| 摘要 |
628,929. Impedance networks. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Aug. 8, 1947, No. 21988. Convention date, Feb. 28, 1946. [Class 40 (viii)] [Also in Group XL (c)] An antenna is coupled to a feeder through an impedance matching section substantially shorter than one quarter wavelength at that frequency and having a characteristic impedance greater than the geometric mean of the resonant input impedance of the antenna and the characteristic impedance of the feeder, these two quantities having a ratio substantially greater than unity. As shown, a quarter wave antenna comprises a rod 10 protruding from a sleeve 12 whose outer surface forms the lower half of the antenna. Within sleeve 12 is the series impedance matching section comprising the inner surface of sleeve 12 and an inner rod 14 forming a continuation of rod 10. At the lower end of the impedance matching section and below ground plane GP, the outer conductor 16 of the co-axial feeder TL is connected to the sleeve 12 and ground plane GP, the inner conductor 18 being connected to rod 14. It is shown mathematically how to derive, for a specified maximum permissible standing wave ratio, the necessary values of the characteristic impedance and length of the matching section and the antenna input impedance, to ensure optimum matching conditions over the frequency band to be radiated. |
