An active spurious cancellation method and system based on symmetry of multi-DDS structure

Abstract

This invention provides an active spurious cancellation method and system based on the structural symmetry of multiple DDS (Digital Frequency Synthesis) systems, relating to the field of digital frequency synthesis technology. The method includes constructing at least two structurally symmetrical DDS channels; setting a global phase bias and initializing control parameters, including amplitude control parameters and phase control parameters for each DDS channel; using the global phase bias and the control parameters, coarsely canceling the structural spurious emissions from the multiple DDS channels to obtain a coarsely suppressed synthesized output signal; extracting residual spurious emissions from the synthesized output signal and adaptively iteratively updating the control parameters with the goal of minimizing the residual spurious emissions amplitude; re-performing coarse suppression using the updated control parameters and generating a synthesized output signal, stopping the iteration when the residual spurious emissions meet a preset suppression requirement. This invention solves the problem that existing spurious cancellation methods do not consider the coherent relationship between spurious components.

Description

Technical Field

[0001] This invention relates to the field of digital frequency synthesis technology, and more specifically, to an active spurious cancellation method and system based on the symmetry of multiple DDS structures. Background Technology

[0002] Direct digital frequency synthesizers (DDS) are widely used in radar, communications, and test and measurement fields due to their advantages such as high frequency resolution, controllable phase, and flexible modulation. However, in practical applications, DDS output signals inevitably contain spectral spurs, primarily caused by internal and external factors such as phase truncation errors, amplitude quantization errors, digital-to-analog converter (DAC) nonlinear distortion, and sampling clock jitter. These spurs severely degrade the system's spurious-free dynamic range (SFDR), limiting signal detection accuracy and anti-interference capabilities, becoming a core bottleneck restricting performance improvements in high-end DDS applications.

[0003] To address the aforementioned spurious energy problem, existing technologies have proposed various suppression schemes, which can be categorized into passive compensation and energy dispersion types, but all have significant limitations. For example, the passive compensation type employs a "main signal channel + independent correction branch" architecture. Its core logic involves extracting spurious features through high-speed sampling at the DDS output end, then specifically generating a correction signal with the same frequency, amplitude, and opposite phase as the spurious energy. Spurious energy cancellation is achieved through the synthesis of the main signal and the correction signal. The energy dispersion type, as shown in existing patent CN118113109A, increases the number of DDS channels and phase differences to disperse spurious energy in the frequency domain, thereby reducing local spurious energy intensity.

[0004] However, none of the above suppression schemes break through the design concept of passively dealing with spurious emissions, reveal the coherent relationship between multiple DDS spurious components, or provide technical means to actively construct spurious coherent cancellation conditions at the system level. Passive compensation-based suppression requires designing independent correction links for different spurious frequencies when facing broadband multi-frequency spurious emissions, leading to a surge in system complexity. Furthermore, it is a back-end remedial suppression method, unable to fundamentally improve the spurious emission mechanism, and is susceptible to factors such as ambient temperature drift and hardware parameter aging, limiting its suppression stability and depth. Energy dispersion-based suppression cannot achieve precise and deep suppression of specific strong spurious frequencies, and the spurious energy is only dispersed rather than eliminated, still potentially causing interference to sensitive frequencies in the system.

[0005] Therefore, there is an urgent need for an active spurious cancellation method that can fundamentally solve the inherent defects of existing technologies and provide a new technical path for broadband, deep, and stable spurious suppression. Summary of the Invention

[0006] The purpose of this invention is to provide an active spurious cancellation method and system based on the symmetry of multiple DDS structures, so as to improve the above-mentioned problems. To achieve the above objective, the technical solution adopted by this invention is as follows:

[0007] Firstly, this application provides an active spurious cancellation method based on the symmetry of multiple DDS structures, including:

[0008] Construct at least two DDS channels with symmetrical structure;

[0009] Set the global phase offset and initialize the control parameters, which include the amplitude control parameters and phase control parameters for each DDS channel;

[0010] By using the global phase bias and the control parameters, the multiple DDS channels are subjected to structural spurious coherence cancellation to obtain a coarsely suppressed synthetic output signal.

[0011] Residual spurious emissions are extracted based on the synthesized output signal, and the control parameters are adaptively iteratively updated with the goal of minimizing the residual spurious emissions amplitude.

