US2419193A - Communication system - Google Patents

Communication system Download PDF

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Publication number
US2419193A
US2419193A US468346A US46834642A US2419193A US 2419193 A US2419193 A US 2419193A US 468346 A US468346 A US 468346A US 46834642 A US46834642 A US 46834642A US 2419193 A US2419193 A US 2419193A
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United States
Prior art keywords
pulses
pulse
triangular
voltage
transient
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US468346A
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English (en)
Inventor
Everhard H B Bartelink
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General Electric Co
Original Assignee
General Electric Co
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Filing date
Publication date
Priority to BE478855D priority Critical patent/BE478855A/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US468346A priority patent/US2419193A/en
Application granted granted Critical
Publication of US2419193A publication Critical patent/US2419193A/en
Priority to FR946323D priority patent/FR946323A/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K7/00—Modulating pulses with a continuously-variable modulating signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/02—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation

Definitions

  • 'It is an object of my invention to provide a new and improved method of and apparatus for the transmission of signals of the above type which results in a substantial saving in power input for a given power output or a substantial increase in the power output for a given power input to such a transmitter, as compared with more conventional transmitting systems, without impairing receiver operation.
  • Pulse systems of radio communication have been proposed hitherto. Such systems have been operated at relatively high frequencies as for example 500 to 3000 megacycles because of the preemption of lower frequencies for other services, because of difculties in obtaining sufficient band width at lower frequencies, and also because directional transmission of signals, or beaming has been required in some applications.
  • the pulse system of radio transmission enables a relatively high instantaneous voltage and power to be safely utilized, resulting in a favorable signal-to-noise ratio, without Indeed overloading available types of electron discharge tubes.
  • the transmission of pulses is advantageous for other uses such as the detection of distant objects, range nding, and the like.
  • Hitherto relatively square pulses have been employed in high frequency, -high power audio transmitters. It can be shown that the operation of a receiver is not adversely affected by the transmission of triangular pulses instead of square pulses if the same peak power is maintained.
  • a comparison of pulse shapes shows that for a square pulse of given width and for sub-v butl Whose ⁇ base is twice the width of the square pulse is used to modulate the carrier.
  • the same receiver performance maybe obtained at a 30% saving in input power or, for a given input power to the transmitting system, a 30% increase inreceiver performance or received signal may be obtained if triangular pulses are used rather than the relatively square pulses hitherto employed.
  • Fig. 1 of the drawing there is illustrated in block form the component parts of a radio transmitter suitable for the impression of substantially triangular pulses on anV antenna and typical pulse shapes at different parts of the system.
  • Means for producing a succession of discrete substantially square impulses is provided.
  • a square wave generator I0 of any desirable type, such as a multivibrator and a suitable clipping circuit may be used.
  • the square pulses are passed through a low pass network or filter II which transforms the pulses into triangular shape in accordance with principles explained hereinafter.
  • Such pulses are then usedk to modulate a carrier ⁇ wave obtained from a source of high frequency oscillations such as a master oscillator I2.
  • 'I'he modulated carrier may be applied to the antenna I3 either directly or through a power amplifier.
  • the transmission of the high frequency oscillations is thus controlled by the extent and duration of theV impulses.
  • Modulator and power amplifier are grouped in a single block indicated by the numeral I4.
  • Fig. 2 there is illustrated a system in which square waves from a suitable generator Ill are transformed into triangular pulses in a low'pass lter II andl used to modulate a sub carrier from a source of high frequency oscillations or sub carrier generator I5.
  • the modulator is indicated by the block I6.
  • the System arrangement is the same as that shown in Fig. 1.
  • the signals are used to modulate the main carrier from a second source of high frequency oscillations, or main carrier generator I'I, as indicated by the block I8.
  • Fig. 3 there is illustrated a system similar to that of Fig. .2 except that the square waves from generator I0 modulate the sub carrier and then are transformed into triangular form by means of a suitable band pass filter I9.
  • Fig. 4 represents an idealized relationship between the lter transfer factor A (which is defined as the ratio of the output voltage of the lter to its input voltage), plotted as ordinates,
  • Figs. 6 and 7 represent the rise and decay of the output voltage after applicationto the lter of pulses such as those shown in Fig. 8.
  • the abscissa in Figs. 6, 7 and 8 represents time. Particular instants of time are represented by the vertical dot-dash lines running through Figs. 6, 7 and 8 and designated'ti, t2, etc.
  • the scale for both voltage and time is the same in each iigure. More particularly, Fig,y 6 represents a typical transient curve when a voltage En is'appl'ied to the filter l l.
  • Fig. 6 represents a typical transient curve when a voltage En is'appl'ied to the filter l l.
  • Fig. 7 depicts the pulses of Fig. 8' after passage through a filter section of the type shown in Figs. 1, 2 and 3. LAs will be clear from the following explanation, the pulse shapes of Fig. 7 are only approximations which, however, are ac,- curate for all practical purposes.
