Ranges (FMCW)

In this lesson you will learn:

  • How FMCW Radar works
  • How ranges are measured with FMCW radar
  • Advantages of FMCW Radar

Frequency Modulated Continuous Wave is a bit of a mouthful so this technology has a variety of other names from different manufactures, such as Broadband, chirp or solid state - and whilst there are some subtle differences, ultimately they are variations on the same technology.

As the name suggests, the transmit frequency of the radar is modulated, this means it has a changing frequency, and the radar transmits constantly. The term 'broadband' radar stems from the idea that the radar frequency varies within a defined bandwidth of around 40 MHz. They are the same thing, just different names.

An FMCW radar may for example transmit a repeating signal starting from 9400 MHz ramping up to 9440 MHz, sweeping between these 2 frequencies continuously would give the radar a 'broad-band' of 40 MHz to operate within.

2 big advantages of FMCW over pulsed radar: firstly it can detect targets much closer to the vessel, and secondly it also consumes less power.

If you were to analyse this radars transmit frequency on an oscilloscope display as shown above, you would see a sweep through the 'broadband' of frequencies.

The return signal is always at a different frequency to the transmitted signal at any given time.

In the above animation the reflected signal is at a different frequency to the transmitting signal, this is how the FMCW radar can transmit and receive at the same time. It is in fact this difference between frequencies that allows the radar to work out the range of the targets. Watch the video lesson below for a much more detailed look at this.