[0012] The coarse suppression is re-performed using the updated control parameters, and a synthetic output signal is generated. The iteration stops when the residual spurious signals meet the preset suppression requirements.

[0013] Secondly, this application also provides an active spurious cancellation system based on the symmetry of a multi-DDS structure, comprising:

[0014] Modules for building at least two symmetrical DDS channels;

[0015] An initialization module is used to set the global phase offset and initialize control parameters, including amplitude control parameters and phase control parameters for each DDS channel.

[0016] The coarse suppression module is used to perform structural spurious coherence cancellation on multiple DDS channels through the global phase bias and the control parameters to obtain a coarsely suppressed synthesized output signal.

[0017] The optimization module is used to extract residual spurious signals based on the synthesized output signal and to adaptively iteratively update the control parameters with the goal of minimizing the residual spurious signal amplitude.

[0018] The iterative module is used to re-perform coarse suppression and generate a synthetic output signal using updated control parameters until the residual spurious emissions meet the preset suppression requirements, at which point the iteration stops.

[0019] The beneficial effects of this invention are as follows: This invention actively constructs spurious coherence cancellation relationships using the symmetry of a multi-DDS structure. Combined with closed-loop iterative optimization of structural coarse suppression and adaptive fine suppression, it achieves deep suppression of broadband multi-frequency spurious signals without the need for additional independent correction branches. Simultaneously, it achieves precise suppression through a spectral error function and breaks local minima traps by leveraging random phase perturbations, ensuring that the optimization converges to the global optimum. Furthermore, through structural symmetry-based active spurious coherence cancellation, combined with an adaptive iterative mechanism, it avoids the problem of increased system complexity in traditional passive compensation schemes and the spurious residue defects of energy-dispersed schemes. This provides an efficient, stable, and low-cost spurious suppression solution for scenarios with stringent signal purity requirements, such as radar and communications.

[0020] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the active spurious cancellation method based on the symmetry of multiple DDS structures described in this embodiment of the invention;

[0023] Figure 2 This is a schematic diagram of the S-structure stray coherence cancellation principle in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram comparing the spectra before and after spurious suppression in an embodiment of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] Example 1:

[0028] This embodiment provides an active spurious cancellation method based on the structural symmetry of multiple DDS structures.

[0029] See Figure 1 The figure shows that the method includes steps S1, S2, S3, S4 and S5.

[0030] Step S1: Construct at least two DDS channels with symmetrical structure;

[0031] Step S1 includes:

[0032] Step S11: Construct at least two DDS channels;

[0033] In this step, select DDS channel, Indicates the number of DDS channels. The specific requirements are determined by the spurious emission suppression needs and hardware resources of the actual application scenario. All channels use the same model of DDS chip or the same specification of FPGA logic resources, such as the AD9910 or XC7K325T FPGA built-in DDS IP core.

[0034] Step S12: Ensure that each DDS channel maintains structural symmetry in phase accumulation, table lookup, DAC, and sampling clock paths;

[0035] In this step, during the hardware circuit setup, each DDS channel includes four core units: a phase accumulator, a waveform ROM lookup table module, a digital-to-analog converter (DAC), and a low-pass filter (LPF). Furthermore, the power supply module, clock drive module, and signal amplification module of all DDS channels use the exact same component models and circuit parameters, such as the same type of LDO power supply chip and operational amplifiers with the same bandwidth.

[0036] It should be noted that this step requires hardware consistency design and unified configuration of logical parameters to achieve structural symmetry of the critical path.

[0037] Specifically, the phase accumulator bit width (e.g., 32-bit) and accumulation step control logic of all DDS channels are completely identical, and the same IP core configuration parameters are used in the FPGA implementation to make the phase accumulator symmetrical.

[0038] All DDS channels store the same sine / cosine wave sampling data in their waveform ROMs. The ROM depth (e.g., 1024 points) and quantization bit width (e.g., 16 bits) are exactly the same, and the lookup table address mapping logic is consistent, making the lookup table module symmetrical.

