US2211003A - Radio signaling system - Google Patents

Radio signaling system Download PDF

Info

Publication number
US2211003A
US2211003A US187618A US18761838A US2211003A US 2211003 A US2211003 A US 2211003A US 187618 A US187618 A US 187618A US 18761838 A US18761838 A US 18761838A US 2211003 A US2211003 A US 2211003A
Authority
US
United States
Prior art keywords
impedance
grid
quarter wave
cathode
line
Prior art date
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
Application number
US187618A
Other languages
English (en)
Inventor
James W Conklin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RCA Corp
Original Assignee
RCA Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to NL58874D priority Critical patent/NL58874C/xx
Priority to BE432342D priority patent/BE432342A/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US187618A priority patent/US2211003A/en
Priority to GB3154/39A priority patent/GB524416A/en
Application granted granted Critical
Publication of US2211003A publication Critical patent/US2211003A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C7/00—Modulating electromagnetic waves
    • H03C7/02—Modulating electromagnetic waves in transmission lines, waveguides, cavity resonators or radiation fields of antennas
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C1/00—Amplitude modulation
    • H03C1/16—Amplitude modulation by means of discharge device having at least three electrodes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/38—Impedance-matching networks
    • H03H7/383—Impedance-matching networks comprising distributed impedance elements together with lumped impedance elements

