CN112672367A - Harmonic interference elimination method and device and receiving equipment - Google Patents
Harmonic interference elimination method and device and receiving equipment Download PDFInfo
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Abstract
The invention provides a method and a device for eliminating harmonic interference and receiving equipment, wherein the method comprises the following steps: carrying out first receiving processing on a received signal to obtain an original signal estimation; reconstructing the original signal estimate; obtaining a noise estimation signal according to the received signal and the reconstruction signal; carrying out frequency domain analysis on the noise estimation signal to obtain a harmonic interference frequency point; setting a notch frequency of a notch filter according to the harmonic interference frequency point, and filtering the received signal by using the notch filter; and carrying out second receiving processing on the filtered signals. The invention can adaptively detect the harmonic interference frequency point, track the change of the harmonic interference frequency point and improve the harmonic interference elimination capability of the receiving equipment.
Description
Technical Field
The present invention relates to the field of wireless communications, and in particular, to a method and an apparatus for eliminating harmonic interference, and a receiving device.
Background
In a wireless communication system, interference signals, such as harmonic interference, etc., often occur in signals received by a receiver, and the interference signals cause the signal-to-noise ratio of useful signals at corresponding frequency points to deteriorate, thereby seriously affecting the receiving performance.
Harmonic frequency points in the harmonic interference may come from the receiver circuit itself or from external interference. For example, harmonic interference of a Radio Frequency (RF) crystal oscillator becomes in-band interference of a received signal when a harmonic component of the crystal oscillator is coupled to an RF high-Frequency input port and passes through a mixer.
The harmonic frequency point may be a harmonic of a known frequency, such as the harmonic interference of the radio frequency crystal oscillator, and the harmonic frequency point is an integral multiple of the crystal oscillator fundamental frequency, which is known in advance.
For the harmonic interference of the known frequency, the position of the harmonic frequency point is fixed, and the known frequency information can be used for eliminating the harmonic interference, for example, a corresponding notch filter is arranged at the known harmonic interference frequency point.
However, if the harmonic frequency point is a harmonic of unknown frequency or the harmonic frequency point dynamically changes, the above method is not suitable, so it is necessary to provide a harmonic interference cancellation method suitable for the harmonic interference frequency point unknown or the harmonic interference frequency point changing.
Disclosure of Invention
The invention aims to provide a method and a device for eliminating harmonic interference and receiving equipment, which are used for solving the problem of harmonic interference caused by unknown harmonic interference frequency points or changed harmonic interference frequency points.
The technical scheme provided by the invention is as follows:
a method of harmonic interference cancellation, comprising: carrying out first receiving processing on a received signal to obtain an original signal estimation; reconstructing the original signal estimate; obtaining a noise estimation signal according to the reconstruction signal; carrying out frequency domain analysis on the noise estimation signal to obtain a harmonic interference frequency point; setting a notch frequency of a notch filter according to the harmonic interference frequency point, and filtering the received signal by using the notch filter; and carrying out second receiving processing on the filtered signals.
Further, the first receiving process includes: carrying out demodulation processing and decoding processing on the received signal in sequence, and taking the result after the decoding processing as the original signal estimation; reconstructing the original signal estimate, comprising: and sequentially carrying out coding processing and modulation processing on the original signal estimation.
Further, a noise estimation signal n is derived from the received signal and the reconstructed signal according to the following formula:
wherein y is the received signal,
for reconstructing the signal, H is the current channel estimation matrix, representing the convolution operation.
Further, the frequency domain analysis of the noise estimation signal to obtain a harmonic interference frequency point includes: performing fast Fourier transform on the noise estimation signal to obtain corresponding frequency spectrum information; and selecting the frequency points with the strongest energy, the energy of which exceeds a preset threshold and the number of which does not exceed a preset number, from the frequency spectrum information as harmonic interference frequency points.
Further, the sequentially demodulating and decoding the received signal includes: carrying out first filtering processing on a received signal by using a notch filter, and then carrying out demodulation processing and decoding processing on the signal subjected to the first filtering; the notch frequency of the notch filter is the previous harmonic interference frequency point; the obtaining of the noise estimation signal according to the reconstructed signal includes: and obtaining a noise estimation signal according to the first filtered signal and the reconstructed signal.
