DE824960C - Circuit for frequency stabilization - Google Patents

Description

To stabilize oscillators, it is known to use the beat frequency between the oscillator oscillations and to use that of a standard oscillator and derive a control voltage from the beat frequency.

The latter derivation can be effected in a number of ways. So is suggested among other things been to produce two voltages with the difference frequency, one mutual Have phase difference of o, o ° and these voltages are one of two in push-pull to supply switched mixing tubes existing system that has two states of equilibrium. Included under the influence of the vibrations imposed on the grids, either the one or the other of the tubes depending on an oscillator frequency that is too high or too low locked.

This device has the disadvantage that at least two mixing tubes are required, ao whose setting is difficult and which, due to their push-pull effect, not easily one Can supply control voltage to a reactance tube.

It has also been proposed to use the aforementioned ^{voltages shifted in phase by 90 0} for alternately charging and discharging a capacitor via diodes. This method has the disadvantage that, in view of the equality of the two voltages shifted in phase, it is very difficult to carry out and that a relatively large amount of energy is consumed.

The invention aims to provide a frequency stabilizer in which the aforementioned disadvantages are avoided.

The idea on which the invention is based

is as follows: If two voltages of the same frequency are impressed on the grilles of a mixer tube, the anode current will be maximum when these voltages are in phase and minimum when they are in antiphase. So if two of the beat vibrations; Voltages are derived which have a mutual phase difference of 90 ⁰ , and one of these voltages is ^{rotated again by 90 0} in phase, in such a way that the final phase of this voltage does not flip when the frequency difference between the oscillator to be stabilized and the standard oscillator has its sign changes, the two voltages, if they are applied to a mixing tube, make the anode current of this tube maximum or minimum, depending on whether the sign of the aforementioned frequency difference is positive or negative. A stabilizing control voltage can thus be taken directly from this anode current.

A constant phase shift of one of the two of the control tube to be pushed Beat vibrations can thereby be brought about according to one embodiment of the invention be that this oscillation is imposed on one of the grids of this tube via a capacitor and a diode is connected between this grid and the cathode with positive bias voltage, which only allows current to pass at such a negative grid voltage that the tube is completely or is at least almost locked.

Further features and details of the invention will become apparent from the following description, in which the invention is explained in more detail with reference to the drawing, for example.

Fig. Ι shows a simplified circuit diagram to I explain the principle of the invention;

2 shows a graphic representation of the course of some voltages;

Fig. 3 shows a detailed circuit diagram of an embodiment;

Fig. 4 shows a modification of the same.

In the circuit diagram according to FIG. 1, the two frequencies to be compared Z ₁ and f _{% are} fed to two mixer stages M ₁ and M _2. At the frequency Z _1, this feed takes place via a network phasenverdrehendes A, whereby the vibrations of this frequency, the mixer stages M ₁ and M ₂ with a mutual phase difference of approximately 90 reach ^{the 0th} The same phase difference then also occurs between the data supplied by M ₁ and M ₂ oscillations with _(beat frequency Z ₁ -Z _2. The last-mentioned, derived from M ₂ vibration is through a capacitor C ₂ to the third grid G _a a mixing tube B pressed If the sign of the beat frequency Z ₁ -Z _{2 is} reversed, the phase of the vibrations imposed on g _{3 changes} over 180 °.

The beat oscillations originating from M ₁ are pressed onto the grid g _{x of} the mixing tube B via a capacitor C _1. The cathode of this tube is given a positive bias voltage by means of a resistor W , and a diode D is _{switched on between the grid ^ 1} and the dead end of the resistor W , which only carries current when the potential of the grid g _{1 is} under the influence of The beat vibrations imposed on it becomes so negative η ₀ with respect to the cathode that the tube B is completely or almost completely blocked.

In FIG. 2, the curve of the voltage V ₁ supplied by M ₁ as a function of time and the course of the voltage v of the lattice ^ _{1 gl} applied, wherein the line V _D represents the magnitude of the positive cathode bias, at the same time the "threshold for the diode is. It results that v _gl is shifted by about 90 ⁰ with respect to V ₁ and is thus either in phase or in antiphase with the voltage on grid g ₃ , and further that the phase of the voltage v _gl does not flip when the sign changes from Z ₁ - ^ ₂ . It is therefore dependent on this sign whether the voltages on the two grids are in phase or in opposite phase, in other words whether the anode current of tube B is maximum or minimum. A control voltage R can thus be taken directly from the anode circuit of this tube.

