US1755091A - High-frequency receiving system - Google Patents

Description

A ril 15,1930. H.E .A1LLEN 1,155,091

HIGH FREQUENCYREGEIVING SYSTEM Filed Maroh -'29, 1929 Inventor I Hu miAuen,

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Patented Apr. 15, 1930 UNITED STATES PATENT oFFicE' HUGH E. ALLEN, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELEGTRIC COMPANY, A CORPORATION OF NEW YORK HIGH-FREQUENCY RECEIVING SYSTEM Application filed March 29, 1929. Serial No. 351,093.

My invention relates to high frequency receiving systems for use in connection with remote control systems such, for example, as that disclosed in my application, Serial No.

195,388, filed May 31, 1927, and entitled Ra mote control system of which my present application is a continuation in part.

It has for one of its objects to provide a receiving system employing an electron discharge device the electrodes of which may be energized from an alternating current source, which is more economical to construct than known circuits utilizing alternating energizing currents and which possesses the characteristic of sensitiveness to received high frequency impulses.

The novel features which I believe to be characteristic of myinvention are set forth with particularity in the appended claims.

My invention itself, however, both as to its organization and method of operation, to gether with further objects and advantages thereof, may best be understod by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 represents an embodiment of my invention, and Fig. 2 represents a modification thereof.

Referring to the drawing I have represent- P ed at 1 an electron discharge device having an anode, a cathode and a grid. This discharge device is arranged to be energized by alter nating currents, which may be of commercial frequency as, for example, sixty cycles per second, and which are supplied thereto by means of a transformer 5 having a plurality of secondary windings 6, 7 and 8. Potential is supplied to the grid of the discharge device by means of the winding 6 and tothe anode thereof by means of the winding 8, whereas the cathode is energized from the winding 7 The adjacent terminals of the windings 6 and 8 are connected to the cathode, and the potentials on opposite terminals of these windings, which are displaced in phase by 180, are supplied to the grid and anode. The outer terminal of the winding 8 is connected to the anode through relay 9 and the outer terminal of winding 6 is connected to the grid through a resistor 10 and secondary winding of an input transformer 11.

The primary winding of tranformer 11 may, of course, be connected through a suitable coupling means to a power transmission line over which high frequency carrier currents are transmitted, or to an antenna, or other means whereby high frequency currents, for control of remote equipment, etc., are supplied to the discharge device.

In the operation of the device, as thus described, it will be apparent that the winding 6 supplies a bias potential to the grid of device 1 during the half cycle when the anode is positive. Thus during this half cycle the device operates as a biased detector. The anode current, during this half cycle, assuming that no high frequency electromotive force is supplied to the grid, is maintained at a suitably small value, or a zero, by means of the grid potential. hen high frequency electromotive force is impressed upon the grid, the negative grid potential will be sufficiently opposed by the positive half cycles of the high frequency wave to permit sufficient anode current to fiow in the device to cause operation of relay 9. p

The condenser 12, which is connected in arallel with the winding of relay 9, becomes charged by the anode current when the anode is positive and discharges its current through the winding of relay 9 when the anode is negative. the relay is maintained during the negative half cycle and the relay is thereby prevented from chattering.

The input circuit to the discharge device may, of course, be tuned to the frequency of the high frequency electromotive force, in any suitable manner, as by connecting a condenser across the secondary winding of transformer 11 or, if desired, the transformer may be one having suflicient distributed capacity to render it inherently resonant at the frequency at which the system is to operate.

To obtain maximum efficiency of the device, it is necessary that the 180 phase relation which exists between the potentials at the outer terminals of windings 6 and 8 be preserved upon the grid and anode of the dis- In this way the energization of charge device during periods when no high frequency electromotive force is impressed upon the grid and that, as will be explained hereinafter, the grid should become negative substantially simultaneously with the anode becoming positive. If any appreciable current be permitted to flow in the grid circuit, this current flowing in the impedance of thatcircuit will cause a deviation from the above relation between the potentials impressed upon the grid and anode of the device and a consequent diminution in efficiency and sensitiveness of the device.

