In the conventional antenna system for the handset, some gain degradation h
as been observed when an operator holds the handset. This is caused by the
variation of the current on the conducting box used in the handset due to t
he body effect. This paper presents (1) design concept of antenna for the h
andset and (2) analysis of a newly proposed loop antenna system, which has
the balance structure for the antenna feed to reduce the effect of currents
on the conducting box. In order to confirm the effectiveness of using the
balance-fed loop antenna, a simple model using a small loop antenna mounted
on a ground plane is analyzed. The current distribution for the balance-fe
d loop antenna system is obtained calculatedly and also experimentally and
is compared with that for the unbalance-fed loop antenna system. In a resul
t, remarkable decrease in the current distribution on the ground plane for
the case of the balance-fed antennas system is shown. Calculated results ar
e in good agreement with measured results.