Electrical Component

Abstract

A distributed constant electrical component which may be utilized as a transmission or a delay line is disclosed which utilizes a length of non-conductive material such as a matrix of polytetrafluoroethylene in which is dispersed particles of a magnetic material such as powdered iron or powdered ferrite. Alternatively, a length of ferrite material may be used. At least a portion of a signal conductor extends through the length of material to provide a path for electrical signals. Both balanced and unbalanced lines are disclosed. There also is disclosed a device which may be used as a variable delay line which includes means for varying the spacing between portions of the length of material.

Parent Case Text

This application is a continuation-in-part of my copending application, Ser. No. 629,139, filed Apr. 7, 1967, entitled "Delay Line," now abandoned .

Description

This invention pertains to electrical components and, more particularly, to components which may be used as signal delay or transmission lines.

While, as noted above, the electrical component of the present invention may be utilized as a transmission line, it is particularly advantageous to use the same as a signal delay line. Hence, the component will be described below in the context of being a delay line. However, this is by way of example only and is not to be interpreted as being a limitation of the invention. That is, it will readily be obvious to those skilled in the art that the disclosure applies equally as well to transmission lines.

Signal delay lines have many applications in the fields of signal processing such as radar and computers. Generally, the delay lines are used to establish the time of arrival of signals at particular points in the signal processing circuits.

As the signal processing art grew, delay lines, depending on the overall delay required and the permissible signal distortion, developed as lumped-constant transmission lines or as distributed constant coaxial lines. Each type of line was relatively bulky. In fact, it has been known to use many feet of coaxial line to obtain fractions of millisecond delays. In the present era of miniaturization heretofore available delay lines are becoming impractical.

It is accordingly a general object of the invention to provide an improved signal delay line.

It is another object of the invention to provide an improved delay line of the distributed type which has a small volume to overall delay ratio.

It is a further object of the invention to provide such a delay line which is relatively inexpensive to manufacture and is at the same time very reliable and rugged.

Accordingly, an electrical component constructed according to the present invention includes a section of non-conductive material having a dielectric constant substantially independent of frequency, low dielectric loss and a magnetic permeability greater than unity. In contact with the material is signal conducting means for providing a path for the transmission of an electrical signal.

Other objects, the features and advantages of the invention will be apparent from the following detailed description, when read with the accompanying drawings which show, by way of example and not limitation, the now preferred embodiments of the invention.

In the drawings:

FIG. 1 is a perspective view, partially broken away, of an electrical component according to the invention;

FIG. 2 is a perspective view of an electrical component similar to that of FIG. 1 but which is controllably variable; and

FIG. 3 is a further modified embodiment of an electrical component constructed according to the present invention.

Referring to FIG. 1, there is shown an electrical component in the form of an unbalanced delay line 10 comprising a striplike element 12 and a signal conductor 14. Striplike element 12 comprises a sheet 16 of conductive material such as copper (a ground plane element) and a layer 18 of non-conductive material.

The non-conductive material should have a permeability-permittivity product which is high and substantially frequency independent, i.e., substantially less than a five per cent change in the range of frequencies from 1 megahertz to 1 gigahertz. In addition, the material should have a low dielectric and magnetic loss over the cited range of frequencies. Such a material is a plastic matrix in which is dispersed a magnetic material. Suitable plastics should be those exhibiting substantially frequency independent dielectric constants and low dielectric loss. The following plastics satisfy these criteria: Polyethylene (which has a dielectric constant of 2.26 over the range under consideration), Polystyrene (which has a dielectric constant of 2.56-2.55 over the range under consideration). A plastic admirably suited for use and constituting a preferred embodiment of the invention is polytetrafluoroethylene. The magnetic material should exhibit a permeability much greater than one in addition to having a permeability-permittivity constant which is substantially independent of frequency over the range under consideration. Such a material can be a ferromagnetic or a ferrimagnetic material. In particular, powdered iron or powdered ferrite is preferred.

Alternatively, the non-conductive material may comprise a linear ferrite material because linear ferrites are found to possess the above-noted characteristic at the frequencies of interest.

