DC offset filter for wide band beamforming receivers

• US 9,312,897 B2
• Filed: 10/31/2012
• Issued: 04/12/2016
• Est. Priority Date: 10/31/2012
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Steele, Gregory, Tsfati, Yossi, Weissman, Haim M, Taghivand, Mazhareddin
• Primary Examiner(s): Safaipour, Bobbak
• Assistant Examiner(s): SANDIFORD, DEVAN A
• Application Number:
  US13/664,678
• Publication Number:
  US 20140120851A1
• Time in Patent Office: 1,259 Days
• Field of Search: 455/90.2, 455/306, 455/307
• US Class Current: 1/1
• CPC Class Codes: H03D 2200/0043 Bias and operating point
• CPC Class Codes: H03D 2200/0047 Offset of DC voltage or frequency
• CPC Class Codes: H03D 3/008 Compensating DC offsets
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04B 2001/1063 using a notch filter

Abstract

A DC offset filter for wide band beamforming receivers is disclosed. In an exemplary embodiment, an apparatus includes a first mixer configured to down-convert an RF wideband beamformed signal to generate a first baseband wideband beamformed signal, the RF wideband beamformed signal having a beam pattern selected from a plurality of beam patterns, and a notch filter configured to remove DC offset from the first baseband wideband beamformed signal independent of the beam pattern.

Claims

1. An apparatus comprising:

a first mixer configured to down-convert an RF wideband beamformed signal to generate a first baseband wideband beamformed signal, the RF wideband beamformed signal having a beam pattern selected from a plurality of beam patterns;

a DC blocking capacitor connected between an output of the first mixer and an input of a baseband filter, the DC blocking capacitor forming a notch filter that is configured to remove DC offset from the first baseband wideband beamformed signal independent of the beam pattern selection;

a bypass switch connected across the DC blocking capacitor configured to operate in a bypass mode to bypass the DC blocking capacitor and to operate in a non bypass mode to enable the DC blocking capacitor to remove the DC offset; and

a loopback switch configured to loop back RF wideband transmit signal to the input of the first mixer;

wherein the apparatus is configured to;

close the bypass switch and the loopback switch and perform a first DC offset measurement;

open the bypass switch and perform a second DC offset measurement;

set the bypass switch based on the first DC offset measurement and the second DC offset measurement; and

open the loopback switch.

2. The apparatus of claim 1, the DC blocking capacitor having a capacitance value that provides a corner frequency of approximately 300 kHz.

3. The apparatus of claim 1, the bypass switch configured to operate in a loopback calibration mode to provide transceiver calibration.

4. The apparatus of claim 1, further comprising a second mixer configured to down-convert the RF wideband beamformed signal to generate a second baseband wideband beamformed signal that bypasses the DC blocking capacitor.

5. The apparatus of claim 4, further comprising a mode signal configured to enable the second mixer in a bypass mode and to disable the second mixer in a non bypass mode.

6. The apparatus of claim 1, the first mixer comprising a direct conversion mixer.

7. An apparatus comprising:

means for down-converting an RF wideband beamformed signal to generate a baseband wideband beamformed signal, the RF wideband beamformed signal having a beam pattern selected from a plurality of beam patterns;

means for notch filtering to remove DC offset from the baseband wideband beamformed signal independent of the beam pattern selection;

a bypass switch configured to selectively bypass the means for notch filtering during a bypass mode and for enabling the means for notch filtering to remove the DC offset; and

a loopback switch configured to selectively providing a RF wideband transmit signal along with the RF wideband beamformed signal;

means for closing the bypass switch and the loopback switch and performing a first DC offset measurement;

means for opening the bypass switch and performing a second DC offset measurement;

means for setting the bypass switch based on the first DC offset measurement and the second DC offset measurement; and

means for opening the loopback switch.

8. The apparatus of claim 7, the means for notch filtering comprises the DC blocking capacitor connected between an output of the means for down-converting and an input of a baseband filter.

9. The apparatus of claim 8, the DC blocking capacitor having a capacitance value that provides a corner frequency of approximately 300 kHz.

10. The apparatus of claim 7, the means for down-converting comprising a direct conversion mixer.