Interference suppression method and device based on local spreading code frequency domain digital filtering

Abstract

The application relates to an interference suppression method and device based on local spread spectrum code frequency domain digital filtering, which comprises the following steps: interference sensing of a received spread spectrum signal to obtain interference sensing information of narrowband interference; frequency domain comb digital filtering processing of a local spread spectrum code according to the interference sensing information and an anti-interference strategy of the spread spectrum system; inverse Fourier transform of the spectrum of the filtered local spread spectrum code to obtain a local spread spectrum code time domain waveform; multiplication of the local spread spectrum code time domain waveform and the input spread spectrum signal to complete narrowband interference suppression; and spread spectrum signal synchronization and despreading of the signal after the narrowband interference suppression. The application realizes narrowband interference suppression in the despreading link of the received spread spectrum signal by performing frequency domain digital filtering of the local spread spectrum code at the receiving end of the spread spectrum system, reduces the complexity of the multiple frequency domain transform processing of the spread spectrum signal at the receiving end in the traditional method, and improves the wideband anti-interference capability of the spread spectrum system.

Description

Technical Field

[0001] This invention relates to the field of communications, and in particular to an interference suppression method and apparatus based on local spreading code frequency domain digital filtering. Background Technology

[0002] Direct sequence spread spectrum (DSSS) technology features low power spectral density, good signal concealment, strong multiple access communication capability, and strong noise / interference resistance, making it widely used in fields such as security, anti-interference, and anti-surveillance communication. The anti-interference capability of a DSSS system is mainly reflected in its resistance to narrowband interference, which depends primarily on the system's spread spectrum processing gain, which is mainly achieved by increasing the spread spectrum bandwidth. However, due to hardware limitations, the spread spectrum bandwidth cannot be expanded indefinitely. Furthermore, increasing the spread spectrum bandwidth inevitably introduces more narrowband interference, degrading communication performance. When the spread spectrum processing gain is insufficient to combat strong narrowband interference, additional interference suppression techniques must be employed to improve the system's resistance to strong narrowband interference.

[0003] A typical method for handling narrowband interference involves frequency domain filtering of the received spread spectrum signal. This involves first performing a Fast Fourier Transform (FFT) to digitally process the received spread spectrum signal, obtaining the input signal's spectrum, identifying the amplitude and frequency distribution of narrowband interference, then suppressing the interference in the frequency domain, and finally performing an Inverse Fast Fourier Transform (IFFT) to restore the frequency domain signal to the time domain signal before despreading the input spread spectrum signal. Frequency domain suppression of narrowband interference typically employs the following approach: in the spectrum of the received spread spectrum signal, the amplitude coefficients of narrowband interference signals exceeding a threshold are set to zero or set to a suitable parameter value, such as a threshold or average noise amplitude, thereby suppressing the interference signal in the frequency domain.

[0004] For systems with low spread spectrum bandwidth, this frequency domain processing method has low computational cost and good interference suppression performance. However, as the bandwidth of the spread spectrum system increases, this method will face significant challenges in terms of data processing volume and response time. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the present invention aims to provide an interference suppression method and apparatus based on local spreading code frequency domain digital filtering. By performing frequency domain digital filtering of the local spreading code at the receiving end of the spread spectrum system, interference suppression is achieved in the despreading stage of the received spread spectrum signal by the local spreading code. This reduces the complexity of multiple frequency domain transformations of the spread spectrum signal at the receiving end in traditional methods and improves the broadband anti-interference capability of the spread spectrum system.

[0006] To achieve the above-mentioned objectives, this invention provides an interference suppression method based on local spreading code frequency domain digital filtering, comprising the following steps:

[0007] Interference sensing is performed on the spread spectrum signal input to the receiving end to obtain interference sensing information of narrowband interference;

[0008] Based on the interference sensing information and the anti-interference strategy of the spread spectrum system, the local spreading code is subjected to frequency domain comb-tooth digital filtering.

[0009] Perform an inverse Fourier transform on the filtered local spreading code spectrum to obtain the local spreading code time-domain waveform;

[0010] The local spreading code time-domain waveform is multiplied by the input spreading signal to achieve narrowband interference suppression;

[0011] The signal that has completed narrowband interference suppression is then spread spectrum synchronized and despread.

[0012] According to one technical solution of the present invention, the interference sensing of the spread spectrum signal input to the receiving end includes:

[0013] Using a spectrum estimation method, with a fast refresh rate at frequency resolution granularity, the interference threshold within the spread spectrum signal bandwidth is determined, as well as the interference type, occupied bandwidth, center frequency, and average power exceeding the interference threshold.

[0014] Anti-interference decisions are made according to the anti-interference strategy of the spread spectrum system, and interference suppression parameters are generated; the interference suppression parameters include the number of local spreading code frequency domain comb levels, comb power attenuation factor, and timestamp.

[0015] According to one technical solution of the present invention, the frequency resolution granularity is smaller than the frequency domain comb spacing of the local spreading code.

[0016] According to one technical solution of the present invention, the frequency domain comb digital filtering process includes:

[0017] Set the amplitude value of the frequency component in the local spreading code spectrum corresponding to the frequency of the narrowband interference signal to zero, or set it to a specific threshold.

[0018] According to one aspect of the present invention, an interference suppression device based on local spreading code frequency domain digital filtering is provided, comprising:

[0019] The spread spectrum signal input unit is used to receive the input spread spectrum signal and output the spread spectrum signal in two paths.

