EP0716518A2
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EP
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Narrow-band quadrature demodulator for digital audio broadcast via satellite
Assignee: Broadcom Corp
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Filing: 1995-11-29
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Granted: —
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Expires: 2015-11-29
Abstract
Abstract A direct broadcast satellite sends subscribers signals received from an earth-station transmitter and typically having a 10 MHz bandwidth, 6 MHz for an analog video station and 4 MHz for up to 24 digital audio stations. When a subscriber selects one of the audio stations, an FM demodulator recovers the 10 MHz signal; a variable gain amplifier amplifies the received signal; and an A/D converter digitizes the amplified signal at (e.g.) 24.576 MHz. A digital synthesizer produces trigonometric functions (sine, cosine) at (e.g.) 24.576 MHz, and mixers downconvert the signals to baseband. The sampling frequency is then reduced to 256 KHz, twice the digital audio signal baud rate. In response to the 256 KHz signals, a first servo varies a VCO frequency to obtain a regulation by the A/D converter of the digitizing frequency at 24.576 MHz and another servo regulates the frequency of the trigonometric functions. A microcomputer provides a fixed coarsely amplified gain to the 256 KHz signals dependent upon the relative amplitudes of the video and audio signals. The amplitudes of the coarsely amplified signals are detected, filtered and converted to an analog voltage to precisely regulate the gain of the variable gain amplifier. The sampling frequency of the signals at the outputs of the programmable gain stages is reduced to 128 KHz (i.e. the transmitted baud frequency). A Viterbi decoder corrects errors in these in-phase and quadrature baseband "soft-decision" signals. The resulting 192 kb/s output data stream is decompressed and converted to stereo audio sound.
Inventors
- 👤 Henry Samueli
- 👤 Kenneth R. Kindsfater
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 07:27
CPC Classifications
H; H04; H04H; H04H40/00; H04H40/18; H04H40/27; H04H40/90; H04H20/00; H04H20/28; H04H20/33; H04H20/34; H04H20/44; H04H20/46; H04H20/51
Claims Analysis
Total Claims: 36
Claim 1
Independent Claim
172 words
In combination in a direct broadcast system having a plurality of channels each with a particular range of frequencies and with an analog video signal occupying a portion of the range of frequencies in the channel and with a plurality of digital audio signals occupying the remainder of the range of frequencies in the channel, the combination being provided to select a particular one of the digital audio signals in the channel, first means for receiving the analog video signals and the digital audio signals in the channel, second means for digitally processing the analog video signals and the digital audio signals at a particular sampling frequency, third means responsive to the digital signals from the second means for controlling the operation of the second means to maintain the digital processing of the analog video signals and the digital audio signals at the particular sampling frequency, and fourth means responsive to the digital signals from the second means for processing the digital signals to recover the audio information in the particular channel.
Claim 2
Dependent Claim
74 words
In a combination as recited in claim 1 wherein the third means includes fifth means for reducing the sampling frequency of the processed signals after the processing of the signals at the particular sampling frequency, and the third means includes sixth means responsive to the signals from the fifth means at the reduced sampling frequency for feeding such signals back to the second means for regulating the digital signals at the particular sampling frequency.
Claim 3
Dependent Claim
69 words
In a combination as set forth in claim 1 wherein the second means includes fifth means for providing a conversion of the signals from the first means to digital signals at the particular sampling frequency and wherein the third means includes sixth means responsive to the digital signals from the fifth means for regulating at the particular sampling frequency the digital processing of the signals from the first means.
Claim 4
Dependent Claim
99 words
In a combination as set forth in claim 1 wherein fifth means convert the signals from the first means to digital signals at a particular sampling frequency and wherein sixth means demodulate the signals at the particular sampling frequency to produce quadrature components of the digital signals at the particular sampling frequency and wherein seventh means reduce the sampling frequency at which the quadrature components of the digital signals are produced and wherein eighth means regulate the operation of the second means in regulating at the particular sampling frequency the digital processing of the signals from the first means.
Claim 5
Dependent Claim
58 words
In a combination as set forth in claim 4 wherein the eighth means include ninth means for converting the digital signals from the seventh means to analog signals and include tenth means for introducing the analog signals to the second means to regulate at the particular sampling frequency the digital processing of the signals from the first means.
