Abstract: Systems and methods for loudspeaker protection against excessive excursion are described. In an illustrative, non limiting embodiment, a method may include splitting an input signal into two or more signals, each of the two or more signals within a given frequency band; independently selecting between a power attenuation or an excursion attenuation for each of the two or more signals; independently applying the selected power attenuation or excursion attenuation to each of the two or more signals; combining the attenuated two or more signals into an output signal; and providing the output signal to a loudspeaker.

Abstract: A system includes a class D amplifier and a current steering digital-to-analog converter (DAC) directly connected to the class D amplifier. The system also includes a common mode servo circuit coupled to a node interconnecting the current steering DAC to the class D amplifier. The common servo circuit amplifies a difference between a common mode signal determined from the node and a reference voltage and generates a feedback current to the node based on the amplified difference. A feed-forward common-mode compensation circuit is included to reduce an alternating current (AC) ripple from the class D amplifier. The feed-forward common-mode compensation circuit includes first and second resistors coupled to respective outputs of the class D amplifier. A current mirror is coupled to the first and second resistors and is configured to sink a current from the node to ground that approximates a common mode feedback current of the class D amplifier.

Abstract: A system includes a class D amplifier and a current steering digital-to-analog converter (DAC) directly connected to the class D amplifier. The system also includes a common mode servo circuit coupled to a node interconnecting the current steering DAC to the class D amplifier. The common servo circuit amplifies a difference between a common mode signal determined from the node and a reference voltage and generates a feedback current to the node based on the amplified difference. A feed-forward common-mode compensation circuit is included to reduce an alternating current (AC) ripple from the class D amplifier. The feed-forward common-mode compensation circuit includes first and second resistors coupled to respective outputs of the class D amplifier. A current mirror is coupled to the first and second resistors and is configured to sink a current from the node to ground that approximates a common mode feedback current of the class D amplifier.

Abstract: Methods for modeling a loudspeaker having a passive radiator include applying a stimulus signal to a speaker within the cabinet, wherein the stimulus is applied over a frequency range. The sound pressure level (SPL) in the cabinet is measured as a function of frequency during application of the stimulus signal. At least one coefficient based on the measured SPL is derived, wherein at least one passive radiator parameter is a function of the at least one coefficient.

Abstract: Systems and methods for loudspeaker protection against excessive excursion are described. In an illustrative, non limiting embodiment, a method may include splitting an input signal into two or more signals, each of the two or more signals within a given frequency band; independently selecting between a power attenuation or an excursion attenuation for each of the two or more signals; independently applying the selected power attenuation or excursion attenuation to each of the two or more signals; combining the attenuated two or more signals into an output signal; and providing the output signal to a loudspeaker.

Abstract: A predictive back-emf protection methodology for an electromechanical system, including a signal processor that processes a source signal to provide a modified source signal, a driver that converts the modified source signal to a drive signal, and an electromechanical transducer that generates, from the drive signal, a transducer response, and a back-emf signal coupled back to the driver output. A predictive back-emf generator (such as a routine in the signal processor) is characterized by a back-emf transfer function (linear parameterized model of the electromechanical transducer) for transforming an input signal into a transform back-emf representation of a back-emf signal predicted by the back-emf transfer function as a response of the electromechanical transducer to such input signal. The signal processor processes the source signal based on the transform back-emf representation to generate the modified source signal input to the driver.

Abstract: Methods for modeling a loudspeaker having a passive radiator include applying a stimulus signal to a speaker within the cabinet, wherein the stimulus is applied over a frequency range. The sound pressure level (SPL) in the cabinet is measured as a function of frequency during application of the stimulus signal. At least one coefficient based on the measured SPL is derived, wherein at least one passive radiator parameter is a function of the at least one coefficient.

Abstract: In an embodiment of the invention, the voice coil of an electro dynamic transducer is protected against thermal overload by estimating the temperature of a magnet in the electro dynamic transducer. When a power limit based on the temperature of the magnet and on a predetermined voice coil temperature limit is reached by an audio signal, the power applied to the voice coil is reduced.

Abstract: In an embodiment of the invention, the voice coil of an electro dynamic transducer is protected by measuring the power of the input audio signal. When a predetermined power limit is reached by the input audio signal, the power of the input audio signal is reduced.

Abstract: In an embodiment of the invention, over-excursion of a diaphragm in an electro dynamic transducer is reduced by attenuating low frequency content in an audio signal when the power of an audio signal exceeds a predetermined power limit. The audio signal is used to drive the input of an amplifier and the output of the amplifier drives the electro dynamic transducer. When the audio signal does not exceed a predetermined power limit, the low frequency content in the input audio signal is amplified.

Abstract: In an embodiment of the invention, the voice coil of an electro dynamic transducer is protected against thermal overload by estimating the temperature of a magnet in the electro dynamic transducer. When a power limit based on the temperature of the magnet and on a predetermined voice coil temperature limit is reached by an audio signal, the power applied to the voice coil is reduced.

