US3553409A

US3553409A - Circuit frame

Info

Publication number: US3553409A
Application number: US767730A
Authority: US
Inventors: Sanford S Lehrfeld
Original assignee: TEK WAVE Inc
Current assignee: TEK WAVE Inc
Priority date: 1968-10-15
Filing date: 1968-10-15
Publication date: 1971-01-05
Anticipated expiration: 1988-01-05

Abstract

A circuit frame comprised of a one-piece metallic frame member having launchers secured thereto in a precise manner and provided with top and bottom covers for sealing the interior opening. At least one of the covers is provided with a mounting surface for supporting a microstrip circuit which makes an electrical interface with the launchers secured to the frame to provide for a plurality of coaxial-to-microstrip transitions. The top and bottom covers may be either soldered or mechanically fastened to the frame member to protect the coaxial-to-microstrip electrical interface against dirt, dust, or other external influences. Precision alignment of the launcher assemblies provides a circuit frame apparatus having highly reliable operating characteristics.

Description

I United States Patent 1 13,5s3,409

[72] Inventor SanfordS.Lehrfeld 3,339,158 8/1967 Passaro 333/].1 HeightstowmNJ. 3,359,510 12/1967 Geiszler 333/l.1 32 12 Primary Examiner-H. 0. Jones Paemed Jan. 5, 1971 Attorney Ostrolenk, Faber, Gerb&Soffen [73] Assignee Tek-Wave,lnc. Princeton,N.J. a corporation of New Jersey [54] CIRCUIT FRAME 6 Claims, 5 Drawing Figs.

[52] U.S. Cl 200/168, 333/84 [51] Int. Cl. H0lh 9/04, HOlp 3/08 [50] Field of Search 200/ 1686, 153.18;333/84, 84M, 1.1; 333/21, 97

[56] References Cited UNITED STATES PATENTS 3,063,024 11/1962 Davis, Jr 333/84(M)UX ABSTRACT: A circuit frame comprised of a one-piece metallic frame member having launchers secured thereto in a precise manner and provided with top and bottom covers for sealing the interior opening. At least one of the covers is provided with a mounting surface for supporting a microstrip circuit which makes an electrical interface with the launchers secured to the frame to provide for a plurality of coaxial-tomicrostrip transitions. The top and bottom covers may be either soldered or mechanically fastened to the frame member to protect the coaxial-to-microstrip electrical interface against dirt, dust, or other external influences. Precision alignment of the launcher assemblies provides a circuit frame apparatus having highly reliable operating characteristics.

. CIRCUIT FRAME The present invention relates to'a microwave circuits, and

l more particularly to a novel circuit frame for use in microwave circuit applications which necessitates a plurality of highly reliable coaxial-to-microstrip transitions.

There exist a number of applications in the microwave field wherein it is both desirable and necessary to connect a coaxial transmission line to a microstrip circuit which is an essentially flat-strip transmission, capable of superior operation at microwave frequencies. Two of the major problems which are experienced in forming such electrical .interfaces are the provision of good impedance matching at such transitions and accurate alignment of the components forming the electrical interfaces, and especially in those applications where a plurality of such coaxial-to-microstrip transitions must be provided.

The present invention is characterized by providing a novel circuit frame having secured thereto in a highly precise manner a plurality of launchers for electrically coupling coaxial lines to a microstrip circuit. The central opening of the frame is sealed by top and bottom covers which are securely fastened thereto by any suitable means. At least one of the covers is provided with a mounting surface for receiving the microstrip circuit whoseconductive surfaces are accurately aligned and firmly electrically engaged with the tabs of the launchers once the cover member supporting the microstrip circuit is securely fastened to the frame. In addition to providing a good electrical interface between the coaxial launchers and the microstrip circuitry, the top and bottom covers keep the interior region enclosing the electrical interfaces free from dust and dirt" and being further designed to provide a critical air space relationship between the interior surfaces of the top cover and the substrate to reduce the overall height of the frame assembly to a minimum while providing sufficient spacing of the bottom cover surface above the substrate surface so that the normal operation is unaffected. The one-piece frame member provides for high precision alignment of the launching assemblies, which alignment may be assured prior to and in the absence of coupling the microstrip circuitry thereto.

