Overview
Phased-array technology is well established, having been used for decades in military systems. Recently, its use in 5G systems in the sub-6 GHz and millimeter-wave bands has attracted attention because it can improve signal strength, gain, directivity, and bandwidth. A phased array uses multiple antenna elements and controls the relative phase of each element to steer the radiation pattern or beam. Antenna elements are connected via microwave transmission lines and power dividers. Beamforming in phased-array design relies on interference between two or more radiated signals to control the transmitted beam direction.
The antenna achieves beamforming by adjusting phase differences among the drive signals feeding each transmitter in the array. The number of transmitters in a phased array can range from a few to several thousand.
How phased arrays work
When signals from each transmitter are in phase, they interfere constructively and produce strong radiation in a specific direction. The radiation direction is controlled by setting phase shifts on the signals sent to different transmitters. These phase shifts are implemented as small delays between signals fed to successive transmitters. Using phase shifters, a phased array can synthesize hundreds of beams.
Phased-array antenna types
- Linear array
Elements are arranged along a single line. In this configuration, only a single phase shifter per line is required, and beam steering is limited to a single plane. To create a planar aperture, multiple linear arrays must be stacked vertically. - Planar array
Each antenna element has its own phase shifter. By arranging elements in a matrix, a planar antenna is formed and beams can be steered in two dimensions. This architecture requires many phase shifters, increasing complexity and cost. - Frequency-scanned array
Phase shifters are not required in this architecture. Beam steering is achieved by varying the transmitter frequency.
Figure 1: Phased-array antenna working principle. Source: ADI
Digital beamforming techniques that support multiple simultaneous beams are advancing. These replace fixed circuits with reconfigurable networks. A reconfigurable network can add or reconfigure antenna array elements, adapt operation, and enable performance improvements via software updates. Digital beamforming removes narrowband limitations and supports wideband operation. A single antenna architecture can provide capabilities required for radar, communications, and electronic warfare.
Applications
In military and aerospace radar, phased arrays provide higher performance and flexibility, low profile, rapid reprovisioning, and easier multi-target tracking. For military communications, they can connect to multiple unmanned vehicles and low-earth-orbit satellites simultaneously, supporting faster and more efficient signal handoff. Electronic warfare use cases include electronic attack and platform protection, enabling directional control of jamming and precise geolocation of hostile signals even in noisy electromagnetic environments. In space, phased arrays can meet satellites' wideband requirements.
Phased arrays are also important for 5G. For 5G systems, phased-array antennas enable wider bandwidths, greater range, and higher capacity at millimeter-wave bands. Millimeter-wave systems are relatively easy to deploy for short-range indoor use, but outdoor deployments face propagation loss, rain attenuation, atmospheric absorption, and high loss from blockage and shadowing.
Recent semiconductor advances have produced more cost-effective phased-array solutions used in satellites, radar, and 5G. For example, a commercial satellite terminal integrates hundreds of small antennas synchronized to picosecond precision to implement a phased-array system. By adjusting delays among the antennas, a single terminal can track multiple satellites without mechanical motion.
ADI and Keysight Technologies have announced cooperation on phased-array technology. ADI's phased-array platform is used to accelerate beamforming development, while Keysight provides phased-array test solutions. The collaboration aims to offer a design, test, and calibration ecosystem to reduce development and validation time.
Figure 2: Test and calibration are important components of the phased-array technology ecosystem. Source: Keysight Technologies
Future directions and challenges
Challenges remain. Although modern digital phased-array radios and differential RF front ends improve link linearity, noise, and dynamic range, overall efficiency is often low. Future cellular generations require antenna arrays that deliver wideband performance with lower complexity and higher efficiency in fewer integration steps. Millimeter-wave frequencies demand scalable, manufacturable solutions, which are still under development. Simplifying array architectures, reducing cost, improving efficiency, and expanding scan range are key objectives. Renewed interest and collaborative efforts are expected to drive rapid technical progress.
