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Systems, apparatuses, and methods estimate the distance between a player and a ball by transmitting a chirp (sweep signal) to a radio tag located on the ball. During the chirp, the frequency of the transmitted signal is changed in a predetermined fashion. The radio tag doubles the transmitted freque

Systems, apparatuses, and methods estimate the distance between a player and a ball by transmitting a chirp (sweep signal) to a radio tag located on the ball. During the chirp, the frequency of the transmitted signal is changed in a predetermined fashion. The radio tag doubles the transmitted frequency and returns the processed signal to a transceiver typically located on the player. The currently transmitted frequency is then compared with the received frequency to obtain a difference frequency from which an apparatus may estimate the distance. The apparatus may simultaneously receive the processed signal from the radio tag while transmitting the sweep signal.

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1. A system for determining a proximity between a player and a ball in a game, the system comprising: a transceiver located on the player, the transceiver configured to: send a sweep signal to a radio tag, the sweep signal having a sweep frequency changing according to a predetermined pattern;the ra

1. A system for determining a proximity between a player and a ball in a game, the system comprising: a transceiver located on the player, the transceiver configured to: send a sweep signal to a radio tag, the sweep signal having a sweep frequency changing according to a predetermined pattern;the radio tag located on the ball, the radio tag configured to: receive the sweep signal; andgenerate a return signal at a different frequency than the sweep frequency; andthe transceiver further configured to: simultaneously receive the return signal while sending the sweep signal;determine a frequency difference between the return signal and a current frequency of the sweep signal; andapproximate a distance between the player and the ball based on the frequency difference. 2. The system of claim 1, the radio tag comprising a frequency doubler circuit configured to generate the return signal at the different frequency while simultaneously receiving the sweep signal, wherein the different frequency equals twice the sweep frequency. 3. The system of claim 2, the radio tag further comprising: an antenna for receiving at the sweep frequency and for transmitting at twice the sweep frequency. 4. The system of claim 2, the transceiver comprising: a mixer configured to mix the return signal with a second harmonic of the sweep signal. 5. The system of claim 3, the antenna comprising a cross magnetic slotted dipole. 6. The system of claim 4, the transceiver further comprising: a filter having a bandwidth to accommodate a mixer output generated by the mixer. 7. The system of claim 1, the transceiver further configured to: determine when to start the sweep signal to reduce interference by another transceiver, the other transceiver associated with another player. 8. The system of claim 1, the transceiver further configured to: when a variability of measurements of the frequency difference is greater than a predetermined threshold, generating a subsequent sweep signal to approximate the distance between the player and the ball. 9. An apparatus for estimating a distance between a player and a ball, the apparatus located on the player, the apparatus comprising: a radio section configured to: send a sweep signal to a radio tag, the sweep signal having a sweep frequency changing according to a predetermined pattern;simultaneously receive a return signal from a radio tag located on the ball while sending the sweep signal; andobtain a frequency difference between the return signal and a current sweep frequency of the sweep signal; anda processor configured to: approximate the distance between the player and the ball based on the frequency difference. 10. The apparatus of claim 9 further comprising: a mixer configured to mix the return signal with a second harmonic of the sweep signal. 11. The apparatus of claim 10 further comprising: a filter having a bandwidth to accommodate a mixer output generated by the mixer. 12. The apparatus of claim 9, wherein the processor is further configured to: determine when to start the sweep signal to reduce interference by another apparatus, the other apparatus associated with another player. 13. The apparatus of claim 9, wherein the processor is further configured to: determine an estimated distance between the player and the ball from a plurality of measurements of the frequency difference. 14. The apparatus of claim 13, wherein the processor is further configured to: when a variability of the plurality of measurements is greater than a predetermined threshold, generate a subsequent sweep signal to approximate the distance between the player and the ball. 15. A radio tag located on a ball for determining a distance between a player and the ball in a game, the radio tag comprising: an antenna for receiving at a sweep frequency and for transmitting at twice the sweep frequency; anda frequency doubler circuit configured to: receive a sweep signal through the antenna from an apparatus located on the player; andsimultaneously generate a return signal at twice the sweep frequency through the antenna while receiving the sweep signal. 16. The radio tag of claim 15, the antenna comprising a cross magnetic slotted dipole.