A 1 / f noise suppression method for a particle detection system and related apparatus

Abstract

The application discloses a 1 / f noise suppression method for a particle detection system and a related device, and belongs to the field of photoelectric signal detection. The method comprises the following steps: acquiring a low-frequency voltage signal scattered by particles and a high-frequency carrier; mixing the low-frequency voltage signal based on the high-frequency carrier, shifting the frequency spectrum of the low-frequency voltage signal from low frequency to high frequency to suppress 1 / f noise, and then sequentially performing band-pass filtering and amplification to obtain a high-frequency voltage signal; and after sampling the high-frequency voltage signal through an analog-to-digital converter, mixing the high-frequency voltage signal with a first quadrature carrier generated by a local oscillator and performing low-pass filtering to synthesize a baseband signal. The application can suppress 1 / f noise and solve the problem of 1 / f noise reducing the signal-to-noise ratio of a micro-particle signal.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of photoelectric signal detection, and particularly relates to a 1 / f noise suppression method for a particle detection system and a related device. BACKGROUND

[0002] The principle of liquid particle detection is that there are particles of various diameters in the liquid. When the particles are irradiated by light, scattering occurs. A laser is used to irradiate one end of the liquid, and a photodiode is used to receive the other end. When particles exist, the light will be blocked, which will appear as a pulse signal on the receiving tube. The number and size of the particles are determined by analyzing the amplitude and number of the pulse signal. Liquid particle detection is mainly divided into oil particle detection and pure water particle detection. The application scenarios of oil particle detection include mechanical lubricating oil, aviation fuel and rocket fuel, etc. According to statistics, about 80% of mechanical failures are caused by poor lubrication or abrasive damage, and the accumulation of small particles in oil is one of the core reasons for causing equipment wear, corrosion and leakage. The cleanliness requirements of aerospace and semiconductor industries are extremely high. Micron-sized particles can cause precision components to fail. For example, particles larger than 0.1 mm in the fuel system of an aircraft engine can cause nozzle blockage, affecting thrust output. Pure water particle detection requires that the concentration of particles larger than 0.05 um in the water used to clean the semiconductor equipment according to ISO 14644-1 Class 1 standard be less than one billionth. Particles larger than 50 um remaining on the wafer surface can cause photolithography defects and etching abnormalities. Therefore, accurately measuring the number of particles in the liquid is of great significance to the safety of semiconductor equipment and aerospace.

[0003] The existing particle detection system is composed of a light source driving module, a photoelectric signal acquisition module, a filter signal amplification module and a digital processing module. Since the diameter of the liquid particles is very small, the voltage after photoelectric conversion is usually only a few mV or even a few uV, for example, in the range of 1 um to 10 um, and the voltage after photoelectric conversion and I / V conversion is about 10 uV to 10 mV. In the face of such a small signal, noise becomes a decisive factor limiting the measurement accuracy. The main sources of noise are thermal noise, 1 / f noise and shot noise. If the amplitude of the noise is greater than the particle signal, the measurement result will be disturbed, resulting in an overestimation of the number of particles.

[0004] Besides the signal-to-noise ratio (SNR), the most significant factor affecting measurement results is the signal-to-noise ratio (SNR). A low SNR leads to measurement errors. Traditional particle detection processes the signal as follows: photoelectric reception is converted into voltage, then filtered by a filtering circuit, directly amplified by an amplifier circuit, and finally processed by an ADC (analog-to-digital converter). For example, Chinese patent application CN118794850A discloses a particle detection processing circuit and method. It involves photoelectric reception of scattered light signals generated by laser irradiation of particles, converting the scattered light signals into current signals; an I / V conversion module converting the current signals into voltage signals; an operational amplifier module amplifying the voltage signals to obtain an amplified signal; a low-pass filter module filtering the amplified signal to obtain a filtered signal; a signal differential module extracting the AC component of the amplified signal to obtain a differential signal; and a signal processing module determining particle detection information data based on the filtered and differential signals. This patent achieves partial noise suppression through filtering and differential circuits. Chinese patent application CN214281340U captures an initial weak signal through a primary amplification stage, amplifies it initially, and then transmits it to a narrowband filter unit to filter out noise. The signal is then amplified again by a secondary amplification stage. While this patent suppresses some noise through the narrowband filter unit, it does not address the most significant 1 / f noise.

