Читать книгу Antenna and EM Modeling with MATLAB Antenna Toolbox - Sergey N. Makarov - Страница 26

The dipole antenna discussed thus far is a classic example of a narrow‐band antenna that has its first resonance as a series resonance. In general, a resonance is characterized by a zero reactance, X_a = 0. However, the resistance value can vary dramatically depending on the type of resonance, i.e. series or parallel. Parallel resonances typically achieve large resistances. In the case of the dipole, the series resonances occur at odd multiples of f_res. In general, the dipole is not used at higher multiples of the fundamental resonance. The half‐wavelength current distribution is no longer valid at these frequencies and therefore the radiation pattern of the antenna is also distorted.