Combined discrete automatic gain control (AGC) and DC estimation

• US 6,654,593 B1
• Filed: 10/30/2000
• Issued: 11/25/2003
• Est. Priority Date: 10/30/2000
• Status: Expired due to Fees

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Blackberry Limited
• Inventors: Simmons, Sean, Kemenczy, Zoltan, Dajani, Muhammad
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US09/699,794
• Time in Patent Office: 1,121 Days
• Field of Search: 455/234.1, 455/234.2, 455/245.1, 455/246.1, 455/250.1, 455/296, 455/303, 455/309, 455/310, 455/312, 455/317, 455/324, 375/345
• US Class Current: 455/234.1
• CPC Class Codes: H03D 7/00 Transference of modulation from one carrier to another, e.g. frequency-changing H03D9/00, H03D11/00 take precedence; dielectric amplifiers, magnetic amplifiers, parametric amplifiers used as a frequency-changers H03F
• CPC Class Codes: H03G 3/001 Digital control of analog signals
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04L 25/06 Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
• CPC Class Codes: H04L 27/3809 Amplitude regulation arrangements
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

An automatic gain control (AGC) and DC estimation and correction technique for wireless communication devices is provided. An AGC signal, which controls a gain applied to a received signal by a gain stage to generate a scaled signal, is assigned one of a relatively small number of values in accordance with the amplitude of the scaled signal. An estimate of a DC offset in the scaled signal corresponding to each value of the AGC signal is stored in a memory. A DC estimation arrangement then reads the stored estimate associated with the particular value of the AGC signal from the memory and generates a current DC estimate based thereon. The current estimate is then used to correct the scaled signal for DC offset and to update the stored estimate.

Claims

1. A wireless communications receiver, comprising:

(a) means for applying a gain to a received signal, responsive to an automatic gain control (AGC) signal, to produce a scaled signal;

(b) AGC means for determining amplitude of the scaled signal and generating the AGC signal; and

(c) means for estimating a DC offset of the scaled signal comprising an exponential filter the state of which is set using a previously stored DC offset estimate read from a memory means.

2. A wireless receiver according to claim 1, wherein the AGC signal has a finite number of possible values.

3. A wireless receiver according to claim 2, wherein the memory means stores a DC offset estimate corresponding to each possible value of the AGC signal.

4. A wireless receiver according to claim 3, wherein the number of DC offset estimates stored in the memory means is less than the finite number of possible values of the AGC signal, such that at least one of the stored DC offset estimates corresponds to more than one of the values of the AGC signal.

5. A wireless receiver according to claim 2, further comprising an analog to digital converter (ADC) for converting the scaled signal to a digital signal, wherein the receiver operates for received signals within a receiver dynamic range, the ADC operates on input signals within an ADC dynamic range and the possible values of the AGC signal are selected such that received signals within the receiver dynamic range are converted to scaled signals within the ADC dynamic range.

6. A wireless receiver according to claim 5, wherein the possible values of the AGC signal are selected such that received signals within the receiver dynamic range are converted to scaled signals within a desired ADC operating range, the desired ADC operating range being smaller than and within the ADC dynamic range.

7. A wireless receiver according to claim 1, further comprising means for removing DC offset from the scaled signal using the DC offset estimated by the means for estimating.

8. A wireless receiver according to claim 7, wherein the AGC means, the means for estimating the DC offset of the scaled signal and the means for removing DC offset from the scaled signal are implemented as software in a digital signal processor (DSP).

9. A wireless receiver according to claim 1, implemented in a wireless modem.

10. A wireless receiver according to claim 1, implemented in a mobile communication device.

11. A wireless receiver according to claim 10, wherein the mobile communication device is a cellular telephone.

12. A wireless receiver according to claim 10, wherein the mobile communication device is a two-way pager.

13. A wireless receiver according to claim 10, wherein the mobile communication device is a PDA.

14. A wireless receiver according to claim 10, wherein the mobile communication device is an Internet appliance.

15. A wireless receiver according to claim 1, implemented in an electronic device having means for short-range wireless communications.

16. In a wireless communication receiver, a gain control and DC offset estimation method comprising the steps of:

(a) applying a gain to a received signal, responsive to an automatic gain control (AGC) signal, to produce a scaled signal;

(b) determining an amplitude of the scaled signal;

(c) generating the AGC signal based on the amplitude of the scaled signal and an AGC algorithm, the AGC algorithm assigning one of a finite number of possible values to the AGC signal;

(d) estimating a DC offset of the scaled signal to generate an estimate; and

(e) updating a storage location in a memory means with the estimate, wherein the step of estimating the DC offset comprises a step of reading a previously stored estimate from the memory means and using the previously stored estimate to set the state of an exponential filter in order to estimate the DC offset of the scaled signal.

