Synthetic aperture RFID handheld with tag location capability

An RFID (radio frequency identification) reader comprising:

• at least one RFID radio having a first antenna;
• at least one data memory component;
• at least one input/output component configured to prompt a user to move the reader in a first direction;
• and
• at least one processor coupled among the RFID radio, the data memory component, and the input/output component, wherein the processor is configured to:
• transmit a first RF (radio frequency) query using the RFID radio;
• calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna, and wherein the first and second positions correspond to movement of the reader in the first direction;
• calculate a change of phase of the tag signal as a function of time using the first phase and the second phase;
• and
• determine a location of the tag relative to the movement direction of the reader based on the calculated change of phase as a function of time;
• wherein the RFID reader is configured to determine when the RFID reader is in motion, further wherein data from the RFID reader is used to determine the change of phase of the tag as a function of time.

A method of determining a location of an RFID (radio frequency identification) tag relative to an RFID reader, the method comprising:

• prompting the user to move the reader in a first direction;
• using an RFID transceiver having an antenna to send a first RF query;
• calculating a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first location of the first antenna, and
• wherein the second phase corresponds to the tag signal received at a second location of the first antenna, and
• wherein the first and second locations correspond to movement of the reader in the first direction;
• calculating a change of phase of the tag signal as a function of distance traveled by the reader using the first phase and the second phase;
• determining a position of the tag relative to the movement direction of the reader based on the calculated change of phase as a function of time;
• and
• displaying the position of the tag relative to the reader
• emitting sounds, wherein the sounds based upon the change of phase.

An apparatus for determining a location of an RFID (radio frequency identification) tag, the apparatus comprising:

• means for prompting a user to move an RFID reader, where the reader includes a module for determining a location or movement of the reader;
• means for using an RFID transceiver having an antenna to transmit a first RFID interrogation signal;
• means for calculating a first phase and a second phase for a tag signal sent by a tag in response to the first interrogation signal, wherein a first phase corresponds to the tag signal received at a first location of the antenna, and wherein the second phase corresponds to the tag signal received at a second location of the antenna;
• means for calculating a trajectory or locations of the moving reader using data from the module for determining a location or movement of the reader;
• means for determining a location for the tag using the calculated trajectory or positions and the calculated first phase and second phase for the tag.

An RFID (radio frequency identification) reader comprising:

• a location or movement determination component configured to measure location or acceleration of the reader in three dimensions;
• at least one RFID radio having a first antenna;
• at least one data memory component;
• at least one input/output component configured to prompt a user to move the reader;
• and
• at least one processor coupled among the location or movement determination component, the RFID radio, the data memory component, and the input/output component, wherein the processor is configured to:
• transmit a first RF (radio frequency) query using the RFID radio;
• calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna;
• calculate a trajectory or positions of the moving reader using data from the location or movement determination component;
• and
• determine a bearing for the tag using the calculated trajectory or positions and the calculated first phase and second phase for the tag,
• wherein the system determines whether to take more tag signal readings based on whether a minimum level of confidence has been reached, and wherein the RFID radio transmits on a different frequency when the minimum level of confidence is not achieved within a predetermined time period.

An RFID (radio frequency identification) reader comprising:

• at least one RFID radio having a first antenna;
• at least one data memory component;
• at least one input/output component configured to prompt a user to move the reader in a first direction;
• and
• at least one processor coupled among the RFID radio, the data memory component, and the input/output component, wherein the processor is configured to:
• transmit a first RF (radio frequency) query using the RFID radio;
• calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna, and wherein the first and second positions correspond to movement of the reader in the first direction;
• calculate a change of phase of the tag signal as a function of time using the first phase and the second phase;
• and
• determine a location of the tag relative to the movement direction of the reader based on the calculated change of phase as a function of time,
• wherein the input/output component is configured to emit a series of sounds, wherein characteristics of the series of sounds are controlled by the processor, and further wherein the processor is configured to change a period of repetition of the sounds in the series or a frequency of the series of sounds based upon the change of phase.