DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As seen in FIG.
1, our preferred form of antenna 2 includes a receiving/transmitting element 4 comprising a pair of shaped electrically conducting portions 6,8, each independently connected (as by solder) to a respective wire 10a, 10b.
The portions 6,8 are mounted on a base 12, to prevent relative movement.
The portions 6,8 are mirror-images; each is symmetrical about the centre-line of element 4 (a line left-right across the paper through the centre of the element 4, as viewed).
The portions 6,8 each have a generally rectangular form, but with a narrowed facing central part 14,16, rounded corners, and several recesses.
Thus, in this embodiment each portion has a curved recess 20, and straight-edged recesses 22 and 24.
The exact form and shape of the portions, and the recesses therein, determines the frequency range and band width over which the element will resonate, i.
e.
the frequency range and band width over which it will receive and transmit signals, as can readily be determined by those skilled in this art.
An element made substantially according to FIG.
1, and with a dimension A of 8.
3 cm, has been found to operate effectively at the 875-910 MHz frequency range.
Tests have shown that with a dimension A of 4.
17 cm the element would operate effectively at the 1800 MHz frequency, and with a dimension A of 16.
7 cm the element would operate effectively a frequency of 450 MHz (a frequency used for the UHF mobile communications system).
The portions 6,8 are of copper.
In this embodiment the antenna 2 is manufactured using as a starting material a slab of 0.
08 cm thick fibre glass laminate (as an insulating base), roller coated on both sides with a 0.
01 cm thick layer of copper, made as would be a slab for a double-sided printed circuit board.
Selected regions of the copper on one face of the base are etched away around the portions 6,8 (FIG.
1), in known fashion until the base 12 locally is exposed.
To the other side of base 12 the copper is also etched away to provide a pair of reflecting panels 30 (FIG
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