101 results about "Pseudo random sequence" patented technology

Disclosed are an auxiliary pilot adaptive optimization method, apparatus and device, and a medium, which relate to the technical field of wireless communications, and solve the problems of static configuration, resource waste and single function of the existing auxiliary pilot. An auxiliary pilot frequency sequence is designed into a synchronous prefix and an estimation core section, and the synchronous prefix adopts a pseudo-random sequence with high autocorrelation and is used for timing synchronization (positioning through a sequence autocorrelation peak value) and frequency synchronization (calculating frequency offset through a phase difference) in a demodulation process; the estimation core section adopts an orthogonal sequence with a low peak-to-average ratio and is used for accurate channel estimation; the double-segment sequence is connected through a preset code pattern, and it is ensured that a demodulation end can perform synchronous analysis. By sensing the channel state in real time, parameters of the auxiliary pilot frequency are dynamically adjusted, and a synchronization function is fused, so that the demodulation performance and the resource utilization rate are improved.

The invention provides an image encryption method based on chaotic mapping and dynamic positioning generalized knight cruise, and the method comprises the following steps: reading a plaintext image P, and converting the plaintext image P into a pixel matrix with the size of the plaintext image P; a chaotic pseudo-random sequence is generated through three-dimensional Logistic chaotic mapping, and three integer pseudo-random sequences are obtained through integer processing and serve as parameters of a pixel matrix for a knight cruise scrambling method; two of the obtained integer pseudo-random sequences are used for controlling cruising of a rider on rows and columns respectively, so that scrambling operation is completed; and generating a chaos matrix by using a third integer pseudo-random sequence, carrying out XOR operation on the chaos matrix and the scrambled image matrix, changing an image pixel value, and completing image encryption to generate a ciphertext image C. The dynamic positioning generalized knight cruise scrambling method designed by the invention is simple in process, and the encryption efficiency can be remarkably improved.

The application provides a method and device for generating a pseudo-random sequence, an electronic device and a computer readable storage medium. The method comprises: performing AND operation and XOR operation on M bit values of a first sequence to obtain an (A+m)th bit value of the first sequence; wherein M is an integer greater than or equal to 1, and A is an integer greater than or equal to 0; and determining an mth bit value of the pseudo-random sequence according to the (A+m)th bit value of the first sequence.

This application discloses a communication method and apparatus. The method includes: A terminal device receives indication information, where the indication information indicates M combinations, and each combination includes one CS value and one comb offset value; or each combination includes a hopping value of one CS value and a hopping value of one comb offset value, where M is a positive integer. Then, the terminal device determines, based on the indication information, a first pseudo-random sequence, and a first time unit, a target CS value and a target comb offset value that correspond to a reference signal in the first time unit. Then, the terminal device sends the reference signal in the first time unit based on the target CS value and the target comb offset value.

The invention discloses a foreground and background calibration fused capacitor mismatch calibration method and system, and the method comprises the steps: carrying out foreground digital calibration after a chip is powered on, and comprises the steps: obtaining an error voltage; quantizing the obtained error voltage to generate a corresponding error code word; the weight of foreground calibration is obtained; the method comprises the following steps of: generating a pseudorandom sequence and injecting the pseudorandom sequence into an input signal of an ADC (Analog to Digital Converter) when an ADC (Analog to Digital Converter) enters normal work; carrying out weighted summation on the digital code word quantized and output by the ADC and eliminating the interference of the pseudo-random sequence from the digital code word; and carrying out correlation calculation on the weighted summation result after the interference of the pseudo-random sequence is eliminated and the pseudo-random sequence to obtain a calibration coefficient, and carrying out iterative calculation on the capacitance weight according to the calibration coefficient. The advantages of foreground calibration and background calibration are fully combined, so that a better calibration effect is achieved.

The invention discloses a radio analog telephone communication encryption method, device and equipment and a medium, and the method comprises the steps: generating a frequency spectrum segment number and a pseudo-random sorting sequence through a preset encryption algorithm; and carrying out controllable segmentation on the total spectrum of the analog voice according to a continuous sequence from low frequency to high frequency, carrying out sequence recombination on each sub-spectrum according to a pseudo-random sequence, finally combining and outputting encrypted voice, and recovering the original voice by utilizing the same pseudo-random sequence reverse recombination at a receiving end. Therefore, the time-frequency continuity and statistical characteristics of the voice spectrum in the traditional radio analog communication are fundamentally changed. According to the method, frequency spectrums are recombined as a whole according to a pseudo-random rule, so that an eavesdropper can only obtain disordered voice signals after the frequency spectrums are rearranged even if the eavesdropper intercepts the signals, and the difficulty of passive cracking means such as frequency spectrum analysis, filtering reduction and voice recognition is remarkably increased; the problem that in the prior art, radio analog telephone communication is insufficient in encryption and easy to crack is solved.

