Retractable broad-band antenna for portable telephones

摘要

A retractable broad-band antenna for a portable telephone which includes a first antenna element which resonates in the lower region of the frequency band, a second antenna element which is coupled in series to the first antenna element via electrostatic capacitance and resonates in the higher region, and a call-receiving third antenna element mounted to the tip end of the second antenna element. The first and second antenna elements are shortened antenna elements in a form of helical coils. The first antenna element has an electrical length of lambda L/8 and is a non-grounded type having broad band characteristics by means of a matching device; and the second element has an electrical length of lambda H/2 wherein lambda H and lambda L are respectively the wave lengths at a center frequency of the higher and lower region of the frequency band used. The third antenna element preferably has a conductive contact so that the tip portion of the second antenna element, which stays outside of the telephone housing when the base portion of the second antenna element is retracted into the housing, can act as a call-receiving antenna element.