WAVEGUIDE DELAY

Abstract: A waveguide delay comprising an elongated channel formed to give an extended path for a travelling wave characterised by an elongated channel in a first rigid member (1-8-11-15-21 or 25) and closed by a second rigid member (4-5-9-12-17-22 or 27) engaging that face of the first member in which the channel (2-6-7-10-13-16-23 or 25) is formed to form a closing member for the channel.

Description: WAVEGUIDE DELAY This invention relates to improvements in and to a Waveguide Delay and the method of manufacturing same. A low loss signal delay mechanism is a common requirement 5. in a certain class of electronic equipment both military and commercial. In many cases, where some form of waveguide delay would otherwise be appropriate, such is precluded on the ground of cost, weight or the space available, particularly where long delays are called for. 10. Waveguide delay lines are already well known and these may typically consist of metallic tubes which may be of cylindrical, rectangular, single or double ridged cross- section. When used to construct a delay line, normal waveguide 15. poses a problem in forming and packaging, particularly when significant delays are required. An object of the present invention is to provide an improved waveguide delay which can be manufactured in a relatively simple manner with a high degree of accuracy and at low cost relative to the general 20. type of waveguide delay line as used at present. A waveguide delay as described can: (a) be integrated into a system design in such a way that it becomes a load bearing structural component occupying minimum volume; 25. (b) be an extremely low weight/high strength structure; (c) offer low cost of manufacture; (d) the cost penalty for varying design parameters can be low; (e) retain the low insertion loss characteristic of normal 5. waveguide. The waveguide delay the subject of the present invention can conveniently be in the form of a helix with part section formed in a tubular body by machining or the like and completed by a closing member fitting over the channel to 10. close same, or the waveguide channel can be formed in a member by having the channel in spiral form, or alternatively it can take the form of longitudinally extending side by side channels having guide members at each end to divert the signal from one channel back to another channel to flow 15. in an opposite direction, and so on, by means of which aforesaid members a relatively elongated channel can be formed in a small space and of solid form because the channels can conveniently be formed in tubular bodies with closing members fitting to the bodies or formed as a part of the 20. bodies, to complete the rigid and compact structure. Thus the waveguide delay according to this invention can according to one form be defined as comprising an elongated channel formed to give an extended path for a travelling wave, characterised by an elongated channel 25. machined or formed in the first member and closed by a second closing member engaging that face of the first member in which the channel is formed. The two members can be formed so that one can be shrunk onto the other after machining of the channel or otherwise forming it in a rigid member and can take either a helical or spiral form and if desired the channel can be formed 5. of complementary sections in a first member and a second closing member which are then interengaged to form the completed waveguide channel. According to the further form the tubular waveguide delay can comprise an elongated channel formed to give an 10. extended path for a travelling wave characterised by a series of nested channels to fill a selected volume, and end pieces fabricated and connected to the ends of the said nested channels to form a folded waveguide delay line, whereby to achieve high volumetric efficiency, high strength and 15. low weight. The invention relates also to a termination for the helical form of the waveguide delay line. In order, however, that the nature of the invention can be more fully appreciated embodiments thereof will now 20. be described with reference to the accompanying drawings which show examples of such waveguide delays, and in which: FIG. 1 is a perspective view of a cylindrical wave guide delay constructed according to this invention in its simplest form, the wall of the structure being cut away 25. to show how the channels are formed in an inner member and closed by a closing member fitting over the inner member. FIG. 2 is a fragmentary sectional view showing the inner member of the waveguide delay section, shown here as single ridged, with a closing member being assembled 30. over it to complete the waveguide delay section required. FIG. 3 is a fragmentary sectional view showing how the closing member can fit over the outside of a cylindrical member which has the channels formed in it. FIG. 4 is a similar view to FIG. 3 but showing an inner 5. cylindrical member closed by a closing member but with an inverted member fitted over the closing member so that the closing member closes the channels of both members. FIG. 5 is a similar view to FIG. 4 but showing how a pair of members have channels formed in them, the inner 10. member being closed by the next outer member which is in turn closed by the outer closing member. FIG. 6 shows how the channels can be formed in both an inner and an outer member so as to register and form a completed channel which has a junction on an intermediate 15. portion of the completed channel. FIG. 7 is a fragmentary perspective view showing how the channels can be formed by fitting together a pair of pressed members. FIG. 8 is a perspective view of a fragment of a device 20. in which the channels are formed in a plate to be of spiral form shown here as a single ridge single sided arrangement. FIG. 9 is a view similar to FIG. 8 but showing how other profiles such as the double ridge double sided device can be formed. FIG. 10 is a view showing how the channels can extend horizontally with end members of suitable design to guide the signal from one channel to an adjacent channel so that an elongated channel is formed in a relatively compact space. 