US2810859A

US2810859A - Cathode ray filter

Info

Publication number: US2810859A
Application number: US511627A
Authority: US
Inventors: Karl F Ross
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-05-27
Filing date: 1955-05-27
Publication date: 1957-10-22
Anticipated expiration: 1974-10-22

Description

ocrn 22, 1957 A K. F. Ross 1 2,810,859

zATHoDE RAY FILTER Filed May 2,7. 1955 United States Patent My present invention relates. to a cathode ray iilter for electromagnetic waves. This application is a continuation-in-part of my co-pending application Ser. No. 155,205, led April 1,1, 1950, now Patent No. 2,728,854, issued December 27, 1955.

An object of my present invention is to provide means in a cathode rayV tube for `discriminating between waves of different frequencies and selectively producing an output representative of one or more ofsuch waves.

Another objectof this invention is to provide a lter adapted to accept certain wavelengths within a given band while rejecting other wavelengths, in combination with means f-orinterchanging the pass and stop bands r.of such iilter.

A further object of the invention is to provide sharply discriminating `filter `means for channeling single-frequency waves of different amplitudes into respective signaling circuits. p

In a system as herein disclosed there are provided rst and second dellecting means for deflecting the beam of ,a cathode ray tube in different (usually perpendicular) planes, in combination with a network for varying the relative phase of signal waves applied to these two deflecting means in dependence upon their frequency. (A similar system utilizing a network forvarying the relative amplitude, rather than phase, of such signal wavesl has been disclosed and claimed in co-pending application Ser. No. 155,207, led April 11, 1950 by Phil Cutler and myself, now Patent No. 2,728,911, issued December 27, 1955.)

A feature of the instant invention resides in providing,

in a cathode ray tube system as set forth above, a plurality of concentric annular output electrodes each shaped and positionedto register with the trace of the beam when the latter is deflected by a signal of predetermined frequency and amplitude; if these output electrodes are all similar to each other (e. g. all'circular), they will 50 all respond to signals of the same frequency but of different amplitudes.

Another feature of my invention resides in the provision of an output electrode having at least one but not more than two axes of symmetry, each axis of symmetry being inclined with respect to the two planes of deection of the beam. .An electrode of this description has a preferred dimension which, if positioned at a 45 angle relative to the planes of deflection, will coincide with the axis of an ellipse which will be the major axis for some frequencies and the minor axis for others. A relatively large output will then be obtainable from waves in the first-mentioned frequency group while only a negligible output will result from waves of said other ,frequencies. When the connections between the signal source and the two deecting means are reversed, the positions of the two frequency groups in the spectrum are interchanged.

Advantageously, therefore, a cathode ray tube accordi ing to the invention comprises target means in the shape of a plurality of distinctly elliptical, concentric and similar ellipses whose major and minor axes extend at 45 angles with respect to two perpendicular planes, in combination with means for subjecting the beam of the tube to out-of-phase deiiectingforces in said two planes derived from the samerinput signal. Y

, My invention will be more fully described with reference to the accompanying drawing in which:

Fig. 1 shows acircuit arrangement of a cathode ray tube system embodying the invention; and

Figs. 2-7 illustrate` different targets adapted to be used as output electrodes with the system of Fig. 1.

Throughout the drawing, similar elements have been denoted by the same reference numerals prefixed by different hundreds digits identifying the respective ligures.

In Fig. 1 there is shown a cathode ray tube 100 cornprising a source of electrons shown as a cathode 101 and focusing or beam-forming means shown as a first anode 102 and a second or accelerating anode 103. The

electrodes

101, 102 andiV 103 derive their potentials from a battery 104 and a potentiometer 105 in series therewith,

Two pairs of deiiecting electrodes 106', 106" and I107',

107", arranged in mutually perpendicular planes, receive signals from input terminals 108', 108" to which the horizontal deflectors 106', 106" are connected directly; the vertical deiiectors 107', 107" are connected across the signal source 108', 108" through a reversing switch 109 and a delay network 110. This network, shown schematically as composed of a pair of ladder-type filter sections, may be a four-terminal network with lumped constants, a coaxial line, or any other combination of circuit elements adapted to impart a progressive phase shift to a range oflsignalswithin a predetermined frequency range withoutmaterially varying their relative amplitudes.

