Abstract:
A differential delta-sigma-modulator has an integrator including a pair of single-ended amplifiers. A sample clock is driving a first switchable capacitor configuration and a second switchable capacitor configuration at a predetermined switching cycle. The first switchable capacitor configuration is adapted for sampling respective outputs from the pair of single-ended amplifiers on a pair of output sampling capacitors in the first part of the switching cycle. The second switchable capacitor configuration is adapted for charging a common mode capacitor with the average voltage of the voltage sampled by the pair of output sampling capacitors in the second part of the switching cycle. The voltage across the common mode capacitor represents the common mode voltage for the integrator.
Abstract:
An FSK transceiver for use in a hearing aid has means for automatic tuning of the transceiver frequency. The automatic tuning means comprises a phase difference detector and a tuning manager adapted to control the frequency of a resonant circuit of the FSK transceiver according to information received from the phase difference detector. The phase difference detector measures the phase difference across a component of the resonant circuit of the FSK transceiver. If the phase difference of a binary FSK symbol is equal to the phase difference of the opposite binary FSK symbol, the resonant circuit is tuned, otherwise the tuning manager performs a tuning procedure in order to minimize the difference in phase differences, and adjusts the frequency of the resonant circuit accordingly.
Abstract:
A hearing assistive device having an input transducer (18) for picking up sound from the environment, a digital signal processor (27) for alleviating a hearing loss of a specific user by compensating an audio signal according to the users hearing deficit, and an output transducer (29) for reproducing the compensated audio signal. The hearing assistive device further includes an integrated circuit component (40) having at least one analog-to-digital converter adapted for receiving an audio input signal from a microphone and providing a data output for signal processing. The at least one analog-to-digital converter includes an AC filter (50) preventing audible signal losses towards the microphone, and the AC filter (50) is provided with all components integrated in the integrated circuit component (40).
Abstract:
A hearing assistive device including an audio processing circuit with an analog-to-digital converter having an integrator integrating a voltage present in the summation point; a comparator comparing an output from the integrator with a reference voltage (Vref) and outputting a logical level in accordance with the comparison; a feedback loop coupling a feedback signal back to the summation point; and a reference voltage generation circuit being adapted to provide the reference voltage (Vref) being lower than a power supply voltage (Vbattery) and following the decay of the power supply voltage (Vbattery) with a predefined margin.
Abstract:
In a hearing aid (40), a direct-digital H-bridge output driver stage (1) driven by a sigma-delta modulator (2) is configured to operate in a power-saving three-level output mode or a power-consuming two-level output mode. The three-level output mode of the H-bridge output driver stage (1) has low power consumption but suffers the disadvantage of emitting capacitive noise potentially interfering with the reception of radio signals in a radio receiver (17) in the hearing aid (40). By providing a novel method of selecting the two-level output mode whenever the radio receiver (17) is receiving signals, and selecting the three-level output mode whenever the radio receiver (17) is idle, this capacitive interference does not disturb the radio receiver (17) in the hearing aid (40).The invention provides a method and a hearing aid.
Abstract:
In a monitoring device consisting of a reader and a data carrier, the reader (100) comprises a control unit (101), a memory (102), a digital signal generator (103), an output driver (104), resonance capacitors (105, 107) and a transmitter coil (106). The digital signal generator (103) is adapted for supplying a digital bit sequence selected among, at least two, bit sequences stored in the memory (102) whereby the strength of the magnetic field generated by the transmitter coil (106) can be varied dependent on the bit sequence selected by the control unit (101). The invention further provides a method of controlling the strength of a magnetic field generated by the reader of the monitoring device.
Abstract:
A digital receiver being adapted for receiving an MSK modulated signal, comprises a digital front-end unit (10) adapted for providing samples having a phase value (θmeasure) of a down-mixed signal, a phase compensation unit (11) adapted for compensating the phase value (θmeasure) by delivering a phase offset compensated sample having a phase value (θsync), and a coherent demodulator (12) adapted for recovering information content from the phase offset compensated sample. The phase compensation unit (11) is adapted for analyzing a phase value (θsync) of the phase offset compensated sample, calculating a phase offset value (θoffset) based on the phase value (θsync) of the phase offset compensated sample, and applying the phase offset value (θoffset) when delivering a subsequent phase offset compensated sample.
Abstract:
A frequency-shift-keying (FSK) transceiver for use in a hearing aid system and having a resonant circuit comprising a transceiver inductance (L1), said resonant circuit having a resonance frequency, and a transfer function where gain and phase are frequency dependent, wherein the transceiver comprises an FSK modulator receiving a data stream, and in response thereto outputting an FSK modulated signal to the resonant circuit for wirelessly transmission. The transceiver includes a controller monitoring the data stream received by the FSK modulator, and a phase equalizer unit controlled by the controller for substantially equalizing the phase distortion introduced by the frequency dependent resonant circuit. The invention also provides a hearing aid and a method of operating an FSK transceiver.
Abstract:
In order to minimize noise and current consumption in a hearing aid, an input converter including a first voltage transformer and an analog-to-digital converter of the delta-sigma type for a hearing aid is devised. The analog-to-digital converter of the input converter has an input stage, an output stage, and a feedback loop, and the input stage includes an amplifier (QA) and an integrator (RLF). The first voltage transformer (IT) has a transformation ratio such that it provides an output voltage larger than the input voltage and is placed in the input converter upstream of the input stage. A second voltage transformer (OT) having a transformation ratio such that it provides an output voltage larger than the input voltage, is optionally placed in the feedback loop of the converter. The voltage transformers (IT, OT) are switched-capacitor voltage transformers, each transformer (IT, OT) having at least two capacitors (Ca, Cb, Cc, Cd). The invention further provides a method of converting an analog signal.
Abstract:
A digital, three-level output driver (7) of the H-bridge variety for a hearing aid (20) obtains a reduced capacitive interference by providing a primary voltage (3) and a secondary voltage (8) for the output driver (7) and applying the secondary voltage (8) to both sides of the output driver (7) whenever the middle level of the three-level output driver (7) is present in the input signal for the output driver (7). The output driver (7) may be controlled from a pulse-width modulated signal, a sigma-delta pulse-density modulated signal, or a combination of those signals. The output driver (7) produces a clocked output signal consisting of a positive level, a negative level, and a zero level for driving an acoustic output transducer of the hearing aid (20). The invention provides a hearing aid (20) and a method of driving an output stage (7) of a hearing aid (20).