Patent ID: 7502638

Claim:
An antenna device comprising: a circuit board including a communication circuit and a ground portion; an information transmitting/receiving antenna electrically connected to the ground portion and operating using the ground portion as an element of the information transmitting/receiving antenna, the information transmitting/receiving antenna being disposed on the circuit board; a tunable receiving antenna of a frequency-changeable type electrically connected to the ground portion and operating using the ground portion as an element of the tunable receiving antenna, the tunable receiving antenna being disposed on the circuit board at a distance from the information transmitting/receiving antenna; and a signal-band separating circuit disposed between the ground portion and the information transmitting/receiving antenna for separating signals in a frequency band for communication transmitted and received by the information transmitting/receiving antenna from signals in a frequency band for reception received by the tunable receiving antenna, the frequency band for reception being different from the frequency band for communication; wherein the signal-band separating circuit is connected to the ground portion via an impedance such that the signals in the frequency band for communication are transmitted between the communication circuit and the information transmitting/receiving antenna and such that the signals in the frequency band for reception are transmitted between the information transmitting/receiving antenna and the ground portion via the impedance, and at least the antenna length of the information transmitting/receiving antenna functions as a part of the antenna length of the tunable receiving antenna such that the sensitivity of the tunable receiving antenna is compensated in the frequency band received by the tunable receiving antenna; and both communication with the signals in the frequency band for communication and broadcast reception with the signals in the frequency band received by the tunable antenna are provided.