US1801636A - Piezo-electric-crystal stabilizer modulator - Google Patents

Description

A. M L. NICOLSON PIEZO ELECTRIC CRYSTAL STABILIZER MODULATOR Filed Jan. 18, 1927 April 21, 1931.

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flMPL/F/ER 29 POWER 29 30 flMPL/F/[R INVENTOR ALEXANDER 1mm NICOLSON ATTORNEY Patented Apr, 21, 1931 ALEXANDER MCLEAN NICOLSON, OF NEW YORK, N. Y., ASSIGNOR,

BY MESN E ASSIGN- MENTS, TO FEDERAL TELEGRAPH COMPANY, A CORPORATION OF CALIFORNIA PIEZO-ELEOTRIC-CEi-YSTAL STABILIZER MODULATOR Application filed January 18, 1927. Serial No. 161,853.

This invention relates to apparatus for producing electrical oscillations of relatively high frequency, suitable for carrier current or radio transmission, modulated at relatively lower frequencies and, more particularly, to such apparatus, utilizing piezo-electric crys tal devices for introducing the control or stabilization of the high frequency, and also for introducing the modulating frequencies.

It is an object of this invention to provide apparatus of the class described utilizing a piezo-electric device particularly adapted for stabilizing the high frequency, and an additional piezo-electric device particularly adapted for the introduction of the low or modulating frequencies into the system.

It is a further object of this invention to provide apparatus of utilizing the minimum tube amplifiers number of vacuum and performing simultaneously the functions of oscillation generation, f

frequency stabilization, and modulation by means of a single amplifying. system, and utilizing for the high frequency control a piezo-electric crystal device particularly adapted thereto, and for the low frequency oscillations a piezo-electric crystal device particularly adapted thereto.

It is still a further object of this invention to provide such apparatus in which the various crystal devices are arranged so as not to interfere with each other in operation at widely different frequencies in the same circuit.

Still other objects of this invention will be apparent from the specification. p

The features of novelty which I believe to be characteristic of my invention, are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles and as to its practical applications, will best be understood by reference to the specification and accompanying drawing, in which:

Fig. 1 is a diagrammatic view of one form of apparatus according to my invention.

ig. 2 is a similar view of another form thereof. 1

In accordance with my invention, I provide an apparatus for producing oscillations the class described of a frequency suitable for carrier current or radio transmission, such, for example, as an oscillator, preferably a thermionic vacuum tube oscillator.

I also provide a pair of crystal devices, one of which is particularly adapted to respond to the frequency desired for transmission for the purpose of controlling and stabilizing the same, and the other of which is adapted to respond to acoustic vibrations and to convert the same into electric oscillations corresponding thereto, which may be used to modulate the high frequency oscillations. Both of these crystal devices are arrangedin circuit in such manner as to control the potential between the grid and filament of a thermionic amplifier, which pro duces in its output circuit the high frequency signalling'oscillations modulated at the low frequencies of the signal, whether these low requencies be speech, music or other audible signals.

The modulated high frequency oscillations may then be passed through a suitable power amplifier and amplified to the desired extent, after which they may be impressed upon the load circuit such for example, as an antenna or a wire line.

According to another, and in some instances preferred, form or modification of my invention, I may dispense with the separate oscillator and provide an arrangement of circuits associated with the amplifier, such that this amplifier itself acts as a generator of high frequency oscillations, the frequency of which is stabilized by one of the piezo-electrio crystal devices. The oscillations of modulating frequency or frequencies, are supplied by the other or low frequency piezo-electric device. In this instance, although only a single amplifying system is utilized, the currents flowing in the output circuit thereof are similar to those produced by the apparatus shown in Fig. 1, and these currents may therefore be supplied to a power amplifier and amplified to the extent desired for impression upon a load circuit such as an antenna or a wire line.

Referring now more particularly to Fig. 1, l designates a piezo-electric crystal device of V trical Engineers,

i the level desired.

' ling to an additionalcoil 30 connected in the back circuit,

' one end of coil 10, the other I be connected to the cathode 23 of plifier 20, which cathode maybe energized by high c ielectric constant, such for example as a crystal of Rochelle salt exhibiting the hour glass configuration as described in my entitled Piezoelectric effect delivered before the American Institute of Elec on Oct. 9, 1919, and provided with electrodes 2 and '3 at opposite electrical poles and also provided with mounti plates 4 and 5 if desired. An acoustic ,iachragm such as a'conebv may be attached o a mechanical pole of the crystal device, e as to cause vibrat'on of the r Y e, aeration of corresponding elecoscilla ions when sound vibrations m cf (1 piezoelectric crystal device 7, or example as a quartz crystal, having and dimensions so chosen as to be nigh frequency which it is it, is a so provided, having c ectrodes 8 and 9 at the proper points, as known in the art. in this instance, a coil 1O my be provided inductively coupled to a second coil 11, one end of which second'coil may be connected to the grid or control elec trode13 of a thermionic amplifierlZ. The opposite endof the through a suitable source of potential l7 to the anode 14 of the said amplifier, and the cat 7 ode 15, energized by a suitable source of potential such as battery 16, isconnected to.

an intermediate point upon the coil 11. This arrangement forms what is known as a feed well known in the art, which may be adjusted to produce oscillations of substantially the desired frequency.

