I’m working on a problem where I have to build a speed detector using a hardware circuit with a microcontroller. I will be using a radar motion detector module to do this. I have contacted the manufacturer B+B sensors for information regarding the application circuits with no reply as yet (https://shop.bb-sensors.com/out/media/Datasheet_RADAR-IPM-165_DBE_Rev01.pdf)

I’m looking for some advice to determine which filter to implement to ‘clean’ the received frequency. Does anyone have any ideas on how I could go about this? The received frequency will be in the GHz range I imagine due to the operating frequency being 24GHz.

  • 2
    \$\begingroup\$ Read the data shet: Application circuits for this are available on request. \$\endgroup\$ – Andy aka Feb 1 '18 at 17:27
  • \$\begingroup\$ I'm voting to close this question as off-topic because there is no evidence that the OP has read the data sheet. \$\endgroup\$ – Andy aka Feb 1 '18 at 17:27
  • \$\begingroup\$ @Andyaka I’ve contacted the seller with no reply hence why I’m asking for help here \$\endgroup\$ – Jandy12 Feb 1 '18 at 17:28
  • \$\begingroup\$ @Andyaka I’ve literally quoted the data sheet regarding the 24GHz transmitted signal \$\endgroup\$ – Jandy12 Feb 1 '18 at 17:30
  • \$\begingroup\$ Perhaps you could hose this module output to a PC's microphone input, and use waveform analysis tools to see what filtering is suitable. \$\endgroup\$ – glen_geek Feb 1 '18 at 17:41

The datasheet says,

...the frequency of signal originating at the mixer output is proportional to the speed: 44 Hz corresponding to a movement speed of approx. 1 km/h.

This implies that

  1. There is demodulation implemented in the module (by the "mixer" that was mentioned)

  2. The signal delivered to you is somewhere in the DC to kHz range.

The only filtering you would want to do is low-pass filtering, with a cut-off frequency determined by the highest speed target you need to detect. You might do band-pass filtering instead if you don't need to detect a stationary or near-stationary target.

In any case, 24 GHz through that 3-pin 2.54-mm electrical interface would be absurd.

  • \$\begingroup\$ Thank you so much for your help that’s exactly what I’ve needed \$\endgroup\$ – Jandy12 Feb 1 '18 at 17:47

Did you get the version with the integrated amplifier? If not, you need to have an amplifier at the output pin "with defined bandwidth (approx. 20 ... 900 Hz)" and a gain that will bring the 300µV signal to the level required by whatever ADC input you're using.

Those are pretty simple requirements for an amplifier.

  • \$\begingroup\$ I’ve created an amplifier by cascading two opamps, I’ve managed to get a gain of 11k to get an output of ~3.3V \$\endgroup\$ – Jandy12 Feb 1 '18 at 17:48
  • \$\begingroup\$ @Jandy12 Sounds like you're set then. \$\endgroup\$ – Samuel Feb 1 '18 at 17:59

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