Communications: radio wave antennas – Antennas – High frequency type loops
Patent
1986-10-03
1988-11-15
Sikes, William L.
Communications: radio wave antennas
Antennas
High frequency type loops
343743, 343842, 343866, H01Q 700
Patent
active
047853034
DESCRIPTION:
BRIEF SUMMARY
This invention concerns improvements in and relating to aerials, and more especially to aerials for radio and television reception in the VHF and UHF frequency band.
Conventional dipole aerials used for the reception of radio and television in the VHF and UHF frequency band have directional characteristics such that for optimum gain they must be aligned in a predetermined position relatively to the transmitter. Such aerials therefore have significant disadvantages when used on mobile vehicles, since, with the aerial in the fixed position on the vehicle, the strength of any signal received will vary in accordance with the direction in which the vehicle is moving and the corresponding alignment of the aerial relatively to the transmitter.
Attempts to produce omni-directional aerials for use on mobile vehicles have hitherto not proved entirely successful.
It is accordingly an object of the invention to provide a radio or television aerial of which the construction is such that acceptable signal reception can be obtained regardless of the relative alignment of the aerial and the transmitter, at least in the horizontal plane.
An aerial construction is known, (see U.S. Pat. No. 4,479,127) which comprises four substantially identical folded dipole elements each element defining a loop lying in a plane parallel to a common central axis which, in use, is intended to be vertical, the planes of all of said loops being equally spaced from said central axis and the planes of adjacent ones of said loops being relatively angularly displaced by 90.degree. about said central axis such that said dipole elements are arranged in mutually facing pairs disposed on opposite sides of said central axis, all of said dipole elements being connected to common whereby the polar response of said aerial is substantially circular about said axis. Such an aerial, in the case of which a horizontally polarised omni-directional radiation pattern is obtained over a wide bandwidth when used as a transmitting aerial, is, however, of relatively complicated construction, special means being necessary to obtain the required impedance of the aerial over the appropriate bandwidth. This aerial does not therefore meet the need for an omni-directional receiving aerial of simple and robust construction suitable for use by the consumer for the purpose of reception of domestic radio or television programmes.
In accordance with the invention, however, this object is achieved by a construction as outlined above which is characterised in that each folded dipole element consists of a single open ended loop of which the ends are spaced apart in the respective plane in a direction parallel to the said central axis, and that the respective ends of each loop are coupled to common terminal means, by means of twin feeders extending from said ends of the loop parallel to one another and radially towards said central axis.
The size and shape of each dipole element may vary in accordance with the frequency of electromagnetic waves to be received, and in the case of a UHF television may comprise loop aerial elements of round or square configuration. Square elements are found to be more advantageous, particularly when opposite corners of the square are aligned on vertical and horizontal axes respectively, since the aerial can be used for the reception of both horizontally and vertically polarised transmissions.
In the case of an aerial for reception of VHF frequencies, which are usually horizontally polarised, the dipole elements are preferably in the form of folded dipole of which the horizontal dimension is greater than the vertical.
An aerial in accordance with the invention has surprisingly been found to give a response that is truly omni-directional, whilst also having a very wide band-width.
One embodiment of aerial in accordance with the invention is illustrated in the accompanying drawings, in which
FIG. 1 is a perspective view of an aerial in accordance with the invention.
FIG. 2 is a view similar to FIG. 1 with components of the aerial assembly removed to show
REFERENCES:
patent: 1994237 (1935-03-01), Woods
patent: 2217911 (1940-10-01), Lindenblad
patent: 2373206 (1945-04-01), Thomas
patent: 2533900 (1950-12-01), Shanklin
patent: 2747183 (1956-05-01), Edwards
patent: 2787788 (1957-04-01), Clough
patent: 3329954 (1967-07-01), Travers
patent: 4479127 (1984-10-01), Barbano
Clark Derek J.
Clark Reginald E. J.
Johnson Doris J.
Maxview Aerials Limited
Sikes William L.
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