US2261606A - Mixer tube circuit - Google Patents

Mixer tube circuit Download PDF

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Publication number
US2261606A
US2261606A US293018A US29301839A US2261606A US 2261606 A US2261606 A US 2261606A US 293018 A US293018 A US 293018A US 29301839 A US29301839 A US 29301839A US 2261606 A US2261606 A US 2261606A
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United States
Prior art keywords
grid
control
potential
local oscillator
oscillator
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Expired - Lifetime
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US293018A
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English (en)
Inventor
Steimel Karl
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Telefunken AG
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Telefunken AG
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Publication date
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/22—Automatic control in amplifiers having discharge tubes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/06—Transference of modulation from one carrier to another, e.g. frequency-changing by means of discharge tubes having more than two electrodes
    • H03D7/10—Transference of modulation from one carrier to another, e.g. frequency-changing by means of discharge tubes having more than two electrodes the signals to be mixed being applied between different pairs of electrodes

Definitions

  • the grid of a multi-grid mixer tube and to which the alternating input potential (high-frequency potential) is applied can be adapted for variable amplification control, and more especially as exponential grid just as in the case of an exponential tube. It is desirable to increase the limited controllability of such a mixer tube, i. e. to decrease the requirement in control potential. This would be possible if, aside from the control at the input grid, also the amplitude of the superposed alternating potential applied to the grid of the local oscillator, or the grid biasing potential of the grid of the local oscillator would be controlled. Both types of control are complicated as regards the circuits and difficult tov realize since frequency distortions occur at the control performance.
  • the control at the grid of the local oscillator appears to be simpler but still more diiicult than at the input grid since the grid of the local oscillator carries current. Furthermore the change of the grid current causes a change of the damping of the oscillatory circuit of the local oscillator and hence, a frequency distortion.
  • the invention affords a new and simpler way Without any particular requirement in circuit means and which resides substantially in a different design of the tube.
  • Underlying the invention is a known mixer tube with a grid for the alternating input potential which grid is so designed for variably controlling the amplification and this mixer tube also has a non-controlled grid for the alternating potential of the local oscillator.
  • the mixer tube is so designed and/or so operated that when the grid biasing potential of the input grid becomes more negative, the alternating potential of the local oscillator which remains constant controls but partially the plate current.
  • the invention resides in that the control affected by the grid for the alternating potential of the local oscillator is diierent throughout the length of the grid in the same manner in which the control by the input grid differs.
  • Figure 1 shows a mixer tube circuit in accordance with the invention
  • Figures 2 and 3 are oscillator gridpotential-plate 55 current curves for two conditions of operation which will serve to explain the invention.
  • the circuit is shown to utilize a tube having four grids. 'I'he incoming high-frequency is impressed across the highfrequency circuit H upon the grid situated next to the cathodei
  • the second grid and fourth grid are screen grids having constant direct potential (in place of the series resistor R a voltage divider may at first be considered)
  • the third grid has applied thereto from the grid of the built-in oscillator, with the oscillatory circuit O, the alter' nating potential of the local oscillator.
  • the anode lead-in contains the band filter Z for the intermediate frequency.
  • the amplification of the mixing performance can already be controlled by varying the biasing potential Ugi of this grid. Since in View of freedom from distortion certain conditions exist for the bend of the characteristic such a method affords controlling of the amplification only at the ratiorof about 1:50. But it is aimed at acontrol ratio of 1:300
  • the last mentioned measure could be carried out again in two different ways, namely in shifting the working point for the local alternating potential likewise on a suitable characteristic, or and this was found to be most suitable and represents the feature of the first mentioned mode of construction according to the invention, in that solely through proper dimensioning of the tube employed it is accomplished that simply by varying the biasing potential of the rst grid the modulation ratio of the third grid is so varied at the same time that at lower grid biasing potential of the first grid (high steepness) the modulation ratio becomes as high as possible, and at high grid biasing potential (small steepness) of the first grid said modulation ratio becomes as low as possible.
  • the tube is conceived as being divided into two or a greater number of partial systems such as is usually done in the case of tubes yhaving a variable mu or amplification factor whereby the said partial systems are considered as being arranged side by side along the cathode.
