US2421138A

US2421138A - Wave signal translating arrangement

Info

Publication number: US2421138A
Application number: US597037A
Authority: US
Inventors: Harold A Wheeler
Original assignee: Hazeltine Research Inc
Current assignee: Hazeltine Research Inc
Priority date: 1945-06-01
Filing date: 1945-06-01
Publication date: 1947-05-27
Anticipated expiration: 1964-05-27
Also published as: BE474969A; GB612371A; CH260751A

Description

y 7, 1947. H. A. WHEELER 2,421,138

7 WAVE SIGNAL TRANSLATING' ARFANGEMENT Filed Jun 1, 1945 i To Decoder K12 |3- o PULSE- 9 O T|ME PULSE- E v MOI J U QE DELAY E. i- 55 --OSCILLOSCOPE RECIEVER NETWORK LIMITER 0 o o 9 0 Jill 4 l8 (fiols) GAIN- CONTROL SYSTEM Volts INVENTOR. HAROLD A. WHEELER ATTORN Y Patented May 27, 1947 ZAZLBS WAVE SIGNAL TRAN SLATING ARRANGEMENT Harold A. Wheeler, Great Neck, N. Y., assignor, by mesne' assignments, to Hazeltine Research, Inc, Chicago, 111., a corporation of Illinois Application June 1, 1945, Serial No. 597,037

9 Claims.

This invention is directed to wave-signal translating arrangements for translating pulse signals which may have one or more sloping edges. Although the invention is subject to a variety of applications, it is especially suited for use ina radio-locating and direction-finding system of the type utilizing pulse-modulated signals and it will be particularly described in that connection.

In one radio-locating and direction-finding system of the type under consideration, the desired information is conveyed by means of a pulse signal, coded in accordance with a prescribed coding schedule. For example, the coded signal may include a pair of pulse components, individually having a fixed duration and a time separation that is variable in a code sequence. In the preferred system, the coded signal is received, shaped and passed on to a decoder unit which automatically derives the desired information by deciphering the received signal.

The coded signal is shaped, in the usual case, by means of a conventional limiter in which the received pulses are clipped off at a predetermined amplitude level. Such an arrangement performs the desired wave-shaping function but is subject to an operating limitation which may be undesirable in certain installations. This limitation follows from the fact that variations in signal strength of the received signal cause variations in the slope of leading and trailing edges of the pulse components. As a consequence, the ordinary limiter which operates at a fixed amplitude level produces in its output circuit pulse signals having pulse widths that also vary in accordance with the received signal strength. This becomes objectionable where the pulse widths of the code components of the received signal are significant.

Circuit arrangements for responding to the sloping edges of applied pulse signals have already been proposed. In one prior arrangement a contrcl potential is derived, having a magnitude that varies with the slope of one edge of the applied signal. The potential is developed across a conventional time-constant circuit and is used to control the gain of a receiver to maintain the amplitude of the signal delivered therefrom within a relatively narrow range fora wide range of received signal intensities. Such control arrangements, while providing a suitable automatic-gain-control potential, are not effective to shape the edges of the translated pulse signal as is required to avoid the aforementioned pulsewidth variations inherent in conventional limiting of pulse signals which have sloping edges.

It is an object of the present invention, therefore, to provide an improved wave-signal translating arrangement for translating pulse signals which substantially avoids one or more of the aforementioned limitations of prior arrangements.

It is another object of the invention to provide an improved wave-signal translating arrangement for translating a pulse signal which may have a sloping edge and foreffectivelysuppressing the sloping edge.

It is a particular object of the invention to provide an improved wave-signal translating arrangement for translating a pulse signal which may have sloping, leading and trailing edges and for deriving therefrom a pulse signal having substantially vertical edges.

In accordance with the invention, a wave-signal translating arrangement for translating a pulse signal which may have a sloping edge comprises a controllable signal-translating channel for supplying the signal to a utilizing device. The arrangement has means connected to the channel at one point and responsive to the sloping edge of the pulse signal for deriving a control potential. Also, means are provided for applying the control potential to a succeeding point in the channel to interrupt signal translation at the succeeding point for an interval having a duration approximately equal to, and a substantial time coincidence with, the occurrence of the sloping edge of the pulse signal at the succeeding point, effectively to suppress the sloping edge in the signal translated through the channel.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 represents a Wave-signal translating arrangement including the present invention in a preferred form, and Fig. 2 comprises graphs utilized in explaining the operation of the Fig. 1 arrangement.