The invention relates to a pseudorandom sequence generation method and device and a medium, and the method comprises the steps: calculating weight vectors of different powers through modular operation based on a primitive polynomial of a Galois field, and obtaining a bit weight value of each bit; splitting the offset value into a plurality of accumulations in the form of power of 2 by using a binary decomposition method, and obtaining an initial vector at the offset position by combining the bit weight value at each bit; according to the bit width generation requirement, the one-dimensional weight matrix is expanded into a two-dimensional generation matrix based on the principle of a digital root method; based on the two-dimensional generation matrix, recursively calculating matrixes under different bit weights by using matrix power operation, and generating weight matrixes under different processing bit widths; generating a pseudorandom sequence starting point according to a mode of multiplying the initial vector at the offset position by the weight matrixes under different processing bit widths; and generating the pseudorandom sequence from the starting point of the pseudorandom sequence by using a recursive formula. According to the invention, waste of storage resources and bandwidth resources can be avoided.

The present application relates to the technical field of wireless communications. Disclosed are a communication method and a related apparatus. The method is applied to a first communication apparatus. The method comprises: sending first information to a second communication apparatus, the first information being used for indicating a first pseudo-random sequence, the first pseudo-random sequence being used for training a channel estimation model, the channel estimation model being used for predicting a channel between the first communication apparatus and the second communication apparatus, and the channel being predicted on the basis of the first pseudo-random sequence and a second pseudo-random sequence; and sending the second pseudo-random sequence to the second communication apparatus. The present application is used for keeping the model performance of channel estimation models during training.

The invention relates to the technical field of communication security, and particularly provides an encryption method based on a dynamic coupling image lattice, comprising the following steps: S1, acquiring to-be-encrypted constellation diagram data, and taking the constellation diagram data as plaintext data; s2, carrying out DNA coding on the plaintext data, then carrying out arithmetic operation, and then carrying out DNA anti-coding to complete data disturbance encryption; rules of DNA coding, operation and DNA anti-coding are determined through a preset method. The preset method comprises the following steps: S21, acquiring a key sequence, and dividing the key sequence; s22, generating a first intermediate one-dimensional pseudo-random sequence by using a first chaotic mapping model; s23, performing dynamic iteration on the first intermediate one-dimensional pseudo-random sequence by using a one-dimensional coupling mapping lattice model fused by a second chaotic mapping model to obtain a second intermediate one-dimensional pseudo-random sequence; and S24, determining the rules of DNA coding, operation and DNA anti-coding through the second intermediate one-dimensional pseudorandom sequence. The method is high in sequence randomness and high in communication security.

This invention belongs to the field of communication technology, and particularly relates to a code Doppler verification device and method. An initial pseudo-random sequence C(t) is periodically sent from a signal source to a wireless channel simulator. The wireless channel simulator adds a code Doppler effect to the acquired initial pseudo-random sequence C(t) to obtain a pseudo-random sequence C′(t), and sends the pseudo-random sequence C′(t) and the initial pseudo-random sequence C(t) to a spectrum and signal analyzer. The spectrum and signal analyzer performs orthogonal demodulation and low-pass filtering on the initial pseudo-random sequence C(t) and the pseudo-random sequence C′(t) to obtain a pseudo-random sequence C0. n (t) and pseudo-random sequence C′ m (t), and the initial pseudo-random sequence C(t) and the pseudo-random sequence C n (t) and pseudo-random sequence C′ m (t) is sent to the host computer; the host computer, based on the initial pseudo-random sequence C(t) and the pseudo-random sequence C... n (t) and pseudo-random sequence C′ m (t) Verify whether the added code Doppler is consistent with the effect of symbol compression or expansion caused by the actual speed.