Claim 6
Dependent Claim
188 words
In combination in a direct broadcast system having a plurality of channels each with a particular range of frequencies and with an analog video signal occupying a portion of the range of frequencies in the channel and with a plurality of digital audio signals occupying the remainder of the range of frequencies in the channel, the combination being provided to select a particular one of the digital audio signals in the channel, first means for receiving the analog video signals and the digital audio signals, second means for amplifying the analog video signal and the digital audio signals with a variable gain, third means for digitally processing the amplified signals from the second means, fourth means responsive to the signals from the third means for providing to such signals a gain programmable in accordance with the range of amplitudes of the analog video signals superimposed with the plurality of digital audio signals, and fifth means responsive to the signals from the fourth means for regulating the gain in the amplitudes of the signals from the second means in accordance with the programmable gain provided by the fourth means.
Claim 7
Dependent Claim
81 words
In a combination as set forth in claim 6 wherein the fifth means includes sixth means responsive to the signals from the fifth means for detecting the gain of the signals from the fourth means and includes seventh means responsive to the signal gain detected by the sixth means for providing an analog signal and includes eighth means for regulating the gain of the amplification provided by the second means in accordance with the analog signals provided by the seventh means.
Claim 8
Dependent Claim
82 words
In a combination as set forth in claim 6 wherein the third means includes sixth means for digitizing the signals from the second means at a particular sampling frequency and includes seventh means responsive to the signals from the sixth means for producing quadrature components of such signals and includes eighth means responsive to the signals from the seventh means for regulating the operation of the sixth means in obtaining the particular sampling frequency for digitizing the signals from the second means.
Claim 9
Dependent Claim
63 words
In a combination as set forth in claim 8 wherein the seventh means produces the quadrature components of the signals from the sixth means at the particular sampling frequency and wherein the seventh means includes eighth means responsive to the quadrature components of the signals from the seventh means for regulating the production of the trigonometric digital signals at the particular sampling frequency.
Claim 10
Dependent Claim
117 words
In a combination as set forth in claim 6 wherein the third means includes sixth means for digitizing the signals from the second means at a first particular sampling frequency and includes seventh means responsive to the signals from the sixth means for producing quadrature components of such signals at the particular sampling frequency and includes eighth means responsive to the signals from the seventh means for reducing the sampling frequency of the quadrature components of such signals to a second particular frequency lower than the first particular frequency and includes ninth means responsive to the signals from the eighth means for regulating the particular frequency at which the trigonometric functions are produced by the seventh means.
Claim 11
Dependent Claim
36 words
In a combination as set forth in claim 10 wherein tenth means are responsive to the signals from the eighth means for regulating the particular frequency at which the signals from the second means are digitized.
Claim 12
Dependent Claim
206 words
In combination in a direct broadcast system having a plurality of channels each with a particular range of frequencies and with an analog video signal occupying a portion of the range of frequencies in the channel and with a plurality of digital audio signals occupying the remainder of the range of frequencies in the channel to select a particular one of the digital audio signals in the channel, first means for receiving the analog video signals and the digital audio signals, second means for providing a variable gain to the received signals, third means for converting the signals from the second means to digital signals at a particular frequency, fourth means for producing quadrature components of the digital signals at the particular sampling frequency, fifth means for reducing the sampling frequency of the quadrature components of the digital signals from the fourth means to a particular value, sixth means for providing a programmable gain in the signals from the fifth means in accordance with the range of amplitudes of the analog video signals superimposed with the plurality of the digital audio signals in the channel, and seventh means responsive to the programmable gain from the sixth means for regulating the gain provided by the second means.
Claim 13
Dependent Claim
26 words
In a combination as set forth in claim 12 wherein the seventh means includes an automatic gain control detector, a loop filter and a digital-to-analog converter.
Claim 14
Dependent Claim
43 words
In a combination as set forth in claim 12 wherein eighth means are responsive to the signals from the fifth means for regulating the particular frequency at which the signals from the second means are converted to digital signals by the third means.
Claim 15
Dependent Claim
37 words
In a combination as set forth in claim 12 wherein eighth means are responsive to the signals from the fifth means for regulating the particular frequency at which the trigonometric functions are produced by the fourth means.
