US3579117A - Waveform generator - Google Patents

Waveform generator Download PDF

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Publication number
US3579117A
US3579117A US763301A US3579117DA US3579117A US 3579117 A US3579117 A US 3579117A US 763301 A US763301 A US 763301A US 3579117D A US3579117D A US 3579117DA US 3579117 A US3579117 A US 3579117A
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Prior art keywords
waveform
generator
output
pulse
frequency
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Expired - Lifetime
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US763301A
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English (en)
Inventor
Walter E Norris
Stephen D Shoap
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AT&T Corp
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Bell Telephone Laboratories Inc
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
    • H03K5/01—Shaping pulses

Definitions

  • a waveform generator is required which can generate a pulse having the desired waveshape to be substituted for the rectangular pulse of a digital pulse train.
  • Prior art waveform generators which utilize frequency domain shaping techniques (filtering) are physically cumbersome and have limited capabilities with respect to the waveforms which can be produced. For instance, when a null in the spectrum at a specific frequency is created by filtering, the signals in the frequencies contiguous to the specific frequency suffer from undesirable phase shift and amplitude effects.
  • An object of the present invention is to provide a waveform generator which can produce a complex function in a simple manner.
  • Another object of the present invention is to utilize time domain shaping techniques in the production of a desired waveform.
  • Another object of the present invention is to synchronize parts of a combined wave in a simple manner.
  • Another object of the present invention is to generate a pulse waveform which may be substituted for a rectangular pulse waveform in a simple manner.
  • Another object of the present invention is to generate a pulse having a waveform suitable for use in a digital transmissron system.
  • the master clock may be a square wave oscillator which is connected to plural frequency converters.
  • each frequency converter is passed through a respective waveshaper and the outputs of the waveshapers are selectively combined in accordance with predetermined 'control signals and passed through a simple filter to provide a desired waveshape.
  • Each combination of frequency converter and waveshaper forms an elementary generator.
  • the predetermined control signals may be selected to provide modulation of the desired waveshape in addition to performing the combining functions. As a feature of the present invention, significant equipment savings may be realized by joining the modulation function with the combining circuit.
  • time domain shaping techniques in accordance with the present-invention, may produce waveforms having special properties which were not readily obtainable with frequency domain shaping techniques.
  • the null unobtainable by frequency domain shaping techniques is easily obtained with the present invention by producing a modified periodic ripple signal in the time domain which, it may be shown, transfers to a null in the frequency domain.
  • one such waveform is a Sinx/x pulse. Since a Sinx/x pulse theoretically is nonvanishing over all time, its actual generation is impossible. By duration limiting the Sinx/x pulse, that is, by generating a portion of the waveform over a specified time duration, it may effectively be approximated and used with a digital transmission system.
  • an embodiment of the present invention provides a duration limited pulse which resembles the Sinx/x pulse, but has a zero average level and is used as a substitute for the rectangular pulse in digital transmission systems. By sampling this pulse at a positive portion of the waveform, the desired information may be obtained.
  • the desired duration limited pulse is derived, in an illustrative embodiment of the present invention, for use with a digital transmission system by applying the output of a square wave generator to two tandemly-connected flip-flops which serve as frequency dividers.
  • the output of each flip-flop is passed through a respective simple low-pass filter, and the outputs of the filter are selectively combined in order to provide the desired duration limited pulse.
  • embodiments of the present waveform generator may be fabricated by integrated circuitry techniques, the benefits of which are well known and significant.
  • the waveshaping devices following each flip-flop may provide some problem for integrated circuitry fabrication, but when they comprise only resistors and capacitors, integrated circuitry techniques may be used.
  • FIG. 1 is a block diagram of the generalized waveform generator arranged in accordance with the principles of the presentinvention
  • FIG. 2 is a block diagram of an illustrative embodiment of the waveform generator shown in FIG. I which is capable of producing an electrical waveform for use with a digital transmission system;
  • FIG. 3 presents a series of curves representative of electrical waveforms appearing at various points in the function generator shown in FIG. 2;
  • FIG. 4 is a more detailed block diagram of a control and combining circuit arrangement suitable for use in the waveform generator of FIGS. 1 and 2;
  • FIG. 5 presents a series of electrical waveforms appearing at portions of the control and combining circuit arrangement shown in FIG. 4.