  • control ranges are obtained, in the manner known in the-case of variable mu orexponential tubes, by'designing the third or oscillator grid to possess a variable mu or amplification factor, and in practicethe simplest-way is toy provide such grid with different pitches just as in the case of exponential tubes.
  • control range on the third grid can likewise be obtained by cutting out one or several grid turns and in accordance with'thefabove that turn is to be cut out at the placel oftheelectron path which corresponds with the gap on thefirst grid.
  • the second mode of construction in accordance with the invention resides in applying the' nating potential of the local oscillator thatI at' the increase of the control range of the local oscillation grid, due to an increasing screen grid potential during the downward control of the mixer tube at the input grid, the local oscillator potential only partially controls this control range.
  • the use of a screen grid series resistance in place ⁇ of a potentiometer gives the following result:
  • the application of the gliding screen grid potential reduces the controllability of a multigrid mixer tube though not quite as eifective as in the case of the earlier tubes it is desired to have a further reduction in control potential required and therewith an improvement in the controlling property of the tube which can be achieved with the second mode of construction according to the invention (or with the rst one).
  • the screen grid potential owing to a higher negative biasing potential at the input grid
  • the range of control of the local oscillation grid increases in fact.
  • the alternating potential of the local oscillator is so chosen that at an increase in the range of control of the local oscillation grid the plate current is no longer completely controlled by the alternating potential of the local oscillator (such as in Figure 3), there appears at a downward control of the ampliiication at the input grid at the same time a reduced modulation property of the local oscillation grid and hence a further decrease of the mixer amplication.
  • the controlling property hence, is increased.
  • the third possibility resides in applying at the same time the two different modes of construction according to the invention, namely the special design of the local oscillation grid and the above-explained dimensioning of the alternating potential of the local oscillator in employing the gliding screen grid potential.
  • the principle of the gliding screen grid potential can be applied without the necessity of a larger requirement as regards the control potential.
  • the invention may be applied not only to the mixer tube shown in Figure 1 but also to other types of multiple grid mixer tubes. Furthermore it may be practiced not only in connection with superheterodyne receivers but generally in mixer tubes serving for the mixing of two frequencies.
  • a tube provided with at least a cathode, a signal control grid, an oscillator grid and an anode, each of said grids being provided with low and high mu sections and corresponding sections of said grids being disposed in cooperative relation with one another, means for applying a variable bias to the control grid for controlling the amplication of the system, mea-ns for impressing a signal frequency on the control grid, a local source of oscillations for impressing a constant voltage of a predetermined frequency on the frequency oscillator grid, and a utilization circuit responsive to the combined frequency connected to the anode, the arrangement being such that with increased control grid bias to reduce the amplification the control action of the local oscillator grid becomes less eifective in producing the conversion to the combined frequency.
  • a screen grid is interposed between the signal and oscillator grids and a voltage dropping resistor is connected to said screen grid, so that with increased bias on the control grid, the applied screen grid voltage is increased to render the control action of the oscillator grid more ineifective.
  • a tube provided with at least a cathode, a signal control grid, a screen grid, an oscillator grid and an anode arranged in the order named, each of the control and oscillator grids having a variable mu factor, means for applying a variable bias to the control grid for controlling the amplication of the system, means for impressing a signal frequency on the control grid, a local source of oscillations for impressing a constant voltage of a predetermined frequency on the frequency oscillator 4 grid, a utilization circuit responsive to the combined frequency connected to the anode, and meansv for applying operating voltage to the screen grid through a resistor, the arrangement being such that with increased control grid bias to reduce the amplification the control action of the local oscillator grid by reason of its variable mu factor and the increased screen grid potential becomes less effective in producing the conversion to the combined frequency.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Superheterodyne Receivers (AREA)
US293018A 1938-09-28 1939-09-01 Mixer tube circuit Expired - Lifetime US2261606A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2261606X 1938-09-28

Publications (1)

Publication Number Publication Date
US2261606A true US2261606A (en) 1941-11-04

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ID=7992832

Family Applications (1)

Application Number Title Priority Date Filing Date
US293018A Expired - Lifetime US2261606A (en) 1938-09-28 1939-09-01 Mixer tube circuit

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US (1) US2261606A (fr)
FR (1) FR861280A (fr)

Also Published As

Publication number Publication date
FR861280A (fr) 1941-02-05

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