5. FIG. 11 is a fragment of such an assembly showing in this case the.channels in an outer member which may be shrunk onto an inner member or otherwise firmly fitted to close the open portion of the channels. FIG. 12 is a view of a fragment of such a waveguide 10. delay showing how nested members can be formed with each having part of a channel formed therein in a manner similar to FIG. 7 but in this case with longitudinal instead of helical channels. FIG. 13 is a view showing how the channels can be formed 15. by pressing or similar means in this case showing a pair of members each of single ridged section formed to have longitudinal channels with a division therebetween but it will be realised that the division between the channels could be omitted to form compound channels with a portion 20. in each interengaging member. FIG. 14 is a longitudinal section of a termination here shown for a single ridged configuration for a helical waveguide delay according to the invention, and FIG. 15 is a transverse section of the termination. 25. Where possible similar parts in the embodiments have similar reference numerals. Referring first to FIGS. 1 to 7 inclusive, the invention comprises a tube 1 of any suitable material such as aluminium into which is machined the helical channel 2 which continues along the tube 1 the required 5. distance to provide the necessary length for the particular delay line, and the cross section of the channel can be suited to any particular requirement such as by having a central ridge 3 and the channel is closed by simply fitting another tube which forms 10. a closing member over the tube 1 by heat shrink or other methods to obtain effective contact between the walls of the tube and the wall of the channel closing member 4. Terminations can be fitted at either end to couple energy into and out of the delay line and 15. such a termination will be described with reference to FIGS. 14 and 15. It will be appreciated a high degree of accuracy is obtainable when, for instance, the channel 2 is machined in the surface of a tube 1, and that the 20. dimensions and shape of the channel can be readily selected by appropriate machining methods. It will also be appreciated that multiple channels could be formed in the same tube in side by side helical arrangement. 25. In FIG. 4 is shown how the tube 1 with a channel 2 and closing member 4 can have a second tube 5 fitted within it and shrunk fitted on to the now closing member to form a second channel 6. FIG. 5 shows a rearrangement of the assembly shown in FIG. 4 to have the one member close the channels of the other and itself having the channels closed by a closing member, the components being 5. referenced similar to FIG. 4. In FIG. 6 is shown how a channel 7 can be formed between two tubes 8 and 9 each having part of the channel 7 formed in it by machining or other forming methods, one of the part channels thus acting as 10. a closing member for the part channel of the other member. Grinding or any other treatment of the channel 2 or 6 or 7 can effectively be carried out because of the nature of its construction and formation and such a channel also has very high mechanical rigidity 15. which is inherent in tubular structures and as the channel is formed in .a unitary manner supporting of such a channel is also facilitated because of the inherent rigidity of a tubular structure. FIG. 7 shows a similar assembly to FIG. 6 but 20. with the two tubes formed by pressing or moulding reference numerals similar to FIG. 6 being used. The channels could be formed in flat sheets then curved to tubular form or pressed into thin tubes. FIG. 8 shows how a channel 10 can be of spiral 25. form formed in a flat plate 11, closed by a further flat plate 12 which acts as the closing member, but it will be realised that in this form part channels may be formed in both sides of a central member and closed by top and bottom members which may also carry 5. part channels to complete any waveguide section required. Such a form is shown in FIG. 9 where as well as the channel 10, a channel 13 is formed in the opposite face of the plate 11 and a second closing member 14 is used. 10. In the case of a spiral configuration the channel can be formed by machining such a configuration into a flat plate and to bond to the top of the channel a further flat plate to form the waveguide delay and while machining is the preferred form of construction 15. it can be formed by pressing or molding. In the form shown in FIGS. 10 to 13 inclusive, instead of using a helical or spiral configuration it consists of a particular arrangement of straight waveguide delay sections of the required profile 20. which are pressed, cut or otherwise formed as longitudinal adjacent channels which are disposed to efficiently fill a given volume, end pieces being used which are so fabricated and so connected to the straight sections as to form a multiple folded 25. waveguide delay line offering high volumetric efficiency, high strength and low weight. In the form of this concept shown in FIG. 10 in which the tube, closing member and channels are designated 1, 4 and 2 respectively as in FIG. 1, part profile of a desired folded waveguide delay 5. section is fabricated from a tube 15 to form longi¬ tudinal channels 16 in the wall of the tube 15, a closing member 17 being used to close the channels 16 to give the profile of the desired waveguide delay, assembled to the tube 15 and closing member 17 may be by a heat shrink or 10. other process. The ends of the structure so formed have fabricated end pieces 18 having curved channels 19 to form a continuous or a continuous folded waveguide delay ' line. The curved end channels 19 direct the signal 15. from each channel 16 in the tube 15 to another channel 16 in any required order. The channels 16 can be formed from the outer face of the tube ' 15 as shown in FIG. 10 or from the inner face as shown in FIG. 11 where similar references are used. 20. The end members 18 having the curved channels 19 formed in them can butt against the ends of the tube 15 and held in place by the closing member 17 which when in the form of a tube can be shrunk fitted to both the tube 15 and the end members 18. 