Analysis and Resonant Length Formulation of Dual Band Microstrip Antenna with Modified Ground

A dual band microstrip antenna with defected ground plane is proposed in this paper. The dual bands are achieved by appropriately embedding pair of slots on the ground plane to tune TM 30 mode resonant frequency. These slots essentially reduces $\mathbf{TM}_{\pmb{30}}$ mode frequency and places it closer to fundamental mode frequency. Broadside radiation pattern is observed at both the frequencies with maximum gain of nearly 3 dBi. The effect of the ground slot is studied and are portrayed by showing resonance plot for variation in the slot length. Empirical formulation of resonant length for fundamental as well as higher order $\mathbf{TM}_{\pmb{30}}$ mode frequency is suggested in the paper. The calculated frequencies obtained using the proposed formula closely matches with the simulated values. Thus these formulas can be applied to design dual band antenna with similar configuration at any given operating frequency.