[0020] An interference sensing unit, connected to the spread spectrum signal input unit, is used to sense narrowband interference within the spread spectrum signal band, acquire interference sensing information of the narrowband interference signal, and generate interference suppression parameters.

[0021] A local spreading code generation unit, connected to the interference sensing unit, is used to store the encoding information of the local spreading code, and to perform frequency domain comb-tooth digital filtering on the local spreading code according to the interference sensing information and the interference suppression parameters; and to perform IFFT transform on the filtered local spreading code to generate the time domain waveform of the local spreading code.

[0022] The signal processing unit, connected to the spread spectrum signal input unit and the local spread spectrum code generation unit, is used to receive the time-domain waveforms of the spread spectrum signal and the local spread spectrum code, perform synchronization, despreading, filtering or integration processing on the time-domain waveforms of the spread spectrum signal and the local spread spectrum code, and obtain and output the despread signal.

[0023] The control unit is used to control each functional unit.

[0024] According to one technical solution of the present invention, the local spreading code generation unit includes:

[0025] A local spreading code parameter memory is used to receive the interference sensing information and the interference suppression parameters; the interference sensing unit is provided with a control and decision command input port, which is connected to the local spreading code parameter memory;

[0026] A local spreading code frequency domain parameter regulator is used to perform frequency domain comb-tooth digital filtering on the local spreading code based on the interference sensing information and the interference suppression parameters.

[0027] An IFFT processor is used to perform IFFT transformation on the filtered local spreading code to generate the time-domain waveform of the local spreading code.

[0028] The local spreading code waveform output port is used to output the local spreading code time-domain waveform to the signal processing unit.

[0029] According to one technical solution of the present invention, the control and decision command input port is used to receive control commands from the control unit.

[0030] According to one technical solution of the present invention, the signal processing unit includes:

[0031] A spread spectrum signal despreading processor is used to despread the received spread spectrum signal and the time-domain waveform of the local spreading code to obtain a despread signal;

[0032] A despreading signal inverter is used to down-convert the despreading signal via a local oscillator to generate a baseband data signal.

[0033] A despread signal filter is used to perform low-pass filtering on the baseband digital signal to generate a baseband low-pass data signal;

[0034] The broadband spread spectrum digital signal input port and the local spread spectrum code waveform input port are respectively connected to the spread spectrum signal input unit and the local spread spectrum code generation unit;

[0035] The despread signal output port is used to output the baseband low-pass data signal to the back-end processor for signal demodulation.

[0036] According to one technical solution of the present invention, the spread spectrum signal input unit further includes:

[0037] The first digital-to-analog converter has its input terminal connected to the output terminal of the spread spectrum signal input unit, and its output terminal has two paths, which are respectively connected to the interference sensing unit and the signal processing unit.

[0038] According to one technical solution of the present invention, it further includes:

[0039] The second analog-to-digital converter has its input terminal connected to one output terminal of the spread spectrum signal input unit; its output terminal is connected to the input terminal of the interference sensing unit.

[0040] The second digital-to-analog converter has its input terminal connected to the output terminal of the local spreading code generation unit, and its output terminal connected to one input terminal of the signal processing unit.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention proposes a narrowband interference suppression method for spread spectrum systems based on frequency domain digital filtering of the local spreading code waveform at the receiver. By performing frequency domain comb digital filtering of the local spreading code waveform at the receiver of the spread spectrum system, that is, by selectively setting the amplitude codeword of the local spreading code frequency domain comb corresponding to the interference frequency to zero or setting it to a certain threshold according to the interference frequency and bandwidth distribution characteristics, interference suppression is achieved in the despreading stage of the received spread spectrum signal by the local spreading code waveform, reducing the complexity of signal processing at the receiver and improving the broadband anti-interference capability of the spread spectrum system.

[0043] This invention achieves efficient narrowband interference suppression and wideband spread spectrum signal reception and despreading without requiring high-speed time-frequency (FFT) and frequency-time (IFFT) transformations on the wideband spread spectrum signal. This significantly reduces signal processing complexity and computational load, and enhances the wideband anti-interference capability of the spread spectrum system.

[0044] This invention targets frequency domain interference suppression only for the local spreading code frequency domain comb. It directly sets the amplitude value of the frequency component in the local spreading code spectrum corresponding to the frequency of the narrowband interference signal to zero, or sets it to a specific threshold. This enables a rapid interference suppression response to interference situations and has high real-time performance. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0046] Figure 1 This diagram illustrates the principle framework of a narrowband interference suppression method for spread spectrum systems based on frequency domain digital filtering using local spreading codes at the receiver.

[0047] Figure 2 A schematic diagram illustrating the technical principle of a narrowband interference suppression method for spread spectrum systems based on frequency domain digital filtering using local spreading codes at the receiver.

[0048] Figure 3 This schematic diagram illustrates the structure of a narrowband interference suppression device for a spread spectrum system based on frequency domain digital filtering of the local spreading code at the receiver, according to Embodiment 1 of the present invention.

[0049] Figure 4 This schematic diagram illustrates the structure of the local spreading code generation unit according to the present invention.

[0050] Figure 5 This schematic diagram illustrates the structure of the signal processing unit according to the present invention.

[0051] Figure 6 This schematic diagram illustrates the structure of a narrowband interference suppression device for a spread spectrum system based on frequency domain digital filtering of the local spreading code at the receiver, according to Embodiment 2 of the present invention.