Definitions

  • My invention relates to modulating systems, and more particularly to a modulating system for a high frequency television transmitter which consists of varying the internal impedance of 5 modulator tubes connected across the load terminals of a tuned quarter wave transmission line which is so connected that the input terminals of said line effectively vary the impedance across an output load connection such as an antenna.
  • the prior art discloses many ways for modulating high frequency broadcast transmitters. v
  • the wide range and high frequency of the modulation which is necessary in a television transmitter makes methods usually applicable to normal broadcast frequencies unsatisfactory for this purpose.
  • the widely separated side band frequencies would be seriously attenuated by the successive resonant circuits usually employed in broadcast transmitters after the point of modulation.
  • the modulator of the present disclosure broadly relates to the principle concerned in a patent to Crosby, No. 2,085,418, issued June 29, 1937, except that in the instant case a transmission line which is an efiective odd number of quarter wave lengths in length is utilized in place of the artificial line or wave filter of Crosby.
  • a further improvement is here included relating to the variable impedance tubes terminating the .line.
  • My invention not only eliminates this difliculty but also results in improved operation in a manner to be hereinafter described.
  • a further object is to provide means for modulating a radio frequency carrier which favors the higher modulating frequencies and so compensates for normal high frequency attenuation 20 in the modulator amplifier.
  • a still further object of my invention is to provide means for utilizing the impedance-inverting characteristic of a quarter wave resonant line for the purpose of modulating a radio fre- 25 money carrier.
  • Another purpose is to provide means for connecting one or more thermionic tubes across a quarter wave line so that a very high impedance is presented to the line by the tube or tubes.
  • a further purpose is to provide means for varying the impedance of a tube so connected in accordance with a modulating signal.
  • a further object is to provide a simplified modulating device for a high frequency transmitter. 35
  • a source of radio frequency energy is indicated at i, which may' be an oscillator or a power amplifier.
  • the output from this source is coupled by any convenient means to a first transmission line 5
  • a quarter wave line may be used to couple unequal impedances which-are connected across its terminals. This characteristic is utilized in my invention to couple the relatively high impedance source of carrier frequency to the relatively low impedance of a load, which may be an antenna, a'transmission line, or any other utilization device, the impedance of which is represented in the diagram by resistor IS.
  • a further well-known characteristic of a quarter wave line is that when a constant voltage is applied to its input, the current through its load is constant regardless of the value of the load impedance.
  • E the conditions at the load
  • I the conditions at the load
  • Z the loadimpedance
  • Voltage variations across an antenna cause variations in the radiated en- .ergy, which is the condition obtained in amplitude modulation. It follows therefore that in a circuit of this nature amplitude modulation may be accomplished by varying the load impedance of a quarter wave transmission line.
  • a quarter wave line While I prefer to use a quarter wave line, the operation of my device and the theoretical discussion here presented is not limited to such a line, but may also be applied to a line any odd number of quarter wave lengths long, such as A or At ultra high frequencies, the length of a quarter wave line may be such as to make it desirable to use a wave line, or even longer.
  • a quarter wave line therefore, in effect provides regulation between a constant voltage input and its load. If this were not so, no modulation could be accomplished, for the constant input would.
  • a series resistance between a constant voltage source and a variable load serves a similar purpose, but consumes energy.
  • the quarter wave method here ative values of the terminating impedancs.
  • a second quarter wave line 53 consisting of two similar hollow conductors I and 8 is connected at an angle to the first quarter wave line 5
  • the second line has a shorting bar ll connected across its extremities. Consequently there is a voltage node at this point, and a voltage maximum at the point of junction with the first line, which results in its presenting a very high impedance across the load.
  • the mid-point of shorting bar H is at zero radio f requency potential, and is consequently grounded.
  • a third quarter wave line 55 is now to be considered. Like the first two, it also consists of two hollow copper conductors 45 and 41 which are connected at the junction point of the first and second lines to form an extension of the former.
  • the cathode leads 5'! and 59 may be consideredas an extension of conductors 45 and 41, and thus a part of the resonant circuit 55. This is true because the cathodes are fioatingj that is, they are ungrounded and carrier freq ency potentials appear on them out of phase with respect to each other.
  • and 23 are connected across the extremities of the third quarter wave line 55. These tubes are preferably of the watercooled, external-anode type, such as the RCA 891. Their anodes 25 and 21 are connected together and grounded. This serves two important purposes. The first is that no insulation is necessary for the cooling system. The secondis that, because of the construction which commonly makes the anode the outer shell of the tube, a very short ground connection is obtainable.
