A phased array is a group of antennas whose effective (summed) radiation pattern can be altered by phasing the signals of the individual elements.
By varying the phasing of the different elements, the radiation pattern can be modified to be maximized / suppressed in given directions, within limits determined by various factors, such as:
- The radiation pattern of the elements
- The size of the array
- The configuration of the array
Phased arrays were invented for use in military radar systems, to steer a beam of radio waves quickly across the sky to detect planes and missiles. But today, phased-array radar systems have evolved so that this technology is used in civilian applications also.
A phased array antenna is typically a computer-controlled array of antennas. Normally, when a signal is broadcast from multiple antennas there is a risk of an interference pattern that can cause a reduction in signal strength. For radars, this can lead to a misrepresentation of the radar target’s size, as well as false positives or negatives.
However, an interference pattern can be used to improve a radar’s accuracy. By carefully controlling several beams of radio waves, a constructive interference pattern can be created which boosts the signal strength.
By adjusting the phase relationship between the antennas, the signal can be electronically ‘steered’ to point in different directions without moving the antennas, this is known as beamforming.
Beamforming can be achieved with as few as two antennas, but phased array antennas number in the hundreds or thousands of individual antennas.
Beamforming is especially beneficial for radar as it can reduce signal radiation in some directions while boosting the signal radiation in the desired direction.
Consequently, the accuracy of the radar reflection signal is substantially improved. The large number of antennas in the system also add redundancy, which can be invaluable in mission-critical applications, such as aerospace and defense.
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