Audio communication band image transceiver
First Claim
1. A method of converting an analog image signal of slow-scan television (SSTV) format to a digital image signal, said method comprising steps of:
- providing an input level controller;
using said input level controller to receive said analog image signal of SSTV format and to responsively provide an output analog SSTV image signal within a selected range;
providing an analog-to-digital (A/D) signal converter;
using said A/D signal converter to receive said output analog SSTV image signal and to responsively provide said digital image signal;
providing a Hilbert filter; and
supplying said digital image signal to said Hilbert filter to provide a phase-shifted digital signal.
1 Assignment
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Accused Products
Abstract
A still video image transceiver for use across narrow-band analog voice communication channels allows still video images captured or provided by a wide variety of consumer and industrial image sources, even those of the common hetrodyne-signal type, to be transmitted over a voice communication channel, such as over a telephone line or by high frequency radio communication. The captured video image is converted to an audio band signal using a digital linear signal processing method which avoids the common problem of first having to separate the image signal of its RGB color signal components. Use of a time-base corrector is avoided, while a jitter-free image for the receiver of the image is obtained even for those images which originate with asynchronous hetrodyne-type image source. Even over analog voice communication channels of marginal operating condition, an excellent signal to noise ratio is achieved because a limiter circuit is not used prior to demodulation of the received image signal. Also, a digital linear signal decoding method is used for superior results.
71 Citations
19 Claims
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1. A method of converting an analog image signal of slow-scan television (SSTV) format to a digital image signal, said method comprising steps of:
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providing an input level controller; using said input level controller to receive said analog image signal of SSTV format and to responsively provide an output analog SSTV image signal within a selected range; providing an analog-to-digital (A/D) signal converter; using said A/D signal converter to receive said output analog SSTV image signal and to responsively provide said digital image signal; providing a Hilbert filter; and supplying said digital image signal to said Hilbert filter to provide a phase-shifted digital signal.
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2. A method of converting an analog image signal of slow-scan television (SSTV) format to a video image signal, said method comprising steps of:
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providing an analog-to-digital (A/D) converter; supplying the analog SSTV signal to said A/D converter to provide a digitized SSTV image signal; providing a Hilbert filter; supplying said digitized SSTV image signal to said Hilbert filter to effect a phase-shift Hilbert transform of said digitized SSTV signal providing a phase-shifted SSTV signal having a certain time delay; providing a delay unit having a delay interval substantially equal to said certain time delay; supplying said digitized SSTV image signal to said delay unit to provide a time-delayed SSTV signal; and detecting the phase difference corresponding with the angular frequency of said slow-scan TV signal according to the arctangent between said phase-shifted SSTV signal and said time-delayed SSTV signal. - View Dependent Claims (3)
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4. A method of converting an analog composite video image signal to SSTV format for transmission over a narrow band-width analog communication channel, said method comprising steps of:
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providing an analog-to-digital (A/D) converter; supplying said analog composite video image signal to said A/D converter to provide a digital composite video image signal; providing a band pass filter; supplying said digital composite video image signal to said band pass filter to provide a chroma signal; providing a first delay unit of the finite-process-time type having a process time substantially equal to said band pass filter; supplying said digital composite video image signal to said first delay unit to provide a delayed digital composite video image signal; providing a Y/C separator; and supplying said chroma signal and said delayed digital composite video image signal to said Y/C separator to provide a luminescence signal. - View Dependent Claims (5, 6, 7)
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8. Transceiver apparatus for receiving an analog composite video image signal and responsively providing an analog image signal of SSTV format for transmission over a narrow band-width analog audio communication channel, and also for receiving such an analog image signal of SSTV format and responsively providing an analog composite video image signal, said apparatus comprising:
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an input level controller receiving said analog image signal of SSTV format, said input level controller including means for responsively providing an output analog SSTV image signal within a selected signal range; an anti-aliasing low-pass filter receiving said output analog SSTV image signal within a certain range, said anti-aliasing low-pass filter including means for rejecting aliasing signals therefrom and responsively providing an output analog SSTV image signal within a certain range and free of aliasing signals; further including an analog-to-digital (A/D) signal converter, switch means for routing a selected one of said composite video image signal or said analog SSTV image signal within a certain range and free of aliasing signals to said A/D converter, said A/D converter including means for receiving said analog signals and for responsively providing a respective digital version of each signal; a digital signal processor; memory means associated with said digital signal processor for storing said digital versions of said analog composite video image signal and of said analog SSTV image signal within a certain range and free of aliasing signals; wherein said digital signal processor includes; a Hilbert filter receiving said digital version of said SSTV image signal to effect a phase-shift Hilbert transform of said digitized SSTV signal, said Hilbert filter providing a digital phase-shifted SSTV signal having a certain time delay; a delay unit having a delay interval substantially equal to said certain time delay, said delay unit providing a time-delayed SSTV signal; and a phase detector for detecting the phase difference corresponding with the angular frequency of said digitized SSTV signal according to the arctangent between said phase-shifted SSTV signal and said time-delayed SSTV signal. - View Dependent Claims (9)
