RECEIVER FOR OBJECT LOCATING AND TRACKING SYSTEMS AND RELATED METHODS

• US 20070248180A1
• Filed: 04/04/2007
• Published: 10/25/2007
• Est. Priority Date: 04/19/2006
• Status: Active Grant

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Wherenet Corporation Corporation of The State of California
• Inventors: Han, Huong M., Bowman, Douglas C.
• Granted Patent: US 8,265,191 B2
• Time in Patent Office: Days
• US Class Current: 375/272
• CPC Class Codes: G01V 15/00 Tags attached to, or associated with, an object, in order to enable detection of the object record carriers for use with machines having a detectable tag or marker G06K19/00

Abstract

A communications system, such as part of a real-time location system, includes a transmitter that can be part of a location processor, tag emission reader or tag interrogator that generates a frequency shift key (FSK) modulated wireless communication signal representative of digital data and transmits the communications signal over a wireless communications channel. A receiver such as incorporated within a tag transceiver used in the real-time location system receives the FSK modulated communication signal. The receiver includes a circuit for calculating the magnitude of low and high tones of the FSK modulated communication signal and a threshold for amplitude shift keyed (ASK) channel data and FSK channel data to derive the digital data even in the presence of on-tone jammers in the communications channel.

Claims

1. A communication system, comprising:

a transmitter that generates a Frequency Shift Key (FSK) modulated wireless communications signal representative of digital data and transmits the communications signal over a wireless communications channel; and

a receiver that receives the FSK modulated communications signal and comprising a circuit for calculating the magnitude of low and high tones of the FSK modulated communications signal and a threshold for Amplitude Shift Keyed (ASK) channel data and FSK channel data to derive the digital data even in the presence of on-tone jammers in the communications channel.

2. A communications system according to claim 1, and further comprising a tag transceiver used in a real-time location system in which said receiver is incorporated.

3. A communications system according to claim 1, wherein said receiver comprises a digital-to-analog (A/D) converter that receives and converts said FSK modulated communications signal into an analog signal.

4. A communications system according to claim 3, wherein said receiver comprises a bandpass filter connected to said A/D converter and operative as an anti-aliasing filter.

5. A communications system according to claim 1, wherein said receiver comprises an Inphase/Quadrature (I/Q) matched filter circuit for processing low and high tones.

6. A communications system according to claim 5, wherein said I/Q matched filter circuit comprises low tone I and Q matched filters and high tone I and Q matched filters.

7. A communications system according to claim 5, wherein said receiver comprises an adder circuit connected to said I/Q matched filter circuit for calculating the magnitude of low and high tones.

8. A communications system according to claim 7, wherein said receiver comprises a compare circuit that receives the result of the adder circuit to generate FSK channel data.

9. A communications system according to claim 7, wherein said receiver comprises a peak-hold and divide circuit that receives data from the adder circuit.

10. A communications system according to claim 1, wherein said receiver comprises an encoder for Manchester encoding the ASK and FSK channel data such that known signal segments are valid when expressed in Manchester periods.

11. A receiver for processing Frequency Shift Key (FSK) modulated communications signals representative of digital data, comprising:

an analog/digital converter that receives the FSK modulated communications signal over a communications channel and converts the communications signal into an analog signal;

an inphase/quadrature (I/Q) matched filter circuit, adder circuit and compare circuit that processes low and high tones from the analog signal converted from the FSK modulated communications signal and calculates the magnitude of low and high tones of the FSK modulated communications signal and a threshold for Amplitude Shift Keyed (ASK) channel data and FSK channel data to derive the digital data even in the presence of on-tone jammers in the communications channel.

12. The receiver according to claim 11, and further comprising a tag transceiver used in real time location systems in which said receiver is incorporated.

13. The receiver according to claim 11, and further comprising an encoder for Manchester encoding the ASK and FSK channel data such that known signal segments are valid when expressed in Manchester periods.

14. The receiver according to claim 11, wherein said I/Q matched filter circuit comprises low tone I and Q matched filters and high tone I and Q matched filters.

15. The receiver according to claim 11, and further comprising a bandpass filter operative as an anti-aliasing filter and connected to said A/D converter.

16. A method for communicating, which comprises:

generating a Frequency Shift Key (PSK) modulated wireless communications signal representative of digital data;

transmitting the communications signal over a wireless communications channel to a receiver; and

calculating at the receiver the magnitude of low and high tones of the FSK modulated communications signal and a threshold for Amplitude Shift Keyed (ASK) channel data and FSK channel data to derive the digital data even in the presence of on-tone jammers in the communications channel.

17. The method according to claim 16, which further comprises converting the received FSK modulated communications signal into an analog signal.

18. The method according to claim 17, which further comprises bandpass filtering the analog signal.

19. The method according to claim 16, which further comprises processing high and low tones at the receiver within an Inphase/Quadrature (I/Q) matched filter circuit.

20. The method according to claim 16, which further comprises calculating the magnitude of low and high tones within an adder circuit.

21. The method according to claim 20, which further comprises comparing the results from the adder circuit to generate FSK channel data.

22. The method according to claim 16, which further comprises Manchester encoding ASK and PSK channel data such that known signal segments are valid when expressed in Manchester periods.

23. A method according to claim 16, which further comprises locating the receiver within a real-time location system.

24. A method according to claim 23, which further comprises incorporating the receiver into a tag transceiver.