What is a Phased Array Antenna?

Phased Array Antennas are antenna systems that can electronically control the direction and shape of their radiation pattern without any physical movement. This capability allows them to steer beams rapidly and accurately, making them highly versatile for modern wireless and radar applications.

A phased array consists of multiple individual antenna elements arranged in a specific geometry. Each element transmits (or receives) signals at the same frequency, but with carefully controlled phase differences. When these signals combine, they reinforce each other in a desired direction (constructive interference) and cancel out in other directions (destructive interference). This results in higher gain, improved directivity, and better overall system performance.

The required phase shift for each antenna element depends on the desired beam direction. Calculating and applying these phase shifts involves complex mathematical models and is handled by a computer-controlled system.

Passive Electronically Steered Array (PESA)

At a fundamental level, beam steering in phased array antennas is achieved by precisely controlling the relative phase of the signals associated with each antenna element. By applying calculated phase offsets across the array, the combined electromagnetic waves reinforce one another in a chosen direction and cancel out elsewhere, effectively steering the beam electronically. This phase control can be implemented using analog, digital, or hybrid techniques, depending on the phased array architecture.

Phased Array Antennas can consist of a few elements or scale up to hundreds or even thousands of elements. The physical size of each antenna element is inversely proportional to the operating frequency - higher frequencies allow for smaller antennas. As a result, phased arrays are especially well suited for high-frequency applications such as millimeter-wave (mmWave) 5G systems and other compact, high-performance RF systems where space is limited.

Phased Array Antennas on a PCB

Types of Phased Array Antennas

Phased Array Antennas can be broadly categorized into four commonly used types:

1. Passive Electronically Steered Array (PESA)
2. Active Electronically Steered Array (AESA)
3. Digital Beam Forming (DBF)
4. Hybrid Beam Forming (HBF)

Passive Electronically Steered Array (PESA)

In a Passive Electronically Steered Array (PESA), a single transmitter generates the RF signal for the entire antenna array. This signal is then distributed to each antenna element through individual phase shifters. A computer-controlled phase controller adjusts these phase shifters electronically, enabling beam steering without mechanical movement.

PESA systems are often considered the first generation of phased array antennas and have been widely deployed in early radar, defense, and some commercial applications.

Active Electronically Phased Array

Active Electronically Steered Arrays (AESAs) represent the second generation of phased array technology. In an AESA, each antenna element has its own dedicated transmitter and/or receiver module, all controlled by a central processing system.

This architecture provides greater flexibility than PESA systems. AESAs can transmit multiple beams simultaneously, operate across different frequencies, and offer improved reliability since the failure of a single element does not disable the entire array.

AESA Basic Schematic

Digital Beam Forming

In Digital Beam Forming (DBF) phased arrays, each antenna element is connected to its own digital receiver. The received RF signals are converted into digital data at the element level and then processed using digital signal processing hardware, such as a Field Programmable Gate Array (FPGA).

Because beamforming is performed digitally, DBF enables extremely precise beam control, adaptive beam shaping, and the simultaneous formation of multiple independent beams.

Hybrid Beam Forming

Hybrid Beam Forming (HBF) combines features of both analog and digital beamforming approaches. In this architecture, antenna elements are grouped into subarrays, each driven by a separate transmitter or receiver chain.

These subarrays are then combined to form the full antenna array. By using multiple subarrays, HBF systems can generate clusters of beams simultaneously while reducing system complexity, cost, and power consumption compared to fully digital beamforming systems.

PESA fitted on the tip of a fighter jet

Applications of Phased Array Antennas

Phased Array Antennas were originally developed for military radar systems and have been used in defense applications for decades. Over time, their use has expanded into a wide range of fields, including broadcasting, satellite and space probe communication, weather monitoring, optics, and human–machine interfaces.

Today, phased arrays play a critical role in modern commercial wireless technologies such as 5G and Wi-Fi 6, where fast beam steering, high data rates, and efficient spectrum usage are essential.