Further, the frequency domain analysis of the noise estimation signal to obtain a harmonic interference frequency point includes: performing fast Fourier transform on the noise estimation signal to obtain corresponding frequency spectrum information; selecting the frequency points with the strongest energy, the energy of which exceeds a preset threshold and the number of which does not exceed a preset number, from the frequency spectrum information as candidate interference frequency points output this time; acquiring the energy of the harmonic interference frequency point output last time in the frequency spectrum information, and compensating the harmonic interference frequency point according to the filtering depth parameter of the notch filter to obtain corresponding compensation energy; and selecting the frequency point with the strongest energy, the number of which is not more than the preset number, from the candidate interference frequency point and the harmonic interference frequency point output last time as the harmonic interference frequency point output this time according to the energy of the candidate interference frequency point and the compensation energy of the harmonic interference frequency point output last time.
The invention also provides a device for eliminating harmonic interference, which comprises: the receiving processing module is used for carrying out first receiving processing on the received signal to obtain an original signal estimation; a reconstruction module for reconstructing the original signal estimate; the noise estimation module is used for obtaining a noise estimation signal according to the reconstruction signal; the harmonic estimation module is used for carrying out frequency domain analysis on the noise estimation signal to obtain a harmonic interference frequency point; the notch filtering module is used for setting notch frequency of a notch filter according to the harmonic interference frequency point and filtering the received signal by using the notch filter; and the receiving processing module is also used for carrying out second receiving processing on the filtered signals.
Furthermore, the receiving processing module is further configured to sequentially perform demodulation processing and decoding processing on the received signal, and use a result after the decoding processing as an original signal estimation; and the reconstruction module is also used for sequentially carrying out coding processing and modulation processing on the original signal estimation.
Further, the receiving processing module is further configured to perform first filtering processing on the received signal by using a notch filter, perform demodulation processing and decoding processing on the signal subjected to the first filtering, and estimate a result after the decoding processing as an original signal; the notch frequency of the notch filter is the previous harmonic interference frequency point; and the noise estimation module is further configured to obtain a noise estimation signal according to the first filtered signal and the reconstructed signal.
The present invention also provides a receiving apparatus comprising: apparatus comprising harmonic interference cancellation as claimed in any preceding claim.
The method, the device and the receiving equipment for eliminating the harmonic interference provided by the invention can at least bring the following beneficial effects:
1. the invention utilizes signal reconstruction to detect the harmonic interference frequency point during receiving, dynamically adjusts the parameters of the notch filter according to the harmonic interference frequency point, and performs notch filtering on the received signal, thereby adaptively eliminating the harmonic interference and improving the receiving performance of the receiving equipment.
2. The invention can track the change of the harmonic interference frequency point well by detecting the harmonic interference frequency point in a self-adaptive manner.
3. According to the invention, the notch filter arranged at the previous harmonic interference frequency point is used for filtering the received signal for the first time, signal reconstruction is used for further harmonic interference detection, and the notch frequency of the notch filter is updated, so that the cycle is repeated, and the accuracy of the harmonic interference detection is further improved.
Drawings
The above features, technical features, advantages and implementations of a method and apparatus for harmonic interference cancellation, a receiving device and a method for harmonic interference cancellation according to the preferred embodiments will be described in detail in the following with reference to the accompanying drawings.
FIG. 1 is a flow diagram of one embodiment of a method of harmonic interference cancellation of the present invention;
FIG. 2 is a flow diagram of another embodiment of a method of harmonic interference cancellation of the present invention;
FIG. 3 is a schematic diagram of an embodiment of an apparatus for harmonic interference cancellation according to the present invention;
FIG. 4 is a schematic diagram of a receiving device according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an architecture of a wireless communication system;
fig. 6 is a schematic diagram of the working principle of a harmonic interference cancellation method applied to the LTE system.
The reference numbers illustrate:
100. the device comprises a receiving processing module, a 200 reconstruction module, a 300 noise estimation module, a 400 harmonic estimation module, a 500 notch filtering module and a 40 harmonic interference elimination device.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will be made with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, other drawings and embodiments can be derived from them without inventive effort.
