Perhaps you should try some spelling variations:
"ground generating radar" » "ground penetrating radar", "sound generating radar", "group generating radar", "ground penetrating radars", "ground generating random"
"groups generating radar" » "groups generation radar", "groups generated radar", "groups generators radar", "groups penetrating radar", "groups penetrating radars", "groups generating random"

Try widening your search to All Fields.

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"ground generating radar\") OR (\"groups generating radar\"))".
• Removing quotes may allow a broader search: (( ground generating radar ) OR ( groups generating radar )).
• Adding a wildcard symbol may retrieve word variants: (("ground generating radar") OR ("groups generating radar"))*.