US2217280A

US2217280A - Ultra high frequency modulator

Info

Publication number: US2217280A
Application number: US232629A
Authority: US
Inventors: Winfield R Koch
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1937-07-28
Filing date: 1938-09-30
Publication date: 1940-10-08
Anticipated expiration: 1957-10-08
Also published as: GB504238A

Description

Oct. 8, 1940. w. R. KOCH ULTRA HIGH FREQUENCY MoDULATon Original Filed July 28. 1957 Z f 056/1. nro/.v

G waz/Mme )i6 mouz/eroe 59 ILL/970? :inventor Gttorneg Patented ou. s, 1940 i UNITED STATES'- PATENT OFFICE ULTRA HIGH FREQUENCY MODULATOR Winfield R. Koch, Haddonileld, N. J., assigner to Radio Corporation o! America, a corporation voi' Delaware 3 Claims.

My invention relates to ultra high frequency modulators, and particularly to means for frequency modulating an ultra high frequency resonant line circuit.

This application is a division of my copending application, Serial No. 156,054, filed July 28, 1937, Patent No. 2,174,701, Oct. 3, 1939, and entitled Ultra high frequency modulators.

It has been found that generators of currents of 50 megacycles per second and upwards may be better stabilized by resonant transmission lines than by piezoelectric crystal controls with their attendant difficulties. In one aspect, my invention contemplates varying the characteristic of such stabilizing ultra high frequency resonant line circuits to thereby frequency modulate the ultra high frequency currents impressed on said resonant lines. serves the dual purpose of frequency modulation and stabilization.

One of the objects of my invention is to provide an improved means for modulating an ultra high frequency current.

Another object is to provide an improved means for frequency or amplitude. modulating an ultra high frequency carrier.

Another object is to provide means for modulating the frequency of a high frequency oscillator by means of amplitude modulated currents of a lower frequency.

Another object is to provide means for varying y the effective stabilizing .frequency of a resonant line.

'An additional object is to provide a stabilizing resonant line including magnetostrictive material and means for modulating the output of the line by modulations of said magnetostrictive material.

A still further object of my invention is to provide means for modulating an ultra high frequency carrier without the application of electrical power.

My invention may be best understood by reference to the accompanying drawing, in which Figure l is a schematic circuit diagram of a resonant line and means for modulating said line,

Figure 2 is a modification of Fig. l and illustrates one embodiment of my invention applied to a concentric resonant line,

vFigure 3 is a circuit diagram showing a concentric line and a crystal modulator applied thereto,

Figure 4 is a circuit diagram illustrating ay modified form of magnetostrictive modulator and concentric line,

Figure 5 is a schematic illustration of a con- Thus employed, the resonant line (CL P19-171.5)

centric line which is modulated by sound waves. and

Figure 6 is a schematic diagram of a. circuit which produces frequency modulated waves through the use of amplitude modulated Waves.

Referring to Fig.`1, a pair of magnetostrictive members i, 3 form a resonant transmission line 5 which is connected to a thermionic oscillator l. The oscillator may be of the Barkhausen- Kurz, magnetron, or any suitable type of ultra high frequency current generator. The transmission line -5 is surrounded by a solenoid d which is energized by currents from a modulator il.

If no modulation currents are impressed on the resonant line 5, the frequency of the oscillator will be determined by the characteristics of the line, and in particular by its length. The line will stabilize the frequency of the oscillator. When modulation currents are impressed on the solenoid, these currents will exert forces on the magnetostrictive material of the members of the line, alter its length, and hence the resonant frequency of the line. Thus, the line both stabilizes the frequency and modulates the frequency of the currents generated by the oscillator.

Referring to Fig. 2, a concentric resonant line i3 is made up of an outer member i5, an inner member il, and an armature member i9 mounted on the top of the inner member. The outer member i5 and the inner member il are made of magnetostrictive material. A. solenoid 2i, surrounding the concentric line i3, is connected to a modulator 23. The line i3 is energized by an oscillator 25.

The foregoing construction shortens the length of the line because of the increased capacity be tween the armature i9 and the-end of the outer member i5. When the modulation currents are passed through the solenoid 2i, the length of the magnetostrictive member of the concentric line will be varied to thereby modulate the frequencyof the currents stabilized by the line i3. The undesirable effects' of eddy currents in the outer member i5 may be avoided by one or more slits in the outer member. The stabilizing effects of the line on the carrier currents of the oscillator will be retained and the modulation characteristics described above added thereto.

In Fig. 3 the modulation is effected, not by magnetostrictive forces, but by piezoelectric eifects. A concentric line 2l, comprising an outer member 29 and an inner member 3l, is coupled to an oscillator 32. The inner member is made hollow to thereby accommodate a connecting wire. A piezoelectric member 33 is mounted on a conductor 35 or electrode'which is4 insulated from a biasing battery t i \In the operation of the circuit of Fig. 3, the

oscillator currents are stabilized by the concentric line to thereby maintain the carrier frequency substantially constant. When modulation potentials are applied to the piezoelectric crystal- 33. the crystal will undergo changes in its thickness which will vary the capacity betweer the conductor 31 and the outer member 29. This variation in capacity will, in effect, modulate the concentric line 21 and hence the frequency of the carrier currents.

