Ball spin rate measurement
First Claim
1. A system for determining a spin rate of a projectile in flight, the system comprising:
- a signal transmitter to transmit a microwave signal toward the projectile in flight;
a signal receiver to receive a reflected signal from the projectile in flight, the reflected signal caused by at least a portion of the microwave signal incident on the projectile in flight;
a signal mixer to mix the received signal with a comparison signal based on the transmitted microwave signal to yield a difference signal;
a demodulator to demodulate the difference signal to generate a demodulated signal comprising at least one periodic component indicating phase variations between the received signal and the comparison signal; and
a frequency analyzer to detect a first periodic component of the demodulated signal, the first periodic component including a first time portion indicating a first apparent speed of the projectile greater than a nominal speed of the projectile, and including a second time portion indicating a second apparent speed of the projectile less than the nominal speed of the projectile, the frequency analyzer to determine a period of the first periodic component, and to determine the spin rate of the projectile in flight based on the period of the first periodic component.
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Accused Products
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.
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Citations
20 Claims
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1. A system for determining a spin rate of a projectile in flight, the system comprising:
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a signal transmitter to transmit a microwave signal toward the projectile in flight; a signal receiver to receive a reflected signal from the projectile in flight, the reflected signal caused by at least a portion of the microwave signal incident on the projectile in flight; a signal mixer to mix the received signal with a comparison signal based on the transmitted microwave signal to yield a difference signal; a demodulator to demodulate the difference signal to generate a demodulated signal comprising at least one periodic component indicating phase variations between the received signal and the comparison signal; and a frequency analyzer to detect a first periodic component of the demodulated signal, the first periodic component including a first time portion indicating a first apparent speed of the projectile greater than a nominal speed of the projectile, and including a second time portion indicating a second apparent speed of the projectile less than the nominal speed of the projectile, the frequency analyzer to determine a period of the first periodic component, and to determine the spin rate of the projectile in flight based on the period of the first periodic component. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of determining a spin rate of a projectile in flight, the method comprising:
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transmitting a microwave signal toward a projectile in flight; receiving a reflected signal from the projectile in flight, the reflected signal being a reflected portion of the microwave signal incident on the projectile in flight; mixing the received signal with a comparison signal based on the transmitted microwave signal to yield a difference signal; demodulating the difference signal to generate a demodulated signal comprising at least one periodic component indicating phase variations between the received signal and the comparison signal; detecting a first periodic component of the demodulated signal, the first periodic component comprising a repeating bipolar pulse having a first portion during which an apparent speed of the projectile is greater than a preceding speed of the projectile, the bipolar pulse having a second portion during which the apparent speed of the projectile is less than the preceding speed of the projectile; determining a period of the first periodic component; and determining the spin rate of the projectile in flight based on the period of the first periodic component. - View Dependent Claims (16, 17)
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18. A system for determining a spin rate of a projectile in flight, the system comprising:
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at least one hardware processor; and a memory including instructions that, when executed by the at least one hardware processor, cause the system to perform operations comprising; receiving a phase-demodulated difference signal of a projectile in flight from a Doppler radar system; detecting a first periodic component of the phase-demodulated signal, the first periodic component comprising a plurality of bipolar pulses, each of the plurality of bipolar pulses having a first portion during which an apparent speed of the projectile is greater than a nominal speed of the projectile between consecutive ones of the bipolar pulses, and each of the plurality of bipolar pulses having a second portion during which the apparent speed of the projectile is less that the nominal speed of the projectile between consecutive ones of the bipolar pulses; determining a period of the first periodic component; and determining the spin rate of the projectile in flight based on the period of the first periodic component. - View Dependent Claims (19, 20)
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Specification