US2484107A - Oscillograph circuit to modulate a signal - Google Patents

Description

Oct. 11, 1949. M. MARON 2,484,107

OSCILLOGRAPH CIRCUIT 'IO MODULATE A SIGNAL Filed Sept. 21, 1946 771M (NVENTOR.

RTTORNEI' phase are applied to the terminals 13 and B.

Patented Oct. 11,1949 4 OSCILLOGRAPH CIRCUIT TO MODULATE A SIGNAL Meyer Maron, Passaic, N. J., assignor to Allen B. Du Mont Laboratories, Inc., Passaic, N. .L, a

corporation of Delaware Application September 21, 1946, Serial No. 698,486

This invention relates to a circuit for a polar coordinate oscillograph. It is particularly useful for modulating a signal by means of another signal without using tuned circuits or filters. It will operate over. a wide range of frequencies with little if any frequency discrimination, phase shift, or signal addition of modulating signal and signal to be modulated.

With this invention radial deflection of the circular sweep of a cathode-ray beam may be obtained by modulating the circular sweep with another signal.

The invention, may be understood from the description in connection with the accompanying drawing in which:

Fig.1 is a diagram of connections and elements illustrating an embodiment of the invention, and

Figs. 2 and 3 are diagrams showing, respectively, signals produced without and with this invention.

In the drawing, reference characters I, 2, 3 and 4 indicate pentodes that are alike. They are of the same size and have like characteristics, The pentodes l and 2 have their plates connected to a source of positive potential, not shown, through load resistance 5. The pentodes 3 and 4 have their plates connected to the same source of positive potential through load resistance 6.

The control grids of tubes 2 and 3 are negatively biased in the known way as shown by the negative sign n and are coupled by condensers and 8 respectively to input terminals A and A.

Balanced input signals of equal magnitude and 180 out of phase, that are to be modulated, are applied to the terminals A and A from which they are applied to the control grids of the tubes 2 and 3 respectively. These signals A and. A may be direct coupled or they may be resistance coupled from a source of such signals in the known way and are applied to the control grids of the tubes 2- and 3 by condensers 1 and 8- Signals of equal magnitude and 180 out of The signal applied at B is fed to the screen grids of the tubes 2 and 3 and the signal applied at B is fed to the screen grids of the tubes I and 4. In this way the transconductance of tubes 2 and 3 is changed and the signals A and A are modulated. The' signals at B which are applied to the screen grids of the tubes I and 4 prevent distortion of the signal outputs from tubes 2 and 3,

3 Claims. (Cl. 332-42) When the tubes l and 4 are not used the signals applied to the terminals A, A, are amplified by the tubes 2 and 3. These amplified signals are applied to the plates I5 and I5 and cause distortion of the modulated signals from tubes 2 and 3 as indicated in Fig. 2. When the tubes I and 4 are connected as shown, the signals applied at A, A are modulated Without appreciable distortion as shown in Fig. 3.

What is claimed is:

1. A device for modulating electrical signals which comprises a cathode-ray tube having a pair of deflecting plates, a pair of pentodes to the control grids of which said signals are applied in phase opposition, said grids being negatively biased, another pair of pentodes, means to apply one phase of a modulating signal to the screen grids of said first named pair of pentodes and the opposite phase of said modulating signal to the screen grids of said second named pair of pentodes, and means to connect the outputs of the respective pairs of said pentodes to opposite plates of said pairs of deflecting plates.

2. Apparatus for modulating a first electrical signal by a second signal comprising a first pair of thermionic tubes having screen grids and negatively biased control grids, said first signal being applied to said control grids respectively in phase opposition, a second pair of thermionic tubes having screen grids and control grids, the output of said second pair of tubes being connected respectively to the output of said first pair of tubes, said second signal being applied to said v screen grids of said first pair. of tubes and in opposite phase to'said screen grids of said second pair of tubes.

3. Apparatus for modulating afirst electrical signal by a second signal comprising a. pair'of by compensatin for the rise in voltage at the plates of tubes 2 and 3, due to modulation.

Reference character T indicates a cathode-ray tube which is provided with a cathode I I, control grid I2, first anode l3, second anode I4, a pair I5, I 5' of vertical deflection plates and a pair I6, I6 of horizontal deflection plates.

The output appearing at the terminals 9 and I0 may be resistance coupled or it may be direct coupled to the vertical deflection of the cathode-ray tube T. l

thermionic tubes having anodes, screen grids and negatively biased control grids, said first signal being applied respectively in phase opposition to said control grids, a second pair of thermionic tubes having anodes, screen grids and control grids and means for applying said second signal to'the screen grids of said first pair of tubes and in opposite phase to the screen grids of said second pair of tubes, the anodes 01 said first pair 01' tubes being connected respectively directly to the anodes or said second pair of tubes.

MEYER MARON.

REFERENCES CITED The following references are 01' record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,011,499 Paddle Aug. 13. 1935 2,239,776 Brunn Apr. 29, 1941 2,278,641 Bond Apr. 7,1942

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