  • the electron-emissive cathodes 33 and 35 are energized by a source I3 which is preferably an A. C. or D. C. generator. One terminal of the generator is grounded. The first terminal of cathode 35 is connected to the remaining generator terminal by a conductor 11 which is within the hollow tubes 9 and 45. The first terminal of cathode 33 is similarly connected to the generator by a conductor [5 within the'hollow members I and 41. The same terminal of each cathode is also bypassed to the extremities of line 55 by two capacitors 31 and 39. The remaining terminal of each cathode is connected to said extremities of line 55, thus completing the cathode heating circuit to generator I3 by means of the parallel members of lines 53 and 55.
  • a source I3 which is preferably an A. C. or D. C. generator.
  • One terminal of the generator is grounded.
  • the first terminal of cathode 35 is connected to the remaining generator terminal by a conductor 11 which is within the hollow tubes 9 and 45.
  • the two grids 29 and 3! are connected together by means of an inductor 43, which has such a value that at the carrier frequency a shunt anti-resonant circuit is formed with the grid-anode capacity of tubes Hand 23.
  • an inductor 43 which has such a value that at the carrier frequency a shunt anti-resonant circuit is formed with the grid-anode capacity of tubes Hand 23. The result of this is that at the carrier frequency there is an extremely high impedance between grid and anode, between grid and ground, and betweencathode and ground.
  • the tube impedance represented by the cathodeground. impedance, approaches infinity in the manner of an anti-resonant circuit, and is no r longer limited by the impedance represented by the interelectrode capacities.
  • each cathode is oscillating at carrier frequency, therefore a voltage is induced on each grid equal to the instantaneous potential of its associated cathode multiplied by the ratio of the grid-anode impedance to the cathode-anode impedance. This value is slightly less than unity because the antiresonant circuit makes the grid-anode impedance extremely high with respect to the grid-cathode impedance. Thus the grid potential at any instant approximately equals the associated cathode potential.
  • a mid-tap connection 49 is provided on inductor 43 which is connected to one terminal of a source of modulation frequency 4 I, preferably a video amplifier.
  • the remaining terminal of said source is connected to ground through a bias battery 6
  • is superimposed on the radio frequency potential of the grids 29 and 3
  • the tube impedance therefore becomes very low across the output terminals of quarter wave line 55. Line 55 is thus equivalent to line 53 and its loading effect across 19 is negligible.
  • a negative impulse of modulating voltage is superimposed on the grids,
  • the antenna is short circuited and the load impedance presented to the amplifier tubes is so high that substantially no power is delivered to the load or the modulator tubes. will likewise absorb no power at all from the antenna since they present an extremely high shunt impedance to the antenna.
  • the modulator tubes cathodes, or leads may be introduced within quarter wave section 5
  • a radio frequency oscillator When a radio frequency oscillator is coupled into quarter wave line 5
  • a quarter wave line tuned slightly above or below resonance no longer presents a pure resistive load at its input terminals, but in the manner of all tuned circuits becomes reactive on either side of resonance.
  • the value of the reactive component varies with the load impedance, and cunsequently by a proper choice may be made to detune the oscillator in a manner which will tend to compensate for the undesired frequency modulation.
  • a further important feature of my invention is that an unusually high impedance from grid to ground has been attained by the use of the resonant grid circuit. Without this resonant circuit, the effective tube impedance across the line could never be any greater than that presented by the inherent grid-cathode capacity. At higher frequencies, this impedance is usully quite low, and therefore the reflected impedance across the antenna due to the modulator tubes would be prevented from approaching zero, and the percent modulation obtainable would be seriously restricted. My invention, however, completely eliminates this difiiculty and 100% modulation has been obtained, substantially fiat over a very wide range of modulation.
  • second impedance-inverting means connected across said utilization device, a pair of thermionic tubes having cathodes, grid and anode electrodes terminating said second impedance-inverting means, means anti-resonant at carrier frequency interconnected with said grid electrodes, and means including a source of modulating potentials for varying the impedance of said thermionic tubes whereby the impedance presented to said utilization device by said second impedance-inverting means is varied by said modulating potentials.
  • a high frequency modulated carrier system comprising a source of carrier currents, a load impedance, 9. first transmission line substantially an odd number of quarter wave lengths long for matching the impedance of said sourceto said load impedance, means for causing amplitude modulation ofisaid carrier frequency at said load impedance which includes a second transmission line substantially an odd number of quarter wave lengths long, a pair of thermionic tubes having anode, grid and cathode'electrodes terminating said second transmission line, said cathode electrodes being a continuation of said second transmission line, an inductor interconnected with said 75' 0 grid electrodes being anti-resonant at carrier frequency, and means intermediate the ends of said inductor for impressing modulating potentials on said grids.