A wireless power transmission system is provided for encoding (462, 526) a beacon signal in a wireless power delivery environment. The wireless power transmission system is used to encode a beacon signal to isolate a client device (546) for wireless (550) power delivery in a wireless power delivery environment. The beacon signal can be encoded or modulated (462) with a transmission code provided (524) to a selected client in the wireless power delivery environment. In this way, the beacon signal from the selected client can be identified and the corresponding client device is isolated for wireless power delivery (544, 546). In some embodiments, the transmission code can be a pseudo-random sequence used by the wireless power delivery client to encode the transmitted beacon signal.

This invention proposes an image encryption method, system, and decryption method and system, relating to the technical field of information security. It utilizes the computational holographic GS algorithm to encode the original image into a pure phase holographic encrypted image. Then, based on a pseudo-random block-based approach, a Logistic chaotic system is used to generate a pseudo-random sequence and obtain its complementary sequence. These two sequences are used to block-process the pure phase holographic encrypted image, generating two complementary sub-images. This avoids strong correlation between image pixels and ensures the reliability of encryption for each image pixel. Next, the Logistic chaotic system is used to perform a bitwise XOR operation on the block sub-images to obtain scrambled encrypted sub-images. Finally, the scrambled encrypted sub-images are synthesized into a complete encrypted image. This results in better encryption performance, a larger key space, and improved confidentiality and security during image transmission and use.

The embodiment of the invention provides an information acquisition method, if a DMRS is generated based on a ZC sequence, a root and / or cyclic shift amount corresponding to the ZC sequence is acquired, a target parameter corresponding to a single carrier SSB is carried through the root and / or cyclic shift amount, and the target parameter can be one or more of a cell identifier, an SSB index and a half-frame indication. That is, the amount of root and / or cyclic shift correlates with the value of the target parameter. In addition, the amount of root and / or cyclic shift also correlates with the length of the sequence corresponding to the DMRS. And if the DMRS is generated based on the pseudo-random sequence, obtaining related information corresponding to the pseudo-random sequence, and carrying a target parameter corresponding to the single carrier SSB through the related information. Wherein the related information comprises one or more of the initial value, the generator polynomial or the offset, and the related information is related to the value of the target parameter. Visibly, in the single carrier SSB, information related to the single carrier SSB is carried through the DMRS.

This application relates to a high-precision modeling method for low-Earth orbit (LEO) satellite orbits based on measured data correction. The method includes: first, acquiring measured orbital error data of in-orbit LEO satellites; setting the simulation scenario duration; periodically extending or pruning / segmenting the error data; generating a pseudo-random sequence using a 10-level feedback shift register; modulating and combining the pseudo-random sequence to obtain a first and a second sequence; filtering the valid second sequence through correlation calculation to obtain uncorrelated sequences for each segment; finally, combining and sampling according to the number of satellites, adding the orbital error to the error-free orbit to achieve high-precision modeling. This method can accurately reflect the characteristics of measured orbital errors, achieving high-precision modeling of LEO satellite orbits.

The invention discloses a demodulation reference signal sequence generation method and device, equipment, a medium and a product. The method comprises the following steps: determining a current signal index and a current time slot index, and determining a current index number according to the current signal index and the current time slot index; querying a predetermined register data table according to the current index number, and determining a current first state register value and a current second state register value; according to the method, iterative calculation is performed according to the current value of the first state register and the current value of the second state register to obtain a preset number of pseudo-random sequence values, and the demodulation reference signal sequence is generated according to the preset number of pseudo-random sequence values, so that the problem of computing resource waste in the demodulation reference signal sequence generation process is solved, and the demodulation reference signal sequence generation efficiency is improved. The register data table is generated in advance, the first state register value and the second state register value are stored through the register data table, the state register value is rapidly obtained, multiple iterations are not needed, computing resources are saved, and the sequence generation speed is increased.

The application discloses a video encryption method and device and a computer storage medium, and relates to the field of video encryption. The method comprises the following steps: calculating a spatial gradient amplitude and a motion vector field based on three continuous frames of an original video, calculating a motion activity to generate an activity tensor based on the two, constructing a complex seed-driven four-dimensional hyperchaotic mapping based on the activity tensor and a video resolution to generate three synchronous pseudo-random sequences, forming a heterogeneous encryption unit set based on the activity and a local Shannon entropy and an edge density product and combining dynamic modulation of the first pseudo-random sequence, mapping each heterogeneous unit into a virtual particle, constructing a chaotic potential field by the second pseudo-random sequence to simulate a virtual particle trajectory, and realizing pixel order rearrangement according to the trajectory, and generating a diffusion mask based on the third pseudo-random sequence to perform cross-frame XOR feedback diffusion on the result of the permutation. The application improves the security of video encryption.