In the circuit of Flgi, a concentric line 43 is used. The line consists of Aarl outer member 45, an inner member 41, an amature 49 which is fastened to the inner member and a diaphragm 5l which is attached to the outer member 45. The diaphragm is made of bimetal; one of the metals is magnetostrictive. The diaphragm may be slotted to eliminate eddy current losses. A solenoid 53, energized by a modulator 55, actuates the magnetostrictive portion of the diaphragm.

Because one portion of the diaphragm is responsive to magnetostrictive forces, and the other is not, the diaphragm will bulge toward or away from the armature 49. 'I'he diaphragm movements will vary the capacity of the resonant concentric line and hence the period of carrier currents from the oscillator 51 which is coupled to the line 43.

`'I'he device illustrated in Fig. 5 can be used to modulate ultra high frequency oscillations Without the applicationof electrical energy. A concentric line 59, having an inner member 6i and an outer member 63, is suitably coupled to a generator 65 of ultra high -frequency oscillations. The upper portion of the inner member 6i includes an armature 61. An acoustic diaphragm.

69 is mounted on the end of the outer conductor 33 in spaced relation to the armature 61. Sound y waves may be impressed directly on the diaphrag'm 99. The diaphragm actuated by such waveswill vary the capacity of the concentric line and hence its resonant frequency. The variation in capacity will frequency modulate the line 59 and the output from the oscillator 65. This arrangement is particularly adapted to an ultra high frequency portable transmitter because of the absence of apparatus and the power supply usually required for modulation. In installations where weight and power supplies are not important factors, the' diaphragm 69 may be driven by a loudspeaker motor or the like.

A schematic circuit diagram of the application of the invention to an ultra high frequency transmitter and frequency modulator is shown in Fig. 6. In this circuit, a concentric line 1I is arranged with an outer member 13 and an inner member 15. A diaphragm 11 is mounted on the top of the outer conductor 13. An armature 19 is mounted on top of the linner member 15 and adjacent the diaphragm 11. vAn oscillator 8|, supplying ultra high frequency currents, is coupled to the concentric line 1i. A modulator 33 and an intermediate frequency oscillator 85 are arranged to supply a solenoid 91 with amplitude modulated intermediate frequency currents which actuate the diaphragm 11 through the reaction between the magnetic field set up by the currents in coil 81 and the field due to the eddy currents in the diaphragm. The intermediate 4vwill, however, follow the average amplitude or modulation wave. Thus operated, the carrier 5 ciu-rents from the oscillator 9| are stabilized by the concentric line and modulated as described. The greater the current through coil 81, the greater will be the eddy current induced in theK diaphragm, and the greater will be the depressing of the diaphragm, resulting in a greater decrease in frequency of oscillator 9|.

I have described several modifications of my invention which provide means for applying modulating signals to a resonant line which is used to stabilize an ultra high frequency oscillator. The resonant line serves the dual purpose of modulation and stabilization. and permits an efficient application of wide range frequency modulation to an ultra high frequency carrier. zo In this type of modulation, the anode voltage on the oscillator may be continuous, thereby maintaining high gridl impedance and low grid circuit power losses.

While I have specifically described the invention as applied to frequency modulation of the direct or double modulation type, it should be understood that my invention may be applied to vary the resonant frequency of a line connected between the oscillator and the output, thus varying the coupling between the oscillator and an antenna to modulate amplitude. It is also possible to apply the invention as shown to the automatic control of the frequency of the heterodyne oscillator of a superheterodyne receiver. In such cases, changes in the intermediate frequency currents are applied to the resonant line circuit to thereby change the frequency of the heterodyne oscillator to maintain constant intermediate frequency currents.

I claim as my invention:

1. An ultra high frequency device including in combination a source of oscillatory currents, a concentric line coupled to said source for controlling the frequency of said currents, a piezoelectric element interposed in said line the vibratory movements of which produce variations in the electrical properties of said line, and means for applying modulating potentials to said piezoelectric element whereby the vibratory movements of said element modulate the frequency of said currents. Y

2. An ultra high frequency device including, in combination, a source of oscillatory currents, a resonant line'coupled to said source for controlling the frequency of said currents, a piezoelectric element interposed in said line the vibratory movements of which produce variations in the electrical properties of said line, and means for applying modulating potentials to said piezoelectric element whereby the vibratory movements of said element modulate the frequency of said` currents.

3. An ultra. high frequency device including, 65 in combination, a source of oscillatory currents, a resonant line coupled to said source, a piezoelectric element interposed in said line the vibratory movements of which produce variations in the electrical properties of said line, and means 70 for applying modulating potentials to said piezoelectric element whereby the vibratory movements of said element modulate the frequency of said currents.

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