  • the distance between the intersection of a line which is tangent to the center part of the slope of the transient curve vT1' with the initial and final values of voltage represents reasonably accurately the time of duration of the transient or ther transient time 'I'. From Equation 3 it can be shown that the distance T between these intersections has the value of approximately where :EL 21r is the cut-off frequency of the lter. In Fig. 6,
  • the origin represents the initial value of voltage and the rhorizontal dot-dash line represents the nal value of voltage.
  • the duration of the pulse is ⁇ made shorter than that of pulse 4', the transients of the beginning and end portions of the pulses overlap; that is, the decreasing transient begins before the increasing transient has reached its peak and the resultant of the transients is a nat topped pulse.
  • the square pulse width isl only that indicated at 2' in Fig. 8
  • the output pulse is-determined by the resultant of transients Tri and Trz as indicated at 2 in Fig. 1.
  • This pulse has a base width vfour times that of the square Ypulse 2 and the maximum voltage of this trapezoidal pulse is muchv less thany the maximum voltage of the triangular pulse 4.
  • graphical addition methods show that the maximum amplitude of the signal is materially reduced if the pulse Width is less than that of the pulse 4 and an increase of th'e pulse duration up Ato time t4 results in increased signal strength at the output of the filter. If the pulse duration is longer than that of pulse li', as indicated at 5 ⁇ of Fig. 8, a flat top pulse whose base width is one and one-half times that ofthesquare pulse results as indicated by the numeral 5 in'Fig. 7. A flat-toppedl pulse is undesirable and unnecessary because the flat portion H. of the wave or pulsey conveys no intelligence.
  • crease oi signal intensity is obtained and the optimum pulse duration is ti-Atl or T.
  • a square pulse is received as a substantially triangular or trapezoidal wave or impulse depending upon the pulsev duration and optimum results are obtained when the square pulse Width is equal to time T andthe triangular pulse has a base width equal'toV 2T or twice the'tr'ansient time of the overall system. While the foregoing discussion related to'the production of pulses in the transmitter, the same considerations lead to .the conclusion that a pulse signal applied to a receiver has a triangular shape in the receiver output irrespective of the shape of the impressed pulse.
  • the pulse is shaped into a triangular form at the transmitter, receiver action will be unimpaired and if the conversion of the pulse to a triangular shape is accomplished before the pulse is impressed on the modulator and power amplifier, the energy otherwise consumed in the pulse at this stage is reduced.
  • the combination of means for reducing the power required by the transmitting means to produce in the receiving means pulses of desired intensity comprising a source of substantially rectangular pulses, means for transforming said pulses into pulses substantially triangular in shape having duration, as measured at the base of said pulses, which is twice the duration of the transient time of the overall system, and means for modulating said high frequency oscillations to provide pulses shaped in accordance with said triangular pulses.
  • the method of reducing the power required at the transmitting station to produce pulses of desired intensity at said receiving station which comprises the step of shaping the envelope of each carrier wave pulse transmitted in the form of a triangle.
  • a carrier wave transmitter a source of square wave pulses, means to modulate the output of said transmitter into pulsesr corresponding to said square wave pulses but the intensity of which increases from Zero to maximum and starts to decrease to Zero when said maximum is reached, said means comprising a network having an input and output, and having a transient period for buildup of voltage in said output in response to voltage supplied to said input, means to supply said square wave pulses to said inut, said pulses having a duration so related to said transient period of said network that the intensity of said pulses as reproduced in said output attains its maximum simultaneously with termination of the pulse supplied to the network.
  • a carrier wave transmitter means to modulate the output of said transmitter to produce recurrent triangular shaped pulses
  • said means comprising a iilter having a transient time between its input and output circuits, means to supply substantially square wave pulses of duration substantially equal to said transient time to said input, and means to modulate the output of said transmitter in accord with the shape of l said pulses as reproduced in said output.
  • a pulse communication system comprising means for transmitting a series of recurrent pulses of high frequency oscillations, said transmitting means comprising a source of substantially rectangular pulses, means including coupling means having input and output circuits for integrating the leading edges of said rectangular Apulses without appreciably reducing their peak intensity, said coupling means having a transient period of build up of Voltage in said output circuit no greater than the duration of said rectangular pulses thereby to provide in said output circuit aseries of reeurrent pulsesof substantially triangular configuration, va, lsource of high ifrequeney carrier Waves, and means for modulating said arrier waves in accordance with said triangular pulses whereby to reduce the input power required -to transmit pulses of a predetermined desired intensity.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transmitters (AREA)
US468346A 1942-12-09 1942-12-09 Communication system Expired - Lifetime US2419193A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE478855D BE478855A (en)) 1942-12-09
US468346A US2419193A (en) 1942-12-09 1942-12-09 Communication system
FR946323D FR946323A (fr) 1942-12-09 1947-05-08 Systèmes de communication par impulsions