[0005] While the above method filters out some noise outside the bandwidth through filtering circuits, it doesn't address noise within the bandwidth itself. This results in a situation where, for large particle signals, the large voltage amplitude minimizes the impact of noise on detection, but for small particle signals, the voltage is inherently small, causing noise and signal to mix and become indistinguishable, thus affecting particle identification. Particle signals primarily occur between 1kHz and 100kHz, where noise is typically 1 / f noise, with a large amplitude at low frequencies that decreases as the frequency increases. Modulating the signal to a higher frequency range before amplification and filtering can effectively reduce noise and improve signal resolution. This is of great significance for the detection of tiny particles. Furthermore, practical testing has shown that particle signals typically have lower frequencies, between 1kHz and 100kHz, where 1 / f noise is the dominant noise factor. Therefore, noise reduction remains a technical challenge. Summary of the Invention

[0006] The purpose of this invention is to provide a 1 / f noise suppression method and related apparatus for particle detection systems, so as to solve the problem of 1 / f noise reducing the signal-to-noise ratio of small particle signals.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, a method for suppressing 1 / f noise in a particle detection system includes the following steps:

[0009] Acquire low-frequency voltage signals and high-frequency carrier waves scattered by particles;

[0010] The low-frequency voltage signal is mixed based on the high-frequency carrier, and the spectrum of the low-frequency voltage signal is shifted from low frequency to high frequency to suppress 1 / f noise. Then, bandpass filtering and amplification are performed in sequence to obtain a high-frequency voltage signal.

[0011] The high-frequency voltage signal is sampled by an analog-to-digital converter, mixed with a first orthogonal carrier generated by a local oscillator, and low-pass filtered to synthesize a baseband signal.

[0012] In some embodiments, the steps of mixing the low-frequency voltage signal based on the high-frequency carrier to shift the spectrum of the low-frequency voltage signal from low frequency to high frequency to suppress 1 / f noise, followed by bandpass filtering and amplification to obtain the high-frequency voltage signal, specifically include:

[0013] After multiplying the low-frequency voltage signal with a high-frequency carrier using a multiplier, the spectrum of the low-frequency voltage signal is shifted from low frequency to high frequency;

[0014] Then, after bandpass filtering and power amplification, a high-frequency voltage signal is obtained.

[0015] The product of the modulation index of the multiplier and the low-frequency voltage signal is less than 1.

[0016] In some embodiments, the steps of mixing the low-frequency voltage signal based on the high-frequency carrier to shift the spectrum of the low-frequency voltage signal from low frequency to high frequency to suppress 1 / f noise, followed by bandpass filtering and amplification to obtain the high-frequency voltage signal, specifically include:

[0017] The low-frequency voltage signal is split into I-channel and Q-channel signals, and the high-frequency carrier is a second orthogonal carrier.

[0018] The I-channel signal and Q-channel signal are mixed with the corresponding second orthogonal carrier, then synthesized by an adder, and then bandpass filtered and radio frequency amplified in sequence to obtain a high-frequency voltage signal.

[0019] In some embodiments, the step of acquiring the low-frequency voltage signal scattered by particles specifically includes: acquiring the light signal scattered by particles through a photodiode and converting it into a current signal; converting the current signal into a voltage signal through a transimpedance amplifier; and then low-pass filtering the voltage signal to obtain the low-frequency voltage signal.

[0020] In some implementations, the following steps are also included:

[0021] A preset detection threshold is used to sample the baseband signal and obtain the sampling point value;

[0022] If the current sampling point value is greater than the detection threshold, then continue to detect the next sampling point value until the current sampling point value is less than the detection threshold, then save the previous sampling point value as a valid peak value;

[0023] The effective peak value is converted into particle size to complete particle detection.

[0024] Secondly, a 1 / f noise suppression system for a particle detection system includes:

[0025] The data acquisition and generation module is used to acquire the low-frequency voltage signal scattered by particles, as well as the high-frequency carrier wave;

[0026] The 1 / f noise suppression module is used to mix the low-frequency voltage signal based on the high-frequency carrier, shift the spectrum of the low-frequency voltage signal from low frequency to high frequency to suppress 1 / f noise, and then perform bandpass filtering and amplification in sequence to obtain a high-frequency voltage signal;

[0027] The digital downconversion module is used to sample the high-frequency voltage signal through an analog-to-digital converter, and then mix and low-pass filter it with a first orthogonal carrier generated by a local oscillator to synthesize a baseband signal.

[0028] In some embodiments, the data acquisition and generation module includes: a photodetector, a transimpedance amplifier, a first low-pass filter, and a local oscillator;

[0029] The 1 / f noise suppression module includes an amplitude modulation module and an IQ modulation module. The amplitude modulation module includes a multiplier, a first bandpass filter, and a power amplifier. The IQ modulation module includes a passive RF splitter, a first mixer, an analog adder, a second bandpass filter, and an RF amplifier.

[0030] The digital downconversion module includes: a dual-channel synchronous analog-to-digital converter, a second mixer, a second low-pass filter, and a sum-of-squares synthesizer circuit;

[0031] A photodetector is used to collect light signals scattered by particles, convert them into current signals, and transmit them to a transimpedance amplifier.

[0032] A transimpedance amplifier is used to convert the current signal into a voltage signal and transmit it to a first low-pass filter;

[0033] A first low-pass filter is used to suppress high-frequency noise in the voltage signal, obtain a low-frequency voltage signal, and transmit it to a multiplier or a passive radio frequency splitter.