Abstract: Asynchronous sample rate conversion for use in a digital audio receiver is disclosed. Different algorithms are applied for the upsampling and downsampling cases. In the upsampling case, the input signal is upsampled and filtered, before the application of a finite impulse response (FIR) filter. In the downsampling case, the input signal is filtered by an FIR filter, and then filtered and downsampled. The FIR coefficients of the fractional delay FIR filter are calculated by evaluation of polynomial expressions over intervals of the filter impulse response, at times corresponding to the input sample points.

Abstract: System for pulse-width-modulated class D audio amplifiers. In one preferred embodiment an adder is described to generate a difference signal responsive to an input signal and a feedback signal, a pulse-width-modulator coupled to the adder to compare the difference signal to a reference signal and produce a pulse-width-modulated signal based on the comparing, a filter coupled to an output of the pulse-width-modulator, and a loop filter having a first input coupled to the output of the filter and a second input coupled to the input of the filter, the loop filter to generate a feedback signal by applying transfer functions to signals at its inputs. The loop transfer function of the amplifier is minimum aliasing error transfer function. The minimum aliasing error properties provide low distortion and taking the feedback from the output of the filter reduces high frequency output impedance.

Abstract: A signal converting system is described that has a multi-segment digital to analog converter coupled to one or more error shaping loops. Each error shaping loop includes a quantizer with a feedback loop configured to generate a control signal responsive to a stream of symbols and to an error signal. Each error shaping loop also includes an inter-symbol-interference (ISI) shaping loop coupled to receive the control signal and to produce an ISI portion of the error signal that is responsive to inter-symbol transition rate.

Abstract: In a method and an amplifier for the compensation of unlinearities e.g. of the class D type, wherein an audio signal is pulse-width modulated, e.g. with a carrier wave signal in the form of a triangular signal to provide a pulse-width modulated small-signal, the so-called multiplicative error signals, which occur prior to the provision of a pulse-width modulated great-signal (7), are detected in a detector (10)). It is noted that the carrier wave signal could be analog as well as digital. The signal from the detector, which is derived on the basis of differences between the pulse widths of the small-signals and the pulse widths of the great-signals, is used for changing the carrier wave signal so that the amplifier gets a constant gain in the entire audio range and is thereby linearized.

Abstract: A signal converting system is described that has a multi-segment digital to analog converter coupled to one or more error shaping loops. Each error shaping loop includes a quantizer with a feedback loop configured to generate a control signal responsive to a stream of symbols and to an error signal. Each error shaping loop also includes an inter-symbol-interference (ISI) shaping loop coupled to receive the control signal and to produce an ISI portion of the error signal that is responsive to inter-symbol transition rate.

Abstract: An embodiment of the invention provides one or more cascade circuits that are cascaded together to form a cascaded circuit. The cascaded circuit reduces noise at an analog output of the cascaded circuit. Each of the cascade circuits contains a noise-shaping circuit, a PCM (Pulse Code Modulation)-to-PWM (Pulse Width Modulation) converter and a 1-bit P-tap AFIR (Analog Finite Impulse Response) filter DAC. Noise at the output of the cascaded circuit may be further reduced by increasing the number of cascade circuits.

Abstract: An embodiment of the invention provides one or more cascade circuits that are cascaded together to form a cascaded circuit. The cascaded circuit reduces noise at an analog output of the cascaded circuit. Each of the cascade circuits contains a noise-shaping circuit, a PCM (Pulse Code Modulation)-to-PWM (Pulse Width Modulation) converter and a 1-bit P-tap AFIR (Analog Finite Impulse Response) filter DAC. Noise at the output of the cascaded circuit may be further reduced by increasing the number of cascade circuits.

Abstract: An error model can be utilized to mitigate errors associated with a conversion system, such as an analog-to-digital or digital-to analog converter. The error model is adaptively calibrated to approximate error characteristics associated with at least a portion of the conversion system, such as a digital-to analog converter. The error model can be generated on-line during system operation or off-line to improve performance of various types of signal converters and systems using such signal converters.

Abstract: A digital audio system including a digital audio amplifier with reduced AM interference. The digital audio amplifier includes a pulse-width-modulation (PWM) processor in which a digital datastream is upsampled by an interpolation filter. A sample rate converter resamples the upsampled datastream to produce a datastream at a converted sampling frequency, or PWM frame rate. The converted datastream is then applied to pulse-width-modulation circuitry which generates a PWM signal at the PWM frame rate. The sample rate converter resamples according to a sample rate conversion ratio associated with the AM tuned frequency. For example, the sample rate conversion ratio can be selected so that the PWM frame rate and its lower harmonics avoid an AM tuned frequency, any intermediate frequency in the AM tuner, and also an image frequency in the tuner.