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US468346A US2419193A (en) 1942-12-09 1942-12-09 Communication system

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US2419193A true US2419193A (en) 1947-04-22

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BE (1) BE478855A (en))
FR (1) FR946323A (en))

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2564660A (en) * 1946-08-02 1951-08-21 Ollie J Allen Means for interconnecting radio and telephone systems
US2658993A (en) * 1946-07-10 1953-11-10 Rca Corp Loran transmitter

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1695042A (en) * 1923-08-15 1928-12-11 Western Electric Co High-efficiency discharge-device system
GB422468A (en) * 1933-06-09 1935-01-09 Labouchere Hillyer Bainbridge Improvements in and relating to wireless signalling
US2061734A (en) * 1934-09-29 1936-11-24 Rca Corp Signaling system
US2149471A (en) * 1934-05-26 1939-03-07 Rca Corp Saw-tooth wave generator
US2230243A (en) * 1938-06-28 1941-02-04 Philip M Haffcke Signal selection by amplitude discrimination

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1695042A (en) * 1923-08-15 1928-12-11 Western Electric Co High-efficiency discharge-device system
GB422468A (en) * 1933-06-09 1935-01-09 Labouchere Hillyer Bainbridge Improvements in and relating to wireless signalling
US2149471A (en) * 1934-05-26 1939-03-07 Rca Corp Saw-tooth wave generator
US2061734A (en) * 1934-09-29 1936-11-24 Rca Corp Signaling system
US2230243A (en) * 1938-06-28 1941-02-04 Philip M Haffcke Signal selection by amplitude discrimination

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2658993A (en) * 1946-07-10 1953-11-10 Rca Corp Loran transmitter
US2564660A (en) * 1946-08-02 1951-08-21 Ollie J Allen Means for interconnecting radio and telephone systems

Also Published As

Publication number Publication date
BE478855A (en))
FR946323A (fr) 1949-05-31

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