Topic: Electromagnetics
To increase gain of a parabolic reflector antenna by 6 dBi, the correct statement is (Assuming efficiency 70%)
- A. Diameter is to be increased to 6 folds
- B. Diameter is to be increased to 4 folds
- C. Diameter is to be increased to 2 folds
- D. None of above
Answer: C. Diameter is to be increased to 2 folds
Explanation: $G=\eta\frac{4\pi A_{e}}{\lambda^{2}}=\eta\frac{4\pi\cdot\pi D^{2}}{4} = X~dB$ (suppose). If the diameter is increased to 2 folds i.e. $D'=2D$ then gain in dB will increase by $10~log_{10}4 = 6.02~dBi$.