[0039] All DDS channels use the same type of DAC chip. The sampling rate, reference voltage, and output range parameters of the DAC are uniformly configured. A single clock source and power divider are used to provide sampling clocks for all DDS channels (such as a 1GHz temperature-controlled crystal oscillator) to ensure that the phase jitter and frequency deviation of each clock are consistent. The time delay difference of the clock arriving at each DDS chip is ≤1ns, ensuring the symmetry of the DAC and sampling clock paths.

[0040] Meanwhile, the DAC output of each DDS channel is connected to a low-pass filter of the same model and parameters (the cutoff frequency is set according to the target signal bandwidth). The gain and bandwidth of the amplifier circuit after the filter are completely consistent, making the subsequent conditioning circuit symmetrical.

[0041] Step S13: Input the same FTW to all DDS channels and collect the output spectrum of each DDS channel individually;

[0042] In this step, the exact same frequency control word (FTW) is input to all DDS channels to ensure that the target output frequency of each DDS channel is consistent.

[0043] Then disconnect the combined link of the multiple DDS channels and adopt the single-channel test mode. Sequentially turn on the output of each DDS channel individually and use a spectrum analyzer to collect the output spectrum of each DDS channel. During the test, the same frequency range (covering the predetermined spurious frequency points), resolution bandwidth and number of scans need to be set.

[0044] Step S14: Determine by the output spectrum that the spurious frequency positions of each DDS channel at the predetermined spurious frequency point are completely consistent and the phase difference is stable; otherwise, rebuild the DDS channel.

[0045] In this step, the spectrum data (frequency, peak amplitude, phase) of each DDS channel at the predetermined spurious frequency point is obtained by outputting the spectrum.

[0046] When determining spurious frequency consistency, it is necessary to compare the frequency values ​​of each DDS channel at the predetermined spurious frequency point. The frequency deviation must be less than the preset deviation (determined by the frequency accuracy of the spectrum analyzer). If the frequency deviation exceeds the preset deviation, it is necessary to check whether the FTW configuration is consistent and whether there is frequency drift in the clock source. After readjustment, the test should be repeated.

[0047] When determining the stability of the phase difference, it is necessary to calculate the phase difference between any two DDS channels at a predetermined spurious frequency. Ten sets of phase data are continuously collected, and the standard deviation of the phase difference is calculated. If the standard deviation is greater than the standard deviation threshold, the PCB trace delay and DAC synchronization need to be checked, and the hardware routing or clock synchronization scheme needs to be re-optimized.

[0048] If all DDS channels meet the requirements of completely consistent spurious frequency positions and stable phase difference, then the DDS channel with symmetrical structure is considered to have been successfully built, and the next step can be performed. If the above conditions are not met, the DDS channel needs to be rebuilt (replacing the components with poor consistency and optimizing the circuit design), and steps S11 to S14 are repeated until the judgment criteria are met.

[0049] It should be noted that when the FTW (main signal frequency) of the DDS channel remains unchanged, that is, when the main signal frequency remains unchanged, the position of the predetermined spurious frequency point is fixed; if the main signal frequency needs to be switched later, step S13 needs to be executed again to collect the single-channel spectrum under the new frequency and update the predetermined spurious frequency point list.

[0050] Step S1 ensures that the spurious signals from multiple DDS channels possess high coherence, which is the only hardware prerequisite for subsequent active spurious signal cancellation. It is understandable that the root causes of spurious signals are internal phase truncation and amplitude quantization errors within the DDS, as well as external clock jitter and circuit nonlinearity. Only by ensuring complete symmetry in the hardware and logic of multiple DDS channels can we guarantee that the spurious signals they generate are coherent signals with the same origin, frequency, amplitude, and stable phase difference.

[0051] Step S2: Set the global phase offset and initialize the control parameters, which include the amplitude control parameters and phase control parameters for each DDS channel;

[0052] Step S2 includes:

[0053] Step S21: Obtain the number of DDS channels;

[0054] Step S22: Calculate the initial global phase offset based on the number of DDS channels;

[0055] In this step, the core function of the initial global phase offset is to ensure that the spurious signals from multiple DDS channels form a uniformly distributed phase relationship during synthesis (e.g., 2 channels in opposite directions, 3 channels with a 120° phase difference), ensuring that the spurious vectors cancel each other out initially after superposition. Therefore, based on the principle of uniform distribution and cancellation of spurious vectors, the initial global phase offset... The calculation formula is:

[0056] ;

[0057] In the formula, This represents the initial global phase offset. Indicates the number of DDS channels.

