Method and device for processing analogue ouput signals from capacity sensors

• US 20040174832A1
• Filed: 11/10/2003
• Published: 09/09/2004
• Est. Priority Date: 12/01/2000
• Status: Active Grant

• Current Assignee: Hahn-Schickard-Gesellschaft für angewandte Forschung e.V.
• Original Assignee: Hahn-Schickard-Gesellschaft für angewandte Forschung e.V.
• Inventors: Geiger, Wolfram, Niklasch, Norbert, Gaisser, Alexander
• Granted Patent: US 7,054,778 B2
• Time in Patent Office: Days
• US Class Current: 370/295
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719

Abstract

An analogue output signal of a sensor which comprises a carrier signal with a carrier frequency ω_C which is modulated by a measurement size is sampled with a sampling frequency ω_A to receive a sampled sensor output signal. The frequency ω_A of the sampling signal is set so that it is an integer divisor n of the carrier frequency ω_C, wherein the phase of the sampling signal is set so that the sampling signal is synchronous to the sensor output signal. The sampled sensor output signal is filtered now to remove periodically repeated signal components from the sampled sensor output signal. Then a filtered useful signal is received, wherein its amplitude is proportional to the measurand detected by the sensor.

Claims

1. Method for processing an analogue output signal (S4) of a sensor (100), wherein the analogue sensor output signal (S4) comprises a carrier signal having a carrier frequency ω

_C and being modulated by a measurand, wherein the method comprises;

sampling (126, 128) of the analogue sensor output signal (S4) using a sampling frequency ω

_A to obtain a sampled sensor output signal, wherein the sampling frequency ω

_A of the sampling signal is set to be an integer divisor n of the carrier frequency ω

_C, and wherein the phase of the sampling signal is set so that the sampling signal is synchronous to the carrier signal ω

_C.

2. Method according to one of the preceding claims, wherein the sampling signal is obtained by a synchronous frequency division of the carrier signal, wherein the carrier frequency ω

_C of the carrier signal is an integer multiple n of the sampling frequency ω

_A, with;

ω

_C=nω

_A.

3. Method according to one of the preceding claims, wherein the carrier frequency ω

_C of the carrier signal is set to a frequency which is higher or equal to 250 kHz.

4. Method according to one of the preceding claims, wherein the carrier frequency ω

_C of the carrier signal is higher than the frequency ω

_drive of the useful signal by a factor of 30-500.

5. Method according to one of the preceding claims, wherein the analogue sensor output signal (S4) is amplified analogously before the step of sampling.

6. Method according to one of the preceding claims, wherein the amplified analogue sensor output signal is high-pass filtered before the step of sampling to essentially remove low-frequency components of the signal (S4).

7. Method according to one of the preceding claims, wherein the analogue sensor output signal (S4) is amplitude-modulated by the measurand.

8. Method according to one of the preceding claims, wherein the measurand is a rotational rate.

9. Method according to one of the preceding claims, wherein the sensor (100) is a capacitive sensor.

10. Method according to claim 9, wherein the capacitive sensor (100) is a capacitive rotational rate sensor.

11. Method according to one of the preceding claims, wherein the carrier signals are fed into the sensor (100) at a center electrode of the same, wherein the sensor output signal is output to exterior electrodes of the sensor (100).

12. Method according to one of claims 1 to 10, wherein the carrier signals are fed into the sensor (100) at exterior electrodes of the same, wherein the sensor output signal is output at a common electrode (108) of the sensor.

13. Method according to one of the preceding claims, wherein the useful signal is input into a digital signal processor (130), wherein the digital signal processor outputs an analogue or a digital signal representing the measurand.

14. Device for processing an analogue output signal (S4) of a sensor (100), wherein the analogue sensor output signal (S4) comprises a carrier signal having a carrier frequency ω

_C and being modulated by a measurand, the device comprising;

a sampling device (126, 128) for sampling the analogue sensor output signal (S4) with a sampling frequency ω

_A to obtain a sampled sensor output signal, wherein the sampling frequency ω

_A of the sampling signal is set to be an integer divisor n of the carrier frequency ω

_C, and wherein the phase of the sampling signal is set so that the sampling signal is synchronous to the carrier signal.

15. Device according to claim 14, wherein the sampling device (100) is an analogue/digital converter having a sample &

hold member.