US3243734A

US3243734A - Wave shaping device using saturable inductance

Info

Publication number: US3243734A
Application number: US320463A
Authority: US
Inventors: William J Bartik
Original assignee: Sperry Rand Corp
Current assignee: Sperry Corp
Priority date: 1963-10-31
Filing date: 1963-10-31
Publication date: 1966-03-29
Anticipated expiration: 1983-03-29

Description

March 29, 1966 w. J. BARTIK 3,243,734

WAVE SHAPING max/1cm USING SATURABLE mnucmncm Filed Oct. 51, 1963 United States Patent 3,243,734 WAVE SHAPING DEVICE USING SATURABLE INDUQITANCE William .I. Bartik, Jenkintown, Pa., assignor to sperry Rand Corporation, New York, N.Y., a corporation of Delaware Filed Oct. 31, 1963, Ser. No. 320,463 6 Claims. (Cl. 333-40) This invention relates to a device which is utilized to shape electrical signals or waveforms. More particularly, the device uses transmission line techniques and thin magnetic film phenomenon to provide a signal which has a leading edge or wave front which is steeper than an applied signal.

In the electronic field, there are many types of circuits which require high speed signals to effect switching or operation thereof. In many cases, the operation of the circuit is accomplished entirely by the high-speed, fast rise-time leading edge of an applied signal. Many types of circuits have been devised in order to provide such high-speed, fast rise-time signals. These circuits .include circuits for generating spike signals and the like. However, these signal generating circuits are generally of a complicated and complex nature. Therefore, the instant device is proposed in order to provide a wave shaping device which is relatively simple and uncomplicated.

In the instant invention, a two conductor transmission line, of either planar or coaxial configuration, is provided. The spacer between the conductors of the transmission line includes an insulation layer and a thin magnetic film layer. By using a thin magnetic film layer which exhibits uniaxial anisotropy, variations may be made or effected in the propagation of a signal supplied to the transmission line conductors. By properly controlling these variations, the leading edge or wave front of the applied signal may be varied such that the leading edge or wave front of the signal produced is much steeper, i.e., has a faster rise time, than the originally applied signal.

It is an object of this invention to provide a device for easily generating signals having wave fronts with fast rise-times.

Another object of this invention is to provide a device which is comprised of passive means and generates a Waveform with a steep-slope leading edge.

Another object of this invention is to provide a signal forming network which utilizes a transmission line having a thin magnetic layer included in the spacer between the conductors of the transmission line.

These and other objects and advantages of this inven- .tion will become more readily apparent when the following description is read in conjunction'with the attached drawings, in which:

FIGURE 1 is a schematic diagram of one embodiment of the invention;

FIGURE 2 is a graphic diagram showing the hysteresis characteristic for the thin magnetic film and the applied signals;

FIGURE 3 is a graphic representationof the originally applied signal and the signal which is developed by the instant invention; and

FIGURE 4 is a schematic diagram of another embodiment of the instant invention.

Referring now to FIGURE 1, there is shown one embodiment of the instant invention. This embodiment comprises a transmission line element 100 which is characterized by a coaxial configuration. That is, element 100 is in the form of an elongated cylinder having two conductors in which one conductor completely surrounds the other, the two conductors being coaxial and separated by a dielectric spacer. The inner conductor 18 may be any electrically conductive material, as for example, copper, silver or the like. The dimensions of the inner conductor are determined by the power to be carried by the device, the frequency of the signals to be applied and other parameters which are determined by the usage of the device. Typically, inner conductor 18 may have a diameter of approximately /8 inch. Outer conductor 10 is similar to inner conductor 18 in that it is an electrical conductor comprised of material such as copper, silver or the like. The thickness of outer conductor 10 may be on the order of 0.01 inch. Typically, the thickness of conductor 10 is determined by the skin depth of the signal applied to the device. The length of the device is determined as a function of the wavelength of the applied signal. The device must be at least M4 long in order that the leading edge of the signal can be affected.

The thin magnetic film layer 14 may be any type of thin magnetic film as for example the usual Permalloy magnetic material which is comprised of Ni and 20% Fe. This magnetic layer may have a thickness of approximately 10,000 A. and is the same length as the inner and outer conductors. The thin magnetic film layer is further characterized by a uniaxial anisotropy whereby HARD and EASY magnetization directions are exhibited by the film. That is, by applying a signal to the EASY or HARD direction, a different hysteresis characteristic is observed. In order to avoid the losses produced by the open or rectangular hysteresis characteristic, a thin magnetic film layer is provided with the EASY direction along the axis of the cylinder. In addition, the HARD magnetization direction of the thin film is defined to be in a circumferential direction around the axis of the cylinder.

