Radars are an incredible invention which have been utilised for many decades in all sorts of industries, from to commercial travel and weather surveillance to national defence. Since 1934, radars have been used for aeroplane tracking, which is quite remarkable considering the lack of technology during this period.
Radars have helped air traffic controllers land planes safely, astronauts return to earth in one piece and military personnel spot enemy aircraft in the sky for almost 80 years.
How they work
Radars can detect moving objects by sending out waves into the atmosphere and detecting echoes. These waves can detect the distance and speed of an item based on the timing and the frequency of the echoes.
Technology has also been developed so that radars can request additional information, such as identity, altitude or faults, from aeroplanes. This technology is commonly known as secondary radar.
Radars send out waves using two different methods – either pulse-modulated or continuous wave.
The pulse-modulated method, often shortened to ‘pulsed’, involves the sending of waves on an intermittent basis. After each wave is sent, the radar then ‘listens’ for an echo. The quicker this echo returns, the closer the aircraft.
Pulse-modulated radars send out up to 2,000 pulses per second, depending on the distance it is expected to monitor. Longer-range radars might only send around 250 pulses per second.
Continuous Wave Radar (CW)
Continuous wave radars, as the name might suggest, constantly send out waves. They detect the whereabouts of planes by measuring the changes in frequency of the returning waves. The frequency will rise if a plane is moving closer and drop if it’s moving further away. This is called the Doppler Effect.
Another type of CW radar varies the frequency of the signal it sends out and can determine a plane’s position by the time amount of time it takes to return. It works almost as an inverted Doppler Effect. This is called FMCW.
Secondary radar was developed shortly before World War II and proved essential for Britain in identifying enemy aeroplanes. There could have been a lot more friendly fire had this technology been developed, that’s for sure.
The system, called Identification Friend or Foe (IFF), allowed British aircraft to communicate with British radars so they could be identified as friendly. Any aircraft that didn’t communicate was presumed to be an enemy. This technology is still used during air conflict today, although have been various calls for it to be upgraded after a series of friendly fires in recent times.
A non-military version of this technology, called Secondary Surveillance Radar (SSR), proves very useful to air traffic controllers. Potentially vital information, such as the height, speed or potential problems can be sent to them using coded pulses of information. The technology is much better at identifying clouds, birds and the like as unimportant moving items.
Users of secondary radars have can identify planes quicker and easier whilst gathering potentially priceless information in the process. In this day and age, they arguably become essential in a number of industries.
Rob Dunham, a science graduate is very much passionate about latest technology, mobiles, different types of iPhone apps and gadgets. Currently he resides in Hampshire, UK. Rob is an IT professional and loves to write on Tech gadgets review. You may connect him via Google+