A wireless device is configured to produce a signal in a time slot of a frame, wherein the time slots have variable lengths. The signal having a first portion and a second portion, wherein the first portion and the second portion are located in defined time regions in the slot. Further, the first portion having data and a multiplexed first pilot, wherein the multiplexed first pilot is derived from a pseudo random sequence, the second portion having a pilot sequence and a cyclic prefix. The wireless device transmits the produced signal in the time slot.

The invention discloses a generative image steganography method based on robust position mapping. According to the technical scheme, a steganography system composed of a run length coding module, an initial Gaussian noise generation module, a candidate pool processing module, a pseudorandom sequence generation module, an index sorting module, an information embedding module and a stable diffusion model SD is constructed. The run length coding module carries out run length coding on the secret information to obtain a two-tuple Y; an initial Gaussian noise generation module generates a Gaussian noise tensor zinit; the candidate pool processing module performs positive and negative value division on the zinit; the pseudo-random sequence module generates a random sequence P, and an index matrix S'is obtained through the index sorting module. The information embedding module embeds the secret sequence after run length coding in the Y into an empty tensor zemed to obtain a tensor zemed conforming to Gaussian distribution; and the SD carries out denoising on the zzzled and decodes the zzzled to generate a steganographic image. According to the method, the secret information extraction accuracy and steganography capacity can be effectively improved.

The present disclosure provides a sampling circuit, a control method and a hardware accelerator applied to a lattice cryptography algorithm, and relates to the technical field of post-quantum cryptography. The sampling circuit comprises a padding module configured to pad a seed according to a hash padding rule; a hash operation module configured to perform a hash operation on the padded seed to generate a pseudo-random sequence; a cache module configured to store the pseudo-random sequence generated by the hash operation module; and a sampling module configured to sample the pseudo-random sequence stored in the cache module to obtain a sampling result. The present disclosure provides the cache module, and in the sampling process, the cache module provides data for sampling to the sampling module without relying on the hash operation module to provide data. Therefore, the sampling module and the hash operation module in the present disclosure are independent of each other and can work simultaneously, thereby improving the operation efficiency of the sampling circuit and effectively accelerating the calculation process of the lattice cryptography algorithm.

The invention discloses a servo system mechanical resonance identification method based on a Welch algorithm, and the method is characterized in that a pseudo-random sequence signal is injected into a motor q-axis current instruction of a servo system, the real-time feedback speed of a motor is collected and recorded according to a preset sampling frequency, and finally a real-time feedback speed sequence with the length equal to that of the pseudo-random sequence signal is obtained; carrying out zero equalization, segmentation and windowing processing on the pseudo-random sequence signal and the real-time feedback speed sequence in sequence; according to the new pseudo-random sequence signal and the new real-time feedback speed sequence, the amplitude and the phase of the servo system are obtained through a Welch algorithm, so that a Bode diagram of the servo system is obtained; and finally, the mechanical resonance frequency of the servo system is obtained. The method has the advantages that the problem of resonance point misjudgment risk caused by frequency spectrum burrs of a traditional FFT method is fundamentally solved, and the method has the advantages of being high in noise immunity, high in frequency resolution and small in operand and can be widely applied to resonance monitoring and suppression of numerical control machine tools, robot joints and new energy transmission systems.

Embodiments of the present application provide a wireless signal transmission method and device, computer equipment and medium, and relate to the technical field of wireless communication, wherein the method comprises the following steps: if a signal frame sent by a signal sending party is detected, a pseudo-random binary output sequence is generated by a pseudo-random sequence generator using a time reference of a signal frame transmission time; the pseudo-random binary output sequence is bit by bit exclusive-ORed with a synchronization header and a training sequence according to the arrangement order of the synchronization header and the training sequence, to generate a randomized synchronization header and a randomized training sequence; the randomized synchronization header, the randomized training sequence and service load data are combined and sequentially output, and the output data is modulated; a time reference hopping time is calculated, and a modulated signal is transmitted to a signal receiving party at the time reference hopping time. The scheme completes randomization processing through a pseudo-random sequence, thereby improving the security of wireless communication signal transmission.

