User's Manual

Introduction to the Navico Broadband radar system | 5
What is Broadband radar?
The Navico Broad band 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 sends out 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 thermoinic
valve technology.
Secondly it transmits continuously, not in pulses and thirdly it measures the time of the echo
not by listening to a received pulse but by varying the frequency of the transmitted signal and
detecting the shift in frequency in the received echo. 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 linear 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
2 Introduction to the Navico Broadband radar system
Preliminary