A very small folded-spiral monopole for handheld devices

When wound into a spiral, a /spl lambda//4 monopole is reduced to 1/16 /spl lambda/ (or even smaller in its linear dimensions) while its resonant frequency of zero reactance remains approximately unchanged. The radiation resistance, however, is reduced from 40 ohms to around 15 ohms depending on the configuration of the spiral, and the size and shape of the handheld device as ground. Through a proper choice of folding of the spiraled monopole, the 15 ohm (or other small radiation resistance) can be raised to a suitable 50 ohm with low ohmic loss, and with acceptable bandwidth (4.2%). This paper synthesizes such a folded-spiral monopole.