The

insulation layers

12 and 16 may be any desirable type of insulation such as SiO which may be on the order of 300 A. in thickness. Moreover, one or the other of the

insulation layers

12 or 16 may be omitted, if desired. That is, only one of the insulation layers is required in order to prevent electrical contact between the inner and outer conductors. The construction of element shown in FIGURE 1, is a coaxial transmission line element which comprises the

conductors

10 and 18. The spacer between. the conductors comprises insulation layers 12 and/or 16'and thin magnetic film layer 14 as well as any desirable bonding layers (not shown). In accordance with well known transmission line theory, the application of an input signal to one end of the transmission line between the inner and outer conductors results in the propagation of a signal therealong. The velocity of the propagation of the signal is given by the equation The values of ,u and e are characteristics of the spacer of the device. Because of the nature of the spacer, it is relatively simple to vary the value of ,u thereof and to hold the value of e substantially constant. By varying the value of u, a variation in the propagation velocity of the signal is produced. If the propagation velocity of the signal is varied during the signal duration, then .the waveform of the signal produced is also varied. Thus, a waveforming operation is produced by the transmission line element.

Referring now to FIGURE 2, the graphic illustration of the hysteresis characteristic of the thin magnetic layer and the applied input signal shows more details of the operation of the device shown in FIGURE 1. The hysteresis characteristic 200 is the substantially linear hysteresis characteristic which is observed when a signal is applied to the magnetic material in the HARD magnetization direction thereof. This hysteresis characteristic represents a Substantially lossless operation and includes the

saturation levels

202 and 204 and the unsaturated region 206. The hysteresis characteristic 200, as shown by the solid line, is the idealized characteristic for the magnetic material 14. When the film is operating in the negative saturation region 202 or the positive saturation region 204-, the value of i thereof is approximately identical to the value of a for air. On the contrary, when the film is operating in the unsaturated region 206, the value of p. thereof maybe in excess of 10,000. These changes in the value of ,U. vary the inductance and coupling between the inner and outer conductors of the transmission line whereby the velocity of propagation of signals therealong also varies.

It is generally well understood in the art that the idealized hysteresis characteristic 200 (solid line) is relatively unobtainable. Therefore, the idealized characteristic is shown only so that the anisotropy values may be conveniently defined by the

points

212 and 214. In practice, the hysteresis characteristic incorporates

rounded corners

208 and 210. The value of ,4 which is related to the slope of the hysteresis characteristic, varies continuously (rather than discontinuously) from the saturated to the unsaturated region, and vice versa, with the rounded characteristic. As will become apparent subsequently, this continuous slope variation provides a smoother output signal.

The applied signal 250 is shown as a sinusoidal signal having typical sine Wave leading and trailing edges. The portion of the signal which is centered about the B axis (line 220) of the hysteresis characteristic 200 and which lies between the dashed

lines

216 and 218 is the portion of the signal which causes the thin magnetic film layer to operate in the unsaturated region. This portion of the sinusoidal applied signal is designated as 252. The peaks 254 of the applied signal which exceed the dashed lines 216 and/or 218 are the portions of the applied signal which cause the thin magnetic film layer to operate in the saturated region. That is, the dashed

lines

216 and 218 are projected from the knees or

corners

212 and 214, respectively, of the hysteresis characteristic 200. The

points

212 and 214 represent the negative and positive anisotropy values, respectively, of the magnetic material. Of course, in practice, there are no

discrete knees

212 or 214 as such but rather the

slopes

208 and 210 exist instead.

Referring now to FIGURE 3, there is shown, in solid line, a sinusoidal input signal similar to signal 250 of FIGURE 2. The signal 300 produced by the waveforming device is shown by the dashed lines. Furthermore, the +H and H values for the magnetic material in the waveforming device are represented by the dashed

lines

218 and 216, respectively. The signal portion 252 is the portion of the signal which is characterized by an instantaneous amplitude which is lower than the magnitude of the anisotropy value H so that the magnetic material operates in the unsaturated region. Therefore, the signal 250, as supplied to the waveforming device, has the portion 252 thereof delayed. The delayed portion of the leading edge of the signal is represented by the dashed line 302. would be parallel to the solid line portion 252 of the input signal. However, due to the curvature of the more realistic hysteresis characteristic, including

