Transmitter-receiver system utilizing pulse position modulation and pulse compression

• US 4,206,316 A
• Filed: 01/08/1979
• Issued: 06/03/1980
• Est. Priority Date: 05/24/1976
• Status: Expired due to Term

• Current Assignee: Hughes Aircraft Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Bancroft, Charles F., Burnsweig, Joseph
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Masinick, Michael A.
• Application Number:
  US06/001,982
• Time in Patent Office: 512 Days
• Field of Search: 325/138, 325/139, 325/156, 325/157, 325/142, 325/143, 325/126-130, 325/321, 325/324, 179/15 A, 179/15 AW, 358/13, 358/141, 358/263, 178/68, 330/207 A
• US Class Current: 178/66.1
• CPC Class Codes: H04B 14/026 using pulse time characteristics modulation, e.g. width, position, interval
• CPC Class Codes: H04N 7/00 Television systems details H04N3/00, H04N5/00; methods or arrangements, for coding, decoding, compressing or decompressing digital video signals H04N19/00; selective content distribution H04N21/00

Abstract

Transmitter are receiver systems are disclosed including an encoder and a decorder, respectively. The encoder samples an incoming analog video signal and operates a periodic bipolar pulse pair whose phase separation is proportional to the amplitudes of the sampled data, thus pulse position modulation (PPM). In one embodiment of the invention the coded in-phase pulses are applied to a first channel having an intermediate frequency (IF) dispersive delay line with a positive-sloped transfer function. The out-of-phase pulses are applied to a second channel having a dispersive delay line with a negative-sloped, or conjugate, transfer function. The two channels of positive and negative dispersed pulses are added together resulting in a complex IF waveform. The complex IF waveform is frequency translated to a suitable time varying DC voltage waveform for controlling a transmitter. The receiver system includes a decoder having first and second channels with respective first and second conjugate pulse compression lines or chirp filters for recovering the original bipolar coded data. The first pulse compression line, with a negative-shaped transfer function recovers the in-phase PPM pulses of the bipolar pulse pair. The second pulse compression line, having the conjungate slope, recovers the out-of-phase PPM of the bipolar pulse pair pulses. The PPM pulses in the first and second channels are translated into pulse-width modulated pulses which are then demodulated. The demodulated pulses are subtracted and the original data is recovered while at the same time the sampling frequency is filtered out.

Claims

1. In a transmitter and receiver system for transmission and reception of coded signals utilizing pulse position modulation with zero beats between the carrier and the modulation, said receiver having a decoder, an encoder in said transmitter, comprising:

a source of a reference frequency signal forming the carrier frequency with negative and positive half cycles;

input means for providing first and second push-pull analog input signals to first and second channels, respectively, said first and second analog signals being 180 degrees out of phase with each other;

first modulation means in said first channel and responsive to said source for sampling said first analog signal and providing a first pulse position modulated pulse in response to said first input signal during each negative half cycle;

second modulation means in said second channel and responsive to said source for sampling said first analog signal and providing a second pulse position modulated pulse in response to said second input signal during each positive half cycle; and

combining means coupled to said first and second modulation means for combining during each cycle, said first and second pulse position modulated pulses into bipolar pulse pairs, each pair having a separation proportional to the sampled amplitude.

2. In a transmitter and receiver system according to claim 1, further comprising:

first dispersive delay means coupled between said first modulation means and said combining means, said first dispersive delay means having a first transfer function with a first slope for providing dispersed pulses in response to said first modulation means; and

second dispersive delay means coupled between said second modulation means and said combining means, said second dispersive delay means having a second transfer function being the conjugate of said first transfer function for providing dispersed pulses in response to said pulses from said second modulation means.

3. In a transmitter and receiver system according to claim 1, said decoder comprising:

pulse detecting means for detecting said first and second pulses of said pairs of pulses;

first pulse width modulation means coupled to said pulse detecting means, said first pulse width modulation means being responsive to said first pulse position modulated pulses and providing output pulses having widths determined by said first pulses;

second pulse width modulation means coupled to said pulse detecting means, said second pulse width modulation means being responsive to said second pulse position modulated pulses and providing output pulses having widths determined by said second pulses; and

coupling means responsive to said first and second pulse width modulation means for providing an analog output signal to a utilization circuit.

4. In a transmitter and receiver system according to claim 1, the combination comprising:

in said encoder, a first dispersive delay line coupled to said first modulation means for providing a first dispersed signal to said combining means; and

a second dispersive delay line coupled to said second modulator means for providing a second dispersed signal to said combining means, said second dispersive delay line having a transfer function being the conjugate of the transfer function of said first dispersive delay line;

and in said decoder, first pulse compression means responsive to said first dispersed signals, said first pulse compression means having a transfer function being the conjugate of the transfer function of said first dispersive delay line;

second pulse compression means responsive to said second dispersed signals, said second pulse compression means having a transfer function being the conjugate of the first transfer function of said second dispersive delay line;

first and second pulse detecting means coupled to said first and second pulse compression means, respectively, for detecting first and second pulses of said pairs of pulses; and

first and second pulse width modulation means coupled to said first and second pulse detecting means, respectively, said pulse width modulation means being responsive to said pairs of pulses and providing output pulses having widths determined by the time offset within each of said pairs of pulses.

