SIGNAL CONDITIONER WITH SUPPRESSION OF INTERFERING SIGNALS
A semiconductor die with an integrated circuit providing a signal conditioner ( 106 ) for a capacitive transducer ( 105 ), comprising: a gain stage ( 101 ) configured to receive an analogue transducer signal; an analogue-to-digital converter ( 102 ) coupled to receive a signal outputted from the gain stage ( 101 ) and to provide a digital signal. A feedback signal is provided via a digital-to-analogue converter ( 104 ) and a digital signal processor ( 103 ) that receives the digital signal; and the gain stage ( 101 ) is configured with a first input ( 107 ) and second input ( 108 ) coupled to receive the analogue transducer signal and the feedback signal, respectively.
1 . A semiconductor die with an integrated circuit providing a signal conditioner for a capacitive transducer, comprising:
a gain stage configured to receive an analogue transducer signal on a first input and a feedback signal on a second input;
an analogue-to-digital converter coupled to receive an output signal of the gain stage and to provide a digital signal,
the feedback signal is provided via a digital-to-analogue converter and a digital signal processor receiving the digital signal characterized in that:
a latency or time delay through a feedback loop or path, formed from an input of the analogue-to-digital converter to the feedback signal at the second input of the gain stage, is smaller than 50 μS.
2 . A semiconductor die according to claim 1 , wherein a resolution of the digital-to-analogue converter is higher than a resolution of the analogue-to-digital converter.
3 . A semiconductor die according to claim 2 , wherein the resolution of the digital-to-analogue converter in an audio bandwidth between 20 Hz and 20 kHz is more than 6 dB, or more than 10 dB, or more than 20 dB higher than the resolution of the analogue-to-digital converter.
4 . A semiconductor die according to claim 1 , wherein the digital-to-analogue converter is operated at a higher clock frequency than the analogue-to-digital converter.
5 . A semiconductor die according to claim 1 , wherein at least one of the analogue-to-digital converter and the digital-to-analogue converter is operated at an over-sampled sampling rate.
6 . A semiconductor die according to claim 5 , wherein the over-sampled sampling rate is higher than 48 kHz.
7 . A semiconductor die according to claim 1 , wherein the gain stage is configured as an integrator.
8 . A semiconductor die according to claim 1 , wherein an open loop small signal gain of the gain stage is larger than 40 dB at 20 Hz.
9 . A semiconductor die according to claim 1 , wherein the gain stage comprises a differential input stage having respective input terminals separately connected to the feedback signal and the analogue transducer signal.
10 . A semiconductor die according to claim 1 , wherein the digital signal processor comprises a digital high-pass filter.
11 . A semiconductor die according to claim 1 , wherein the digital signal processor is configured with a digital low-pass filter and the digital low-pass filter is controlled in response to the input signal.
12 . A semiconductor die according to claim 1 , wherein the digital signal processor comprises a signal estimator configured to:
estimate an amplitude and/or phase of a dominating signal component of the transducer signal,
a signal generator controlled by the signal estimator to generate the feedback signal with an amplitude and/or phase determined on basis of the amplitude and/or phase of the dominating signal component.
13 . A semiconductor die according to claim 12 , wherein the signal estimator is configured to detect a time duration of the dominating signal component.
14 . A. semiconductor die according to claim 13 , wherein the signal estimator is configured to detect a time duration of the dominating signal component by performing an analysis over periods of time longer than an expected duration of voiced cues of human speech.
15 . A semiconductor die according to claim 12 , wherein the signal estimator is configured to detect the time duration of the dominating signal component by auto-correlation or spectral analysis.
16 . A semiconductor die according to claim 14 , wherein the signal estimator is adapted to control the amplitude and/or phase of the feedback signal based on detected time durations of the dominating signal component.
17 . A semiconductor die according claim 1 , wherein the digital signal processor is configured with an adaptive filter to suppress a component of the input signal that has autocorrelation values about equidistant delays, where the autocorrelation values significantly represent a persisting oscillation in the signal input to the signal processor.
18 . A semiconductor die according to claim 1 , wherein at least one of the analogue-to-digital converter and the digital-to analogue converter comprises a single level or multi-level sigma-delta converter.
19 . A semiconductor die according to claim 1 , wherein the first input of the gain stage has an input impedance larger than 1 GΩ, such as larger than 10 GΩ, or preferably larger than 100 GΩ.
20 . An electroacoustical transducer comprising a semiconductor die according to claim 1 arranged inside a transducer housing; and
a transducer element disposed inside the transducer housing and operatively connected to the first input of gain stage to supply the analogue transducer signal.
21 . An electroacoustical transducer according to claim 20 , where the transducer element comprises a capacitive transducer element.
22 . (canceled)