corners

208 and 210, shown in FIGURE 2, the value of a for the magnetic layer and, therefore, the inductance of the waveforming device varies whereby the dashed line portion 302 approaches and coincides with the solid line portion 252. In the preferred embodiment, this coincidence of the signals will occur at the saturation level of the magnetic film. If the coincidence does not occur precisely at this level, a slight discontinuity in the output signal may occur between the dashed signal portion 302 and the solid signal portion 254. That is, since the signal portion 254 is that portion of the applied signal which has the instantaneous amplitude greater than the magnitude of the saturation value H this portion of the signal sees a saturated magnetic layer such that there is no delay thereof. T herefore, the solid line portion 254 of the input signal 250 is indicative of and coincident with the output signal which is produced thereby. Similarly, when the applied signal begins the negative slope of the trailing edge thereof, the magnitude of signal 250 (represented by the solid line) falls below the saturation value H whereupon the dashed signal portion 304 is shown delayed with respect to the solid line signal portion 252a. Ag-ain, when the signal 250 reaches the crossover point at reference line 220, the negative portion of the signal which has an instantaneous amplitude less than H is delayed because of the 'characteristics of the waveforming device. This delayed signal is represented by the dashed signal 302. Again, the negative signal portion 254 which has an instantaneous amplitude greater than the negative saturation level, H;;, is not delayed because the value of ,u. of the magnetic material for this portion of'the signal is small. The signal portion 252a, which is the portion of the applied signal which has instantaneous amplitude less than the negative saturation value -H provides the delayed signal portion represented by dashed line 304. This type of operation continues as long as input signals are applied to the waveforming device.

Thus, it may be seen that a typical sinusoidal input signal may be applied to the waveforming device. The portion of this signal for which the instantaneous ampli tude is less than the absolute magnitude of the saturation level of the thin magnetic layer material in the waveforming device is delayed. On the other hand, the portion of the applied signal for which the instantaneous amplitude is greater than the absolute magnitude of the saturation level of the thin magnetic film material is undelayed. Therefore, there is a bunching or shaping of the leading edge of the signal. That is, part of the signal is delayed such that another part of the signal appears substantially closer thereto in time whereby a signal is produced which has a faster rise time on the leading edges thereof. Of course, the delay of the signal while the film is in the unsaturated region also'etfects the trailing edge of the signal whereby a less rapid trailing edge is produced. However, as noted supra, there are many types of circuits which require high speed triggering pulses wherein a pulse with a fast-rise-time leadingedge may operate as the triggering pulse and the slowspeed trailing-edge would be inconsequential. Moreover, this slow-speed trailing-edge of the signal would not produce any spurious results which would interfere with the operation of the high-speed leading-edge of the following opposite polarity pulse. Therefore, a signal with a high-speed fast-rise-time leading-edge is produced.

Referring now to FIGURE 4, there is shown another embodiment of the invention. That is, the coaxial struc ture shown in FIGURE 1 has been altered to form a Under idealized conditions, the dashed line 302 planar configuration. In the embodiment shown in FIG URE 4, similar components have the last two digits thereof similar to elements or components shown in FIGURE 1. Thus, the transmission line conductors which are fabricated of electrically conductive material, as for example, copper or silver, are designated as

conductors

410 and 418, respectively. The insulating layers 412 and 416 (one of which may be eliminated if so desired) may be SiO layers which provide electrical insulation between the

conductors

410 and 418. Again, the layer 414 is a magnetic material in the form of a thin magnetic film comprising a typical Permalloy material, as for example Ni, 20% Fe. The operation of this device when an input signal is applied thereto is identical to the operation of the device shown in FIGURE 1. Thus, the application of an input signal of alternating configuration, as for example a sinusoidal input signal, provides a de layed signal for the portion of the signal for which the instantaneous amplitude is less than the absolute magnitude of the saturation levels of the thin magnetic film 414. The portions of the input signal for which the instantaneous amplitude is greater than the saturation levels of the film 414 are undelayed. Therefore, the bunching of the leading edge of the applied signal occurs whereby a signal is produced which has a high-speed, fast rise-time leading edge.

The specific embodiments described spura are not meant to be limitative of the instant invention. Rather, these specific embodiments are meant to provide preferred illustrations of the inventive principles described herein. Therefore, modifications of the device may be made without departing from the principles and scope of the invention as described in the attached claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A waveshaping element to receive electrical signals of a substantially sinusoidal configuration and to produce electrical signals having a steeper leading edge than the signal received, said element comprising first and second parallel electrical conductors, a thin magnetic film layer exhibiting uniaxial anisotropy and having magnetically saturated and unsaturated operating conditions, at least one layer of insulating material, said magnetic layer and said insulating material being disposed between said first and second electrical conductors, said element producing a substantial delay only for electrical signals received thereby for which the instantaneous amplitude is such that said thin film operates in the unsaturated operating condition, said element producing substantially no delay for signals received thereby for which the instantaneous amplitude is such that said thin film operates in the saturated operating condition.

