Design of Broadband Aperture-Coupled Stacked Microstrip Antennas Using Second-Order Filter Theory

• Published in: IEEE transactions on antennas and propagation Vol. 70; no. 7; pp. 5345 - 5356
• Main Authors: Garcia-Alcaide, Nieves, Fernandez-Prieto, Armando, Boix, Rafael R., Losada, Vicente, Martel, Jesus, Medina, Francisco
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-07-2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antenna design; Antenna theory; Antennas; Aperture coupled antennas; Apertures; Broadband; Broadband antennas; Chebyshev approximation; Circuit design; Design modifications; Equivalent circuits; Filtering theory; Least squares method; Mathematical models; Microstrip; Microstrip antennas; Microstrip filters; Modelling; Parameter modification; Patch antennas; Resonators
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2022.3161345

In this article, the authors propose a lumped circuit methodology for the design of broadband stacked microstrip patch antennas fed through an aperture. First, an equivalent circuit (EC) is introduced for the antenna. The EC consists of an <inline-formula> <tex-math notation="LaTeX">LC </tex-math></inline-formula> series resonator modeling the feed plus two capacitively coupled <inline-formula> <tex-math notation="LaTeX">LC </tex-math></inline-formula> parallel resonators accounting for the radiating patches. Then, a deembedding procedure based on total least squares method is introduced to determine all the parameters of the antenna EC. Second, the circuit stage modeling the patches is designed as a second-order Chebyshev filter based on coupled resonators. Since the standard Chebyshev approach leads to circuit parameters that cannot be physically obtained in practice, a modified second-order quasi-Chebyshev design is presented, which can be physically implemented by stacking one conventional rectangular patch above one rectangular patch with both inner and meandering slots. The proposed methodology is used to design an antenna with over 30% bandwidth at a center frequency of 5.57 GHz. A prototype has been fabricated and measured, and good agreement has been found between simulations and experiments.