Method and apparatus for receiving infrared signals with improved noise immunity

• US 6,360,090 B1
• Filed: 08/25/1999
• Issued: 03/19/2002
• Est. Priority Date: 08/26/1998
• Status: Expired due to Fees

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Integration Associates, Inc. (Silicon Laboratories Incorporated)
• Inventors: Holcombe, Wayne T., North, Brian B.
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): West, Lewis G.
• Application Number:
  US09/383,295
• Time in Patent Office: 937 Days
• Field of Search: 455/307, 455/334, 455/338, 455/339, 455/337, 455/296, 379/56.3, 375/317, 348/189, 250/214.AL, 250/214.B, 250/214.C, 250/338.1
• US Class Current: 455/307
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04B 10/114 Indoor or close-range type systems

Abstract

Disclosed is a method and apparatus for receiving infrared signals that is better able to receive a data signal in the presence of a noise signal. The method according to the present invention involves bandwidth filtering an incoming signal that includes a data signal and a noise signal. The bandwidth filtered signal is then averaged to obtain an average alternating current (AC) value signal of the bandwidth filtered signal. The average AC value signal is integrated to obtain a detect level adjustment signal. The detect level adjustment signal is summed with a minimum detect threshold value to obtain a detection level signal. The incoming signal is then compared to the detection level signal in order to produce a received data signal.

Claims

1. A receiver circuit having a receiver input terminal for receiving an incoming signal and a receiver output terminal for outputting a data signal, the receiver comprising:

an detect comparator output circuit having an output terminal coupled to the receiver output terminal, a first input terminal coupled to the receiver input terminal and an second input terminal for receiving a detect threshold signal, where the detect comparator output circuit is configured to compare the incoming signal to the detect threshold signal in order to generate the data signal at the receiver output terminal;

a minimum detect threshold circuit having an output terminal coupled to the second input terminal of the detect comparator output circuit, where the minimum detect threshold circuit it configured to generate a minimum detect threshold level signal at the output terminal;

a noise bandpass filter circuit having an input terminal coupled to the receiver input terminal and an output terminal for outputting a filtered incoming signal, where the noise bandpass filter circuit is configured to pass a predetermined bandwidth corresponding to a noise signal;

a signal averaging circuit having an input terminal coupled to the output terminal of the noise bandpass filter circuit and an output terminal, where the signal averaging circuit is configured to average the filtered incoming signal to produce an averaged signal for output at the output terminal of the signal averaging circuit; and

an integration and scaling circuit having an input terminal coupled to the output terminal of the signal averaging circuit and an output terminal coupled to the second input terminal of the detect comparator output circuit, where the integration and scaling circuit is configured to integrate the averaged signal received from the signal averaging circuit and scale the averaged signal by a predetermined constant in order to generate an adaptive detection threshold signal at the output terminal of the integration and scaling circuit, such that the minimum detect threshold level signal and the adaptive detect threshold signal are summed at the second input terminal of the detect comparator output circuit to produce the detect threshold signal.

2. The receiver circuit of claim 1, where the signal averaging circuit further comprises a full wave rectifier circuit configured to full wave rectify the filtered incoming signal received at the input terminal of the signal averaging circuit in order to generate the averaged signal at the output terminal of the signal averaging circuit.

3. The receiver circuit of claim 2, where the integration and scaling circuit further comprises:

an amplifier having an input terminal coupled to the output terminal of the signal averaging circuit and an output terminal, where the amplifier is configured to amplify the averaged signal received at the input terminal of the integration and scaling circuit by the predetermined constant in order to generate a scaled averaged signal at an output terminal of the amplifier; and

a low pass filter having an input terminal coupled to the output terminal of the amplifier, where the low pass filter is configured to integrate the scaled averaged signal in order to generate the adaptive detection threshold signal at the output terminal of the integration and scaling circuit.

