Hitachi Patent: Triple-Conversion Super-Heterodyne HDTV Signal Receiver Using QAM Demodulation

MicroPatent via Individual Inc. : Abstract: 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.

Ex Claim Text: A high definition TV signal receiver comprising: an input filter extracting a desired signal from input radio frequency signals; a radio frequency amplifier amplifying or attenuating said desired signal of said input filter; a first local oscillator outputting a first local oscillation signal at an oscillation frequency corresponding to channel selection information; a first frequency converter converting said desired signal which is an output signal of said radio frequency amplifier to a first intermediate frequency signal in accordance with said first local oscillation signal; a first intermediate frequency filter extracting said first intermediate frequency signal from an output signal of said first frequency converter; a first intermediate frequency amplifier amplifying said first intermediate frequency signal; a second local oscillator outputting a second local oscillation signal; a second frequency converter converting said first intermediate frequency signal to a second intermediate frequency signal utilizing said second local oscillation signal; a second intermediate frequency filter extracting only said second intermediate frequency signal from an output signal of said second frequency converter; a second intermediate frequency amplifier amplifying or attenuating said second intermediate frequency signal; a third local oscillator outputting a third local oscillation signal; a third frequency converter converting said second intermediate frequency signal to a third intermediate frequency signal utilizing said third local oscillation signal; a third intermediate frequency filter extracting only said third intermediate frequency from an output signal of said third frequency converter; a third intermediate frequency amplifier amplifying said third intermediate frequency signal; a first demodulator demodulating said third intermediate frequency signal, and also generating a first AFC voltage finely tuning the oscillation frequency of said third or second local oscillator and a first AGC voltage controlling the amplification degree of said third intermediate frequency amplifier; a filter having frequency characteristics reducing a frequency component, which is equal to a carrier component in a TV signal of a standard system, of said third intermediate frequency signal which is supplied from said third intermediate frequency amplifier; a detector detecting an output signal from said filter; and a smoothing amplifier smoothing an output signal of said detector and amplifying it to a desired voltage, when said desired signal from said input radio frequency signals is a high definition TV signal having an occupied band width which is the same as that of the TV signal of the standard system, and wherein an output signal of said smoothing amplifier is a gain control signal of said radio frequency amplifier and said second intermediate frequency amplifier.

Assignee: Hitachi, Ltd.

Patent Number: 5572264

Issue Date: -&dD1996 11 05-&d@

Inventor(s): Mizukami, HiroyukiIgarashi, Yutaka

Nagashima, Toshio

If you would like to purchase a copy of this patent, please call MicroPatent at 800-984-9800.High definition TV signal receiver (Assignee -- Hitachi, Ltd.)

Source: MicroPatent

MicroPatent via Individual Inc. : Abstract: 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.

Ex Claim Text: A high definition TV signal receiver comprising: an input filter extracting a desired signal from input radio frequency signals; a radio frequency amplifier amplifying or attenuating said desired signal of said input filter; a first local oscillator outputting a first local oscillation signal at an oscillation frequency corresponding to channel selection information; a first frequency converter converting said desired signal which is an output signal of said radio frequency amplifier to a first intermediate frequency signal in accordance with said first local oscillation signal; a first intermediate frequency filter extracting said first intermediate frequency signal from an output signal of said first frequency converter; a first intermediate frequency amplifier amplifying said first intermediate frequency signal; a second local oscillator outputting a second local oscillation signal; a second frequency converter converting said first intermediate frequency signal to a second intermediate frequency signal utilizing said second local oscillation signal; a second intermediate frequency filter extracting only said second intermediate frequency signal from an output signal of said second frequency converter; a second intermediate frequency amplifier amplifying or attenuating said second intermediate frequency signal; a third local oscillator outputting a third local oscillation signal; a third frequency converter converting said second intermediate frequency signal to a third intermediate frequency signal utilizing said third local oscillation signal; a third intermediate frequency filter extracting only said third intermediate frequency from an output signal of said third frequency converter; a third intermediate frequency amplifier amplifying said third intermediate frequency signal; a first demodulator demodulating said third intermediate frequency signal, and also generating a first AFC voltage finely tuning the oscillation frequency of said third or second local oscillator and a first AGC voltage controlling the amplification degree of said third intermediate frequency amplifier; a filter having frequency characteristics reducing a frequency component, which is equal to a carrier component in a TV signal of a standard system, of said third intermediate frequency signal which is supplied from said third intermediate frequency amplifier; a detector detecting an output signal from said filter; and a smoothing amplifier smoothing an output signal of said detector and amplifying it to a desired voltage, when said desired signal from said input radio frequency signals is a high definition TV signal having an occupied band width which is the same as that of the TV signal of the standard system, and wherein an output signal of said smoothing amplifier is a gain control signal of said radio frequency amplifier and said second intermediate frequency amplifier.

Assignee: Hitachi, Ltd.

Patent Number: 5572264

Issue Date: -&dD1996 11 05-&d@

Inventor(s): Mizukami, HiroyukiIgarashi, Yutaka

Nagashima, Toshio

If you would like to purchase a copy of this patent, please call MicroPatent at 800-984-9800.