# US 5,952,879 A · Device for the simultaneous demodulation of a multifrequency signal, particularly for an eddy current measurement

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- Number: US 5,952,879 A
- Document ID: US5952879A
- Status: Granted
- Kind: A
- Application number: 08/981,377
- Filed: 1997-12-18
- Granted: 1999-09-14
- Earliest claimed: 1995-06-20
- Assignees: Intercontrole
- Inventors: Edouard de Ledinghen
- Web page: https://patentgrep.com/patent/US5952879A

## CPC

- H03D 3/006: {by sampling the oscillations and further processing the samples, e.g. by computing techniques (H03D3/007 takes precedence)}
- G01N 27/9046: {by analysing electrical signals}
- H03D: DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER (masers, lasers H01S; circuits capable of acting both as modulator and demodulator H03C; details applicable to both modulators and frequency-changers H03C; demodulating pulses H03K9/00; transforming types of pulse modulation H03K11/00; coding, decoding or code conversion, in general H03M; repeater stations H04B7/14; demodulators adapted for AC systems of digital information transmission H04L27/00; synchronous demodulators adapted for colour television H04N9/66)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A device for the simultaneous demodulation of a multifrequency signal comprising a processor in which demodulation takes place by calculation. An injector's output signal is multiplied by a complex signal having sinusoids of varying frequencies corresponding to frequency-shifted carriers, thereby transposing the injector's signal on intermediate frequencies.

## Claims

### Claim 1

Device for the simultaneous demodulation of a multifrequency signal, comprising a processor, where the demodulation takes place by calculation, comprising an injector, whose output signal is multiplied by a complex signal in the following form: ##EQU3## .epsilon..sub.1 being a small frequency deviation and .alpha..sub.1 a phase, the frequencies of the N sinusoids being the frequencies of the frequency-shifted carriers, so as to transpose the signal of the injection on the intermediate frequencies.

### Claim 2 (depends on 1)

Device according to claim 1, comprising said injector followed by a multiplier and a low-pass filter, and said filter, having an antialiasing function, is followed by a digital converter.

### Claim 3 (depends on 1)

Device according to claim 1, which is used for a measurement by eddy currents.