Although striplike element 12 has been described as two separate portions it is preferably a laminated structure wherein the layer 18 of non-conductive material is bonded on the sheet 16 of conductive material. The signal conductor 14 is of a conductive material such as copper, silver or aluminum, preferably "printed" on the exposed surface of layer 18. Printing is used in its generic sense to include evaporating, sputtering, photoetching or other techniques well known in the arts of printed circuitry and microelectronic fabrication. This, in the application wherein the layer 18 of non-conductive material comprises a linear ferrite, both surfaces of the slab may be plated or coated with an appropriate conductor. The bottom layer of the conductive coating forms the sheet 16 and the signal conductor 14 is formed from the upper layer, utilizing any of the conventional methods noted. The signal conductor 14 traces out a meandering path and is formed by a plurality of serially connected interdigit elements such as 14A and 14B which are adjacent and substantially parallel. It should be noted that the lengths of the interdigit elements and their spacing controls the coefficient of coupling between the elements and can be used to vary the properties of the delay line.

The delay line 10 also may be fabricated by molding techniques. Thus, the conductor 14 is traced on a conducting plate and removed therefrom. A mold is filled with the dielectric material in powdered form having the magnetic particles dispersed therethrough. Alternatively, the mold may be filled with a powdered ferrite material. The conductor 14 is placed on the dielectric material and the mold is closed. Heat is applied to melt the material. The resulting element is removed from the mold and the bottom surface thereof is coated with a conducting material in any conventional manner as by sputtering techniques or the like. In this respect, it should be noted that it may be desirable to have the dielectric material extend between and about the conductor 14.

The delay line 10 has an input terminal 20 and an output terminal 22. These terminals are connected to the ends of signal conductor 14. Signals applied between input terminal 20 and the grounded sheet 16 travel along the signal conductor 14 and are transmitted as signals across the output terminal 22 and ground.

The transmitted signals will be delayed a period of time related to the mechanical length of the signal conductor 14 and the electromagnetic properties such as the permeability and the permittivity of the region surrounding the signal conductor 14. Thus, it is seen that greater delays per unit length are obtained from the meandering geometry of the signal conductor. In addition, increasing the product of the average permeability and average permittivity of the region surrounding the signal conductor 14 increases the delay per unit length.

Accordingly, another embodiment contemplates placing the striplike element 24 over striplike element 12. Element 24 comprises sheet 26 of conductive material and layer 28 of non-conductive material. Since sheet 26 is the same as sheet 16 and layer 28 is the same as layer 18 they will not be discussed any further. It should be noted that layers 18 and 28 are in opposed relation and sheets 16 and 26 are conductively connected together by a shorting wire 30. Such a configuration, in addition to increasing the delay of the line by surrounding signal conductor 14 with high-permeability and high-dielectric constant material also provides signal shielding by virtue of the ground planes established by sheets 16 and 26.

The embodiment including striplike elements 12 and 24 also may be molded in a manner similar to that described above. For this latter embodiment, both mold halves will be filled with dielectric material and, after removal from the mold, the upper and the lower surfaces of the resulting block of material are coated with an electrically conducting material

It should be noted that by feeding signals between the signal conductor 14 and the ground planes the delay line 10 is an unbalanced line.

As has been stated above the delay per unit length of the delay line is at least a function of the product of the average permeability and average dielectric constant of the region surrounding the signal conductor 14. Therefore, if an air gap having a controllable thickness is introduced between elements 12 and 24 a delay line with a controllable delay is obtainable. Such a delay line 10' is shown in FIG. 2. The delay line 10' is identical in all respects to delay 10 of FIG. 1 except that sheets 16' and 26' are more rigid. In addition, leaf springs 32 of Nylon or the like are interposed between elements 12' and 24' for biasing the elements to separate. A screw C-clamp 34 engages the elements 12' and 24' to move them together under the control of the rotation of screw 36. Although leaf springs and a screw C-clamp have been shown it should be apparent that other well known means are available.

