US 2013/0095776 A1 · CANCELLATION OF SPECTRAL IMAGES IN COMMUNICATION DEVICES

Abstract

Digital-to-analog conversion in a communication device typically results in superimposed spectral images in the frequency spectrum of the analog waveform. These superimposed spectral images can distort the analog waveform and potentially violate the spectral mask and the constraints on out-of-band emissions set by the FCC. The communication device can be configured to implement a spectral image cancellation unit with feed-forward architecture to minimize the spectral images in the frequency spectrum of the analog waveform. The spectral image cancellation unit can generate a spectral image error signal comprising the spectral images at one or more spectral image frequencies. The spectral image cancellation unit can then subtract the spectral image error signal from the analog waveform to reduce spectral image components of the analog waveform and to yield an output signal for transmission.

Claims20

Dependent claims

An apparatus comprising:

a digital-to-analog conversion unit operable to:
generate a radio frequency (RF) analog composite signal comprising an RF transmission signal component and a superimposed RF spectral image signal component;
and
a spectral image cancellation unit coupled with the digital-to-analog conversion unit, the spectral image cancellation unit operable to:
generate a baseband analog composite signal comprising a baseband transmission signal component and a superimposed baseband spectral image signal component;
filter the baseband analog composite signal to yield a baseband spectral image signal;
up-convert the baseband spectral image signal in accordance with a predetermined carrier signal to yield an RF spectral image signal;
and
subtract the RF spectral image signal from the RF analog composite signal generated by the digital-to-analog conversion unit to reduce the superimposed RF spectral image signal component associated with the RF analog composite signal and generate an output RF transmission signal.

6 more elements

An apparatus comprising:

a digital-to-analog conversion unit operable to:
generate a baseband analog composite signal comprising a baseband transmission signal component and a superimposed baseband spectral image signal component;
a signal amplifier coupled with the digital-to-analog conversion unit, the signal amplifier operable to:
amplify the baseband analog composite signal in accordance with a predetermined signal amplification factor;
and
a spectral image cancellation unit coupled with the signal processing unit, the spectral image cancellation unit operable to:
filter the baseband analog composite signal to yield a baseband spectral image signal;
amplify the baseband spectral image signal in accordance with a predetermined error amplification factor based, at least in part, on the amplitude of the superimposed baseband spectral image signal component generated by the signal processing unit;
and
subtract the baseband spectral image signal from the baseband analog composite signal generated by the signal processing unit to reduce the superimposed baseband spectral image signal component associated with the baseband analog composite signal and generate an output baseband transmission signal.

7 more elements

An apparatus comprising:

a signal processing unit operable to:
generate a baseband analog composite signal comprising a baseband transmission signal component and a superimposed baseband spectral image signal component, wherein the superimposed baseband spectral image signal component is associated with one or more spectral image frequencies;
and
a spectral image cancellation unit coupled with the signal processing unit, the spectral image cancellation unit operable to:
for each of the one or more spectral image frequencies associated with the baseband spectral image signal component of the baseband analog composite signal,
generate an error signal at the spectral image frequency that comprises a spectral image signal component at the spectral image frequency;
amplify the error signal at the spectral image frequency in accordance with an error amplification factor based, at least in part, on an amplitude of the superimposed baseband spectral image signal component generated by the signal processing unit;
and
subtract one or more error signals at the corresponding one or more spectral image frequencies from the baseband analog composite signal generated by the signal processing unit to reduce the superimposed baseband spectral image signal component associated with the baseband analog composite signal and generate an output baseband transmission signal.

6 more elements

An apparatus comprising:

a signal processing unit operable to:
generate a baseband analog composite signal comprising a baseband transmission signal component and a superimposed baseband spectral image signal component based on an input baseband digital signal comprising information to be transmitted, wherein the superimposed spectral image signal component is at a spectral image frequency;
and
a spectral image cancellation unit coupled with the signal processing unit, the spectral image cancellation unit operable to:
generate an analog in-phase spectral image signal component and an analog quadrature spectral image signal component based on the input baseband digital signal comprising information to be transmitted;
up-convert the analog in-phase spectral image signal component and the analog quadrature spectral image signal component in accordance with the spectral image frequency;
combine the up-converted analog in-phase spectral image signal component and the analog quadrature spectral image signal to yield a baseband spectral image signal at the spectral image frequency;
and
subtract the baseband spectral image signal at the spectral image frequency from the baseband analog composite signal generated by the signal processing unit to reduce the superimposed baseband spectral image signal component associated with the baseband analog composite signal and generate an output baseband transmission signal.

6 more elements

A method comprising:

generating a radio frequency (RF) analog composite signal comprising an RF transmission signal component and a superimposed RF spectral image signal component based on a digital baseband signal comprising information to be transmitted;
generating a baseband analog composite signal comprising a baseband transmission signal component and a superimposed baseband spectral image signal component based on the digital baseband signal comprising information to be transmitted;
filtering the baseband analog composite signal to yield a baseband spectral image signal;
up-converting the baseband spectral image signal in accordance with a predetermined carrier signal to yield an RF spectral image signal;
and
subtracting the RF spectral image signal from the RF analog composite signal to reduce the superimposed RF spectral image signal component associated with the RF analog composite signal and generate an output RF transmission signal.

3 more elements

Dependencies are inferred from the claim text.

Cancellation of spectral images in communication devices

Life of this patent

Cancellation of spectral images in communication devices

Life of this patent

Abstract

Claims20