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What is antenna diversity?

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Antenna diversity uses two or more antennas whose received signals fade independently, so the chance of all being in a deep fade at once is small. Diversity branches are obtained by spatial separation, orthogonal polarizations or different patterns, and combined by selection, equal-gain or maximal-ratio combining. Vaughan and Andersen showed the importance of envelope correlation and branch power balance to diversity gain.[1][2]

How much spacing is needed?

In uniform 2D scattering (Clarke’s model), the correlation between two vertical antennas follows J0(2πd/λ)², which first reaches zero near d ≈ 0.38λ; λ/2 is a common rule. Base stations with narrow angular spread need ten or more wavelengths of horizontal separation.[2][3]

What gain does diversity give?

At 1% outage in Rayleigh fading, two-branch selection diversity yields roughly 10 dB of improvement over a single antenna, and maximal-ratio combining a little more, provided branches are uncorrelated and balanced.[2]

Where is diversity used?

Wi-Fi access points and clients, Bluetooth and IoT radios with antenna switching, cellular base stations (polarization diversity with ±45° slant antennas), vehicles and broadcast receivers.[3][1]

Frequently asked questions

Is diversity the same as MIMO?

Diversity improves reliability of one stream; MIMO also multiplexes several streams.

Can two antennas on a small device give diversity?

Yes, via pattern and polarization differences, if coupling and correlation are controlled.

What is switched diversity?

Selecting one of several antennas based on received signal quality.

References

Online sources accessed October 21, 2026; printed works cited by edition. See all sources.

  1. “Antenna Diversity in Mobile Communications”. R. G. Vaughan and J. B. Andersen, IEEE Transactions on Vehicular Technology, vol. 36, no. 4, pp. 149-172. November 1987.
  2. “Wireless Communications, 2nd ed.”. A. F. Molisch, Wiley. 2011.
  3. “Antennas and Propagation for Wireless Communication Systems, 2nd ed.”. S. R. Saunders and A. Aragón-Zavala, Wiley. 2007.
Categories: Arrays and beamforming