A Dual Band Microstrip-Fed Slot Antenna

A simple new design method to achieve a dual band microstrip-fed slot antenna is presented. It is shown that when two slot antennas are placed in series, the spacing between the two antennas can be adjusted to achieve an effective secondary resonance. The new resonance is found to be due to the mutual coupling between the two slot antennas. An approximate circuit model for the dual band antenna is presented to explain the dual band mechanism and to provide a design guideline. The model is validated with a prototype antenna that operates at 4.22 GHz and 5.26 GHz, which are commonly used as the downlink and uplink in satellite communications. Measured results show good return loss at both frequencies, and radiation patterns agree well with the simulations. The proposed antenna has a simple geometry can be easily produced using printed circuit board techniques for applications where compactness and multiband operation are of interest.