US1400591A - Electrical wave transmission - Google Patents

Description

C. D. EHRET.

ELECTRICAL WAVE TRANSMISSION.

APPLICATION FILED MAR. 12, I9I9.

Patented Dec. 20, 1921.

CORNELIUS D. EHRE'I, OF PHILAD ELPHIA, PENNSYLVANIA.

ELECTRICAL WAVE TRANSMISSION.

Specification of Letters Patent. Patented De 20, 1921 Application'flled March 12, 1919. Serial No. 282,166.

To all whom it may concern:

Be it known that I, CORNELIUS D. EHRn'r, a citizen of the United States, residing in the city and county of Philadelphia, State of Pennsylvania, have invented a new and useful Electrical Wave Transmission, of which the following is a specification.

My invention relates to a method of and apparatus for electrically transmitting speech by recourse to carrier waves both in systems where the energy of those waves is radiated or otherwise transmitted through the natural media, and where the carrier wave is in the form of a current transmitted over a conductor or conductors extending between the transmitting and receiving stations.

My inventionresides in a method of and apparatus or system for electrically transmitting speech, or sound waves in general, wherein energy modulated. in accordance with sound waves or speech is impressed upon the plate or anode circuits of a thermi-' onic oscillation producing means, whereby different groups of high frequency oscillations or. carrier waves are produced whose amplitude varies in accordance with the speech or soundwaves, the envelop of the successive groups representing the complete message, such energy being supplied as the plate or anode circuit energy of and as distinguished from the usual direct current source employed for energizing the plate or anode circuit.

By such method and apparatus no high frequency or carrier wave energy is radiated or impressed upon the line conductor until the existence of speech or sound waves; that is to say, no high frequency energy comes into existence or is radiated or impressed upon the line conductor until the microphone is actuated by speech orother sound waves.

My invention resides further in a method and apparatus or system of the character referred to, wherein the telephonic current is first amplified before conversion into the hi h frequency carrier wave; energy.

y invention resides further in a method and apparatus or system of the character referred to in which the high frequency or carrier wave energy produced asdescribed is amplified before radiation thereof into the natural media or impression thereof on a line conductor.

in the absence My invention resides further in a method and apparatus or system of the character referred to wherein high frequency current modulated .in accordance with speech or sound waves is converted into high frequency or carrier wave energy of different, preferably higher, frequency.- s

For an understanding of my method and for an illustration of some of the various forms my apparatus may take, reference is to be had to the accompanying drawing, in which:

Figure 1 is a diagrammatic View of apparatus embodying my invention and suitable for carrying out my method.

Fig.2 is a diagrammatic View of a modified form of apparatus suitable for a simplified'method of carrying out my invention.

Fig. 3-is a diagrammatic view of a modified form of apparatus embodying my invention and suitable for carrying outmy method.

Referring to Fig. 1, a microphone m is connected in circuit with a suitable'sourceof current, as a battery a, in the primary of a transformer 25 whose'secondary is connected directly to the circuit of the grid 9 of an amplifier A of suitable type, in this instance of thermionic type having in association with the grid 9 the anode or plate p and the filament or cathode f rendered incandescent by current from the battery I). In the grid circuit; may be included if desired or suitable, a device cwhich may be either a condenser or a battery, as well understood in the art. In the plate circuit of the amplifier formation, but preferably a step-uptransformer delivering currentat potential high enough, as regards the smallest amplitude of the voice current it is desired shall be transmitted, to equal and preferably exceed the lowest potential suitable for operating the anode circuits of the oscillator O. The opposite ends of the transformer secondary. are connected, respectively, to the plates or anodes p and p of a thermionic oscillator 0 comprising, in addition, the grid 9 and incandescent filament or cathode f. Connected across thesecondary of the transformer t, are the condensers C and C preferably variable to attain equal capacity, or, in any event, to cause oscillations of the same frequency in and by cooperation with the inductance L, whose one terminal connects to a point between the condensers C and C and to a variable mid-point on the secondary of the transformer t,, and whose other terminal is variable and connected to the filament f. The grid circuit is coupled to part of the inductance L by the variable inductance Z. In the grid circuit may be employed if suitable or desirable a condenser c. a

In inductive relation with the inductance L is the variable transformer secondary L whose one terminal connects through the variable non-inductive resistance 7*, which may be adjusted to suitable value or which may be entirely cut out, to the grids g, g of the high power amplifiers A A any number of which may be connected in parallel with each other as indicated, as by parallel connection of their plates, grids and filaments. For energizing the plate circuits may be provided the battery'or other source of current al and in the grid circuits may be connected the battery 6 with its negative terminal presented to the grids. Connected across the grid circuit, upon closure of the switch e, is a variable condenser C for tuning the grid circuit to the frequency of the oscillations derived from the secondary L However, it will be understood that .either or both the condenser C and the resistance 1" may be omitted.

connectedthrough an adjustable inductance L to the antenna or radiating structure R of a radio system. Or the transformer secondary L may connect to any suitable line conductor \or line conductor system extending between transmitting and receiving stations.