Claim 16
Dependent Claim
78 words
In a combination as set forth in claim 12 wherein the trigonometric functions produced by the fourth means constitute sine and cosine functions and wherein the fifth means includes eighth means for reducing the sampling frequency of the quadrature signals and ninth means for combining the quadrature signals and tenth means for reducing the sampling frequency of the combined quadrature signals and eleventh means for reconstituting the individual quadrature components at the reduced frequency from the tenth means.
Claim 17
Dependent Claim
87 words
In a combination as set forth in claim 16 wherein the seventh means includes an automatic gain control detector, a loop filter and a digital-to-analog converter, twelfth means are responsive to the signals from the eleventh means for regulating the particular frequency at which the signals from the second means are converted to digital signals by the third means, and thirteenth means are responsive to the signals from the fifth means for regulating the particular frequency at which the quadrature signals are produced by the fourth means.
Claim 18
Dependent Claim
183 words
In combination for use in a direct broadcast system having a channel with a particular range of frequencies and with an analog video signal occupying a portion of the range of frequencies in the channel and with a plurality of digital audio signals occupying the remainder of the range of frequencies in the channel to select a particular one of the audio signals in the channel, first means for receiving the analog video signals and the digital audio signals in the channel, second means for digitizing the received signals, third means for producing quadrature components of the digitized signals, fourth means for decreasing the sampling frequency of the quadrature components of the signals from the third means to a frequency related to the rate at which the digital audio signals are provided, and fifth means responsive to the quadrature digital signals from the fourth means for operating upon the first and second means to facilitate the regulation of the sampling frequency of the signals by the fourth means at the frequency related to the rate at which the digital audio signals are provided.
Claim 19
Dependent Claim
52 words
In a combination as set forth in claim 18 wherein the fifth means includes sixth means responsive to the signals from the fourth means for feeding signals back to the second means to regulate the operation of the second means in obtaining the digitizing of the received signals at a particular frequency.
Claim 20
Dependent Claim
57 words
In a combination as set forth in claim 20 wherein the fifth means includes sixth means responsive to the signals from the fourth means for feeding signals back to the third means to regulate the operation of the third means in producing the quadrature components of the signals from the third means at a particular sampling frequency.
Claim 21
Dependent Claim
52 words
In a combination as set forth in claim 20 wherein the fifth means includes seventh means responsive to the signals from the fourth means for feeding signals back to the second means to regulate the operation of the second means in obtaining the digitizing of the received signals at the particular frequency.
Claim 22
Dependent Claim
58 words
In a combination as set forth in claim 21 wherein the seventh means includes eighth means for converting the digitized signals to analog signals and includes a voltage controlled oscillator responsive to the analog signals from the eighth means for producing signals at the particular frequency to obtain the digitizing of the received signals at the particular frequency.
Claim 23
Dependent Claim
30 words
In a combination as set forth in claim 18, sixth means for regulating the gain of the received signals before the digitizing of the received signals by the second means.
Claim 24
Dependent Claim
82 words
In a combination as set forth in claim 21, including, eighth means responsive to the signals from the fourth means for providing a programmed gain of such signals in accordance with the range of amplitudes of the analog video signals superimposed with the plurality of the digital audio signals in the channel, and ninth means responsive to the signals from the eighth means for regulating the gain of the received signals before the digitizing of the received signals by the second means.
Claim 25
Dependent Claim
159 words
In combination in a direct broadcast system having a plurality of channels each with a particular range of frequencies and with an analog video signal occupying a portion of the range of frequencies in the channel and with a plurality of digital audio signals occupying the remainder of the range of frequencies in the channel to select a particular one of the digital audio signals, first means for receiving the analog video signals and the digital audio signals, second means for digitizing the received signals, third means for producing quadrature components of the digitized signals from the second means, fourth means for decreasing the sampling frequency of the signals from the third means to the frequency of the particular one of digital audio signals in the channel, and fifth means responsive to the signals from the fourth means for operating upon the second and third means to facilitate the recovery of the audio signals in the particular audio channel.
Claim 26
Dependent Claim
44 words
In a combination as set forth in claim 25 wherein the fifth means includes a servo feedback loop responsive to the signals from the fourth means for operating upon the second means to obtain the digitizing of the received signals at a particular frequency.