The beam 111, produced by the electron gun 101-103, impinges upon an output electrode generally indicated at 112 and consisting of a dielectric backing 113, a layer 114 of resistance material thereon and a pair of highly conductive terminal members 11S', 115" in contact with that layer at diametrically opposite locations. Electrode 112 may be similar to the target 312 shown in face view in Fig. 3, having its terminal members 11S', 115 inclined at 45 with respect to the horizontal and vertical planes of deflection; these terminal members are co'nnected across an output resistor 116, grounded at its center, and to respective output terminals 117', 117.`

The operation of the system of Fig. 1 is asfollowss With switch 109 in its right-hand position of, closure, ground on signal terminal 108 is applied to horizontal deflecting electrode 106 and to vertical deflecting electrode 107'. It will be convenient to consider these two electrodes as located on the negative half-axes of a coordinate system. A positive signal voltage applied to terminal 108" will then appear instantaneously on electrode 106", thus tending to deflect the beam in the positive horizontal direction; after a delay 0, dependent upon the signal frequency, it will also appear on electrode 107" so as to tend to deiiect the beam in the "positive vertical direction. 1f the position of switch 109 is now reversed, the phase of the signal on electrode 107" is shifted by 180 and the lagging phase angle 0 isV converted into a leading phase angle of like magnitude. Itwill thus be seen that a phase reversal on one set of deflecting electrodes is equivalent to a transfer of delay network from one set of electrodes to the other.

If, for a given signaling frequency, the phase angle 0 is equal to 0, 360 or any multiple thereof, the deflected beam will produce a linear trace bisecting the positive and negative lquadrants of the c-oordinate system. In Fig. 2 l have shown a target electrode 212 aligned with such trace, comprising an elongated body 214 of resistance material inclined at 45-to the horizontal and vertical planes of deection. Terminal members 215', 215" at the ends of body 214 are connected across series resistors 216', 216" which are grounded at their junction, each resistor being bridged by a respective condenser 219', 219" serving as a shunt for impulses due to brief crossings of target 212 by the beam when the latter is deflected by signal waves not having the proper frequency. The output terminals of the system are shown at 217', 217".

The target electrode 312 of Fig. 3 comprises a rectangular resistive body 314 bounded on two opposite edges by terminal strips 315', 315", the latter being connected across output terminals 317', 317" which are bridged by resistor 316 grounded at its midpoint. Owing to the arrangement of strips 315', 315", the face of electrode 312 (as also of electrode 212) has but two axes of symmetry even if its resistance body 314y is a perfect square; these axes are again inclined at angles to the horizontal and vertical planes of deflection.

If f, is a signal frequency for which the phase delay introduced by network 110 is 180 or an odd multiple thereof, and if f2 is a frequency for which this phase delay is zero or any even multiple of 180 as considered in connection with Fig. 2, the trace of the beam will be a straight line perpendicular (f1) or parallel (f2) to the Strip`s 315', 315". In the lirst instance the output at terminals 317', 317" will be a maximum; in the second instance this output will vanish. When the switch 109 is reversed, the positions of traces f1 and f2 will be interchanged whereby only the latter frequency will produce an output. It will thus be seen that the device now being described acts as a filter having,r `a pass band centered on a first frequency f1 and a stop band centered on a second frequency f2, the switch 109 serving as a means for interchanging the positions of these bands in the frequency spectrum.