[0058] It is understandable that spurious signals can be considered as complex vectors (containing amplitude and phase), when When the phase of the stray vector is uniformly distributed on a 360° circle, the total amplitude after the vector superposition will approach 0.

[0059] like Figure 2 As shown, at a certain spurious frequency point in the 2-channel DDS, when At that time, the two stray vectors are in opposite directions and completely cancel each other out when their amplitudes are equal. To achieve the coherent cancellation relationship of strays by actively constructing them, thereby reducing the stray amplitude at the source.

[0060] Figure 2 middle, and These represent the initial phases of DDS channel 1 and DDS channel 2, respectively. and These represent the spurious signal components of DDS channel 1 and DDS channel 2, respectively. , Since DDS channel 1 and DDS channel 2 have the same structure, their initial phase and amplitude are basically equal. Therefore, when the initial global phase offset is... When superimposed, the phases of DDS channel 1 and DDS channel 2 are approximately opposite, and the amplitudes of the stray components are equal, which can achieve coherent cancellation of strays.

[0061] Step S23: Fine-tune the initial global phase offset to obtain the global phase offset;

[0062] It should be noted that the multi-channel DDS system built in step S1 has inherent hardware deviations (such as PCB trace delay, DAC nonlinearity, and clock jitter), which cause a slight deviation between the actual spurious phase difference and the theoretical value. Therefore, fine-tuning is required.

[0063] Taking a 2-channel DDS system as an example, if directly using However, hardware deviations result in an actual phase difference of... The two spurious signals cannot be completely reversed, resulting in a higher residual spurious amplitude. By making small adjustments, the actual phase difference can be brought infinitely close to the theoretical cancellation value, significantly improving the effect of subsequent first-stage structural coarse suppression.

[0064] In this step, the initial global phase offset is fine-tuned within ±5° to obtain the global phase offset. .

[0065] Step S24: Set the initial values ​​of the amplitude control parameters and phase control parameters for each DDS channel.

[0066] In this step, the amplitude control parameter is set to 1.0, and the phase control parameter is set to 0°.

[0067] Step S3: Using the global phase bias and the control parameters, the multiple DDS channels are subjected to structural spurious coherence cancellation to obtain a coarsely suppressed synthesized output signal;

[0068] Understandably, most existing spurious suppression techniques involve generating spurious emissions first and then compensating for them. However, this step creates the physical conditions for spurious cancellation from the source by using a structurally symmetrical DDS channel and a global phase bias, thus achieving active spurious coherent cancellation.

[0069] Step S3 includes:

[0070] Step S31: Calculate the basic phase offset of each DDS channel using the global phase offset and the preset phase offset formula;

[0071] In this step, the basic phase bias... The calculation formula is:

[0072] ;

[0073] In the formula, Indicates the first Basic phase offset of the DDS channel , This indicates the DDS channel number index. , Indicates the number of DDS channels. This indicates the global phase offset.

[0074] Step S32: Calculate the actual phase offset of each DDS channel using the basic phase offset and phase control parameters of each DDS channel;

[0075] In this step, the actual phase offset is the superposition of the basic phase offset and the phase control parameters, which is used to compensate for residual hardware deviations and provide precise phase adjustment for stray coherence cancellation.

[0076] Actual phase offset The calculation formula is:

[0077] ;

[0078] In the formula, Indicates the first Actual phase offset of the DDS channel , Indicates the first Basic phase offset of the DDS channel , This represents the phase control parameters.

[0079] Step S33: Adjust the amplitude weighting of the output signal of the corresponding DDS channel by using the amplitude control parameters of each DDS channel;

[0080] In this step, the formula for calculating the magnitude weighting is:

[0081] ;

[0082] In the formula, Indicates the first Adjusting the output amplitude of the DDS channel , Indicates the first Amplitude control parameters of the DDS channel. Indicates the first Raw output amplitude of the DDS channel .

[0083] Step S34: Adjust the spurious phase of the corresponding DDS channel at the predetermined spurious frequency point by adjusting the actual phase offset of each DDS channel;

[0084] In this step, phase adjustment is only performed on predetermined spurious frequencies (such as the second harmonic and the third harmonic) to avoid affecting the phase of the main signal.