25. Instead of forming part of the channel in the wall of the tube 15, parts of such channels can be formed in adjacent tubes as illustrated in FIG. 12 where an inner tube 21 is disposed in an outer tube 22 with the channels 23 of one opening to the channels 24 of the other. In the form shown in FIG. 13, a similar form 5. to that shown in FIG. 4 is used but the channels 25 and 26 are formed by pressing or moulding the tubular members 27 and 28 and fitting them over a closing member 29. Instead of the channels extending longitudinally 10. on the cylinder they can be of curved formation to be part helical, but still provided with end members to interconnect adjacent channels for signal trans¬ mission from the one channel to the adjacent channel. While the preferred form is cylindrical as 15. shown, this can -be flat form with the channels formed side by side and extending longitudinally, end curved channels closing the longitudinal channels and directing the signal leaving one channel into the adjacent channel . 20. Referring to FIG. 10 it will be realised that the tube 15 and end members 18 can be formed of one tube with the channels formed by routing to give a unitary structure. A waveguide delay as described can be fed in various way ' s but in the helical form as shown particularly in FIGS. 1 to 3 inclusive one end of the channel has the termination shown in FIGS. 14 5. and 15 attached to it and is so arranged that it can share part of the wall of the end of the helical waveguide delay to which the signal is fed and allowing the system to be arranged in a symmetrical manner by maintaining the integrity of tight internal 10. tolerances. In this manner the termination has minimal intrusion into the cylindrical centre cavity of the delay line which may be required for mounting associated componentry. The termination is open on one side and a shared 15. wall of the helix is used to complete its profile. The geometry of the termination is such that a smooth transition profile is provided together with adequate sealing and mounting flanges. As shown in the drawings the tubular member 20. 1 has the helical channel 2 formed in it which may 'be of required shape. 35 represents the end wall of the first channel of the convolution. The termination 36 has inner and outer walls 37 and 38 respectively and one complete end wall 25. 39 but the opposite end wall 40 is positioned to be in the same plane as the end wall 35 but is arranged to fit tightly to it so that the end wall 35 of the channel 34 together with the end wall 40 of the termination 36 complete the structure 30. and provide a matching feed for the channel . The termination 36 can be fed in any required manner such as by a co-axial line through the aperture 41 in a connecting boss 42. Alternatively, the boss 41 could be replaced with a co-axial 5. connector, the centre pin of which passes through a circular aperture in the lower ridge 45 to connect with the upper ridge 44 via the gap 43. From the foregoing description, it will be realised that the configurations of a waveguide 10. delay outlined above afford good volumentric efficiency through shared walls, high structural strength and low weight, and while machining from a solid form may be an appropriate method achieving high accuracy and good strength requirements, the 15. formation can be by forming of sheet metal or non- metallic material rendered conducting, which can be moulded or have the necessary channels pressed or otherwise formed in it and in which again the channels can be full- depth in the one member to 20. be closed by another member, or they can be formed by the two co-operating members each containing part of the channel so that when the members are assembled together the complete channel is formed. The basic concept allows, in the helical ' 25. configuration for example, that a tube (typically aluminium) can have formed upon its surface a helical waveguide profile the dimensions of which reflect the frequency/bandwidth characteristic required. As said a further tube can then be fitted to the profiled 30. tube by a heat shrink or other process to complete the waveguide delay configuration. When such a profile is formed, for example, on a numerically controlled machine any desired variation in the frequency/bandwidth characteristic of the delay would require only a simple change 5. to the controlling instruction set - a feature of value where small production runs are required of devices with different delay characteristics (e.g. set of laboratory waveguide delays). The high load bearing characteristics of a 10. tube permit the use of very thin wall sections in the helical configurations (typically .5mm). In. many applications the helical waveguide delay could serve as a structural member, heat-sink, component carrier and electromagnetic shield. 15. Should a split delay be required or where a second delay calls for a different frequency/ bandwidth profile two helical profiles could be formed side by side or an additonal tube formed to the required profile could be assembled contiguous 20. with the first helical delay structure by a heat shrink or other process, thus affording space/cost and weight saving through shared walls. In any of the above described waveguide delay assemblies the channels can be of any required 25. cross-sectional shape such as double ridged, circular, single ridged or rectangular, formed in one member and closed by another or formed in inter- fitting members each having part of the channel formed therein.

