Method for eliminating radio frequency interference in signal and communication system thereof

Abstract

The present application relates to a method for eliminating radio frequency interference in a signal and a communication system thereof. In the communication system, after a received analog signal is converted into a digital signal in the frequency domain, it will carry radio frequency interference. The signal continues to be processed by an equalizer and a far-end crosstalk eliminator. At this time, in order to avoid the problem of erroneous signals caused by notches generated therein, the proposed method for eliminating radio frequency interference in the signal is to correct the masking parameters of the equalizer and the far-end crosstalk eliminator, and adopt a method of not processing the frequency band detected with radio frequency interference, that is, masking the corresponding bin after fast Fourier transformation to the frequency domain, and then outputting the signal to the radio frequency interference eliminator for radio frequency interference elimination. Finally, the communication system obtains a digital signal with radio frequency interference eliminated.

Description

Technical Field

[0001] The present application relates to a technology for eliminating signal interference, and in particular to a method and a communication system for eliminating radio frequency interference by masking a frequency band affected by radio frequency interference to avoid the influence of notch. Background Art

[0002] A wireless communication system may encounter various interferences during operation. For example, the equalizer is a very important part in the communication system. Since the transmitted signal is subject to multipath interference and shadow effect caused by obstructions in the path during the transmission path to the receiver, these phenomena will cause the error rate of the received signal to increase. Therefore, in the prior art, in order to reduce the error rate of communication system transmission, channel estimation is performed, and the channel response is compensated through the estimation result to reduce the transmission error rate.

[0003] Another type of interference is radio frequency interference (RFI). The cause of RF interference is electromagnetic wave radiation, which resonates with the RF signal in the same frequency band, causing the RF signal to be interfered by electromagnetic wave radiation, thus making it impossible to transmit radio wave signals. The main reason for RF interference is that the wired high-frequency interface needs to be transmitted at high speed. The baseband and frequency multiplication used are high-frequency signals, which overlap with the frequency used by wireless radio frequency. Since the high-frequency signal is discontinuous, electromagnetic wave radiation forms noise. However, since the energy radiated by the noise is much greater than the energy of the wireless signal, the high-frequency noise resonance interferes with the RF signal, which is RF interference.

[0004] In the prior art, a Radio Frequency Interference (RFI) canceller technology is proposed. In a communication system, a tone generator is used after an equalizer to eliminate the RF interference. However, in the training mode of the connection stage, the RF interference canceller is prone to interact with the equalizer and a filter circuit such as a far-end crosstalk canceller (FEXT (Far End Crosstalk) canceller), so that its coefficients are deformed by the RF interference, thereby affecting the system performance, and in severe cases, causing the connection to fail. Summary of the invention

[0005] In order to avoid the problem of excessive processing of electromagnetic interference caused by mutual influence of filtering circuits in communication systems, the present invention proposes a method for eliminating radio frequency interference in a signal and a communication system running this method, wherein the method specifically avoids the notch problem caused by excessive processing of the interference elimination circuit in the communication system by masking the frequency band affected by radio frequency interference.

[0006] According to an embodiment of the communication system, the main circuits of the communication system include an analog-to-digital signal converter for converting an analog signal received by the communication system into a digital signal in the frequency domain; an RF interference detector for detecting a frequency band in the digital signal that is subject to RF interference; an interference elimination circuit, such as an equalizer and a far-end crosstalk canceller, for the purpose of performing interference elimination in the communication system; and an RF interference canceller for performing RF interference elimination on a frequency band in the digital signal that has RF interference.

[0007] A method for eliminating radio frequency interference in a signal is performed in a communication system. In this method, a frequency band in a digital signal that is affected by radio frequency interference is first detected by an radio frequency interference detector, and a processing circuit therein modifies a masking parameter in an interference elimination circuit so that the interference elimination circuit does not process the frequency band in which the radio frequency interference is detected when processing the digital signal. The processed signal is then transmitted to the radio frequency interference eliminator to perform radio frequency interference elimination, and then a digital signal after radio frequency interference elimination is output.

[0008] In the communication system, when the digital signal after the radio frequency interference is eliminated is finally output, it can be processed by a data divider and the non-noise signal can be output from the communication system.