2. A waveshaping element to receive electrical signals of a substantially alternating configuration, said element comprising first and second parallel electrical conductors, said first and second conductors being arranged in coaxial and concentric relationship, a thin magnetic film layer exhibiting uniaxial anisotropy and having magnetically saturated and unsaturated operating conditions, a layer of insulating material, said magnetic layer and said insulating material being disposed between said first and second electrical conductors in coaxial and concentric layers, said element producing a substantial delay only for electrical signals received thereby for which the instantaneous amplitude is small enough such that said thin film operates in the unsaturated operating condition, said element producing substantially no delay for signals received thereby for which the instantaneous amplitude is large enough such that said thin film operates in the saturated operating condition.

3. In a waveshaping device, a pair of parallel electrical conductors, a thin magnetic film exhibiting uniaxial anisotropy, an electrically insulating layer, said thin film and said insulating layer being disposed between said pair of parallel conductors, said thin film being characterized by EASY and HARD magnetization directions, said thin film being oriented relative to said pair of conductors such that electrical signals which are applied to the conductors propagate therealong parallel to said thin film EASY magnetization direction whereby substantially lossless operation is achieved, said thin magnetic film further characterized by saturated and unsaturated operating conditions which affect the propagation of electrical signals along said pair of conductors.

4. In a waveshaping device, a pair of parallel coaxial electrical conductors, magnetic film layer exhibiting uniaxial anisotropy, an electrically insulating layer, said magnetic film layer and said insulating layer being concentric layers and disposed between said pair of parallel conductors, said magnetic film layer being characterized by EASY and HARD magnetization directions, said magnetic film layer being oriented relative to said pair of conductors such that electrical signals applied to the conductors propagate therealong parallel to said thin film EASY magnetization direction whereby substantially lossless operation is achieved, said magnetic film layer further characterized by saturated and unsaturated operating conditions which afiYect the propagation of electrical signals along said pair of conductors, said unsaturated operating condition being efiective to delay signals applied to said pair of conductors, said saturated operating condition eifecting substantially no delay to signals applied to said pair of conductors.

5. In a waveshaping device, a pair of parallel electrical conductors, a thin magnetic film exhibiting uniaxial anisotropy and characterized by EASY and HARD magnetization direction, an electrically insulating layer, said thin film and said insulating layer being disposed between said pair of parallel conductors, said thin film being oriented relative to said pair of conductors such that electrical signals which are applied to the conductors propagate therealong parallel to said thin film EASY magnetization direction whereby substantially lossless operation is achieved, said thin magnetic film further characterized by saturated and unsaturated operating conditions which atfect the propagation of electrical signals along said pair of conductors to the extent that the signal portion Which causes said thin film to operate in the unsaturated condition is delayed while the signal portion which causes said thin film to operate in the saturated condition is not delayed whereby the delayed signal portion is produced closer to the undelayed signal portion.

6. A waveshaping element for receiving electrical signals of a substantially sinusoidal configuration and producing electrical signals having a steeper leading edge than the signal received, said element comprising first and second parallel electrical conductors, a thin magnetic film layer exhibiting uniaxial anisotropy and having magnetically saturated and unsaturated operating conditions, the saturation level between said saturated and unsaturated operating conditions being defined by the anisotropy field value of said thin magnetic film layer, at least one layer of insulating material, said magnetic layer and said insulating material being disposed between said first and second electrical conductors, said element producing a substantial delay only for electrical signal portions received thereby for which the instantaneous amplitude is greater than said saturation level of said thin film, said element producing substantially no delay for electrical signal portions received thereby for which the instantaneous amplitude is less than said saturation level of said thin film whereby the delayed signal portions are produced substantially closer to the undelayed signal portions,

References Cited by the Examiner UNITED STATES PATENTS 2,871,453 1/1959 Bradley 333-31 3,051,891 8/1962 Jorgensen 323-76 3,102,048 8/1963 Gran et al 340-174 3,175,200 3/1965 Hofiman et al. 340174 HERMAN KARL SAALBACH, Primary Examiner.

A. M. MORGANSTERN, Assistant Examiner.