Receiver architecture with digitally generated intermediate frequency

• US 20060083335A1
• Filed: 10/12/2005
• Published: 04/20/2006
• Est. Priority Date: 10/12/2004
• Status: Abandoned Application

• Current Assignee: Maxlinear Incorporated
• Original Assignee: Maxlinear Incorporated
• Inventors: Ling, Curtis, Montemayor, Raymond, Chang, Glenn, Ye, Sheng, Seendripu, Kishore
• Application Number:
  US11/248,657
• Publication Number:
  US 20060083335A1
• Time in Patent Office: Days
• US Class Current: 375/332
• CPC Class Codes: H03D 3/008 Compensating DC offsets
• CPC Class Codes: H03D 3/009 Compensating quadrature phase or amplitude imbalances
• CPC Class Codes: H03D 7/166 using two or more quadrature frequency translation stages
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26

Abstract

A receiver can be configured to include an RF front end that is configured to downconvert a received signal to a baseband signal or a low Intermediate Frequency (IF) signal. The receiver can downconvert the desired signal from an RF frequency in the presence of numerous interference sources to a baseband or low IF signal for filtering and channel selection. The filtered baseband or low IF signal can be converted to a digital representation. The digital representation of the signal can be upconverted in the digital domain to a programmable IF frequency. The digital IF signal can be converted to an analog IF signal that can be processed by legacy hardware.

Claims

1. A receiver comprising:

a downconverter configured to downconvert an input signal to a signal in a first frequency band;

an analog to digital converter (ADC) coupled to the downconverter and configured to digitize the signal in the first frequency band to produce a digital representation of the signal in the first frequency band; and

a digital upconverter configured to upconvert the digital representation of the signal in the first frequency band to a digital representation of the signal in a second frequency band.

2. The receiver of claim 1, wherein the first frequency band comprises one of a baseband frequency band or a low Intermediate Frequency (IF) band based on a mode of the receiver.

3. The receiver of claim 1, wherein the downconverter comprises:

an in-phase downconverter configured to downconvert an in-phase component of the input signal to the first frequency band; and

a quadrature downconverter configured to downconvert a quadrature component of the input signal to the first frequency band.

4. The receiver of claim 1, wherein the downconverter comprises:

an in-phase downconverter configured to downconvert an in-phase component of the input signal to substantially a baseband in-phase signal; and

a quadrature downconverter configured to downconvert a quadrature component of the input signal to substantially a baseband quadrature signal.

5. The receiver of claim 1, wherein the downconverter comprises:

an in-phase downconverter configured to downconvert an in-phase component of the input signal to a in-phase low Intermediate Frequency (IF) signal; and

a quadrature downconverter configured to downconvert a quadrature component of the input signal to a quadrature low IF signal.

6. The receiver of claim 1, further comprising a filter configured to perform at least partial channel selection of the signal in the first frequency band prior to the ADC.

7. The receiver of claim 1, further comprising a digital filter configured to perform channel selection of the digital representation of the signal in the first frequency band.

8. The receiver of claim 1, wherein the digital upconverter comprises:

a first digital upconverter configured to digitally upconvert an in-phase component of the input signal to an in-phase digital signal at a desired Intermediate Frequency (IF); and

a second digital upconverter configured to digitally upconvert a quadrature component of the input signal to a quadrature digital signal at the desired IF.

9. The receiver of claim 8, further comprising a digital signal combiner configured to combine the in-phase digital signal at the desired IF with the quadrature digital signal at the desired IF.

10. A receiver comprising:

a first frequency converter configured to downconvert a received signal to an in-phase baseband signal component;

a second frequency converter configured to downconvert the received signal to a quadrature baseband signal component;

a first analog filter coupled to the first frequency converter and configured to perform at least partial channel selection on the in-phase baseband signal component;

a second analog filter coupled to the second frequency converter and configured to perform at least partial channel selection on the quadrature baseband signal component;

a first Analog to Digital Converter (ADC) coupled to the first analog filter and configured to convert the in-phase baseband signal component to a digital in-phase baseband signal component;

a second ADC coupled to the second analog filter and configured to convert the quadrature baseband signal component to a digital quadrature baseband signal component;

a first digital filter coupled to the first ADC and configured to digitally filter the digital in-phase baseband signal component to generate a digitally filtered in-phase baseband signal component;

a second digital filter coupled to the second ADC and configured to digitally filter the digital quadrature baseband signal component to generate a digitally filtered quadrature baseband signal component;

a first digital upconverter configured to digitally upconvert the digitally filtered in-phase baseband signal component to an in-phase Intermediate Frequency (IF) signal component at a desired IF;

a second digital upconverter configured to digitally upconvert the digitally filtered quadrature baseband signal component to a quadrature IF signal component at the desired IF; and

a digital signal combiner configured to combine the in-phase IF signal component with the quadrature IF signal component.

11. A method of receiving a signal, the method comprising:

frequency converting an input signal to an intermediate signal in a first frequency band;

digitizing the intermediate signal; and

digitally converting the intermediate signal to a second frequency band.

12. The method of claim 11, wherein frequency converting the input signal comprises:

downconverting the input signal to an in-phase baseband signal component; and

downconverting the input signal to a quadrature baseband signal component.

13. The method of claim 11, wherein the intermediate signal comprises:

an in-phase baseband signal component; and

a quadrature baseband signal component.

14. The method of claim 11, further comprising performing partial channel selection on the intermediate signal.

15. The method of claim 11, wherein digitizing the intermediate signal comprises:

digitizing an in-phase signal component of the intermediate signal; and

digitizing a quadrature signal component of the intermediate signal.

16. The method of claim 11, wherein digitally converting the intermediate signal comprises:

digitally upconverting an in-phase signal component of the intermediate signal to an in-phase Intermediate Frequency (IF) component at a desired IF;

digitally upconverting a quadrature signal component of the intermediate signal to a quadrature IF component at the desired IF; and

combining the in-phase IF component with the quadrature IF component.

17. A method of calibrating a quadrature receiver, the method comprising:

injecting a calibration tone to a signal path of a quadrature receiver;

detecting an amplitude and phase imbalance of the quadrature receiver;

adjusting a gain of at least one of an in-phase and a quadrature signal path based on the amplitude imbalance; and

adjusting a phase of at least one of the in-phase and quadrature signal paths based on the phase imbalance.

18. The method of claim 17, wherein injecting the calibration tone comprises injecting one of a quadrature or an in-phase Local Oscillator (LO) signal to the signal path.

19. The method of claim 18, wherein the one of the quadrature or in-phase LO signal is synchronized with a LO signal used to downconvert the calibration tone to a DC signal.

20. The method of claim 17, wherein detecting the amplitude and phase imbalance of the quadrature receiver comprises:

downconverting an in-phase Intermediate Frequency (IF) signal component to a first DC signal;

downconverting a quadrature IF signal component to a second DC signal;

combining the first and second DC signals to generate a combined DC signal; and

determining the phase imbalance based on the combined DC signal.

21. A quadrature receiver calibration apparatus, the apparatus comprising:

a tone generator configured to generate a calibration tone;

a coupler configured to couple the calibration tone to a signal path of the quadrature receiver;

a detector configured to detect an in-phase and quadrature signal component when the calibration tone is coupled to the signal path;

a gain feedback module configured to adjust a gain of at least one of an in-phase signal path and a quadrature signal path; and

a phase feedback module configured to adjust a phase of at least one of the in-phase signal path and the quadrature signal path.