Method and device for analog digital converting a signal including a low-frequency component

An analog/digital converter device for analog/digital converting of at least one analog low-frequency signal, comprising

• an analog intermediate signal generating unit for generating an analog intermediate signal using the analog low-frequency signal, which has at least one frequency component below a predetermined border frequency value,
• and at least one analog high-frequency signal, which has a frequency above the predetermined border frequency value,
• wherein the generated analog intermediate signal has a characteristic analog feature which makes it possible to determine the analog low-frequency signal from the analog intermediate signal,
• an analog/digital converter for converting an analog signal into a digital signal, which is connected to an output of the analog intermediate signal generating unit so that the analog intermediate signal is input into the analog/digital converter so that a digital intermediate signal is generated, wherein the analog/digital converter is able to capture only an analog signal with a frequency above the predetermined border frequency value, and the digital intermediate signal has a characteristic digital feature which makes it possible to determine a digital low-frequency signal from the digital intermediate signal,
• a low-frequency determination unit for determining the digital low-frequency signal from the digital intermediate signal using the characteristic digital feature, the low-frequency determination unit being connected to an output of the analog/digital converter.

An analog intermediate signal generating unit to be connected to an analog/digital converter which can capture and convert only an analog signal with a frequency above a predetermined border frequency value of said analog/digital converter, said analog intermediate signal generating unit being provided for processing an analog low-frequency signal which has at least one frequency component below the predetermined border frequency value, said low frequency component being such that the analog low-frequency signal, when captured and-converted by said analog/digital converter without said frequency component, cannot be reconstructed from an output signal of the analog/digital converter,

• said analog intermediate signal generating unit comprising
• an input for said analog low-frequency signal,
• an input for an analog high-frequency signal which has a frequency above the predetermined border frequency value,
• a processing unit for carrying out a linear or non linear operation on the analog low-frequency signal and the analog high-frequency signal, and
• an output for providing an analog intermediate signal which is produced by said operation and which has sufficient frequency components above the predetermined border frequency value so that it is possible to reconstruct the analog low-frequency signal from a digital output signal of the analog/digital converter resulted from the capturing and converting said analog intermediate signal by said analog/digital converter.