[0052] The correspondence between component names and reference numerals in each figure is as follows:

[0053] 1. Spread spectrum signal input unit; 2. Interference sensing unit; 3. Local spreading code generation unit; 4. Signal processing unit; 5. Control unit; 6. First digital-to-analog converter unit; 7. Second analog-to-digital converter unit; 8. Second digital-to-analog converter unit;

[0054] 21. Control and decision command input port;

[0055] 31. Local spreading code parameter memory; 32. Local spreading code frequency domain parameter controller; 33. IFFT processor; 34. Local spreading code waveform output port;

[0056] 41. Spread spectrum signal despreading processor; 42. Despread signal frequency converter; 43. Despread signal filter; 44. Wideband spread spectrum digital signal input port; 45. Local spread spectrum code waveform input port; 46. Despread signal output port. Detailed Implementation

[0057] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0058] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0059] like Figure 1 As shown, the present invention provides a method for narrowband interference suppression in a spread spectrum system based on frequency domain digital filtering of the local spreading code at the receiver, comprising the following steps:

[0060] Interference sensing is performed on the spread spectrum signal input to the receiving end to obtain interference sensing information of narrowband interference;

[0061] Based on the interference sensing information and the anti-interference strategy of the spread spectrum system, the local spreading code is subjected to frequency domain comb-tooth digital filtering.

[0062] Perform an inverse Fourier transform on the filtered local spreading code spectrum to obtain the local spreading code time-domain waveform;

[0063] The local spreading code time-domain waveform is multiplied by the input spreading signal to achieve narrowband interference suppression;

[0064] The signal that has completed narrowband interference suppression is then spread spectrum synchronized and despread.

[0065] This invention achieves interference suppression by performing frequency-domain comb-like digital filtering on the local spreading code waveform at the receiving end of the spread spectrum system and by performing despreading on the received spread spectrum signal using the local spreading code waveform. This reduces the complexity of signal processing at the receiving end and improves the broadband anti-interference capability of the spread spectrum system.

[0066] In this invention, interference sensing of the spread spectrum signal input to the receiving end includes:

[0067] Using a spectrum estimation method, with a fast refresh rate at frequency resolution granularity, the interference threshold within the spread spectrum signal bandwidth is determined, as well as the interference type, occupied bandwidth, center frequency, and average power exceeding the interference threshold.

[0068] Anti-interference decisions are made according to the anti-interference strategy of the spread spectrum system, and interference suppression parameters are generated; the interference suppression parameters include the number of local spreading code frequency domain comb levels, comb power attenuation factor, and timestamp.

[0069] The frequency resolution granularity is smaller than the frequency domain comb spacing of the local spreading code.

[0070] In this invention, the frequency domain comb digital filtering process includes:

[0071] Set the amplitude value of the frequency component in the local spreading code spectrum corresponding to the frequency of the narrowband interference signal to zero, or set it to a specific threshold.

[0072] Because interference states can change rapidly over time, the interference suppression function of a spread spectrum system needs to respond quickly based on the interference state. While rapid perception of broadband interference situations is relatively easy to achieve, the computational complexity of high-speed time-frequency (FFT) and frequency-time (IFFT) transformations of broadband spread spectrum signals is enormous, making a rapid response difficult. Therefore, existing frequency domain interference suppression methods for spread spectrum signals are ineffective in dealing with rapidly changing interference.

[0073] The local spreading code's time-domain waveform is pseudo-random and periodic, and its IFFT transform calculation parameters are stable. This invention only targets frequency-domain interference suppression for the local spreading code's frequency-domain comb. The relevant parameters are easily inferred from the interference perception information. The frequency-domain comb digital filtering of the local spreading code can be completed by directly setting the amplitude encoding codeword of the local spreading code to zero or setting it to a certain threshold parameter. It has real-time performance and can achieve rapid interference suppression response to interference situations.

[0074] The principle of the narrowband interference suppression method for spread spectrum systems based on receiver-side local spreading code frequency domain digital filtering provided by this invention is as follows:

[0075] The technical principle of this invention is as follows: Figure 2 As shown. The spread spectrum signal received at system input port 1 contains a spectrally broadened data signal, a narrowband interference signal, and a white noise signal, which can be represented as follows:

[0076] r(t)=s(t)+i(t)+n(t) (1)

[0077] r(t) is the received spread spectrum signal, s(t) is the transmitted spread spectrum signal, i(t) is the narrowband interference signal, and n(t) is the noise. s(t) is expressed as...

[0078] s(t)=d(t)·p t (t)·c(t) (2)d(t) is the waveform of the data signal with a data period of T. d bandwidth is p t (t) is the spreading code waveform at the transmitting end, with a chip period of T. c The bandwidth is W = 1 / T c The spreading code bandwidth is much larger than the data bandwidth, so W >> B. c(t) is the carrier of the spreading signal.

[0079] For simplicity, assume the spread spectrum system has a short code and satisfies T d / T c =L, where L is a positive integer. The system transmission path and receiver response are ideal, the receiver has completed synchronization, and the receiver's local spreading code waveform p l (t) and the spreading code waveform p at the transmitting end t (t) are exactly the same. The system channel is a Gaussian channel. The received spread spectrum signal r(t) is identical to the local spreading code p at the receiver. l Multiplying (t) and the local oscillator l(t) completes the received despreading of the spread spectrum signal, resulting in the received despread signal r1(t), which is expressed as:

[0080] r1(t)=d(t·p t (t)·c(t)·p l (t)·l(t)+i(t)·p l (t)·l(t)+n(t)·p l (t)·l(t) (3)

[0081] Since the local spreading code is exactly the same as and synchronized with the received spreading signal, there is usually a relationship p. t (t)p l r1(t) = H, where H is a constant. Then r1(t) can be expressed as...

