US2927996A - Electronic sequential antenna switch or the like - Google Patents

Description

March 8, 1960 R. A. DAVIS v 2,927,996

ELECTRONIC SEQUENTIAL ANTENNA SWITCH OR THE LIKE Filed June 23, 1955 B giND OR SLIGHTLY R038 A. DAVIS INVENTO By flffig HIS ATTORNEY antennas to a single channel receiver.

ELECTRONIC SEQUENTIAL ANTENNA SWITCH on THE LIKE Ross A. Davis, Los Augeles, Calif.

Application June 23, 1955, Serial No. 517,461

2 Claims. (Cl. 250-40) This invention is related to electronic apparatus for automatically and sequentially coupling a plurality of antennas to the input stages of a single channel receiver.

In the past there have been several attempts made to develop a means, electronic or mechanical, which would automatically and sequentially couple a pair of more of One such system is described in the co-pending application entitled Antenna Selector filed and pending in the name of the same inventor as this application. One of the problems encountered with such priorart switching devices has been that of assuring positive de-coupling from one antenna when the other antenna is being utilized as a source of the signal to be translated. It is also necessary that the apparatus generate a minimum of noise and spurious signals and the mechanical schemes which have been used generally do not provide a sufiiciently low noise level or the desired degree of de-coupling.

Therefore, it is an object of this invention to provide an electronic sequential antenna switch which assures positive tie-coupling from one antenna when a signal is being derived from the other of theantennas."

It is a further object of this invention to provide an antenna selector circuit which develops an absolute minimum of noise.

According to the present invention certain sheet beam tubes with grid control are incorporated in the antenna switching circuitry. The ability of such tubes to switch the beam of electrons positively from one collector electrode to another collector electrode is utilized to effect the desired positive switching and high degree of decoupling I of the inactive antenna from the translating circuits.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and mannerofoperation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, in which:

Figure 1 is a schematic diagram showing one embodiment of this invention.

Figure 2 is a schematic diagram showing a second embodiment of this invention.

In Figure lradio frequency'signals from antenna 10, which may be a closed loop formed by the conductive boundary surrounding an opening in a metallic structure or vehicle, are coupled through cable 11 and input tuning circuit 12 to control grid 13 of switching tube 14 which may be of the type known as the 6AR8. Correspondingly, radio frequency signals from antenna 15 are taken through cable '16 and input tuning circuit 17 to grid '18 of switching tube '19 which may also be of the type known commercially as the 6AR8. Switch tube 14 has collector electrodes 20 and 21 between which the beam of electrons from cathode 22 may be switched by deflection plates 23 and 24 when appropriate deflection potentials are applied thereto from oscillator 31. While oscillator .31 may have any frequency dictated by the application Z,27,9% Fatented Mar. 8, 1960 involved, in the simplest case, it is a sine wave oscillator operating above the range of audible frequencies so as to produce a minimum amount of undesirable audio noise in the output from the receiver. Deflection plates 23 and 24 will be out of phase in potential, the electron beam being attracted to the one which is more positive with the result that such electron beam is deflected and falls upon collector electrode 20 or 21, whichever is closest to the deflection electrode carrying the positive potential. correspondingly, the electron beam flowing from cathode 25 of switch tube 19 will fall upon either collector electrode 26 or collector electrode 27 depending upon whether deflection electrode 28 or deflection electrode 29, respectively, is the more positive. Of course, the translated signal from antenna 10 will appear at the collector electrode 20 or 21 upon which the electron beam from cathode 22 is falling. correspondingly, in switch tube 19 the translated signal from antenna 15 will appear at collector electrode 25 or collector electrode 27 depending upon which the electron beam from cathode 25 is falling. It is to be noted that collector electrode 21 in switch tube 14 and collector electrode 27 in switch tube 19 are bypassed to ground and, hence, signal currents are short circuited when the electron beams fall on those collector electrodes. Conversely, amplified signals from antenna 10 appear at collector electrode 20 and amplified signals from antenna 15 appear at collector electrode 26. It should be noted that the connections from oscillator 31 to the deflection electrodes in switch tubes 19 and 14 are such that when the electron beam in switch tube 14 falls on the bypassed collector electrode the electron beam in switch tube '19 is falling on a signal amplifying collector electrode, and vice versa. Collector electrodes 20 and 26 are connected to a common RF load circuit but, by

currents appearing in the output circuits are a minimum.

.In Figure 2 radio frequency signals from antenna 40 are coupled through cable 41 to input tuning circuit 42 and are applied to control grid 43 in vacuum tube 44. correspondingly, signals from antenna 45 are coupled "through cable 46 to input tuning circuit 47 and are applied to control grid 48 of vacuum tube 44. The electron beam from cathode 49 passes through control grid 43, focusing electrode 50, accelerating electrode 51 and deflection electrodes 52 and 53 before approaching collector electrodes 54 and 55. Out-of-phase deflection voltages are applied to deflection plates 52 and 53 from oscillator 56 which may be a sine wave or square wave oscillator. When deflection electrode 52 is positive with "respect to deflection electrode 53, the electron beam is bent towards collector electrode 54 which is bypassed to ground and short circuits the signal from antenna 40. However, when deflection electrode 53 is positive with respect to deflection electrode 52, the electron beam falls upon collector electrode 55 to which is attached output tuning circuit 57.

