US2255839A - Periodic wave repeater - Google Patents

Description

Sept. 1941- J. 0. WILSON 2,255,839

' PERIODIC WAVE REPEATER Filed March 1, 1940 FIG.|.

lhc

1 "I 2 M 3 "a B I] H FL n nfv g, 2 3 93 F|G.3.

INVENTOR ATTORNEY Patented Sept. 16, i941 masts rnnromc wava mean-in John 0. Wilson, amide, N.

tine Corporation, a corpora Y I assignor to Basel horn of Delaware Application March 1, 1940, Serial No. 321,659

12mins.

This invention relates to periodic wave repeaters and, while the invention is or general application, the periodic wave repeater o! the invention is particularly suitable for eflectively re peating only predetermined pulses oi a periodicpulse wave for use in a television signal receiver.

It is frequently desirable, especially in the synchronizing system of a television signal receiver, to clean all undesired or spurious pulses, noise, and static from a periodic-pulse wave and to repeat only selected desired pulses. In the.

past it has been proposed to use selectively-responsive periodic w'ave repeaters for this purcl. etc-s1) visionsignal receiver of all unwanted frequency components.

In accordance with the present invention, there is provided a periodic wave repeater adapted etiectively to repeat only predetermined pulses of a wave including periodic pulses, which comprises a vacuum tube having an input circuit adapted to have said wave applied thereto, and

an output circuit. The repeater includes also impedance means degenerativelycoupling these circuits and eilfective to apply to the input circuit a voltage of the same phase as that oi. the output circuit and including frequency-selective means pose. For example, it has been proposed to provide a periodic wave repeater comprising a vacuum tube normally biased substantially to cutoi! and having input and output circuits one of which is a sensitivity-controllingcircuit for the vacuum tube. A time-delay network is coupled to the sensitivity-controlling circuit and, at the time a given output pulse is due irom the repeater, there is applied to the delay network an input pulse which is so delayed by the network and applied to the sensitivity-controlling circuit thereby with such polarity as to sensitize the vacuum tube for operation at the time the succeeding output pulse is vdue. Certain M such eriodic wave repeaters, while effective to an extent in cleaning interference and unwanted pulses from selected pulses of a periodic-pulse wave, for example, a synchronizing-pulse wave,

are not entirely eflective in cleaning all unwanted irequency components irom the wave tov that, for example, a clean line-synchronizing wave may be applied to the line-scanning oscillator. Certain other of such periodic repeaters for substantially reducing the degenerative 'efl'ect thereof at the fundamental frequency and at least one harmonic frequency of the aforesaid predetermined pulses. The impedance means may comprise irequency-selective means tuned to resonate at the fundamental frequency and one or more harmonic frequencies or the predetermined pulses ior reducing the degenerative etiect, oi the impedance means at such frequencies, thereby to clean the wave 01 unwanted frequency components. The impedance means alternatively may include a reflecting time-delay circuit for altering the degenerative effect of the impedance means to predetermined pulses.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the I appended claims.

are regenerative, so that the-circuit (11: is

critical and the output of the generator varies in amplitude with the amplitude of the input periodic-pulse wave.

It is an object of the present invention, there- .101'8, to provide an improved periodic wave repeater which is effective to overcome one or more of the above-mentioned disadvantages and undesirable features of the arrangements of the prior It is another object of the inventionto provide an improved periodic wave repeater which is 121- iective to repeat nonregeneratively-selected pulses of a periodic-pulse wave and selectively to degenerate all other ignal components.

It is a specific object of theinvention to provide a periodic wave repeater which ,is eflective to clean the synchronizing-pulse wave of a tele- In the accompanying drawing, Fig. i is a circuit diagram, partially schematic, 01 a periodic wave repeater embodying the present invention; Fig. 2 is a circuit diagram of a modification or the circuit of Fig. 1; while Fig.3 is a group of curves oi assistance injexplaining the operation of the.

invention. I

Reierring now more particularly to Fig. l of the drawing, there is illustrated a periodic wave repeater comprising a vacuum tube ll having an input circuit the terminals H, ll- 01 which are adapted to have applied thereto a wave including periodic pulses, such as the synchronizing-signal wave 01 a television signal receiver. Included in a grid-leak resistor it. The output circuit 0! the tube ll. includes a coupling resistor l4 across which are Wted output terminals II, II, and a source of unidirectional potential I. The in-' put and output circuits or tube ll have a single path common thereto,.comprising a cathode circuit, and are degeneratively coupled by imthe input circuit are a couplingcondenser l2 and quency-selective' impedance means I! connected in the portion of the cathode circuit common to the input and output circuits and including'fre- I vquency-selective means resonant at the fundamental frequency and at least one harmonic frequency ofthe applied periodic pulses for developing a degenerative effect which is greater at f frequencies other than the fundamental frequency and at least one harmonic frequency of the pulses desired to be repeated by the tube 10. For example, the impedance means 11 may compriseconventional circuit means tuned to pro-'- vide minimum terminal impedance only' at the fundamentalfrequency and one or more harmonic frequencies of the predetermined pulses.

