Wideband Microstrip Antenna in Small Volume Without Using Fundamental Mode

Microstrip antennas are of significant interest and extensively utilized in communication systems because of their unique low profile. However, the general difficulty in microstrip antenna design lies in its wideband electromagnetic radiation within a low-profile structure. To enhance the bandwidth, superposing the fundamental mode and other high-order modes is the most common method, but this occupies a larger footprint than regular narrow-band modes. Here, as a counterintuitive way to broaden the bandwidth, a wideband miniaturized microstrip antenna is proposed by using two high-order modes. The avoidance of the fundamental mode allows for footprint miniaturization without decreasing the bandwidth, providing a different but feasible design strategy for wideband microstrip antennas. Compared with other microstrip antennas at the same profile, the proposed antenna achieves wider bandwidth and a smaller footprint. The experimental result shows a bandwidth of 4.81-6.01 GHz is achieved with a volume of 0.47 ×0.47 × 0.043 λ 0 ³ , where λ 0 represents the in-vacuum wavelength at the center frequency. Therefore, the proposed design provides an effective solution to the intrinsic contradiction between wideband electromagnetic radiation and compact antenna dimensions, not only in a low profile but in a small footprint, contributing to the fundamental development of microstrip antennas.