User's Manual

What is Broadband radar?
The Navico Broadband radar uses FMCW (Frequency Modulated Continuous Wave) radar
technology.
What is FMCW?
The current normal leisure radar generates microwave pulses with a thermionic device called a
magnetron. This ancient technology transmits bursts of high power microwave energy
periodically, and the radar detector listens to the echoes coming back from each pulse. As the
radar rotates, these echoes are built into a 360 degree image.
FMCW radar is different:
Firstly it is solid state – i.e. the transmitter is a semiconductor device, not based on magnetron
technology. Secondly, it transmits a 1ms long signal of increasing frequency, rather than a short
duration pulse. Thirdly, it measures the distance to a target not by timing the returned echoes,
but by measuring the difference between the current transmitted frequency and echoed
frequency. Hence FMCW – Frequency Modulated Continuous Wave.
The building up of the image over 360 degrees and the processing of the radar data is the same
as for a magnetron radar.
How does FMCW radar work?
FMCW = Frequency Modulated Continuous Wave
The scanner transmits a ‘rising tone’ (Tx wave) with linearly increasing frequency. The wave
propagates out from the transmitter retaining the frequency it had when it was transmitted. If it
reflects off an object, it will return to the receiver, still at the frequency it had when originally
transmitted.
Meanwhile, the transmitter continues to output an increasing frequency.
The difference between both the currently transmitted and received frequencies, coupled with
the known rate of frequency increase, allows a time of flight to be calculated, from which
distance is calculated.
6 | 0BIntroduction to the Navico Broadband radar system