Using a Household Fan for Experiments with Doppler Frequency and the I and the Q Part (Video)

A household fan provides a nice low costs target to generate Doppler frequencies.

Some years, our friend, the radar expert Christian Wolff inspired the following exercise.

Exercise Set-up

Place a fan in front of SkyRadar's training radar. Set up you block diagrams with the following objectives:

• Tap the live radar with the signal receiver. Suppress the source with a "Suppress Source"-block.
  Check the suppression of the source with an A-scope (A-Scope 1)
• place on IQ separator block and choose I. Put an A-Scope behind (A-Scope 2).
• place on IQ separator block and choose Q. Put an A-Scope behind (A-Scope 3).
• You can create a matrix through the burst block, put an FFT block behind.
  Also you can put a heatmap behind the burst block

What you will see 

In the A-Scope of the Q-Signal, you will see lots of activities while the radar is starting up and stopping. These activities represent the phase shifts during that acceleration and slowing-down phase.

During full speed, the radar will not recognize the rotation of the fan anymore as it is too fast. It will rather read it as a radar cross section. This is seen in the A-Scopes 1 and 2, as the amplitude of the target "Fan" is reaching its maximum.

In the 3D-Scope and in the heatmap you can see the Doppler frequency.

You can extend the exercise by letting the Fan pan. The panning will add addition motion (a mix of radial and tangential motion). Check in A-Scope 3 the impact on the Q-Signal at both ends of the panning motion (strong radial motion component) and when the radar crosses the radar's line of sight tangentially (rather tangential motion).

Watch the Video

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