Communication processing apparatus and distance measuring method for communication processing apparatus

• US 8,717,227 B2
• Filed: 11/16/2011
• Issued: 05/06/2014
• Est. Priority Date: 03/04/2011
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Nogami, Hidekatsu, Kasai, Hirokazu, Matsui, Shuichi
• Primary Examiner(s): Brainard, Timothy A
• Application Number:
  US13/297,726
• Publication Number:
  US 20120223854A1
• Time in Patent Office: 902 Days
• Field of Search: 342/20, 342 42- 51, 342/127
• US Class Current: 342/82
• CPC Class Codes: G01S 13/82 wherein continuous-type signals are transmitted

Abstract

A communication processing apparatus alternately transmits a carrier wave carrying a command and receives a response from a tag while transmitting an unmodulated carrier wave. A transmission control unit changes the phase of the unmodulated carrier wave transmitted from a transmission/reception circuit in response to start of reception of the reflected wave from the tag. The transmission/reception circuit includes a circuit for separating and detecting an I signal and a Q signal included in the reflected wave from the tag. A phase detection unit uses the I signal and the Q signal to detect change of the phase of the reflected wave. A distance calculation unit measures a time from a change of the phase of the unmodulated carrier wave to a detection of a corresponding change in the phase of the reflected wave, and uses the time to calculate the distance from the antenna to the tag.

Claims

1. A communication processing apparatus that processes and transmits a command to an RFID tag by modulating a carrier wave, receives and processes a reflected wave from the RFID tag in response to an unmodulated carrier wave while transmitting the unmodulated carrier wave, and decodes and processes a response signal of the RFID tag from the received reflected wave, the apparatus comprising:

a phase detector that detects a phase of the reflected wave received in the reception processing;

a phase changer that changes a phase of the unmodulated carrier wave in response to a start of reception of the reflected wave in the reception processing; and

a distance measurer that measures a time from when the phase of the unmodulated carrier wave is changed to a time when a corresponding change occurs in the phase of the reflected wave detected by the phase detector, and that uses the measured time to measure a distance to the RFID tag that returned the reflected wave.

2. The communication processing apparatus according to claim 1, wherein the phase changer changes the phase of the unmodulated carrier wave in response to a detection of a preamble in the response signal in the decoding processing.

3. The communication processing apparatus according to claim 1, wherein the phase changer changes the phase of the unmodulated carrier wave in response to a detection of a preamble in the response signal in the decoding processing, and

the phase detector detects a change of the phase of the reflected wave transmitted while the preamble is being detected.

4. The communication processing apparatus according to claim 1 further comprising:

a determiner that determines whether the RFID tag that returned the reflected wave is appropriate as a target of communication based on the distance measured by the distance measurer.

5. A method of measuring distance by a communication processing apparatus that processes and transmits a command to an RFID tag by modulating a carrier wave, receives and processes a reflected wave from the RFID tag in response to an unmodulated carrier wave while transmitting the unmodulated carrier wave, and decodes and processes a response signal of the RFID tag included in the received reflected wave, the method comprising:

changing a phase of the unmodulated carrier wave in response to a start of reception of the reflected wave in the reception processing; and

while detecting a phase of the reflected wave, measuring a time until a change occurs in the phase of the reflected wave that corresponds to the change of the phase in the unmodulated carrier wave, and using the measured time to measure a distance to the RFID tag that returned the reflected wave.