[0009] Furthermore, the signal outputted by the data divider can be further passed through a feedback equalizer to eliminate inter-symbol interference and inter-carrier interference in the signal to increase the signal-to-noise ratio, and then fed back to the RF interference canceller to optimize the RF interference canceller's performance in eliminating RF interference.

[0010] In one embodiment, the interference cancellation circuit may include an equalizer and a far-end crosstalk canceller. By modifying masking parameters of the equalizer and the far-end crosstalk canceller to process digital signals, the equalizer and the far-end crosstalk canceller may not process frequency bands where radio frequency interference is detected.

[0011] In one embodiment, the method of not processing the frequency band where the radio frequency interference is detected is to mask the bin where the radio frequency interference is detected after fast Fourier transformation to the frequency domain.

[0012] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and description and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A circuit architecture embodiment diagram of a communication system using a method for eliminating radio frequency interference in a signal is shown;

[0014] Figure 2 A flow chart of an embodiment of a method for eliminating radio frequency interference in a signal is shown;

[0015] Figure 3 An embodiment of a process for a communication system to converge on masking parameters of an interference cancellation circuit in a training mode is shown;

[0016] Figure 4 The waveform diagram of the signal processed by the feedforward equalizer in the time domain is shown;

[0017] Figure 5 shows a waveform diagram of a signal processed by a feedforward equalizer in the frequency domain;

[0018] Figure 6 A waveform diagram showing a signal processed by a far-end crosstalk canceller in the time domain; and

[0019] Figure 7 The waveform diagram of the signal processed by the far-end crosstalk canceller in the frequency domain is shown. DETAILED DESCRIPTION

[0020] The following is an explanation of the embodiments of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the concept of the present invention. In addition, it is stated in advance that the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual sizes. The following embodiments will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention.

[0021] It should be understood that, although the terms "first", "second", "third", etc. may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are mainly used to distinguish one component from another component, or one signal from another signal. In addition, the term "or" used herein may include any one or more combinations of the associated listed items depending on the actual situation.

[0022] In the field of wireless communication, whether it is the transmitting end or the receiving end, there will always be signal interference problems, such as radio frequency interference (RFI). RF interference is generally electromagnetic interference caused by mutual inductance coupling of signals with similar frequencies received at the frequency position of the signal received by the receiver or at a position close to this frequency. These RF interferences will occupy unused frequency bands and interfere with signals in the used frequency bands. In addition to isolating the interference source as much as possible, the common way to eliminate RF interference (generally only reduces interference, but cannot completely eliminate interference) can also be used by compensation and gain adjustment. However, in general communication systems, it is possible that a specific interference elimination circuit in the communication system (such as an equalizer or a far-end crosstalk canceller) may produce a notch due to excessive processing, which will affect the subsequent RF interference elimination effect.

[0023] The present invention discloses a method for eliminating radio frequency interference in a signal and a communication system thereof. The main technical purpose of the method is to correct the masking parameters of an equalizer and a far-end crosstalk canceller when the communication system performs radio frequency interference (RFI) elimination without processing the frequency band detected with radio frequency interference, and then hand it over to the radio frequency interference canceller to perform radio frequency interference elimination. In this way, the notch generated by the interaction between the radio frequency interference canceller and the equalizer or the far-end crosstalk canceller can be avoided to affect the effect of radio frequency interference elimination. In addition to avoiding errors caused by notches in the signal processing process, the system performance can also be maintained at the same time.

[0024] The communication system using the method for eliminating radio frequency interference in a signal can refer to Figure 1 The circuit components of the communication system implement the method, and the related processes also refer to Figure 2 The embodiment flow chart is shown.

[0025] The communication system receives an input signal 11 through an antenna (step S201). The analog signal is first converted into a digital signal by an analog-to-digital signal converter 101 (step S203). In the method of eliminating radio frequency interference in the signal, the time domain signal is simultaneously converted into a frequency domain signal (step S205). Then, a radio frequency interference detector 102 detects the frequency band of the digital signal that is subject to radio frequency interference (step S207). According to one embodiment, one method of detecting the frequency band of radio frequency interference in the signal is to first store the digital signal in a register of the communication system, convert the time domain signal into a frequency domain signal by a fast Fourier transformation circuit, and then use the radio frequency interference detector 102 in the communication system to compare the signal with radio frequency interference according to the characteristics of the interference signal, so as to distinguish it from other signals.

