Pulse or digital communications – Receivers – Interference or noise reduction
Reexamination Certificate
1998-08-13
2001-11-20
Corrielus, Jean (Department: 2631)
Pulse or digital communications
Receivers
Interference or noise reduction
C375S285000, C375S340000, C455S063300
Reexamination Certificate
active
06320918
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention refers to a procedure for reducing interference in the transmission of an electrical communication signal which preferably is a voice signal but which could also be a data signal. In the transmission of voice signals over faulty channels, the voice signals are generally superimposed with additional interference. This interference can have different causes, for example crosstalk on lines, interference from power transmission lines, bit errors or burst errors in the case of digital transmission routes or echoes on the lines. The faulty signals caused by this interference can take on such great amplitudes that the audibility of the voice on the received voice signal is decreased significantly.
2. Discussion of Related Art
To reduce the faulty parts of a voice signal which has been received with interference, it is generally well known that band-stop filters can be used which suppress the interference in a particular frequency range. In this, the disadvantage is that parts of the frequency of the voice signal are also suppressed.
If the faulty signal can be established over a great amplitude which exceeds a certain threshold, for example in the HF or ZF demodulator range of the receiver, then the output signal can be switched to silent. Such a procedure is used, for example, in UKW radio receivers and amateur devices.
In addition, it is known in the case of a statistically steady-state noise how to estimate and buffer the noise in the voice breaks and to subtract the noise spectrum from this noise during speech, as in W. Reich: Adaptive systems for the reduction of environmental noise in voice transmissions, Dissertation at the Institute for Communication Technology, the University of Karlsruhe, 1985. In the described procedure, the time function of the voice is transformed by means of a Fast-Fourier transformation into a frequency spectrum; the frequency spectrum is analyzed with regard to unwanted noise and transformed back for further processing in the time range. Due to the multiple Fast-Fourier transformation, this procedure demands great computer input. In addition, disturbance within the voice spectrum cannot be recognized.
SUMMARY OF THE INVENTION
The invention now solves the task of finding a procedure for reducing interference in a communication message which compared to the known state of the art can be achieved with a lower computer input and which is not limited to the reduction of steady-state or quasi-steady state interference but is also suited to the reduction of shorter, non-steady interference.
According to the present invention, a procedure for reducing interference of an electrical communication signal is characterized by the following procedural steps: the communication signal received as a faulty time function is fed to at least one memory as well as at least one detector, the communication signal is stored in the memory and analyzed in the detector with regard to interference signal characteristics, a signal type is recognized by the detector and then the time range is established in which the interference signal occurred, the stored signal is read out from the memory and in the time range of the interference signal a suppression method is selected dependent on the type of interference signal, using which the interference signal and the recognized interference signal type are processed so that an interference-free communication signal is achievable.
The nature of the invention is that the suppression method is selected dependent on the interference signal type. In addition, the interference in a received communication signal are analyzed with regard to characteristics in the time range and classified as clicks, crackles, rumbles or noise interference signals and the time of their occurrence is marked. Dependent on the interference signal type, a blanking out of the interference signal and/or an interpolation of the communication signal and/or a subtraction of the interference signal from the communication signal and/or a regeneration, i.e. the replacement of the interference signal with a usable signal takes place.
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Matt Hans Jurgen
Trompf Michael
Walker Michael
Alcatel
Corrielus Jean
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