It is therefore one object of the instant invention to provide a novel frame for use in microwave circuit applications wherein a plurality of coaxial-to microstrip transitions are required.

Another object of the present invention is to provide a novel circuit frame for use in microwave circuit applications wherein the circuit frame is comprised of a one-piece frame member having a plurality of launching assemblies secured in a highly precise manner to provide for aplurality of coaxialto-microstrip transitions within the circuit frame opening.

Yet another object of the present invention is to provide a novel circuit frame for use in microwave circuit applications wherein the circuit frame is comprised of a one-piece frame member having a plurality of launching assemblies secured thereto in a highly precise manner to provide for a plurality of coaxial-to-microstrip transitions within the circuit frame opening and which is further comprised of top and bottom covers, at least one of which is provided-with'a surface for supporting the microstrip circuitry, which covers effectively act to keep the interior region surrounding the electrical interfaces free from dirt, dust and other-external influences.

These as well as other objects will become apparent when reading the accompanying description and drawings in which:

FIG. I is a perspective view showing the circuit frame of the present invention and one cover thereof in the removed position to expose the structural details.

FIG. 2 is a top plan view of the circuit frame of F IG 1.

FIG. 3 is an elevational view showing the circuit frame of FIGS. 1 and 2 wherein the circuit frame covers are shown in assembled fashion as well as being separated from the frame body. v

FIGS. 4a and 4b are top plan views of alternative embodiments of the circuit frame of F I68. 1 through 3.

The circuit frame of the present-invention is shown best in FIGS. 1 through 3, and is comprised of a rigid one-piece metallic frame 11 which is machined or otherwise formed to have a rectangular-shaped opening 11a provided with a series of arcuate-shaped cutouts through 12d at each of its interior comers to facilitate receipt of a top cover member and a bottom cover member, to be more fully described, and to permit ease of fit of these members within the frame opening. The frameis further provided with a plurality of openings 13a through for receipt and accurate alignment of a plurality of launcher assemblies 14 through 16, respectively. Each of the launchers is threaded along an exposed portion thereof for threadedly engaging a mating coupling (not shown) of a coaxial cable to provide for electrical connection between a coaxial cable and a microstrip circuit, to be more fully described. Each of the launchers is provided with a metallic tab through 16a, respectively, which projects inwardly beyond the interior of the frame opening 11a for making physical contact and electrical engagement with an associated conductive surface provided on the microstrip circuit. The interior exposed portion of each of the tabs 140 through may be substantially flat, as is shown best in H05. 2- and 3, or a portion thereof may be tapered in the manznerdescribed in detail in copending application Ser. No. 709,264 entitled Chip Launcher, filed Feb. 29, 1968 and assigned to the assignee of the present invention A detailed description of the launcher assemblies will be omitted herein for purposes of simplicity. The detailed description of launcher assemblies set forth in the above-mentioned copending application should be referred to for a thorough understanding of the launcher assembly, and such description is incorporated herein by reference thereto. It is sufficient, for purposes of the present invention, to understand that the launcher employed in the circuit frame of the present invention acts as the electrical interface between a coaxial cable and a microstrip circuit while providing a highly accurate dielectric constant coaxial-tomicrostrip transition, ensuring complete reliability of operation and further providing improved impedance match, flat frequency response and a high accuracy, low VSWR.

The metallic frame 11 is preferably formed of either goldplated brass or aluminum, and is designed to accommodate high-tolerance microwave quality circuits.

The frame opening 11a is sealed by a top cover 20 preferably formed of the same material as the frame 11. the top cover 20 has a rectangular shape: and its outer dimensions are substantially equal to the outer dimensions of the periphery of frame member 11. The top cover is preferably a one-piece member and is machinedl or otherwise formed to provide a continuous marginal portion 20a for physically engaging the top surface 111) of frame 11. The remainder 21 of the bottom surface is fitted within the rectangular-shaped opening 11a of the frame member 11..