[0082] r1(t)=d(t)·H·c(t)·l(t)+i(t)·p l (t)·l(t)+n(t)·p l (t)·l(t) (4)

[0083] Formula (4) consists of three terms. The first term, d(t)·H·c(t)·l(t), is the data signal restored after frequency conversion and despreading by multiplying the received spread spectrum signal with the local spreading code and the local oscillator. Its spectrum is compressed, and the energy is mainly concentrated within the data bandwidth B. The second term, i(t)·p l (t)·l(t) represents the spectrally broadened signal resulting from the multiplication of the narrowband interference signal with the local spreading code and the local oscillator, with energy distributed across the spreading bandwidth W. The third term is n(t)·p.l (t)·l(t) is the noise signal after multiplying the noise with the local spreading code and the local oscillator, which is still broadband noise.

[0084] After processing such as integration or narrowband filtering, the data signal d(t) is completely preserved, while out-of-band interference and broadband noise after spreading are significantly suppressed, leaving only some residual interference and noise within the bandwidth B. This improves the system's signal-to-noise ratio (SNR) and signal-to-interference ratio (SNR). In spread spectrum systems, the improvement in SNR and SNR achieved through spread spectrum despreading can be characterized by the spread spectrum processing gain, i.e., G = W / B.

[0085] When the power of the narrowband interference signal is low, the spread spectrum processing gain can ensure that the system has a sufficient demodulation signal-to-noise ratio. However, when the power of the narrowband interference signal is high, and residual interference within bandwidth B becomes the main factor affecting signal demodulation, the system will be unable to effectively perform synchronization and data signal demodulation due to insufficient processing gain. In this case, the spread spectrum system must perform additional interference suppression processing on the narrowband interference signal to ensure a sufficient demodulation signal-to-noise ratio.

[0086] Additional narrowband interference suppression methods mainly include time-domain adaptive interference suppression methods and frequency-domain (transform domain) adaptive interference suppression methods. Currently, frequency-domain methods primarily focus on frequency-domain interference suppression of the r(t) signal. A typical process involves performing a time-frequency transform on the r(t) signal to obtain its spectrum, automatically identifying the amplitude-frequency characteristics of the narrowband interference i(t) in the spectrum, then performing processing such as setting the amplitude parameter of the narrowband interference to zero in the frequency domain. The processed r(t) is then subjected to a time-frequency transform again to obtain the interference-suppressed r(t) signal waveform. This waveform is then combined with the local spreading code p. l (t) Synchronization and despreading are performed. This method requires two transformations of the input spread spectrum signal: time-frequency (FFT) and frequency-time (IFFT). For broadband spread spectrum systems, this poses significant challenges in terms of broadband high-speed analog-to-digital conversion, data processing volume, and response time of interference suppression.

[0087] To address this issue, this invention proposes a novel frequency domain interference suppression method for narrowband interference in spread spectrum systems. This method achieves narrowband interference suppression during the despreading and filtering (or integration) processes of the received spread spectrum signal with the local spreading code by setting the amplitude-frequency parameters of the local spreading code. In this process, only one IFFT transform calculation is required to generate p... l (t) waveform, without the need for broadband high-speed analog-to-digital conversion and high-speed FFT transformation, can achieve efficient narrowband interference suppression and broadband spread spectrum signal reception and despreading, thereby improving the technical performance of broadband spread spectrum systems in dealing with narrowband interference.

[0088] For simplicity, we make simple model assumptions for the spreading code waveform, data signal waveform, and interference signal. Typically, the spreading code is an M-sequence, and the spreading code waveform p(t) is a bipolar BPSK modulated waveform. p(t) is periodic, and its waveform is represented as follows:

[0089]

[0090] Its spectrum is represented as

[0091]

[0092] In formulas (5) and (6), A k , Let and kf0 be the amplitude, phase, and frequency of the k-th Fourier series of the spreading code waveform, respectively. f0 is the repetition frequency of the spreading code, satisfying f0 = 1 / T. d T d The length of the data bits is T, and the length of the spreading code chip is T. c The condition G=T is satisfied between them. d / T c Clearly, the frequency domain characteristics of the spreading code exhibit a discrete comb-like spectrum, with each level of the Fourier series corresponding to a discrete comb tooth. It is easy to derive that the average power of the spreading code is approximately...

[0093] The data waveform d(t) is a bipolar BPSK modulated waveform with a spectrum D(f). The interference signal is a point-frequency interference, represented as...

[0094]

[0095] The spread spectrum signal carrier and local oscillator are respectively Know The average power of the spread spectrum signal is

[0096]

[0097] The average power of the received despread signal r1(t) is expressed as:

[0098]

[0099] Where P data PSD is the average power of the data signal. noise (f) represents the average power spectral density of noise in the received spread spectrum signal before despreading. IF =f l -f c It is the difference frequency between the local oscillator and the spread spectrum carrier. m is the m-th level comb of the local spreading code corresponding to the interference frequency. This comb converts the interference signal to the data bandwidth after despreading, affecting the demodulation of the data signal.

