A novel design approach to wideband, triple-mode resonant microstrip patch antenna with enhanced backfire gain and low side-lobe level, is advanced. The antenna consists of a 2.0-wavelength sectorial magnetic dipole and an annular sector reflector which width is an odd multiple(s) of 1/4-wavelength. Under high-order mode resonance, the principal radiator and the reflector can be tuned to electrically couple, thus simultaneously to yield enhanced backfire radiation and low side-lobe level. As is numerically simulated and experimentally validated, the width of reflector is finally determined to be 3/4-wavelength. In that fashion, the antenna exhibits an impedance bandwidth of 43.6%, with a backfire gain up to 7.3 dBi and a first side-lobe level as low as -16.4 dB in V2X-band within xy-plane.