RFID decoding subsystem with pre-decode module

• US 20080065957A1
• Filed: 07/20/2006
• Published: 03/13/2008
• Est. Priority Date: 07/20/2006
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Rofougaran, Ahmadreza (Reza), Shoarinejad, Kambiz
• Granted Patent: US 7,734,994 B2
• Time in Patent Office: Days
• US Class Current: 714/758
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

A radio frequency identification (RFID) decoding subsystem includes a pre-decode module and a decode module. The pre-decode module is coupled to process down-converted RFID signals into at least one of pre-decoded baseband data and corresponding decoding information. The decode module is coupled to process the pre-decoded baseband data into decoded RFID data, where the processing of the pre-decoded baseband data is based on the corresponding decoding information when the corresponding decoding information is produced by the pre-decoder module.

Claims

1. A radio frequency identification (RFID) decoding subsystem comprises:

pre-decode module coupled to process down-converted RFID signals into at least one of pre-decoded baseband data and corresponding decoding information; and

decode module coupled to process the pre-decoded baseband data into decoded RFID data, wherein the processing of the pre-decoded baseband data is based on the corresponding decoding information when the corresponding decoding information is produced by the pre-decoder module.

2. The RFID decoding subsystem of claim 1, wherein the pre-decode module comprises at least one of:

an in-phase filter coupled to filter in-phase components of the down-converted RFID signals to produce filtered in-phase component signals;

a quadrature filter coupled to filter quadrature components of the down-converted RFID signals to produce filtered quadrature component signals;

amplitude estimation module coupled to estimate amplitude of the down-converted RFID signals based on the filtered in-phase and quadrature component signals to produce an estimated amplitude; and

a limiting module coupled to produce the pre-decoded baseband data based on the estimated amplitude.

3. The RFID decoding subsystem of claim 2, wherein the amplitude estimation module performs at least one of:

√

{square root over (I²+Q²)},

wherein I represents amplitude of the in-phase component signals and Q represents amplitude of the quadrature component signals; and

max(|I|,|Q|)+0.5*min(|I|,|Q|)

4. The RFID decoding subsystem of claim 1, wherein the pre-decode module comprises at least one of:

an in-phase filter coupled to filter in-phase components of the down-converted RFID signals to produce filtered in-phase component signals;

a quadrature filter coupled to filter quadrature components of the down-converted RFID signals to produce filtered quadrature component signals;

an in-phase received signal strength indication (RSSI) module coupled to determine signal strength of the filtered in-phase components;

a quadrature RSSI module coupled to determine signal strength of the filtered quadrature components;

an in-phase limiting module coupled to limit the filtered in-phase component signals to produce limited in-phase component signals;

a quadrature limiting module coupled to limit the filtered quadrature component signals to produce limited quadrature component signals; and

selection module coupled to select the limited in-phase quadrature component signals or the limited quadrature component signals as the pre-decoded baseband data based on at least one of the signal strength of the filtered in-phase components and the signal strength of the filtered quadrature components.

5. The RFID decoding subsystem of claim 1, wherein the pre-decode module comprises at least one of:

an in-phase filter coupled to filter in-phase components of the down-converted RFID signals to produce filtered in-phase component signals;

a quadrature filter coupled to filter quadrature components of the down-converted RFID signals to produce filtered quadrature component signals;

an in-phase received signal strength indication (RSSI) module coupled to determine signal strength of the filtered in-phase components;

a quadrature RSSI module coupled to determined signal strength of the filtered quadrature components;

an in-phase limiting module coupled to limit the filtered in-phase component signals to produce limited in-phase component signals;

a quadrature limiting module coupled to limit the filtered quadrature component signals to produce limited quadrature component signals, wherein the pre-decoded baseband data includes at least one of the limited in-phase component signals and the limited quadrature component signals, and wherein the corresponding decoding information includes at least one of the signal strength of the filtered quadrature components and the signal strength of the filtered in-phase components.

6. The RFID decoding subsystem of claim 5, wherein the decode module processes the pre-decoded baseband data by:

decoding the limited in-phase component signals to produce decoded in-phase RFID data;

decoding the limited quadrature component signals to produce decoded quadrature RFID data; and

selecting the decoded in-phase RFID data or the decoded quadrature RFID data as the decoded RFID data based on the least one of the signal strength of the filtered quadrature components and the signal strength of the filtered in-phase components.