17. A method according to claim 16, wherein the step of reading from the memory means reads from a unique location of the memory means for each possible value of the AGC signal.

18. A method according to claim 16, wherein the step of reading from the memory means reads from a single common memory location of the memory means for at least two of the possible values of the AGC signal, such that at least one of the stored estimates corresponds to more than one of the values of the AGC signal.

19. A method according to claim 16, wherein the values of the AGC signal are selected such that the step of applying the gain to the received signal maintains the scaled signal within a desired dynamic range.

20. A method according to claim 16, further comprising a step of removing DC offset from the scaled signal using the estimate generated in step (d).

21. A method according to claim 16, implemented as software in a digital signal processor (DSP).

22. A method according to claim 21, implemented in a wireless modem.

23. A method according to claim 21, implemented in a cellular phone.

24. A method according to claim 21, implemented in a two-way pager.

25. A method according to claim 21, implemented in an Internet appliance.

26. A method according to claim 21, implemented in an electronic device having means for short-range communication.

27. A method according to claim 21, implemented in a wireless hand-held communication device.

28. In a wireless communications receiver, a software program stored on a computer-readable medium, which when executed by a processor in the receiver performs the method steps of:

(a) providing an automatic gain control (AGC) signal to a gain stage in the receiver to control a gain applied to the received signal, the gain stage producing a scaled signal;

(b) determining an amplitude of the scaled signal;

(c) generating the AGC signal based on the amplitude of the scaled signal and an AGC algorithm, the AGC signal having one of a finite number of possible values;

(d) estimating a DC offset of the scaled signal to generate an estimate;

(e) updating a storage location in a memory means with the estimate; and

(f) removing DC offset from the scaled signal using the estimate, wherein the step of estimating the DC offset comprises a step of reading from the memory means a previously stored estimate corresponding to the value of the AGC signal and using the previously stored estimate to set the state of an exponential filter in order to estimate the DC offset of the scaled signal.

29. A software program according to claim 28, wherein the computer-readable medium is resident in a digital signal processor (DSP).

30. A software program according to claim 28, implemented in a wireless hand-held communication device.

31. A software program according to claim 28, implemented in a cellular telephone.

32. A software program according to claim 28, implemented in a personal digital assistant (PDA).

33. A software program according to claim 28, implemented in a two-way pager.

34. A software program according to claim 28, implemented in an Internet appliance.

35. A software program according to claim 28, implemented in an electronic device having means for short-range communication.

36. A wireless communications receiver comprising:

(a) an antenna for receiving a communication signal;

(b) a receiver front end comprising means for filtering, amplifying and down-converting the communication signal received by the antenna;

(c) means for applying a gain to the signal output by the receiver front end to produce a scaled signal, the particular applied gain being controlled by an automatic gain control (AGC) signal;

(d) in-phase (I) and quadrature (Q) signal component processing means for separating the I and Q components of the scaled signal;

(e) analog to digital converting (ADC) means for converting the separated I and Q components to digital signals; and

(f) a digital signal processor (DSP) comprising;

(i) AGC means for determining amplitude of the I and Q components and generating the AGC signal; and

(ii) means for estimating a DC offset of the I and Q components to generate a DC offset estimate,

wherein the means for estimating the DC offset reads a previously stored DC offset estimate from a memory means and applies the previously stored estimate to set the state of an exponential filter in order to estimate the DC offset of the scaled signal.

37. A wireless receiver according to claim 36, wherein the AGC signal has a finite number of possible values and the means for estimating the DC offset reads a previously stored DC offset estimate corresponding to the value of the AGC signal generated by the AGC means.

38. A wireless receiver according to claim 37, wherein the means for estimating the DC offset of the scaled signal updates the previously stored DC offset value in the memory means.

39. A wireless receiver according to claim 36, the DSP further comprising means for correcting the I and Q components for DC offset using the DC offset estimated by the means for estimating.

40. A wireless receiver according to claim 36, implemented in a wireless modem.

41. A wireless receiver according to claim 36, implemented in a wireless hand-held communication device.

42. A wireless receiver according to claim 36, implemented in a two-way pager.

43. A wireless receiver according to claim 36, implemented in an Internet appliance.

44. A wireless receiver according to claim 36, implemented in an electronic device having means for short-range communication.