US2164176A - Method and system for television communication - Google Patents

Method and system for television communication Download PDF

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Publication number
US2164176A
US2164176A US195441A US19544138A US2164176A US 2164176 A US2164176 A US 2164176A US 195441 A US195441 A US 195441A US 19544138 A US19544138 A US 19544138A US 2164176 A US2164176 A US 2164176A
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United States
Prior art keywords
frequency
sweep
wave
carrier
signals
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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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US195441A
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English (en)
Inventor
Jr Thomas T Goldsmith
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Allen B du Mont Laboratories Inc
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Allen B du Mont Laboratories Inc
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Filing date
Publication date
Application filed by Allen B du Mont Laboratories Inc filed Critical Allen B du Mont Laboratories Inc
Priority to US195441A priority Critical patent/US2164176A/en
Priority to GB7814/39A priority patent/GB526211A/en
Priority to FR851501D priority patent/FR851501A/fr
Priority to US263510A priority patent/US2201309A/en
Application granted granted Critical
Publication of US2164176A publication Critical patent/US2164176A/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/04—Synchronising
    • H04N5/06—Generation of synchronising signals
    • H04N5/067—Arrangements or circuits at the transmitter end
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K4/00—Generating pulses having essentially a finite slope or stepped portions
    • H03K4/06—Generating pulses having essentially a finite slope or stepped portions having triangular shape
    • H03K4/08—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape
    • H03K4/10—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only
    • H03K4/12—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only in which a sawtooth voltage is produced across a capacitor
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/04—Synchronising
    • H04N5/06—Generation of synchronising signals
    • H04N5/067—Arrangements or circuits at the transmitter end
    • H04N5/073—Arrangements or circuits at the transmitter end for mutually locking plural sources of synchronising signals, e.g. studios or relay stations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/06—Systems for the simultaneous transmission of one television signal, i.e. both picture and sound, by more than one carrier