Claims: . THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A waveguide delay comprising an elongated channel formed to give an extended path for a travelling wave characterised by an elongated channel in a first rigid member (1-8-11-15-21 or 25) and closed by a second rigid 5. member (4-5-9-12-17-22 or 27) engaging that face of the said first member in which the channel (2-6-7-10-13-16-23 or 25) is formed to form a closing member for the said channel. 2. A waveguide delay according to claim 1 characteris in that one said member (1) is tubular and the other said member (4) is also tubular and is shrunk on to the other said member to seal the channel. 3. A waveguide delay according to claim 1 or 2 characterised in that the channel (2) is formed as a helix extending around the said first member (1) which is cylindr and is closed by a closing member (4)' which is also cylindr 5. and fits against the first said member to form a closed channel. 4. A waveguide delay according to claim 3 characteris in that the first member (1) has.the helical channel (2) formed in its outer surface, and the closing member (4) fits neatly over the first said member (1) to close said 5. helical channel (2). 5. A waveguide delay according to claim 3 characteris in that the first member (1) has the helical channel (2) formed in its inner surface, and the closing member (4) fits neatly against the inner wall of the first said member 5. to close the said channel (2). ' 6. A waveguide delay according to claim 3 characterised by a plurality of channels (10-13) formed in the said first member (15) each said channel being closed by a closing member (12-13) engaging that face in which a channel 5. is formed. 7. A waveguide delay according to claim 3 characterised by a plurality of said first members with the channels of one closed by the other said member. 8. A waveguide delay according to claim 1 or 2 characterised in that a channel (10) is formed as a spiral in a first member (11) and is closed by a second closing member (12) engaging the face of the first member (11) 5. in which the spiral is formed. 9. A waveguide delay according to claim 1 characterised by multiple waveguide delay channels (2) in an interengaging assembly using at least a first member (1) and a second inter-fitting member (5) with a closing member (4) therebetwee 5. to form a compound waveguide delay with the channnels (2 and 6) closed by the common closing member (4). 10. A waveguide delay according to claim 1 characterised in that a first member (8) and a second member (9) interertgage to form between them at least one machined extended waveguide delay channel (7). 11. A waveguide delay according to claim 1 characterised in that the said first rigid member (1) is a plate (11) having the channel (10) formed therein and closed by a second rigid member (12) in the form of 5. a plate engaging the said first member (11) to close the said channel (10) . 12. A tubular waveguide delay according to claim 1 characterised by a series of nested channels (16) formed in a first rigid member (15) arranged to fill a selected volume, and having curved end channels (19) arranged to 5. connect to the ends of the said channels (16) to form a folded waveguide delay line, and a closing member (17) to close the said channels. 13. A tubular waveguide delay according to claim 12 wherein the nested channels (16) are open and formed in a cylindrical member (15) and the channels (19) are formed in end members (18) and the channels (16) and the 5. channels (19) in the end members are closed by second cylindrical closing member (17) fitting neatly to the first cylinder and the end members (18) and shrunk fitted thereon. 14. A tubular waveguide delay according to claim 12 characterised in that the channels (16-19) open inwards in a cylindrical member (15-18) and are closed by a cylindrical closing member (21) fitting against the inner face of the 5. cylindrical member (15-18). 15. A tubular waveguide delay according to claim 12 wherein the nested channels (23) are open and formed in the wall of a first cylindrical member (21) and the channels (23) are closed by a second cylindrical member 5. (22) having open channels (24) mating with the open channels (23) of the first cylindrical members (21). 16. A tubular waveguide delay according to claim 15 wherein one of the said cylindrical members (22) is heat shrunk to the other said cylindrical member. 17. A tubular waveguide delay according to claim 13 wherein waveguide channels (25-26) are formed in the . walls of two hollow generally cylindrical sheet metal members (27-28), one said cylindrical member (27) being 5. assembled around the other said cylindrical member (28) with open channels (25-26) in each facing the adjacent cylindrical member. 18. A tubular waveguide delay according to claim 17 wherein the channels (25-26) are closed by a cylindrical closing member (29) interposed between the first said two cylindrical members (27-28), said cylindrical members 5. (27-28) being joined to a closing member (29) to form a rigid structure. 19. A waveguide delay according to claim 3 characterised by a termination for a helical waveguide delay which engages the end of the first said member (1) at the end of the said helical channel (2) and includes 5. a channel (46) which shows the end wall (35) of the channel (2) on the said first member (1).

Inventors: DADSWELL PETER JOHN, DADSWELL, PETER, JOHN
Applicants: COMMW OF AUSTRALIA, THE COMMONWEALTH OF AUSTRALIA, CARE OF THE SECRETA
Application year: 1985
Main classification: H01P9
IPC codes: H01P3, H01P9