[0026] For the frequency bands detected by the RF interference detector 102 and affected by RF interference, the communication system masks these frequency bands affected by RF interference, so that the subsequent interference elimination circuit in the communication system does not process the frequency bands detected by RF interference when processing digital signals. The technology of masking the frequency bands can be implemented by using bins, which are the smallest units when performing Fourier transform. The method of not processing the frequency bands detected by RF interference can be to mask the bins detected by RF interference after fast Fourier transform to frequency domain. The calculation method of modifying the masking parameters can refer to the following equation.

[0027] Equation 1 is a formula for updating the coefficients of the equalizer 103 (such as a feed-forward equalization (FFE)) and the coefficients of the far-end crosstalk canceller 105 (FEXT) in the communication system using the least mean square error (LMS) in the frequency domain, where "C(k)" represents a bin in the frequency domain, k is an index value, and "μ*X H (k)E(k)" is the coefficient for performing interference cancellation using interference cancellation circuits such as equalizer 103 and far-end crosstalk canceller 105. Equation 2 describes the Fourier transform equations of these systems.

[0028] The method for eliminating radio frequency interference in a signal proposed by the present invention is to mask the gradient of the bin where radio frequency interference is detected in the frequency domain. That is, when the radio frequency interference detector (RFI detector) detects that a bin (bin, index m) has radio frequency interference, the masking parameters (mask) of these bins are set to 0, as shown in equation 3, and when the signal (index k) is processed one by one to the bin with radio frequency interference (k=m), the interference elimination coefficient is set to 0 (X H (k)E(k)=0, i.e. setting mask) so that this item is not updated, so that the equalizer 103 and the far-end crosstalk canceller 105 do not process the frequency band where the RFI is detected, which is the method of not processing the frequency band where the RFI is detected as described in the above embodiment.

[0029] C(k+1)=C(k)+μ*X H (k)E(k);E(k)=FFT[e(n)] (Equation 1)

[0030] X(k)=FFT[X(n)],k=1,2,…,N (Equation 2)

[0031] X H (k)E(k)=0,if k=m (Equation 3)

[0032] Thus, the signal is processed by the interference cancellation circuit with modified masking parameters (step S209), and in particular, the frequency band where the RF interference is detected is not processed. Then, according to one embodiment, the RF interference detector 102 can provide the obtained frequency band (or bin) affected by the RF interference to the RF interference canceller 107 to perform RF interference cancellation (step S211), and finally output the signal after the RF interference is cancelled (step S213).

[0033] According to one embodiment, in a communication system, the digital signal output after the RF interference is eliminated can be processed by a data slicer 109 to generate an output signal 12, and then the non-noise signal is output from the communication system. The data slicer 109 is one of the post-processing circuits of the communication system, which can realize post-amplification, so that the final output amplitude of the entire communication system can be amplified to a demodulated level. The data slicer 109 can also use a comparator to compare the error according to the bit symbol in the signal to restore the digital signal demodulated by the receiver in the communication system, and finally determine whether the signal is noise or an actual signal to output the actual signal.

[0034] When the data divider 109 outputs a signal, the signal may be transmitted to a feedback equalizer (FBE) 108. The feedback equalizer 108 is used to eliminate inter-symbol interference and inter-carrier interference in the signal to increase a signal-to-noise ratio (SNR).

[0035] According to one embodiment, the above communication system can be implemented as a circuit system, which can be applied in a network device for network signal processing. When the network device receives a signal, it is converted into a frequency domain signal through a circuit, which may contain radio frequency interference (RFI). According to the above embodiment, the signal will be processed by an equalizer for multipath interference, and then processed by a far-end crosstalk canceller before being output to a radio frequency interference canceller, and finally processed by a data splitter before being output.

[0036] Applying the above method to eliminate RF interference in the signal, Figure 3 An embodiment of a process for converging masking parameters of an interference cancellation circuit in a communication system in a training mode is described.

[0037] When the communication system is in training mode, a signal generator generates a signal (step S301), wherein the RF interference detector detects the RF interference according to the characteristics of the interference (step S303), and the frequency band or bin affected by the interference must be noted, and the relevant notes are stored in the register of the communication system. At this time, the masking parameters are set for the noted frequency band (or bin) (step S305), so that when performing signal interference elimination (equalizer, far-end crosstalk elimination), the noted frequency band (or bin) is not processed (step S307), and then the result of signal interference elimination can be obtained, so as to update the parameters of the relevant interference elimination circuit (step S309).

