 Magnetic recording medium |
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| Rotary magnetic head assembly |
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| Apparatus for electrically converting an analog signal into a digital representation |
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| Capacitive DAC to filter interface circuit |
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| Fail-safe alarm circuit |
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| Signal converter |
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| Surface-mounted single package data acquistition system |
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| Double integration, delta-sigma, analog-digital coder |
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| Radar altimeter |
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Antenna matching device
| Details |
Inventors: Hodgkinson, Alec J.;
Assignee: Z.S. Electroniques (Proprietary) Limited (ZA)
Primary Examiner:
Assistant Examiner:
Attorney, Agent or Firm:
An antenna matching device has a ferromagnetic core with a balanced shape and composition to each side of a center tap position. Each side of the core has a first and second parallel wound coil, the free end leads of the first coils being connected together, and the center-tap lead of each first coil being connected to that of the corresponding second coil on the opposite side of the core, the free end lead of each second coil being connected to its own antenna terminal. |
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DETAILED DESCRIPTION OF THE DRAWING Referring to FIG.
1, two antenna leads 1 are illustrated, each being approximately seven meters long and having a cylindrical tube 2 with a central conductor 3 with the space 4 between the central conductor and the inner walls of the tube being filled with a dielectric material.
This antenna is normally used in a whip antenna configuration, and is more particularly described in, and forms the subject matter of, applicant's South African Patent Application number 79/6143 entitled "Dielectric Antenna", filed on the Oct.
9, 1980 and claiming a priority date of Nov.
15, 1979.
The difficulty with this and other whip antennas, is that when placed in a horizontal position they are unbalanced as a result of the stray capacitance between the antenna and ground.
The application of this invention, as will be described, enables the use of such an antenna in a horizontal position.
An elongated ferrite core 5 is of a balanced shape and composition to each side of a centre-tap position 6 in the middle thereof.
Each side of the core 5 has a first and second parallel wound coil, numbered 7 and 8 respectively, and the coils on each side are wound in the same direction from the centre-tap position.
Each coil has a centre-tap lead 9 and a free end lead 10 at its end of the coil.
The free end leads 10 of first coils 7 are connected directly together by a line shown as 11, and the centre-tap lead 9 of each first coil 7 is connected to that of the second coil 8 on the opposite side of the core respective to form radio unit feed terminals 12 at the connection points.
One of these terminals 12 is connected to the signal line 13 of a co-axial cable 14, and the other terminal 12 is connected to the earth braid 15 of the co-axial cable 14.
The co-axial cable is taken as feed to the radio unit (not shown).
This other terminal 12 is also directly connected to an earth 16.
The free end lead 10 of each second coil 8 is connected to a separate antenna terminal 17.
Each antenna 1 at its remote end has its central wire connected to the cylindrical wall, as shown by numeral 18, and the opposite rear end of each antenna 1 has its cylindrical wall connected to a different one of the antenna terminals 17
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Radio 