4. The receiver of claim 3, where the noise bandpass filter circuit has an upper cutoff frequency of 200 KHz.

5. The receiver of claim 4, where the predetermined constant is approximately 3.3.

6. The receiver of claim 3, where the detect comparator output circuit further comprises another amplifier having a first input terminal coupled to the receiver input terminal, an output terminal coupled to the receiver output terminal and a second input terminal for receiving the detect threshold signal.

7. The receiver of claim 3, where the detect comparator output circuit further comprises:

a high pass filter having an input terminal coupled to the receiver input terminal and an output terminal;

another amplifier having a first input terminal coupled to the output terminal of the high pass filter, a second input terminal for receiving the detect threshold signal, and an output terminal;

a pulse stretcher circuit having an input terminal coupled to the output terminal of the another amplifier and an output terminal, where the pulse stretcher circuit is configured to produce a stretched pulse at the output terminal of the pulse stretcher circuit by responding rapidly to an edge transition from a first voltage level to a second voltage level at the output terminal of the another amplifier and responding relatively slowly to an edge transition from the second voltage level to the first voltage level at the output terminal of the another amplifier; and

an output buffer having an input terminal coupled to the output terminal of the pulse stretcher and an output terminal coupled to the receiver output terminal.

8. The receiver of claim 7, where the pulse stretcher circuit further comprises:

a resistor having a first terminal coupled to the output terminal of the another amplifier and a second terminal coupled to the input terminal of the output buffer;

a diode having a first terminal coupled to the output terminal of the another amplifier and a second terminal coupled to the input terminal of the output buffer; and

a capacitor having a first terminal coupled to the input terminal of the output buffer and a second terminal coupled to a ground potential contact.

9. The receiver of claim 3, where the detect comparator output circuit further comprises:

a high pass filter having an input terminal coupled to the receiver input terminal and an output terminal;

a first another amplifier having a first input terminal coupled to the receiver input terminal, a second input terminal for receiving the detect threshold signal, and an output terminal;

a second another amplifier having a first input terminal coupled to the output terminal of the high pass filter, a second input terminal for receiving the detect threshold signal, and an output terminal; and

an RS flip-flop having a reset terminal coupled to the output terminal of the first another amplifier, a set terminal coupled to the output terminal of the second another amplifier, and an output terminal coupled to the receiver output terminal.

10. The receiver circuit of claim 1, where the signal averaging circuit further comprises a negative peak detector configured to detect negative peaks of the filtered incoming signal received at the input terminal of the signal averaging circuit in order to generate the averaged signal at the output terminal of the signal averaging circuit.

11. The receiver circuit of claim 10, where the integration and scaling circuit further comprises:

a low pass filter having an input terminal coupled to the input terminal of the integration and scaling circuit, where the low pass filter is configured to integrate the averaged signal in order to generate an integrated averaged signal at an output terminal of the low pass filter; and

an amplifier having an input terminal coupled to the output terminal of the low pass filter, where the amplifier is configured to amplify the integrated averaged signal by the predetermined constant in order to generate the adaptive detection threshold signal at the output terminal of the integration and scaling circuit.

12. The receiver of claim 11, where the noise bandpass filter circuit has an upper cut-off frequency of 200 KHz.

13. The receiver of claim 12, where the predetermined constant is approximately 2.

14. The receiver of claim 11, where the detect comparator output circuit further comprises another amplifier having a first input terminal coupled to the receiver input terminal, an output terminal coupled to the receiver output terminal and a second input terminal for receiving the detect threshold signal.

15. The receiver of claim 11, where the detect comparator output circuit further comprises:

a high pass filter having an input terminal coupled to the receiver input terminal and an output terminal;

another amplifier having a first input terminal coupled to the output terminal of the high pass filter, a second input terminal for receiving the detect threshold signal, and an output terminal;

a pulse stretcher circuit having an input terminal coupled to the output terminal of the another amplifier and an output terminal, where the pulse stretcher circuit is configured to produce a stretched pulse at the output terminal of the pulse stretcher circuit by responding rapidly to an edge transition from a first voltage level to a second voltage level at the output terminal of the another amplifier and responding relatively slowly to an edge transition from the second voltage level to the first voltage level at the output terminal of the another amplifier; and

an output buffer having an input terminal coupled to the output terminal of the pulse stretcher and an output terminal coupled to the receiver output terminal.