[0038] The reference for updating the parameters of the relevant interference elimination circuit can be found in Figures 4 to 7 The waveform shown.

[0039] Figure 4 The waveform diagram of the signal processed by the feedforward equalizer in the time domain is shown, wherein after the signal is processed by the equalizer, when the frequency band where the radio frequency interference is detected is not masked, a signal 401 without masking is obtained, and when the frequency band where the radio frequency interference is detected is masked, a signal 402 with masking is obtained after the signal is processed by the equalizer. As can be seen from the figure, after the signal is processed by the equalizer, except for the peak part which is not affected, part of the signal in the signal 402 with masking is flat.

[0040] Convert the time domain signal into the frequency domain signal. The performance of the equalizer in the frequency domain can be referred to Figure 5The waveform diagram of the signal processed by the feedforward equalizer in the frequency domain is shown, wherein it is shown that after the signal is processed by the equalizer, without masking the frequency band where the radio frequency interference is detected, an unmasked signal 501 is obtained, and in particular, it is obtained that the signal strength of the unmasked signal 501 has an obvious dip at the position 0.6, that is, the phenomenon of notch 503 generated due to over-processing as described in the above embodiment, and when the frequency band where the radio frequency interference is detected is masked, the masked signal 502 in which the notch 503 problem has been solved is obtained after the signal is processed by the equalizer.

[0041] Figure 6 The waveform diagram of the signal processed by the FEXT canceller in the time domain shows that the original signal 602 is a waveform with large oscillations. If there is no masking for the frequency band with radio frequency interference, the signal is processed by the FEXT canceller to obtain an unmasked interference-eliminated signal 601. If the frequency band with radio frequency interference is masked, the signal is processed by the FEXT canceller to obtain a masked and interference-eliminated signal 603. In the time domain, it is not possible to clearly see the effect of masking the frequency band with radio frequency interference.

[0042] When the time domain signal is converted to the frequency domain signal, the waveform after the far-end crosstalk canceller processing can be referred to Figure 7 The waveform diagram of the signal processed by the far-end crosstalk canceller in the frequency domain is shown. This figure shows an original signal 702, in which when no masking is performed on the signal with radio frequency interference, an unmasked interference-eliminated signal 701 is obtained after being processed by the far-end crosstalk canceller, and a notch 704 generated by over-processing can be obtained at this time. However, if masking is performed on the frequency band where radio frequency interference is detected, a masked and interference-eliminated signal 703 that has solved the notch 704 can be obtained. It can be seen that the method for eliminating radio frequency interference in the signal proposed by the present invention can effectively mitigate the notch phenomenon caused by radio frequency interference to the equalizer and the far-end crosstalk canceller, and effectively reduce the influence of radio frequency interference on the interference elimination circuit (filter) in the communication system, thereby maintaining the stability of the system performance.

[0043] In summary, according to the method for eliminating radio frequency interference in a signal and the communication system thereof described in the above embodiments, the proposed method is mainly to solve the problem that the interference elimination circuit in the communication system may generate errors due to excessive processing, especially when the signal received by the communication system contains radio frequency interference, in order to avoid the problem of erroneous signals caused by the notch generated therein, the method will correct the masking parameters of the equalizer and the far-end crosstalk canceller, and adopt a method of not processing the frequency band detected with radio frequency interference, and then use the radio frequency interference canceller to eliminate radio frequency interference, and finally the communication system obtains a digital signal with radio frequency interference eliminated.

[0044] The contents disclosed above are only preferred feasible embodiments of the present invention and are not intended to limit the scope of protection of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention's specification and drawings are included in the scope of protection of the patent application of the present invention.

