Based on characteristic mode analysis (CMA), a novel method for reshaping the TM00 mode of the rectangular patch antenna (RPA) is presented. Initially, the RPA loaded by periodic shorting vias, as the basic structure for generating the TM00 mode, is investigated by CMA. The nonbroadside pattern of TM00 mode is revealed to be caused by the vertical currents on the shorting vias. And it can be transformed into a broadside direction by replacing the vertical vias with a new shorting structure possessing strong horizontal currents. Moreover, to further verify the feasibility of the proposed method, a compact CPW-fed aperture-coupled RPA for the WLAN application is designed. By simultaneously exciting a reshaped TM00 mode, a fundamental TM10 mode, and a slot mode, the proposed RPA can achieve dual-band performance with broadside radiation features. Finally, the proposed antenna is fabricated and tested. The results illustrate that the fabricated antenna can achieve good impedance matching and broadside radiation characteristics in 2.4–2.46 GHz and 5.1–5.6 GHz bands.