National Engineering Week - Special Edition

Over the last four days I've tried to share a little bit about the different facets of engineering and how it affects people on a day to day basis. What I hope you've gotten out of it is that engineers are very useful folk to have around, even if our contribution to society is not as immediately obvious as doctors and teachers.

To wrap up the series I want to try and give a brief introduction to microwave engineering, which is my field of professional interest. Microwave engineering is all about the generation, transmission, detection, and processing of signals at microwave frequencies. What are microwave frequencies you ask? Anything from 300 MHz to 30 GHz is considered microwave. 30 GHz to 300 GHz is considered millimetre wave. The reason for this is that at 30 GHz, the wavelength of the signal (i.e. the distance between one peak and the next) is 10 millimetres. Below microwave frequencies we have radio frequency in the 30-300 MHz range. Oh, and MHz is short for megahertz, which means the signal goes up and down one million times per second. GHz is short for gigahertz - one billion times per second. In perspective, humans can hear frequencies from around 80 Hz up to 40 kHz. Concert pitch, or A-440 is 440 cycles per second.

Some situations where people use microwaves:
- FM radio (RF, around the 100 MHz region)
- cordless phones, mobile phones, bluetooth and any of your wi-fi/wireless network connections (anywhere from 900 MHz to 5.4 GHz depending on what it is)
- GPS navigation (around 1.3-1.5 GHz)
- Microwave ovens
- Point to point communication links (the dishes that look like a squat grey cylinder on the side of buildings and TV towers)
- Police radar
- Weather radar
- Vehicle anti-collision radar
- Air traffic control radar
- Military radars

My work is mostly related to the last item on the list. In the military environment there are basically two groups of microwavers. Those on the radar side, who try to generate signals to find and track other ships/aircraft/whatever, and those on the countermeasures side, who try to pick up the radar before it sees you, or send out a fake signal to make the radar think you're somewhere else.

I don't actually build the systems that do those sort of things. The company where I work builds some of the components that go into those systems. It's interesting, and it's challenging because not only do you have to deal with very small spaces (I know aeroplanes look big on the outside, but there's not much space inside for this sort of thing) you also have to deal with severe environmental conditions like very high temperatures (85 Celsius is normal), very low temperatures (it gets down to below -40 Celsius at cruising altitude), dust, salt, vibration, and high shocks (like when a missile hits a few metres away, or when an aircraft launches from a catapult).

The observant among you would also have noted that I mentioned photonics a few days ago. Photonics is a branch of fibre optics, using light waves to transmit and process these signals. The cables that make international phone calls and the internet possible are all fibre optic cables now. The infamous national broadband network (which is a great concept turned into a stinking mound of sewerage by the government and beauraucrats) also uses fibre, lots of it.

Naturally I think all of the above are some of the great things that microwave engineers are involved in. When we get things wrong they're not usually as spectacular as a bridge falling down, but still worth acknowledging. The microwave mortuary has a lot reports, scroll down to an entry from late 2006 for one that I'm quite familiar with... Warning: this page has heaps of photos so will take a while to load, even over broadband.

So there you have it. Engineers are everywhere, doing all sorts of stuff. Like doctors, we're very useful unless we make a mistake, which tends to upset people.

Thanks for reading.