7. The RFID decoding subsystem of claim 1, wherein the pre-decode module comprises at least one of:

an in-phase filter coupled to filter in-phase components of the down-converted RFID signals to produce filtered in-phase component signals;

a quadrature filter coupled to filter quadrature components of the down-converted RFID signals to produce filtered quadrature component signals;

an in-phase received signal strength indication (RSSI) module coupled to produce an in-phase weighting factor in accordance with signal strength of the filtered in-phase components;

a quadrature RSSI module coupled to produce a quadrature weighting factor in accordance with signal strength of the filtered quadrature components;

an in-phase limiting module coupled to limit the filtered in-phase component signals to produce limited in-phase component signals;

a quadrature limiting module coupled to limit the filtered quadrature component signals to produce limited quadrature component signals;

an in-phase counting module coupled count transitions of the limited in-phase component signals to produce an in-phase count;

a quadrature counting module coupled count transitions of the limited quadrature component signals to produce a quadrature count; and

a weighting module coupled to weight the in-phase count based on the in-phase weighting factor and to weight the quadrature count based on the quadrature weighting factor to produce the pre-decoded baseband data.

8. The RFID decoding subsystem of claim 1, wherein the pre-decode module comprises at least one of:

an in-phase filter coupled to filter in-phase components of the down-converted RFID signals to produce filtered in-phase component signals;

a quadrature filter coupled to filter quadrature components of the down-converted RFID signals to produce filtered quadrature component signals;

multiplexer coupled to provide the filtered in-phase component signals as the pre-decoded baseband data when a selection signal is in a first state and to provide the filtered quadrature component signals as the pre-decoded baseband data when the selection signal is in a second state, wherein one of the first and second states of the selection signal corresponds to an errorless cyclic redundancy check (CRC) of the decoded RFID data and another of the first and second states of the select signal corresponds to an error of the CRC of the decoded RFID data.

9. The RFID decoding subsystem of claim 1, wherein the pre-decode module comprises:

a limiter coupled to limit the down-converted RFID signals to produce limited RFID signals, wherein the decoded RFID data corresponds to four-interval bit cell encoded data; and

frequency divider module coupled to reduce transition frequency of the limited RFID signals to correspond to a rate of one of;

FM0 and FM1 data.

10. The RFID decoding subsystem of claim 1, wherein the pre-decode module comprises:

a processing module coupled to process the down-converted RFID signals into at least one of pre-decoded baseband data and corresponding decoding information in accordance with one of a plurality of pre-decoding processes, wherein the one of the plurality of pre-decoding processes is selected in accordance with a pre-decoding selection signal.

11. The RFID decoding subsystem of claim 10, wherein the processing module further functions to:

interpret at least one of a preamble of the down-converted RFID signals or system setup information to establish a state for the pre-decoding selection signal.

12. The RFID decoding subsystem of claim 1, wherein the pre-decode module comprises:

a digital down converter to down convert to intermediate frequency RFID signals into baseband RFID signals, wherein the baseband RFID signals corresponds to the down-converted RFID signals.

13. A radio frequency identification (RFID) reader receiver comprises:

a low noise amplifier coupled to amplify an inbound RF signal to produce an amplified inbound RF signal;

a block cancellation module coupled to receive an outbound RF signal from an RFID transmitter and to substantially cancel a blocking signal from the amplified inbound RF signal using the outbound RF signal and substantially pass a modulated RF signal;

a down-conversion module coupled to convert the modulated RF signal to down-converted RFID signals;

pre-decode module coupled to process down-converted RFID signals into at least one of pre-decoded baseband data and corresponding decoding information; and

decode module coupled to process the pre-decoded baseband data into decoded RFID data, wherein the processing of the pre-decoded baseband data is based on the corresponding decoding information when the corresponding decoding information is produced by the pre-decoder module.

14. The RFID reader receiver of claim 13, wherein the pre-decode module comprises at least one of:

an in-phase filter coupled to filter in-phase components of the down-converted RFID signals to produce filtered in-phase component signals;

a quadrature filter coupled to filter quadrature components of the down-converted RFID signals to produce filtered quadrature component signals;

amplitude estimation module coupled to estimate amplitude of the down-converted RFID signals based on the filtered in-phase and quadrature component signals to produce an estimated amplitude; and

a limiting module coupled to produce the pre-decoded baseband data based on the estimated amplitude.

15. The RFID reader receiver of claim 14, wherein the amplitude estimation module performs at least one of:

√

{square root over (I²+Q²)},

I represents amplitude of the in-phase component signals and Q represents amplitude of the quadrature component signals; and

max(|I|,|Q|)+0.5*min(|I|,|Q|)

16. The RFID reader receiver of claim 13, wherein the pre-decode module comprises at least one of:

an in-phase filter coupled to filter in-phase components of the down-converted RFID signals to produce filtered in-phase component signals;

a quadrature filter coupled to filter quadrature components of the down-converted RFID signals to produce filtered quadrature component signals;

an in-phase received signal strength indication (RSSI) module coupled to determine signal strength of the filtered in-phase components;

a quadrature RSSI module coupled to determined signal strength of the filtered quadrature components;

an in-phase limiting module coupled to limit the filtered in-phase component signals to produce limited in-phase component signals;

a quadrature limiting module coupled to limit the filtered quadrature component signals to produce limited quadrature component signals; and

selection module coupled to select the limited in-phase quadrature component signals or the limited quadrature component signals as the pre-decoded baseband data based on at least one of the signal strength of the filtered in-phase components and the signal strength of the filtered quadrature components.

