Abstract:
A compact arrangement having concentric loading element and coupling element with the latter forming a bearing support for a revolvable member mounting the former.

Description:
BACKGROUND 
     It has long been an object of the prior art to obtain a match for impedance of an RF source to that of a line or antenna. See U.S. Pat. No. 2,855,599 as a teaching of a way to arrive at this object and for the reasons such is desirable. 
     However, while this has been a long standing object, no one is known prior to this invention to have found a practical, inexpensive and compact means of packaging such elements to permit universal economical utilization. It is therefore the principal object of this invention to obtain a compact concentric operative relationship of loading coil and coupling coil for impedance matching of an RF source to a line or antenna. 
    
    
     DRAWING DESCRIPTION 
     FIG. 1 is a simple schematic design of an impedance matching circuit according to this invention; 
     FIG. 2 is a plan view with some elements partially shown in cross-section for clarity of element relationships of a package concept for the circuit of FIG. 1 in accordance with this invention; and 
     FIG. 3 is an end view along lines 3--3 of FIG. 2. 
    
    
     DETAILED DESCRIPTION 
     With more particular reference to FIG. 1 there is shown a loading coil 10 operatively related to a coupling coil 12 such that varying the resolution ratio of coils 10 and 12 may be scheduled by a commutator 14 between the line and ground terminals 16 and line 18 respectively. With such circuits a pair of terminals 20, 22 connect a signal source or receiver to the coupling coil. 
     Such structure makes it possible to find a specific match for the transmission line and load. Specific utility is found for this invention in impedance matching an antenna and/or a transmission line to an RF source. 
     Turning now to FIG. 2 there the structure is shown by which this invention may be realized. Specifically, the loading coil 10 is mounted about an insulator 24. A shaft 26 is connected to the insulator 24 to rotate same. As seen, the shaft is supported by a bearing block 28 in an end piece and held thereto by a retaining ring 30. Shaft 26 is connected to a ground source as by a sliding contact (not shown) or any other well known means available to one skilled in the art. This could even be by an end frame where one does not, as here, use an end frame 32 to also support commutating wheel shaft 34. 
     Shaft 34 as shown has an antenna terminal 16 on one end and supports a commutating wheel 38 such that it may move axially in providing a variable length circuit connection of terminal 16 to loading coil 10. Loading coil 10 has one end 40 connected to shaft 26 to ground. 
     Actually shaft 34, as may be best seen by FIG. 3 is supported by spring plates 36 so that wheel 38 has a forced contact with coils of loading coil 10. This will then present side loads on insulator 24, which if no other support is used, would have to be accepted and absorbed by the bearing block 28 supporting shaft 26. However, by appropriate sizing of coupling coil 12 diameter the hollow insulator will have a spaced support between bearing block 28 and the individual coils A, B, C, D and E of coupling coil 12. This allows one to use a spring bias for wheel 38 that will insure a scrubbing contact of wheel 38 and coils F, G, H, J, K, L, M and N of load coil 10. Therefore any tendency to lessen the electrical continuity is prevented. 
     The transmission line or RF source terminals are brought through end-frame 46 as at 48 and 50. 
     OPERATION 
     Using the familiar expression for the resolution ratio: ##EQU1## where N 1  equals the turns of coil 10, 
     N 2  equals the turns of coil 12, and 
     Rl equals the load across 16 and 18. 
     It may thus be realized with the structure of this invention and with the couple of coils 10 and 12 being an air coil, that it is possible in high frequency devices to obtain continuous variance and an infinite number of impedance resolution ratios from less than one to, with the use of an 8 to 4 ratio shown, two, and any fractional ratio between 0 and 2. 
     It may also be realized that the air core could be replaced with a ferrite or like material core for similar operation with low frequency devices.