US2492134A - Pulse coding system - Google Patents

Description

Dec. 27, 1949 E. COLE PULSE CODING SYSTEM Filed NOV. 29, 1947 Patented Dec. 27, Y1949 UNITED STATES TENT trice PULSE ,CODENG SYSTEM` Application November ze, 1947, sel-gama 783,894.

(Clt 250V- 921) 4y clams. l

This invention relates to electrical. selective translation circuits` which may be termed amplitude class selectors. An amplitude. class yselector as here used refers to. an apparatus which has for its functionA the classification of. signals in' accordance with the amplitude ranges Within which said signals lie; and more specically, the production of` output indicationsk on a. channel specially reserved for signals having an amplituderlying within a given range.

Pulse: separation systemsfcr separating pulses and channelizing them in accordance with the range of amplitudes Withinv which theyk liev have many applications.. A.. system of amplitude: class selection has been previously proposed-for use in multi-channel communication systems utiliztixn'e'modulated pulses. The pulses of diier- ,ent channels-have diierent amplitudes and they are separated at the terminal or at a drop chan.- nel. relay station according to their amplitudes. I nthe previously proposed system` it is desired that the time modulation .of the pulses lbe retained atithe relay station for those pulseswhich are'to be retransmitted to some subsequent-terirninal station. In other systems it has been desirable to separate pulsesaccording to their amplitudes and to .count the number of pulseswithin given amplitude. ranges, Such systemsmay be of. especial utility in connection with nuclear counters for example.

Recently a number kof systems of communication have been p roposed,in which, instead. of transmitting a cor'itinuouslyy varying signal, there is transmittedinstead a: quantized signal; that is to say, pulse amplitude modulation is obtained Afrom the signal, and the pulses are then quantized in amplitude. Whenever a given pulse has an amplitude lying Within a specified range, another pulse havinga fixed amplitude, representing all amplitudes Within said range is transmitted instead of the original. By this process a continuously varying function is replaced by .a function which takes on discreet values only.

An object of the present invention is toprovide `an improved amplitude Class selector whichk relies for its operation upon the use of frequency sensitive circuits.

Another objectof the invention is to provide an improved amplitude class selector which is equally suitable for-the classification oiipulses and for the quantization o f continuously varyinefunotions.

In accordance with a feature of the invention',y

a signal :to be channellzedrln accordance with its amplitude is used to control the frequency of an oscillator, and the controlled frequencyis; then selected, or channelized, bvl means of,` frequency selective circuits.

s/,separate amplitude range ,and has particular application to the channelizing. of pulses in accordinyellton itself willi-behest understood loyrefer- In accordance with another feature of the inventiom automatic, frequency control means are arranged tocontrolthe frequencies applied to .the above-mentioned frequency' selective circuits so thatr although the frequency produced by said osciliator may yaryv .over a limited range, the frequency applied tothe input ofthe frequency selective circuits remains within narrow limits during said variation.

.In .accordance with: a further :feature of the invention, auxiliary oscillator is used to provide al wave which is heterodyned with the output oi they oscillator controlled in accordance withl thev amplitude oiv the input. signal. to be -chanpelized and the frequency of the auxiliary oscillator iscontrolled in accordance with the output of' a discriminator connected .to one of the above-mentioned frequency selective circuits.

The invention isV described inv connection with a. plurality of channels each corresponding to, a

ance with their amplitudes. It may also be read- Y to another..

varying function' into a number of channels, as the function changes from one amplitude range The above mentioned and other features and objects of: the invention and the manner of attaining them Will become more apparent andthe ence to the following description .of an embodiment of the invention taken in conjunction with Y the accompanyingA dra-Wings, wherein;

Fig.. i is a block diagram of an amplitude class selector constructed in accordancewith the principlesY oi"- this invention;

Fig. 2 isK a' set of curves which will be used' in explaining the'operation of the system of Fig. 1.

Referring now to- Fig. 1, I show a reactance tube' l to whichisappled the input complex Wave form,--Which maybe forl example; a speech Wave. Reactance` tube I controls the frequency of an oscillator 2' Which may loev operated atl any conc veulent-'frequency as, for. example, 50 to 60 megacycles.

isrtlicnlapplziedftoaplurality of ampliers 5. each off whichv tuned @to the .center oi a predeterelements of the tuned amplifier 5 in channel I.