Definitions

  • My invention relates to improvements in methods and systems for television communication.
  • Another object of my invention resides in the provision of an improved method and system for television communication which has advantages over those proposed heretofore in the way of greater simplicity of construction'and manner of operation, and higher efiiciency.
  • Another object of my invention resides inthe provision of an improved method and system for television communication by which the various 40 necessary signals can be transmitted by wireless over substantially greater distances than it has been possible with the various methods and systems proposed heretofore, the possible range of wireless transmission from the transmitting station directly to a receiving station being of the order ofhundreds of miles.
  • Eof t epick-up tube at the transmitter and scanso that the electron ray in the tubes must of necessity be always in step during the scanning action. Because of the impossibility of this system getting out of synchronization as to both line and frame or field frequencies, a much high- 5 er interlace ratio is possible. This allows a given detail picture to be transmitted over a much narrower frequency band. Likewise, the transmission of much higher definition pictures over the same frequency band can also be accom- 10 plished.
  • Another advantage of this system is that it will receive pictures of transmitters operating at any desired line and frame frequencies. With the present systems, it is necessary that all trans- 5 mitters operate with exactly the same respective scanning frequencies if all receivers are to be capable of receiving from any one of the transmitters.
  • My invention resides in the improved meth g0 and system of the character hereinafter described and claimed.
  • Figures 1 and 2 are simplified, diagrammatic views of a television transmitting station and a television receiving station, respectively, constructed and operating in accordance with my invention;
  • Figs. 3 and 4 are graphical representations of electrical wave forms possible for use in my improved system for governing the scanning action.
  • Figs. 5, 6 and '7 show circuit details for use in 35 my improved system.
  • the reference numeral I0 designates a cathode-ray pick-up tube of a conventional construction, and comprises a mosaic, photoelectric screen on which a light image of the object 4 is projected, an electron gun for generating a ray of electrons directed at the screen, and two sets of deflecting plates for deflecting the electron ray at the line and field frequencies respectively so that'it is caused to scan the screen.
  • the picture 45 I or video signals are thereby developed, and fed by an output connection II to a modulating amplifier l2.
  • a first, main carrier wave is provided by an oscillator l3.
  • this carrier wave is modulated bythe wide frequency band video signal through the modulating amplifier I2.
  • the signals from the amplifier l4 are supplied by a connection I5 to a mixer circuit l6.
  • the reference numerals I1 and i8 designate generators of voltage waves of sine form for the sweeps and which are, respectively, at the desired field and line frequencies.
  • the low-frequency sweep by means of the amplifier l9, modulates the sub-carrier oscillator in its amplifier stage 2
  • the high-frequency sweep by means of the amplifier 22, modulates the sub-carrier oscillator 23 in its amplifier stage 24.
  • the audio or sound signals from the microphone 25 are passed through an amplifier 28.
  • the two sweep signals and the audio signals are applied through a mixer circuit 21 to modulate, in the power amplifier stage-28 of an oscillator 29, a second, main carrier wave:
  • the signals from the amplifier 28 are supplied by a connection 30 to the mixer circuit IS.
  • the two carrier waves, one modulated by the video signals and the other modulated by the two sweep signals and the sound signals, are mixed in the mixer circuit l6 and fed to a common antenna 3
  • the two sweep signals are transmitted in the form of sine waves, in Fig. 1 they are not used as such for direct application to the two respective sets of electrostatic deflecting plates, but are first changed or modified to waves of saw-tooth form by wave-form modifying means or networks 32 and 33.
  • wave-form modifying means or networks 32 and 33 An example of such a network is shown in Fig. 5, in which the sine-wave input is fed through a rectifier 34 to a filter section consisting of a condenser 35 and a resistance 36, from which section is delivered the desired output wave of saw-tooth form.
  • Fig. 1 it is proposed to use a frequency-multiplying method for the purpose of maintaining constant, particularly where interlaced scanning is used, the relation of line frequency to field frequency.
  • a system or circuit for such purpose is shown in Fig. 6, in which a low-frequency voltage wave of sine form, such as the 60-cycle power main frequency, is fed through successive fullwave rectifiers 31, 38, etc., followed by filters, as shown, to allow passage of the double-frequency harmonics. In this way there is produced a final and much higher frequency which can be utilized for the high frequency sweep coordinated with the original low-frequency sweep for the two respective deflections for scanning.
  • Fig. 6 there is shown only two stages of the frequency-multiplication scheme.
  • a transformer primary 3!] is excited by 60 cycles, and the tapped secondary supplies the full-wave rectifier 31 which de-' livers 120 cycles to the tuned filter comprising the condenser 4
  • the 120-cycle signal is supplied by the tapped secondary 43 to the full-wave rectifier 38 and thence at the double frequency of 240 cycles to the condenser 44 and the next succeeding transformer primary 45.
  • the tapped secondary 46 delivers signals to the next stage, and so on until the required high frequency for linescanning is'obtained. In event the resistances of the transformers are too low, resistances may be inserted in the rectifier circuits for the purpose of limiting the direct current.
  • FIG. 7 An alternative and simplified system or circult, for the same purpose as that shown in Fig. 6, is shown in Fig. 7.
  • the reference numerals 41, 48 and 48 designate transformer windings, connected as shownwith respect to full- :gave rectifiers 50 and 5
  • Figs. 6 and '7 conventional amplifier stages may be employed when needed.
  • phase-shifting networks may be inserted in one or more stages of the frequencymultiplication system.
  • the video signals instead of being fed to the mixer l6, may be applied by the connection l5 to another antenna system independent of the antenna 3
  • the antenna 54 applies the combined carrier signals, from the transmitter antenna 3
  • 'A local oscillator 56 reacts with these signals in a first detector stage 51, on the superheterodyne principle, to produce two intermediate-frequency signals which are supplied to the respective intermediate-frequency channels or stages 58 and 59.
  • the video signal is detected at 60 and applied by a connection 5
  • the device 62 is represented as being in the form of a cathode-ray tube of a common construction, and comprising a fluorescent screen, an electron gun for developing a ray of electrons directed at the screen, and two sets of electrostatic plates for deflecting the electron ray at the respective line and field frequencies to cause it to scan the screen.
  • the video signals are applied to a control electrode of the electron gun whereby the intensity of the electron ray is made to vary with the picture or video signals.
  • the signal in the intermediate-frequency stage 59 still contains the two sweep signals and the audio signals, which now require separation.
  • a second detector 83 of relatively wide band output removes the composite signals from the intermediate-frequency carrier, the output from this detector going to three selective filters 64, and 85.
