Synchronization of receiver and transmitter local oscillators for ranging applications

A method of performing a distance measurement between a first network device and a second network device, comprising:

• transmitting a first packet from the first network device to the second network device, using a first frequency;
• replying to the first packet by transmitting a second packet from the second network device to the first network device using the first frequency;
• transmitting a third packet from the first network device to the second network device using a second frequency, different from the first frequency;
• replying to the third packet by transmitting a fourth packet from the second network device to the first network device using the second frequency;
• and
• calculating a distance based on a phase received by the first network device and the second network device for each packet, the first frequency and the second frequency,
• wherein the first network device and the second network device each comprise a clock generation circuit to generate a receive clock and a transmit clock, wherein a phase difference between the transmit clock and the receive clock of each network device is constant.

A clock generation circuit comprising:

• a receive clock generation circuit;
• a transmit clock generation circuit;
• and
• a signal source to provide a REFCLK signal;
• wherein the receive clock generation circuit and the transmit clock generation circuit each comprise:
• a phase locked loop, comprising:
• a detector to determine a difference between the REFCLK signal and a feedback signal and provide an output based on the difference;
• a loop filter to filter the output to create a filtered output;
• an oscillator to generate a clock signal with a frequency related to the filtered output;
• a divider to divide the clock signal by a quantity;
• and
• a multi-modulus divider in communication with an output of the divider, to further divide the output of the divider by an integer and supply the feedback signal to the detector;
• wherein the divider comprises a reset signal so as to be initialized to a known state;
• wherein the transmit clock is generated based on the output of the divider in the transmit clock generation circuit and the receive clock is generated based on the output of the divider in the receive clock generation circuit, and wherein a phase difference between the transmit clock and the receive clock is constant.