What Are Phased Arrays?

Phased arrays are systems of spatially distributed transmitting or receiving elements whose individual signals are combined with controlled phase offsets, enabling the composite beam to be steered electronically without moving parts. By setting a progressive phase delay across the elements, the system causes signals from all elements to combine constructively in a chosen direction and destructively elsewhere, forming a narrow, steerable beam. The principle applies equally to electromagnetic waves in radio and microwave systems, to light in optical systems, and to acoustic waves in ultrasonic and sonar systems, making phased arrays one of the most broadly deployed beam-control technologies across physics and engineering.

The key parameters of a phased array are the number of elements, the element spacing (typically lambda/2, where lambda is the operating wavelength), the phase resolution of the control system, and the amplitude weighting applied across the aperture to manage sidelobe levels. Larger element counts produce narrower beams and higher directional gain; amplitude weighting with functions such as Taylor or Chebyshev tapers trades peak gain for reduced sidelobe levels. Smart antennas add adaptive signal processing on top of these basic steering operations to track desired sources and null out interferers.

Radio-Frequency and Microwave Phased Arrays

RF phased arrays originated in radar, where the ability to scan a high-power beam in microseconds conferred decisive advantages for tracking fast-moving targets. Modern active electronically scanned array (AESA) radars assign each element its own transmit/receive module, allowing simultaneous formation of multiple independent beams, graceful degradation when modules fail, and per-element amplitude and phase control. The same architecture underlies 5G millimeter-wave base stations, where integrated silicon beamforming chips handle phase shifting, variable gain amplification, and switching for arrays of 64 or more elements in a compact module.

The Analog Devices technical resource on phased array antenna patterns explains how the array factor controls beam width, sidelobe level, and grating lobe formation, providing the quantitative foundation for array design across radar, satellite, and wireless applications.

Optical Phased Arrays

Optical phased arrays (OPAs) extend the phased array concept to near-infrared and visible wavelengths, using arrays of waveguide emitters or apertures on a photonic integrated circuit. Thermo-optic or electro-optic phase modulators control the phase at each emitter; combining all emitters on-chip allows solid-state beam steering across tens of degrees without mechanical scanners. A 2025 review in npj Nanophotonics on photonic integrated circuit OPAs reports point-to-point steering rates approaching 1 GHz in integrated OPA designs, with applications in LiDAR for autonomous vehicles, free-space optical communications, and remote sensing. Continued miniaturization of OPA chips is bringing solid-state LiDAR from research toward production.

Ultrasonic and Acoustic Phased Arrays

Acoustic phased arrays transmit and receive pressure waves rather than electromagnetic radiation, but share the same beam-forming mathematics. Medical ultrasound phased-array probes contain 64 to 128 piezoelectric elements driven with programmable delays, allowing real-time sector scanning of cardiac structures and abdominal organs from a small handheld transducer. In nondestructive testing, phased array ultrasonic testing as described by ASNT enables beam steering and dynamic focusing to detect and size flaws in welds, composites, and structural components, replacing multiple single-element probes with one configurable instrument.

Two-dimensional matrix arrays extend steering to both azimuth and elevation for three-dimensional volumetric imaging in both medical and industrial contexts.

Applications

Phased arrays have applications across a wide range of disciplines, including:

• Air defense, weather, and air traffic control radar with electronic beam steering
• 5G millimeter-wave and satellite communication antenna systems
• Autonomous vehicle LiDAR using photonic integrated circuit OPAs
• Cardiac and abdominal medical ultrasound imaging
• Phased array ultrasonic testing for weld and composite inspection
• Free-space optical communication terminals