An equivalent circuit is derived for an antenna coupled to a shielding cavity via field analysis. The input impedance of the antenna inside the cavity is then studied theoretically and experimentally. It is shown that the input resistance of the antenna shielded by the cavity is not merely the loss resistance, but is actually the sum of the antenna loss resistance and the coupling resistance between the antenna and cavity. This coupling effect is demonstrated quantitatively by numerical computations for dipole antennas. A method is proposed to avoid the antenna-cavity antiresonance in the measurement of loss resistance of the antenna.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering