| 摘要 |
A multiple frequency band antenna arrangement comprises a small loop antenna element 1 connected in series to a tank circuit 6. The tank circuit 6 consists of an inductor 15 connected in parallel to a capacitor 14. The tank circuit 6 provides another resonant frequency band of operation, of a quarter wavelength loop antenna, above that provided by the loop antenna itself. This means that the loop antenna may be operated in the extra frequency band without altering a coupling transformer 3 impedance ratio. As a result, it is simple to use a variety of different shaped loop elements. The compact antenna may be used in mobile, military or covert communication systems. The antenna may be formed with elements wound in a non-inductive manner and supported by an inflatable tubular structure. Plug and socket connections may be used such that the tank circuit 6 may be readily changed. The said arrangement may use variable inductor and capacitor components to adjust the tuning. Two whip antennas may be joined to form a loop antenna element. The position of the antenna arrangement, or one or more of its adjustable circuit components, may be altered by a remotely activated motor. |