  • a high frequency modulated carrier system comprising a source of carrier currents, a load impedance, a first transmission line substantially an odd number of quarter wave lengths long for matching the impedance of said source to said load impedance, means for causing amplitude modulation of said carrier frequency currents at said load impedance which includes a second transmission line substantially an odd number of quarter wave lengths long connected across said load impedance, a pair of thermionic tubes having cathode, grid, and anode electrodes, said second transmission line terminating at said cathode electrodes, said anode electrodes being grounded, an inductor interconnected with said grid electrodes being anti-resonant at carrier frequency, and means intermediate the ends of said inductor for impressing modulating potentials on said grids.
  • a high frequency modulated carrier system comprising a source of carrier frequency currents, a load impedance, a first transmission line substantially an odd number of quarter wave lengths long transferring energy from said source to said load impedance, means for causing amplitude modulation of said carrier frequency currents at said load impedance which includes a second transmission line substantially an odd number of quarter wave lengths long connected across said load impedance, a pair of thermionic tubes having anode, grid and cathode electrodes terminating said second transmission line, means interconnecting said second transmission line and said cathodes whereby said cathodes assume the instantaneous potential of the adjacent portion of said second transmission line, means grounding said anode electrodes, an inductor interconnected 'with said grid electrodes which is resonated at carrier frequency by the inherent shunt grid-anode capacity, and means intermediate the ends of said inductor for impressing modulating potentials on said grids.
  • a source of carrier currents an eifective load impedance, a first transmission line substantially an odd number of quarter wave lengths long for transferring energy from said source to said effective load impedance, means for varying said eifective load impedance in accordance with a modulating signal, said means comprising a second transmission line substantially an odd number of quarter wave lengths long, a pair of thermionic tubes terminating said second transmission line, said tubes having anode, grid and cathode electrodes, means interconnecting said cathodes to said second transmission line, said anode electrodes being grounded, an inductor antiresonant at carrier frequency interconnected with said grid electrodes, and means intermediate the ends of said inductor for impressing in phase modulating potentials on said grids whereby the resultant variation of input impedance of said tubes causes said effective load impedance to vary in inverse proportion.
  • a source of carrier currents an effective load impedance
  • a first transmission line consisting of hollow tubular conductors substantially an odd number of 'quarter Wave lengths long for transferring energy from said source to said load impedance
  • means for varying said load impedance in accordance with a signal which includes a second transmission line consisting of a similar pair of hollow tubular conductors substantially an odd number of quarter wave lengths long, a pairof thermionic tubes terminating said second transmission line, said tubes having an electron-emissive cathode, grid and anode electrodes, a source of cathode-energizing potential, a third transmission line consisting of hollow tubular conductors substantially an odd number of quarter wave lengths long connected across said load impedance, means within said second and third transmission lines for interconnecting said cathode electrodes and said source of cathode-energizing potential, means grounding said anode electrodes, an inductor anti-reson
  • a high frequency modulated carrier system comprising a source of carrier currents, a load impedance, a first resonant transmission line consisting of hollow tubular conductors substantially an odd number of quarter wave lengths long whereby carrier frequency currents are coupled from said source into said load impedance, a variable impedance shunted across said load impedance which includes an impedance-inverting device, and a pair of thermionic tubes having cathode, grid and anode electrodes, anti-resonant means interconnecting said grid electrodes, a source of modulating potential and means including said anti-resonant means and said grid electrodes for varying the tube impedance by said modulating potential, whereby said inverting means impresses said variations across said load impedance.
  • a high frequency modulated carrier system comprising a source of carrier currents, a load impedance, a first transmission line substantially an odd number of quarter wave lengths long for transferring carrier energy from said source to said load impedance, means for causing amplitude modulation of said carrier frequency currents at said load impedance which includes a number of quarter wave lengths long shunted across said load impedance.
  • thermionic tubes having cathode, grid and anode electrodes, said second transmission line terminating at said cathode electrodes, anti-resonant means interconnecting said grid electrodes, and means including a source of modulating potential for varying the impedance of said thermionic tubes whereby the shunt impedance of said second transmission line across said load impedance varies according to a signal.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Transmitters (AREA)
  • Microwave Amplifiers (AREA)
US187618A 1938-01-29 1938-01-29 Radio signaling system Expired - Lifetime US2211003A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL58874D NL58874C (es) 1938-01-29
BE432342D BE432342A (es) 1938-01-29
US187618A US2211003A (en) 1938-01-29 1938-01-29 Radio signaling system
GB3154/39A GB524416A (en) 1938-01-29 1939-01-30 Improvements in or relating to modulated carrier wave transmitters

