Low-Profile and Wideband Microstrip Antenna Using Quasi-Periodic Aperture and Slot-to-CPW Transition

In this communication, we propose a new type of compact and wideband coplanar waveguide (CPW)-fed microstrip antenna. Very different from traditional microstrip antennas, the proposed design has the quasi-periodic radiating aperture fed through the slot-to-CPW transition. By optimizing the geometry of the quasi-periodic aperture and the slot-to-CPW transition, the fundamental TM₁₀ mode and antiphase TM₂₀ mode can be efficiently excited, coupled, and matched over a broad bandwidth. We have fabricated and characterized the proposed antenna, and found a good agreement between measurement and simulation results. Our experimental results show that despite the antenna has a thickness of only <inline-formula> <tex-math notation="LaTeX">$0.052\lambda _{0}$ </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at the center frequency), it exhibits a −10 dB impedance bandwidth of 36.5% (3.96–5.73 GHz), a 3 dB gain bandwidth of 35.4% (4–5.72 GHz), and a maximum available gain of 10.45 dBi. Our findings may offer a feasible solution to realize wideband microstrip antennas using a single-layer substrate, with unique merits, such as low profile, low cost, and ease of fabrication.