A frequency f3, for which the phase delay is 90 or an odd multiple thereof, will give rise to -a circular trace as likewise shown in Fig. 3; this trace will be unaffected by reversals of switch 109, producing output oscillations of equal amplitudes in the two switch positions. Intermediate frequencies will produce elliptical traces having their major axes perpendicular (L) or parallel (f5) to terminal strips 315', 315". These frequencies will, accordingly, result in a relatively large and a relatively small output respectively, subject to reversal by operation of switch 109. It will be noted that the relative amplitudes of the output oscillations in Fig. 3 are determined by the extent of the beam sweep in a preferred dimension (perpendicular to strips 315', 315") and are substantially independent of the location of the beam trace on the face of electrode 312.

In Fig. 4 I have shown a type of target adapted to discriminate between a single, pure sine wave of predetermined frequency on the one hand and other types of waves, including or not including the desired frequency, on the other. Such devices are particularly useful in voice frequency signaling systems of telephone circuits wherein it is necessary to guard against false operation of a relay or other switching mechanism by speech waves that happen to contain the critical frequency.

The target of Fig. 4 comprises three concentric ring electrodes of highly conductive material, indicated at 412er, 412b and 412C respectively. Each of these electrodes is connected to a respective output resistor 416a, 41611, 416C and a respective output terminal 417a", 417b", 417e", the later in turn being connected to grounded terminal 417 by way of respective condensers 41911, 41%, and 419C.

If an incoming signal consists of a pure sine wave of frequency f3, the beam 111 will trace a circular path which, depending upon they amplitude of the wave, may be made to coincide with one of the

electrodes

416a, 416b, 416e, thus giving rise to a D.-C. output signal at the corresponding set of terminals. If the frequency of the wave has a value other than f, as defined above, the

4 beam will only intermittently intersect the electrodes of Fig. 4, thereby producing a series of short pulses which will be ineffective to result in any switching operation, being largely shunted to ground through the respective condensers 41911, 419b, 419C (the same as in the system of Fig. 2). A similar situation will exist if some other signal is superimposed upon the wave of frequency f3, Since then the trace wi ll be displaced from its concentric position with respect to the

electrodes

412a, 412b, 412e.

Fig. 5 shows a single electrode 512 consisting of a conductive strip inclined at 45 `and connected to an output resistor 516, the output terminals 517', 517" being bridged by a condenser 519. From the foregoing it will be understood that this electrode responds only to a signal wave of frequency f2 and substantially rejects all other waves, but that in contradistinction to the target 212 of Fig. 2 it produces a steady output potential rather than an oscillating voltage in response to such signal. The output appearing across terminals will, furthermore, be independent of the amplitude of the incoming signal wave.

Fig. 6 illustrates a target combining the features of the systems of Figs. 2 `and 4, designed to produce any oscillatory output which is channeled into one of several load circuits according to the amplitude of the incoming wave. This figure shows three

concentric electrodes

612a, 612b, 612C comprising respective annular layers 614:1, 614b, 614e of resistance material and pairs of diametrically opposite terminal elements 615g', 615a"; 61512', 615b"; 615e', 615C". Each of these terminal elements is grounded by way of a respective output resistor 616:1', 616b', 616C' and 616a", 616b", 616e", shunted by a respective condenser 619a', 619b', 619C' and 619a", 61919", 619C". The corresponding output terminals are indicated at 617a', 61711', 617e' and 617a", 617/1", 617C".

In Fig. 7 I have shown a target consisting of three concentric annular electrodes 712g, 7125, 712C, which are similar to the electrodes of Fig. 6 but are in the form of elongated ellipses rather than circles. Again, each electrode consists of resistance material and is provided with diametrically opposite terminal elements 715g', 715a", 715b', 715b"; 715e', 715e". It will be noted that all of these ellipses are similar, i. e. that the ratio of their axes is the same (corresponding to a predetermined signal frequency, such as f5), and that the major axes are inclined at 45 to the planes of deflection. The output connection of the target electrodes have not been shown in Fig. 7 and may be the same las in Fig. 6. The positioning of the terminal members at the apices of the ellipses is convenient but not essential.