[0085] Step S35: Perform complex vector superposition on the output signals of all DDS channels after amplitude and phase control to obtain the synthesized output signal after coarse suppression.

[0086] This step increases the spurious suppression depth by dynamically constructing coherent destructive conditions, and the spurious suppression effect will not drift over time as long as the structure is symmetrical and the phase bias remains unchanged. Furthermore, spurious suppression is achieved solely through amplitude and phase control and vector synthesis of multiple DDS channels, eliminating the need for additional correction branches, thus reducing system size, power consumption, and cost, making it more suitable for integrated applications.

[0087] It should be noted that the correction branch in existing schemes may introduce additional noise and phase distortion, leading to a deterioration in the signal-to-noise ratio and phase noise of the main signal. However, this step explicitly adjusts only the phase of the predetermined spurious frequency point, keeping the phase and amplitude of the main signal synchronously superimposed. This not only avoids distortion but also increases the output power of the main signal due to multi-channel synthesis.

[0088] Step S4: Extract residual spurious signals based on the synthesized output signal, and adaptively iterate and update the control parameters with the goal of minimizing the residual spurious signal amplitude.

[0089] Step S4 includes:

[0090] Step S41: Perform frequency domain analysis on the target broadband frequency band of the synthesized output signal to extract key features of residual spurious signals. The key features of residual spurious signals include the frequency, peak amplitude and phase of the residual spurious signals.

[0091] In this step, frequency domain analysis employs one or more combinations of Fast Fourier Transform (FFT), sub-band energy detection, and frequency domain peak search. Residual spurious key features cover all predetermined spurious frequencies and newly emerging non-predetermined spurious frequencies after coarse suppression.

[0092] It should be noted that the main signal frequency and the residual spur frequency are two independent frequency domain components. The location of the residual spur can be determined by the frequency of the residual spur, while the phase of the residual spur can be used to determine the coherent cancellation state, thereby guiding the direction of phase parameter adjustment.

[0093] Step S42: To minimize the residual spurious amplitude, a spectral error function is established using the peak amplitude;

[0094] In this step, the core optimization objective is to minimize the sum of squared peak amplitudes of all residual spurs. This approach can simultaneously suppress spurs at multiple frequencies. Furthermore, weighting coefficients are introduced for residual spurs with different priorities (e.g., predetermined spur frequencies have higher priority than non-predetermined spur frequencies) to increase the suppression weight of high-priority spurs.

[0095] Therefore, the spectral error function is defined as follows:

[0096] ;

[0097] In the formula, This represents the global error function value. This represents the total amount of residual stray particles. Indicates the first The weighting coefficients of the residual strays, Indicates the first Peak amplitude of residual stray .

[0098] Step S43: Randomly generate a phase perturbation with limited amplitude, and superimpose the random phase perturbation with the actual phase offset of each DDS channel;

[0099] In this step, a small random phase perturbation is injected into the phase control path. This approach can break the local minima trap in the optimization process. Essentially, it breaks the periodicity of the phase truncation error by using small-amplitude pseudo-random phase perturbations, dispersing concentrated fixed-frequency spurious energy into broadband noise. The danger of fixed-frequency spurious energy lies in its concentration at a single or a few frequency points, easily causing strong interference to sensitive frequency bands of the system. However, broadband noise disperses energy across the entire target frequency band, with extremely low energy density at a single frequency point, resulting in negligible impact on system performance. Therefore, by introducing random phase perturbations, it is ensured that subsequent optimization algorithms converge to the global optimum. Indicates the first During iteration Random phase perturbation of the DDS channel, and , This indicates the upper limit of the disturbance amplitude.

[0100] It should be noted that the amplitude of the random phase perturbation is much smaller than that of the random phase perturbation. The magnitude is such that it only changes the coherent state of the residual stray signal without significantly affecting the phase stability of the main signal.

[0101] Step S44: Iteratively update the control parameters using the spectral error function and the DDS channel after superimposed perturbation.

