US2414475A - Phase shifting means - Google Patents

Description

Jan. 21, 1947. N. MARCHAND PHASE SHIFTING- MEANS Filed April 25. 1942 (iv/a VOLTAGE INVENTOR Mar/141v Make/M ATTORNEY Patented Jan. 21, 1947 PHASE SHIFTIN G MEANS Nathan Marchand, New York, N. Y., assig'nor to Federal Telephone and Radio Corporation, a

corporation of Delaware 4 Application April 23, 1942, Serial No..440,179

Claims. 1

This invention relates to improvements in phase-shifting devices and in particularto such devices as are operative to produce substantially constant voltage output.

It is a prime objective of the invention to provide improved means for producing from a substantially constant voltage an adjustably variable phase shift at a second substantially constant voltage.

Other objects and various further features of novelty and invention will hereinafter be pointed out or will become apparent to those skilled in the art from a reading of the following specification in connection with the drawing included herewith. In said drawing Fig. 1 is a schematic diagram of a basic phaseshifting circuit; t

Fig. 2 is a vector representation of voltages appearing in the circuit of Fig. 1; and

Fig. 3 represents an improved circuit illustrating a method of eifecting a phase shift electronically in accordance with the invention.

Phase shifting devices have been suggested wherein manual operation of certain circuit elements is required to effect the desired phase shift. some of these devices have been of the nature shown in Fig. 1 wherein input voltage is applied across a voltage-dividing device having a centertap. In the form shown, this divider is a resistive potentiometer and comprises two equal impedances R1 and R2. Across the potentiometer are connected two further impedances, one of which has a characteristic in phase quadrature with that of the other. In the form shown, one of these further impedances R3 is resistive and the other C1 is capacitatively reactive. If the applied voltage at the input is substantially constant, a substantially constant voltage may be taken from between the center-tap of the potentiometer and a point between impedances R3 and C1. By adjusting the relative magnitudes of R3 and C1, the phase but not the voltage magnitude of the output may be correspondingly adjusted.

This effect may be more clearly illustrated by the vector diagram of Fig. 2 wherein it will be seen that input voltage is uniformly divided between impedances R1 and R2, as illustrated by the equal vectors Va and V3,. Since output is taken from the center-tap of the potentiometer, the juncture of vectors Va and Va defines one end of the output voltage vector V output. Since the characteristics of impedances R3 and C1 are always in quadrature with respect to each other and further since the voltage across them always equals the sum of Va, and VR the vector locus of the .voltage at a point between them lies on a semi-circle having a radius equal to Va or V12 Since the output is taken from between the center-tap and a point between impedances R3 and C1, the vector representing this voltage will always be equal to the radius of the semi-circle and hence constant.

In accordance with the invention, the relative magnitudes of the quadrature impedances may be electronically controlled by the use of a Vacuum tube having a resistive impedance characteristic which may be varied by varying the grid bias. Such a circuit is shown in Fig. 3 wherein the potentiometer comprising impedances R1 and R; will be recognized. For the sake of simplicity, the circuit of Fig. 3 has been shown to include means for varying only one of the quadrature impedances, namely, the resistive one. In the form shown, this means comprises a variable ,a triode T having a variable resistance R4 in its grid circuit. A large blocking condenser C2 connects one end of resistor R4 to the input side of impedance R1 and to the anode circuit of tube T. Another blocking condenser C3 connects the other side of resistor R4 to the cathode circuit of tube T. Condenser C1 representing the reactive portion of the impedances across the potentiometer is connected to the cathode circuit of tube T.

Considering the input of the circuit of tube T as between anode and cathode, the resistance Za of this tube will appear as where Ep is the signal voltage applied to the anode of tube T from input I, Rp is the plate resistance of tube T, and es is the magnitude of signal voltage from input I which is applied to the grid as controlled by the setting of potentiometer R4.

With the circuit thus described, it will be clear that the resistive impedance branch represented by tube T may be adjustably controlled by hand in accordance with the setting of potentiometer R4. To get an idea of the magnitude of phase control obtainable in this manner, it is convenient to consider the condition when es is made equal to Ep, at which time ZR becomes equal to On the other hand, further variation in the efiective resistance oifered by tube T may be seen as limited by e; being so small that ZR becomes equal "an ics I s substantially only to Rp. It is thus clear that a relatively wide range of manually controlled phase shifts may be obtained with the circuit of Fig. 3.

For any particular manual setting of efi'ective resistance offered by the circuit of tube T, as

made in the above manner, electric, control.

thereof may be efiectedby applicationof a ,de'-" sired control-signal pattern at point P. In this manner grid bias is varied in accordance with the control signal and, in the assumed case of a' variable a tube," so is the p. of tube T.' Itiis.

thus clear that a relatively wide range of elec-,- tronic control of phase shifts'is possible for'anyi particular manual setting of potentiometer R4, as

above explained,

Although I have described my invention indetail in particular connection with the preferred form illustrated, it is to be understood that many modifications, additions, and omissions may be .made fullyxwithin its scope; as defined by the appended claims;

'What. is claimed is:

1. Means for'offering an apparent-variable re-' electron-emissiveelectrode to form the other terminal of said apparent variable resistance, means for applying said control signal across said; adjustable voltage-dividing means, and means for applying a biasing potential through said voltage-dividing means to said' control electrode independently of said control signal.

2.,Apparatus according to claim 1, wherein said means for applying a biasing potential is connected to apply. said biasing potential to one endof said voltage dividing means.

3. In a phase shifting circuit having a voltage dividing means across which input energy is applied, a vacuum tube having plate, cathode and grid electrodes, and a condenser connected be tween one end of said voltage divider and said cathode electrode, the plate electrode being connected to. the other end of said voltage dividing means; means ,for'controlling theimpedance of said'tube comprising a second condenser connected to said plate electrode, a bias voltage source for said grid electrode, a potentiometer therefor with connections therefrom to said second condenser, to said voltage bias source and to said grid, whereby adjustment of said potentiometer controls the impedance of said'tube.

4. In a phase shifting circuit according to claim 3 wherein said potentiometer includes a resistance and an adjustable contact, said resistance being connected between said second condenser and said voltage bias source and said adjustablecontact being connected to said grid electrode.

5; A translating system comprising a voltage dividing means having center tap and outer terminals for application of an input voltage thereto, a series connection of component impedances between. said terminals and with its components connected together at an intermediate point, one

impedance component comprising a potentiometer resistance and an electron discharge device having a control electrode, a biasing means therefor, and a plate-cathode circuit in shunt

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