The electron beam from cathode 58 passes through control electrode 48, focusing electrode 59, which is common with focusing electrode 5%, accelerating electrode 60, which is common with accelerating electrode 51, and deflection electrodes 61 and 62 before approaching collector electrodes 55 and 63. When deflection electrode 62 is positive with respect to deflection electrode 61, the electron beam from cathode 58 falls upon col- 3 lector electrode 63 which is bypassed to ground and short circuits the signals from antenna 45. Conversely, when deflection electrode 61 is positive with respect to deflectlon electrode 62, the electron beam from cathode 58 falls upon collector electrode 55 and an amplified signal appears in the output tuned circuit 57. For certain applications it would be feasible to combine cathodes 49 and 58 into a single elongated cathode having two electron emitting areas, one controlled by grid 43 and the other controlled by grid 48. Such a common cathode should be heavily bypassed. It is to be noted that deflection electrode 61 is connected to the same oscillator terminal as deflection electrode 52 and deflection electrode 62 is connected to the same oscillator terminal as deflection electrode 53. As a result, when the electron beam from cathode 49 is falling upon the bypassed collector electrode 54 and, hence, the signal from antenna 40 is short circuited, the electron beam from cathode 58 is falling upon collector electrode 55 and is being resonated in tuned circuit 57 thus providing signals from antenna 45 to the succeeding stages of the receiver. As the phase of the output voltage from oscillator 56 reverses, the converse condition occurs and signals from antenna 40 appear in output tuned circuit 57 and are coupled to the succeeding stages of the single channel receiver. Output tuned circuit 57 of Figure 2 as well as output tuned circuit 30 of Figure 1 are tuned to frequencies sufficiently higher than that of oscillators 31 and 56, respectively, to appear as substantially short circuits at the switching frequency. Further, each of these tuned circuits is coupled to the succeeding input stage in an unusual fashion. For example, in Figure 2, variable condenser 65 is serially connected from slug-tuned inductor 65 to the low potential end of slug-tuned input inductance 67 of the next stage. Common bypass condenser 68 assures that this is a low-impedance, high-efiiciency intercoupling. It is to be understood that well known magnetic techniques, either beam bending or beam rotating, may be applied to replace the electrostatic deflection techniques utilized in this tube. The circuit which has just been described also provides a high degree of isolation between either of the antennas and the output circuit when the signal from the remaining antenna is being translated. It is to be noted that although the circuits thus far have described the switching on only two antennas by developing three or more phases in the voltages from oscillator 56 and applying such multi-phased voltages to appropriate electrostatic or electromagnetic deflection elements in a tube or tubes having the requisite number of amplifying electrodes cooperating with such deflection elements it would be possible to switch any number of antennas sequentially into the single channel receiver which follows the switching circuit. While reference has been made frequently to the coupling of multiple antennas to a receiver,

it is apparent that the same circuitry may be utilized to provide sequential coupling between any number of R-F sources and loads, for example in coupling multiple transmitting antennas to a single transmitter.

Therefore, it may be seen that there has been provided a sequential switching circuit which is free from the noise normally experienced with mechanical switching circuits and which provides a high degree of de-coupling of the undesired signal or the R-F circuit which is intended to be inactive.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. A sequential antenna-selector including: a sheet beam signal amplifying vacuum tube having, in the order named along the paths of electron flow, a pair of electronemitting cathode areas; a control grid supported in operative relationship with respect to each cathode area; a pair of deflection plates positioned to deflect the electron beam emitted by each cathode area; and a common collector electrode positioned between the paths of undefiected electron flow from said cathode areas; an output circuit coupled to said common collector electrode; a source of deflection potential alternating in sign; means for coupling such deflection potential to each pair of deflection plates in such phase as to alternately deflect the beam of electrons from each cathode area onto said collector electrode; and means adapted for coupling an antenna to each of said control grids.

2. A selector circuit for sequential selection of antennas, including a sheet beam signal amplifying vacuurn tube having a pair of electron-emitting cathode areas, a control grid supported in operative relationship with respect to each cathode area, a pair of deflection plates positioned to deflect the electron beam emitted by each cathode area, an accelerating electrode associated with each cathode area on the side of said deflection plates remote from said cathode areas, and a common collector electrode positioned between said accelerating electrodes; an output circuit coupled to said collector electrode; a source of varying deflection potential; means for coupling such deflection potential to each pair of deflection plates with such polarity as to alternately deflect the beams of electrons from each cathode area to said common collector electrode; and means adapted for coupling an antenna to each of said control grids.

References Cited in the file of this patent UNITED STATES PATENTS 2,165,308 Skellett July 11, 1939 2,185,693 Mertz Jan. 2, 1940 2,225,330 Cage Dec. 17, 1940 2,233,126 Haeff Feb. 25, 1941 2,439,651 Dome Apr. 13, 1948 2,459,724 Selgin Jan. 18, 1949 2,533,405 Skellett Dec. 12, 1950 2,594,517 Sziklai Apr. 29, 1952 2,617,963 Arditi Nov. 11, 1952 FOREIGN PATENTS 485,626 Great Britain May 20, 1938

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