For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product. In addition, in order to make the drawings concise and understandable, components having the same structure or function in some of the drawings are only schematically depicted, or only one of them is labeled. In this document, "one" means not only "only one" but also a case of "more than one".
One embodiment of the present invention, as shown in fig. 1, is a method for harmonic interference cancellation, including:
step S100 performs a first receiving process on the received signal to obtain an original signal estimate.
Step S200 reconstructs the original signal estimate.
Specifically, a typical wireless communication system is shown in fig. 5, and includes a Radio Access Network (RAN) 11 and a Core Network (CN) 12, where a User Equipment (UE) 13 accesses to a wireless Network through AN 11 and communicates with other networks, such as a Data Network (Data Network), through the CN 12.
The devices on the RAN side may be referred to as RAN devices, and may also be referred to as base stations. The names of the different communication systems are different, for example, in a Long Term Evolution (LTE) system, the communication system is called an evolved Node B (eNB), and in a 5G system, the communication system is called a next generation Node B (gnb). The base station and the UE communicate through an air interface (Uu). In the uplink direction, the UE transmits data and the base station receives. In the downlink direction, the base station transmits data and the UE receives.
The embodiment is suitable for a receiving end, and can be implemented in the uplink direction of a base station or the downlink direction of a UE.
In one embodiment of the first reception process, the received signal is demodulated, and the result of the demodulation process is regarded as one kind of original signal estimation and is referred to as a first original signal estimation. Correspondingly, the first original signal estimate is modulated to obtain a reconstructed signal, which is a kind of transmitted signal estimate corresponding to the received signal.
In another embodiment of the first reception process, the received signal is sequentially demodulated and decoded, and the result of the decoding process is regarded as one kind of original signal estimation and is referred to as a second original signal estimation. And carrying out coding processing and modulation processing on the second original signal estimation to obtain a reconstructed signal, wherein the reconstructed signal is another type of transmitted signal estimation corresponding to the received signal. According to the embodiment, reconstruction is carried out according to the decoded result, the reconstructed signal is more accurate, the subsequent noise estimation signal is more accurate, and the detection of the harmonic interference frequency point is more accurate. In addition, the accuracy of the decoding result can be identified according to whether the CRC check of the decoding result is correct or not. Preferably, if the decoding CRC check is correct, the original signal estimate is reconstructed and the subsequent steps are performed; otherwise, it is discarded.
Step S300 obtains a noise estimation signal according to the received signal and the reconstructed signal.
The noise estimation signal n is obtained according to the following formula:
where y is the received signal,
for reconstructing the signal, H is the current channel estimation matrix, representing the convolution operation.
Step S400, the noise estimation signal is subjected to frequency domain analysis to obtain a harmonic interference frequency point.
Specifically, fast fourier transform is performed on the noise estimation signal to obtain corresponding spectrum information. And selecting the frequency points with the strongest energy, the energy of which exceeds a preset threshold and the number of which does not exceed a preset number, from the frequency spectrum information as harmonic interference frequency points. Specifically, the first N frequency points with the strongest energy can be found from the frequency spectrum information, where N is a preset number, and the frequency points with the energy exceeding a preset threshold in the first N frequency points are used as harmonic interference frequency points. Or, finding out frequency points with energy exceeding a preset threshold from the frequency spectrum information, then selecting harmonic interference frequency points from the frequency points, and if the number of the frequency points is more than N, selecting the first N frequency points with the strongest energy as the harmonic interference frequency points; and if the frequency points are not more than N, taking the frequency points as harmonic interference frequency points.
Step S500, the notch frequency of the notch filter is set according to the harmonic interference frequency point, and the received signal is filtered by the notch filter.
Step S600 performs a second reception process on the filtered signal.
Specifically, the notch frequency of the notch filter output this time is set as a harmonic interference frequency point. If a plurality of harmonic interference frequency points exist, a corresponding number of notch filters are arranged. The number of notch filters may be determined according to the number of preset harmonic interference points. If no harmonic interference frequency point reaching the preset harmonic interference frequency point number is detected in the actual detection, the parameters of the redundant notch filter can be set as through.
And filtering the received signal by using a notch filter, and performing second receiving processing on the filtered signal. The second reception process refers to a conventional reception process including a demodulation process and a decoding process. Because the second receiving process eliminates the influence of harmonic interference, the signal obtained by the second receiving process is estimated more accurately to be used as the final original signal.
