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I recently bought two Doppler Effect sensors HB100, but after reading more about the subject, I found out that these sensors can't distinguish if a target is moving towards or away from them.

I wonder if by using both of them I can work out this information of direction (extract I and Q signals). Like putting them within a specific distance of each other or trying to tune their oscilators.

Has anyone ever used these sensors or even faced a similiar problem?

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  • $\begingroup$ I am not familiar with HB100 but form the spec sheet it appears that it is a simple heterodyne X-band mixer. That being the case if you can assure that you drive the reference LO of the pair of HB100 mixers in quadrature then yes, you should be able to tell from the Doppler shift if the target approaches or recedes by measuring it. But note you must be driving a pair of mixers with the same LO but this HB100 seems to be module of a mixer and an oscillator. So you have to use the 2nd mixer with the LO of the first one, maybe a difficult surgery... $\endgroup$ – hyportnex Nov 9 '16 at 2:34
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One approach you could try is using the two sensors to perform frequency difference of arrival (FDOA). Section IIB of the linked paper discusses the mathematical algorithm, where in the angle to a target can be computed using the doppler shifts of two sensors at known locations.

Because you don't know the sign of the range-rate measured by the sensors, there will be ambiguities, but you may be able to resolve these with prior information (i.e. excluding calculated positions that are physically impossible. For instance, if you know the target is "in front" of the sensors, you can exclude any ghosts that are "behind" them. )

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