How do antenna arrays and beamforming work?
An antenna array combines elements so their fields add in chosen directions. For N equally spaced isotropic elements with spacing d and progressive phase β, the array factor is AF = Σ ejn(kd·cosθ + β); the main beam points where kd·cosθ + β = 0. Total pattern = element pattern × array factor. Steering the beam electronically by changing β makes a phased array.[1]
How are grating lobes avoided?
Grating lobes (extra main beams) appear when spacing is too large. For a linear array scanned to θ0 from broadside, require d < λ/(1 + |sin θ0|); λ/2 spacing avoids grating lobes for any scan angle.[1]
What gain does an array add?
Ideally, an N-element array adds 10·log10(N) dB of directivity over one element; in transmit, using N amplifiers also adds 10·log10(N) of combined power, so EIRP scales as 20·log10(N). Scan loss reduces gain away from broadside, roughly as the element pattern (often approximated by cosnθ).
What beamforming architectures exist?
- Analog: phase shifters or true-time-delay at RF or IF; one beam per chain; efficient.
- Digital: a transceiver per element; multiple simultaneous beams, highest flexibility and power.
- Hybrid: analog subarrays feeding digital chains; common in 5G mmWave.
Phase shifters cause beam squint over wide bandwidth; true time delay avoids it.
How are sidelobes controlled?
Amplitude tapering (Taylor, Chebyshev, cosine) lowers sidelobes at the cost of wider beamwidth and lower aperture efficiency.[1]
Frequently asked questions
Why λ/2 spacing?
It prevents grating lobes for all scan angles.
What is beam squint?
Frequency-dependent beam pointing in phase-shifter arrays.
What is MIMO?
Using multiple antennas for spatial multiplexing or diversity; beamforming is one technique within it.
See also
References
Online sources accessed October 21, 2026; printed works cited by edition. See all sources.
- “Antenna Theory: Analysis and Design, 4th ed.”. C. A. Balanis, Wiley. 2016.