Perhaps you should try some spelling variations:
medium connectivity » media connectivity, maximum connectivity, minimum connectivity
medium directivity » medium radioactivity, edge directivity, medium activity
beam directivity » array directivity, field directivity, beamwidth directivity

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((beam directivity) OR (((medium directivity) OR (medium connectivity)))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((beam directivity) or (((medium directivity) OR (medium connectivity))))".
• Adding a wildcard symbol may retrieve word variants: ((beam directivity) or (((medium directivity) OR (medium connectivity))))*.