Abstract: Systems and methods for ball spin rate measurement are described. Some embodiments provide a method whereby a phase-demodulated difference signal of a projectile in flight is received, such as from a Doppler radar system. A first periodic component of the phase-demodulated signal is detected, the first periodic component having a plurality of bipolar pulses, with each of the pulses having a first portion during which an apparent speed of the projectile is greater than a nominal speed of the projectile, and each of the pulses having a second portion during which the apparent speed of the projectile is less that the nominal speed of the projectile. A period of the first periodic component is detected, and the spin rate of the projectile in flight is determined based on the period of the first periodic component.

Abstract: Systems and methods for ball spin rate measurement are described. Some embodiments provide a method whereby a phase-demodulated difference signal of a projectile in flight is received, such as from a Doppler radar system. A first periodic component of the phase-demodulated signal is detected, the first periodic component having a plurality of bipolar pulses, with each of the pulses having a first portion during which an apparent speed of the projectile is greater than a nominal speed of the projectile, and each of the pulses having a second portion during which the apparent speed of the projectile is less that the nominal speed of the projectile. A period of the first periodic component is detected, and the spin rate of the projectile in flight is determined based on the period of the first periodic component.

Abstract: Spin rate measurement utilizing periodic phase modulation of the radar Doppler signal reflected from a golf ball is described. Some embodiments provide a method to directly measure the ball spin rate caused by the symmetrical structure of the golf ball seam, using the dielectric lens effect of a practical sports ball to magnify the modulating effect of a non-homogeneous feature on the ball, and utilizing the specific pattern of modulation caused in this manner.