What is a phased array antenna?
A phased array is an array antenna whose beam is steered electronically by setting the relative phase, or time delay, of each element’s signal. Applying a progressive phase β = −kd·sinθ0 (θ0 from broadside) points the beam toward θ0 in microseconds without moving parts; this underpins modern radar, satellite user terminals and 5G mmWave.[1][2]
What are passive and active arrays?
A passive electronically scanned array (PESA) uses one transmitter/receiver and a phase shifter per element. An active electronically scanned array (AESA) places a transmit/receive module with its own amplifiers at each element or subarray, reducing feed loss, enabling graceful degradation and supporting multiple beams. Digital arrays add a converter per element or subarray.[1][3]
What happens when the beam is scanned?
- Beamwidth broadens roughly as 1/cosθ0 because the projected aperture shrinks.
- Gain drops by roughly cosθ0 (scan loss), more in practice due to element patterns and mismatch.
- The active impedance changes with scan, so mutual coupling can produce scan blindness.
- Grating lobes appear if spacing is too large; see beam steering.[1]
Why does phase steering cause beam squint?
A fixed phase shift corresponds to the correct delay at only one frequency. Across a wide band the beam direction changes with frequency (squint) by Δθ ≈ −(Δf/f)·tanθ0; wideband arrays use true-time-delay units at subarray or element level.[1][4]
Frequently asked questions
How fast can a phased array steer?
Microseconds or less, limited by control electronics.
What scan range is typical?
About ±45° to ±60° from broadside for planar arrays.
Are phased arrays used in consumer products?
Yes, in mmWave 5G phones and satellite broadband user terminals.
See also
References
Online sources accessed October 21, 2026; printed works cited by edition. See all sources.
- “Phased Array Antenna Handbook, 3rd ed.”. R. J. Mailloux, Artech House. 2017.
- “Phased Array Antennas, 2nd ed.”. R. C. Hansen, Wiley. 2009.
- “Introduction to Radar Systems, 3rd ed.”. M. I. Skolnik, McGraw-Hill. 2001.
- “Phased Array Antenna Patterns — Part 1: Linear Array Beam Characteristics and Array Factor”. P. Delos, B. Broughton and J. Kraft, Analog Dialogue (Analog Devices). 2020.