The operation as follows:

Uttering speech or sound waves against the microphone m Varies the current from the battery a, and the resultant current having sound wave or speech modulation is transformed by the transformer t and delivered to .the amplifying apparatus A,

. which amplifies the telephonic energy to any suitable'fidegree. For this purpose a plurality of amplifier devices A maybe employed, either in parallel or in cascade.

The amplifiedenergy is then impressed by transformer t upon the anode or plate circuits of the oscillator O, with the result that,

all the undulations or frequencies of positive sign or polarity from the secondary-of the transformer t are converted by one of The plate circuit of. the amplifiers A A, includes the adjustable transformer primary L in circuit withthe anode circuits, for example, that includplitude in accordance with speech or sound waves, the telephonic energy being the only energy supplied to the plate or anodecircuits, as distinguished from the ordinary case where a battery or the like is in the anode or plate circuit and the telephonic energy employed merely to vary the potential of the grid of the thermionic oscillator.

*ith an oscillator which employs a battery or the like in the plate circuit, with the potential of the grid altered in accordance with speech to vary the amplitude of the oscillations produced from energy of the battery, oscillations are continuously produced without regard to the fact whether or not speech or sound waves are being uttered against the microphone which controls the potential of the grid; and in a system employing such an oscillator the high frequency oscillations, or carrier wave is being continuously radiated or impressed upon I the line conductor.

By my method and apparatus, however, as described, the high frequency oscillations are not existent or produced except when the microphone is actuated.

The oscillations so produced directly by conversion from the telephonic energy are then suitably amplified, if desired, to practically any power; and as such, impressed uponthe radiating system B of a radio sys-' tem or analogous system employing the natural media, or upon a line conductor extending to the receiving station.

It will be understood that the amplifier also that the amplifiers A A, may be omitted. I

The omission of these amplifiers is'indicated in Fig. 2, where with the inductanceL the oscillator O intervenes a second oscilla- 1 tor 0 of a' known type employing in its plate circuit abatteriy d, which supplies the 115 A may be omitted; and it will be understood I ing modulated by the microphone m through the potential control of the grid 9 or oscillator 0 These high frequency oscillations are then transmitted through the transformer t, to the oscillator 0, wherein the half waves or oscillations of positive sign are converted into high frequency oscillations of the same or different frequency, higher or lower, in the circuit of one of the anodes, as 39,, while the half waves or oscillations of negative sign are converted into oscillations of such different frequency inthe circuit of the anode 79,. The energy of the oscillations of this second frequency, which also are modulated in accordance with the sound waves or speech uttered against microphone m, are impressed through transformer L, L either upon a line conductor or upon the radiating system or structure R. For example, the frequency of the oscillations produced by oscillator 0 may be 10,000, 20,000 or 30,000 cycles per second, or

more or less, while the frequency of the oscillations produced by the oscillator 0 may be any suitable higher frequency, for example, upwardly to 500,000 cycles per second, or

more.

OfFigs. 1 and 2,.it is characteristic that in the anode or plate circuits of the oscillator 0 no battery or other source of energy is present which, if .present, would cause conaccordance with speech until the microphone m is actuated by speech'or sound waves, or other means.

What I claim is: l

1. The combination with a thermionic oscillator comprising anodes, a transformer secondary connected thereto, grid structure and an electron-emitting body, inductance and capacities in the circuits of said anodes,

a coupling between the circuit of the grid structure and the anode circuits, said capacities connected in series across said secondary, a connection from between said capacities to said inductance, and means supplying modulated energy to said transformer including a source of continuous current, and means controlling the current of said source in accordance with sound waves.

2. A thermionic oscillator producing oscillations varying in amplitude in accordance with sound waves, comprising anodes, grid structure and electron-emitting means, a source of current representing sound waves, the terminals of said source connect-- ed, respectively, to said anodes, capacities in series with each other bridged across said anodes, a connection from a point between said capacities to a point intermediate the terminals of said source, and means coupling the anode and grid circuits.

' 3. Thermionic oscillation-producing means comprising a source of current representing sound waves, anodes connected to the different terminals of said source, grid structure, electron-emitting means, an inductance comprised in a coupling between the anode and grid circuits, capacities in series with each other bridged across said anodes, and a connection from a point intermediate the terminals of said source and a point between said capacities to said inductance, said source con-' stituting' the only source of curent in each of v said anode circuits. p

4. Thermionic oscillation-producing means comprising a source of current representing sound waves, anodes connected to the different terminals of said source, grid structure, electron-emitting means, a connection from said electron-emitting means to a point intermediate said terminals of said source, and means coupling the anode and grid circuits.

In testimony whereof I have hereunto affixed my signature this 11" day of March,

CORNELIUS D. EHRET.

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