  • FIG. 1 is a block diagram of a generalized embodiment of a waveform generator and illustrates the principles of the present invention.
  • the output of master oscillator 10 which has a frequency f is supplied to a number of frequency converters illustratively shown as 11, 12, and 13.
  • Converters ll, 12, and 13 may be multipliers or dividers or any combination thereof.
  • the outputs of frequency converters 1 1, 12, and 13 are connected to waveshapers 14, 15, and 16, respectively, the outputs of which are connected to combining circuit 17.
  • Each combination of converter and waveshaper forms an elementary generator.
  • control signal generator 18 the outputs of waveshapers 14, 15, and 16 are selectively combined in combining circuit 17 and passed through filter 19 to provide the desired waveform.
  • the operation of the waveform generator shown in FIG. '1 may be viewed as an arrangement which permits the piecing together of separately generated pieces and combining them to form a desired waveform by serially gating the outputs of the elementary generators.
  • the number of frequency converters and waveshapers required is infinite.
  • time domain shaping accomplished by the elementary generators and combining circuit must be supplemented to produce accurately the desired function.
  • filter 19 is connected to the output of combining circuit 17 to provide the necessary frequency domain shaping. Filter 19 may be simple since most of the waveshaping has been accomplished by the prior circuitry.
  • wavefonn generators generally include expensive and complex filters in order to provide a desired waveform.
  • the waveform is produced by initially using time domain shaping and subsequently frequency domain shaping in order to produce the desired waveform. This latter approach enables the waveform generator to be simply and inexpensively fabricated due to the simplicity of the elementary generators.
  • FIG. 2 is a block diagram of an illustrative embodiment of the generalized waveform shown in FIG. 1.
  • the apparatus shown in FIG. 2 produces the desired duration limited pulse for use with a digital transmission system.
  • the master oscillator is illustratively shown as master square wave generator 20 which provides a square wave output to a frequency converter, illustratively shown as flipflop 21, which frequency divides the square wave input supplied by generator 20.
  • Master generator 20 which may serve as a component in an elementary generator, supplies its output through low-pass filter 22 to amplifier 23, while the output of flip-flop 21 passes through low-pass filter 24 to amplifier 25.
  • the outputs of amplifiers 23 and 25 connect to the input of combining circuit 26, the output of which passes through low-pass filter 27.
  • Control signal generator 28 connects to combining circuit 26 and controls the selective combination process to be accomplished by the combining circuit by serially gating the outputs of amplifiers 23 and 25.
  • Frequency divider 21 represents one of a series of tandemly connected frequency dividers connected to master oscillator 20 and locked to it, enabling drift in the master oscillator to be sensed in each of the following frequency dividers.
  • the amount of drift in the following segment will be the same so that the two portions connect together without significant discontinuity.
  • FIG. 3 presents a series of waveforms appearing at various points in the function generator shown in FIG. 2.
  • the output of square wave generator 20 is illustratively shown in FIG. 3 as curve A, while the output of flip-flop 21 (which serves as a frequency divider) is shown as waveform B.
  • Waveforms A and B are passed through filters 22 and 24 respectively and amplifiers 23
  • Curve A is a square wave produced by generator 20 which is 7 frequency divided by flip-flop 21
  • an the output of flip-flop 21 is shown as curve B.
  • flip-flop 21 is shown to change its output state only in response to a positive going step and provide the desired frequency division, as shown by curves A and B.
  • a waveform having a specified shape will most efficiently serve as a substitute for a rectangular pulse in a digital pulse train.
  • the square waves provided by master generator 20 and frequency divider 21 (curves A and B, respectively) are passed through low-pass filters 22 and and 24.
  • the waveshapers may be designed to transform the square waves into waveforms which may be selectively utilized and combined with other waveforms to produce the desired composite waveshape.
  • FIG. 4 is a more detailed block diagram of an embodiment of control signal generator 28 and combining circuit 26 which, in accordance with the present invention, produce the desired waveform.
  • the block diagram shown in FIG. 4 is merely illustrative of one of many arrangements which perform the desired combining function.
  • master generator 20 Since the control signal generator is synchronized with master generator 20 of FIG. 2, master generator 20 is reproduced in FIG. 4 designated 20.
  • the output of master generator 20' connects to counter 41, which is arranged to count six input pulses and then reset.
  • Digital counter 41 includes three stages and a feedback path for proper resetting.
  • Leads 42, 43 and 44 extend from the first, second and third stages, respectively, and to a series of AND gates.
  • Leads 42, 43 and 44 each connect to AND gates 45, 46, 47, 48, 49 and 401 so that, as the count in counter 41 changes, one AND gate will be activated to the exclusion of the others.