[0102] Step S44 includes:

[0103] Step S441: Based on the output spectrum of all DDS channels after superimposed perturbation, extract the updated residual spurious features;

[0104] Step S442: Substitute the updated residual spurious features into the spectral error function to obtain the global error function value;

[0105] In this step, the error function values ​​before and after the perturbation are compared. If the error function value after the perturbation is less than the error function value before the perturbation, it means that the direction of this perturbation is conducive to spurious suppression. Otherwise, this perturbation is discarded, and a new random phase perturbation is generated for the next perturbation.

[0106] Step S443: For each DDS channel, calculate the partial derivative of the corresponding control parameter using the global error function value;

[0107] In this step, the partial derivatives are calculated using the small increment method, specifically the amplitude partial derivative and the phase partial derivative.

[0108] Step S444: Update the control parameters using the partial derivatives according to the gradient descent method to obtain the updated control parameters for each DDS channel.

[0109] In this step, the control parameters are updated along the negative gradient direction to ensure that the global error function value gradually decreases. The update formula is as follows:

[0110] ;

[0111] ;

[0112] In the formula, and They represent the first Second and third During the nth iteration Amplitude control parameters of the DDS channel. and They represent the first Second and third During the nth iteration Phase control parameters of the DDS channel, and These represent the learning rate for the amplitude parameter and the learning rate for the phase parameter, respectively. and These represent the amplitude partial derivative and the phase partial derivative, respectively.

[0113] Step S5: Perform coarse suppression again using the updated control parameters and generate a synthesized output signal until the residual spurious emissions meet the preset suppression requirements, then stop the iteration.

[0114] In this step, if the preset suppression requirement is met, that is, the spurious level drops below the preset spurious threshold, the iteration is stopped immediately, the current control parameters are locked, the parameter configuration of the DDS channel is maintained, and the stable output state is entered. Otherwise, a new round of random phase perturbation is generated, and the next adaptive iterative optimization process is started.

[0115] like Figure 3 As shown, the solid line represents the spectrum before suppression, and the dashed line represents the spectrum after spurious cancellation using the method of this invention. It can be seen that the amplitude of spurious emissions is significantly reduced.

[0116] It should be noted that if the hardware environment or operating state changes, such as temperature changes or Tile state changes, the structural symmetry of the multi-channel DDS needs to be recalibrated and iterative optimization re-performed. This is because the electrical parameters of hardware such as DDS chips and FPGAs drift with temperature, causing the structural symmetry conditions established in step S1 to be disrupted, and the amplitude and phase of spurious emissions to deviate from the optimal coherent cancellation state, resulting in an increase in residual spurious amplitude. A Tile typically refers to a functional module or computing unit (such as a DDS channel module or vector synthesis module in a multi-DDS system), and its state changes include channel start / stop, module fault recovery, and operating mode switching. These changes disrupt the original amplitude and phase consistency of the multi-channel DDS, leading to a decrease in spurious emission cancellation effectiveness.

[0117] Furthermore, the method of this invention can be implemented in an on-chip DDS core, in an FPGA internal NCO and external DAC combination system, and can also be applied to a multi-channel signal source composed of multiple independent DDS chips. For different hardware platforms, as long as the structural symmetry of the multiple DDS channels is maintained and programmable amplitude and phase control and feedback channels are provided, the structural spurious coherence cancellation and adaptive depth suppression proposed in this invention can be achieved.

[0118] Example 2:

[0119] This embodiment provides an active spurious cancellation system based on the structural symmetry of multiple DDS structures. The system includes:

[0120] Modules for building at least two symmetrical DDS channels;

[0121] An initialization module is used to set the global phase offset and initialize control parameters, including amplitude control parameters and phase control parameters for each DDS channel.

[0122] The coarse suppression module is used to perform structural spurious coherence cancellation on multiple DDS channels through the global phase bias and the control parameters to obtain a coarsely suppressed synthesized output signal.

[0123] The optimization module is used to extract residual spurious signals based on the synthesized output signal and to adaptively iteratively update the control parameters with the goal of minimizing the residual spurious signal amplitude.

[0124] The iterative module is used to re-perform coarse suppression and generate a synthetic output signal using updated control parameters until the residual spurious emissions meet the preset suppression requirements, at which point the iteration stops.

