Abstract: A circuit and method is disclosed for filtering an audio signal. The circuit has a first quadrature source and multipliers for multiplying the input signal by the I and Q outputs of the quadrature source. The multiplied inputs are then passed through a pair of low pass filters, which may have an adjustable Q factor. The outputs of the low pass filters are then multiplied in a second pair of multipliers by the I and Q outputs, respectively, of a second quadrature source, which will typically be of the same frequency, but different amplitude and phase, of the first quadrature source. The twice-multiplied signals are then summed by an adder to provide an output signal. The circuit may be modified to include a companding circuit between the low pass filters and the second pair of multipliers that determines the amplitude of the input signal, filters it, and compands the signal in a compandor. The compandor may have adjustable parameters.

Abstract: A method for determining a physiological parameter comprises receiving measured physiological data, parsing the measured physiological data into a plurality of time windows, each time window including a plurality of samples of the physiological data, fitting each of the plurality of time windows to a mathematical function utilizing a fitting function to obtain a plurality of sets of fit parameters, each set associated with a one of the plurality of time windows, and based on the plurality of sets of fit parameters, determining a physiological parameter.

Abstract: An apparatus and method are disclosed for providing output signal swings that are greater than the supply voltage in a class-D amplifier. The amplifier circuit boosts the voltage across the amplifier load, such as a loudspeaker, by using capacitors to “charge pump” the voltage across the load and thus increase the voltage temporarily. This is done by using two or more output bridges rather than one, and connecting the bridges through the capacitors. For signals of less than the supply voltage, only an inner bridge, similar to a full bridge of the prior art, operates. For signals above the supply voltage, an outer bridge charges capacitors, which are then used to ‘boost’ the voltage on the bridge output for the short period of the Class-D switching period. Thus, only relatively small value boosting capacitors are needed, as they do not need to supply charge for very long.

Abstract: A method and system for designing and implementing a finite impulse response (FIR) filter to create a plurality of output signals, each output signal having the same frequency but at a different phase shift from the other output(s), is described. Values are determined for the resistors, or other elements having impedance values, in a FIR filter having a plurality of outputs, such that each output has the same frequency response but a different phase than the other output(s). This is accomplished by the inclusion of a phase factor in the time domain calculation of the resistor values that does not change the response in the frequency domain. The phase shift is constant and independent of the frequency of the output signal.

Abstract: A circuit and method is disclosed for filtering an audio signal. The circuit has a first quadrature source and multipliers for multiplying the input signal by the I and Q outputs of the quadrature source. The multiplied inputs are then passed through a pair of low pass filters, which may have an adjustable Q factor. The outputs of the low pass filters are then multiplied in a second pair of multipliers by the I and Q outputs, respectively, of a second quadrature source, which will typically be of the same frequency, but different amplitude and phase, of the first quadrature source. The twice-multiplied signals are then summed by an adder to provide an output signal. The circuit may be modified to include a companding circuit between the low pass filters and the second pair of multipliers that determines the amplitude of the input signal, filters it, and compands the signal in a compandor. The compandor may have adjustable parameters.

Abstract: An apparatus and method are disclosed for providing output signal swings that are greater than the supply voltage in a class-D amplifier. The amplifier circuit boosts the voltage across the amplifier load, such as a loudspeaker, by using capacitors to “charge pump” the voltage across the load and thus increase the voltage temporarily. This is done by using two or more output bridges rather than one, and connecting the bridges through the capacitors. For signals of less than the supply voltage, only an inner bridge, similar to a full bridge of the prior art, operates. For signals above the supply voltage, an outer bridge charges capacitors, which are then used to ‘boost’ the voltage on the bridge output for the short period of the Class-D switching period. Thus, only relatively small value boosting capacitors are needed, as they do not need to supply charge for very long.

Abstract: An apparatus and method are disclosed for providing output signal swings that are greater than the supply voltage in a class-D amplifier. The amplifier circuit boosts the voltage across the amplifier load, such as a loudspeaker, by using capacitors to “charge pump” the voltage across the load and thus increase the voltage temporarily. This is done by using two or more output bridges rather than one, and connecting the bridges through the capacitors. For signals of less than the supply voltage, only an inner bridge, similar to a full bridge of the prior art, operates. For signals above the supply voltage, an outer bridge charges capacitors, which are then used to ‘boost’ the voltage on the bridge output for the short period of the Class-D switching period. Thus, only relatively small value boosting capacitors are needed, as they do not need to supply charge for very long.

