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A six-element endfire array is proposed for coal mine or tunnel communication in this letter. To further decrease the end cross section, which has adverse effect on air ventilation, meander-line folded dipoles are used as antenna elements. By the antenna itself, the cross section toward the ventilation direction is only 100 × 1 mm2. A prototype array is fabricated and tested. Bidirectional endfire radiation patterns with low cross-polarization levels in the azimuth and elevation plane are achieved. The measured - 10-dB bandwidth is approximately 7.5% (834-899 MHz), and the corresponding peak gain is 8.05-9.05 dBi.
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Liu et al. (2012) studied this question.
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