Micro-Doppler signatures carry distinctive features of movements of human body parts. Based on micro-Doppler signatures, it is possible to identify movement human body parts. An example of micro-Doppler signature of a human body part is the hand gesture. When fingers and hands are moving in different directions and at different speeds, they can cause different Doppler shifts, shapes, intensities, and durations in radar micro-Doppler signatures. Thus, a hand gesture can be identified from its unique signature.

Figure 1 shows a gesture of Snapping Fingers. When the middle finger is moving from the upper left to stop at the lower right, the angle θMiddle gradually decreases. As a result, the Doppler shift increases. At the same time, the thumb is moving at a velocity from the lower right to stop at the upper left, the angle θThumb gradually increases. Thus, the Doppler frequency shift decreases. The micro-Doppler signature of the snapping fingers indicates that there is a higher negative Doppler peak and a lower positive Doppler peak located at the same time instant. The higher negative Doppler peak corresponds to flipping the middle finger onto the palm and the lower positive Doppler peak corresponds to flipping the thumb forward the radar. Then the three fingers are reset back to their initial positions and there is another low positive Doppler peak appearing as shown in the Figure 1.

Any SDR kit can be used for hand gesture data collections. Especially, C-band SDR-KIT 580AD, X-band SDR-KIT 980AD, and K-band SDR-KIT 2400AD are often used for hand gesture study. With two-channel transmitter and multi-channel receiver SDR-KIT, you can collect hand gesture data of bistatic, monopulse, interferometric and polarimetric radars.

Figure1 – Micro-Doppler signature of a gesture – Snapping Fingers using anSDR kit.

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