Automatic adapt circuit for circumventing demodulator transients in radio receiver

• US 6,356,749 B1
• Filed: 06/24/1999
• Issued: 03/12/2002
• Est. Priority Date: 11/04/1998
• Status: Expired due to Term

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Wong, Man Wa, Rollins, Norman T., Hoggarth, Steven P.
• Primary Examiner(s): Hunter, Daniel
• Assistant Examiner(s): ZEWDU, MELESS NMN
• Application Number:
  US09/344,192
• Time in Patent Office: 992 Days
• Field of Search: 455/296, 455/312, 455/307, 455/218, 455/219, 455/214, 455/324, 455/337, 455/340, 329/300, 329/304, 329/311, 329/318, 329/319, 329/345, 329/349, 329/351, 375/316, 375/317, 375/318, 375/319
• US Class Current: 455/334
• CPC Class Codes: H04B 1/28 the receiver comprising at least one semiconductor device having three or more electrodes

Abstract

An auto-adapt circuit (200) for altering radio receiver parameters due to demodulator transients and preventing the loss of received information. The auto-adapt circuit includes a detector circuit (215) connected to the output of a receiver demodulator (203) and a switch (219) controlled by the detector circuit (215). The detector circuit (215) detects a transient voltage at an upper threshold limit or at a lower threshold limit such that a transient at an output of the receiver demodulator will actuate the at least one switch for varying demodulator coupling parameters of the radio receiver.

Claims

1. An auto-adapt circuit for altering radio receiver parameters due to demodulator transients and preventing the loss of received information comprising:

at least one detector circuit connected to the output of a receiver demodulator;

at least one switch controlled by the detector circuit; and

wherein the at least one detector circuit detects a DC offset shift at an upper threshold limit or at a lower threshold limit such that the DC offset shift at an output of the receiver demodulator will actuate the at least one switch for varying dimodulator coupling parameters of the radio receiver.

2. An auto-adapt circuit as in claim 1, wherein coupling parameters of the at least one demodulator circuit are varied by changing a resister-capacitor (RC) time constant.

3. An auto-adapt circuit as in claim 1, wherein the at least one detector circuit includes at least one comparator.

4. An auto-adapt circuit as in claim 3, wherein the at least one comparator is a digital comparator.

5. An auto-adapt circuit as in claim 1, wherein the at least one detector circuit includes a first and second comparator circuit for setting the upper and lower threshold limit and an or gate for providing an actuating signal to the at least one switch.

6. An auto-adapt circuit as in claim 1, wherein at least one filter is positioned between the demodulator and the at least one detector circuit for providing a desired frequency response.

7. An auto-adapt circuit as in claim 1, wherein the at least one detector circuit is in parallel with a center slicer for converting analog data to a digital bit stream.

8. An auto-adapt circuit as in claim 7, further comprising a decoder attached to the output of the center slicer for decoding information from the digital bit stream.

9. A radio receiver system including an adaptive circuit for detecting and responding to the presence of a DC offset shift at the output of a demodulator comprising:

a demodulator circuit for receiving detected information;

at least one filtering circuit for receiving demodulated information;

at least one center slicer for converting the filtered information into a digital bit stream;

a decoder circuit for decoding data within the digital bit stream;

at least one detector circuit receiving information from the at least one filtering circuit for detecting a DC offset shift such that the signal crosses either above or below predetermined thresholds; and

at least one switch circuit responsive to the at least one detector for altering a receiver attack time and preventing loss of received information due to receiver DC offset shift.

10. A radio receiver system as in claim 9, wherein the receiver attack time is altered by varying an resistor-capacitor (RC) time constant in a coupling circuit.

11. A radio receiver system as in claim 10, wherein the coupling circuit couples the demodulator circuit and the at least one filtering circuit.

12. A radio receiver system as in claim 10, wherein the at least one detector circuit is comprised of at least one comparator for comparing the upper and lower signal threshold levels and actuating the at least one switch.

13. A method for automatically adapting a radio receiver to circumvent demodulator DC offset shift comprising the steps of:

providing a demodulated output signal from a demodulator circuit;

alternating current (AC) coupling the demodulator output signal to a center slicer circuit;

monitoring the output of the demodulated output signal to detect the presence of a DC offset shift;

detecting a DC offset shift beyond an upper voltage limit or lower voltage limit; and

altering an resistor capacitor (RC) time constant of the AC coupled signal to provide a substantially rapid decay time of the DC offset for preventing loss of received information.

14. A method for automatically adapting a radio receiver as in claim 13, wherein the DC offset shift is detected using at least one comparator for comparing the signal against an upper and lower DC voltage limit.

15. A method for automatically adapting a radio receiver as in claim 14, wherein the at least one comparator is a digital comparator.

16. A method for automatically adapting a radio receiver as in claim 13, wherein the RC time constant is switched.

17. A method for automatically adapting a radio receiver as in claim 13, further comprising the step of:

filtering the demodulator output signal for providing a tailored frequency response to the center slicer circuit.

18. A method for automatically adapting a radio receiver as in claim 13, further comprising the step of:

decoding the output of the center slicer circuit for providing decoded information.