Data transmitting systems

• US 4,066,841 A
• Filed: 09/24/1976
• Issued: 01/03/1978
• Est. Priority Date: 01/25/1974
• Status: Expired due to Term

• Current Assignee: Serck Industries Ltd. (Schneider Electric SE)
• Original Assignee: Serck Industries Ltd. (Schneider Electric SE)
• Inventors: Young, Robert Eric
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US05/726,323
• Time in Patent Office: 466 Days
• Field of Search: 325/30, 325/163, 178/66 R, 178/66 A, 178/69 R, 178/69 D, 328/163
• US Class Current: 375/276
• CPC Class Codes: H04L 27/10 Frequency-modulated carrier systems, i.e. using frequency-shift keying H04L27/32 takes precedence

Abstract

It is important that a data transmission system should be fast, utilize a minimum of band width and be accurate in the presence of high noise levels. The invention provides a frequency shift keying data transmission system for transmission of binary coded information in which the mark of the coded pulse waveform is represented by a half cycle of one keying frequency and the space is represented by a half cycle of another keying frequency. An improvement in speed, band width utilization and accuracy at high noise levels is obtained by providing that the transmission signal is an approximately sinusoidal waveform of which the phase is continuous at the transitions, the time lengths of the mark and space symbols thereof are matched to the half time periods of the respective keying frequencies and the slope is constant at the cross-over points.

Claims

1. In a frequency shift keying data transmission system for transmission of information in a binary coded pulse waveform in which the mark of the binary coded pulse waveform is represented by a half cycle of a first keying frequency and the space is represented by a half cycle of a second keying frequency, the improvement comprising:

means for the generation of a signal of an approximately sinusoidal waveform having a phase continuous at the transitions of said sinusoidal waveform and wherein the time lengths of the mark and space symbols thereof are matched to the half time periods of the respective keying frequencies and the slope of said approximately sinusoidal waveform is constant at the cross-over points, and means for measuring the time duration between the crossover points of the binary coded pulse waveform signal and comparing the time duration with a reference to determine whether the duration corresponds with that of the shorter half time of the higher keying frequency or that of the longer half time period of the lower keying frequency, wherein said means for measuring and comparing includes a source of clock pulses, a counter connected to said source of clock pulses, means responsive to the beginning of a half cycle of binary coded pulse waveform signal for starting the counter, means responsive to the end of a half cycle of received signal for stopping the counter, and comparator means for determining whether the count of clock pulses during each enabled period is greater or less than a predetermined count corresponding to a time duration greater than the half time of the higher frequency and less than the half time of the lower frequency.

2. In a frequency shift keying data transmission system for transmission of information in a binary coded pulse waveform in which the mark of the binary coded pulse waveform is represented by a half cycle of a first keying frequency and the space is represented by a half cycle of a second keying frequency, the improvement comprising:

means for the transmission of a signal of an approximately sinusoidal waveform having a phase continuous at the transitions of the sinusoidal waveform and wherein the time lengths of the mark and space symbols thereof are matched to the half time periods of the respective keying frequencies and the slope of said sinusoidal waveform is constant at the cross-over points;

means for storing said binary coded pulse waveform, means for converting the binary coded pulse waveform into a matched waveform in which the time lengths of the mark and space symbols thereof are matched to the half time periods of the respective keying frequencies, filter means coupled to said converting means producing, from the matched waveform, said approximate sinusoidal waveform;

said storage means being a data register having an input to which the binary coded pulse waveform is fed, and an output;

clock means coupled to said data register such that the coded waveform is fed under the control of pulses from said clock means one bit at a time to a first shift register and, additionally, through an inverter to a second shift register, wherein the number of stages in the first and second shift registers have the same relationship to each other as the relationship between the first and second keying frequencies;

said clock means generating pulses for shifting each bit of the coded waveform through the first and second registers to an OR gate, the outputs of which are the coded information converted to a rectangular waveform in which the time lengths of the mark and space symbols thereof are matched to the half time periods of the respective keying frequencies.

3. In a frequency shift keying data transmission system for transmission of information in a binary coded pulse waveform in which the mark of the binary coded pulse waveform is represented by a half cycle of a first keying frequency and the space is represented by a half cycle of a second keying frequency, the improvement comprising:

means for the transmission of a signal of an approximately sinusoidal waveform having the phase continuous at the transitions of the sinusoidal waveform and wherein the time lengths of the mark and space symbols thereof are matched to the half time periods of the respective keying frequencies and the slope of said sinusoidal waveform is constant at the cross-over points;

means for measuring the time duration between the cross-over points of the binary coded pulse waveform signal and comparing the time duration with a reference to determine whether the duration corresponds with that of the shorter half time of the higher keying frequency or that of the longer half time period of the lower keying frequency;

clock means generating pulses are fed to a binary counter during the time interval of each half cycle, and the count obtained from said counter transferred to a first shift register, a second shift register containing a reference count, and comparator means coupled to said first and second shift registers to determine whether the count in said first shift register is greater than, less than, or equal to the reference count in the second shift register.

4. A data transmission system as claimed in claim 3, wherein the first and second shift registers are of the parallel in/serial out type.

5. A data transmission system as claimed in claim 3, wherein the first and second shift registers are of the parallel in /parallel out type.

6. In a frequency shift keying data transmission system for transmission of information in a binary coded pulse waveform in which the mark of the binary coded pulse waveform is represented by a half cycle of a first keying frequency and the space is represented by a half cycle of a second keying frequency, the improvement comprising:

means for the transmission of a signal of an approximately sinusoidal waveform having a phase continuous at the transitions of the sinusoidal waveform and wherein the time lengths of the mark and space symbols thereof are matched to the half time periods of the respective keying frequencies and the slope of said sinusoidal waveform is constant at the cross-over points;

means for storing said binary coded pulse waveform, means for converting the binary coded pulse waveform into a matched waveform in which the time lengths of the mark and space symbols thereof are matched to the half time periods of the respective keying frequencies, filter means coupled to said converting means producing, from the matched waveform, said approximate sinusoidal waveform, said storage means comprising a data register having an input to which the binary coded pulse waveform is fed and an output;

clock means coupled to said data register such that the binary coded pulse waveform is fed from said data register under the control of pulses from said clock means;

a shift register having an input and a plurality of stages of which at least two stages provide respective outputs, means for actuating one of the outputs when the binary coded bit is a mark and for actuating another of the outputs when the binary coded bit is a space, means for feeding clock pulses to the input of the shift register at the commencement of a mark or space bit and means for receiving the output of the actuating means and producing a rectangular wave output in which the time lengths of the mark and space symbols thereof are matched to the half time periods of the respective keying frequencies.