Loop antenna with series resonant circuit and parallel reactance providing dual resonant frequencies
First Claim
1. A loop antenna apparatus comprising a loop of conductive material, feed means coupled to the loop, and a reactive network electrically connected in series with the loop for tuning the loop to at least first and second resonant frequencies, said reactive network including:
- a. a series resonant circuit having substantially zero reactance at the first resonant frequency; and
b. reactive means electrically connected in parallel with the series resonant circuit for cooperating with said circuit to tune the loop to at least the second resonant frequency.
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Accused Products
Abstract
A loop antenna (10) is provided with feed means (12,14) and a variable capacitor (C1) to adjust a first resonant frequency of the antenna (10). A reactive network (C2,L2,X) is included which permits the antenna to provide a further resonant frequency. The reactive network comprises a series-resonant circuit (L2,C2) in parallel with a further reactive element (X). The resonant frequency of the series-resonant circuit is arranged to be substantially equal to the first resonant frequency of the antenna as tuned by the capacitor (C1). The reactance (X) thus has no effect at this frequency. Another resonant frequency for the antenna may be adjusted by altering the reactance (X). The arrangement may be extended to provide further resonant frequencies.
40 Citations
11 Claims
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1. A loop antenna apparatus comprising a loop of conductive material, feed means coupled to the loop, and a reactive network electrically connected in series with the loop for tuning the loop to at least first and second resonant frequencies, said reactive network including:
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a. a series resonant circuit having substantially zero reactance at the first resonant frequency; and b. reactive means electrically connected in parallel with the series resonant circuit for cooperating with said circuit to tune the loop to at least the second resonant frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification