VOICE TRANSMISSION AND RECEIVING SYSTEM EMPLOYING PULSE DURATION MODULATIONS WITH A SUPPRESSED CLOCK

• US 3,667,046 A
• Filed: 10/09/1969
• Issued: 05/30/1972
• Est. Priority Date: 10/09/1969
• Status: Expired due to Term

• Current Assignee: Magnavox Electronic Systems Company
• Original Assignee: Ralph W. Schoolcraft
• Inventors: Schoolcraft, Ralph W.
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Mayer, Albert J.
• Application Number:
  US04/865,145
• Time in Patent Office: 964 Days
• Field of Search: 179/15AB,15MM 178/67,68 325/30,38,142,152,163,320,321,322,324,58,47,164 328/58 329/106 332/9,14,15 307/265 340/347DD,347AD,206
• US Class Current: 375/308
• CPC Class Codes: H04B 14/02 characterised by the use of pulse modulation in radio transmission relays H04B7/17
• CPC Class Codes: H04B 14/026 using pulse time characteristics modulation, e.g. width, position, interval

Abstract

A voice transmission system including coded voice information using pulse duration modulation (PDM) with a suppressed clock and wherein this suppressed clock pulse duration modulated voice signal is used to modulate a phase shift keying modulator (PSK). The receiver includes a phase shift keying demodulator which feeds a limiter having a wide bandwidth so as to achieve the highest possible processing gain. The receiver also includes a voltage controlled oscillator which is fed an error signal derived from an integrator so as to produce an output signal from the voltage controlled oscillator to replace the suppressed clock.

Claims

1. A system for coding analog information, including first means responsive to the analog information for producing a clocked pulse amplitude modulated (PAM) signal representative of the analog information, second means coupled to the first means and responsive to the clocked PAM signal for producing a clocked pulse duration modulated (PDM) signal representative of the clocked PAM signal, and third means coupled to the second means and responsive to the clocked PDM signal for suppressing the clock to produce a suppressed clock PDM signal representative of the clocked PDM signal.

2. The system of claim 1 further including fourth means coupled to the third means and responsive to the suppressed clock PDM signal for producing a phase shift keying (PSK) modulated signal representative of the suppressed clock PDM signal.

3. The system of claim 1 wherein the analog information undergoes speech conditioning including pre-emphasis and compression.

4. The system of decoding a suppressed clock, pulse duration modulated (PDM) signal representative of analog information, including first means responsive to the suppressed clock PDM signal for inserting a clock signal to produce a clocked PDM signal representative of the suppressed clock PDM signal, second means coupled to the first means and responsive to the clocked PDM signal for producing a clocked pulse amplitude modulated (PAM) signal representative of the clocked PDM signal, and third means coupled to the second means and responsive to the clocked PAM signal for producing an analog signal representative of the clocked PAM signal.

5. The system of claim 4 wherein the clock signal is produced by a voltage controlled oscillator (VCO) and wherein the VCO is controlled by an error signal and wherein the error signal is produced by integrating the output signal from the first means.

6. The system of claim 4 wherein the suppressed clock PDM signal is coupled through a wideband limiter and wherein the limiter has a bandwidth of a value wherein the jitter noise and the cross-over noise of the suppressed clock PDM signal are approximately equal.

7. A communications system for transmitting an output signal containing coded information representative of analog information, including first means responsive to the analog information for periodically sampling the analog information at a fixed rate and for providing a first pulse signal from the first means having amplitude values in accordance with the periodically sampled amplitude values of the analog information, second means coupled to the first means and responsive to the first pulse signal for producing a second pulse signal having pulsewidths in accordance with the amplitude value of the pulses in the first pulse signal and with the leading edges of the pulses in the second pulse signal occurring in response to the leading edges of the corresponding pulses in the first pulse signal and with the trailing edges of the pulses in the second pulse signal occurring in response to the amplitude of the corresponding pulses in the first pulse signal;

and third means coupled to the second means and responsive to the second pulse signal for producing a third pulse signal having pulses with leading and trailing edges occurring in response to the trailing edges in the pulses in the second pulse signal.

8. The communications system of claim 7 additionally including fourth means coupled to the third means and responsive to the third pulse signal for producing an oscillator signal having its phase shifted upon the occurrence of the leading and trailing edges of the pulses in the third pulse signal.

9. The communications system of claim 7 including speech conditioning of the analog information and wherein the speech conditioning includes pre-emphasis and compression.

10. A communications system for receiving a suppressed clock pulse duration modulated (PDM) signal containing coded information representative of analog information, including first means for producing a clock signal having periodic changes in state, second means coupled to the first means and responsive to the suppressed clock PDM signal for producing a first pulse signal and with the leading edges of the pulses in the first pulse signal occurring in response to a change in state of the clock signAl and with the trailing edge of the pulses in the first pulse signal occurring in response to a change in state of the suppressed clock PDM signal, third means coupled to the second means and responsive to the first pulse signal for producing a second pulse signal having pulse amplitudes in accordance with the pulsewidths of the first pulse signal, and fourth means coupled to the third means for producing an analog signal having amplitude values in accordance with the amplitudes of the pulses in the second pulse signal.

11. The communications system of claim 10 wherein the first means for producing the clock signal includes a voltage controlled oscillator controlled by an error signal produced by integrating the output signal from the second means.

12. The communications system of claim 10 wherein the suppressed clock PDM signal is coupled through a limiter and wherein the limiter has a bandwidth of a value wherein the jitter noise and the cross-over noise of the suppressed clock PDM signal are approximately equal.

13. A system for coding and decoding analog information, including first means responsive to the analog information for producing a clocked pulse amplitude modulated (PAM) signal representative of the analog information, second means coupled to the first means and responsive to the clocked PAM signal for producing a clocked pulse duration modulated (PDM) signal representative of the clocked PAM signal, third means coupled to the second means and responsive to the clocked PDM signal for suppressing the clock to produce a suppressed clock PDM signal representative of the clocked PDM signal and for transmitting such suppressed clock PDM signal, fourth means for receiving the suppressed clock PDM signal and for inserting a clock signal to produce a clocked PDM signal representative of the suppressed clock PDM signal, fifth means coupled to the fourth means and responsive to the clocked PDM signal for producing a clocked pulse amplitude modulated (PAM) signal representative of the clocked PDM signal, and sixth means coupled to the fifth means and responsive to the clocked PAM signal for producing an analog signal representative of the clocked PAM signal.

14. The system of claim 13 further including seventh means coupled to the third means and responsive to the suppressed clock PDM signal for producing a phase shift keying (PSK) modulated signal representative of the suppressed clock PDM signal, and eighth means coupled to the fourth means and responsive to the PSK modulated signal for producing a suppressed clock PDM signal representative of the PSK modulated signal and for coupling the suppressed clock PDM signal to the fourth means.

15. The system of claim 13 wherein the clock signal is produced by a voltage controlled oscillator (VCO) and wherein the VCO is controlled by an error signal and wherein the error signal is produced by integrating the output signal from the fourth means.

16. The system of claim 13 wherein the suppressed clock PDM signal is coupled through a wideband limiter and wherein the limiter has a bandwidth of a value wherein the jitter noise and the cross-over noise of the suppressed clock PDM signal are approximately equal.