A probe-fed L-shaped plate antenna is presented for the enhancement of the impedance bandwidth. The radiating plate is suspended at a large height above a ground plane. The impedance characteristics of the antenna are investigated experimentally and numerically. The results demonstrate that the probe-fed L-shaped plate antenna operating in two adjacent modes has achieved a 24% impedance bandwidth for 2:1 VSWR without any additional matching network or any parasitic elements. The parametrical study on the spacing and the dimensions of the plate is performed using a commercial software package. Furthermore, a new parameter called matching factor is suggested to assess the matching performances of broadband antennas. ¿ 2001 American Geophysical Union