The circuit described so far works due to the existing isolating capacitors C ₁ and C ₂ only at values of Z ₁ -Z ₂ , which are let through by the capacitors to a sufficient extent. A complete synchronism cannot be achieved with this.

A circuit in which this is the case, however, is shown in FIG. 3, which corresponds in principle to FIG and in which corresponding or equivalent parts are denoted by the same reference numerals.

The output voltage of network A , shifted in phase by 90 ⁰ , is fed to mixer diodes M ₁ and M ₂ via capacitors ι and 2, respectively, and this in the opposite sense, for reasons mentioned below. The oscillation with the frequency Z _{2 is} fed to these diodes via a transformer T, also in the opposite sense.

The beat frequency supplied by the diode M ₁ is fed to the grid g _{1 of} the mixing tube B via a resistor 3 and a capacitor C _1, the grid being connected to the cathode via a diode D and a cathode resistor W. The beat frequency supplied by the diode M ₂ passes via a resistor 4 and the capacitor C ₂ to the grid g _v which is connected via a resistor 5 to an intermediate point of the resistor W , so that g _{3 is} on average a little negative with respect to the cathode is.

So that the desired stabilization occurs even at very low beat frequencies, down to frequency zero, the mixer diodes M ₁ and M _{2 are designed} as a simple beat discriminator, in which the tube B works as a direct current amplifier, since the grid g _{x of} this tube

is connected to the two mixer diodes M ₁ and Af ₂ via high discharge resistances 6 and 7, respectively. Since these diodes are connected in opposition, the two DC voltage components occurring in them are balanced. If the beat frequency approaches too close to zero to be admitted by the isolating capacitor C ₁ to the grid g ₁ , the beat discriminator M ₁ M ₂ takes over the control effect until perfect synchronism is achieved.

Without this auxiliary device, the lowest cut-off frequency is that at which the capacitor C _{1 is} discharged again during part of the period by leakage currents through resistors that are intentionally or unintentionally arranged for this purpose. It is not necessary to use tube D as a direct current amplifier at low frequencies, since in this case the control voltage of the beat discriminator can be taken from the circuit even without this tube. This is shown in FIG. 4, for example.

The circuit shown in this figure corresponds essentially to that according to FIG. 3.

Only the two resistors 6 and 7 are not connected to the grid g _{t of} the tube B , but are led directly to the output terminal, to which the anode of the tube B is also connected, preferably via a resistor 8. A capacitor 9 is arranged to dissipate the alternating voltage components which reach the output terminal in this circuit via the resistors 6 and 7.

Claims (5)

PATENT CLAIMS: i. Circuit for frequency stabilization of an oscillator with the help of the oscillator voltage and a frequency-constant voltage formed beat frequency, from the two mutually phase-shifted auxiliary voltages are generated, characterized in that one of these two auxiliary voltages is subjected to such a phase shift that it corresponds to the sign of the Difference frequency with the other auxiliary voltage either in phase or in opposite phase is and that the control voltage is taken from a mixer tube to which the two auxiliary voltages are applied. 2. Circuit according to claim 1, characterized in that that between the grid of the mixer tube, which is pressed by an auxiliary voltage and the cathode of this tube is connected to a diode that is so big The threshold value is that it only conducts current at a grid voltage at which the mixer tube Is blocked. 3. Circuit according to claims 1 or 2, characterized in that the auxiliary mixer tubes, with which the two auxiliary voltages are generated, as a simple beat discriminator are switched. 4. A circuit according to claim 3, characterized in that the two auxiliary voltages are each fed to a grid of the mixing tube via separating capacitors and that one this grid is also connected to the two auxiliary mixer tubes via high resistances, in which the two auxiliary voltages are generated. 5. A circuit according to claim 3, characterized in that the two auxiliary voltages The grids of the mixer tube via separating capacitors and directly via resistors Output terminal of the circuit are supplied. Referred publications:
"Communications from research and operations of the television company, Berlin" 1st volume, issue 6, Dec. 1939, p. 215; German patent specification No. 881554. 1 sheet of drawings © 2557 12.