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US187618A US2211003A (en) 1938-01-29 1938-01-29 Radio signaling system

Publications (1)

Publication Number Publication Date
US2211003A true US2211003A (en) 1940-08-13

Family

ID=22689732

Family Applications (1)

Application Number Title Priority Date Filing Date
US187618A Expired - Lifetime US2211003A (en) 1938-01-29 1938-01-29 Radio signaling system

Country Status (4)

Country Link
US (1) US2211003A (es)
BE (1) BE432342A (es)
GB (1) GB524416A (es)
NL (1) NL58874C (es)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2419564A (en) * 1943-06-10 1947-04-29 Gen Electric Radio transmitter-receiver switching system
US2452912A (en) * 1942-06-10 1948-11-02 Rca Corp Circuit for improving oscillator stability
US2468237A (en) * 1947-05-24 1949-04-26 Raytheon Mfg Co Modulation apparatus
US2523209A (en) * 1945-02-06 1950-09-19 Csf Method of and means for the modulation of ultrashort waves
US2523311A (en) * 1939-07-29 1950-09-26 Int Standard Electric Corp Coupling means between radio stages
US2547378A (en) * 1945-03-22 1951-04-03 Robert H Dicke Radio-frequency mixer
US2554107A (en) * 1944-07-26 1951-05-22 Hartford Nat Bank & Trust Co Push-pull mixing circuit
US2574868A (en) * 1946-10-18 1951-11-13 Rca Corp Electron discharge tube circuit arrangement
US2582726A (en) * 1943-03-27 1952-01-15 Hartford Nat Bank & Trust Co Mixing circuit arrangement
US2591982A (en) * 1941-07-30 1952-04-08 Hartford Nat Bank & Trust Co Superheterodyne receiver for very short waves
US2591821A (en) * 1945-11-29 1952-04-08 Us Navy Modulator circuit
US2595997A (en) * 1943-10-27 1952-05-06 Hartford Nat Bank & Trust Co Receiver for short waves

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2523311A (en) * 1939-07-29 1950-09-26 Int Standard Electric Corp Coupling means between radio stages
US2591982A (en) * 1941-07-30 1952-04-08 Hartford Nat Bank & Trust Co Superheterodyne receiver for very short waves
US2452912A (en) * 1942-06-10 1948-11-02 Rca Corp Circuit for improving oscillator stability
US2582726A (en) * 1943-03-27 1952-01-15 Hartford Nat Bank & Trust Co Mixing circuit arrangement
US2419564A (en) * 1943-06-10 1947-04-29 Gen Electric Radio transmitter-receiver switching system
US2595997A (en) * 1943-10-27 1952-05-06 Hartford Nat Bank & Trust Co Receiver for short waves
US2554107A (en) * 1944-07-26 1951-05-22 Hartford Nat Bank & Trust Co Push-pull mixing circuit
US2523209A (en) * 1945-02-06 1950-09-19 Csf Method of and means for the modulation of ultrashort waves
US2547378A (en) * 1945-03-22 1951-04-03 Robert H Dicke Radio-frequency mixer
US2591821A (en) * 1945-11-29 1952-04-08 Us Navy Modulator circuit
US2574868A (en) * 1946-10-18 1951-11-13 Rca Corp Electron discharge tube circuit arrangement
US2468237A (en) * 1947-05-24 1949-04-26 Raytheon Mfg Co Modulation apparatus

Also Published As

Publication number Publication date
NL58874C (es)
GB524416A (en) 1940-08-06
BE432342A (es)

Similar Documents

Publication Publication Date Title
US2211003A (en) Radio signaling system
US2326314A (en) Frequency modulation
US2426295A (en) Frequency modulation system with crystal oscillator
US3196368A (en) Wide angle phase shifter or modulator
US2077223A (en) Modulation system
US2393785A (en) Carrier modulation
US1947003A (en) Oscillation generation
US2346800A (en) Wave length modulator
US2347458A (en) Frequency modulation system
US2278429A (en) Reactance tube modulation
US2263276A (en) Modulated carrier wave transmitter
US2296056A (en) Frequency modulation receiver
US2383848A (en) Reactance control circuit
US2271519A (en) Neutralizing system
US2143864A (en) Wide range beat frequency generator
GB485959A (en) System for amplitude modulation employing impedance inversion for high-frequency electric signalling
US2027975A (en) Frequency modulation
US2443746A (en) Tube reactance and modulator
US2476803A (en) High stability receiver circuit
US2255476A (en) High efficiency amplifier
US2566405A (en) Frequency modulation
US2509280A (en) Cathode-driven oscillator
US1986632A (en) Cathode ray tube oscillator
US2510787A (en) Variable reactance circuit
US2097896A (en) Amplifying arrangement