[0125] The initialization module includes:

[0126] The acquisition unit is used to acquire the number of DDS channels;

[0127] The first calculation unit is used to calculate the initial global phase offset based on the number of DDS channels;

[0128] The fine-tuning unit is used to fine-tune the initial global phase offset to obtain the global phase offset;

[0129] The setting unit is used to set the initial values ​​of the amplitude control parameters and phase control parameters of each DDS channel.

[0130] The coarse suppression module includes:

[0131] The second calculation unit is used to calculate the basic phase offset of each of the DDS channels using the global phase offset and the preset phase offset formula;

[0132] The third calculation unit is used to calculate the actual phase offset of each DDS channel through the basic phase offset and phase control parameters of each DDS channel;

[0133] An amplitude adjustment unit is used to perform amplitude weighted adjustment on the output signal of the corresponding DDS channel by using the amplitude control parameters of each DDS channel;

[0134] The phase adjustment unit is used to offset and adjust the spurious phase of the corresponding DDS channel at a predetermined spurious frequency point by means of the actual phase offset of each DDS channel;

[0135] The superposition unit is used to perform complex vector superposition of the output signals of all DDS channels after amplitude and phase control to obtain the synthesized output signal after coarse suppression.

[0136] The optimization module includes:

[0137] The extraction unit is used to perform frequency domain analysis on the target broadband frequency band of the synthesized output signal and extract key features of residual spurious signals, including the frequency, peak amplitude and phase of the residual spurious signals.

[0138] A unit is established to establish a spectral error function based on the peak amplitude with the aim of minimizing residual spurious amplitude;

[0139] The perturbation unit is used to randomly generate a limited-amplitude random phase perturbation and superimpose the random phase perturbation with the actual phase offset of each DDS channel;

[0140] The update unit is used to iteratively update the control parameters using the spectral error function and the DDS channel after superimposed perturbation.

[0141] It should be noted that the specific methods by which each module performs operations in the system described in the above embodiments have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0142] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0143] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An active spurious cancellation method based on the symmetry of multiple DDS structures, characterized in that, include: Construct at least two DDS channels with symmetrical structure; Set the global phase offset and initialize the control parameters, which include the amplitude control parameters and phase control parameters for each DDS channel; By using the global phase bias and the control parameters, the multiple DDS channels are subjected to structural spurious coherence cancellation to obtain a coarsely suppressed synthetic output signal. Residual spurious emissions are extracted based on the synthesized output signal, and the control parameters are adaptively iteratively updated with the goal of minimizing the residual spurious emissions amplitude. The coarse suppression is re-performed using the updated control parameters, and a synthetic output signal is generated. The iteration stops when the residual spurious signals meet the preset suppression requirements.

2. The active spurious cancellation method based on the symmetry of multiple DDS structures according to claim 1, characterized in that, The construction of at least two symmetrically structured DDS channels includes: Construct at least two DDS channels; This ensures that each DDS channel maintains structural symmetry in phase accumulation, table lookup, DAC, and sampling clock paths; The same FTW is input to all DDS channels, and the output spectrum of each DDS channel is acquired individually; The output spectrum is used to determine that the spurious frequency positions of each DDS channel at the predetermined spurious frequency point are completely consistent and the phase difference is stable; otherwise, the DDS channels are rebuilt.

3. The active spurious cancellation method based on the symmetry of multiple DDS structures according to claim 1, characterized in that, The process of setting the global phase offset and initializing the control parameters includes: Get the number of DDS channels; The initial global phase offset is calculated based on the number of DDS channels; The initial global phase offset is fine-tuned to obtain the global phase offset; Set the initial values ​​for the amplitude control parameters and phase control parameters for each DDS channel.

4. The active spurious cancellation method based on the symmetry of multiple DDS structures according to claim 1, characterized in that, The process of using the global phase bias and the control parameters to perform structural spurious coherence cancellation on multiple DDS channels to obtain a coarsely suppressed synthesized output signal includes: The basic phase offset of each DDS channel is calculated using the global phase offset and the preset phase offset formula. The actual phase offset of each DDS channel is calculated using the basic phase offset and phase control parameters of each DDS channel. The amplitude weighting adjustment of the output signal of the corresponding DDS channel is performed by using the amplitude control parameters of each DDS channel; By adjusting the actual phase offset of each DDS channel, the spurious phase of the corresponding DDS channel at the predetermined spurious frequency point is shifted and adjusted. The output signals of all DDS channels after amplitude and phase control are superimposed by complex vectors to obtain the synthesized output signal after coarse suppression.