A similarly formed bottom cover 17 is provided with a like marginal portion whose dimensions are such as to cause the remaining interior surface 18 of cover 17 to substantially closely fit and project into the bottom of opening 11a, while surface 17a makes physical engagement with the bottom surface llc of frame 11. Bottom cover 17 is also preferably a one-piece member. The covers 17 and 20 are preferably formed of the same material as frame member 11. A microstrip circuit 19 is mounted directly upon portion 18 of bottom cover 17. Either solder, an epoxy, or any other appropriate means may be employed to firmly mount the microstrip circuit board 19 upon the surface of bottom cover portion 18.

Once the microstrip circuit 19 is mounted upon portion 18 of bottom cover 17, the top and bottom covers may be joined to frame 11 by aligning the covers in the positions shown in FIG. 3 and moving the covers in the directions shown by

arrows

22a and 22, respectively, until they occupy the positions 20' and 17', respectively. Considering the bottom cover member 17, it can be seen that when the bottom cover is assembled in the manner shown in FIGS. 1 and 3, the

microstrip conductors

23, 24 and 25 provided on the surface of microstrip circuit 19 make electrical contact with the tabs 14a through 16a, respectively, establishing an electrical circuit therebetween. The distance D between the bottom surface of frame 11 and the top surface of microstrip circuit 19 is selected so as to cause the tabs 14a through 16a to make firm physical contact (and hence good electrical engagement) with the conductors formed upon the surface of microcircuit 19.

Since square corners are difficult to machine, the corners of the frame v11 are provided with the arcuate shaped cutouts l2al2 (having either the configuration of FIG. 1 or FIG. 2) to facilitate insertion of both the top and bottom covers and 17 respectively as well as substrate 19. The cutouts also eliminate the need for further machining of square shaped substrates which machining (i.e. rounding-off" of the corners of substrate 19) would otherwise be necessitated in conventional devices. Both top and bottom covers 20 and 17, respectively, may be firmly secured to frame 11 through the use of suitable fastening means (not shown) which pass through suitable openings 20b20b and 17b -17b provided in the top and bottom covers in order to threadedly engage suitable openings llc-I Ic provided in frame 11.

bottom covers may be provided with beveled portions at 20c and 176, for example, to provide a good press-fitting between the covers and the frame member 11.

The launcher assemblies may be press-fitted into their associated openings in frame member 11,0r, if desired, they may be soldered to the frame.

Mounting the covers 17 and 20 to frame 11 by either threaded fastening means or by soldering effectively acts to prevent both dust and air from entering into the interior region defined by frame opening 110 and covers 17 and 20.

Providing a solid one-piece frame member 11 greatly facilitates alignment of the launcher assemblies 14 through 16 relative to one another. Testing for alignment of the launchers 14 through 16 may be carried out independently of and in the absence of the microcircuit 19. In a like manner, testing of the microcircuit may be performed independently of the circuit frame.

