A two-stage distortion limiter and method for limiting distortion in a sound signal, for example an output sound signal synthesis from a sound signal decoder. In a first stage, a level detector detects an amplitude value of the sound signal and computes a control gain using the detected amplitude value, and an attenuator reduces the level of the sound signal using the control gain. In a second stage, a saturation detector detects saturation in the sound signal and updates the control gain in response to detection of saturation.

In one embodiment, a signal-processing apparatus for generating an amplified output signal based on an input signal is provided. The apparatus comprises: an amplifier configured to generate the output signal, wherein the amplifier is configured to receive a supply voltage; and a limiter configured to inhibit increases in the input signal power level from being applied to the amplifier, wherein the limiter comprises: a variable attenuator configured to selectively attenuate the input signal before being applied to the amplifier; wherein the limiter integrates over a voltage difference between a current measure of attenuated input signal power level and a limiter threshold level to control a level of attenuation applied by the variable attenuator to the input signal.

In one embodiment, a signal-processing apparatus for generating an amplified output signal based on an input signal is provided. The apparatus comprises: an amplifier configured to generate the output signal, wherein the amplifier is configured to receive a supply voltage; and a limiter configured to inhibit increases in the input signal power level from being applied to the amplifier, wherein the limiter comprises: a variable attenuator configured to selectively attenuate the input signal before being applied to the amplifier; wherein the limiter integrates over a voltage difference between a current measure of attenuated input signal power level and a limiter threshold level to control a level of attenuation applied by the variable attenuator to the input signal.

A system is provided to analyze cross-modulation distortion in audio devices, which may include testing with audio frequencies. One or more distortion signals from the audio device may be measured for an amplitude, phase, and or frequency modulation effect. In another embodiment a musical signal may be used as a test signal. Providing additional test signals to the audio device can induce a time varying cross-modulation distortion signal from an output of the audio device. Utilizing at least one additional filter, filter bank, demodulator and or frequency converter and or frequency multiplier provides extra examination of distortion. Frequency and or phase response can be measured with the presence of a de-sensing signal and or another signal that induce near slew rate limiting or near overload condition of a device. Another system is provided to analyze modulation index differences between input and output signals for a test signal including modulation.

A system is provided to analyze cross-modulation distortion in audio devices, which may include testing with audio frequencies. One or more distortion signals from the audio device may be measured for an amplitude, phase, and or frequency modulation effect. In another embodiment a musical signal may be used as a test signal. Providing additional test signals to the audio device can induce a time varying cross-modulation distortion signal from an output of the audio device. Utilizing at least one additional filter, filter bank, demodulator and or frequency converter and or frequency multiplier provides extra examination of distortion. Frequency and or phase response can be measured with the presence of a de-sensing signal and or another signal that induce near slew rate limiting or near overload condition of a device. Another system is provided to analyze modulation index differences between input and output signals for a test signal including modulation.

A signal processing method, especially for audio signals, comprises: receiving input signal samples having source signal portions associated with respective time periods (In_n1); generating parameters associated with the respective time periods by processing the respective input signal samples, in which the step of generating the parameters has an associated non-zero latency period so that generating step provides a parameter p in a time period (T_n1) later than the start of the respective time period; and generating an output data portion associated with a given time period (Out_n1 using a signal processing function F which depends upon the input signal samples in the given time period (In_n1) and an approximated parameter p (1110) associated with a time period other than the given time period (T_n2).

A signal processing method, especially for audio signals, comprises: receiving input signal samples having source signal portions associated with respective time periods (In_n1); generating parameters associated with the respective time periods by processing the respective input signal samples, in which the step of generating the parameters has an associated non-zero latency period so that generating step provides a parameter p in a time period (T_n1) later than the start of the respective time period; and generating an output data portion associated with a given time period (Out_n1 using a signal processing function F which depends upon the input signal samples in the given time period (In_n1) and an approximated parameter p (1110) associated with a time period other than the given time period (T_n2).

In one embodiment, a signal-processing apparatus for generating an amplified output signal based on an input signal is provided. The apparatus comprises: an amplifier configured to generate the output signal, wherein the amplifier is configured to receive a supply voltage; and a limiter configured to inhibit increases in the input signal power level from being applied to the amplifier, wherein the limiter comprises: a variable attenuator configured to selectively attenuate the input signal before being applied to the amplifier; wherein the limiter integrates over a voltage difference between a current measure of attenuated input signal power level and a limiter threshold level to control a level of attenuation applied by the variable attenuator to the input signal.

In one embodiment, a signal-processing apparatus for generating an amplified output signal based on an input signal is provided. The apparatus comprises: an amplifier configured to generate the output signal, wherein the amplifier is configured to receive a supply voltage; and a limiter configured to inhibit increases in the input signal power level from being applied to the amplifier, wherein the limiter comprises: a variable attenuator configured to selectively attenuate the input signal before being applied to the amplifier; wherein the limiter integrates over a voltage difference between a current measure of attenuated input signal power level and a limiter threshold level to control a level of attenuation applied by the variable attenuator to the input signal.

A signal-processing system has an amplifier that generates an amplified (RF) output signal based on an (RF) input signal. The amplifier receives a supply voltage that can be selectively set to an appropriate level between a lower power supply level and a higher power supply level. With one power supply permanently connected to the supply voltage node, a control unit executes software to toggle a supply switch to periodically connect and disconnect the other power supply thereby generating a weighted average value for the supply voltage between the two power supply levels. When a sudden and large increase occurs in the (input) power level, hardware-interrupt circuitry interrupts and supersedes the software-based control of the supply-voltage switch to quickly switch the supply voltage towards the higher power supply level. The hardware-interrupt circuitry handles such situations faster than the software-based control in order to prevent a limit violation of spectrum emission requirements.