Sentence:  The transducer itself moves the beam in a sector scan , just like a <WSD>radar</WSD> antenna , while the entire transducer structure is moved over a 90 - degree arc in front of the eye to `` look into '' all corners . 
Meaning of the word marked with <WSD> tags:  measuring instrument in which the echo of a pulse of microwave radiation is used to detect and locate distant objects