US2138653A - High efficiency modulating and amplifying system - Google Patents

High efficiency modulating and amplifying system Download PDF

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Publication number
US2138653A
US2138653A US171675A US17167537A US2138653A US 2138653 A US2138653 A US 2138653A US 171675 A US171675 A US 171675A US 17167537 A US17167537 A US 17167537A US 2138653 A US2138653 A US 2138653A
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United States
Prior art keywords
tube
circuit
source
amplifier
carrier
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Expired - Lifetime
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US171675A
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English (en)
Inventor
Robert B Dome
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General Electric Co
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General Electric Co
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Priority to NL90377D priority Critical patent/NL90377B/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US171675A priority patent/US2138653A/en
Priority to GB31114/38A priority patent/GB521999A/en
Priority to FR845283D priority patent/FR845283A/fr
Priority to DEI62772D priority patent/DE763872C/de
Application granted granted Critical
Publication of US2138653A publication Critical patent/US2138653A/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
    • H03F1/04—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in discharge-tube amplifiers
    • H03F1/06—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in discharge-tube amplifiers to raise the efficiency of amplifying modulated radio frequency waves; to raise the efficiency of amplifiers acting also as modulators

Definitions

  • My invention relates to modulating and amplifying systems for radio transmitters and like apparatus, and particularly to methods of and means for increasing the efiiciency and lowering the first cost and operating cost of modulator and amplifier devices employed, for example, in high power radio transmitters.
  • Amplifiers of the linear or similar type have been commonly employed in radio transmitters but have been, at times, replaced by other types of amplifiers, particularly in high power installations since the linear amplifier has not in general been capable of operation at more than a relatively low overall efliciency.
  • I provide means whereby, in a radio transmitter or like apparatus for the transmission or a modulated wave of carrier frequency, an amplifying device or tube operates into a variable modulated load, a portion of the load being radiated on an antenna or consumed in any suitable load circuit, and another portion of the load being rectified, the rectifier current being fed back to replenish the power supply means supplying D. C. power to the amplifying device.
  • the rectifying means which provides the feedback of power to the amplifying device is controlled by a quarter-wave transmission line or network section connected in the output circuit of the amplifying device.
  • a similar rectifying means is shunt arranged in a coupling circuit provided between the output circuit of the amplifying device and the antenna circuit or other load consuming work circuit.
  • Fig. 1 is a diagrammatic representation of a radio transmitter in which my invention has been embodied
  • Fig. 2 is a diagrammatic representation of .a radio transmitter embodying a modification of my invention.
  • Fig. 1 the numeral I indicates a space discharge device or tube which in the present embodiment of my invention is a power amplifier for modulated carrier waves.
  • This tube may be, for example, of the 207 type.
  • Tube l is arranged to be shunt fed through a choke 2 from a source of anode potential 3, and the anode 4 of the output circuit 5 of the tube is coupled through a blocking capacitor 6 to an oscillatory circuit 1 comprising an inductance 8 resonating with a capacitor 9 at the operating frequency.
  • An antenna H3 is coupled to inductance 8 through a coupling coil H and is tuned by an antenna capacitor l2.
  • choke 2 has such a value of inductance that the choke inductance resonates, at the operating frequency, with the capacity of tube l to ground, and with the capacity of connecting wires and the stray capacity of capacitor 6 to ground, the reason for this requirement being that it is essential that the combination 8, 9 be truly resonant and not reactive.
  • a quarter-wave section of network [4 which may comprise, for example, an inductance l5 and connected thereacross, two capacitors l6 and I! in series.
  • the far end 29 of the quarter-wave network section It is connected through a lead 2'! to the anode 22 of a modulatorrectifier space discharge device or tube 23.
  • the cathode 24 of tube 23 is connected through a lead 25 to the positive terminal 26 of anode potential source 3, and the grid 27 of this tube is connected to cathode .25 through, preferably, a resistor 28, the secondary 29 of an audio frequency transformer 33 the primarytl of which is connected to a source (not shown) of modulating frequencies, and a source of grid bias potential 32.
  • a choke 33 is connested in shunt with capacitor E5 to carry the direct current output of modulator-rectifier tube 23.
  • the output circuit of the modulator-rectifier tube 23 thus includes anode 22, cathode 24, lead 25 connecting cathode 24 to positive terminal 25 of anode potential source 3, potential source 3 to the cathode it of tube 8, choke 33 bypassing capacitor it; of the network section IQ, inductance E5 of the network section i l, and lead 2! connecting far end terminal 2% of network section Hi to anode 22.
  • a choke 3% may in certain instances be shunted across capacitor ll of quarter-wave network section it, for a purpose to be explained hereinafter.
  • the input circuit 35 of tube l comprises grid or control electrode 36, an optional grid leak 3i and bypass condenser 38, a grid oscillatory circuit 3 comprising inductance lil tuned by capacitor ll, a grid bias potential source t2, and cathode it which is at ground potential.
  • this circuit is coupled to the anode circuit 43 of an exciter tube 44, to the input circuit 45 of which is coupled a source (not shown) of carrier frequency, and which is adapted to be plate modulated through an audio transformer 46 coupled to the source of modulating frequencies.
  • the modulating frequency should be so phased on audio transformers 30 and 56 that the grid of tube 23 goes negative when the modulation is positive on the excitation to tube