Abstract: A circuit component that is adjustable at run time and a method of designing the circuit are disclosed. The component contains a hierarchy of recursive levels in which a bottom level is a compound element made from two connected simple elements, and each higher level contains two compound elements connected in the same fashion. The described circuit allows for a large number of available values of the component value to be arranged in a logarithmic fashion rather than a linear one as in the prior art, thus generally reducing errors between any desired value for the component and the available values. In addition, such compound elements reduce the power dissipated by the analog element and the susceptibility to noise as compared to prior art adjustable components without adversely affecting the overall gain of the circuit.

Abstract: A system and method is disclosed for placing some of the elements of a FIR filter into a high impedance state in certain situations. When it is detected that the signal to an impedance element is the same as the previous value, then the driver of that impedance element is “turned off” or goes into a high impedance state, so that no current flows through that impedance element, and it no longer contributes to the filter output. Alternatively, if the impedance elements are the same between two adjacent taps of the delay line, the driver of one of those impedance elements may be turned off or go into a high impedance state. The technique may be particularly useful in differential output filters. Turning off a driver effectively removes the attached impedance element from the filter and reduces current flow and power consumption, thus extending battery life in mobile devices.

Abstract: A circuit component that is adjustable at run time and a method of designing the circuit are disclosed. The component contains a hierarchy of recursive levels in which a bottom level is a compound element made from two connected simple elements, and each higher level contains two compound elements connected in the same fashion. The described circuit allows for a large number of available values of the component value to be arranged in a logarithmic fashion rather than a linear one as in the prior art, thus generally reducing errors between any desired value for the component and the available values. In addition, such compound elements reduce the power dissipated by the analog element and the susceptibility to noise as compared to prior art adjustable components without adversely affecting the overall gain of the circuit.

Abstract: A circuit and method for lowering noise in an audio rendering system is described. An analysis is made of the spectral content of an audio signal, i.e., the frequencies it contains, over a certain time interval. Cutoff frequencies of high pass and low pass filters that pass the audio signal are then adjusted for each interval by changing the effective values of adjustable impedance elements in the filters, so that the bandwidth of the system is adjusted to be what is sufficient to pass any frequencies in the resulting analog audio signal during any given time interval, rather than requiring the entire 20 kHz audio spectrum to be constantly present.

Abstract: An apparatus and method are disclosed for providing output signal swings that are greater than the supply voltage in a class-D amplifier. The amplifier circuit boosts the voltage across the amplifier load, such as a loudspeaker, by using capacitors to “charge pump” the voltage across the load and thus increase the voltage temporarily. This is done by using two or more output bridges rather than one, and connecting the bridges through the capacitors. For signals of less than the supply voltage, only an inner bridge, similar to a full bridge of the prior art, operates. For signals above the supply voltage, an outer bridge charges capacitors, which are then used to ‘boost’ the voltage on the bridge output for the short period of the Class-D switching period. Thus, only relatively small value boosting capacitors are needed, as they do not need to supply charge for very long.

Abstract: An apparatus and method are disclosed for providing output signal swings that are greater than the supply voltage in a class-D amplifier. The amplifier circuit boosts the voltage across the amplifier load, such as a loudspeaker, by using capacitors to “charge pump” the voltage across the load and thus increase the voltage temporarily. This is done by using two or more output bridges rather than one, and connecting the bridges through the capacitors. For signals of less than the supply voltage, only an inner bridge, similar to a full bridge of the prior art, operates. For signals above the supply voltage, an outer bridge charges capacitors, which are then used to ‘boost’ the voltage on the bridge output for the short period of the Class-D switching period. Thus, only relatively small value boosting capacitors are needed, as they do not need to supply charge for very long.