In the embodiment, harmonic interference frequency point detection is performed by utilizing signal reconstruction during receiving, parameters of a notch filter are dynamically adjusted according to the harmonic interference frequency points, and notch filtering is performed on a received signal, so that harmonic interference is adaptively eliminated, and the receiving performance of receiving equipment is improved; the harmonic interference frequency point can be detected in a self-adaptive mode, and the change of the harmonic interference frequency point is tracked.
Another embodiment of the present invention, as shown in fig. 2, is a method of harmonic interference cancellation, comprising:
step S110, carrying out first filtering processing on the received signal by using a notch filter, and carrying out first receiving processing on the signal after the first filtering processing to obtain an original signal estimation; the notch frequency of the notch filter is the previous harmonic interference frequency point.
Step S210 reconstructs the original signal estimate.
Specifically, the present embodiment is applicable to a receiving end, and can be implemented in both an uplink direction of a base station and a downlink direction of a UE.
Initially, the notch filter is set to pass through, for example, the initial value of the notch frequency may be set to a frequency point outside the reception band. And after the harmonic interference frequency point is obtained, the trapped wave frequency is the previous harmonic interference frequency point.
In one embodiment of the first reception process, the received signal is demodulated, and the result of the demodulation process is regarded as one kind of original signal estimation and is referred to as a first original signal estimation. Correspondingly, the first original signal estimate is modulated to obtain a reconstructed signal, which is a kind of transmitted signal estimate corresponding to the received signal.
In another embodiment of the first reception process, the received signal is sequentially demodulated and decoded, and the result of the decoding process is regarded as one kind of original signal estimation and is referred to as a second original signal estimation. And carrying out coding processing and modulation processing on the second original signal estimation to obtain a reconstructed signal, wherein the reconstructed signal is another type of transmitted signal estimation corresponding to the received signal. Preferably, if the decoding CRC check is correct, the original signal estimate is reconstructed and the subsequent steps are performed; otherwise, it is discarded.
Because the received signal is firstly filtered, part of interference is filtered, and then the first receiving processing is carried out, the obtained original signal estimation is more accurate compared with the original signal estimation obtained by directly carrying out the first receiving processing on the received signal. The resulting reconstructed signal will also be more accurate.
Step S310 obtains a noise estimation signal according to the first filtered signal and the reconstructed signal.
The noise estimation signal n is obtained according to the following formula:
where y2 is the first filtered signal,
for reconstructing the signal, H is the current channel estimation matrix, representing the convolution operation.
Step S410, frequency domain analysis is carried out on the noise estimation signal to obtain a harmonic interference frequency point.
The method specifically comprises the following steps: carrying out fast Fourier transform on the noise estimation signal to obtain corresponding frequency spectrum information; selecting the frequency points with the strongest energy, the energy of which exceeds a preset threshold and the number of which does not exceed a preset number, from the frequency spectrum information as candidate interference frequency points output this time; acquiring the energy of the harmonic interference frequency point output last time in the frequency spectrum information, and compensating the harmonic interference frequency point according to the filtering depth parameter of the notch filter to obtain corresponding compensation energy; and selecting the frequency point with the strongest energy, the number of which is not more than the preset number, from the candidate interference frequency point and the harmonic interference frequency point output last time as the harmonic interference frequency point output this time according to the energy of the candidate interference frequency point and the compensation energy of the harmonic interference frequency point output last time.
For example, assuming that the preset number is 3, the filtering depth parameter of the harmonic filter is 10dB, and the previous output 3 harmonic interference frequency points are f11, f12, and f 13; 3 candidate interference frequency points are output at this time, and the corresponding frequency points are f1, f2 and f 3. From the spectrum information obtained this time, the energy values of f1, f2 and f3 are a1, a2 and a3 respectively; the energy values of f11, f12 and f13 are b1, b2 and b3 respectively; because the signals of the f11, f12 and f13 frequency points are subjected to notch filtering processing by the harmonic filter, the energy of the obtained signals is reduced by 10dB, so that the actual energy of the signals is added with 10dB and then compared with the energy values of f1, f2 and f 3. The compensation energy values of f11, f12 and f13 are (b1+10), (b2+10) and (b3+10), respectively. And comparing the energy values of f11, f12 and f13 with the compensation energy values of f11, f12 and f13, and selecting the first 3 frequency points with the largest energy as the harmonic interference frequency points output at this time.