As noted above, the line shown in FIGS. 1 and 2 illustrates an unbalanced line. However, in many applications it may be desirable to provide a balanced delay or transmission line. Accordingly, FIG. 3 illustrates a balanced line which is designated generally by the reference numeral 40. The line 40 includes a length of non-conductive material 42 having the same properties as the layer of material 18. Received on the material 42 are signal conducting means such as signal conductors 44 and 46. The conductors 44 and 46 are identical in construction and include elements similarly to the conductor 14. That is, the conductors 44 and 46 trace out meandering paths and are respectively formed by a plurality of serially connected interdigit elements such as 44A, 46A and 44B, 46B which are in adjacent and substantially parallel relationships. Moreover, the elements of the conductor 44 are spacially displaced from and substantially parallel to corresponding elements of the conductor 46. Connected to one end of the conductors 44 and 46 are respective input leads 48 and 50; connected to the other end of conductors 44 and 46 are respective output leads 52 and 54. As noted above, the line 40 may be constructed by lamination techniques or by molding techniques, similarly to the line 10 disclosed above. Thus, the line 40 provides a means for conducting a balanced signal with respect to an outside reference point such as ground.

In many applications it may be desirable to shield the conductors 44 and 46 from external electric fields or to contain the electric field produced by the signal carried by the conductors. Accordingly, an electrically conducting layer 56 may be provided on the outer surface of the material 42 to effect such shielding.

Moreover, another length of dielectric material (not shown) may be placed over the conductors 44 and 46 to fully enclose the conductors in a dielectric housing. If desired, both the upper and the lower surfaces of this housing may be coated with a conductive layer, or conductive layers may be laminated thereto, to effect shielding of the conductors.

There has thus been shown an improved electrical component which by using a material having a high permeability and high dielectric constant in conjunction with a meandering signal conductor provides an easily fabricated, very efficient and compact signal delay device. In addition, by being able to control the separation between the layers of the material it is possible to vary the signal delay of the line.

Although only a single layered line has been shown, it should be realized that such lines can be stacked to obtain greater delays when used as a delay line. While only a limited number of embodiments of the invention have been shown and described in detail, there will now be obvious that numerous omissions, changes and additions may be made in such embodiments without departing from the spirit and scope of the present invention.

Claims

What is claimed is:

1. An electrical component including a planar single composite section of nonconducting material having a dielectric constant substantially independent of frequency, low dielectric and magnetic loss, a magnetic permeability greater than unity and substantially independent of frequency; an electrical signal conducting means in contact with said material for providing a path for the transmission of an electrical signal, said signal conducting means comprising a first signal conductor adapted to be connected to a first terminal, and a second signal conductor spacially displaced from and electrically cooperable with said first signal conductor and adapted to be connected to a second terminal, said first signal conductor being formed by a plurality of serially connected interdigit elements which are in adjacent and substantially parallel relationship, said second signal conductor lying in the same plane as said first signal conductor and comprising a plurality of serially connected interdigit elements which are in adjacent and substantially parallel relationship, said first and second signal conductors being sized and positioned so that the elements of said first signal conductor are spacially displaced from and parallel to corresponding ones of said elements of said second signal conductor.

2. An electrical component as in claim 1, and an electrically conductive layer of material covering at least a surface of said section of material.

3. An electrical component as in claim 1, wherein said non-conductive material comprises a strip of polytetrafluoroethylene having finely divided particles of magnetic material dispersed therethrough.

4. An electrical component as in claim 1, in which said non-conductive material is composed of a linear ferrite.

5. An electrical component comprising a length of composite material having a permittivity substantially independent of frequency, low dielectric and magnetic loss and a magnetic permeability greater than unity; and signal conducting means for conducting an electrical signal; at least a portion of said signal conducting means extending through said material, said signal conducting means including a first and a second signal conductor each having serially connected interdigit elements which lie in the same plane and are in adjacent and substantially parallel relationship, said elements of said first conductor being spacially displaced from and parallel to corresponding elements of said second conductor.

6. An electrical component as in claim 5, and electrically conductive layers of material on at least two opposed surfaces of said length of material.

7. An electrical component comprising a length of composite material having a permittivity substantially independent of frequency, low dielectric and magnetic loss, and a magnetic permeability greater than unity; and signal conducting means for conducting an electric signal; at least a portion of said signal conducting means extending through said material; said length of material including a first section and a second section; said signal conductor means including a first conductor disposed between said first and second sections, and a second conductor comprising ground plane elements of electrically conductive material on the respective outer surfaces of said first and second sections, and means for controllably varying the spacing between said sections to vary the delay introduced in signals applied to said signal conducting means.

8. An electrical component as in claim 5, in which said length of material is a solid block of material, and said portion of said signal conducting means is embedded therein.