The embodiment of the application discloses a satellite network data sending method. The method comprises the following steps: acquiring satellite payload data packets; establishing data frames corresponding to the satellite payload data packets, wherein the data frames comprise first signal-to-noise ratio data frames, second signal-to-noise ratio data frames and third signal-to-noise ratio data frames; sending the data frames to a receiving end; and processing the data frames to obtain the satellite payload data packets. The working point ranges of the first signal-to-noise ratio data frames, the second signal-to-noise ratio data frames and the third signal-to-noise ratio data frames are greater than or equal to-15 dB and less than-10 dB, greater than or equal to-10 dB and less than 0 dB, and greater than or equal to 0 dB and less than 20 dB. The first signal-to-noise ratio data frames comprise a plurality of sub-first signal-to-noise ratio data frames, and the frame length of the sub-first signal-to-noise ratio data frames is the same as that of the second signal-to-noise ratio data frames and the third signal-to-noise ratio data frames. The unique code field of the frame header of the first signal-to-noise ratio data frames, the unique code field of the frame header of the second signal-to-noise ratio data frames and the unique code field of the frame header of the third signal-to-noise ratio data frames are selected from a pseudo-random sequence set.

The application discloses an image encryption method and system resisting chosen-plaintext attack, and the method comprises the following steps: generating initial values or parameters required by chaotic mapping by taking plaintext image hash value, timestamp and first key together; generating pseudo-random sequence required by image encryption by using pseudo-random number generator based on chaotic system; realizing point scrambling and pixel link diffusion operation of image pixels based on pseudo-random selection mechanism of pseudo-random sequence and multiple DNA encoding and operation; hiding plaintext image hash value and timestamp in extended image based on Chinese remainder theorem and second key, and obtaining final ciphertext image by performing XOR operation on the extended image and noise image generated based on third key. The method enhances the ability of resisting chosen-plaintext attack by making plaintext hash value and timestamp participate in encryption and hiding in ciphertext, and the relationship between plaintext image and ciphertext image depends on plaintext hash value and timestamp, so that the key management of the algorithm is superior to similar encryption algorithms.

The invention discloses a multi-clock-domain digital logic self-test module and an ADC chip, and belongs to the technical field of integrated circuits. The device is arranged in an ADC chip and interacts with an on-chip analog module and a plurality of digital logic modules to be tested; a control instruction of the ADC chip external host determines that the chip works in a user mode or a self-test mode; in the self-test mode, the self-test module switches clocks and signals of the to-be-tested modules; the self-test module generates a pseudo-random sequence, the pseudo-random sequence is injected into each to-be-tested module, pseudo-random output generated by each to-be-tested module is fed back to the self-test module for compression, and the self-test module generates a new pseudo-random sequence and continues to send the new pseudo-random sequence into each to-be-tested module; and comparing a self-test result obtained after a limited number of iterations with a preset result, if the self-test result and the preset result are completely matched, determining that the test is passed, otherwise, determining that the test is not passed. Self-testing can be carried out in the testing stage, the cost is effectively reduced, and the testing efficiency is considered.

The invention relates to the technical field of anti-unmanned aerial vehicles, and discloses a high-power microwave system and electronic countermeasure collaborative anti-unmanned aerial vehicle method and system, and the method comprises the steps: completing the configuration of an initial fixed frequency point; the working frequency of a high-power microwave signal emitted by a high-power microwave system is monitored and analyzed in real time, and main interference frequency information of the high-power microwave signal is captured; generating an initial frequency screening instruction based on the main interference frequency information; receiving actual frequency information, and comparing the deviation between the target frequency parameter and the actual frequency information; according to a frequency hopping parameter corresponding to the qualified frequency screening instruction, constructing a frequency hopping pattern by combining a pseudo-random sequence generated by a Logistic mapping algorithm; and generating an electronic countermeasure signal resistant to high-power microwave interference based on the frequency hopping pattern superposition modulation signal. According to the invention, the collaborative capability of high-power microwaves and electronic countermeasures can be effectively improved.

