Far field zone of a single antenna can be determined by using the equation below.


Where D is the biggest dimension of the antenna.

This equaiton is suitable for single antenna. But what if there are more antennas than one?

How can we determine rayleigh distance, far-field distance, of an array antenna? For example, how can I determine far-field distance of an two element (aperture type antennas) linear array antenna as shown below?

enter image description here

  • \$\begingroup\$ The far-field region is \$> \dfrac{2D^2}{\lambda}\$. It doesn't equal it. \$\endgroup\$
    – Andy aka
    Jun 30, 2020 at 10:29
  • \$\begingroup\$ I edited it @Andyaka \$\endgroup\$ Jun 30, 2020 at 10:34

1 Answer 1


The answer is still $$2D^2/\lambda$$ but we need to define D value correctly.

Rayleigh distance of a single horn antenna can be calculated as shown below. $$R=\dfrac{4A^2}{\lambda}$$

We can define D of array antenna as shown below.

enter image description here

Rayleigh distance of an array antenna can be calculated as shown below. $$R=\dfrac{2(4A+A)^2}{\lambda}=\dfrac{50A^2}{\lambda}$$


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