Claim 27
Dependent Claim
34 words
In a combination as set forth in claim 25 wherein the fifth means includes a servo feedback loop responsive to the signals from the fourth means for producing trigonometric signals at a particular frequency.
Claim 28
Dependent Claim
54 words
In a combination as set forth in claim 27 wherein the servo loop is a first servo loop and wherein the fifth means includes a second servo loop responsive to the signals from the fourth means for operating upon the second means to obtain the digitizing of the received signals at the particular frequency.
Claim 29
Dependent Claim
62 words
In a combination as set forth in claim 25, sixth means for providing the received signals with a programmed gain control before the digitizing of the received signals, the programmed gain control being dependent upon the range of amplitudes of the analog video signal and upon the modulations of these amplitudes by the plurality of the digital audio signals in the channel.
Claim 30
Dependent Claim
89 words
In a combination as set forth in claim 28, sixth means operative upon the signals from the fourth means for providing these signals with a programmed gain control dependent upon the range of amplitudes of the analog video signals and upon the modulations of these amplitudes by the plurality of the digital audio signals in the channel, and a third servo loop responsive to the signals from the sixth means for regulating the gain of the received signals before the digitizing of the received signals by the second means.
Claim 31
Dependent Claim
70 words
In a combination as set forth in claim 1, the second means including fifth means for reducing the frequency of the digital processing from that provided by the second means, and the third means being responsive to the signals from the fifth means for controlling the operation of the second means to maintain the digital processing of the analog video signals and the digital audio signals at the particular frequency.
Claim 32
Dependent Claim
54 words
In a combination as set forth in claim 4, ninth means responsive to the quadrature components of the digital signals at the reduced sampling frequency for regulating the operation of the sixth means in demodulating the signals at the particular frequency to produce the quadrature components of the digital signals at the particular frequency.
Claim 33
Dependent Claim
133 words
In a combination as set forth in claim 32, the seventh means including tenth means for reducing the sampling frequency of the quadrature components of the digital signals from the particular frequency and including eleventh means for combining the quadrature components of the digital signals at the reduced frequency and including twelfth means for further reducing the frequency of the combined signal from the eleventh means and further including thirteenth means for reconstructing the quadrature components of the digital signals at the further reduced frequency, and the ninth means being responsive to the quadrature components of the digital signals at the further reduced frequency for regulating the operation of the sixth means in demodulating the signals at the particular frequency to produce the quadrature components of the digital signals at the particular frequency.
Claim 34
Dependent Claim
152 words
In a combination as set forth in claim 18, the fourth means including sixth means for decreasing the sampling frequency of the quadrature components of the digital signals from the third means and including seventh means responsive to the quadrature components of the signals at the decreased frequency for combining such signals and including eighth means for further decreasing the frequency of the combined signals from the seventh means and including ninth means responsive to the combined signals from the eighth means for reconstituting the quadrature components of the digital signals at the further decreased frequency, and the fifth means being responsive to the quadrature components of the digital signals from the ninth means for operating upon the first and second means to facilitate the regulation of the sampling frequency of the signals by the fourth means at the frequency related to the rate at which the digital audio signals are provided.
Claim 35
Dependent Claim
51 words
In a combination as set forth in claim 33, the fifth means including tenth means responsive to the signals from the ninth means for feeding signals back to the second means to regulate the operation of the second means in obtaining the digitizing of the received signals at a particular frequency.
Claim 36
Dependent Claim
152 words
In a combination as set forth in claim 25, the fourth means including sixth means for decreasing the sampling frequency of the quadrature components of the digital signals from the third means and including seventh means responsive to the quadrature components of the signals at the decreased frequency for combining such signals and including eighth means for further decreasing the frequency of the combined signals from the seventh means and including ninth means responsive to the combined signals from the eighth means for reconstituting the quadrature components of the digital signals at the further decreased frequency, and the fifth means being responsive to the quadrature components of the digital signals from the ninth means for operating upon the first and second means to facilitate the regulation of the sampling frequency of the signals by the fourth means at the frequency related to the rate at which the digital audio signals are provided.
References Cited (Backward Citations)
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