  • inverters are utilized at the inputs to the AND gates and illustratively shown. The proper use thereof for sequencing purposes is well known in the prior art.
  • the output of AND gate 45 is connected to one input of sampling gates 402, 403, 404, 405, 406 and 407, respectively.
  • the outputs of sampling gates 402- -407 are connected to summing circuit 408, the output of which is connected to low-pass filter 409.
  • FIG. 5 illustrates a series of waveforms found at the inputs and outputs of sampling gates 402-407 and summing circuit 408.
  • FIGS. 3 and 5 are presented on the same sheet of drawings because the waveforms illustratively shown in FIG. 5 are synchronized with the output of the master generator, illustratively shown as waveform A in FIG. 3.
  • time slots have been assigned to consecutive portions of the output of the master generator. Ten time slots are shown in both FIG. 3 and FIG. 5.
  • the operation of counter 41 is well known, and a binary code representing the count in counter 41 is carried on leads 42, 43 and 44.
  • leads 42, 43 and 44 are connected to AND gates 45 through 49 and 401, the outputs of each of which are shown as curves J, K, L, M, N, p, respectively.
  • leads 42, 43 and 44 will each carry binary O, and the output of AND gate 45 will be binary 1 during time slot 1 since each binary 0 is inverted at the input to AND gate 45.
  • the output of AND gate 45 is shown as curve J.
  • binary 0 is considered to be a low voltage, and binary 1 a high voltage. Other arrangements may be provided for carrying out the same logic functions.
  • leads 42 and 43 will carry binary 0, while lead 44 will carry binary 1.
  • a binary 1 will appear at the output of AND gate 46 during time slot 2 since the binary appearing on leads 42 and 43, respectively, will be inverted at the input of AND gate 46.
  • the output of AND gate 46 is shown as waveform K in FIG. 5.
  • the output of AND gate 47 is a binary 1 during time slot 3, illustratively shown as curve L in FIG. 5.
  • the output of AND gate is a binary 1 during time slot 4, illustratively shown as waveform M in FIG. 5.
  • the output of AND gate 19 is binary I during time slot 5, illustratively shown as waveform N in FIG. 5, and the output of AND gate 401 is binary I during time slot 6, illustratively shown as waveform P in FIG. 5.
  • Sampling gates 402 through 407 are two-input devices, one input of which'is connected to AND gate 42 through 49 and 401, respectively, while the other input is connected to the output of the waveshaping devices in FIG. 2.
  • waveform E may be generated by selectively applying the waveforms shown as curve D during time slots 2--5 in FIG. 5 to sampling gates 403-406, respectively, and curve C during time slot 6 in FIG. 6 to sampling gate 407.
  • the waveform generator shown in FIGS. 2 and 4 illustrates a principle of the present invention which provides a significant advantage over the prior art. If pieces of a desired waveform are improperly synchronized, significant discontinuities would result in the produced waveform. This may be seen by referring to curves C and D in FIG. 5. During time slot 2, it is desired that the waveform shown as curve C not contribute to waveform E, while the waveform shown as curve D contribute to the desired function to be produced. If there is a lack of synchronization between the apparatus which operates during timeslot 1 and time slot 2, curve C may contribute during a part of time slot 1. This synchronization problem, therefore, may cause significant error in the produced waveform. By utilizing the principles of the present invention, the synchronization problem is eliminated because the frequency dividers and the control signal generator are sychronized with a master generator.
  • FIGS. 2 and 4 illustrates the application of the principlesof the present invention in a waveform generator
  • modulation may also be realized by using the principles of the present invention.
  • the process of selectively combining a desired waveform includes the capability to shape a waveform in accordance with digital control signals where the digital control signals represent modulation information.
  • the generalized block diagram of FIG. I may be utilized to achieve this modulation.
  • a waveform generator comprising:
  • a first waveshaping network connected to receive said pulse signals and convert them to an output signal of frequency f
  • a square wave pulse generator connected to receive said pulse signals and produce a pulse signal output of a second periodicity
  • a second waveshaping network connected to receive the output pulses of said pulse generator and convert them to an output signal of frequency f
  • a control signal generator connect receive said pulse signals of said first periodicity
  • a waveform generator comprising:
  • each of said elementary wave generators comprising a frequency divider and a waveshaping network connected to the output of the frequency divider, the frequency divider of each of said elementary wave generators producing a square wave pulse signal output having a periodicity different from the periodicity of the frequency divider outputs of v the other elementary wave generators,
  • control signal generator connected to receive pulse signals of said first periodicity from said source
  • each of said waveshaping networks comprises a low pass filter and an amplifier.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Manipulation Of Pulses (AREA)
  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)
US763301A 1968-09-27 1968-09-27 Waveform generator Expired - Lifetime US3579117A (en)