Theanode current, of course, except as indicated hereinafter, may be maintained at zero, or at a suitably small value, by means of the bias potential on the grid. During the half cycle, when the grid is positive, however, current will flow in the grid circuit. This current will cause energy to be stored in the inductance of the transformer 11 which energy will, in turn, tend to cause the grid to remain positive after the anode has become positive. Consequently a short rush of current in the anode circuit will occur at the beginning of each operative half cycle of the device independently of received high frequency electromotive force. This current will cause the condenser 12 to be charged during the first position of the half cycle when the anode is positive. This condenser, in turn, will discharge through the winding of relay 9 after the short impulse has passed. Thus the result of this flow of current is to necessitate an adjustment of the relay 9 such that it will not respond to this current, which adjustment, in turn, causes a less sensitive operation of the relay to current flowing in the anode circuit in response to high frequency electro-motive force upon the grid.

To obviate this adjustment and to preserve the 180 phase relation between the grid and anode potentials the resistance 10 is inserted in the grid circuit of such value that substantially no grid current flows during the half cycle when the grid is positive. The anode current may then be maintained at Zero value or at a Very small value by means of the grid bias potential with the result that maximum efficiency of the device is obtained.

Fig. 2 represents a modification of the system shown in Fig. 1 in that a transformer 13 is employed for supplying energy of the frequency of the energizing currents from the anode circuit of the device 1 to the grid circuit thereof during the half cycle when the anode is positive. That is, when high frequency current is applied to the grid of the discharge device the current flowing in the anode circuit thereof will cause a potential impulse to be produced in the secondary winding of the transformer 13 having the frequency of the power source. The secondary winding of this transformer is connected in the rid circuit of the discharge device in opposed relation to the winding 6 thereby tending to cause the grid of the discharge device to become positive during the half cycle when. the anode is positive.

It will thus be seen that when no high frequency current is received the bias on the grid of the discnarge device 1 during the l alf cycle when the anode is positive will be determined practically entirely by the potential of the winding 6. Then carrier is received, however, and current is caused to flow in the anode circuit during the half cycle when the anode is positive the negative bias potential upon the grid will be reduced by'the amount of the instantaneous secondary voltage of the transformer 13. This potential may be sui'iicient to drive the grid positive. In this way the current flowing in the anode circuit and hence the sensitivity of the device may be greatly increased.

The resistance 10 will of course serve to so reduce the grid current that the relation indicated above between the potentials on the grid and anode is obtained during the period when no carrier is received.

The sensitivity of the device may be fur ther increased by tuning the feedback circuit to resonance at the frequency of the power source. This may be effected by connecting a condenser 14 of proper capacitance across the primary winding of the transformer 13.

lVhile I have illustrated my invention in connection with a receiving system having a particular type of input and output circuit, it will of course be apparent that I do not wish to be limited thereto since my invention has utility in connection with systems employing other forms of input coupling means and load circuits as well.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a receiver for high frequency electric impulses employing an electron discharge device having an anode, a cathode and a grid, a source of alternating current, connections from a neutral point on said source to said cathode and from opposite points on said source to said grid and to said anode such that voltages on said grid and on said anode are in opposed phase relation, means for impressing high frequency impulses on said grid, means in said grid connection for correcting for displacement in phase relation between said grid and anode voltages resulting from said last means and current responsive means associated with said anode.

2. In a receiver for high frequency electric impulses employing an electron discharge .device having an anode, a cathode and a grid,

a source of alternating current, connections from a neutral point on said source to said cathode and from opposite points on said source to said grid and to said anode such that voltages on said grid and on said anode are in opposed phase relation, means for impressing high frequency signaling impulses on said grid, means in said grid connection for reducing the current flowing therein substantially to zero during the half cycle when the grid is positive with respect to the cathode, and current responsive means associated with said anode.

3. The combination, in a high frequency receiver of an electron discharge device having an anode, a cathode and a grid, a source of alternating current, connections from a neutral point on said source to said cathode and from opposite points on said source to said gridand anode, input means having energy storage capacity connected between said grid and cathode, and means for preventing storage or energy in said means during the half cycle when the anode is negative thereby to prevent the fiow of anode current due to potential on the grid resulting from energy stored insaid means.

4. The combination, in a high frequency receiver, of an electron discharge device having an anode, a cathode, and a grid, a source of alternating electromotive force, connections from a neutral point on said source to said cathode and from opposite points on said source to said grid and anode, a relay connected in series between said anode and cathode, an input transformer having a secondary winding connected between said grid and cathode and a resistance connected in series with said winding to prevent flow of current in said relay resulting from energy stored in said means when no high frequency electromotive force is supplied to the grid.

In witness whereof, I have hereunto set my hand this 28th day of March, 1929.

HUGH E. ALLEN.

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