Method and system for chopped antenna impedance measurements with an RFID radio

• US 8,135,354 B2
• Filed: 06/02/2009
• Issued: 03/13/2012
• Est. Priority Date: 06/02/2009
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Duron, Mark, Connolly, Sean, Strzelczyk, Martin
• Primary Examiner(s): Nguyen, Duc M
• Application Number:
  US12/476,320
• Publication Number:
  US 20100304684A1
• Time in Patent Office: 1,015 Days
• Field of Search: 455/67.11, 455/226.1, 455/227, 455/228, 455/230, 455/254, 455/289, 455/41.1, 455/41.2, 455/44, 340/10.1, 340/10.3, 340/505
• US Class Current: 455/67.11
• CPC Class Codes: G01R 27/04 in circuits having distributed constants , e.g. having very long conductors or involving high frequencies
• CPC Class Codes: G01R 29/10 Radiation diagrams of antennas
• CPC Class Codes: G01R 31/2822 of microwave or radiofrequency circuits of attenuation, gain, e.g. using network analyzers G01R27/28

Abstract

Described herein are methods, devices and systems for characterizing an attached antenna to an electronic device, such as a radio frequency identification (“RFID”) reader. One exemplary embodiment is related to a method comprising outputting a low amplitude modulation (“AM”) index radio frequency (“RF”) waveform, the waveform simulating tag data timing and bandwidth, removing a direct current (“DC”) component from the waveform to create a chopped portion of the waveform, applying at least one vector analyzer technique on the chopped portion of the waveform, characterizing at least one antenna impedance vector of the waveform.

Claims

1. A method, comprising:

outputting a low amplitude modulation (“

AM”

) index radio frequency (“

RF”

) waveform, the waveform simulating tag data timing and bandwidth;

removing a direct current (“

DC”

) component from the waveform to create a chopped portion of the waveform;

applying at least one vector analyzer technique on the chopped portion of the waveform;

characterizing at least one antenna impedance vector of the waveform.

2. The method according to claim 1, wherein the chopped portion is substantially proportional to an antenna reflection coefficient present at an in-phase and quadrature (“

I/Q”

) demodulator input.

3. The method according to claim 1, further comprising:

providing the chopped portion of the waveform to a composite receiver.

4. The method according to claim 1, further comprising:

determining a polarity sensitive I-channel received signal strength indication (“

RSSI”

) and a polarity sensitive Q-channel RSSI of the waveform.

5. The method according to claim 4, further comprising:

providing the I-channel and the Q-channel RSSIs to one of an echo canceller and a tunable antenna.

6. The method according to claim 1, wherein the outputting step is performed by an RF transmitter.

7. The method according to claim 6, wherein the RF transmitter is a radio frequency identification reader, and the tag-like data is provided from at least one radio frequency identification tag reader.

8. The method according to claim 1, further comprising:

maximizing an S11 measurement demodulated signal to noise ratio (“

SNR”

) using a low level AM modulation index signal source having a modulation rate substantially similar to a data rate of an RFID tag.

9. The method according to claim 1, further comprising:

decreasing a saturation characteristic of an I and Q receiver function demodulation circuitry using a low level AM modulation index signal source to minimize the demodulator non-linearity and third order intermodulation distortion.

10. The method according to claim 1, further comprising:

using a low level AM modulation index signal source derived from a transmitter running at a power output during an S11 measurement, wherein the S11 measurement is taken simultaneously with a tag charging interval of a tag addressing sequence.

11. The method according to claim 1, further comprising:

using a low level AM modulation index signal source derived from a transmitter running at a power output during an S11 measurement at a normal I and Q receiver demodulators, wherein the S11 measurement is continuously taken during an energy charging period of a tag addressing sequence.

12. A communication device, comprising:

a radio frequency (“

RF”

) source outputting a low amplitude modulation (“

AM”

) modulation index radio frequency (“

RF”

) waveform, the waveform simulating tag data timing and bandwidth;

a plurality of direct current (“

DC”

) blocks removing a DC component from the waveform to create a chopped portion of the waveform;

a processor applying at least one vector analyzer technique on the chopped portion of the waveform and characterizing at least one antenna impedance vector of the waveform.

13. The communication device according to claim 12, wherein the chopped portion is substantially proportional to an antenna reflection coefficient.

14. The communication device according to claim 12, wherein the chopped portion of the waveform is provided to a composite receiver.

15. The communication device according to claim 12, wherein the processor further determines a polarity sensitive I-channel received signal strength indication (“

RSSI”

) and a polarity sensitive Q-channel RSSI of the waveform.

16. The communication device according to claim 15, wherein the I-channel and the Q-channel RSSIs are provided to one of an echo canceller and a tunable antenna.

17. The communication device according to claim 12, wherein the RF transmitter is a radio frequency identification reader, and the tag data is provided from at least one radio frequency identification tag.

18. A system, comprising:

a transmitting means for transmitting a low amplitude modulation (“

AM”

) modulation index radio frequency (“

RF”

) waveform, the waveform simulating tag data;

a means for removing a direct current (“

DC”

) component from the waveform to create a chopped portion of the waveform;

an analyzing means for applying at least one vector analyzer technique on the chopped portion of the waveform; and

a characterizing means for characterizing antenna at least one impedance vector of the waveform.

19. The system according to claim 18, wherein the chopped portion is substantially proportional to an antenna reflection coefficient.

20. The system according to claim 18, further comprising:

a providing means for providing the chopped portion of the waveform to a composite receiver.

21. The system according to claim 18, further comprising:

a determining means for determining a polarity sensitive I-channel received signal strength indication (“

RSSI”

) and a polarity sensitive Q-channel RSSI of the waveform.

22. The system according to claim 21, further comprising:

a means for providing the I-channel and the Q-channel RSSIs to one of an echo canceller and a tunable antenna.

23. The system according to claim 18, wherein the transmitting means is an RF transmitter.

24. The system according to claim 23, wherein the RF transmitter is a radio frequency identification reader, and the tag data is provided from at least one radio frequency identification tag.