Communication device
A wireless tag that is not guaranteed to be located within a predetermined area is prevented from being read as a valid wireless tag. A communication device includes: an antenna; a reference tag; a reception unit; and a determination unit. The reception unit uses the antenna to sequentially receive signals wirelessly transmitted from a reference tag whose relative position to the antenna is known and a reading target tag different from the reference tag. The determination unit determines that the signal transmitted from the reading target tag and received by the reception unit is invalid based on a phase of the signal transmitted from the reference tag and received by the reception unit.
1. A commodity registration system comprising:
a reference tag configured to couple to or embed in a table or surface;
an antenna;
an actuator configured to reposition the antenna between a first position underneath the table or surface and a second position underneath the table or surface; and
a control system configured to:
use the antenna to acquire (i) one or more reference signals wirelessly transmitted from the reference tag whose relative position to the antenna is known and (ii) one or more target signals wirelessly transmitted from a target tag attached to a commodity for purchase that is placed on or proximate the table or surface, the target tag different from the reference tag, wherein the one or more reference signals include a first reference signal acquired by the antenna at the first position and a second reference signal acquired by the antenna at the second position, and wherein the one or more target signals include a first target signal acquired by the antenna at the first position and a second target signal acquired by the antenna at the second position;
determine that the one or more target signals transmitted from the target tag are invalid based on a phase characteristic of the one or more reference signals transmitted from the reference tag, wherein the phase characteristic of the one or more reference signals is a threshold phase difference determined based on a reference phase difference between the first reference signal and the second reference signal;
determine a target phase difference between the first target signal and the second target signal;
register the commodity for purchase in response to the target phase difference being less than the reference phase difference; and
refrain from registering the commodity for purchase in response to the target phase difference being greater than the threshold phase difference.
2. The commodity registration system of claim 1 , wherein the actuator includes a motor, an output shaft coupled to the motor, a rail coupled to the output shaft, and a stage coupled to the rail, wherein the antenna is coupled to the stage, and wherein the motor is configured to drive the output shaft to cause the antenna to translate relative to the reference tag along the rail between the first position and the second position.
3. The commodity registration system of claim 1 , wherein the reference tag is positioned closer to the first position than the second position.
4. The commodity registration system of claim 1 , wherein the control system is configured to issue an alarm in response to the threshold phase difference being outside of a preset range.
5. A commodity registration system comprising:
an antenna;
an actuator configured to reposition the antenna between a first position and a second position; and
a control system configured to:
use the antenna to acquire one or more reference signals wirelessly transmitted from a reference tag whose relative position to the antenna is known, the one or more reference signals including a first reference signal acquired by the antenna at the first position and a second reference signal acquired by the antenna at the second position;
use the antenna to acquire one or more target signals wirelessly transmitted from a target tag coupled to a commodity and different from the reference tag, the one or more target signals including a first target signal acquired by the antenna at the first position and a second target signal acquired by the antenna at the second position;
determine a reference phase difference between the first reference signal and the second reference signal;
determine a target phase difference between the first target signal and the second target signal;
register the commodity for purchase in response to the target phase difference being less than the reference phase difference; and
refrain from registering the commodity for purchase in response to the target phase difference being greater than the reference phase difference.
6. A commodity registration system comprising:
an antenna;
an actuator configured to reposition the antenna between a first position and a second position; and
a control system configured to:
use the antenna to acquire one or more reference signals wirelessly transmitted from a reference tag whose relative position to the antenna is known, the one or more reference signals including a plurality of reference signals acquired by the antenna at a plurality of positions between the first position and the second position;
use the antenna to acquire one or more target signals wirelessly transmitted from a target tag coupled to a commodity and different from the reference tag, the one or more target signals include a plurality of target signals acquired by the antenna at a plurality of positions between the first position and the second position; and
determine a reference phase change curve between the first position and the second position based on a phase of each of the plurality of reference signals acquired between the first position and the second position;
determine a target phase change curve between the first position and the second position based on a phase of each of the plurality of target signals acquired at a plurality of positions between the first position and the second position;
register the commodity for purchase in response to a curvature of the target phase change curve being gentler than a curvature of the reference phase change curve; and
refrain from registering the commodity for purchase in response to the curvature of the target phase change curve being more abrupt than the curvature of the reference phase change curve.