Antenna device shared by three kinds of waves

Claim 1

An antenna device for allowing an AM-FM radio receiver to receive AM and FM broadcast signals and allowing a vehicle telephone transceiver to transmit and receive a telephone signal, said antenna device comprising: a single two-stage collinear array antenna comprising fractional-wave dipole antennas which are adapted for the telephone signal and stacked in two stages; a first coaxial cable for applying the AM and FM broadcast signals received by said antenna to the AM-FM receiver; a second coaxial cable connected between a base end of said antenna and the telephone transceiver for applying the telephone signal received by said antenna to the telephone transceiver and the telephone signal outputted by said telephone transceiver to said antenna, the impedance at said end of said antenna being substantially equal to the impedance of said second coaxial cable in response to the telephone signal; first impedance matching circuit means connected between said base end of said antenna and said first coaxial cable for selectively matching the impedance at said base end of said antenna to the impedance of said first coaxial cable in response to the AM broadcast signal; and second impedance matching circuit means connected between said base end of said antenna and said first coaxial cable for selectively matching said impedance at said base end of said antenna to said impedance of said first coaxial cable in response to the FM broadcast signal; said first and second impedance matching circuit means feeding respective AM and FM output signals thereof to the AM-FM radio receiver via said first coaxial cable; said first impedance matching circuit means comprising: a first bandpass filter for selectively passing only the AM broadcast signal therethrough; and a first impedance matching circuit connected to an output of the first bandpass filter for selectively matching said impedance at said base end of said antenna to said impedance of said first coaxial cable in response to the AM broadcast signal; and said second impedance matching circuit means comprising: a second bandpass filter for selectively passing only the FM broadcast signal therethrough; and a second impedance matching circuit connected to an output of the second bandpass filter for selectively matching said impedance at said base end of said antenna to said impedance of said first coaxial cable in response to the FM broadcast signal.