  • the system above described is set up for operation as follows: Assuming that a carrier wave is being impressed on tube l, the capacitor is is first short-circuited, thus connecting the lower end of plate oscillatory circuit 1 directly to the cathode of tube 1 and eliminating effectively, for the time being, the quarter-wave network section I4 from the output circuit of the tube. The loading on oscillatory circuit '3 is next adjusted, by adjustment of the coupling to the antenna, until the loading is correct to provide an antenna power equal to four times the desired carrier power.
  • Tube 23 is then biased temporarily beyond cutoff, and with the anode-cathode circuit of the latter tube thus made non-conducting, the elements of the quarter-wave network section M are'adjusted until the same 16 kw. antenna power is again obtained.
  • This result in antenna power is obtainable for the reason, in general, that if the far end terminating impedance of a quarterwave network section is infinity, the near end impedance is zero.
  • the far end ill] of network section I4 is connected to the anode 22 of tube 23 which is now nonconducting, the terminating impedance of the far end 29 is infinity and the impedance of the near end 13 is therefore zero. Since the near end impedance of the network is zero, conditions in the output circuit of amplifier i are the same as with oscillation circuit 1 connected directly to cathode it by a short-circuit across capacitor it of network it.
  • tube 23 The negative bias on tube 23 is next decreased slowly so that this tube becomes active and begins to rectify the radio frequency voltage across capacitor ill, or across the far end 20 of the quarter-Wave network section M.
  • This action of tube 23 causes the far end impedance of network section it to decrease and the near end impedance correspondingly to increase,
  • the impedance thus introduced, in series with the 2640 ohm load line, in the output circuit 5 of amplifier l is resistive and does not detune the anode circuit of this tube provided the inductance of'choke 2 has the value above mentioned.
  • the lowering of the negative bias of tube 23, and consequent increase in the total impedance in circuit 5, is continued until the antenna power is down to four kw., which as above mentioned is the antenna power corresponding to the unmodulated or carrier conditions of the transmitter. Since, with the antenna power down to four kw., or carrier conditions in the present case, the total plate swing of amplifier l is still approximately the same as before in the 100 per cent modulation conditions of the transmitter, because the excitation to tube l is so arranged that under carrier conditions the plate voltage is given its utmost excursion, therefore the rectifier-modulator tube 23 new places across the far end 20 of the quarter-wave network section l d a load equal to the load across the circuit 1, or 2640 ohms.
  • the amplifier l under these conditions works into an effective load of 5280 ohms. may vary slightly because the plate swing of amplifier l is slightly increased for increased load lines, and instead of 5280 ohms the value may be about 5600 ohms.
  • the total output of the tube l is now eight kilowatts and the plate current is 0.76 ampere. The efficiency so far as the tube is concerned is now 75 percent Of the total eight kilowatts output, four kilowatts go to the antenna. The other four. kilowatts are rectified by tube 23.
  • the modulating audio frequency is so phased on transformer 30 of modulator-rectifier tube 23 and on transformer of the exciter tube 44 that the grid 2'! of tube 23 goes negative to the cut-off point when the modulation is positive on the excitation to amplifier I, and that, therefore, at 100 per cent modulation tube 23 does not rectify any of the modulated R. F. across capacitor ll of the network section M.
  • the impedance of the far end 20 is infinity and that of the near end I3 is zero. Under these conditions the network Id does not provide any impedance in the output circuit 5 of amplifier I, as before explained 1n connection with the setting-up of the system.
  • the grid bias on modulator-rectifier tube 23 is adjusted initially at such a value that rectification of the radio frequency oscillations across capacitor I! of network l4 occurs sufficient to cause one-half of the total output of amplifier l (8 kilowatts in the present case) to be fed back ,to the plate supply source of the amplifier.
  • the operation of modulator-rectifier tube 23 is such as to cause a feed-back to the plate current of amplifier i appropriate to the particular condition of positive modulation.
  • R1 the far end impedance (resistance).
  • Rz the near end impedance (resistance).
  • the current, I, on peaks of modulation, W0, is that due to five per cent of the peak power, or
  • a system in accordance with my invention as illustrated in Fig. 1 employing glass amplifier tubes, for example, of the 806 type, it is possible to obtain approximately half the class C rating of the tubes as carrier power with a resulting saving in tube cost over previous systems.
  • a single 806 amplifier tube when incorporated in the present system yields a carrier power of approximately 225 watts.
  • the modification of my invention illustrated in Fig. 2 is similar to the embodiment illustrated in Fig. 1 in that modulated carrier waves are impressed on an antenna circuit 41 comprising an antenna 48, an inductance 49, and a tuning capacitor 50, from an amplifier tube 5
  • the system illustrated in Fig. 2 is further similar to that of Fig. 1 in that the amplifier 5
  • a modulator-rectifier device or tube 54 to add to the power supply which furnishes D. C. power to the amplifier.
  • a quarter-wave network section is not employed, in connection with the modulator-rectifier tube, to obtain this result.
  • the amplifier output oscillatory circuit 55 is coupled to a resonant coupling circuit 56 comprising inductance 5'!
  • the modulator-rectifier tube 54 is connected in shunt with coupling circuits 56 and 6E.
  • the anode 64 of tube 54 is connected through lead 59 to the high potential side of the coupling circuits 55 and 6! and the cathode 65 is connected through a lead 65 to the positive terminal 5'! of a source (not shown) of anode potential for amplifier 5!,
  • Grid ill of the modulator-rectifier 54 is supplied from the source of modulating frequency through a circuit including lead 66, a source ll of bias voltage, and the secondary E2 of an audio transformer 13 the primary T4 of which is connected to the source of modulating frequency.