[0034] A local oscillator is used to generate a high-frequency carrier and transmit it to a multiplier or a first mixer, and at the same time to generate a first quadrature carrier and transmit it to a second mixer.

[0035] The multiplier is used to multiply the low-frequency voltage signal and the high-frequency carrier, and then pass them sequentially through the first bandpass filter and the power amplifier to obtain the high-frequency voltage signal, which is then transmitted to the first channel of the dual-channel synchronous analog-to-digital converter.

[0036] A passive radio frequency splitter is used to split the low-frequency voltage signal into an I-channel signal and a Q-channel signal, and transmit them to the first mixer;

[0037] The first mixer is used to mix the I-channel signal and the Q-channel signal with the corresponding high-frequency carrier respectively to obtain the I-channel mixed signal and the Q-channel mixed signal, and transmit them to the analog adder. The high-frequency carrier in the first mixer is the second quadrature carrier.

[0038] An analog adder is used to add the I-channel mixing signal and the Q-channel mixing signal together, synthesize them, and then pass them sequentially through a second bandpass filter and an RF amplifier to obtain a high-frequency voltage signal, which is then transmitted to the second channel of the dual-channel synchronous analog-to-digital converter.

[0039] A dual-channel synchronous analog-to-digital converter is used to sample the high-frequency voltage signal of the first channel or the second channel and then transmit it to the second mixer;

[0040] The second mixer is used to mix the sampled high-frequency voltage signal with the first quadrature carrier, and then pass it through the second low-pass filter and the sum-of-squares synthesis circuit to obtain the baseband signal.

[0041] Thirdly, an electronic device includes a memory, a processor, and a computer program stored in the memory and executable in the processor, wherein the processor, when executing the computer program, implements the steps of the 1 / f noise suppression method for a particle detection system.

[0042] Fourthly, a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the 1 / f noise suppression method for a particle detection system.

[0043] Fifthly, a computer program product comprising a computer program that, when executed by a processor, implements the steps of the 1 / f noise suppression method for a particle detection system.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] This invention mixes low-frequency voltage signals with high-frequency carrier waves, shifting the spectrum of the low-frequency voltage signals from low to high frequencies. This avoids the situation where small particle signals are easily submerged by 1 / f noise in the low-frequency band. Combined with bandpass filtering and amplification, it can effectively filter out out-of-band noise and improve the signal-to-noise ratio.

[0046] Furthermore, signal modulation is achieved through a multiplier, and the product of the modulation index and the low-frequency voltage signal is controlled to be less than 1, ensuring that linear modulation avoids signal distortion. Compared with the traditional method of directly performing bandpass filtering and power amplification, thermal noise coupling can be reduced. At the same time, the bandpass filter can accurately intercept the signal frequency band and suppress adjacent channel interference.

[0047] Furthermore, by using IQ modulation technology to divide the low-frequency voltage signal into I-channel and Q-channel signals, and then mixing them with the second quadrature carrier to synthesize them, a high-frequency voltage signal is obtained. This can eliminate image interference in single-channel modulation, while IQ modulation technology can preserve the complete phase information of the signal.

[0048] Furthermore, if the current sampling point value is greater than the detection threshold, the next sampling point value is detected until the current sampling point value is less than the detection threshold. Then, the previous sampling point value is saved as the effective peak value, and the effective peak value is converted into particle size. This method can track the signal peak value in real time and avoid missed detections or false detections caused by traditional fixed thresholds. Attached Figure Description

[0049] Figure 1 A detailed flowchart of a 1 / f noise suppression method for a particle detection system provided by the present invention;

[0050] Figure 2 This is a simulation schematic diagram of a transimpedance amplifier circuit provided in an embodiment of the present invention;

[0051] Figure 3 The simulation results of the transimpedance amplifier provided in the embodiment of the present invention are shown in the figure.

[0052] Figure 4 The simulation schematic diagram of the SK-type second-order low-pass filter provided in the embodiment of the present invention;

[0053] Figure 5 The amplitude-frequency response curve of the SK-type second-order low-pass filter provided in the embodiment of the present invention;

[0054] Figure 6 A flowchart of a 1 / f noise suppression method for a particle detection system provided in an embodiment of the present invention;

[0055] Figure 7 This is a structural diagram of a 1 / f noise suppression system for a particle detection system provided in an embodiment of the present invention. Detailed Implementation

[0056] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings. The content described herein is for explanation rather than limitation of the present invention.

[0057] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of this invention are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, systems, products, or devices.

