In this paper, design concept of multilayer, compact antipodal slot antenna with high performance is presented. The sandwich feed line is connected to two feed pads printed on both sides of a substrate by a metallic via so that the coaxial-cable connector or other components can be directly connected to the antenna. The new antenna's impedance bandwidth is from 3.12GHz to 10.8GHz, which is about 3.4:1. Stable omnidirectional radiation patterns with low cross-polarization level, gain flatness of less than 3dB over the frequency range are also obtained.