5. In a transmitter and receiver system for transmission and reception of pulse position modulated signals with said transmitter having an encoder, a decoder in said receiver comprising:

pulse detecting means for detecting first and second pulses of pulse pairs, said first and second pulses being pulse position modulated in a coded manner;

pulse separator means coupled to said pulse detecting means for separating said first pulses into a first channel and said second pulses into a second channel;

first pulse width modulation means coupled to said pulse separator means, said first pulse width modulation means being responsive to said first and second pulses and providing a first pulse width modulated signal on a first channel;

second pulse width modulation means coupled to said pulse separator means, said second pulse width modulation means being responsive to said first and second pulses and providing a second pulse width modulated signal on a second channel;

demodulating means coupled to said first and second pulse width modulation means for demodulating said first and second pulse width modulated signals to respectively provide first and second analog signals each including a beat signal; and

combining means coupled to said demodulating means for combining said first and second analog signals to cancel said beat signals and provide an output analog signal.

6. A decoder responsive to frequency dispersed PPM first and second pulses of a pair of pulses defining a code and provided by an encoder, comprising:

pulse compression means responsive to said first and second pulses, said pulse compression means having a first transfer function for said first pulses and having a second transfer function for said second pulses;

pulse detecting means coupled to said pulse compression means for detecting first and second pulses of said pair of pulses; and

pulse width modulation means coupled to said pulse detecting means for providing pulse width modulated pulses in response to said first and second pulse position modulated pulse pair; and

combining means responsive to said pulse width modulation means for providing an analog signal in response to said pulse width modulated pulses.

7. In the decoder according to claim 6, said pulse compression means comprising:

a first pulse compression line responsive to said first pulses of said pairs of pulses, having said first transfer function with a predetermined slope; and

a second pulse compression line being responsive to said second pulses of said pairs of pulses, having said second transfer function with a slope being the conjugate of said first slope.

8. In a transmitter and receiver system for transmission and reception of coded signals with said receiver having a decoder, an encoder in said transmitter comprising:

input means for receiving a time-varying signal;

first means responsive to said input means for providing first and second signals being out of phase with each other;

pulse generating means coupled to said first means for providing pairs of pulse position modulated pulses in response to the amplitude of said first and second signals at a preselected sampling frequency;

dispersive delay means coupled to said pulse generating means for providing a first dispersed signal having a first slope in response to said first pulses of said pairs of pulses and for providing a second dispersed signal having a second slope in response to said second pulses of said pairs of pulses, said first and second slopes being conjugate; and

combining means coupled to said dispersive delay means for combining said first and second dispersed signals.

9. An encoder for use in a transmission-reception system providing pulse-position modulated pulses, comprising:

phase-splitter means for receiving an analog-input signal and providing first and second analog signals out of phase with each other to first and second channels, respectively;

first current generator means in said first channel for receiving said first analog signal and generating a current signal proportional thereto;

first pulse-width multivibrator means coupled to said first current generator means for providing a pulse having a pulse-width in proportion to the current generated by said current generator means;

first pulse-position multivibrator means coupled to said first pulse-width multivibrator means for generating pulses having a predetermined pulse width and being pulse-position modulated in response to the width of the pulses from said first pulse-width multivibrator means;

second current generator means in said second channel for receiving said second analog signal from said phase-splitter means and providing a current signal proportional thereto;

second pulse-width multivibrator means coupled to said second current generator means for providing pulse-width modulated pulses in response to current signals from said second current generator means; and

second pulse-position multivibrator means coupled to said second pulse-width multivibrator means for generating pulse-position modulated pulses having a predetermined pulse width in response to the pulse-width modulated pulses from said second pulse-width multivibrator means.

10. The invention, according to claim 9, further comprising:

combiner means for combining said pulse-position modulated pulses from said first pulse-position multivibrator means in said first channel and said pulse-position modulated pulses from said second pulse-position multivibrator means in said second channel and providing a single channel of bipolar pulse-position modulated pulses.

11. The invention, according to claim 10, comprising:

bandpass filter means coupled to said combiner means for providing a sine-wave output signal having positive-negative half-cycles being modulated in response to said bipolar pulse-position modulated pulses.

12. The invention, according to claim 9, comprising:

reference generator means for providing a control signal to said first and second current generator means for sampling said respective first and second analog signals at a predetermined frequency.

13. An encoder for use in a transmitter-receiver system utilizing pulse-position modulated pulses, comprising:

phase-splitter means for receiving an analog signal and providing first and second analog signals out of phase with each other;

first energy storage means for storing energy;

first current-generator means coupled to said energy storage means for charging said first energy storage means;

first discharge means coupled to said first energy storage means for discharging said stored energy in response to a first control signal;

first adder means coupled to said first energy storage means and to said phase-splitter means for adding said first analog signals and said stored energy in said first energy storage means;

first comparator means coupled to said first adder means for providing pulse-width modulated pulses in response to said first adder means;

first multivibrator means coupled to said first comparator means for providing first pulse-position modulated pulses in response to said first comparator means;

second energy storage means for storing energy;

second current generator means coupled to said second energy storage means for charging said second energy storage means;

second discharge means coupled to said second energy storage means for discharging said stored energy in response to a second control signal being out of phase with said first control signal;

second adder means coupled to said second energy storage means and to said phase-splitter means for adding said second analog signals and said stored energy in said second energy storage means;

second comparator means coupled to said second adder means for providing pulse-width modulated pulses in response to said second adder means; and

second multivibrator means coupled to said second comparator means for providing second pulse position modulated pulses in response to said second comparator means.