Step S510 updates the notch frequency of the notch filter according to the output harmonic interference frequency point, and performs filtering processing on the received signal by using the notch filter.
Step S610 performs second reception processing on the filtered signal.
The second reception process refers to a conventional reception process including a demodulation process and a decoding process. And taking the signal obtained by the second receiving processing as a final original signal.
In this embodiment, the notch filter set at the harmonic interference frequency point of the previous time is used to perform the first filtering processing on the received signal, and then the conventional receiving processing is performed to obtain more accurate original signal estimation, so as to obtain more accurate reconstructed signals, thereby further improving the accuracy of the harmonic interference detection.
In one embodiment of the present invention, as shown in fig. 3, an apparatus 40 for harmonic interference cancellation includes:
the receiving processing module 100 is configured to perform a first receiving process on the received signal to obtain an original signal estimate.
A reconstruction module 200 for reconstructing the original signal estimate.
Specifically, the present embodiment is applicable to a receiving end, and can be implemented in both an uplink direction of a base station and a downlink direction of a UE.
In one embodiment of the first reception process, the received signal is demodulated, and the result of the demodulation process is regarded as one kind of original signal estimation and is referred to as a first original signal estimation. Correspondingly, the first original signal estimate is modulated to obtain a reconstructed signal, which is a kind of transmitted signal estimate corresponding to the received signal.
In another embodiment of the first reception process, the received signal is sequentially demodulated and decoded, and the result of the decoding process is regarded as one kind of original signal estimation and is referred to as a second original signal estimation. And carrying out coding processing and modulation processing on the second original signal estimation to obtain a reconstructed signal, wherein the reconstructed signal is another type of transmitted signal estimation corresponding to the received signal. According to the embodiment, reconstruction is carried out according to the decoded result, the reconstructed signal is more accurate, the subsequent noise estimation signal is more accurate, and the detection of the harmonic interference frequency point is more accurate. In addition, the accuracy of the decoding result can be identified according to whether the CRC check of the decoding result is correct or not. Preferably, if the decoding CRC check is correct, the original signal estimate is reconstructed and the subsequent steps are performed; otherwise, it is discarded.
A noise estimation module 300, configured to obtain a noise estimation signal according to the received signal and the reconstructed signal.
The noise estimation module 300 obtains a noise estimation signal n according to the following formula:
where y is the received signal,
for reconstructing the signal, H is the current channel estimation matrix, representing the convolution operation.
And the harmonic estimation module 400 is configured to perform frequency domain analysis on the noise estimation signal to obtain a harmonic interference frequency point.
Specifically, the harmonic estimation module performs fast fourier transform on the noise estimation signal to obtain corresponding spectrum information. And selecting the frequency points with the strongest energy, the energy of which exceeds a preset threshold and the number of which does not exceed a preset number, from the frequency spectrum information as harmonic interference frequency points.
And a notch filtering module 500, configured to set a notch frequency of a notch filter according to the harmonic interference frequency point, and perform filtering processing on the received signal by using the notch filter.
The receiving processing module 100 is further configured to perform a second receiving process on the filtered signal.
Specifically, the notch frequency of the notch filter output this time is set as a harmonic interference frequency point. If a plurality of harmonic interference frequency points exist, a corresponding number of notch filters are arranged. The number of notch filters may be determined according to the number of preset harmonic interference points. If no harmonic interference frequency point reaching the preset harmonic interference frequency point number is detected in the actual detection, the parameters of the redundant notch filter can be set as through.
And filtering the received signal by using a notch filter, and performing second receiving processing on the filtered signal. The second reception process refers to a conventional reception process including a demodulation process and a decoding process. Because the second receiving process eliminates the influence of harmonic interference, the signal obtained by the second receiving process is estimated more accurately to be used as the final original signal.
