Abstract:
An improved method and apparatus for detecting and measuring one or more biometric parameters of a user using a computing device in conjunction with an electroacoustic (audio) transducer is described. A first mode in which the audio transducer produces sound is disabled, and the device is placed in a second mode of operation in which a biometric signal is recovered from the transducer using a “back” audio signal. The biometric signal may then be measured or analyzed. The first mode is disabled by temporarily creating a high impedance between circuitry producing the audio signal and the transducer, while the biometric parameter is measured. This allows for detection of the biometric event without the need for significant additional components or circuitry. The computing device may most conveniently be a smartphone, but the approach described herein may also be easily and usefully applied to tablets, laptop or desktop computers or other devices.
Abstract:
An improved system and method for reducing the ambient noise experienced by a user listening to an earpiece without the use of a microphone is disclosed. An “ambient noise signal” created by the sound pressure wave of the ambient noise acting on the earpiece transducer is obtained. In some embodiments, the ambient noise signal is inverted and fed back, and the inverted signal is added to the intended audio signal being sent to the earpiece so that the ambient noise is cancelled. In other embodiments, a processor receives the ambient noise signal and predicts the modification to the intended audio signal needed to counteract the ambient noise. The ambient noise signal may be obtained by comparing the actual signal across the earpiece transducer to the intended audio signal, or by detecting variations in the current across the transducer from the current generated to drive the transducer.
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. Another circuit implements a multiplying element and digital-to-analog converter with selective enablement of duplicate current source devices. Another circuit implements a multiplying element and digital-to-analog converter with variable effective length of the digital-to-analog converter. In one such circuit one or more current sources of a multiplier element are deselected to remove a noise contribution of the multiplier element, as described herein. A complex filter circuit includes a pair of real finite impulse response filter circuits performing addition and subtraction in current domain, sharing a common resistor network to perform weighted addition. One such circuit further includes a second pair of real finite impulse response filter circuits performing addition and subtraction in current domain, sharing a second common resistor network to perform weighted addition.
Abstract:
A method and system for generating and matching complex series and/or parallel combinations of nominally identical initial elements to achieve an arbitrary compound value is disclosed. A recursive algorithm successively adds one or more similar nominal two-terminal elements to generate a series and/or parallel compound combination of nominal elements, the compound combination having a desired impedance. The compound value, and thus the ratio between two compound values, can be determined to almost any desired degree of accuracy, with potential errors greatly reduced from those typical in the construction of individual elements of different values. Since the initial elements are nominally identical, the compound value, and the ratio between values, depends primarily upon the connections of the initial elements, rather than their geometry, and thus remain virtually constant regardless of variations in the manufacturing process.
Abstract:
A delay circuit in which the delay is independent of variations in the power supply which powers the logic gates of the delay circuit is disclosed. By separating the CMOS transistors that form each logic gate by additional CMOS bias transistors which are biased at a controlled voltage, variations in the gate delay of the inverter transistors due to variations in the power supply voltage for the inverter transistors may be minimized. In one embodiment, the constant bias voltage may be provided by a constant current source comprising a series of amplifiers each having a gain significantly less than one connected to a triple cascode.
Abstract:
A method and system is disclosed in which the phase detector in a phase-locked loop is able to run at the fastest speed appropriate for a reference signal. A frequency offset is added, to the output frequency of the phase-locked loop, to alter the frequency fed to the frequency divider which would receive the output frequency in a conventional PLL to an intermediate frequency. The frequency offset is selected so that the ratio of the intermediate frequency to the reference frequency is a simple fraction, and preferably an integer, i.e., the intermediate frequency is a multiple of the reference frequency. In cases where the relationship between the output frequency and the reference frequency is largely relatively prime, the phase detector is thus able to receive signals at the frequency of the reference signal and operate at the fastest speed appropriate for the reference signal.
Abstract:
A digitally controlled oscillator (DCO) that generates an output frequency clock signal without drift and can be rapidly locked to an input or reference clock is described. A variable-modulus-fixed-increment form of DCO is configured to divide the frequency of a nominally fixed frequency oscillator. A constant is derived from the ratio of a fixed increment to the desired output frequency; this constant is multiplied by the frequency of the oscillator and the modulus adjusted to keep the ratio of the input clock and the output clock constant. The frequency of the oscillator is conveniently measured by counting the number of cycles between input cycles of a reference frequency. The oscillator must be greater in frequency than the expected output and is most accurate in cases where the reference frequency is low compared to the expected output frequency.
Abstract:
A digitally controlled oscillator (DCO) that generates an output frequency clock signal without drift and can be rapidly locked to an input or reference clock is described. A variable-modulus-fixed-increment form of DCO is configured to divide the frequency of a nominally fixed frequency oscillator. A constant is derived from the ratio of a fixed increment to the desired output frequency; this constant is multiplied by the frequency of the oscillator and the modulus adjusted to keep the ratio of the input clock and the output clock constant. The frequency of the oscillator is conveniently measured by counting the number of cycles between input cycles of a reference frequency. The oscillator must be greater in frequency than the expected output and is most accurate in cases where the reference frequency is low compared to the expected output frequency.
Abstract:
A system and method for passively balancing electroacoustic transducers so that sounds other than the transducer's output can be detected. A transducer producing audio output based upon an input audio signal can operate in reverse to produce a signal in response to the impact of external sound upon the transducer from another source. This “reverse” or “microphone” signal represents the sound from the other source. Transducers are operated in monophonic mode, each in opposite polarity to the other thus canceling out and leaving only the microphone signal created by the transducers, i.e., a signal representing the external sound. The microphone signal can be amplified, and can be filtered and processed to identify and/or obtain various types of information about the sound received by the transducers.
Abstract:
A system and method for passively balancing electroacoustic transducers so that sounds other than the transducer's output can be detected. A transducer producing audio output based upon an input audio signal can operate in reverse to produce a signal in response to the impact of external sound upon the transducer from another source. This “reverse” or “microphone” signal represents the sound from the other source. Transducers are operated in monophonic mode, each in opposite polarity to the other thus canceling out and leaving only the microphone signal created by the transducers, i.e., a signal representing the external sound. The microphone signal can be amplified, and can be filtered and processed to identify and/or obtain various types of information about the sound received by the transducers.