| 摘要 |
A broadband antenna in either the monopole or dipole configuration has an impedance broadbanding potentiality superior to those of known broadband antennas such as the triangular, helical and log-periodic antennas. Compared with the forementioned antennas in corresponding operating frequency ranges (expressed by the ratio of maximum to minimum frequency), the 'Elliptic sheet antenna' has the merits of: (i) markedly lower variation of input resistance (Rin) as expressed by the ratio of maximum-to-minimum of Rin, (ii) markedly lower values of input reactance (Xin) and lower reactive content in the impedance, as expressed by the ratio ¦Xin¦/¦Zin¦, (iii) preferable input resistance level, being nearly matched to that of the Standard 50 Ohms coaxial line, when the new antenna is used in the monopole configuration, (iv) wider operating frequency range if determined by a maximum tolerable standing wave ratio (SWR) as is specified in television, (v) lower SWR for equal frequency ranges. The merits of the new antenna reduce the main drawbacks of the other antenna, namely: (i) reflection loss and the corresponding variation with frequency of radiated power for a constant transmitter power, (ii) complex matching networks and power loss therein, (iii) limitation of frequency range of a single antenna when a tolerable maximum SWR is specified; more than one antenna should be used for broader frequency ranges. The antenna geometry and construction are simpler than with the other broadband antennas. The elliptic sheet antenna may be used either as a single element, or as a member of an array.
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