At all'other frequencies the impedance of the unit ll is made large relative to that of the coupling resistor M. A conventional circuit fulfilling the requirements of an impedance means of this character is shown in Electric Circuits and Wave Filters by A. T. Starr (Pitman1934) "page 216, Fig. 198. v r

In considering the operation of the periodic wave repeater shown in 'Fig. 1, it will be assumed that an input waveincluding periodic pulses is .applied to the input terminals, II II. The impedance means "I1 is efiectiveto apply to the input circuit'of tube ID a voltage of the same phase I as that of the output circuit of this tube for substantially reducing the degenerative eifect of the impedancemeans H at the fundamental frequency and at least one harmonic frequency of the applied periodie' pulses. Thus, those frequency componentsof predetermined pulses at which the impedance I| has a minimum im- Thatis, the unwanted pulses are effectively reduced by the degenerative effect of the impedance means i'l. Referring now tperiodic wave repeater shown is essentially simiinto that ofFig. '1 and similar circuit elements have ,been givenidentical. reference numerals.

I 'The circuit of Fig. 2 differs primarily from that "of. Fig. 1 in that the cathode circuitof vacuum 1 tube- III, which is common to the input and output circuits, includes a-frequency-selective degenerative means consisting of a resistor i8 and a' reflecting time-delay circuit'connected thereacrossfcomprising series-inductance elements i9 and shunt-capacitance elements 20 and termiating at its remoteend in a short-circuit. The T- delay circuit may include any desired number of 1 elements 19,20 depending upon the desired degree ofgfldelity of reproduction of repeated pulses. The. delay circuit and resistor. It together have minimum terminal impedance at the fundamental of the periodic pulses as described more fully in the co'pending United Statespatent application Lewis, Serial No. 262,846, filed.

- "of "Harold M.

"March 20, 1939. In considering the operation frequency-and at least one harmonic frequency wave repeaterof Fig. 2, reference ismade to Fig.

f periodic pulses, which is appliedto the input cirmore particularly to Fig. 2, the

cuit of tube It). The first input pulse (21 results in-the formation of a large first degenerative pulse In of wave B across cathode resistor l8 which has a large degenerative eifect on the first repeated output pulse 01 of output wave C. The

next input pulse or, however, occurs at thesame instant as the delayed and reversed reflection of the-first pulse applied to the delay circuit I9, 20

appears across resistor I 8.. These two pulses of opposite polarity partially cancel each other so that the net degenerative pulse 122 is reduced and the degenerative effect of resistor I8 is partially neutralized as to such input pulse 112 and the second output pulse c: is consequently of increased amplitude. If there is a mismatch of the impedance of resistor I8 and that of the circuit in-.

eluding elements I9, 20, multiple reflections are set up which aids the desired degenerative action and, as this action continues, the amplitude of the output pulses of wave, C increases to a maximum represented by the .pulse C; which has a steady value determined largely by the amount of mismatching of the impedance of resistor I8 with the reflecting filter i9, 20. Likewise, the resultant degenerative pulses b3 reach a small constant amplitude determined primarily 'by the mis--- matching ofv the system. The rate at which'the output pulses build up and also their final am plitudes are thus determined primarily by the degree of impedance mismatch between the resistor l8 and the delay circuit I9, 20.

If there is no mismatch of impedances as'between element l8 and the time-delay reflecting filter including elements I9, 20, there are, of

course, no reflections of the delayed pulses at resistor l8 and the output amplitude of the wanted 4 only output pulses of opposite-polarity which can pulses reach their maximum value'upon the simultaneous application of the second pulse 111 of curve A and the reflected pulse bar to the system.

'While the input circuit of the tube and spurious pulses along with the input wave A, the frequency components thereof are such that as to them the resistor I8 is degenerative in the normal manner, the time delay of the reflecting circuit I9, 20 being such that their reflections, due

to their sporadic occurrence, are not, in general,

in phase withany subsequent spurious or un-'.

wanted pulses and, since the reflected pulses are of opposite polarity, they are effective to develop be readily suppressed.

It is seen, therefore,

corresponding pulses in the output of the system. Therefore, amplitude-selecting means couof. the periodic a 3-i11ustrating awaven, including predetermined input circuit of tube 1 o;

pied at a point in the'system succeeding terminals It may be utilized completely, to separate the wanted pulses from the. spurious or unwanted pulses which appear with very much reduced rela- I.

tive amplitude in the output of thesystem. Such amplitude-selecting means maybe such as to select only, a predetermined portion ofthe plitude range of the output signal in a manner) well understood in the art. Also, it will "be understood that the signal input'to the system Y I of the in'ventioncan be limited so that no unwanted components appear inithe input to tube III with amplitudes appreciably greater'than the amplitude of the wanted pulses While there have been described what are at present considered, tobe the preferred embodi- 'Ill may'be subject to the application of static,interference,.

that the system of the invention is eifectiveto amplify the pulses of curve A to provide very much increased amplitude of applied to the a and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

said wave, whereby said vacuum tube is effective to repeat such pulses.

