Design and transmission line model analysis of a compact dual-frequency antenna

In this study, a compact dual-frequency antenna with stacked configuration is proposed, and the transmission line model for the antenna is also studied. Compared with the conventional stacked dual-frequency antenna, the radiating element with half-guided wavelength at the first resonant frequency is arranged on two layers connected through one via hole, thus the dimension of the antenna can be reduced effectively. Each patch of the antenna is modelled as a section of transmission line terminated by two radiating slots, and a via hole between stacked patches is represented by an inductor and a capacitor in parallel. In particular, the formula for the capacitor of a via hole between stacked patches is provided when the antenna is fed from the upper patch. To validate the transmission line model, two compact dual-frequency antennas are designed and fabricated. The results of simulations and measurements indicate that the proposed transmission line model is suitable for analysing compact dual-frequency antennas with stacked configuration.