Distortion and aliasing reduction for digital to analog conversion
View Patent ↗Distortion and aliasing reduction for digital to analog conversion. Synthesis of one or more distortion terms made based on a digital signal (e.g., one or more digital codewords) is performed in accordance with digital to analog conversion. The one or more distortion terms may correspond to aliased higher-order harmonics, distortion, nonlinearities, clipping, etc. Such distortion terms may be known a priori, such as based upon particular characteristics of a given device, operational history, etc. Alternatively, such distortion terms may be determined based upon operation of a device and/or based upon an analog signal generated from the analog to conversion process. For example, frequency selective measurements made based on an analog signal generated from the digital to analog conversion may be used for determination of and/or adaptation of the one or more distortion terms. One or more DACs may be employed within various architectures operative to perform digital to analog conversion.
1. An apparatus, comprising:
a modulator for processing digital data thereby generating at least one codeword;
a first digital to analog converter (DAC) for processing the at least one codeword thereby generating a first analog signal;
a stop band filter for filtering the first analog signal thereby generating a filtered, first analog signal;
a synthesizer for providing at least one distortion term, based on the at least one codeword or a portion thereof and a control signal, corresponding to a frequency band of the first analog signal;
an adapter for modifying the at least one distortion term based on at least one frequency selective measurement corresponding to the filtered, first analog signal or at least one additional signal derived there from;
a second DAC for processing the at least one distortion term thereby generating a second analog signal;
a combiner for combining the filtered, first analog signal and the second analog signal thereby reducing distortion within the filtered, first analog signal thereby generating a combined signal; and
a controller for generating the control signal in accordance with dithering operations based on a measurement associated with the combined signal.
2. The apparatus of claim 1 , further comprising:
an up-converter for processing the second analog signal before providing it to the combiner.
3. The apparatus of claim 1 , further comprising:
a coupler for outputting at least a portion of a combined signal output from the combiner;
a frequency selective filter for selecting a spectral band component of the at least a portion of the combined signal;
a power detector for measuring power of the spectral band component; and wherein:
the controller for generating the control signal based on the measured power of the spectral band component.
4. The apparatus of claim 1 , wherein:
the first DAC operative at a first frequency; and
the second DAC operative at a second frequency.
5. The apparatus of claim 1 , wherein:
the synthesizer for generating the at least one distortion term in real time based on the at least one frequency selective measurement or at least one additional frequency selective measurement.
6. The apparatus of claim 1 , wherein:
the adapter for performing adaptive at least one of filtering, gain, phase, and delay adjustment of the at least one distortion term.
7. The apparatus of claim 1 , wherein:
the apparatus being a communication device operative within at least one of a satellite communication system, a wireless communication system, a wired communication system, and a fiber-optic communication system.
8. An apparatus, comprising:
a modulator for processing digital data thereby generating at least one codeword;
a first digital to analog converter (DAC), operating at a first frequency, for processing the at least one codeword thereby generating a first analog signal;
a stop band filter for filtering the first analog signal thereby generating a filtered, first analog signal;
a synthesizer for providing at least one distortion term, based on the at least one codeword or a portion thereof, corresponding to a frequency band of the first analog signal;
an adapter for modifying the at least one distortion term based on at least one frequency selective measurement corresponding to the filtered, first analog signal or at least one additional signal derived there from;
a second DAC, operating at a second frequency, for processing the modified at least one distortion term thereby generating a second analog signal; and
a combiner for combining the filtered, first analog signal and the second analog signal thereby reducing distortion within the filtered, first analog signal.
9. The apparatus of claim 8 , further comprising:
an up-converter for processing the second analog signal before providing it to the combiner.
10. The apparatus of claim 8 , further comprising:
an amplifier for processing the first analog signal before providing it to the stop band filter.
11. The apparatus of claim 8 , further comprising:
a coupler for outputting at least a portion of a combined signal output from the combiner;
a frequency selective filter for selecting a spectral band component of the at least a portion of the combined signal;
a power detector for measuring power of the spectral band component; and
a controller for directing operation of the adapter based on the measured power of the spectral band component.
12. The apparatus of claim 8 , wherein:
the synthesizer for generating the at least one distortion term in real time based on the at least one frequency selective measurement or at least one additional frequency selective measurement.
13. The apparatus of claim 8 , wherein:
the adapter for performing adaptive at least one of filtering, gain, phase, and delay adjustment of the at least one distortion term.
14. The apparatus of claim 8 , wherein:
the apparatus being a communication device operative within at least one of a satellite communication system, a wireless communication system, a wired communication system, and a fiber-optic communication system.
15. A method, comprising:
processing digital data thereby generating at least one codeword;
operating a first digital to analog converter (DAC) for processing the at least one codeword thereby generating a first analog signal;
stop band filtering the first analog signal thereby generating a filtered, first analog signal;
synthesizing at least one distortion term, based on the at least one codeword or a portion thereof, corresponding to a frequency band of the first analog signal;
modifying the at least one distortion term based on at least one frequency selective measurement corresponding to the filtered, first analog signal or at least one additional signal derived there from;
operating a second DAC for processing the modified at least one distortion term thereby generating a second analog signal; and
combining the filtered, first analog signal and the second analog signal thereby reducing distortion within the filtered, first analog signal.
16. The method of claim 15 , wherein:
operating the first DAC at a first frequency; and
operating the second DAC at a second frequency.
17. The method of claim 15 , further comprising:
coupling at least a portion of a combined signal generated from the combination of the filtered, first analog signal and the second analog signal;
performing frequency selective filtering for selecting a spectral band component of the at least a portion of the combined signal;
measuring power of the spectral band component; and
modifying the at least one distortion term based on the measured power of the spectral band component.
18. The method of claim 15 , further comprising:
generating the at least one distortion term in real time based on the at least one frequency selective measurement or at least one additional frequency selective measurement.
19. The method of claim 15 , wherein:
the modifying the at least one distortion term in accordance with performing adaptive at least one of filtering, gain, phase, and delay adjustment of the at least one distortion term.
20. The method of claim 15 , wherein:
the method performed within a communication device operative within at least one of a satellite communication system, a wireless communication system, a wired communication system, and a fiber-optic communication system.