A simple explanation of phased array radar.

I keep seeing buzzwords such as AESA being thrown around, with little regard to the advantages and design concepts of an phased array radar. Most people come out with comments that its somehow better, and allows longer ranged more accurate tracking. Well, thats true, partially, but let me explain why it is true, and give better insight on other advantages.

First, let me give an idiot proof explanation on how this type of radar works. To make things simple, lets pretend what we are working with is 2D, and that our hypothetical phased array has only 5 distinct antennas.

Lets pretend we’re in a pond. A rock is dropped in the pond.

(Note: I suck with MSPaint, bear with me)

Waves propagate outwards from the rock in a circular fashion. However, at longer ranges, a circular spread becomes very close to linear.

At least, close enough to make calculation much simpler. A more advanced array will compensate for the very slight distortion of the radio wave. However, to simplify things, I’ll consider the wave a flat line, which it basically is at longer ranges.

A phased array has multiple antennas, or T/R modules for you AESA obsessed buzzword wielders.

This particular array constructed in MSPaint has 5 modules. The wave hits first the antenna nearest to the source. Then hits the rest of the antennas one after another.

Every single time an antenna is hit, a computer records the signal, by seeing which antennas are hit first, it is possible to figure out the direction of the signal. A timing of the pulse gives you the range of the signal.

Measuring the angle is relatively simple. First, lets assume the antennas are one wavesecond apart.(waves traveling at one wavesecond per second). Now, lets assume it takes ½ of a wavesecond for the wave to hit the second antenna after hitting the first antenna.

This creates a very simple right triangle.

So, we do a basic high school geometry problems, (arcsin(1/2)+90) and find the angle to the target.

Simple? Remember that there are many many other factors to consider. Such as filtering out atmospheric noise, ECM, and transmitting at the same time. Transmission works in a similar manner, expect it relies on radio waves of the same wavelength to bounce off partially bounces off eachother to direct the beam. If anyone wants an explanation of how to transmit directionally with an phased array, I’d be happy to write a guide for that.

Now, for the more important part in the next post, why phased array? What are the advantages and disadvantages of using a phased array? Whats the difference between a passive one and an active one, etc….