Perhaps you should try some spelling variations:
"imsparse signals" » "sparse signals", "sparse signal", "response signals"
"impulse signals" » "pulse signal", "impulse signal", "imsparse signals", "imprice signals"
"pulse signals" » "pulse signal", "sparse signals", "price signals"

Try widening your search to All Fields.

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: (("pulse signals") OR ((("impulse signals") OR ("imsparse signals")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"pulse signals\") or (((\"impulse signals\") OR (\"imsparse signals\"))))".
• Removing quotes may allow a broader search: (( pulse signals ) or ((( impulse signals ) OR ( imsparse signals )))).
• Adding a wildcard symbol may retrieve word variants: (("pulse signals") or ((("impulse signals") OR ("imsparse signals"))))*.