[0058] Example 1

[0059] like Figure 1 and Figure 6 As shown, this embodiment provides a 1 / f noise suppression method for a particle detection system, including the following steps:

[0060] S1, acquire the low-frequency voltage signal and high-frequency carrier wave scattered by the particles;

[0061] S1.1, the photodiode converts the particle-scattered light signal into a current signal. Specifically, it is done through the following formula:

[0062]

[0063] in, Photoresponsivity (unit: A / W) Optical power (in watts). For example, the photodiode S1223. =0.5A / W, typical output current =10nA (corresponding to 1µm particles);

[0064] S1.2, the operational amplifier is the core component of the transimpedance amplifier, which converts the current signal into voltage. Converted to voltage signal Specifically, it is done through the following formula:

[0065]

[0066] in, This is the resistance between the output terminal and the inverting input terminal of the operational amplifier.

[0067] Transimpedance amplifiers should be selected with low bias current and low noise to preserve signal integrity. For example, the ADA4522 has a bias current of 50pA. Since the bandwidth of a chip is typically below 100kHz, a bandwidth of 100kHz should be selected to suppress high-frequency noise. Figure 2 The principle of a transimpedance amplifier was demonstrated. Figure 2 In the diagram, VCC represents +12V power supply, and VEE represents -12V power supply, used to power the operational amplifier. Current source I1 is a photodiode circuit model, set to 1mA DC bias, 10uA AC current, and 1kHz frequency, simulating the AC signal from particles. R1 is the feedback resistor of the transimpedance amplifier, and C1 is the feedback capacitor, which, together with the feedback resistor R1, acts as a filter. OUT1 is the output voltage. This transimpedance amplifier amplifies the 1mA current to a 6.2V DC voltage. The current source in the diagram is a photodiode model. The capacitor acts as a filter. Figure 3 For simulation results, I1 is the input current of the current source. V(out) is the output voltage. This transimpedance amplifier can amplify the current signal into a voltage signal of about 6.2V.

[0068] S1.3, use a filter to suppress high-frequency noise. For example, a second-order Butterworth filter can be used, whose transfer function is:

[0069]

[0070] With a reference cutoff frequency of 100kHz and a roll-off rate of -40dB / dec, this filter is used to filter voltage signals. Low-pass filtering is performed to obtain a low-frequency voltage signal. , The cutoff frequency is the angular frequency corresponding to -3dB. Let s be the Laplace complex frequency variable, s = σ + jω, where σ is the real part of the complex variable, representing the signal attenuation constant, ω is the imaginary part of the complex variable, representing the angular frequency of the signal, and j represents the imaginary unit.

[0071] Figure 4 This demonstrates an SK-type second-order low-pass filter. Resistors R2 and R3, capacitors C2 and C3, and operational amplifier U2 constitute the SK-type second-order low-pass filter. It can filter out high-frequency noise signals. The input signal is an AC current signal I1, and the output signal OUT1 is the filter's output voltage. Its cutoff frequency is 100kHz, and its roll-off rate is -40dB / dec. Figure 5The amplitude-frequency response curve is shown. The solid black line represents the gain curve of this SK-type second-order low-pass filter, indicating the gain of the output voltage with respect to the current. This SK-type second-order low-pass filter has a gain of 76dB within 50kHz, and then decreases at a rate of 20dB / dec. The dashed line is the phase curve, representing the phase difference between the output voltage and the input current.

[0072] S1 also includes generating a high-frequency carrier through a local oscillator. Since S2 has two paths, amplitude modulation and IQ modulation, the high-frequency carrier obtained in S1 will be specifically explained in S2 in combination with different paths.

[0073] S2, the low-frequency voltage signal is mixed based on the high-frequency carrier to shift the spectrum of the low-frequency voltage signal from low frequency to high frequency to suppress 1 / f noise, and then bandpass filtering and amplification are performed in sequence to obtain a high-frequency voltage signal;

[0074] S2.1, Amplitude Modulation (AM)

[0075] S2.1.1, generates a high-frequency carrier wave through a local oscillator. Specifically, a high-frequency carrier is generated through the DDS AD9854. ;

[0076]

[0077] High-frequency carrier carrier frequency =1MHz, carrier amplitude =5Vpp, where Vpp is the peak-to-peak voltage of the high-frequency carrier wave. For time, it describes the pattern of how the carrier signal changes over time.

[0078] S2.1.2, use a multiplier for mixing to convert the high-frequency carrier... and low-frequency voltage signals Perform multiplication to achieve Spectrum From low frequency ( ) to high frequency ( The relocation is carried out using the following method:

[0079]

[0080] in, It is a high-frequency voltage signal. The modulation index, , This is the minimum frequency of the particle, typically 10kHz;

[0081] low frequency voltage signal The original signal, its spectrum Concentrated between 1kHz and 100kHz;

[0082] High frequency voltage signal The spectrum is given by the following formula:

[0083]

[0084] in, The spectrum before mixing. For the independent variable, frequency, The unit impact function.

[0085] Key parameter calculation:

[0086] (1) Modulation index The determination

[0087] Assuming a low-frequency voltage signal Maximum input signal amplitude To avoid over-amplitude modulation (i.e. Therefore, the modulation index The following formula must be satisfied:

[0088]

[0089] Modulation index The typical value is Leave a 20% margin. It is the peak-to-peak value of the modulated voltage, which is the maximum voltage minus the minimum voltage.