  • the low-frequency sweep signal still in the form of modulation upon its carrier, is detected at 61 to produce in the output line 68 a voltage wave of sine form which is changed, by a waveform modifying network 69 similar to the network 32 in Fig. 1, to a saw-tooth voltage wave which is applied across the corresponding deflecting plates.
  • the high-frequency sweep signal still in the form of modulation upon its carrier, is detected at 10 to produce in the output line H a voltage wave of sine form which is changed by a wave-form modifying network 12 similar to the network 33 in Fig. 1, to a saw-tooth voltage wave which is applied across the corresponding deflecting plates.
  • the audio signal in its original form from the filter 66, is fed to a loudspeaker I3.
  • the unit v85 represents an automatic signal-level control circuit which, in the well known manner, utilizes a rectified portion of the received signal to adjust the bias on previous stages to aid in maintaining substantially constant signal output.
  • signal for the unit 85 is taken from the high-frequency sweep circuit.
  • Automatic control based on the fixed, high-frequency sweep signal, will be steady and independent of background variations of the video signal.
  • the output control signal from the unit 35 is applied to control bias in the first detector stage 51 and in the intermediatefrequency channel 59.
  • the generators l1 and I8 may be made to develop saw-tooth sweep wave forms, as shown in Fig. 3.
  • Such a sweep wave form is characterized by having a relatively wide frequency band necessary for faithful transmission. Its fundamental frequency and also its harmonics up to about the tenth should be provided for. This type of scanning provides systematic and uniform coverage of the screen, and though high in harmonic content can still be used with this system by proper design of the intermediate-frequency filters.
  • FIG. 4 Another wave shape, illustrated in Fig. 4, may be transmitted, in which case the generators l1 and I8 are designed accordingly. It is characterized by equal slopes of the forward and return traces, thus containing a much lower harmonic content, simplifying the transmission problem considerably. Interlace here takes on a somewhat different interpretation, but pictures produced in this manner prove to be very satisfactory.
  • -cies indicated in Figs. 1 and 2 are by way of example only, and that these might vary widely to meet particular requirements.
  • a feature of my improved system of television is the exclusive generation of the sweeps at the transmitter and actual transmission of these sweeps to the receiver, thus insuring perfect synchronism of scanning. No synchronization is required.
  • the interlace can be quite'complex. with a high interlace ratio such as 4, for example, and yet will remain in adjustment. Receiver controls are greatly simplified.
  • Another feature of my improved system is the use of sweeps of simple wave form, thereby providing a narrow frequency band and consequent simplified amplification and transmission of the sweeps.
  • Still another feature of my improved system resides in the reduced video-frequency band possible with the multiple interlace or high interlace ratio, yet giving high definition pictures.
  • this reduced video-band width and its relatively narrow associate band containing the audio and the sweeps it is practical to utilize other and lower carrier frequencies than those suggested in Figs. 1 and 2, and thus to employ carriers which are not limited to an optical horizon for satisfactory coverage.
  • the frequency width of the video signals illustrated in Figs. 1 and 2 has been shownas those characteristic of a picture of about 600- line definition and the carriers chosen are merely suggestive. One can see that even with this provision for a 'video channel of higher definition than provided in a unit with the 441-line standards with 2 to 1 interlace, the ultra-high frequency band still is not increased over that required for the 441-line 2 to 1 interlace pictures.
  • a receiver of the type illustrated would-be versatile in its ability to accept transmissions from different stations utilizing different degrees of detail. Given a specified band pass in each channel, then pictures of any detail up to a certain limit could be accepted by simply tuning to the appropriatqR. F. carrier of the station in question, without necessity of local adjustment to duplicate their particular sweep system. It will facilitate public field installation of television systems without the fear of equipment becoming immediately obsolete when definition changes are "desired.
  • Another advantage of my improved system is the possibility of the use of automatic volume control, or automatic signal-level control by application from one or the other fixed signals in the sweep circuits. Automatic control based on this signal will be steady and independent of background variations of the video signal.
  • the television system herein disclosed allows practic'ally any type of interlacing to be employed. For example, assume that there is employed a vertical sweep of sixty fields per second, which is well beyond the flicker limit. Now a horizontal frequency of 3000 cycles per second would give fifty lines with exact progressive scanning. Now an increase to 3030 cycles will provide 101 lines in the complete picture with a two to one interlace ratio. The picture repetition rate is reduced to 30 per second, but there is still no appreciable loss in picture continuity. Now use some horizontal sweep such as 3002 cycles per second and the scanning will return to a given configuration only after half a second.
  • a feature of my improved system resides in the utilization of actual scanning wave shape transmission suitable for electrostatic cathode-ray deflection, though with proper amplifiers, the use of electromagnetic deflection is also possible. It is obvious that utilization of electrostatic deflection at the receiver would allow the same to follow the changes in scanning frequency or wave-form, when these might be varied at the transmitter. It would be more difficult' to design anelectromagnetic system having this same flexibility.
  • Another feature of my improved system is the possibility of further simplification of the receiver equipment if operated on a common power main with the transmitter, for then the power mains frequency may be employed for the low sweep.
  • the transmitter carrier may still contain this low sweep component even when exciting such a receiver, for no disturbance will be experienced if units 64 and 61 in Fig. 2 are omitted and replaced by suitable attachments to the power mains. In the light of this modiflcation, it would be most practical to secure the automatic signal-level control voltage from the high sweep channel which will be present in all receivers.
  • Still another advantage of my improved system is that its receivers will be versatile enough to receive both the highest definition pictures and the low definition pictures even of the amateur experimenters where cost of transmitter equipment is'a limit of the definition which can be provided.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Television Systems (AREA)
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US195441A 1938-03-12 1938-03-12 Method and system for television communication Expired - Lifetime US2164176A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US195441A US2164176A (en) 1938-03-12 1938-03-12 Method and system for television communication
GB7814/39A GB526211A (en) 1938-03-12 1939-03-10 Methods and systems for television communication
FR851501D FR851501A (fr) 1938-03-12 1939-03-11 Procédés et systèmes de communications de télévision
US263510A US2201309A (en) 1938-03-12 1939-03-22 Method and system for television communications