[0100] The spread spectrum signal power in formula (8) mainly consists of three parts, the first term being... The average power of the spread spectrum data signal is compared to the average power P of the original data signal. data The average power of the data signal increased after spread spectrum. times, H is the carrier contribution, and H is the spreading code contribution. (Second term) This represents the average power of the interfering signal. The third term is PSD. noise (f)·W is the average noise power within the spread spectrum signal bandwidth W.

[0101] The despread received signal power in formula (9) mainly includes three parts, the first term The average power of the despread data signal is compared to the average power P of the original data signal. data The average power of the data signal increased after spread spectrum. times, For carrier contribution, H 2 Contributed to spreading codes, Contribution to Benzo. Second item. This is the average power of the interference signal within the data bandwidth after despreading. This is the contribution of the m-th order comb tooth of the local spreading code corresponding to the interference frequency. (Third term) This represents the average noise power within bandwidth B after despreading.

[0102] According to formulas (8) and (9), the signal-to-interference ratio (SIR) and signal-to-noise ratio (SNR) before and after receiving despreading are respectively...

[0103]

[0104]

[0105]

[0106]

[0107] Formulas (10-1) and (10-2) represent the signal-to-interference ratio (SIR) and signal-to-noise ratio (SNR) before despreading, respectively, while (11-1) and (11-2) represent the SIR and SNR after receiving and despreading, respectively. Clearly, the change in SNR before and after receiving and despreading is... That is, the signal-to-noise ratio (SNR) is improved by a factor of G after receiving and despreading. The SNR changes as follows:

[0108]

[0109] Since the envelope of the spectrum P(f) of the bipolar BPSK spread spectrum waveform based on the M-sequence is a sinc function, the above equation has a maximum value when m = ±1. The signal-to-interference ratio (SIR) has a minimum value when the interference signal is located near the center carrier of the spread spectrum signal. Therefore, formula (12) can be approximated as follows:

[0110]

[0111] The above formula shows that interference signals are significantly suppressed during the receiving and despreading process, and the signal-to-interference ratio is increased to be greater than or equal to the spread spectrum processing gain G.

[0112] However, as mentioned earlier, if the interference power in the spread spectrum signal is very high, and the residual interference in the data bandwidth after despreading still significantly degrades the signal demodulation, then it is necessary to improve the system's anti-interference capability through supplementary interference suppression measures.

[0113] To address the aforementioned issues, we consider improving the local spreading code waveform p while suppressing interference frequency distribution. l In (t), the m-th order comb tooth is filtered out first to generate a new local spreading code waveform p. l+del (t). Then, the received spread spectrum signal r(t) is despread to obtain the received despread signal r2(t) under interference suppression.

[0114] r2(t)=d(t·p t (t)·c(t)·p l+del (t)·l(t)+i(t)·p l+del (t)·l(t)+n(t)·p l+del (t)·l(t) (14)

[0115] Its average power is expressed as

[0116]

[0117] The despread received signal power under interference suppression conditions in formula (15) mainly includes three parts, the first term The signal average power is compared to the original data signal average power P. data The average power of the data signal increased after spread spectrum. times, This is the power contribution of the spreading code under the condition of interference suppression by the m-th order comb filter of the local oscillator spreading code. (Second term) P is the average power of the suppressed interference signal within the data bandwidth after despreading reception. Threshold This represents the power attenuation factor of the m-th order comb tooth of the local spreading code corresponding to the interference frequency. (Third term) This represents the average noise power within bandwidth B after despreading. This represents the power contribution of the spreading code under the condition of interference suppression by the m-th order comb-tooth filtering of the local oscillator spreading code.

[0118] According to formula (15), the signal-to-interference ratio (SIR) and signal-to-noise ratio (SNR) after receiving and despreading under interference suppression conditions are respectively...

[0119]

[0120]

[0121] As shown in formula (16-1), the signal-to-interference ratio (SIR) after receiving and despreading is improved by interference suppression compared to that without interference suppression. The value is times greater than the center carrier frequency of the spread spectrum signal, and has a minimum value when the interference signal is located near the center carrier frequency of the spread spectrum signal, approximately equal to... Under interference suppression conditions, the change in signal-to-interference ratio (SIR) before and after receiving and despreading is: That is, the signal-to-interference ratio is improved after receiving and despreading. The power attenuation factor P of the m-th level comb of the local spreading code corresponding to the interference frequency. Threshold When P is sufficiently large, it can significantly suppress residual interference within the bandwidth of the received despread data signal, thereby improving the demodulation performance of the data signal. For example, when P... Threshold When the signal-to-interference ratio is G, the signal-to-interference ratio is (G-1). 2 Since G >> 1 in the spread spectrum system, the overall interference suppression level will reach ∝ G. 2 .

[0122] The above analysis demonstrates the typical technical performance of interference suppression using local spreading code frequency domain comb filtering when a single point-frequency interference exists in a spread spectrum system. This method remains effective for other types of narrowband interference and situations where multiple narrowband interferences coexist. For example, when the interference occupies 10% of the total bandwidth W of the spread spectrum signal, the worst-case changes in the signal-to-interference ratio (SIR) and signal-to-noise ratio (SNR) before and after despreading under interference suppression conditions are approximately:

[0123]

[0124]

[0125] As shown in formulas (17-1) and (17-2), for a broadband interference signal occupying 10% of the total bandwidth W of the spread spectrum signal, the receiving system can still achieve interference suppression and signal demodulation. However, when the total interference occupies a very wide bandwidth, it will lead to a deterioration of the received despread signal-to-noise ratio (SNR), making it difficult to balance the improvement of interference suppression level and SNR, and the demodulation performance of the data signal cannot be guaranteed. Therefore, the application conditions of the method described in this invention require targeted measures based on the bandwidth, SNR, SNR, and interference distribution of the spread spectrum signal, and it is not applicable to all interference situations.