[0090] (2) High-frequency carrier carrier power and sideband power Relationship

[0091] Let the carrier amplitude Then the carrier power :

[0092]

[0093] Sideband power (double-sideband):

[0094]

[0095] in , This is the root mean square value of the input voltage.

[0096] The hardware implementation steps of S2.1.2 are as follows:

[0097] (1) Signal input and conditioning: Input impedance matching: The signal source output by the photodiode in modulation S1 needs to be matched with the input impedance of the multiplier, which is 50Ω;

[0098] (2) Multiplier configuration: Use an analog multiplier AD8346 or a digital multiplier DSP (Digital Signal Processor) + FPGA (Field-Programmable Gate Array).

[0099] (3) Injection of high-frequency carrier signal: The 1MHz carrier signal output from the DDS AD9854 is connected to the carrier input terminal (RF port) of the multiplier. The amplitude of the high-frequency carrier signal is matched with the linear operating region of the multiplier. The analog multiplier AD8346 requires V RF <1Vpp, V RF The voltage amplitude of the carrier signal input to the multiplier.

[0100] S2.1.3, a SAW filter (Surface Acoustic Wave Filter) is used for high-frequency voltage signals. Perform bandpass filtering;

[0101] SAW filter retains sidebands:

[0102] )

[0103] Among them, the center frequency =1MHz, bandwidth B=50kHz, out-of-band rejection >50dB Let be the frequency response function of the bandpass filter, which describes the frequency selectivity of the bandpass filter. This is a rectangular function used to describe the passband range of an ideal bandpass filter in the frequency domain. The formula represents the frequency f relative to the center frequency. After normalization (divided by bandwidth B), it falls within [ -B / 2, Frequency components within the +B / 2] interval are preserved, while frequency components outside the interval are suppressed.

[0104] S2.1.4, the signal after bandpass filtering in S2.1.3 is amplified by a power amplifier, specifically by the following formula:

[0105]

[0106] in, High-frequency voltage signal Amplified power, For the gain of the power amplifier, High-frequency voltage signal Power before amplification =30dB, .

[0107] S2.2, IQ modulation

[0108] S2.2.1, the low-frequency voltage signal is split using a passive RF splitter (model Mini-Circuits ZFSC-2-5+). It is divided into two paths. The I path directly transmits the original signal, while the Q path passes through the 90° phase shifter ADI HMC198 to finally obtain the I path signal and the Q path signal.

[0109] I-channel signal:

[0110] Q signal:

[0111] in, This represents the phase value of the modulated signal.

[0112] S2.2.2 The I-channel signal and Q-channel signal are mixed with the second quadrature carrier by the first mixer. The first mixer is a dual-balanced mixer, Mini-Circuits ZX05-2L+.

[0113] The generation of the second quadrature carrier typically employs two methods: a DDS (Direct Digital Synthesizer) chip and a PLL (Phase-Locked Loop) + VCO (Voltage-Controlled Oscillator). This embodiment uses a DDS AD9854 to generate the second quadrature carrier. and ,in It is 1MHz.

[0114]

[0115] in, This is a mixing signal for channel I. This is the Q-channel mixing signal.

[0116] Low-frequency voltage signal in this step All inputs are sent to the RF port of the first mixer, and the second quadrature carrier is sent to the LO port of the first mixer; the LO port and the RF port are isolated by a balun to suppress local oscillator signal leakage (typical value >50 dBc).

[0117] S2.2.3, the I-channel mixer signal and the Q-channel mixer signal are added together using an analog adder to generate a composite signal. The analog adder uses the AD8052 operational amplifier, which has a bandwidth of 100MHz and a gain-bandwidth product of 1.6GHz;

[0118]

[0119] Its resistor network is configured as an inverting adder circuit to achieve signal superposition, such as Figure 5 and Figure 6 Simulation results of the inverting adder circuit are shown. Green and blue represent the I and Q signals, and red represents the summed signal. The formula in the resistor network is:

[0120]

[0121] S2.2.4 For composite signals Bandpass filtering and RF amplification are performed. The bandpass filtering steps are the same as in S2.1.3. The RF amplification uses an RF amplifier with a gain of 30dB.

[0122] S3, the high-frequency voltage signal is sampled by an analog-to-digital converter, and then mixed and low-pass filtered with a first orthogonal carrier generated by a local oscillator to synthesize a baseband signal.

[0123] S3.1, using a dual-channel synchronous analog-to-digital converter (ADC) to process the results obtained in S2.1 and S2.2. and Sampling was performed Signals and Signal:

[0124]

[0125]

[0126] The ADC has a resolution of 16 bits and a sampling rate of .

[0127] S3.2, Digital Down-Conversion

[0128] First, a first quadrature carrier is generated using a local oscillator, specifically the DDS AD9854.

