Wave transmission lines and networks – Plural channel systems – Having branched circuits
Patent
1998-02-12
2000-01-25
Gensler, Paul
Wave transmission lines and networks
Plural channel systems
Having branched circuits
333174, 333175, 333261, H01P 518, H01P 106, H01P 120
Patent
active
060182792
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a radio frequency (RF) coudler and the invention relates particularly, though not exclusively, to an RF coupler for transferring RF power between a first circuit on a rotary shaft and a second circuit relative to which the shaft can rotate.
The invention also relates to a tunable notch filter.
International patent application no. PCT/GB91/00328 discloses an apparatus for measuring dynamic torque in a rotatable shaft. The apparatus comprises a surface acoustic wave (SAW) transducer mounted on the shaft, and requires coupling means for the efficient transfer of RF power between the transducer and processing circuitry which does not rotate with the shaft.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a radio frequency (RF) coupler for transferring RF power between a first circuit on a rotary shaft and a second circuit relative to which the shaft can rotate, the RF coupler comprising a first RF transmission line arranged to rotate with said rotary shaft and for connection to said first circuit, and a second RF transmission line for connection to said second circuit, wherein said first RF transmission line comprises a first, electrically conductive track having at least one termination, said second RF transmission line comprises a second, electrically conductive track having at least one termination, said first and second tracks are arranged coaxially around the rotation axis of the rotary shaft, said first track can rotate relative to said second track and said first and second tracks are arranged in substantial, mutually overlapping relationship to provide coupling between the first and second RF transmission lines.
According to another aspect of the invention there is provided a radio frequency (RF) coupler comprising a first RF transmission line mounted on a rotary shaft for rotation therewith and a second RF transmission line relative to which the first RF transmission line can rotate, wherein the first RF transmission line comprises a first electrically conductive track having at least one termination, said second RF transmission line comprises a second electrically conductive track having at least one termination, said first and second tracks are arranged coaxially around the rotation axis of the rotary shaft, said first track can rotate relative to said second track, said first and second tracks are in substantial overlapping relationship, each said track has a periodic undulation around the rotation axis, the undulation being formed by an integer number n of segments each subtending an angle ##EQU1## at the rotation axis, and said at least one termination in the track is formed in one of the segments thereof.
According to a yet further aspect of the invention there is provided a notch filter tunable to a desired frequency within a predetermined RF frequency band, the notch filter comprising a first RF transmission line and a second RF transmission line, wherein said first RF transmission line comprises a first, electrically conductive track having at least one termination, said second RF transmission line comprises a second, electrically conductive track having at least one termination, said first and second tracks are arranged coaxially around a rotation axis and are in substantial overlapping relationship to provide coupling between the first and second RF transmission lines, and said first and second tracks are capable of relative rotation about said rotation axis to tune the filter to the desired frequency.
The first and second electrically conductive tracks may comprise continuous electrically conductive layers or films formed by any suitable deposition technique such as screen printing or electrodeposition. Alternatively the tracks may be turned or wire wound.
DESCRIPTION OF THE DRAWINGS
Embodiments according to the invention are now described, by way of example only, with reference to the accompanying drawings in which:
FIG. 1 shows a longitudinal sectional view through one embodiment of an RF coup
REFERENCES:
patent: 3143717 (1964-08-01), Gordon
patent: 5192923 (1993-03-01), Komatsu
patent: 5668514 (1997-09-01), Hashino et al.
Gensler Paul
Racal-Mesl Limited
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