Method and apparatus for oversampled, noise-shaping, mixed-signal processing

A switching power amplifier, comprising:

• a first integrator stage in a feedback loop, the first integrator stage having an input;
• a second integrator stage in the feedback loop coupled to the first integrator stage, the second integrator stage having an input;
• a discrete time comparator stage in the feedback loop coupled to the second integrator stage;
• a power switching stage in the feedback loop, the power switching stage having an input and an output, the input of the power switching stage being coupled to the comparator stage;
• and
• a continuous-time feedback path from the output of the power switching stage to the input of at least one of the first and second integrator stages thereby closing the feedback loop, the feedback loop also including means for reducing aliasing effects corresponding to a sample frequency.

A switching power amplifier, comprising:

• a first integrator stage in a feedback loop, the first integrator stage having an input;
• a second integrator stage in the feedback loop coupled to the first integrator stage, the second integrator stage having an input;
• a third integrator stage in the feedback loop coupled to the second integrator stage, the third integrator stage having an input;
• a discrete time comparator stage in the feedback loop coupled to the third integrator stage;
• a power switching stage in the feedback loop, the power switching stage having an input and an output, the input of the power switching stage being coupled to the comparator stage;
• and
• a continuous-time feedback path from the output of the power switching stage to the input of at least one of the first, second and third integrator stages thereby closing the feedback loop, the feedback loop also including means for reducing aliasing effects corresponding to a sample frequency.

A signal processing method comprising the steps of:

• introducing an input signal to a frequency selective network thereby generating a frequency-selected signal;
• sampling the frequency-selected signal only at discrete time intervals at a predefined sample frequency, thereby generating a sampled signal;
• switching the sampled signal thereby generating a continuous-time output signal;
• and
• feeding back the continuous-time output signal to the frequency selective network thereby generating a noise-shaped signal.

A signal processing circuit, comprising:

• a frequency selective network in a feedback loop;
• a sampling analog-to-digital converter in the feedback loop, the sampling analog-to-digital converter being sampled at a sample frequency;
• a switching device coupled to be driven by the sampling analog-to-digital converter to produce a continuous-time output signal;
• and
• means for continuously sensing and feeding back the continuous-time output signal to the frequency selective network for noise and distortion correction in the feedback loop and noise shaping.

An oversampled, noise-shaping, mixed-signal processor, comprising:

• at least one integrator stage in a feedback loop, the at least one integrator stage having an input;
• a sampling stage in the feedback loop coupled to the at least one integrator stage, the sampling stage for sampling an analog signal at a sample frequency;
• a switching stage in the feedback loop coupled to the sampling stage, the switching stage having an input and an output;
• and
• a continuous-time feedback path from the output of the switching stage to the input of the at least one integrator stage thereby closing the feedback loop, the feedback loop also including means for reducing aliasing effects corresponding to the sample frequency, wherein the processor comprises a plurality of integrator stages, the processor further comprising a state feedback path from the input of the switching stage to at least one of the plurality of integrator stages.

A signal processing method comprising the steps of:

• introducing an input signal to a frequency selective network thereby generating a frequency-selected signal;
• sampling the frequency-selected signal at intervals at a sample frequency, thereby generating a sampled signal;
• switching the sampled signal thereby generating a continuous-time output signal;
• and
• feeding back the continuous-time output signal to the frequency selective network while reducing aliasing effects thereby generating a noise-shaped signal, wherein the frequency selective network comprises at least one sampled stage, the reducing step comprising oversampling the at least one sampled stage with respect to the sample frequency.

A signal processing method comprising the steps of:

• introducing an input signal to a frequency selective network thereby generating a frequency-selected signal;
• sampling the frequency-selected signal at intervals at a sample frequency, thereby generating a sampled signal;
• switching the sampled signal thereby generating a continuous-time output signal;
• feeding back the continuous-time output signal to the frequency selective network thereby generating a noise-shaped signal;
• and
• introducing a dithering signal to the frequency-selected signal for the purpose of tone elimination.