[0129] (1) To Demodulate the signal:

[0130]

[0131] right and The baseband signal is obtained by low-pass filtering and synthesis. :

[0132]

[0133] (2) To Demodulate the signal:

[0134]

[0135] right and The baseband signal is obtained by low-pass filtering and synthesis. :

[0136]

[0137] S4, Peak Detection

[0138] The preset detection threshold is 10mV, and the baseband signal obtained in S3 is... or baseband signal Sampling is performed to obtain the sampling point values.

[0139] If the current sampling point value is greater than the detection threshold, then continue to detect the next sampling point value until the current sampling point value is less than the detection threshold, then save the previous sampling point value as a valid peak value;

[0140] The effective peak value is used to calculate the particle size using an amplitude-to-particle-size conversion formula, thus completing particle detection. The specific formula is as follows:

[0141]

[0142] in This is the instrument constant (determined by calibration). Background light intensity, The intensity of the diffracted light is related to the particle radius distribution. For the scattering angle, λ is the wavelength of the incident light.

[0143]

[0144] in, For the effective peak value, It is a low-pass filter. for or .

[0145] The above embodiment modulates the particle electrical signal from a low-frequency band to a high-frequency band, thereby greatly reducing the influence of 1 / f noise. The signal conditioning part includes signal amplification and bandpass filtering. The amplification amplitude must be controlled to fully analyze the particle size of the detected particles, while also considering the ADC input voltage range. For example, when measuring particles from 1µm to 100µm, the voltage corresponds to 1mV to 100mV, and the ADC input voltage is 0 to 5V. Therefore, the amplification factor cannot exceed 50 times, otherwise large particles will not be measured. At the same time, it cannot be too small, making it difficult to distinguish the particle size of small particles. The bandpass filter must consider the bandwidth after signal modulation. Designing a bandpass filter with a center frequency of intermediate frequency and a bandwidth equal to the signal frequency yields the best results. By multiplying the sampled signal with a local carrier of the same frequency and phase, and then low-pass filtering, the I(n) and Q(n) signals are recovered. According to A(n) = The formula calculates the signal amplitude to accurately determine particle size, establishing an effective data processing link from the raw optical signal to particle size determination. After extracting the raw signal, peak values ​​are extracted. The algorithm starts detection when the signal amplitude exceeds a threshold. If subsequent voltage values ​​are higher than the previous value, detection continues until a subsequent voltage value is lower than the previous value, at which point the voltage is saved as the peak value. The particle size is then calculated based on the relationship between voltage and particle size.

[0146] Therefore, this embodiment has the following advantages: (1) It innovatively uses IQ modulation technology to successfully overcome the problem of low-frequency noise interference in small signal testing in traditional particle detection schemes, and greatly improves the test accuracy. In the past detection schemes, after the photodiode converts the light signal into current, it is converted into a voltage signal by a transimpedance amplifier, and then directly filtered and amplified before entering the ADC. However, since the entire process is processed in the low-frequency band, 1 / f noise seriously interferes with the small signal, resulting in a large error in the test results. This invention optimizes the signal processing flow. After the light signal is converted into an electrical signal by the photoelectric conversion module, it directly enters the spectrum shift, thereby avoiding the noise interference in the measurement results caused by direct amplification in the previous method. Amplification and filtering at high frequency can suppress out-of-band noise to the greatest extent.

[0147] (2) Directly using digital demodulation to determine particle size, while some previous methods used comparators, this approach only allowed for pre-setting voltages for several channels to determine the particle size range (e.g., 10µm to 20µm), and could not flexibly determine the specific size of the particles. Digital demodulation, on the other hand, can almost completely preserve particle size information. By analyzing the relationship between voltage and particle size, the particle size can be accurately determined, offering greater flexibility and accuracy.

[0148] (3) The peak detection algorithm can accurately find the voltage value corresponding to each particle. Combined with the particle size determination formula, the particle size can be accurately calculated, and the resolution is further improved.

[0149] Example 2

[0150] like Figure 7 As shown, this embodiment provides a 1 / f noise suppression system for a particle detection system, comprising:

[0151] The data acquisition and generation module is used to acquire the low-frequency voltage signal scattered by particles, as well as the high-frequency carrier wave;

[0152] The 1 / f noise suppression module is used to mix the low-frequency voltage signal based on the high-frequency carrier, shift the spectrum of the low-frequency voltage signal from low frequency to high frequency to suppress 1 / f noise, and then perform bandpass filtering and amplification in sequence to obtain a high-frequency voltage signal;

[0153] The digital downconversion module is used to sample the high-frequency voltage signal through an analog-to-digital converter, and then mix and low-pass filter it with a first orthogonal carrier generated by a local oscillator to synthesize a baseband signal.