[0045] Description of reference numerals:

[0046] 11: Input signal

[0047] 101: Analog-to-digital signal converter

[0048] 102: Radio Frequency Interference Detector

[0049] 103: Equalizer

[0050] 105: Far-end crosstalk canceller

[0051] 107: RF Interference Eliminator

[0052] 108: Feedback Equalizer

[0053] 109: Data Splitter

[0054] 12: Output signal

[0055] 401: Signal not processed by masking

[0056] 402: Signal with masking processing

[0057] 501: Signal without masking processing

[0058] 502: Signal with masking processing

[0059] 503: Notch

[0060] 601: Unmasked interference-cancelled signal

[0061] 602: Original signal

[0062] 603: Signal after masking and interference elimination

[0063] 701: Unmasked interference-cancelled signal

[0064] 702: Original signal

[0065] 703: Signal after masking and interference elimination

[0066] 704: Notch

[0067] Steps S201 to S213: Process of eliminating radio frequency interference in signals

[0068] Steps S301 to S309: Process of converging to obtain masking parameters in training mode

Claims

1. A method for eliminating radio frequency interference in a signal, operating in a communication system, comprising: Convert the received analog signal into a digital signal in the frequency domain; Detect frequency bands affected by radio frequency interference; Processing the digital signal with an interference cancellation circuit that modifies a masking parameter mask, wherein a frequency band where radio frequency interference is detected is not processed; Using a radio frequency interference canceller to perform radio frequency interference cancellation on a frequency band affected by radio frequency interference; as well as Output digital signal with RF interference eliminated, The method of not processing the frequency band where the radio frequency interference is detected is to set the mask parameter mask of the bin where the radio frequency interference is detected to 0 in the frequency domain, and the bin is the smallest unit when performing Fourier transform.

2. The method for eliminating radio frequency interference in a signal according to claim 1, characterized in that: The interference elimination circuit includes an equalizer and a far-end crosstalk canceller, and processes the digital signal by modifying the masking parameters mask of the equalizer and the far-end crosstalk canceller, so that the equalizer and the far-end crosstalk canceller do not process the frequency band where the radio frequency interference is detected.

3. The method for eliminating radio frequency interference in a signal according to claim 2, characterized in that: Before the equalizer and the far-end crosstalk canceller process the digital signal, a radio frequency interference detector is used to detect the frequency band of the digital signal affected by radio frequency interference.

4. The method for eliminating radio frequency interference in a signal according to claim 3, characterized in that: The RF interference detector provides the obtained frequency band affected by RF interference to the RF interference canceller to perform RF interference cancellation.

5. The method for eliminating radio frequency interference in a signal according to claim 1, characterized in that: The digital signal after the radio frequency interference is eliminated is processed by a data divider, and a non-noise signal is output from the communication system.

6. The method for eliminating radio frequency interference in a signal according to claim 5, characterized in that: The signal outputted by the data divider is then passed through a feedback equalizer to eliminate inter-symbol interference and inter-carrier interference in the signal to increase the signal-to-noise ratio, and then fed back to the radio frequency interference canceller.

7. A communication system comprising: an analog-to-digital signal converter for converting an analog signal received by the communication system into a digital signal in the frequency domain; a radio frequency interference detector for detecting a frequency band in the digital signal that is subject to radio frequency interference; an interference cancellation circuit for performing interference cancellation; as well as a radio frequency interference canceller, for performing radio frequency interference cancellation on a frequency band having radio frequency interference in the digital signal; The communication system performs a method for eliminating radio frequency interference in a signal, comprising: Detecting the frequency band affected by radio frequency interference with the radio frequency interference detector for the digital signal, and modifying the masking parameter mask in the interference elimination circuit through the communication system so that the interference elimination circuit processes the digital signal but does not process the frequency band where the radio frequency interference is detected; Using the radio frequency interference canceller to perform radio frequency interference cancellation on the frequency band affected by radio frequency interference; and Output digital signal with RF interference eliminated, The method of not processing the frequency band where the radio frequency interference is detected is to set the mask parameter mask of the bin where the radio frequency interference is detected to 0 in the frequency domain, and the bin is the smallest unit when performing Fourier transform.

8. The communication system according to claim 7, characterized in that: The interference elimination circuit includes an equalizer and a far-end crosstalk canceller, and processes the digital signal by modifying the masking parameters mask of the equalizer and the far-end crosstalk canceller, so that the equalizer and the far-end crosstalk canceller do not process the frequency band where the radio frequency interference is detected.

9. The communication system according to claim 8, characterized in that: The RF interference detector provides the obtained frequency band affected by RF interference to the RF interference canceller to perform RF interference cancellation.

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