Frequency offset compensation at reflector during frequency compensation interval

A method for communicating between a first radio frequency communications device including a first local oscillator and a second radio frequency communications device including a second local oscillator, the method comprising:

• receiving a packet using a receiver of the first radio frequency communications device;
• detecting an average frequency offset based on sequential samples of the packet;
• and applying a first adjustment to the first local oscillator to reduce a frequency offset between the first local oscillator and the second local oscillator, the first adjustment being based on the average frequency offset;
• after adjusting the first local oscillator, transmitting a second packet to the second radio frequency communications device by the first radio frequency communications device using the first adjustment and the first local oscillator;
• transmitting a first continuous wave tone by the first radio frequency communications device using the first local oscillator and the first adjustment;
• and receiving a second continuous wave tone by the first radio frequency communications device in a zero-intermediate frequency (ZIF) mode of operation using the first local oscillator and the first adjustment.

A radio frequency communications system comprising:

• a first radio frequency communications device comprising:
• a receiver comprising:
• a first local oscillator;
• a detector configured to generate an average frequency offset based on sequential samples of a packet;
• and a digital circuit configured to apply a first adjustment to the first local oscillator to reduce a frequency offset between the first local oscillator and a second local oscillator of a second radio frequency communications device, the first adjustment being based on the average frequency offset, wherein the receiver has a low-intermediate frequency (LIF) mode of operation and a zero-intermediate frequency (ZIF) mode of operation, the packet is received in the LIF mode of operation or the ZIF mode of operation, and each sample of the sequential samples is based on a preamble of the packet or a sync word of the packet.

A method for communicating between a first radio frequency communications device including a first local oscillator and a second radio frequency communications device including a second local oscillator, the method comprising:

• receiving, by the first radio frequency communications device, a request to initiate communications from the second radio frequency communications device;
• receiving a packet by the first radio frequency communications device after the first radio frequency communications device transmits a response to the request;
• applying a first adjustment to the first local oscillator to reduce a frequency offset between the first local oscillator and the second local oscillator, the first adjustment being based on the packet;
• transmitting a second packet to the second radio frequency communications device by the first radio frequency communications device using the first local oscillator and the first adjustment;
• and
• after transmission of the second packet, transmitting a continuous wave tone by the first radio frequency communications device using the first local oscillator and the first adjustment;
• and
• applying a second adjustment to the second local oscillator at the second radio frequency communications device, the second adjustment being based on the continuous wave tone received by the second radio frequency communications device;
• and
• after applying the second adjustment to the second local oscillator:
• generating a first phase measurement of the first local oscillator by the second radio frequency communications device using a second continuous wave tone received by the second radio frequency communications device in a zero-intermediate frequency (ZIF) mode of operation;
• generating a second phase measurement of the second local oscillator by the first radio frequency communications device using a third continuous wave tone received by the first radio frequency communications device in the ZIF mode of operation;
• and
• estimating a distance between the first radio frequency communications device and the second radio frequency communications device based on the first phase measurement and the second phase measurement.