Phased array antenna - electronically steerable beam
Phase Shifting: By applying progressive phase delays across elements, the beam direction changes without physical movement.
Array Factor: AF(θ) = Σ exp(jn(kd·sinθ - Δφ)) where Δφ controls steering.
Beamwidth: ≈ λ/(N·d·cosθ). More elements = narrower beam = higher gain!
Grating Lobes: When d > λ/2, secondary main beams appear at other angles.
Applications: 5G mmWave, radar (AESA), satellite (Starlink), Wi-Fi 6.