5. The active spurious cancellation method based on the symmetry of multiple DDS structures according to claim 1, characterized in that, The step of extracting residual spurious signals based on the synthesized output signal and adaptively iteratively updating the control parameters with the goal of minimizing the residual spurious signal amplitude includes: Frequency domain analysis is performed on the target broadband frequency band of the synthesized output signal to extract key features of residual spurious signals. These key features include the frequency, peak amplitude, and phase of the residual spurious signals. With the aim of minimizing residual spurious amplitude, a spectral error function is established based on the peak amplitude; Random phase perturbations with limited amplitude are generated and superimposed with the actual phase offset of each DDS channel; The control parameters are iteratively updated using the spectral error function and the DDS channel after superimposed perturbation.

6. The active spurious cancellation method based on the symmetry of multiple DDS structures according to claim 5, characterized in that, The iterative update of the control parameters using the spectral error function and the DDS channel after superimposed perturbation includes: Based on the output spectrum of all DDS channels after superimposed perturbation, the updated residual spurious features are extracted. Substituting the updated residual spurious features into the spectral error function yields the global error function value; For each DDS channel, the partial derivative of the corresponding control parameter is calculated using the global error function value; The control parameters are updated using the partial derivatives according to the gradient descent method to obtain the updated control parameters for each DDS channel.

7. An active spurious cancellation system based on the structural symmetry of multiple DDS structures, characterized in that, include: Modules for building at least two symmetrical DDS channels; An initialization module is used to set the global phase offset and initialize control parameters, including amplitude control parameters and phase control parameters for each DDS channel. The coarse suppression module is used to perform structural spurious coherence cancellation on multiple DDS channels through the global phase bias and the control parameters to obtain a coarsely suppressed synthesized output signal. The optimization module is used to extract residual spurious signals based on the synthesized output signal and to adaptively iteratively update the control parameters with the goal of minimizing the residual spurious signal amplitude. The iterative module is used to re-perform coarse suppression and generate a synthetic output signal using updated control parameters until the residual spurious emissions meet the preset suppression requirements, at which point the iteration stops.

8. The active spurious cancellation system based on the symmetry of a multi-DDS structure according to claim 7, characterized in that, The initialization module includes: The acquisition unit is used to acquire the number of DDS channels; The first calculation unit is used to calculate the initial global phase offset based on the number of DDS channels; The fine-tuning unit is used to fine-tune the initial global phase offset to obtain the global phase offset; The setting unit is used to set the initial values ​​of the amplitude control parameters and phase control parameters of each DDS channel.

9. The active spurious cancellation system based on the symmetry of a multi-DDS structure according to claim 7, characterized in that, The coarse suppression module includes: The second calculation unit is used to calculate the basic phase offset of each of the DDS channels using the global phase offset and the preset phase offset formula; The third calculation unit is used to calculate the actual phase offset of each DDS channel through the basic phase offset and phase control parameters of each DDS channel; An amplitude adjustment unit is used to perform amplitude weighted adjustment on the output signal of the corresponding DDS channel by using the amplitude control parameters of each DDS channel; The phase adjustment unit is used to offset and adjust the spurious phase of the corresponding DDS channel at a predetermined spurious frequency point by means of the actual phase offset of each DDS channel; The superposition unit is used to perform complex vector superposition of the output signals of all DDS channels after amplitude and phase control to obtain the synthesized output signal after coarse suppression.

10. The active spurious cancellation system based on the symmetry of a multi-DDS structure according to claim 7, characterized in that, The optimization module includes: The extraction unit is used to perform frequency domain analysis on the target broadband frequency band of the synthesized output signal and extract key features of residual spurious signals, including the frequency, peak amplitude and phase of the residual spurious signals. A unit is established to establish a spectral error function based on the peak amplitude with the aim of minimizing residual spurious amplitude; The perturbation unit is used to randomly generate a limited-amplitude random phase perturbation and superimpose the random phase perturbation with the actual phase offset of each DDS channel; The update unit is used to iteratively update the control parameters using the spectral error function and the DDS channel after superimposed perturbation.

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