V A connection may be made between electrode 8 of crystal device 7 and electrode 3 of crystal device 1, and'connections also established from electrode 2 of crystal device 1 to the control electrode or grid 21, of thermionic vacuum tube amplifying system, grammatically as single tube; also, a connection may be inade from electrode 9 to endof .vhich may the ama suitable source of potential such as battery The anode 22 ofthe amplifier 20 may be connected through coil 26 and a potentral25 to the cathode clrcuit.

A second (201127 inductively coupled to coil source of 26, so as to form a transformer, may be connected to the input circuit of a suitable power amplifier, containing as many stages-as may be required to increase the power output to The output circuit of the power amplifier may include a coilz29 coupled to a load circuit such as an antenna, in any suitable manner, such as by inductive coup 1 quency oscillations produced by amplifie 12 coil 11 may be connected shown diawill be stabilized by piezoelectric crystal device 7, and thereby held to a very constant value.

Electrical oscillations corresponding to sounds such as speech and music directed against the acoustic device such as cone 6,.

will be produced by crystal device 1, and superimposed upon the high frequency oscillations suppl ed to grld 21, the result of whlch will be that in the output circuit of the arm extend desired withoutserious deformation or" distortion,and may thereafter be supplied to a load circuit such for example as an antenna. Referrmg now more part cularly to F g.

2, I have shown amodified form in which I I dispense with the separate oscillator 12, and its associated circuits, by arranging to have the amplifier 20 act as an oscillator. In this instance coil 40 may be provided in the output circuit of the amplifier 20, and an additional electrode ll may be provided on the crystal device 7.

One 1 end of coil 10 may be connected through the source of potential 25 to the anode 22 of tube 20 the other end of this coil will be connected to the cathode and'to one of the electrodes of'the crystal device,as for example electrode 41. A connection will also "be provided from an intermediate point on coil 40 toanother electrode of the crystal device 77, as for example electrode 8. Athird electrode 9 may then be connected to electrode 3 of crystal device1,electrode'2 of which will be connected as before to the control electrode 21of the amplifier 20. 7

'Under these conditions, by proper adjustment of the apparatus, it will be found that the currents flowing from the output 40 through the crystal device T to the cathode cause mechanical and electrical vibrations of this devlce at its natural frequency,'resulting 1n the product1on of an electromotlve force between the electrodes ll and 9, which is impressed upon the control sustained oscillations of desired frequency are produced in the output circuitof amplifier 20. These oscillations will bra-modulated as before, through the action of crystal device 1 in response pressed upon cone 6: and may be amplifiedelectrode, I whereby f,

to, acoustic vibrations 1mby a suitable power amplifier tot-he extent desired before being supplied to the load."

Since the capacitive impedance of crystal device 1 to frequencies of the order of those desired for transmission is relatively low, it

is not necessary to provide aby-pass'for these high frequencyoscillations around this crystal device. On the other hand,however, the impedance of the crystal device 7 to relatively low frequencies corresponding to speech and music, is usually relatively high, and for the best results, it may be desired to provide a shunt path for low frequency currents around this crystal, which may be formed by the connection of a suitable coil 42 between electrodes 8 and 9, in the first instance, and electrodes 9 and ll in the second. This coil, as will be understood, should have sufiicient inductance to act as a choke to the high frequencies produced by the crystal device 7, but as a path of low impedance to the low frequencies produced by the crystal device 1.

The piezo-electric crystal devices herein diagrammatically shown may comprise devices of any suitable material, size, shape, and arrangement known in the art and suitable for the purpose, and may for example comprise arrangements described and claimed in my copending applications Rx Entitled Serial No. Filed & Cast piezo-electric device 155,897 Dec. 20, 1926 Composite piezo-electric crystal device 155, 898 Do Composite piezoelectric torsion device 155,899 Do Composite piezo-electric acoustic device 160, 358 Jan. 11, 1927 Internally clamped composite piezoelectric torsion device 155,900 Dec. 20, 1926 Internally clamped composite piezo-electric acoustic device 160, 359 Jan. 11, 1927 Orientation of component crystals in composite piezo-electric devices 155,902 Dec. 20, 1926 While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing from the spirit and scope of my invention, as will be understood by those skilled in the art.

I claim:

1. In combination, an electrical circuit, means for setting up electrical oscillations therein, a piezo electric device in said circuit adapted to control the frequency of said 0scillations, another piezo electric device in said circuit, and means for mechanically vibrating the second named piezo electric device, said second named piezo electric device being adapted to modulate said oscillations in accordance with the mechanical vibrations.

2. In an oscillatory circuit, the combination of a piezo electric device adapted to change its electrical characteristics in accordance with mechanical vibrations of audio frequency, a second piezo electric device adapted to resonate at a super-audible frequency and thereby to control the frequency of the oscillations in said circuit, and an inductance connected in parallel with said second named piezo electric device wherein the first named piezo electric device offers a low impedance to said super-audible oscillations and said inductance offers a high impedance to said super-audible oscillations and a low impedance to oscillations of audio frequency.

3. In combination, an electron discharge device having an anode, a cathode and a control electrode, input and output circuits interconnecting said electrodes, sources of potential for said electrodes, means for generating electrical oscillations in said input circuit, a piezo electric device responsive to mechanical vibrations, means for impressing sound waves thereon, a second piezo electric device resonant at the frequency of said oscillations, said piezo electric devices being connected in series in said input circuit, and an inductance shunted across the second named piezo electric device.

In testimony whereof I hereunto afiix my signature.

ALEXANDER McLEAN N ICOLSON.

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