초록 ▼

To make it possible to receive a modulated signal which is obtained by suppressing a carrier signal such as a high definition TV signal which is digitally demodulated such as QAM (quadrature amplitude modulation), a receiver of the double super-heterodyne system having the first and second mixers 9

To make it possible to receive a modulated signal which is obtained by suppressing a carrier signal such as a high definition TV signal which is digitally demodulated such as QAM (quadrature amplitude modulation), a receiver of the double super-heterodyne system having the first and second mixers 9 and 13 is a basic constitution. A band pass filter having a flatness in pass band and a small deviation of group delay which will prevent the demodulation of a high definition TV signal from degradation is used a first intermediate frequency filter 11. An SAW filter is used as a second intermediate frequency filter 16. The third mixer 28 for converting a second intermediate frequency signal to a third intermediate frequency signal in frequency is installed and the frequency of the third intermediate frequency signal to be converted is set to a value lower than the frequency of the second intermediate frequency signal. The demodulator 33 for a high definition TV signal is installed so as to demodulate a high definition TV signal included in the third intermediate frequency signal.

대표청구항 ▼

[ What is claimed is:] [1.] A digital broadcast receiver capable of receiving digitally modulated television (TV) signals, said receiver comprising:a first frequency converter adapted to convert a received digitally modulated TV signal into a first intermediate frequency signal in a transmission ban

[ What is claimed is:] [1.] A digital broadcast receiver capable of receiving digitally modulated television (TV) signals, said receiver comprising:a first frequency converter adapted to convert a received digitally modulated TV signal into a first intermediate frequency signal in a transmission band lower than the digitally modulated TV signal, said first intermediate frequency signal having a frequency in a standard TV band and useable in demodulating standard TV signals;a band-pass filter for selective pass-through of the first intermediate frequency signal as converted by said first frequency converter while eliminating disturbance from its neighboring signals;a phase-lock loop (PLL) circuit for controlling an oscillation frequency of a local oscillator in said first frequency converter by comparing the oscillation frequency to an oscillation signal of a reference oscillator;a second frequency converter adapted to convert the first intermediate frequency signal passed through said band-pass filter into a second intermediate frequency signal lower in frequency than said first intermediate frequency signal; anda digital demodulator adapted to demodulate the second intermediate frequency signal as converted by said second frequency converter.