| 摘要 |
628,987. Aerials. CORK, E. C. Oct. 1, 1946, No. 29183. [Class 40 (vii)] An aerial resonant in two or more frequency bands comprises a conductor series loaded by reactive elements including an inductance shunted by a capacity, said elements being disposed along the conductor so that the distances between them are always short compared with the operating wavelength and being of such magnitude that the same length of conductor is effective and resonant in each band. The Figure shows a portion of an aerial 10 interrupted by loading elements 11 comprising inductors 12 with capacitors 13 in parallel with at least a portion thereof. Values of components and the aerial length are chosen so that in the lower frequency band the aerial is inductively loaded and resonant while in the higher frequency band it is capacitively loaded and resonant. If the capacitors 13 are shunted across only part of the inductors, a series tuned circuit is formed at a third frequency, whereby the aerial is effectively unloaded and if the natural length is suitably chosen the aerial is then resonant at this third frequency. It is pointed out that the elements 11 may also approach infinite impedance at a further frequency, so splitting the aerial into a string of individual elements. |
