Antenna apparatus and portable radio apparatus

摘要

An antenna apparatus for use in a portable cellular telephone that can avoid deterioration in signal radiation characteristics caused by the adverse influence of a user's head during the use of the telephone. Two sleeves have been fixed to a housing for a portable cellular telephone. A linear radiating conductor having a lambda /4-electrical length is slidably supported by the housing by way of the two sleeves so that it can be both freely pulled out of or accommodated in the housing. The radiating conductor is extended at one end on the side of the power-feed point by a length equivalent to n lambda /2. Also, a tubular conductor is coaxially disposed with the extended portion so as to form a power-feed coaxial line. When the radiating conductor is pulled out of the housing to such a degree as to reveal the coaxial line, the monopole antenna projects sufficiently away from a user's head, and a deterioration in signal radiation characteristics can thus be prevented.