Antenna analysis based on integrating concept of a small portable radio unit

A new analysis model of a portable radio antenna is proposed to investigate the characteristics of the antenna; the influence of the feeding circuit and the box covering the circuit are considered. The existing model used to analyze half wavelength whip antennas ignores the feeding circuits as radiating elements. However, recent radio equipment has become much smaller, and the existing analysis model and the real structure of the radio unit are diverging from the view points of the electrical design. Since the feeding circuits are not completely enclosed in modern units, coupling between the antenna element and the feeding circuit occurs and some unbalanced current mode in the circuit may radiate, but these phenomenon cannot be analyzed using the existing model. This paper proposes a new analysis model of portable radio antennas. A numerical analysis is carried out by using the FDTD method. This model is based on the concept of integrating the necessary parts for the analysis and includes the transmission line and the matching circuit, as well as the radiation element and the metal box of the radio unit. Some fundamental numerical data are presented and it is shown that the model produces a more realistic analysis of portable radio antennas.<>