[0154] The data acquisition and generation module includes: a photodetector, a transimpedance amplifier, a first low-pass filter, and a local oscillator;

[0155] The 1 / f noise suppression module includes an amplitude modulation module and an IQ modulation module. The amplitude modulation module includes a multiplier, a first bandpass filter, and a power amplifier. The IQ modulation module includes a passive RF splitter, a first mixer, an analog adder, a second bandpass filter, and an RF amplifier.

[0156] The digital downconversion module includes: a dual-channel synchronous analog-to-digital converter, a second mixer, a second low-pass filter, and a sum-of-squares synthesizer circuit;

[0157] A photodetector is used to collect light signals scattered by particles, convert them into current signals, and transmit them to a transimpedance amplifier.

[0158] A transimpedance amplifier is used to convert the current signal into a voltage signal and transmit it to a first low-pass filter;

[0159] A first low-pass filter is used to suppress high-frequency noise in the voltage signal, obtain a low-frequency voltage signal, and transmit it to a multiplier or a passive radio frequency splitter.

[0160] A local oscillator is used to generate a high-frequency carrier and transmit it to a multiplier or a first mixer, and at the same time to generate a first quadrature carrier and transmit it to a second mixer.

[0161] The multiplier is used to multiply the low-frequency voltage signal and the high-frequency carrier, and then pass them sequentially through the first bandpass filter and the power amplifier to obtain the high-frequency voltage signal, which is then transmitted to the first channel of the dual-channel synchronous analog-to-digital converter.

[0162] A passive radio frequency splitter is used to split the low-frequency voltage signal into an I-channel signal and a Q-channel signal, and transmit them to the first mixer;

[0163] The first mixer is used to mix the I-channel signal and the Q-channel signal with the corresponding high-frequency carrier respectively to obtain the I-channel mixed signal and the Q-channel mixed signal, and transmit them to the analog adder. The high-frequency carrier in the first mixer is the second quadrature carrier.

[0164] An analog adder is used to add the I-channel mixing signal and the Q-channel mixing signal together, synthesize them, and then pass them sequentially through a second bandpass filter and an RF amplifier to obtain a high-frequency voltage signal, which is then transmitted to the second channel of the dual-channel synchronous analog-to-digital converter.

[0165] A dual-channel synchronous analog-to-digital converter is used to sample the high-frequency voltage signal of the first channel or the second channel and then transmit it to the second mixer;

[0166] The second mixer is used to mix the sampled high-frequency voltage signal with the first quadrature carrier, and then pass it through the second low-pass filter and the sum-of-squares synthesis circuit to obtain the baseband signal.

[0167] The module division in this embodiment of the invention is illustrative and represents only one logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional modules in the various embodiments of the invention can be integrated into a single processor, exist as separate physical entities, or be integrated into a single module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0168] This embodiment also provides a computer device, which includes a processor and a memory. The memory is used to store a computer program (in this embodiment, the computer program includes a computing component and an iterative component, capable of model calculation and model updating). The computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to realize the corresponding method flow or corresponding function. The processor described in this embodiment can be used for the operation of a 1 / f noise suppression method for a particle detection system.

[0169] This embodiment also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the 1 / f noise suppression method for a particle detection system in the above embodiment.

[0170] This embodiment also provides a computer program product, which includes a computer program that, when executed by a processor, implements the corresponding steps of a 1 / f noise suppression method for a particle detection system described in the above embodiment.

[0171] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0172] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (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, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0173] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function 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 function specified in one or more boxes.

[0174] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable 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.

[0175] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A 1 / f noise suppression system for a particle detection system, characterized in that, include: The data acquisition and generation module is used to acquire the low-frequency voltage signal and high-frequency carrier wave scattered by the particles; The 1 / f noise suppression module is used to mix the low-frequency voltage signal based on the high-frequency carrier, shift the spectrum of the low-frequency voltage signal from low frequency to high frequency to suppress 1 / f noise, and then perform bandpass filtering and amplification in sequence to obtain a high-frequency voltage signal; The digital downconversion module is used to sample the high-frequency voltage signal through an analog-to-digital converter, and then mix and low-pass filter it with a first quadrature carrier generated by a local oscillator to synthesize a baseband signal. The data acquisition and generation module includes: a photodetector, a transimpedance amplifier, a first low-pass filter, and a local oscillator; The 1 / f noise suppression module includes an amplitude modulation module and an IQ modulation module. The amplitude modulation module includes a multiplier, a first bandpass filter, and a power amplifier. The IQ modulation module includes a passive RF splitter, a first mixer, an analog adder, a second bandpass filter, and an RF amplifier. The digital downconversion module includes: a dual-channel synchronous analog-to-digital converter, a second mixer, a second low-pass filter, and a sum-of-squares synthesizer circuit; A photodetector is used to collect light signals scattered by particles, convert them into current signals, and transmit them to a transimpedance amplifier. A transimpedance amplifier is used to convert the current signal into a voltage signal and transmit it to a first low-pass filter; A first low-pass filter is used to suppress high-frequency noise in the voltage signal, obtain a low-frequency voltage signal, and transmit it to the multiplier or passive radio frequency splitter. A local oscillator is used to generate a high-frequency carrier and transmit it to a multiplier or a first mixer, and at the same time to generate a first quadrature carrier and transmit it to a second mixer. The multiplier is used to multiply the low-frequency voltage signal and the high-frequency carrier, and then pass them sequentially through the first bandpass filter and the power amplifier to obtain the high-frequency voltage signal, which is then transmitted to the first channel of the dual-channel synchronous analog-to-digital converter. A passive radio frequency splitter is used to split the low-frequency voltage signal into an I-channel signal and a Q-channel signal, and transmit them to the first mixer; The first mixer is used to mix the I-channel signal and the Q-channel signal with the corresponding high-frequency carrier respectively to obtain the I-channel mixed signal and the Q-channel mixed signal, and transmit them to the analog adder. The high-frequency carrier in the first mixer is the second quadrature carrier. An analog adder is used to add the I-channel mixing signal and the Q-channel mixing signal together, synthesize them, and then pass them sequentially through a second bandpass filter and an RF amplifier to obtain a high-frequency voltage signal, which is then transmitted to the second channel of the dual-channel synchronous analog-to-digital converter. A dual-channel synchronous analog-to-digital converter is used to sample the high-frequency voltage signal of the first channel or the second channel and then transmit it to the second mixer; The second mixer is used to mix the sampled high-frequency voltage signal with the first quadrature carrier, and then pass it through the second low-pass filter and the sum-of-squares synthesis circuit to obtain the baseband signal.