The circuit frame of the present invention may be employed to optimum advantage through the use of microwave chips or microwave printed circuits which are essentially flat-strip transmission lines, capable of superior operation of microwave frequencies. The circuits and components are mounted upon the substrate using microstrip techniques upon a substrate preferably formed of alumina having a dielectric constant in the range from 9.0 to 10.0. This approach results in smaller overall size due to the high dielectric constant of the alumina ceramic and the reduction of the ground plane spacing. An additional advantage is gained in that the characteristics of the chips is their ability to operate at high temperatures. The further ability to incorporate additional components, devices and functions in a true integrated circuit leads to major advantages in size reduction and improvements in overall system performance yielding optimum minimization in size of the total package. The microcircuit and microminiature components may be applied in the printed circuit employing either thin or thick film techniques for applications up to and including the X band. Whereas FIGS. 1 through 3 show an arrangement wherein three coaxial-to-microstrip transitions are provided, it should be understood that a greater or lesser number of such transitions may be provided along any two or more of the sides of frame 11. For example, FIG. 4a shows a frame member 11 provided with a total of six launcher assemblies 40 through 45 wherein at least one launcher assembly is provided along each side of frame member 11. The configuration of the frame, while rectangular, can nevertheless be seen to differ somewhat in its lengthwise and widthwise dimensions relative to the embodiment of FIGS. 1 through 3. Top and bottom covers of a similar configuration would obviously be provided for the frame configuration of FIG. 4a. FIG. 4b shows a frame member 11 substantially similar in its outer pair of launcher assemblies are provided on each of three sides of frame member 11. From a consideration of the three em bodiments shown in FIGS. 3, and 4b,*for example, it can'- clearly be seen that any number of coaxial-to-microstrip transitions may be provided, depending only upon theneeds of the user. t

In the case where lumped parameter components are to be added to the microstrip circuit, it is-preferred'that these components be added to the microstrip circuit subsequent to the mounting of the circuit 19 (for example) to bottom cover portion 18. The advantage of this technique resides in the fact that the metallic bottom cover advantageously dissipates the heat generated during the operation in which such components (for example, chip capacitors, chip diodesandflso forth) are soldered to the microstrip circuit surface.

The top cover 20 serves the dual function of being an effective dust cover as well as providing an air space between'the'" bottom surface of top cover 20 and the top surface of microstrip circuit 19 such that the distance E therebetween (see FIG;

3) is sufficient to permit normal operation of the circuit and: further is of a minimum height so as to thereby reduce'the overall height of the frame assembly to a minimum amount.

Testing of the circuit is also greatly simplified by the present design. If faulty operation is detected, testing of-the circuit on bottom cover 18 may be carried out simply by removing the bottom cover 18 from the frame assembly l0. This may be performed without dismantling the launcher or any other components of the peripheral circuitrycoupled to the frame assembly. The circuit may then be rapidlyand easily tested in order to isolate the faulty operation. Obviously, another circuit module (Le/bottom cover 18 andisubstrate 19) may be substituted for the removed module to-further reduce handling and down time to a minimum.

It can be seen from the foregoing that the present inventionv provides a novel circuit frame for multiple coaxial-to-micros' trip transitions between coaxial cable members and microstrip circuitry wherein high precision alignment of the launchers' and circuitry is attained wherein the circuitry and the frame members and launchers may be independently tested for high accuracy alignment and wherein the frame assembly positively seals the electrical interface between the launcher and the microcircuit to protect it against dirt, air and other external influences.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein, but only by the appended claims.

I claim:

1. An assembly for accurately aligning and electrically coupling a plurality of microwave coaxial cables to microwave printed circuits of the microstrip-type being comprised of:

a one-piece circuit frame having a substantially rectangular configuration, a central opening provided in said circuit frame;

a plurality of launching assemblies'adapted for connection I to coaxial cables, each positioned within a suitable opening provided in the sides of said circuit frame so that at least two sides of said circuit frame each support a launching assembly;

each of said launching assemblies being provided with coupling means projecting outwardly from said circuit frame for electrically coupling to a mating coaxial cable, and tabs each projecting inwardly beyond the interior periphery of the central opening of said circuit frame for electrical connection to a microcircuit;

at least one cover provided to seal one of the surfaces of said circuit frame defining said central opening, said cover having a substantially flat surface suitable for supporting and mounting a microcircuitf means rigidly fastening said cover to said circuit frame;

a microwave printed circuit of the rnicrostrip-type having its bottom surface secured to said supporting surface of said cover;

said cover supporting surface projecting into said central opening a distance sufficient to cause the exposed marginal surface of said microwave printed circuit to make firm engagement with the confronting surfaces of said launching assembly tabs.

2. The assembly of claim 1 further comprising a second cover member for sealing the opposite surface of said circuit frame containing said central opening;

means firmly fastening said second cover to said circuit frame;

said first and second covers cooperating to seal the central opening of said circuit frameto keep the interior region thereof free from dirt, dust and other external influences.

