| 摘要 |
PURPOSE: A vehicle television with a diversity antenna circuit is provided to reduce costs and space occupation, while achieving improved productivity by eliminating an additional assembly process. CONSTITUTION: A vehicle television comprises a diversity module(41), a tuner pack(42), an audio/video unit(43), and a micro computer(32). The diversity module includes the first to fourth antennas(ANT1 to ANT4); an antenna switching part(21) for connecting one of the antennas to a tuner(22); and a switching driving part(33) for driving the antenna switching part. The tuner pack includes the tuner for receiving the carrier frequency of the channel selected by a user and converting the received carrier frequency into an intermediate frequency; a SAW filter(23) arranged at the output terminal of the tuner; an amplifier(24) for amplifying the intermediate frequency into a predetermined level; and a detector(25) for detecting the reference frequency from the intermediate frequency output from the amplifier. The audio/video unit includes a video demodulator(26) for demodulating the video intermediate frequency in accordance with the reference frequency and converting the demodulated frequency into the video signal of the base band; an audio demodulator(27) for demodulating the audio intermediate frequency in accordance with the reference frequency and converting the demodulated frequency into the audio signal of the base band; a level detector(28) for detecting the level of the intermediate frequency and converting the level of the intermediate frequency into a DC voltage; a synchronous signal separator(29) for separating a horizontal synchronous signal from the video signal; a noise amplifier(30) for amplifying the noise contained in the video signal; and a noise comparator(31) for comparing the noise signal output from the noise amplifier with the reference level. The micro computer stores the output value of the level detector of the antenna where the signal having the noise level lower than the reference level is input, and controls the antenna having the maximum DC value to be connected to the tuner. |