The application provides a key generation method, a register address scrambling method, a descrambling method and a chip. The key generation comprises generating a periodic pseudo-random sequence by using a linear feedback shift register, and generating an index value based on an original address; a sub-sequence is intercepted from the pseudo-random sequence according to the index value, and the bit width of the sub-sequence is the same as that of the original address; and a key is generated according to the sub-sequence and a static seed. The application utilizes a dynamic index mechanism, that is, the low bits of the original address are used as a variable index, to solve the problem of static mode address leakage. In addition, the application also realizes address consistency, that is, the static seed is used to ensure scrambling consistency of chips of the same type, and also realizes low resource consumption. The linear feedback shift register (PRBS) algorithm and the lightweight XOR operation are used, and compared with other complex encryption and hardware-level encryption, low delay and low consumption are brought, and the method is more suitable for register-level access.

The application discloses a model processing method and device, and belongs to the technical field of neural networks. The model processing method of the application embodiment comprises the following steps: in the training process of a large closed-loop cascaded model, generating a neuron discrete graph according to a maintained two-dimensional weight graph of neuron parameters, wherein the two-dimensional weight graph records the atomic weights and closed-loop weights of various neuron parameters of the atomic capabilities of the large closed-loop cascaded model; periodically generating a pseudo-random sequence, wherein the length of the pseudo-random sequence is equal to the number of weight values of the two-dimensional weight graph; performing an exclusive or operation on the pseudo-random sequence and the neuron discrete graph, and pruning the neurons according to the operation result. The application embodiment can increase the security of a systematic artificial intelligence system.

This invention discloses an internet cloud security thumbnail preservation encryption method based on chain-based sum-diffusion. The main steps are as follows: Extracting the plaintext image size information and invariant features such as pixel sums for each color channel, hashing and fusing them with the master key to generate a derived key related to the image content; using the derived key to drive a chaotic system to generate a pseudo-random sequence with anti-degradation performance; employing a binary space partitioning strategy to process the three channels of the image into irregular rectangular blocks; within each independent sub-block, globally scrambling the pixel positions according to the pseudo-random sequence; finally, based on a pseudo-random traversal path, performing a chain-based sum-diffusion cyclic shift operation on each scrambled sub-block to achieve non-linear diffusion of pixel values. This invention effectively eliminates cross-channel boundary leakage that may result from regular block partitioning while ensuring the semantic usability of the encrypted image at low resolution, and significantly enhances encryption security through a dual mechanism of "scrambling-chain-diffusion".

The application discloses an operational amplifier integrated with a dynamic self-calibration loop and a battery management system device. The device comprises: an analog front-end core for amplifying an input differential signal; a common-mode voltage extraction network for acquiring a transient common-mode signal; a pseudo-random sequence generator for generating a pseudo-random bit sequence; a quadrature injection modulator for performing polarity flipping modulation on the transient common-mode signal; an auxiliary transconductance compensation array for injecting a compensation current into a high-impedance node; a digital correlation extractor for performing correlation demodulation and accumulation operation to extract a common-mode mismatch error and update a calibration control word; and a battery state monitoring module for collecting signals through an operational amplifier. The application can realize real-time background tracking and accurate compensation of dynamic device physical mismatch in a continuous working mode without blocking the amplification of the main differential signal, eliminate chopping aliasing distortion, and maintain high micro-current measurement accuracy in a strong electromagnetic interference environment.

The embodiment of the invention discloses a signal processing method and system. The method is applied to a transmitting end, and comprises the following steps: acquiring a baseband signal to be transmitted, and determining a filter bandwidth of a channel where the baseband signal is located; determining the bandwidth of the pseudo-random sequence generated by the pseudo-random sequence generator based on the filter bandwidth; performing spread spectrum processing on the baseband signal based on the bandwidth of the pseudo-random sequence, and transmitting the radio frequency signal after the spread spectrum processing; wherein the bandwidth of the radio frequency signal after the spread spectrum processing is equal to the bandwidth of the filter. According to the technical scheme, the bandwidth of the pseudo-random sequence generated by the pseudo-random sequence generator can be determined through the bandwidth of the filter, and spectrum spreading processing is carried out on the baseband signal through the bandwidth of the pseudo-random sequence, so that the bandwidth of the baseband signal is expanded to be the same as the bandwidth of the filter; therefore, all useful signals of the baseband signals can pass through the filter, and useless out-of-band signals are just out of the band of the filter and can be filtered out, so that the signals can be better filtered.