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US76330168A 1968-09-27 1968-09-27

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US (1) US3579117A (xx)
JP (1) JPS4922071B1 (xx)
BE (1) BE739422A (xx)
DE (1) DE1947381A1 (xx)
FR (1) FR2019088A1 (xx)
GB (1) GB1288974A (xx)
NL (1) NL6914261A (xx)
SE (1) SE366180B (xx)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3671871A (en) * 1970-12-14 1972-06-20 Northrop Corp Signal frequency synthesizer
US3733555A (en) * 1970-08-19 1973-05-15 Marshall Research & Dev Corp Shock spectrum analyzer and synthesizer system
FR2175178A1 (xx) * 1972-03-08 1973-10-19 Gen Electric
US3801807A (en) * 1972-10-27 1974-04-02 Bell Telephone Labor Inc Improved shift register having (n/2 - 1) stages for digitally synthesizing an n-phase sinusoidal waveform
US3938071A (en) * 1973-06-13 1976-02-10 Commissariat A L'energie Atomique Generator for controlling an ultrasonic transducer
US4137500A (en) * 1976-12-07 1979-01-30 Weber Harold J Frequency dependent amplitude modulated exciter apparatus
US4783632A (en) * 1986-07-03 1988-11-08 Hughes Aircraft Company Multi-arm frequency sweep generator
US5091699A (en) * 1990-11-14 1992-02-25 General Electric Company Frequency division network having low phase noise
US5121069A (en) * 1988-12-16 1992-06-09 Siemens Transmission Systems, Inc. Low frequency sinewave generator
US5332975A (en) * 1992-12-01 1994-07-26 Netmedia Inc. Sine wave generator utilizing variable encoding for different frequency signals
US5500613A (en) * 1994-03-11 1996-03-19 Siemens Aktiengesellschaft Method for producing a digital sine wave signal with a given sampling rate, and circuit configuration for carrying out the method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2247792A (en) * 1990-08-31 1992-03-11 Philips Electronic Associated Sinewave generators

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2566085A (en) * 1949-02-26 1951-08-28 Rca Corp Electronic interval timing method and system
USRE24053E (en) * 1949-01-11 1955-08-23 Source
US3223925A (en) * 1962-01-29 1965-12-14 Ibm Digital data modulation device
US3319170A (en) * 1963-03-28 1967-05-09 Raytheon Co Trigger pulse threshold level adjustment circuit
US3325721A (en) * 1966-03-18 1967-06-13 Albert A Clark Variable frequency changer with means for continuously changing phase of the input frequency signal
US3349257A (en) * 1965-10-22 1967-10-24 Int Research & Dev Co Ltd Sine wave synthesis circuit

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE24053E (en) * 1949-01-11 1955-08-23 Source
US2566085A (en) * 1949-02-26 1951-08-28 Rca Corp Electronic interval timing method and system
US3223925A (en) * 1962-01-29 1965-12-14 Ibm Digital data modulation device
US3319170A (en) * 1963-03-28 1967-05-09 Raytheon Co Trigger pulse threshold level adjustment circuit
US3349257A (en) * 1965-10-22 1967-10-24 Int Research & Dev Co Ltd Sine wave synthesis circuit
US3325721A (en) * 1966-03-18 1967-06-13 Albert A Clark Variable frequency changer with means for continuously changing phase of the input frequency signal

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3733555A (en) * 1970-08-19 1973-05-15 Marshall Research & Dev Corp Shock spectrum analyzer and synthesizer system
US3671871A (en) * 1970-12-14 1972-06-20 Northrop Corp Signal frequency synthesizer
FR2175178A1 (xx) * 1972-03-08 1973-10-19 Gen Electric
US3873928A (en) * 1972-03-08 1975-03-25 Gen Electric Reference wave generator using logic circuitry for providing substantially sinusoidal output
US3801807A (en) * 1972-10-27 1974-04-02 Bell Telephone Labor Inc Improved shift register having (n/2 - 1) stages for digitally synthesizing an n-phase sinusoidal waveform
US3938071A (en) * 1973-06-13 1976-02-10 Commissariat A L'energie Atomique Generator for controlling an ultrasonic transducer
US4137500A (en) * 1976-12-07 1979-01-30 Weber Harold J Frequency dependent amplitude modulated exciter apparatus
US4783632A (en) * 1986-07-03 1988-11-08 Hughes Aircraft Company Multi-arm frequency sweep generator
US5121069A (en) * 1988-12-16 1992-06-09 Siemens Transmission Systems, Inc. Low frequency sinewave generator
US5091699A (en) * 1990-11-14 1992-02-25 General Electric Company Frequency division network having low phase noise
EP0486132A2 (en) * 1990-11-14 1992-05-20 General Electric Company Frequency division network having low phase noise
EP0486132A3 (en) * 1990-11-14 1992-11-25 General Electric Company Frequency division network having low phase noise
US5332975A (en) * 1992-12-01 1994-07-26 Netmedia Inc. Sine wave generator utilizing variable encoding for different frequency signals
US5500613A (en) * 1994-03-11 1996-03-19 Siemens Aktiengesellschaft Method for producing a digital sine wave signal with a given sampling rate, and circuit configuration for carrying out the method

Also Published As

Publication number Publication date
FR2019088A1 (xx) 1970-06-26
DE1947381A1 (de) 1970-04-23
BE739422A (xx) 1970-03-02
SE366180B (xx) 1974-04-08
NL6914261A (xx) 1970-04-01
JPS4922071B1 (xx) 1974-06-05
GB1288974A (xx) 1972-09-13

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