In the embodiment, harmonic interference frequency point detection is performed by utilizing signal reconstruction during receiving, parameters of a notch filter are dynamically adjusted according to the harmonic interference frequency points, and notch filtering is performed on a received signal, so that harmonic interference is adaptively eliminated, and the receiving performance of receiving equipment is improved; the harmonic interference frequency point can be detected in a self-adaptive mode, and the change of the harmonic interference frequency point is tracked.
In one embodiment of the present invention, as shown in fig. 3, an apparatus 40 for harmonic interference cancellation includes:
a notch filtering module 500, configured to perform a first filtering process on the received signal by using a notch filter; the notch frequency of the notch filter is the previous harmonic interference frequency point.
The receiving processing module 100 is configured to perform a first receiving processing on the first filtered signal to obtain an original signal estimate.
A reconstruction module 200 for reconstructing the original signal estimate.
Specifically, the present embodiment is applicable to a receiving end, and can be implemented in both an uplink direction of a base station and a downlink direction of a UE.
Initially, the notch filter is set to pass through, for example, the initial value of the notch frequency may be set to a frequency point outside the reception band. And after the harmonic interference frequency point is obtained, the trapped wave frequency is the previous harmonic interference frequency point.
In one embodiment of the first reception process, the received signal is demodulated, and the result of the demodulation process is regarded as one kind of original signal estimation and is referred to as a first original signal estimation. Correspondingly, the first original signal estimate is modulated to obtain a reconstructed signal, which is a kind of transmitted signal estimate corresponding to the received signal.
In another embodiment of the first reception process, the received signal is sequentially demodulated and decoded, and the result of the decoding process is regarded as one kind of original signal estimation and is referred to as a second original signal estimation. And carrying out coding processing and modulation processing on the second original signal estimation to obtain a reconstructed signal, wherein the reconstructed signal is another type of transmitted signal estimation corresponding to the received signal. Preferably, if the decoding CRC check is correct, the original signal estimate is reconstructed and the subsequent steps are performed; otherwise, it is discarded.
Because the received signal is firstly filtered, part of interference is filtered, and then the first receiving processing is carried out, the obtained original signal estimation is more accurate compared with the original signal estimation obtained by directly carrying out the first receiving processing on the received signal. The resulting reconstructed signal will also be more accurate.
A noise estimation module 300, configured to obtain a noise estimation signal according to the first filtered signal and the reconstructed signal.
The noise estimation module 300 obtains a noise estimation signal n according to the following formula:
where y2 is the first filtered signal,
for reconstructing the signal, H is the current channel estimation matrix, representing the convolution operation.
And the harmonic estimation module 400 is configured to perform frequency domain analysis on the noise estimation signal to obtain a harmonic interference frequency point.
The method specifically comprises the following steps: carrying out fast Fourier transform on the noise estimation signal to obtain corresponding frequency spectrum information; selecting the frequency points with the strongest energy, the energy of which exceeds a preset threshold and the number of which does not exceed a preset number, from the frequency spectrum information as candidate interference frequency points output this time; acquiring the energy of the harmonic interference frequency point output last time in the frequency spectrum information, and compensating the harmonic interference frequency point according to the filtering depth parameter of the notch filter to obtain corresponding compensation energy; and selecting the frequency point with the strongest energy, the number of which is not more than the preset number, from the candidate interference frequency point and the harmonic interference frequency point output last time as the harmonic interference frequency point output this time according to the energy of the candidate interference frequency point and the compensation energy of the harmonic interference frequency point output last time.
The notch filtering module 500 is further configured to update a notch frequency of the notch filter according to the output harmonic interference frequency point, and perform filtering processing on the received signal by using the notch filter.
The receiving processing module 100 is further configured to perform a second receiving process on the filtered signal.
The second reception process refers to a conventional reception process including a demodulation process and a decoding process. And taking the signal obtained by the second receiving processing as a final original signal.
In this embodiment, the notch filter set at the harmonic interference frequency point of the previous time is used to perform the first filtering processing on the received signal, and then the conventional receiving processing is performed to obtain more accurate original signal estimation, so as to obtain more accurate reconstructed signals, thereby further improving the accuracy of the harmonic interference detection.
It should be noted that the embodiment of the apparatus for eliminating harmonic interference provided by the present invention and the embodiment of the method for eliminating harmonic interference provided by the foregoing embodiments are all based on the same inventive concept, and can achieve the same technical effects. Therefore, other specific contents of the embodiment of the apparatus for harmonic interference cancellation may refer to the description of the embodiment of the method for harmonic interference cancellation.