Referring now more particularly to Fig. l, the wave-signal translating arrangement there represented may be considered as the receiving unit of a radio-locating anddirection-finding system. The arrangement comprises an antenna-ground system Ill, H for intercepting pulse-modulated direction-finding signals which may have sloping, leading and trailing edges. The antenna system Ill, l I is coupled to the input terminals of a, controllable signal-translating channel through which received pulse-modulated signals are supplied to a utilizing device. This channel is provided by a pulse-modulated wave-signal receiver |2, a time-delay network i3, a pulse amplifier and limiter I4, and an oscilloscope l connected in cascade in the recited order. The receiver unit l2 may constitute any conventional well-known arrangement for receiving and demodulating pulse-modulated signals, such as a receiver of the superheterodyne type. The pulse amplifier and limiter I4 may comprise an amplifying arrangement of any desired number of stages in at least one of which applied pulse signals are shaped by clipping and amplitude-limiting actions. This may be accomplished by ad lusting the operating potentials of the stage so as to translate only an intermediate amplitude range of an applied pulse signal, eliminating the maximum and minimum levels thereof by way of the well-known anode-current saturation and anode-current cutoiT phenomena, respectively. The time-delay network 3 and oscilloscope I5 may be of conventional constructions, the oscillos'cope preferably being of the cathode-ray type used to monitor the wave-signal translating arrangement under consideration. The pulse-modulated signal obtained in the output circuit of limiter l4 may be applied to an automatic decoding unit (not shown), as indicated by arrow 5.

A gain-control system I! is coupled by way of conductors l8 and Hi to the output circuit of receiver It. for controlling the gain of channel |2-| 5, inclusive. Preferably, the gain-control system is or the type which utilizes the quiescent or noise signal output of receiver IE to stabilize the receiver gain at a desired normal value. If desired,there may also be associated with receiver |2 a pulse gain-control system of the type particularly described in copending application Serial No 597,035, filed concurrently herewith in thename or Harold A. Wheeler and assigned to the same assignee as the present invention. Such a pulse gain-control system is insensitive to the quiescent signal output of receiver [2, that is to say, it is ineffective in the absence of a received pulse-modulated signal. Upon receipt of such a signal, however, the pulse gain-control system responds rapidly to develop a control potential for materially reducing the gain of channel |2-| 5, inclusive, early in the duration of the received signah The condition of reduced gain endures for an interval slightly greater than the duration of the received pulse-modulated signal and is effective to suppress the efiects of spurious or interfering signals which may be received along with a coded pulse-modulated signal, as particularly described in the copending application. An output circuit of the noise gain-control system H is coupled to a control input circuit of receiver l2 for applying control potentials to the receiver for the purpose of controlling its gain.

The signaltranslating arrangement has means, designated 20, connected to the signal-translating channel at one point and responsive to the sloping edge of a received pulse-modulated signal for deriving a, control potential. For the illustrated embodiment where it is desired to effect a shaping or correction of both the leading and trailing edges of received pulse signals, this means comprises a differentiating circuit for deriving a first pair of pulses having opposite polarities. More specifically, unit 20 includes an amplifier comprising a triode vacuum tube 2| having an anode impedance 22 and an equal cathode impedance 23 arranged to provide a balanced output circuit for the amplifier; Acou'pling condenser 24 and leak resistor 25 in conjunction with conductors I8 and I9 connect the input circuit of tube 2| to one point, specifically the output circuit of receiver l2, of channel |2-|5, inclusive. A condenser 26 and resistor 21 coupled to the anode impedance 22 of amplifier 2| constitute a first difierentiating circuit while a. condenser 28 and resistor 29 similarly connected to the cathode impedance 23 constitute a second differentiating circuit. Each such circuit is selected to have a time constant which is very much less than the slope time, that is, the duration of the slope portions of the pulse signals applied to unit 20 from receiver |2.