Abstract: An apparatus and method are disclosed for providing output signal swings that are greater than the supply voltage in a class-D amplifier. The amplifier circuit boosts the voltage across the amplifier load, such as a loudspeaker, by using capacitors to “charge pump” the voltage across the load and thus increase the voltage temporarily. This is done by using two or more output bridges rather than one, and connecting the bridges through the capacitors. For signals of less than the supply voltage, only an inner bridge, similar to a full bridge of the prior art, operates. For signals above the supply voltage, an outer bridge charges capacitors, which are then used to ‘boost’ the voltage on the bridge output for the short period of the Class-D switching period. Thus, only relatively small value boosting capacitors are needed, as they do not need to supply charge for very long.

Abstract: An apparatus is disclosed for providing a common mode voltage to the inputs of a first differential amplifier which outputs the difference between two signals. A second differential amplifier receives the output of the first differential amplifier, and the output of the second differential amplifier is fed back to the inputs of the first differential amplifier as a common mode voltage. Since both inputs of the first differential amplifier receive the fed back common mode voltage, the first differential amplifier still outputs only the difference in the two signals, but the presence of the common mode voltage allows the first differential amplifier to operate with lower noise if the voltage levels of the inputs to the first differential amplifier vary. The second differential amplifier may be of significantly lower quality and cost than the first differential amplifier, without affecting the performance of the first differential amplifier.

Abstract: Channel select filter circuits are described. One circuit implements a multiplying element and digital-to-analog converter as a differential current mode device. Another circuit implementing a multiplying element and digital-to-analog converter with weighted addition, deferred after multiplication of the digital-to-analog converter and multiplier combination. In one such circuit, substantially equal current source magnitudes are in different columns of the circuit. Another such circuit, with substantially equal current source magnitudes, uses non-radix2. Another such circuit, with substantially equal current source magnitudes, has partial segmentation. Another circuit implements a multiplying element and digital-to-analog converter, with partial segmentation, scrambling bit allocation for elements. One such circuit scrambles bit allocation on equally weighted segments, as described herein.

Abstract: An apparatus is disclosed for inputting digital data on the output channel(s) of an audio subsystem in an audio device, without interfering with normal operation of the audio subsystem. The described circuit includes a resistive element in parallel with the expected load device, such as a headphone or speaker. The resistive element receives a modulated digital signal from a data source or a switch, and the instantaneous current through the resistive element due to the modulated digital signal is reflected in a current feedback mechanism of the audio subsystem. Demodulation logic retrieves the digital signal from the current measured by the current feedback mechanism. A capacitor is provided to prevent the current in the resistive element from the digital signal from impacting the average DC current that the feedback mechanism uses to evaluate the load device.

Abstract: A voltage regulator for providing a constant voltage to a circuit is described in which a series regulator acts as the current source for a shunt regulator and the series regulator in turn is controlled by the current diverted from the output by the shunt regulator. The current being diverted by the shunt regulator is measured, either directly or by measuring a related operating parameter. When current below or above a certain desired amount is being diverted from the load by the shunt regulator, a signal is sent to the series regulator causing the series regulator to provide more or less current respectively, so that the shunt regulator again diverts the desired amount of current and the output voltage remains constant. This configuration results in efficiency near that of a series regulator while maintaining the better frequency response of a shunt regulator.

Abstract: An improved method for the placement and routing of compound elements, each comprising a series/parallel combination of nominally identical elements, is disclosed. The method treats each compound element as a separate cell (the sub-circuit construct commonly used in silicon chip design) so as to treat as a unit all the nominally identical elements that make up a compound value, and place them as a single group in the design of a chip. This results in the compound elements being placed as units and routed in such a way that all of the nominal elements are located together and any effects between compound values are thus relatively localized and optimally isolated.

Abstract: A method and system for designing and implementing a finite impulse response (FIR) filter to create a plurality of output signals, each output signal having the same frequency but at a different phase shift from the other output(s), is described. Values are determined for the resistors, or other elements having impedance values, in a FIR filter having a plurality of outputs, such that each output has the same frequency response but a different phase than the other output(s). This is accomplished by the inclusion of a phase factor in the time domain calculation of the resistor values that does not change the response in the frequency domain. The phase shift is constant and independent of the frequency of the output signal.