This paper proposes a new circuit model for E-shaped patch antennas (ESPA) using the multiconductor transmission line mode theory (the modal theory). First, radiation and transmission line modes generated on the ESPA are described, and an equivalent circuit is derived from the modal theory. The equivalent circuit is analyzed in detail to obtain wideband and multiband characteristics. For wideband ESPAs, the theoretical maximum bandwidth is derived under VSWR criterion. Dual-band ESPA is also discussed theoretically. Finally, impedance characteristics obtained by the circuit model are compared with full-wave electromagnetic simulations and measurements.