2. A method for suppressing 1 / f noise in a particle detection system, characterized in that, A 1 / f noise suppression system for a particle detection system as described in claim 1, comprising the following steps: Acquire low-frequency voltage signals and high-frequency carrier waves scattered by particles; The low-frequency voltage signal is mixed based on the high-frequency carrier, and the spectrum of the low-frequency voltage signal is shifted from low frequency to high frequency to suppress 1 / f noise. Then, bandpass filtering and amplification are performed in sequence to obtain a high-frequency voltage signal. The high-frequency voltage signal is sampled by an analog-to-digital converter, mixed with a first orthogonal carrier generated by a local oscillator, and low-pass filtered to synthesize a baseband signal.

3. The 1 / f noise suppression method for a particle detection system according to claim 2, characterized in that, The steps of mixing the low-frequency voltage signal based on the high-frequency carrier, shifting the spectrum of the low-frequency voltage signal from low frequency to high frequency to suppress 1 / f noise, and then sequentially performing bandpass filtering and amplification to obtain the high-frequency voltage signal specifically include: After multiplying the low-frequency voltage signal with a high-frequency carrier using a multiplier, the spectrum of the low-frequency voltage signal is shifted from low frequency to high frequency; Then, after bandpass filtering and power amplification, a high-frequency voltage signal is obtained. The product of the modulation index of the multiplier and the low-frequency voltage signal is less than 1.

4. The 1 / f noise suppression method for a particle detection system according to claim 2, characterized in that, The steps of mixing the low-frequency voltage signal based on the high-frequency carrier, shifting the spectrum of the low-frequency voltage signal from low frequency to high frequency to suppress 1 / f noise, and then sequentially performing bandpass filtering and amplification to obtain the high-frequency voltage signal specifically include: The low-frequency voltage signal is split into I-channel and Q-channel signals, and the high-frequency carrier is a second orthogonal carrier. The I-channel signal and Q-channel signal are mixed with the corresponding second orthogonal carrier, then synthesized by an adder, and then bandpass filtered and radio frequency amplified in sequence to obtain a high-frequency voltage signal.

5. The 1 / f noise suppression method for a particle detection system according to claim 2, characterized in that, The step of obtaining the low-frequency voltage signal scattered by the particles specifically includes: collecting the light signal scattered by the particles through a photodiode and converting it into a current signal; converting the current signal into a voltage signal through a transimpedance amplifier; and then low-pass filtering the voltage signal to obtain the low-frequency voltage signal.

6. The 1 / f noise suppression method for a particle detection system according to claim 2, characterized in that, It also includes the following steps: A preset detection threshold is used to sample the baseband signal and obtain the sampling point value; If the current sampling point value is greater than the detection threshold, then continue to detect the next sampling point value until the current sampling point value is less than the detection threshold, then save the previous sampling point value as a valid peak value; The effective peak value is converted into particle size to complete particle detection.

7. An electronic device, characterized in that, The system includes a memory, a processor, and a computer program stored in the memory and executable in the processor, wherein the processor, when executing the computer program, implements the steps of the 1 / f noise suppression method for a particle detection system as described in any one of claims 2 to 6.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the 1 / f noise suppression method for a particle detection system as described in any one of claims 2 to 6.

9. A computer program product, the computer program product comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the 1 / f noise suppression method for a particle detection system as described in any one of claims 2 to 6.

Images