Q. An antenna has a field pattern E (θ) =cos θ. cos 2θ. The first null beam width of the antenna is:
β
Correct Answer: (B)
900
Explanation: half power beam width of the antenna is obtained by equating the field pattern of the antenna to 0.707 (half power point) and finding θ. 2θ gives the value of beam width. twice the half power beam width gives the first null beam width. with the same steps applied, the half power beam width of the antenna is 450. first null beam width is 900.