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10. Transceiver apparatus for receiving an analog composite video image signal and responsively providing an analog image signal of SSTV format for transmission over a narrow band-width analog audio communication channel, and also for receiving such an analog image signal of SSTV format and responsively providing an analog composite video image signal, said apparatus comprising:
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an input level controller receiving said analog image signal of SSTV format, said input level controller including means for responsively providing an output analog SSTV image signal within a selected signal range; an anti-aliasing low-pass filter receiving said output analog SSTV image signal within a certain range, said anti-aliasing low-pass filter including means for rejecting aliasing signals therefrom and responsively providing an output analog SSTV image signal within a certain range and free of aliasing signals; further including an analog-to-digital (A/D) signal converter, switch means for routing a selected one of said composite video image signal or said analog SSTV image signal within a certain range and free of aliasing signals to said A/D converter, said A/D converter including means for receiving said analog signals and for responsively providing a respective digital version of each signal; further including; a digital signal processor; memory means associated with said digital signal processor for storing said digital versions of said analog composite video image signal and of said analog SSTV image signal within a certain range and free of aliasing signals; and wherein said digital signal processor further includes; a band pass filter receiving said digital version of said composite video image signal to provide a chroma signal; a first delay unit of the finite-process-time type having a process time substantially equal to said band pass filter, said first delay unit receiving said digital version of said composite video image signal to provide a delayed digital composite video image signal; and a Y/C separator receiving said chroma signal and said delayed digital composite video image signal to provide a luminescence signal. - View Dependent Claims (11, 12, 13)
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14. Transceiver apparatus for receiving an analog image signal of SSTV format and responsively providing an analog composite video image signal, said apparatus comprising:
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an analog-to-digital (A/D) signal converter receiving said analog SSTV image signal to responsively providing a respective digital version of said signal; a digital signal processor for receiving said digital version of said SSTV image signal and responsively providing a digital version of said analog composite video image signal; memory means associated with said digital signal processor for storing said digital version of said analog SSTV image signal and said digital version of said analog composite video image signal; digital-to-analog signal converter for receiving said digital version of said analog composite video image signal and responsively providing said analog composite video image signal; wherein said digital signal processor includes; a Hilbert filter receiving said digital version of said SSTV image signal to effect a phase-shift Hilbert transform of said digitized SSTV signal, said Hilbert filter providing a digital phase-shifted SSTV signal having a certain time delay; a delay unit having a delay interval substantially equal to said certain time delay, said delay unit providing a time-delayed SSTV signal; and a phase detector for detecting the phase difference corresponding with the angular frequency of said digitized SSTV signal according to the arctangent between said phase-shifted SSTV signal and said time-delayed SSTV signal. - View Dependent Claims (15)
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16. Transceiver apparatus for receiving an analog composite video image signal and responsively providing an analog image signal of SSTV format for transmission over a narrow band-width analog audio communication channel, said apparatus comprising:
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a buffer amplifier receiving said analog composite video image signal; an analog-to-digital (A/D) signal converter receiving said analog composite video image signal to responsively provide a respective digital version of said signal; a digital signal processor receiving said digital version of said composite video image signal and responsively providing a digital version of said SSTV image signal; memory means associated with said digital signal processor for storing said digital version of said analog composite video image signal and of said SSTV image signal; a digital-to-analog signal converter for receiving said digital version of said SSTV image signal and responsively providing said analog SSTV image signal; wherein said digital signal processor includes; a band pass filter receiving said digital version of said composite video image signal to responsively provide a chroma signal; a first delay unit of the finite-process-time type having a process time substantially equal to said band pass filter, said first delay unit receiving said digital version of said composite video image signal to provide a delayed digital composite video image signal; and a Y/C separator receiving said chroma signal and said delayed digital composite video image signal to responsively provide a luminescence signal. - View Dependent Claims (17, 18, 19)
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Specification