The invention also provides a concrete implementation scene example, and the method and the device for eliminating the harmonic interference provided by the invention are applied to an LTE system and are used for improving the harmonic interference elimination capability of a receiving end, wherein the receiving end can be a base station or UE.
As shown in fig. 6, a Notch Filter (Notch Filter) group is added before demodulation processing to eliminate the detected harmonic interference.
The method comprises the following specific steps:
step S0, the receiver performs radio frequency processing on the received signal of the antenna port to obtain a received signal for baseband processing. In the baseband processing, the first filtering is performed through a notch filter bank.
Initially the notch filter bank is set to pass-through.
After the first harmonic interference detection, the notch frequencies of the notch filter bank are updated to the first detected harmonic interference bins in step S4. And when the second harmonic interference detection is carried out, keeping the notch frequency of the notch filter group unchanged, namely, carrying out first filtering on the first detected harmonic interference frequency point. After the second harmonic interference detection, the notch frequency of the notch filter bank is updated to the harmonic interference frequency point detected for the second time, and the process is repeated, so that the notch frequency of the notch filter bank can be stabilized under the condition that the interference frequency point is stable.
And step S1, demodulating and decoding the signal after the first filtering to obtain the original signal estimation. This reception process is referred to as a first reception process.
And step S2, if the CRC check of the decoded result is correct, reconstructing a transmitting signal corresponding to the current receiving signal according to the decoded result, and using the reconstructed signal as a reconstructed signal.
And step S3, carrying out harmonic estimation according to the first filtered signal, the reconstructed signal and the current channel estimation matrix H, and outputting a harmonic interference frequency point.
The current channel estimation matrix H may be obtained by performing channel estimation according to the received reference signal.
Step S3 specifically includes:
step S31, setting the signal after the first time of filtering in the time domain as y2, and reconstructing the signal as
A noise estimation signal is obtained
Where denotes the convolution operation.
Step S32, performing FFT (fast fourier transform) analysis on the noise estimation signal n to obtain the energy of each frequency point in the noise, and further performing normalization processing to obtain the relative energy (also called normalized energy, i.e. relative energy based on signal intensity of 1) of each frequency point in the noise under the normalization of useful signal intensity, so as to obtain the spectrum information of each frequency point.
And S33, finding out m frequency points f 1-fm which exceed a preset threshold and have the strongest relative energy from the frequency spectrum information, and taking the frequency points as candidate interference frequency points.
And step S34, acquiring the energy of the harmonic interference frequency point output last time in the frequency spectrum information, and compensating the harmonic interference frequency point according to the filtering depth parameter of the notch filter to obtain corresponding compensation energy.
And step S35, selecting the frequency point with the strongest energy, the number of which is not more than the preset number, from the candidate interference frequency point and the harmonic interference frequency point output last time as the harmonic interference frequency point output this time according to the energy of the candidate interference frequency point and the compensation energy of the harmonic interference frequency point output last time.
And step S4, calculating the coefficients of the corresponding Notch flag group according to the harmonic interference frequency point output this time, wherein the coefficients mainly comprise Notch frequency, Notch width and the like, and updating the Notch flag group by using the coefficients.
Step S5, performing Notch filtering on the updated Notch flag group of the received signal, performing second receiving processing on the filtered signal, and taking the result of the second receiving processing as the final original signal.
One embodiment of the present invention, as shown in fig. 4, a receiving apparatus includes a device 40 for harmonic interference cancellation.
The receiving equipment performs harmonic interference frequency point detection on the received signal, dynamically adjusts parameters of a notch filter according to the harmonic interference frequency point, performs notch filtering on the received signal, and performs second receiving processing on the filtered signal, so that harmonic interference is eliminated in a self-adaptive manner, and the receiving performance of the receiving equipment is improved.
It should be noted that the above embodiments can be freely combined as necessary. The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A method of harmonic interference cancellation, comprising:
carrying out first receiving processing on a received signal to obtain an original signal estimation;
reconstructing the original signal estimate;
obtaining a noise estimation signal according to the received signal and the reconstruction signal;
carrying out frequency domain analysis on the noise estimation signal to obtain a harmonic interference frequency point;
setting a notch frequency of a notch filter according to the harmonic interference frequency point, and filtering the received signal by using the notch filter;
and carrying out second receiving processing on the filtered signals.
