lambda., .PHI.p=.+-.42.degree. or 139.degree. are given, wherein .lambda. is the natural space wavelength, the gain vs. frequency characteristics of the C1-type loop antenna for circularly polarized wave is shown as b in FIG. 3, and the circularly polarized wave axial ratio vs. frequency characteristics is shown as b in FIG. 4.
FIG. 7 is a top view of the C2-type loop antenna for radiating a circularly polarized wave. The C2-type loop antenna for circularly polarized wave has the coaxial feeder loop element 100 placed in parallel to the ground plane 105, and the passive loop element 101 having a larger diameter than the coaxial feeder loop element 100 is placed above and in parallel to the coaxial feeder loop element 100 maintaining a concentric configuration thereto. The space between the ground plane 105 and the co
REFERENCES:
patent: 2116734 (1938-05-01), Reinartz
patent: 2405123 (1946-08-01), Fyler
patent: 2785396 (1957-03-01), Carter
patent: 3833908 (1974-09-01), Loh
patent: 5371509 (1994-12-01), Wallace, Jr. et al.
Le Hoang-anh
Nippon Antenna Kabushiki Kaishya
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