A full-wave rectifier system is associated with the differentiating circuits for developing, from a first pair of pulses derived in the difierentiating circuit, a second and corresponding pair of pulses which individually are of the same polarity. The rectifying system comprises a first diode 3B coupled between resistor '27 and acoinmon load impedance 3| and a second diode 32 coupled be tween resistor 29 and common load impedance 3|. A battery 3G or other potential source ap= pliesan amplitude delay bias to each

diode

30 and 32, rendering the rectifier system unrespon sive to the quiescent signal translated in channel |2-|5, inclusive, in the absence of a received pulse-modulated signal. A connection 33 extending from the common load impedance 3| to a control input terminal of unit i l constitutes means for applying the pulses of control potential derived in unit '20 to such a succeeding point in the channel as to interrupt signal translation thereat for an interval approximately equal to, and occurring in time coincidence with, the occurrence of the edges of the pulse signal at this succeeding point to suppress theeclges of the signal translated in channel |2-|5, inclusive.

While a transmitting unit is customarily associated with the arrangement represented in Fig. l. to complete the radio-locating and directionfinding system, the present invention may be clearly understood from a consideration or the receiver portion only. For this reason the re mainder of the direction-finding system has been omitted from the drawing. The operation of the Fig, l arrangement is represented in part by the curves of Fig. 2. I

Curve A represents the signal output obtained from receiver 12 of the signal-translating channel |2|5, inclusive. The low-amplitude signal portions designated S denote the quiescent sig-' nal output of the receiver obtained in the absence of a received signal. This quiescent signal is initiated by and represents inherent disturbances within the receiver as, for example, thermal agitation noise, shot effect and the like. Gain-control system H utilizes the quiescent 'sig nal output to stabilize the receiver gain and maintain the amplitude of its uiescent signal at or below a preselected amplitude level. The pulse components P1 and P2 constitute a received direction-finding signal of the pulse-modulated type which has a duration T1. The time separation of these pulse components is coded in accordance with a prescribed coding schedule. Each of the pulse components P1 and P2 has sloping, leading and trailing edges and an intermediate flat or plateau portion.

The signal of curve A is applied to unit '20, amplified in tube 2| and differentiated in the differentiating circuits associated with the balanced output arrangement of tube 2|, The ,diifferentiated signal thus established across'resistor 2 9 has the wave form and polarity of curve B. It contains a pair of pulses of opposite polarity for each of the code components P1 and P2. The positive-polarity pulse P3 of each pair is derived from the leading edge of one of the code components and has a duration t1 equal to that of the leading edge of the code component. The negative-polarity pulse P4. of each pair is derived from and has a duration t2 equal to that of the trailing edge of each of the code components P1 and P2. The differentiated signal established across resistor 21 has an identical wave form but reversed polarity, a polarity reversal being obtained in translation of the signal of curve A through tube 2| to its anode circuit.

Each of

diodes

30 and 32 rectifies the pulses of negative polarity applied to its cathode from

resistor

21 or 29, developing across the common load'impedance 3! the signal of curve C. This signal also has a pair of pulse components representing the sloping edges of each of the code components P1 and P2 and of negative polarity. The first pulse P3 of each such pair corresponds with the leading edge of one code component and is obtained by way of diode 3!]. The alternate pulse P4 of each pair corresponds with the trailing edge of each code component and is derived through the alternate diode 32. The broken horizontal lines 61 and e2 designate the amplitud delay bias applied to the diodes 3i! and 32. The delay bias is such that signal components of curve B which lie between the bias levels, such as the quiescent signal components Sq, are not translated by the rectifier system and hence do not appear in curve C. The negative-polarity control I pulses of curve C are applied as a pulse-modulated bias potential to a bias control circuit of pulse amplifier and limiter l l. Broken horizontal line e3 represents the cutoff level of unit 14, demonstrating that each of th control pulses P3 and P4 is effective to bias the pulse amplifier and limiter to anode-current cutoff for intervals which correspond to the duration of the leading and trailing edges of code components P1 and P2.

