Antenna assembly
A wireless magnetic resonance imaging scanner antenna assembly has a radio frequency antenna array having a number of RF antenna rungs, a microwave antenna array having a number of microwave antenna elements, and a number of antenna feeds. The rungs and elements are grouped together in feed subsets, each subset having at least one feed rung, one non-feed rung and associated microwave antenna elements. Signal transfers between a feed rung and a non-feed rung of a subset are made at a point on the feed rung, within a region of minimum potential.
1. A wireless magnetic resonance imaging scanner antenna assembly comprising:
a radio frequency (RF) antenna array comprising a plurality of RF antenna rungs; a microwave antenna array comprising a plurality of microwave antenna elements;
a plurality of antenna feeds;
said rungs and elements being grouped together in feed subsets, each subset comprising at least one feed rung, one non-feed rung and associated microwave antenna elements; and
signal transfers between a feed rung and a non-feed rung of the subset being made at a point on the feed rung, within a region of minimum potential determined from the breakdown voltage of air and the distance between pads of capacitors required to maintain a good microwave path with less than 0.5 dB insertion loss.
2. An assembly according to claim 1 , comprising a distribution ring is mounted within the region of minimum potential.
3. An assembly according to claim 1 , wherein the region of minimum potential is substantially at the mid-point of the rung in the z direction of the bore tube.
4. An assembly according to claim 1 , wherein the region of minimum potential is at one end of the antenna rung.
5. An assembly according to claim 1 , wherein the RF antenna comprises an even number of antenna rungs.
6. An assembly according to claim 1 , wherein each subset comprises 0.125 or greater the number of rungs in the RF antenna array.
7. An assembly according to claim 1 , wherein each subset comprises 0.125 or greater the number of antenna elements in the microwave antenna array.
8. An assembly according to claim 1 , wherein the number of feed rungs in the assembly comprises 0.125 of the total number of rungs in the RF antenna array.
9. An assembly according to claim 1 , wherein the antenna rungs are printed on an outer surface of a bore tube spaced at equal intervals around the bore tube.
10. An assembly according to claim 1 , wherein the antenna elements are mounted between adjacent rungs.
11. An assembly according to claim 1 , comprising capacitive coupling between adjacent rungs that produces said signal transfer between adjacent rungs.