[0126] Example 1

[0127] This embodiment provides a narrowband interference suppression device for a spread spectrum system based on frequency domain digital filtering of local spread spectrum code at the receiver, including a frequency signal input unit 1, an interference sensing unit 2, a local spread spectrum code generation unit 3, a signal processing unit 4, and a control unit 5.

[0128] The structure of the narrowband interference suppression device for a spread spectrum system based on local spread spectrum code frequency domain digital filtering provided in this embodiment is as follows: Figure 3 As shown in the diagram, this method utilizes fully digital domain signal processing to achieve the processes of receiving, despreading, and suppressing interference in spread spectrum signals. For simplicity, the essential functional units of a spread spectrum system, such as the local oscillator, RF front-end, and synchronization, are not shown in the block diagram, but this does not affect the description of the technical implementation method.

[0129] The spread spectrum signal input unit 1 is used to receive the input spread spectrum signal and output the spread spectrum signal in two paths. The spread spectrum signal input unit 1 includes a first digital-to-analog converter unit 6, which has two input and two output paths, respectively connected to the interference sensing unit 2 and the signal processing unit 4.

[0130] The spread spectrum signal input unit 1 receives the analog signal of the spread spectrum signal containing interference. After being output from the spread spectrum signal input unit 1, this signal first enters the first digital-to-analog converter unit 6 for analog-to-digital conversion, converting the analog waveform of the spread spectrum signal into a digital waveform. The digital signal of the spread spectrum signal containing interference output from the first digital-to-analog converter unit 6 is split into two paths, which enter the interference sensing unit 2 and the signal processing unit 4 respectively.

[0131] Interference sensing unit 2 is mainly used to sense narrowband interference within the spread spectrum signal band, acquire interference sensing information of the narrowband interference signal, and generate interference suppression parameters. Interference sensing unit 2 senses narrowband interference within the spread spectrum signal band and can use commonly used spectral estimation methods with a coarse frequency resolution and fast refresh method to determine the interference threshold within the spread spectrum signal bandwidth, as well as interference sensing information such as the type of interference exceeding the threshold, occupied bandwidth, center frequency, and average power. It then makes anti-interference decisions according to the anti-interference strategy of the spread spectrum system and generates interference suppression-related parameters. These parameters include the number of comb teeth in the local spreading code frequency domain, the comb tooth power attenuation factor, and the timestamp.

[0132] Interference sensing unit 2 sends interference sensing information and interference suppression parameters to local spreading code generation unit 3, and performs digital filtering of local spreading code frequency domain comb to achieve interference suppression on signal processing unit 4.

[0133] In this context, the frequency resolution granularity for interference sensing should generally be smaller than the comb spacing of the local spreading code in the frequency domain, so as to clearly identify the comb interval where the interference is located and the interference bandwidth occupancy. For ease of frequency domain digital processing, a typical value for the frequency resolution granularity can be set to n, where n is a positive integer. While ensuring accurate and effective interference situational awareness, the frequency resolution granularity should not be too small to improve the system's response rate for interference sensing and suppression. For example, a typical value of n of 8 can guarantee both accurate interference situational awareness and a fast response rate.

[0134] like Figure 4 As shown, the local spreading code generation unit 3 includes a local spreading code parameter memory 31, a local spreading code frequency domain parameter regulator 32, an IFFT processor 33, and a local spreading code waveform output port 34. Interference sensing information and interference suppression parameters generated by the interference sensing unit 2 are input to the local spreading code frequency domain parameter regulator 32 in the local spreading code generation unit 3 via the control and decision command input port 21. The local spreading code frequency domain parameter regulator 31 extracts the local spreading code frequency domain digital codeword parameters stored in the local spreading code parameter memory 31, and performs frequency domain comb amplitude digital filtering processing on the local spreading code according to the interference suppression decision parameters. This interference suppression control frequency domain comb digital filtering processing includes setting the amplitude value of the frequency component in the local spreading code spectrum corresponding to the frequency of the narrowband interference signal to zero, or setting it to a specific threshold. The local spreading code frequency domain parameter regulator 31 then inputs the regulated frequency domain parameters to the IFFT processor 33 for frequency-time transformation to generate the local spreading code time domain waveform. The local spreading code time-domain waveform generated by the IFFT processor 33 is output to the signal processing unit 4 via the local spreading code waveform output port 34 to perform reception despreading and interference suppression processing of the spread spectrum signal. In addition, the control and decision command input port 21 can also receive control commands input by the control unit, such as new local spreading code sequences, clock synchronization parameters, etc.

[0135] like Figure 5 As shown, the signal processing unit 4 includes a spread spectrum despreading processor 41, a despreading signal frequency converter 42, a despreading signal filter 43, and three ports for signal input or output: a wideband spread spectrum digital signal input port 44, a local spread spectrum code word waveform input port 45, and a despreading signal output port 46. The wideband spread spectrum digital signal input port 44 is used to receive the wideband spread spectrum digital signal output by the first digital-to-analog converter 6, the local spread spectrum code word waveform input port 45 is used to receive the local spread spectrum code digital waveform signal output by the local spread spectrum code generation unit 3, and the despreading signal output port 46 is used to output the despreading signal.

