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A new type of dual frequency antenna is introduced by combining a helical and a monopole antenna. The antenna configuration is shown to operate at two discrete frequencies, i.e. ~900 and 1800 MHz. The size of the antenna configuration can be decreased at the cost of the bandwidth. The bandwidth is shown to increase by adding a reactive matching network to the antenna.
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Erätuuli et al. (1996) studied this question.
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