  • the circuits are so adjusted that with modulator-rectifier tube 54 biased beyond cut-01f (no plate current in this tube) for 100per cent modulation conditions, the antenna current is twice the antenna current under carrier conditions; under carrier conditions the load on the power amplifier 5 I is half as much, or the load resistance is twice as great, as under the condition of 100 per cent peaks of modulation.
  • the modulator-rectifier tube 54 takes onehalf the output of the power amplifier 5i and returns the power to the power supply of amplifier 5! in the form of direct current, similarly to the return of power to the amplifier as described in connection with the embodiment of my invention illustrated in Fig. 1.
  • the modulating frequency is so phased on the audio transformers (53 and 13 in Fig. 2) that the grid of the modulatorrectifier tube goes negative when the modulation is positive on the excitation to the amplifier tube.
  • the resistance Rs in turn appears across the tank as a resistance, R7, of a Value Since all of the reactances (Xs) are constant for a given circuit set-up, (26) may be written as k R,,R (27) Now R7 is the resistance load on the power amplifier 5i, and since under carrier conditions k2Ra R3, therefore under the latter conditions l( 2 a+ 2 a) i k312i 1 12, (28
  • a transmitting system comprising a source of carrier waves, a load circuit, an amplifier adapted to transfer energy between said source and said circuit and having an output circuit, a source of modulating potentials, means to modulate said carrier waves in accordance with said potentials, and a source of direct current for said output circuit, the method of operation which includes transferring a portion of the load in said output circuit to said load circuit, rectifying another portion of said output circuit load in accordance with said modulating potentials, and adding said rectified portion to the current in said output circuit from said direct current source.
  • a transmitting system comprising a source of carrier waves, a load circuit, an amplifying device adapted to transfer energy from said source to said circuit and having an anodecathode circuit, a source of modulating potentials, means to modulate said carrier waves in accordance with said potentials, and a source of direct current for said anode-cathode circuit, the method of operation which includes transferring under carrier conditions in said system a portion of the output of said amplifying device to said load circuit, rectifying another portion of said output in accordance with said modulating potentials, and adding said rectified portion to said direct current.
  • a source of carrier waves an amplifying device including an input circuit and an anode-cathode circuit, a load circuit, means to impress said carrier waves on said input circuit from said source, a source of modulating potentials, means to modulate said carrier waves in accordance with said potentials, a current source connected to said anode-cathode circuit to supply direct current thereto, a rectifying device, and means including said rectifying device to transfer under Y iii waves in accordance with said potentials, a source of direct current for said output circuit, and means to add to the current supplied by said direct-current source to said anode-cathode circuit in accordance with said modulating potentials, said last-named means including a quarter- Wave transmission line section connected in series in said output circuit and a rectifying device connected between said transmission line section and the positive terminal of said source of direct current.
  • a source of carrier waves an amplifying device including an output circuit, means to impress a modulated carrier wave on said device from said source, a source of modulating potentials, means to modulate said carrier waves in accordance with said potentials, a source of direct current for said output circuit, a transmission line section connected in series in said output circuit, a rectifying device connected between the far end of said section and the positive terminal of said direct current source to add current in accordance with said modulatingpotentials from the load in said output circuit to the current supplied to said output circuit from said direct current source, and means including said rectifier to cause under conditions of complete modulation of said carrier wave the near end impedance of said section to be substantially zero and under carrier conditions of said Wave the near end impedance of said section to have a value approximately that of the initial load impedance of said output circuit.
  • a source of carrier waves adapted to transfer energy from said source to said circuit and including an output circuit
  • means to impress said carrier waves on said device from said source a source of modulating potentials, means to modulate said carrier waves in accordance with said potentials, a source of direct current for said output circuit, and means to transfer under carrier conditions in said system a portion of the load in said output circuit to said load circuit and to add to the direct current supplied to said output circuit from said current source a direct current in accordance with said modulating potentials, said last-named current being derived from another portion of said output circuit load
  • said last-named means including a coupling circuit means between said output circuit and said load circuit and a rectifying device connected in shunt with said coupling circuit means and having a cathode connected to the positive terminal of said direct current source.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)
  • Transmitters (AREA)
US171675A 1937-10-29 1937-10-29 High efficiency modulating and amplifying system Expired - Lifetime US2138653A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
NL90377D NL90377B (enrdf_load_stackoverflow) 1937-10-29
US171675A US2138653A (en) 1937-10-29 1937-10-29 High efficiency modulating and amplifying system
GB31114/38A GB521999A (en) 1937-10-29 1938-10-27 Improvements in and relating to modulating and amplifying systems
FR845283D FR845283A (fr) 1937-10-29 1938-10-28 Perfectionnements aux systèmes de modulation et d'amplification en haute fréquence
DEI62772D DE763872C (de) 1937-10-29 1938-10-30 Anordnung zur Verbesserung des Wirkungsgrades der Endstufe eines modulierten Senders