The reversing switch 109, which would be functionless in the case of circular target electrodes as shown in Figs. 4 and 6, may be used in conjunction with the system of Fig. 7 for varying the frequency to which the system iS designed to respond, as by changing it fromf5 to L. It will be understood that a steady rather than an oscillating output may be derived from the electrodes 712a, 71217, 712r.` by constructing them of highly conductive material and connecting them across respective load resistors in the manner illustrated in Fig. 4.

From the foregoing description it will be apparent that the beam of the cathode ray tube will describe a generally elliptical path in response to any particular frequency component within the frequency band considered, the straight lines f1, f2 and the circular trace y', being extreme and specific instances of such elliptical path. Useful output will, of course, also be obtainable if only part of the beam trace registers with the target, as where a portion of one or more of the annular electrodes in Figs. 4, 6 and 7 is omitted. The invention is, accordingly, not limited to the specific embodiments described and illustrated but is capable of different modes of realization without departing from the spirit and scope of the appended claims.

I claim:

l. A wave filter comprising a source of electrons, focusing means forming said electrons into a beam, a

source of 'signal waves, first and second deecting means positioned along the path of Isaid beam, first circuit means connecting said source of signal waves to said iirst defleeting means for deecting said beam in one plane under the control of said waves, second circuit means connecting said source of signal Waves to said second deliecting means for deflecting said beam in another plane under the control `of said waves but with a phase delay relative to its deection in said one plane, and target means in the path of said beam comprising at least one output electrode having at least one but not more than two axes of symmetry each inclined with respect to said planes.

2. A wave iilter according to claim 1, further comprising switch means for reversing the relative phase of said signal waves as applied to said first and second deflecting means.

3. A wave filter -according to claim l, wherein said output electrode is in the form of an elongated ellipse.

4. A wave lter according to claim 3, wherein said output electrode comprises a body of resistance material provided with output connections at diametrically opposite points.

5. A wave lter -according to claim 1, wherein said output electrode comprises an elongated strip bisecting the angle between said planes.

6. A wave lter according to claim l, wherein said output electrode comprises a substantially rectangular element of resistance material provided with highly conductive terminal strips along opposite edges, said terminal strips extending substantially parallel to the bisector of the angle between said planes.

7. In a cathode ray tube, in combination, means for producing an electron beam, a source of signal waves, means connected to said source for deiiecting said beam along generally elliptical traces in response to signal waves of a predetermined frequency, a plurality of similar, concentric annular output electrodes shaped and positioned to coincide with said traces for different amplitudes of said waves of predetermined frequency, and a load circuit connected to each of said output electrodes.

8. The combination according to claim 7, wherein said output electrodes are in the shape of elongated ellipses.

9. The combination according t'o claim 7, wherein said output electrodes comprise annular bodies of resistance material provided with output connections at diametrically opposite points.

10. In a cathode ray tube a target electrode having the shape of at least a substantial part of an elongated ellipse.

11. In a cathode ray tube a target electrode comprising an elongated elliptical body of resistance material and output connections at diametrically opposite points of said body.

12. In a cathode ray tube, in combination, means for producing an electron beam, a source of signal waves, rst means connected to said source for deecting said beam in one plane in the rhythm of said Waves, second means connected to said source for deiiecting said beam in another plane in the rhythm of said waves but out of phase with the deflection of said beam in said one plane, and an elliptical target electrode in the path of 'said beam, said electrode having a major axis inclined with respect to said planes.

13. The combination `according to claim 12, wherein said planes are perpendicular to each other, said major axis extending at with respect to said planes.

14. The combination Iaccording to claim 12, further including switch means for reversing the relative phase of deection of said beam in said planes.

References Cited in the le of this patent UNITED STATES PATENTS