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Application Number Priority Date Filing Date Title
US195441A US2164176A (en) 1938-03-12 1938-03-12 Method and system for television communication

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US2164176A true US2164176A (en) 1939-06-27

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US263510A Expired - Lifetime US2201309A (en) 1938-03-12 1939-03-22 Method and system for television communications

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US263510A Expired - Lifetime US2201309A (en) 1938-03-12 1939-03-22 Method and system for television communications

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GB (1) GB526211A (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2495790A (en) * 1940-12-19 1950-01-31 Valensi Georges Scanning system for television receivers
US2653184A (en) * 1948-01-03 1953-09-22 American Optical Corp Transmission of picture and sound on the same carrier
US2656411A (en) * 1949-03-15 1953-10-20 Zenith Radio Corp Television subscriber signaling system
US2656407A (en) * 1949-02-12 1953-10-20 Zenith Radio Corp Subscriber signaling system
US2677719A (en) * 1948-05-29 1954-05-04 Zenith Radio Corp Subscriber television system
US2706218A (en) * 1949-11-15 1955-04-12 William A Wootten System for television-program film recording and record reproduction
US3018053A (en) * 1958-08-04 1962-01-23 Frederick C Alpers Function generator using televisiontype scanning

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2899496A (en) * 1959-08-11 Process for television transmission
US2521009A (en) * 1943-02-24 1950-09-05 John H Homrighous Television system
US2521008A (en) * 1944-06-27 1950-09-05 John H Homrighous Television and sound multiplex system
NL136716C (fr) * 1946-12-10
US2686220A (en) * 1948-05-28 1954-08-10 Rca Corp Conveyeance of auxiliary information in a television system
US3020340A (en) * 1958-06-03 1962-02-06 Lockheed Aircraft Corp Television synchronizing system

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2495790A (en) * 1940-12-19 1950-01-31 Valensi Georges Scanning system for television receivers
US2653184A (en) * 1948-01-03 1953-09-22 American Optical Corp Transmission of picture and sound on the same carrier
US2677719A (en) * 1948-05-29 1954-05-04 Zenith Radio Corp Subscriber television system
US2656407A (en) * 1949-02-12 1953-10-20 Zenith Radio Corp Subscriber signaling system
US2656411A (en) * 1949-03-15 1953-10-20 Zenith Radio Corp Television subscriber signaling system
US2706218A (en) * 1949-11-15 1955-04-12 William A Wootten System for television-program film recording and record reproduction
US3018053A (en) * 1958-08-04 1962-01-23 Frederick C Alpers Function generator using televisiontype scanning

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Publication number Publication date
US2201309A (en) 1940-05-21
FR851501A (fr) 1940-01-10
GB526211A (en) 1940-09-12

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