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US171675A US2138653A (en) 1937-10-29 1937-10-29 High efficiency modulating and amplifying system

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Publication Number Publication Date
US2138653A true US2138653A (en) 1938-11-29

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US171675A Expired - Lifetime US2138653A (en) 1937-10-29 1937-10-29 High efficiency modulating and amplifying system

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US (1) US2138653A (enrdf_load_stackoverflow)
DE (1) DE763872C (enrdf_load_stackoverflow)
FR (1) FR845283A (enrdf_load_stackoverflow)
GB (1) GB521999A (enrdf_load_stackoverflow)
NL (1) NL90377B (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2436066A (en) * 1944-01-04 1948-02-17 Patelhold Patentverwertung Transmitter with anode voltage modulation
US2579542A (en) * 1945-09-18 1951-12-25 Winston H Bostick Pulse transformer circuit

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB262872A (en) * 1925-09-21 1926-12-21 Western Electric Co Ltd An improved modulating system for high frequency signalling

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2436066A (en) * 1944-01-04 1948-02-17 Patelhold Patentverwertung Transmitter with anode voltage modulation
US2579542A (en) * 1945-09-18 1951-12-25 Winston H Bostick Pulse transformer circuit

Also Published As

Publication number Publication date
GB521999A (en) 1940-06-06
FR845283A (fr) 1939-08-17
DE763872C (de) 1954-07-19
NL90377B (enrdf_load_stackoverflow)

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