What is Beam Squint?

Beam Squint is a phenomenon in which the main beam of a phased array antenna system changes direction unintentionally due to a change in the signal frequency. This means that for a given beam direction, the phase shift required changes as a function of frequency. Beam squint can result in performance degradation because the antenna's main beam may not be aligned with the intended direction of transmission or reception at specific frequencies, leading to reduced signal strength and increased interference. 

Beam squint can be calculated using the following formula

Phased array antennas are designed to work in a specific frequency range; whenever these antennas are operated outside the designed range, beam squint causes the main beam to point in a different direction than intended, which results in misalignment with the target or desired coverage area.  

In applications such as radar systems or satellite communication, precise beam steering is required for accurately tracking moving satellites or targets. Beam squinting introduces errors in beam pointing direction as the frequency changes, leading to inaccuracies in tracking and thereby causing loss of signal lock or tracking failures.  It can cause several issues, the most important of which are its detrimental effects on gain, line of sight, angle of arrival, progressive phase, usable bandwidth, and fading effect. As a result of these obstacles, the advantages of adopting a high-frequency band such as a millimetre wave in modern wireless communication systems are limited. Squint-related difficulties, such as decreased channel capacity, increased bit error rate (BER) and lower service quality, may substantially harm channel performance.

How can you Mitigate Beam Squint? 

Various techniques can be employed to minimize beam squint, such as Calibration of phase shifters and other components to reduce the phase error, digital beamforming of the signal to compensate for phase errors dynamically, and adjusting the array factor can also help to align the main lobe. 

Calibrating a phased array antenna to mitigate beam squint effects can be complex and time-consuming. It involves accurately characterizing the frequency-dependent phase shift of each antenna element and compensating for these shifts to maintain beam-pointing accuracy across the operating frequency range.

What causes Beam Squint? 

The distance between the antenna elements in a phased array antenna affects how effectively they can combine signals. If the spacing is too large, especially at high frequencies, it can cause phase shifts, contributing to beam squint. Also, mechanical misalignment of antenna elements or reflector components can create path length differences, resulting in squints. Mechanical imperfections or tolerances in antenna components can contribute to phase errors and squint.