2. The method of harmonic interference cancellation according to claim 1, characterized by:
the first reception processing includes:
carrying out demodulation processing and decoding processing on the received signal in sequence, and taking the result after the decoding processing as the original signal estimation;
reconstructing the original signal estimate, comprising: and sequentially carrying out coding processing and modulation processing on the original signal estimation.
3. The method of harmonic interference cancellation according to claim 2, characterized by:
deriving a noise estimate signal n from the received signal and the reconstructed signal according to the following equation:
wherein y is the received signal,
for reconstructing the signal, H is the current channel estimation matrix, representing the convolution operation.
4. The method of eliminating harmonic interference according to claim 3, wherein the performing frequency domain analysis on the noise estimation signal to obtain a harmonic interference frequency point comprises:
performing fast Fourier transform on the noise estimation signal to obtain corresponding frequency spectrum information;
and selecting the frequency points with the strongest energy, the energy of which exceeds a preset threshold and the number of which does not exceed a preset number, from the frequency spectrum information as harmonic interference frequency points.
5. The method of harmonic interference cancellation according to claim 2, characterized by:
the sequentially demodulating and decoding the received signal includes: carrying out first filtering processing on a received signal by using a notch filter, and then carrying out demodulation processing and decoding processing on the signal subjected to the first filtering; the notch frequency of the notch filter is the previous harmonic interference frequency point;
the obtaining a noise estimation signal according to the received signal and the reconstructed signal includes: and obtaining a noise estimation signal according to the first filtered signal and the reconstructed signal.
6. The method of eliminating harmonic interference according to claim 5, wherein the performing frequency domain analysis on the noise estimation signal to obtain a harmonic interference frequency point comprises:
performing fast Fourier transform on the noise estimation signal to obtain corresponding frequency spectrum information;
selecting the frequency points with the strongest energy, the energy of which exceeds a preset threshold and the number of which does not exceed a preset number, from the frequency spectrum information as candidate interference frequency points output this time;
acquiring the energy of the harmonic interference frequency point output last time in the frequency spectrum information, and compensating the harmonic interference frequency point according to the filtering depth parameter of the notch filter to obtain corresponding compensation energy;
and selecting the frequency point with the strongest energy, the number of which is not more than the preset number, from the candidate interference frequency point and the harmonic interference frequency point output last time as the harmonic interference frequency point output this time according to the energy of the candidate interference frequency point and the compensation energy of the harmonic interference frequency point output last time.
7. An apparatus for harmonic interference cancellation, comprising:
the receiving processing module is used for carrying out first receiving processing on the received signal to obtain an original signal estimation;
a reconstruction module for reconstructing the original signal estimate;
the noise estimation module is used for obtaining a noise estimation signal according to the received signal and the reconstructed signal;
the harmonic estimation module is used for carrying out frequency domain analysis on the noise estimation signal to obtain a harmonic interference frequency point;
the notch filtering module is used for setting notch frequency of a notch filter according to the harmonic interference frequency point and filtering the received signal by using the notch filter;
and the receiving processing module is also used for carrying out second receiving processing on the filtered signals.
8. The apparatus for harmonic interference cancellation according to claim 7, wherein:
the receiving processing module is further configured to sequentially perform demodulation processing and decoding processing on the received signal, and take a result after the decoding processing as an original signal estimation;
and the reconstruction module is also used for sequentially carrying out coding processing and modulation processing on the original signal estimation.
9. The apparatus for harmonic interference cancellation according to claim 8, wherein:
the receiving processing module is further configured to perform first filtering processing on the received signal by using a notch filter, perform demodulation processing and decoding processing on the signal subjected to the first filtering, and estimate a result after the decoding processing as an original signal; the notch frequency of the notch filter is the previous harmonic interference frequency point;
and the noise estimation module is further configured to obtain a noise estimation signal according to the first filtered signal and the reconstructed signal.
10. A receiving device, comprising: an apparatus for harmonic interference cancellation as claimed in any one of claims 7 to 9.
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