In order to simplify the graphical representation, the curves of Fig. 2 neglect the time-delay of network 13 and, additionally, neglect the delay in deriving the control pulses of curve C. In practical circuit applications some time delay is generally encountered in the derivation of the desired control pulses. Accordingly, the delay of network [3 is adjusted to acorresponding value so that the control pulses P3 and P4 of curve C block unit It and interrupt signal translation thereat during spaced operating intervals which have a duration approximately equal to, and a substantial time coincidence with, the occurrence at unit H! of the leading and trailing edges respectively of the code components P1 and P2. Therefore, the output signal of pulse amplifier and limiter It has the wave form of curve D. The code components P1 and P2 of curve D represent that portion of each of code components P1 and P2 of curve A that is translated by unit I4 in view of the control established thereon by the control potential of curve C. Specifically, the control potential of curve C, by blocking unit It during the intervals t1 and t2, suppresses or eliminates the sloping edges in the signal translated. Therefore, the code components P1 and P2 of curve D correspond with that fraction of the flat or plateau portion of each component P1 and P2 that occurs within the limiting levels of limiter M, which levels are represented by horizontal lines E and F. The code components of curve D have a width that is independent of the limiting levels E and F since the sloping edges of the code components are not translated by unit Id.

The signal of curve D, in turn, is applied to the oscilloscope it: where the performance of the channel l2-l5, inclusive, may be determined by reproducing the wave form of curve D on the screen of a cathode-ray tube in well-known fashion. This output signal of the limiter l4 may also be supplied to the automatic decoder (not shown) wherein the coded information conveyed by means of the time separation of code components P1 and P2 is deciphered. Unit 20 which suppresses the sloping edges of the translated code components permits the limiting action of unit Hi to be accomplished without effecting the pulse width of the code components supplied to the decoder. This assures improved operation of the decoding mechanism.

The broken-line curve portions of curve D represent the signal output of a conventional limiter having the limiting levels shown by horizontal lines E and F but operating upon the sloping portions of the code components as well as the fiat or plateau portions thereof. It is evident that in such an arrangement the Width of the limited pulses varies in accordance with the slope of the leading and trailing edges of the code components as well as the limiting levels. This result is avoided by the inclusion of unit 20 in the signal-translating arrangement of Fig. 1.

In the illustrated embodiment of the invention the control pulses of curve C derived at one point in channel I245, inclusive, are applied to a succeeding point in the channel so as to suppress both the leading and trailing sloping edges from the signal translated. By omitting the function of either diode 39 or 32, the arrangement may be utilized to suppress only one of the sloping edges of the pulse components where this operation should be desired. Also, the time-delay network i3 need not necessarily take the form of a pure time-delay mechanism. Where a sufficient number of stages are included in unit it, the time of translation therethrough may correspond with the delay of unit 25 in deriving the control pulses. In such a case connection 33 may be made directly with a particular stage of unit Hi wherein the sloping edges of the pulse signals occur in time coincidence with the control pulses obtained from the rectifier system of unit 26 While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that Various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A wave-signal translating arrangement for translating a pulse signal which may have a sloping edge comprising, a controllable signal-translating channel for supplying said signal to a utilizing device, means connected to said channel at one point and responsive to said sloping edge of said signal for deriving a control potential, and

means for applying said control potential to a succeeding point in said channel to interrupt signal translation at said succeeding point for an interval having a duration approximately equal to and a substantial time coincidence with the occurrence of said sloping edge of said signal at said succeeding. point efiectively' to: suppress said sloping edge in thesignal translated through. saidchanneh 2. A wave-signal translating arrangement, for translating a pulsesignal vvhiclzl may have a sloping. edge comprising; a controllable. signal-trans:- lating channel for supplying said signal to a utilizing device, meansincluding a diffierentiating circuit connected; to said. channel: at one point. and responsive to said: sloping edge of said. signal for deriving. a control! potential,. and means for applying: said control potential to a succeedingpoint in said channel to interrupt signal translation at said; succeeding point for an interval a duration approximately equal to and. a. substantial time coincidence with the occurrence of said sloping edge of said signal at said succeed:- ing; point edectivel-y' to suppress said sloping edge in the signal translated through said channel.

3. A wave-signal translating arrangement for translating a pulse signal which may have a sloping edge comprising, acontrollable signaltranslating channel for supplying; said signal to autili-zing device, means connected to, said channel at one point and responsive to said sloping edge of said signal for deriving, a control potential, time-delaymea-ns. in said channel. connected between said one point and a succeeding point for delaying said signal between said points by an interval corresponding to the time delay in. deriving said control potential, and means, for applying said control potential to said succeeding point to interrupt signal, translation thereat for an interval having, a duration approximately equal to and asubstantial time coincidence with the. occurrence of said sloping edge of said signal at said succeeding point effectively to suppress said sloping edge the signal. translated through said channel.