[0136] The signal processing unit 4 is used to perform synchronization, despreading, filtering, or integration processing on the time-domain waveforms of the spread spectrum signal and the local spread spectrum code to generate a baseband data signal, and to filter the data signal to suppress out-of-band interference and noise, thereby improving the signal-to-noise ratio and signal-to-interference ratio.

[0137] The broadband spread spectrum digital signal and the local spread spectrum code digital waveform received by the signal processing unit 4 are despread on the spread spectrum signal despreading processor 41. The spread spectrum signal is despread and compressed, and the data signal is restored. The despread signal generated by the spread spectrum signal despreading processor 41 is input to the despread signal inverter 42, and down-converted by the local oscillator to generate the data baseband. The baseband data signal is low-pass filtered in the despread signal filter 43 to suppress out-of-band interference and noise, improve the signal-to-noise ratio and signal-to-interference ratio, and finally output as a baseband low-pass data signal to the back-end processor via the despread signal output port 46 for signal demodulation.

[0138] The main function of the control unit 5 is to control each functional unit, including setting and controlling the working status, timing, local spreading code version, and received signal gain control of each functional unit. For example, the frequency resolution, refresh rate, and number of calculation points of the interference sensing unit 2; the spreading code version selection of the local spreading code parameter memory 9; the adaptive adjustment of the spreading code frequency domain amplitude and phase parameters of the local spreading code frequency domain parameter regulator; and providing the system with a high-precision frequency (clock) reference.

[0139] Example 2

[0140] like Figure 6 As shown, this embodiment provides a narrowband interference suppression device for a spread spectrum system based on frequency domain digital filtering of the local spreading code at the receiver. This method combines analog and digital signal processing to suppress spread spectrum signal interference. The signal transformation process is exactly the same as in Embodiment 1, and the interference sensing unit 2, local spreading code generation unit 3, and control unit 5 are the same as in Embodiment 1. The difference lies in the implementation or requirements of the second digital-to-analog conversion unit 8 and the signal processing unit 4 in this embodiment, which are different from those in Embodiment 1. In addition, a second analog-to-digital conversion unit 7 is added.

[0141] The spread spectrum signal input unit 1 receives a broadband spread spectrum analog signal containing interference. This signal is split into two paths, which enter the second analog-to-digital conversion unit 7 and the signal processing unit 4, respectively.

[0142] The second analog-to-digital converter (ADC) 7 performs analog-to-digital conversion on the spread spectrum signal, outputting a digital signal containing interference to the interference sensing unit 2 for interference detection. Compared to Embodiment 1, the technical parameters of the second ADC 7 in this embodiment are less demanding. Since the interference sensing unit 2 requires high digital bandwidth for interference detection of the spread spectrum signal but low amplitude resolution and noise requirements, the second ADC 8 in this embodiment can employ a wideband, high-speed, low-resolution ADC. Such ADCs are low-cost and have a small output data volume. In contrast, the first ADC 6 in Embodiment 1 needs to meet the requirements of the signal processing unit 4 for high-speed, wideband, high-precision, and low-noise ADC conversion, resulting in a high-cost ADC and a large output data volume.

[0143] The functional flow of the interference sensing unit 2 and the local spreading code generation unit 3 is the same as in Embodiment 1. The interference sensing unit 2 performs interference sensing on the narrowband interference within the spread spectrum signal band, obtains the interference sensing information of the narrowband interference signal, and generates interference suppression parameters. The local spreading code generation unit 3 stores the encoding information of the local spreading code, and performs frequency domain comb-tooth digital filtering on the local spreading code according to the interference sensing information and the interference suppression parameters. The filtered local spreading code is then subjected to IFFT transformation to generate the time domain waveform of the local spreading code.

[0144] The local spreading code waveform output by the local spreading code generation unit 3 is sent to the digital-to-analog converter unit 21 to convert the digital waveform into an analog waveform. Although the digital-to-analog conversion of the local spreading code waveform requires a high sampling rate and bandwidth, the requirements for noise and accuracy are lower than those of the first digital-to-analog converter unit 6 in Embodiment 1, and it is easier to implement and has a lower cost. Therefore, the digital-to-analog converter in the second digital-to-analog converter unit 8 is not the main technical bottleneck of the broadband spread spectrum system. The local spreading code analog waveform output by the second digital-to-analog converter unit 8 is sent to the signal processing unit 4 for analog domain frequency conversion, despreading, and filtering. The typical functional configuration of the signal processing unit 4 in this embodiment is the same as that in Embodiment 1, but its implementation is an analog device.

[0145] Furthermore, it should be noted that the present invention can be provided as a method, apparatus, or computer program product. Therefore, embodiments of the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, embodiments of the present invention can take the form of a computer program product implemented on one or more computer-usable storage media containing computer-usable program code.

[0146] Embodiments of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, terminal devices (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0147] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing terminal equipment to cause a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0148] It should also be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0149] Finally, it should be noted that the above description represents a preferred embodiment of the present invention. It should be pointed out that although preferred embodiments have been described, those skilled in the art, once they understand the basic inventive concept of the present invention, can make various improvements and modifications without departing from the principles described herein. These improvements and modifications should also be considered within the scope of protection of the present invention. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention.