14. An encoder for generating dual bipolar pulse-position modulated pulses for use in a transmitter-receiver system, comprising:

first phase-splitter means for receiving an analog input signal and providing first and second analog signals to first and second channels respectively, said first and second signals being out of phase with each other;

said first channel including second phase-splitter means for receiving said first analog signal and providing third and fourth analog signals being out of phase with each other;

first modulator means coupled to said second phase-splitter means for receiving said third and fourth signals and providing first pairs of pulse-position modulated pulses;

third phase-splitter means coupled to said first phase-splitter means for receiving said second analog signal and providing fifth and sixth analog signals being out of phase with each other;

second modulator means coupled to third phase splitter means for receiving said fifth and sixth analog signals and providing second pairs of pulse-position modulated pulses; and

combiner means coupled to said first and second modulator means for providing dual bipolar pulse-position modulated pulse pairs.

15. An encoder for use in a transmission-reception system, comprising;

phase-splitter means for responding to an input analog signal and providing first and second analog signals being out of phase with each other;

first pulse position modulator means coupled to said phase-splitter means for providing first pulse-position modulated pulses at a predetermined frequency in response to said first analog signal;

first impulse driver means coupled to said first pulse position modulator means for providing first impulse signals in response to said first pulses;

first dispersive delay means coupled to said first impulse driver means for providing a frequency dispersed signal having a first slope, in response to said first impulse signal;

second pulse position modulator means coupled to said phase-splitter means for providing second pulse-position modulated pulses at a predetermined frequency in response to said second analog signal;

second impulse driver means coupled to said second pulse position modulator means for providing second impulse signals in response to said second pulses;

second dispersive delay means coupled to said second impulse driver means for providing a frequency dispersed signal having a slope being the conjugate of said first slope; and

combiner means coupled to said first and second dispersive delay means for combining said frequency dispersed signals and providing a single channel output signal.

16. A decoder for use in a transmission-reception system providing pulse-position modulated pulses, comprising:

discriminator means for detecting first and second pulses of bipolar pulse-position modulated signals;

pulse separator means coupled to said discriminator means for providing said first pulses on a first channel and for providing said second pulses on a second channel;

flip-flop means coupled to said pulse separator means for providing first and second pulse-width modulated signals in response to said first and second pulses;

first demodulator means coupled to said flip-flop means for demodulating said first pulse-width modulated signals;

second demodulator means coupled to said flip-flop means for demodulating said second pulse-width modulated signals; and

adder means coupled to said first and second demodulator means for providing a single channel analog signal.

17. A decoder responsive to the encoder of claim 16 comprising:

first and second pulse compression means for receiving a frequency dispersed pulse-position modulated signal, said first compression means for compressing a frequency dispersed signal having a first slope, said second pulse compressions means for compressing a frequency dispersed signal having a conjugate slope, said first and second pulse compression means being responsive to said output signal provided by said combiner means.

18. A decoder for use in a transmission-reception system for providing pulse position modulated pulses, comprising:

pulse separator means for providing first pulse position modulated signals on a first channel and second pulse position modulated signals on a second channel;

first flip-flop means coupled to said pulse separator means for providing first and second pulse-width modulated signals in response to said first pulse-position modulated signals;

first and second pulse-width demodulator means coupled to said first flip-flop means for demodulating said first and second pulse-width modulated signals respectively;

first adder means coupled to first and second demodulator means for providing a first analog signal on a first channel;

second flip-flop means coupled to said pulse separator means for providing third and fourth pulse-width modulated signals in response to said second pulse-position modulated signals;

third and fourth pulse-width demodulator means coupled to said second flip-flop means for demodulating said third and fourth pulse-width modulated signals respectively;

second adder means coupled to said third and fourth pulse-width demodulator means for providing an analog signal on a single channel, and

third adder means coupled to first and second adder means for providing a single analog signal.

19. In a transmitter and receiver system for transmission and receiption of coded signal modulations utilizing pulse position modulation and for cancelling the beat frequency signals between a modulation frequency and a carrier frequency, an encoder and decoder comprising:

a source of push-pull analog input signals;

a source of reference signals cycling at the carrier frequency with negative and positive half cycles;

means coupled to said source of input signals and to said source of reference signals for deriving first and second push-pull pulse position modulated pulses during respective negative and positive half cycles of said reference signals;

means for responding to said first and second push-pull pulses and to respectively derive third and fourth push-pull pulse position modulated pulses therefrom; and

means responsive to said third and fourth pulses including combining means for providing coded signal modulations and for cancelling said beat frequency signals.