In order to achieve ideal coverage, what is the clearance requirement around an antenna?

In order to achieve ideal coverage, there should be a clearance zone around an antenna of at least d, where d is the Fraunhofer or Rayleigh distance at which the near/far-field transition zone exists 17. This distance depends on the largest dimension of the antenna, D, and the operating wavelength, \uF06C. Ideally, D should be at least a half of a wavelength, which gives a minimum clearance zone of a half-wavelength. For example, at 2.4 GHz, the wavelength is about 0.125 m, so the minimum clearance zone is about 0.0625 m. However, in practical situations, this clearance zone is often compromised and the effects must be determined through simulation or empirical measurement 18. A general guideline is to have a clearance zone of 5-10 m around an antenna to avoid significant degradation of performance 19. Therefore, the best answer is C.