Thursday, 19 December, 1996

Radar has Principles

This document is still

 Under Construction road sign - a 60 k gif

Radar has many Principles. But you know what they say? Radar scientists (and engineers) employ few of them; they just do it remotely

Principles of Radar

A brief description of radar operation.

  • Transmitters How we get high power and radiate into Space.
  • Low Noise Amplifiers The very sensitive first stage of the receiving chain; snatching the echo from oblivion.
  • Receiver Making the echo a useful size for the cunning of the
  • Data Acquisition System, the journey from mere echo numbers to an image for Radar science.

We do not usually realise that we see almost everything by reflected light. We see directly only those things which are sources of light - a light bulb filament, a fire, a neon sign, the Sun. These are the exception, for it is these which actually give light, and life, to all the other objects around us. In the dark, a flickering candle illuminates in a general and imprecise way. A flashlight or torch can direct a beam of light to a considerable distance. Those objects so caught in the beam reflect some of the light energy, allowing us to see and to inspect that which in our "dark" is not "visible", things both close and distant. That is how we see them. We can identify them from what gets back to our eyes. Different things reflect differently - materials, colors, shapes - and our brain is usually very good at recognising what we see. If the beam of light is not very strong when it gets to the object, or the object does not reflect well, we have trouble saying what it is; we may have to look many times before being certain, Even then, the body lying in the corner may actually be a white laundry sack!

So it is with radar. We have a beam, not of visible light but of a related energy, microwave radiation. We can direct this into the sky. If there is something in the path it may reflect. If we are looking we may see that reflection. If we are cute we may make something of it. That's it! Radar in a nutshell! It is just like shining a light toward, ... and seeing.

As Shakespeare (probably) said: "There's many a slip 'twixt cup and lip". If it were as easy as turning on a light bulb, everybody could do it.

Transmitter Power - the first step

How we get high power and radiate into Space.

First problem is we need lots of power, but lots, to be able to see well at planetary distances. Generating electrical power takes power stations. We have our own, at Goldstone, diesel powered, low voltage, same as the electricity utilities. We take this and transform it in steps from low voltage to ver