METHODS AND SYSTEMS TO DIGITALLY SWITCH BETWEEN FREQUENCIES AND CORRESPONDING BANDWIDTHS IN A TRANSCEIVER

• US 20110069740A1
• Filed: 09/23/2009
• Published: 03/24/2011
• Est. Priority Date: 09/23/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Laudel, Kennan Herbert, Cowley, Nicholas
• Granted Patent: US 8,300,731 B2
• Time in Patent Office: Days
• US Class Current: 375/132
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges

Abstract

Methods and systems to maintain a tuner at a fixed frequency and to switch between frequencies and bandwidths in a digital domain. IQ imbalance equalization coefficients may be determined with respect to a frequency and bandwidth of a first signal, and the coefficients may be applied to baseband data associated with one or more other frequencies and/or bandwidths. Methods and systems disclosed herein may be applied in a multi-mode Multimedia over Coax Alliance (MoCA) environment, such as to digitally switch between a MoCA 2 standard and a MoCA 1.x standard.

Claims

1. A system, comprising:

a receive tuner, tuned with respect to a first frequency, to down-convert a first modulated signal having a first bandwidth centered about the first frequency to baseband components centered about zero Hertz (Hz), and to down-convert a second modulated signal having a second bandwidth centered about a second frequency to a relatively low intermediate frequency (IF);

an analog-to-digital converter (ADC) to digitize outputs of the receive tuner; and

digital baseband processor including a multi-mode digital demodulator to demodulate data output from the ADC within a bandwidth that encompasses the first and second bandwidths, wherein the demodulator is digitally controllable to operate at zero Hz with respect to the first signal, and to operate at the intermediate frequency with respect to the second signal.

2. The system of claim 1, wherein the first bandwidth encompasses the second bandwidth, and wherein the digital baseband processor further includes:

a digital baseband module calibrated with respect to one or more of the first frequency and the first bandwidth to process baseband components of the first and second signals.

3. The system of claim 2, wherein the digital baseband module includes:

a digital IQ imbalance compensation module, calibrated with respect to the first frequency, to apply corresponding compensation parameters to baseband components of the first and second signals.

4. The system of claim 2, wherein:

the first bandwidth is at least twice the second bandwidth; and

the second bandwidth is at least twice an offset between the first and second frequencies.

5. The system of claim 1, wherein:

the receive tuner includes in-phase and quadrature phase (I and Q) single-stage frequency down-converters and corresponding I and Q baseband filters; and

the digital demodulator is configured to demodulate orthogonal frequency division multiplex (OFDM) data.

6. The system of claim 5, wherein:

the frequency down-converters are tuned to a frequency within a range of approximately 1125 MHz to 1675 MHz;

the baseband filters have a bandwidth of at least −

50 MHz to 50 MHz;

the baseband demodulator is configured to demodulate OFDM data within a bandwidth of at least 100 MHz.

7. The system of claim 6, wherein the digital baseband processor further includes:

a digital IQ imbalance compensation module, calibrated to compensate frequency dependent IQ imbalance associated with the baseband filters at the first frequency and to compensate frequency independent IQ imbalance associated with the frequency down-converters, and to apply corresponding compensation parameters to baseband components of the first and second signals.

8. The system of claim 1, wherein the digital demodulator is configured to perform single sideband demodulation at least with respect to the second signal.

9. The system of claim 1, wherein the digital baseband processor further includes a multi-mode digital modulator, digitally controllable to modulate data in a selected one of first and second modes, wherein the first mode corresponds to a first bandwidth centered about zero Hz and the second mode corresponds to a second bandwidth centered about a relatively low intermediate frequency (IF), the system further including:

a digital-to-analog converter (DAC) coupled to outputs of the digital modulator; and

a transmit tuner, tuned with respect to the first frequency, to receive outputs of the DAC.

10. The system of claim 9, wherein the digital modulator is configured to perform single sideband modulation at least with respect to the intermediate frequency.

11. A system, comprising:

a digital baseband processor including a multi-mode digital modulator, digitally controllable to modulate data in a selected one of first and second modes, wherein the first mode corresponds to a first bandwidth centered about zero Hz and the second mode corresponds to a second bandwidth centered about a relatively low intermediate frequency (IF);

a digital-to-analog converter (DAC) to digitize outputs of the digital modulator; and

a transmit tuner, tuned with respect to a first frequency, to frequency up-convert first mode outputs of the DAC to the first frequency and to frequency up-convert second mode outputs of the DAC to a second frequency equal to a sum of the first frequency and the IF.

12. The system of claim 11, wherein the first bandwidth encompasses the second bandwidth, the system further including:

a digital baseband module calibrated with respect to one or more of the first frequency and the first bandwidth to process baseband components of data associated with the first and second modes.

13. The system of claim 12, wherein the digital baseband module includes:

a digital IQ imbalance pre-compensation module, calibrated with respect to the first frequency, to apply corresponding compensation parameters to baseband components of data associated with the first and second modes.

14. The system of claim 12, wherein:

the first bandwidth is at least twice the second bandwidth; and

the second bandwidth is at least twice an offset between the first and second frequencies.

15. The system of claim 11, wherein:

the transmit tuner includes in-phase and quadrature phase (I and Q) single-stage frequency up-converters and corresponding I and Q baseband filters; and

the digital modulator is configured to perform orthogonal frequency division multiplex (OFDM) modulation.

16. The system of claim 15, wherein:

the frequency up-converters are tuned to a frequency in a range of approximately 1125 MHz to 1675 MZ;

the baseband filters have a bandwidth of at least −

50 MHz to 50 MHz;

the digital modulator is configured to perform OFDM modulation within a bandwidth of at least 100 MHz.

17. The system of claim 16, wherein the digital baseband processor further includes:

a digital IQ imbalance compensation module, calibrated to compensate frequency dependent IQ imbalance associated with the baseband filters at the first frequency and to compensate frequency independent IQ imbalance associated with the frequency up-converters, and to apply corresponding compensation parameters to baseband components of data associated with the first and second modes.

18. A method, comprising:

receiving a first modulated signal having a first bandwidth centered about a first frequency and a second modulated signal having a second bandwidth centered about a second frequency, wherein the first bandwidth encompasses the second bandwidth, and wherein the first and second frequencies differ by a relatively small intermediate frequency (IF);

frequency down-converting the first and second modulated signals by the first frequency;

digitizing results of the down-converting;

digitally selecting a first receive mode to process the first signal and a second receive mode to process the second signal;

digitally demodulating the digitized results within the first bandwidth centered about zero Hertz (Hz) during the first receive mode; and

digitally demodulating the digitized results within the first bandwidth centered about the IF during the second receive mode.

19. The method of claim 18, further including:

digitally selecting amongst first and second transmit modes;

digitally modulating data within the first bandwidth centered about zero Hz during the first transmit mode;

digitally modulating data within the second bandwidth centered about the IF during the second transmit mode; and

frequency-up converting the modulated data corresponding to the first and second transmit modes with respect to the first frequency, including frequency-up converting first transmit mode modulated data to the first frequency, and frequency-up converting second transmit mode modulated data to a sum of the first frequency and the intermediate frequency.

20. The method of claim 19, wherein the first bandwidth encompasses the second bandwidth, the method further including:

digitally determining receive path and transmit path IQ imbalance compensation parameters, with respect to one or more of the first frequency and the first bandwidth; and

applying the IQ imbalance compensation parameters during the first and second receive and transmit modes.