Coded data generation or conversion – Analog to or from digital conversion – Analog to digital conversion
Reexamination Certificate
2002-07-02
2004-04-20
Young, Brian (Department: 2838)
Coded data generation or conversion
Analog to or from digital conversion
Analog to digital conversion
C341S126000, C341S156000
Reexamination Certificate
active
06724337
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an analog/digital converter device for analog/digital converting of at least one analog low-frequency signal and to a method for analog/digital converting of at least one analog low-frequency signal.
A multimedia computer generally includes a sound card for converting a captured analog speech signal, which is input into the computer by a user via a microphone or a line-in-jack, into a digital signal, which digital signal may further be processed by a processing unit, e.g. a microprocessor. For converting the analog signal into a digital signal, an analog/digital converter in the sound card is provided.
However, many of the available sound cards attenuate substantially or even cut off components of the analog signal before the signal is applied to the analog/digital converter for being digitized. Usually, such a sound card has a predetermined border frequency value. The common sound card thus cannot usually detect and process an analog signal with a frequency below this predetermined border frequency value, e.g. it is not possible to capture and process an analog signal with direct-current (DC) signal components. An example of the border frequency value is a frequency of 20 Hz, i.e. many sound cards cannot capture and process an analog signal in a frequency range between 0 Hz and 20 Hz.
Though an audio analog signal usually has a frequency which is above that border frequency value of e.g. 20 Hz, a problem arises when the sound card is intended to be used as well for measurement of non-audio analog signals, as an analog low-frequency signal having frequency components below the predetermined border frequency value cannot be entirely captured by the sound card, since only an analog high-frequency signal which has frequency components only above the predetermined border frequency value and within the frequency range of the sound card can entirely be captured.
An “analog low-frequency signal” in this description means a signal with at least one important frequency component below the predetermined border frequency value of the sound card. “Important frequency component” in this context means that the capturing and processing of such a signal by the sound card, or more generally by an analog/digital converter, would result in an output signal from which the input analog low-frequency signal cannot be reconstructed. Accordingly, an analog low-frequency signal can be e.g. a DC signal or a signal with one or more important frequency components below the predetermined border frequency of the sound card.
Thus, it is not possible to use such a sound card for measurement of analog low-frequency signals.
U.S. Pat. No. 5,987,541 discloses a computer system with a sound card. In this system, the sound card includes a modulation interface for modulation/demodulation of a digitized speech signal on/from a carrier signal of a predetermined frequency. Thus, an analog speech signal is detected by the sound card, converted into a digitized speech signal and modulated on the carrier signal. This is to use different frequency channels on a computer bus for being used by different peripheral devices at the same time. However, with this computer system, if it is used in the scenario described above, measurement of an analog low-frequency signal is still impossible due to the border frequency of the sound card.
SUMMARY OF THE INVENTION
Thus, it is one object of the invention to provide a method for analog/digital converting of at least one analog low-frequency signal with an analog/digital converter which can capture only an analog signal with a frequency within a frequency range above a predetermined border frequency value.
This object is achieved with a method for analog/digital converting of at least one analog low-frequency signal with an analog/digital converter which can capture and convert only an analog signal with a frequency above a predetermined border frequency value, in which at least one analog low-frequency signal and at least one analog high-frequency signal are provided. The analog low-frequency signal is a signal with at least one important frequency component below the predetermined border frequency value according to the above definition, such as a non-audio low-frequency signal or even a direct-current signal, which is to be converted by the analog/digital converter. The analog high-frequency signal is an analog signal having only frequency components above the predetermined border frequency value and within the frequency range of the analog/digital converter. Using the analog low-frequency signal and the analog high-frequency signal, an analog intermediate signal is generated, the analog intermediate signal having a characteristic analog feature with which it is possible to reconstruct the analog low-frequency signal from the analog intermediate signal. In a further step, the analog intermediate signal is converted into a digital intermediate signal, i.e. the analog intermediate signal is digitized in the analog/digital converter. This digitizing is done e.g. by sampling the analog intermediate signal. The thus generated digital intermediate signal has a characteristic digital feature, which makes it possible to determine a digital low-frequency signal from the digital intermediate signal. This characteristic digital feature simply may be the digitized characteristic analog feature. In a last step, the desired digital low-frequency signal is determined from the digital intermediate signal using the characteristic digital feature.
It should be noted that the analog intermediate signal may also have frequency components below the predetermined border frequency value. However, it must have sufficient frequency components above the predetermined border frequency value so that it is possible to reconstruct the analog low-frequency signal from the digitized low-frequency signal after the analog intermediate signal has been captured and digitized by the analog/digital converter and the digital low-frequency signal is determined from the digital intermediate signal.
Therefore, according to the invention it is possible to process, i.e. also to capture and convert, at least one analog low-frequency signal with at least one important frequency component below the predetermined border frequency value of the analog/digital converter.
Furthermore, it is a further object of the invention to provide an analog/digital converter device for analog/digital converting of at least one analog low-frequency signal, the analog/digital converter device being able to process an analog low-frequency signal using an analog/digital converter which can detect only an analog signal with a frequency above a predetermined border frequency value, wherein the analog low-frequency signal has at least one important frequency component below the predetermined border frequency value.
This object is achieved with an analog/digital converter device comprising an analog intermediate signal generating unit. With this analog intermediate signal generating unit, the at least one analog low-frequency signal is mixed with a corresponding analog high-frequency signal.
In this context, when mixing the two signals, one may
add the two signals,
subtract the two signals,
multiply the two signals, or
convolve the two signals.
In general, in this context, the mixing may be any linear or non-linear operation, which is processed on the two signals, as far as this operation results in an analog intermediate signal which fulfills the above explained requirements.
The resulting analog intermediate signal generated by the analog intermediate signal generating unit is input to an analog/digital converter which has a predetermined border frequency value, below which the converter attenuates or cuts off frequencies of the input analog signal. That is, the input of the analog/digital converter is connected to the output of the analog intermediate signal generating unit.
By means of the analog/digital converter, the analog intermediate signal is digitized, i.e. for example sampled, thereby ge
Addest Technovation Pte Ltd
Andras Joseph C.
Myers Dawes Andras & Sherman LLP
Nguyen John
Young Brian
LandOfFree
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