16. The receiver of claim 15, where the pulse stretcher circuit further comprises:

a resistor having a first terminal coupled to the output terminal of the another amplifier and a second terminal coupled to the input terminal of the output buffer;

a diode having a first terminal coupled to the output terminal of the another amplifier and a second terminal coupled to the input terminal of the output buffer; and

a capacitor having a first terminal coupled to the input terminal of the output buffer and a second terminal coupled to a ground potential contact.

17. The receiver of claim 11, where the detect comparator output circuit further comprises:

a high pass filter having an input terminal coupled to the receiver input terminal and an output terminal;

a first another amplifier having a first input terminal coupled to the receiver input terminal, a second input terminal for receiving the detect threshold signal, and an output terminal;

a second another amplifier having a first input terminal coupled to the output terminal of the high pass filter, a second input terminal for receiving the detect threshold signal, and an output terminal; and

an RS flip-flop having a reset terminal coupled to the output terminal of the first another amplifier, a set terminal coupled to the output terminal of the second another amplifier, and an output terminal coupled to the receiver output terminal.

18. A method for receiving an incoming signal with improved noise immunity, the method comprising the steps:

bandwidth filtering the incoming signal by passing a predetermined bandwidth corresponding to a noise spectrum;

averaging the filtered incoming signal to obtain an averaged signal;

integrating and scaling the averaged signal to produce an adaptive detect threshold level signal;

summing the adaptive detect threshold level signal with a minimum detect threshold level signal to produce a detect threshold level signal; and

comparing the incoming signal to the detect threshold level signal to produce a data signal.

19. The method of claim 18, where the step of averaging the filtered incoming signal further comprises full wave rectifying the incoming signal to obtain the averaged signal.

20. The method of claim 19, where the step of integrating and scaling the averaged signal further comprises:

amplifying the averaged signal by a predetermined constant; and

low pass filtering the amplified averaged signal to produce the adaptive detect threshold level signal.

21. The method of claim 20, where the step of bandwidth filtering the incoming signal includes filtering out frequencies above 200 KHz.

22. The method of claim 20, where the predetermined constant is 3.3.

23. The method of claim 18, where the step of averaging the filtered incoming signal further comprises detecting the negative peaks of the incoming signal to obtain the averaged signal.

24. The method of claim 23, where the step of integrating and scaling the averaged signal further comprises:

low pass filtering the averaged signal to obtain an integrated averaged signal; and

amplifying the integrated averaged signal by a predetermined constant to produce the adaptive detect threshold level signal.

25. The method of claim 24, where the step of bandwidth filtering the incoming signal includes filtering out frequencies above 200 KHz.

26. The method of claim 24, where the predetermined constant is 2.

27. The method of claim 18, where the step of comparing the incoming signal to the detect threshold level signal further comprises the steps:

high pass filtering the incoming signal;

comparing the high pass filtered incoming signal to the detect threshold level signal to produce a high frequency pulse;

stretching the high speed pulse to produce a slow recovering pulse; and

buffering the slow recovering pulse to produce the data signal.

28. The method of claim 27, where the step of stretching the high speed pulse further comprises:

responding rapidly to an edge transition of the high speed pulse from a first voltage level to a second voltage level to produce a first edge of the slow recovering pulse; and

responding relatively slowly to an edge transition of the high speed pulse from the second voltage level to the first voltage level to produce a second edge of the slow recovering pulse.

29. The method of claim 18, where the step of comparing the incoming signal to the detect threshold level signal further comprises the steps:

high pass filtering the incoming signal;

comparing the incoming signal to the detect threshold level signal to produce a reset signal;

comparing the high pass filtered incoming signal to the detect threshold level signal to produce a set signal;

setting the output signal responsive to the set signal; and

resetting the output signal responsive to the reset signal.