6. A periodic wave repeater adapted effectively to repeat only predetermined pulses of a wave including periodic pulses comprising, a vacuum tube having an input circuit adapted to have said 1. A periodic wave repeater adapted effectively to repeat only predetermined pulses of a wave including periodic pulses comprising, a vacuum tube having an input circuit adapted to have said' determined pulses.

2. A periodic wave repeater adapted effectively to repeat only predetermined pulses of a wave including periodic pulses comprising, a vacuum tube having an input circuit adapted to have said wave applied thereto and an output circuit, and impedance means degeneratively coupling said circuits and effective to apply to said input circuit a voltage of the same phase as that of said output circuit and including frequency-selective means resonant at the fundamental frequency and at least one harmonic frequency of said predeter mined pulses of said wave for substantially reducing the degenerative effect of said impedance means to said pulses.

3. A periodic wave repeater adapted effectively to repeat only predetermined pulses of a wave in- .cluding periodic pulses comprising, a vacuum pulses of said wave, whereby said vacuum tube is effective to repeat such pulses.

4. A periodic wave repeater adapted effectively to repeat only predetermined pulses of a wave including periodic pulses comprising, a vacuum tube having an input circuit adapted to have said wave applied thereto and an output circuit, and an impedance elementdegeneratively coupling said circuits and effective to apply to said input circuit a voltage of the'same phase as that of said output circuit and including a reflecting time-delay circuit coupled to said impedance element for reducing the degenerative effect of said impedance element to said predetermined pulses of said wave, whereby said vacuum tube is effective to repeat such pulses.

5. A periodic wave repeater adapted effectively to repeat only predetermined pulses of a wave including periodic pulses comprising, a vacuum tube having an input circuit adapted to have said wave applied thereto and an output circuit, and impedance means degeneratively coupling said circuits and effective to apply to said input circuit a voltage of the same phase as that of said output circuit and including a time-delay circuit terminated at its remote end in a short-circuit for decreasing the degenerative effect of. said impedance means to said predetermined pulses of wave applied thereto and an output circuit, and impedance means degeneratively coupling said circuits and effective to apply to said input circuit a voltage of the same phase as that of said output circuit and including a time-delay circuit for substantially neutralizing the degenerative effect of said impedance means to said predetermined pulses of said wave, whereby said vacuum tube is eflective'to repeat such pulses.

7. A periodic wave repeater adapted effectively to repeat only predetermined pulses of a wave including periodic pulses comprising, a vacuum tube having an input circuit adapted to have said wave applied thereto and an output circuit, a resistor degeneratively coupling said circuits to render said vacuum tube normally unresponsive to repeat said wave, and a time-delay circuit coupled to said resistor for reducing the degenerative effect of said resistor to said predetermined pulses of said periodic-pulse wave, whereby said vacuum tube is effective to repeat such pulses.

8. A periodic wave repeater adapted effectively to repeatonly predetermined pulses of a wave including periodic pulses comprising, a vacuum tube having an input circuit. adapted to have said wave applied thereto and an output circuit, a cathode circuit common to said circuits and including impedance means effective to apply to said input circuit a voltage of the same phase as that of said output circuit, and frequency-selective means included in said impedance means for substantially reducing the degenerative effect thereof at the fundamental and at least one harmonic frequency of said predetermined pulses.

9. A periodic wave repeater adapted effectively to repeat only predetermined pulses of a wave including periodic pulses comprising, a vacuum tube having an input circuit adapted to have said wave applied thereto and an output circuit, a

cathode circuit common-to said circuits and including an impedance element to render said vacuum tube normally unresponsive to repeat said wave, and a reflecting time-delay circuit coupled to said impedance element and terminated at its remote end in a short-circuit for neutralizing at least a portion of the degenerative effect of said impedance element to said predetermined pulses of said wave, whereby said vacuum tube is effective to repeat such pulses.

10. A periodic wave repeater adapted effectivelycathode circuit common to said circuits and iricluding a resistor to render said vacuum tube normally unresponsive to repeat said wave, and a reflecting time-delay circuit connected across said resistor and terminated at its remote end in a short-circuit for substantially neutralizing the degenerative eflectof said resistance meansto said predetermined pulses of said wave, whereby impedance means connected degeneratively to couple said circuits, said impedance means including frequency-selective means having minimum terminal impedance at the fundamental frequency and at least one harmonic frequency of said predetermined pulses, whereby such pulses are repeated by said vacuum tube.

12. A periodic Wave repeater adapted effectively to repeat only predetermined pulses of a wave in cluding periodic pulses comprising, a vacuum 10 Q tube having an input circuit adapted to have said wave applied thereto and an output circuit, a single path common to said circuits, and impedance means included in said path and "ineluding frequency-selective means connected degeneratively to couple said circuits for modifying the degenerative effect thereof at the fundamental frequency and at least one harmonic frequency of said predetermined pulses.

. JOHN C. WILSON;

Images