We present a new method for designing a multi-band antenna. The radiating element in the basic study was a monopole antenna. This antenna naturally exhibited dipole and quadrupole modes for the fi rst and second resonance frequencies, respectively. Adding two parasitic elements to the antenna, the quadrupole mode changed into a dipole mode. This antenna is called an open-sleeve monopole antenna. The lengths of the parasitic elements were analytically defined in simulation and measurement. The first and second modes of the antenna were studied with and without the parasitic elements over the frequency range of 400 MHz to 2000 MHz. The radiation patterns in the far fi eld were studied via simulation and measurement. To understand the behavior of the antenna, the magnetic fi eld was also studied in the near field in simulation and measurement