Athletic performance monitoring systems and methods in a team sports environment

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;
• and
• obtain a frequency difference between the return signal and a current sweep frequency of the sweep signal;
• and
• a processor configured to:
• approximate the distance between the player and the ball based on the frequency difference.

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;
• and
• a frequency doubler circuit configured to:
• receive a sweep signal through the antenna from an apparatus located on the player;
• and
• simultaneously generate a return signal at twice the sweep frequency through the antenna while receiving the sweep signal.