In similar fashion the discriminator output characteristics of the remaining channelsY are centered at the resonance frequency of the corresponding tuned amplifier. The discriminator characteristics are arranged to be co-ntiguous and non-overlapping, as shown in Fig. 2 and to cover the entire range of the selected beat frequency output from the mixer 3. The frequency range f for each channel may be adjusted independently so that one channel may cover a range different from other channels. When the frequency of output-energy from mixer 3 is such as to lies Within the range of channel l, for example, the discriminator output voltage is applied to the reactance tube so as to control the oscillator 4, so

Vthat the mixed frequency is held near the center frefrequency of channel I This automatic quency control action Will remain effective until the discriminator output voltage begins to reverse and can no longer hold the output of the mixer within the pass band of channel l. Oscillator 4 Will then be released and the vmixer output will shift suddenly to some otherrfrequency lying in an adjacent or nearby channel dependent upon the input energy to the system. The process will be repeated at the new frequency. The result is that a signal is produced in the output of only one of the channels at a time.

The output of each tuned amplifier 5 is also applied to a corresponding detector 8, which may be a rectifier. The lower part of Fig. 2 shows the rectified voltage output of the corresponding tuned amplifier 'l for each of the channels. As shown in Fig. l, this rectifier' output is taken on separate output lines. Each channel is then applied to any necessary shaping amplifiers Q and to the utilization apparatus l0.

It is apparent that the above-described system functions equally well to classify pulses in accordance with their amplitudes as it does to quantize a continuously varying signal. The output of the system may be used for any of the purposes mentioned above. In particular, each output may be used to control separate signal generators which produce signals representative of a given amplitude class. Said signal generator may produce simple signals, such as a single pulse having a predetermined characteristic, 0r complex s-ignals, such as a group'of pulses having predetermined characteristics.

While I have described above the principles of my invention in connection with specic apparatus, it is to be clearly understood that this description is made only by way of example, and not as a limitation to the scope of my invention.

I claim:

1. A selective translator for channelizing a given electrical Wave in accordance with its amplitude, comprising a source of electrical oscillations, means for frequency modulating said oscillations in accordance with the amplitude of said wave, a plurality of tuned circuits, each tuned to approximately the center of an associated one of a plurality of continguous non-overlapping frequency ranges within the range of the frequency modulation of said oscillations, means for coupling the output of said source of electrical oscillations to said circuits, separate automatic frequency control means controlledby the output from each of said circuits for controlling the frequency of the energy applied to said circuitsover said associated one of said frequency ranges, and output means connected to each of said circuits.

2. A selective translator according to claim 1 wherein said means for coupling the output of said source of electrical oscillations to said circuits comprise a frequency converter coupled to a second oscillator controlled by said automatic frequency control means.

3. A selective translator for classifying signals in accordance with their amplitudes, comprising a first oscillator, means for frequency modulating the energy of said first oscillator in accordance with the amplitude of said signals, a second oscillator, a combining circuit for mixing the output energy of said first and second oscillators to produce a beat frequency, a plurality of amplifiers each tuned to approximately the center of an associated one of a plurality of contiguous nonoverlapping frequency ranges lying Within the range of said beat frequency, means for applying said beat frequency to said amplifiers, separate frequency discriminating means coupled to the output of each of said amplifiers for proportioning automatic frequency control voltages, means for controlling the frequency of said second oscillator in accordance With said voltages, a detector connected to the output of each of said amplifiers, and an output circuit for each of said detectors.

4. A selective translator comprising a source of electrical Wave energy, a rst oscillator, a reactance tube for frequency modulating the energy of said first oscillator in accordance With the amplitude of said wave energy, a second oscillator, a combining circuit for mixing the output energy of said first and second oscillators to produce a beat frequency lying Within a predetermined frequency range, a plurality of amplifiers each tuned to approximately the center of an associated one of a plurality of contiguous non-overlapping frequency bands all lying within said predetermined range, means for applying said beat frequency to said amplifiers, a separate frequency discriminator coupled to the output of each of said ampliers, and having a frequency response characteristic which is substantially linear over said associated one of said frequency bands, and which drops oif rapidly outside of said associated one of said frequency bands, a reactance tube for controlling the frequency of said second oscillator in accordance with the output of said frequency discriminators, a coupling between each of said frequency discriminators and said reactance tube, a detector connected to the output of each of said ampliers, and an output circuit for each of said detectors.

EUGENE COLE.

REFERENCES CITED Thefollowing references are of' record in the le of this patent:V

Hansell T Apr. 23, 1940

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