An accurate method to measure the antenna impedance of a portable radio

Traditional impedance measurement of a monopole antenna is inaccurate due to a likely stray radiating current on the measuring cable that is also affected by the operating human. This letter demonstrates experimentally that the elimination of this stray current is possible by using a special sleeve balun suitable for varied PCB ground-plane and human postures. Adjustment of the balun position is discussed. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 349–352, 1999.