3. The assembly of claim 2 wherein said second cover is provided with an exposed surface projecting inwardly into the central opening of said circuit frame wherein the distance between the exposed surface of said microwave printed circuit and said second cover is sufficient to permit normal operation of the printed circuit while being minimized to reduce the overall height of the assembly.

4. The assembly of claim 1 wherein said circuit frame is a one-piece member formed of a conductive material, said central opening having a substantially rectangular configuration;

the inside comers of said central opening being removed to form arcuate-shaped slots which extend into the interior surface of the central opening to a depth greater than the removed inside corners;

said microwave circuit having a substantially rectangularshaped periphery;

said arcuate-shaped slots being adapted to facilitate insertionand removal of said microwave printed circuit from said circuit frame.

5. The assembly of claim 2 wherein said first and second covers are provided with openings adjacent their periphery;

said circuit frame provided with tapped apertures on opposite sides thereof for alignment with the openings in said first and second c'overs, respectively; threaded fastening means positioned through the openings in said first and second covers and threadedly engaging the tapped apertures of said circuit frame to releasably secure said covers to said circuit frame. 6. The assembly of claim 2 further comprising means hermetically sealing said first and second covers to said circuit frame.

Claims

1. An assembly for accurately aligning and electrically coupling a plurality of microwave coaxial cables to microwave printed circuits of the microstrip-type being comprised of: a one-piece circuit frame having a substantially rectangular configuration, a central opening provided in said circuit frame; a plurality of launching assemblies adapted for connection to coaxial cables, each positioned within a suitable opening provided in the sides of said circuit frame so that at least two sides of said circuit frame each support a launching assembly; each of said launching assemblies being provided with coupling means projecting outwardly from said circuit frame for electrically coupling to a mating coaxial cable, and tabs each projecting inwardly beyond the interior periphery of the central opening of said circuit frame for electrical connection to a microcircuit; at least one cover provided to seal one of the surfaces of said circuit frame defining said central opening, said cover having a substantially flat surface suitable for supporting and mounting a microcircuit; means rigidly fastening said cover to said circuit frame; a microwave printed circuit of the microstrip-type having its bottom surface secured to said supporting surface of said cover; said cover supporting surface projecting into said central opening a distance sufficient to cause the exposed marginal surface of said microwave printed circuit to make firm engagement with the confronting surfaces of said launching assembly tabs.

2. The assembly of claim 1 further comprising a second cover member for sealing the opposite surface of said circuit frame containing said central opening; means firmly fastening said second cover to said circuit frame; said first and second covers cooperating to seal the central opening of said circuit frame to keep the interior region thereof free from dirt, dust and other external influences.

3. The assembly of claim 2 wherein said second cover is provided with an exposed surface projecting inwardly into the central opening of said circuit frame wherein the distance between the exposed surface of said microwave printed circuit and said second cover is sufficient to permit normal operation of the printed circuit while being minimized to reduce the overall height of the assembly. 4. The assembly of claim 1 wherein said circuit frame is a one-piece member formed of a conductive material, said central opening having a substantially rectangular configuration; the inside corners of said central openiNg being removed to form arcuate-shaped slots which extend into the interior surface of the central opening to a depth greater than the removed inside corners; said microwave circuit having a substantially rectangular-shaped periphery; said arcuate-shaped slots being adapted to facilitate insertion and removal of said microwave printed circuit from said circuit frame.

5. The assembly of claim 2 wherein said first and second covers are provided with openings adjacent their periphery; said circuit frame provided with tapped apertures on opposite sides thereof for alignment with the openings in said first and second covers, respectively; threaded fastening means positioned through the openings in said first and second covers and threadedly engaging the tapped apertures of said circuit frame to releasably secure said covers to said circuit frame.

6. The assembly of claim 2 further comprising means hermetically sealing said first and second covers to said circuit frame.