Claims

1. An interference suppression method based on local spreading code frequency domain digital filtering, characterized in that, Includes the following steps: Interference sensing is performed on the spread spectrum signal input to the receiving end to obtain interference sensing information of narrowband interference; Based on the interference sensing information and the anti-interference strategy of the spread spectrum system, the local spreading code is subjected to frequency domain comb-tooth digital filtering. Perform an inverse Fourier transform on the filtered local spreading code spectrum to obtain the local spreading code time-domain waveform; The local spreading code time-domain waveform is multiplied by the input spreading signal to achieve narrowband interference suppression; The signal that has completed narrowband interference suppression is then spread spectrum synchronized and despread; The interference sensing of the spread spectrum signal input to the receiving end includes: Using a spectrum estimation method, with a fast refresh rate at frequency resolution granularity, the interference threshold within the spread spectrum signal bandwidth is determined, as well as the interference type, occupied bandwidth, center frequency, and average power exceeding the interference threshold. Anti-interference decisions are made according to the anti-interference strategy of the spread spectrum system, and interference suppression parameters are generated; the interference suppression parameters include the number of local spreading code frequency domain comb levels, comb power attenuation factor, and timestamp.

2. The interference suppression method based on local spreading code frequency domain digital filtering according to claim 1, characterized in that, The frequency resolution granularity is smaller than the frequency domain comb spacing of the local spreading code.

3. The interference suppression method based on local spreading code frequency domain digital filtering according to claim 1, characterized in that, The frequency domain comb digital filtering process includes: Set the amplitude value of the frequency component in the local spreading code spectrum corresponding to the frequency of the narrowband interference signal to zero, or set it to a specific threshold.

4. An interference suppression device based on local spreading code frequency domain digital filtering, used to implement the interference suppression method based on local spreading code frequency domain digital filtering as described in any one of claims 1 to 3, characterized in that, include: The spread spectrum signal input unit (1) is used to receive the input spread spectrum signal and output the spread spectrum signal in two paths. Interference sensing unit (2) is connected to the spread spectrum signal input unit (1) and is used to perform interference sensing on narrowband interference in the spread spectrum signal band, obtain interference sensing information of narrowband interference signal, and generate interference suppression parameters. The local spreading code generation unit (3) is connected to the interference sensing unit (2) and is used to store the encoding information of the local spreading code and perform frequency domain comb digital filtering on the local spreading code according to the interference sensing information and the interference suppression parameters. The filtered local spreading code is subjected to IFFT transformation to generate the time-domain waveform of the local spreading code. The signal processing unit (4) is connected to the spread spectrum signal input unit (1) and the local spread spectrum code generation unit (3), and is used to receive the spread spectrum signal and the local spread spectrum code time-domain waveform, and to perform synchronization, despreading, filtering or integration processing on the spread spectrum signal and the local spread spectrum code time-domain waveform; The control unit (5) is used to control each functional unit.

5. The interference suppression device based on local spreading code frequency domain digital filtering according to claim 4, characterized in that, The local spreading code generation unit (3) includes: The local spreading code parameter memory (31) is used to receive the interference sensing information and the interference suppression parameters; the interference sensing unit (2) is provided with a control and decision command input port (21), which is connected to the local spreading code parameter memory (31); The local spreading code frequency domain parameter regulator (32) is used to perform frequency domain comb-tooth digital filtering on the local spreading code according to the interference sensing information and the interference suppression parameters. An IFFT processor (33) is used to perform an IFFT transform on the filtered local spreading code to generate the time-domain waveform of the local spreading code. The local spreading code waveform output port (34) is used to output the local spreading code time domain waveform to the signal processing unit (4).

6. The interference suppression device based on local spreading code frequency domain digital filtering according to claim 5, characterized in that, The control and decision command input port (21) is used to receive control commands from the control unit (5).

7. The interference suppression device based on local spreading code frequency domain digital filtering according to claim 4, characterized in that, The signal processing unit (4) includes: The spread spectrum signal despreading processor (41) is used to despread the received spread spectrum signal and the local spread spectrum code time-domain waveform to obtain a despread signal; Despread signal inverter (42) is used to downconvert the despread signal via local oscillator to generate baseband data signal; Despread signal filter (43) is used to perform low-pass filtering on the baseband digital signal to generate a baseband low-pass data signal; The broadband spread spectrum digital signal input port (44) and the local spread spectrum code waveform input port (45) are respectively connected to the spread spectrum signal input unit (1) and the local spread spectrum code generation unit (3); The despread signal output port (46) is used to output the baseband low-pass data signal to the back-end processor for signal demodulation.

8. The interference suppression device based on local spreading code frequency domain digital filtering according to claim 4, characterized in that, The spread spectrum signal input unit (1) further includes: The first digital-to-analog converter (6) has its input terminal connected to the output terminal of the spread spectrum signal input unit (1), and its output terminal has two paths, which are respectively connected to the interference sensing unit (2) and the signal processing unit (4).

9. The interference suppression device based on local spreading code frequency domain digital filtering according to claim 4, characterized in that, Also includes: The second analog-to-digital converter (7) has its input terminal connected to one of the output terminals of the spread spectrum signal input unit (1); Its output terminal is connected to the input terminal of the interference sensing unit (2); The second digital-to-analog converter (8) has its input terminal connected to the output terminal of the local spreading code generation unit (3), and its output terminal connected to one input terminal of the signal processing unit (4).

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