17. The RFID reader receiver of claim 13, wherein the pre-decode module comprises at least one of:

an in-phase filter coupled to filter in-phase components of the down-converted RFID signals to produce filtered in-phase component signals;

a quadrature filter coupled to filter quadrature components of the down-converted RFID signals to produce filtered quadrature component signals;

an in-phase received signal strength indication (RSSI) module coupled to determine signal strength of the filtered in-phase components;

a quadrature RSSI module coupled to determined signal strength of the filtered quadrature components;

an in-phase limiting module coupled to limit the filtered in-phase component signals to produce limited in-phase component signals;

a quadrature limiting module coupled to limit the filtered quadrature component signals to produce limited quadrature component signals, wherein the pre-decoded baseband data includes at least one of the limited in-phase component signals and the limited quadrature component signals, and wherein the corresponding decoding information includes at least one of the signal strength of the filtered quadrature components and the signal strength of the filtered in-phase components.

18. The RFID reader receiver of claim 17, wherein the decode module processes the pre-decoded baseband data by:

decoding the limited in-phase component signals to produce decoded in-phase RFID data;

decoding the limited quadrature component signals to produce decoded quadrature RFID data; and

selecting the decoded in-phase RFID data or the decoded quadrature RFID data as the decoded RFID data based on the least one of the signal strength of the filtered quadrature components and the signal strength of the filtered in-phase components.

19. The RFID reader receiver of claim 13, wherein the pre-decode module comprises at least one of:

an in-phase filter coupled to filter in-phase components of the down-converted RFID signals to produce filtered in-phase component signals;

a quadrature filter coupled to filter quadrature components of the down-converted RFID signals to produce filtered quadrature component signals;

an in-phase received signal strength indication (RSSI) module coupled to produce an in-phase weighting factor in accordance with signal strength of the filtered in-phase components;

a quadrature RSSI module coupled to produce a quadrature weighting factor in accordance with signal strength of the filtered quadrature components;

an in-phase limiting module coupled to limit the filtered in-phase component signals to produce limited in-phase component signals;

a quadrature limiting module coupled to limit the filtered quadrature component signals to produce limited quadrature component signals;

an in-phase counting module coupled count transitions of the limited in-phase component signals to produce an in-phase count;

a quadrature counting module coupled count transitions of the limited quadrature component signals to produce a quadrature count; and

a weighting module coupled to weight the in-phase count based on the in-phase weighting factor and to weight the quadrature count based on the quadrature weighting factor to produce the pre-decoded baseband data.

20. The RFID reader receiver of claim 13, wherein the pre-decode module comprises at least one of:

an in-phase filter coupled to filter in-phase components of the down-converted RFID signals to produce filtered in-phase component signals;

a quadrature filter coupled to filter quadrature components of the down-converted RFID signals to produce filtered quadrature component signals;

multiplexer coupled to provide the filtered in-phase component signals as the pre-decoded baseband data when a selection signal is in a first state and to provide the filtered quadrature component signals as the pre-decoded baseband data when the selection signal is in a second state, wherein one of the first and second states of the selection signal corresponds to an errorless cyclic redundancy check (CRC) of the decoded RFID data and another of the first and second states of the select signal corresponds to an error of the CRC of the decoded RFID data.

21. The RFID reader receiver of claim 13, wherein the pre-decode module comprises:

a limiter coupled to limit the down-converted RFID signals to produce limited RFID signals, wherein the decoded RFID data corresponds to four-interval bit cell encoded data; and

frequency divider module coupled to reduce transition frequency of the limited RFID signals to correspond to a rate of one of;

FM0 and FM1 data.

22. The RFID reader receiver of claim 13, wherein the pre-decode module comprises:

a processing module coupled to process the down-converted RFID signals into at least one of pre-decoded baseband data and corresponding decoding information in accordance with one of a plurality of pre-decoding processes, wherein the one of the plurality of pre-decoding processes is selected in accordance with a pre-decoding selection signal.

23. The RFID reader receiver of claim 22, wherein the processing module further functions to:

interpret at least one of a preamble of the down-converted RFID signals or system setup information to establish a state for the pre-decoding selection signal.

24. The RFID reader receiver of claim 13, wherein the pre-decode module comprises:

a digital down converter to down convert to intermediate frequency RFID signals into baseband RFID signals, wherein the baseband RFID signals corresponds to the down-converted RFID signals.