4. A wave-signal translating arrangement for translating a pulse signal; which may have a. sloping edge comprising, a controllable signaltranslating channel for supplying said signal to autilizing device; means connected to said channel at one point for differentiating said signal. to derive a pulse of control potential having the same duration as said sloping. edge, time-delay means in said channel connected between said one point and a succeeding point, for delaying said signal between said, points by an interval corresponding to the time delay in deriving said control potential, and means. for applying. said control potential tosaid succeeding point.- to. interrupt signal translation thereat for an interval. having a duration approximately equal to and a substantial time coincidence with the oc cur-rcnce of said sloping edge of said signal at said succeeding point effectively to suppress said sloping edge in the signal translated through said channel.

5. A wave-signal translating arrangement for translating a pulse signal which may have a sloping edge comprising, a controllable signal-translating channel. for supplying said signal to a. utie lizing device, means connected to said channel at one point for difierentiating and rectifying said signal to derive a pulse of unidirectional potential having a predetermined polarity and having the same duration as said sloping edge, time-dolay means in said channel connected between said one point and a succeeding point for delaying said signal between said points by an inter-- val corresponding to the time delay in deriving said control potential, and means for applying said control potential to. said succeeding point:

to interrupt signal translation thereat for aninterval having a. duration approximately equalto and a substantial time coincidence with the occurrence of said sloping edge of said signal at said succeeding point efiectively to suppress said sloping edge-in the signal translated through said channel.

6'. A. wave-signal translating arrangement for translating a pulse signal which may have sloping, leading and trailing edges comprising, a controllable signal-translating channel for supplying said signal to a utilizing device, means connected to said channel atone point and responsive to each of said sloping, leading and trailing edges for deriving therefrom a pair of spaced pulses of control' potential having a duration equal to that of said leading-and; trailing edges respectively, timedelay means.- in said channel connected between said one point and: a. succeeding point for delaying said signal between said points by an interval corresponding to. the time delay in deriving each of said pulses of control potential, and means for applying said pair of control pulses to said succeeding point to interrupt signal translation thereat during spaced intervals. having a duration approximately equal. to and a substantial time coincidence with the occurrence at said succeeding pointofsaid leading and trailing edges respectively of said signal effectively to suppress said sloping edges in the signal translated through said channel.

7. A. wave-signal translating arrangement for translating: a.- pulse. signal which may have; slopns, leading. and trailing edges comprising, a controllable signal-translating channel for supplying said signal to a. utilizing device, means connected to said channel at one point for differentiating said signal to derive a first pair of pulses having opposite polarities and a duration equal to that of said leading and trailing edges respectively, full-wave rectifying means for developing from said first pair of pulses a second and corresponding pair of pulses of control potential individually having a given polarity, time-delay means in said channel connected between said one point and a succeeding point. for delaying said signal between said points. by an interval corresponding to; the time. delay in deriving each of said pulses of control potential, and means for applying said pair of control pulses to. said succeeding point to interrupt signal translation thereat. during spaced intervals: having a duration approximately equal to and a substantial time coincidence with the occurrence at said succeeding point. of said leading and trailing edges respectively of said signal effectively to. suppress said sloping edges in the signal translated through said channel.

8- A wave-signal translating arrangement for translating a pulse signal which may have a slopin edge comprising, a. controllable signal-trans,- lating channel for supplying said pulse signal to a utilizing device and efiective in the absence of said pulse signal to translate a quiescent signal representing inherent disturbances within said translating arrangement, means connected to said channel at one point and unresponsive to said quiescent. signal hut. responsive. to said slopin edge. of said pulse signal for deriving a control potential, and means for applying said control potential to asucceeding point in said channel to interrupt signal translation at said succeeding point for an interval having a duration approximately equal toai-nd a sulo'stantial' time coincidence with the occurrence of said sloping edge of said said time-delay network being effective to delay said pulse signal by an interval corresponding to the time delay in deriving said control potential, and means for utilizing said control potential to bias said pulse amplifier to cutoiT for an interval having a duration approximately equal to and a substantial time coincidence with the occurrence of said sloping edge of said signal at said succeeding amplifier effectively to suppress said sloping edge in the signal translated through said channel.

HAROLD A. WHEELER.