190 results about "Oversampling" patented technology

The invention provides a VCO digital circuit control method and system with temperature compensation, and relates to the technical field of circuit control, and the method comprises the steps: obtaining VCO output frequency and real-time temperature, and calculating an initial frequency deviation; correcting the frequency deviation based on the temperature compensation coefficient, and generating a temperature-frequency deviation characteristic curve; an optimal compensation factor is determined through Monte Carlo sampling; calculating a compensation parameter adaptive weight by using Bayesian iteration, and dynamically adjusting a compensation factor; and a control signal is generated through the digital integrator to realize frequency calibration. According to the invention, the high-precision frequency stability of the VCO under the temperature change condition is realized, and the circuit reliability is improved.

The invention relates to the technical field of digital playing equipment, and provides a lossless control method for the volume of a digital player and the digital player. The method comprises the following steps of: after receiving a target volume parameter, executing dynamic multiplying power oversampling and high-order noise shaping on an input digital audio signal, and injecting preset jitter to suppress in-band quantization distortion so as to generate an optimized digital audio stream; meanwhile, a high-resolution digital reference current control instruction corresponding to the target volume is independently generated, output of a reference current source is adjusted according to the high-resolution digital reference current control instruction, and a high-precision differential current signal is obtained by combining nonlinearity, temperature excursion and quantization errors of a closed-loop feedback compensation device through a multi-bit current segmentation network; performing bias stabilization processing on the signal, and converting the signal into a differential voltage signal for suppressing common-mode noise through a precision differential resistance network; and finally, low-distortion differential analog audio signals capable of directly driving a load are output through low-distortion gain, impedance conversion and power driving, so that low-distortion, high-signal-to-noise-ratio and wide-dynamic-range output in a full-volume range is realized.

The invention relates to the technical field of pulse acquisition, in particular to a high-speed ADC (Analog to Digital Converter) and FPGA (Field Programmable Gate Array) coordinated extremely-narrow pulse signal acquisition system, which comprises a phase identification monitoring module, a phase lock reference updating module, a sampling permission control module, a prohibition feedback identification module and a synchronous trigger adjustment module. According to the method, a beat tolerance judgment mechanism is introduced, hyper-bound phase deviation trend statistics and frequency vector extraction are combined, beat correction is carried out by utilizing a directional hopping cumulant and a period adjustment amount, a sampling permission judgment and keeping window alignment mechanism is introduced in a multi-frame period, and a two-way judgment means of a sampling starting trigger value is adopted, so that the beat tolerance of the multi-frame period is judged. And meanwhile, centralized extraction and frequency directivity statistics are carried out on the hopping direction in the sampling prohibition time sequence, the synchronous mismatch trend is distinguished, and the initial beat position is adjusted, so that the time domain characteristics of the narrow pulse waveform are kept continuous, the edge response is prevented from deviation, the trigger structure is stable and reliable, and the overall sampling judgment is more accurate and efficient.

The invention relates to the technical field of flow metering, in particular to an anti-flow-fluctuation metering method of a multichannel ultrasonic flowmeter. The method comprises the following steps: dividing the measurement of each sound channel into a plurality of measurement periods, calculating the weight proportion of each sound channel in the overall measurement based on a multi-factor weighting model, and introducing a real-time compensation mechanism of a fluid dynamic working condition to correct the weight proportion; when the fluid passes through the measuring pipe section, sound wave transmitting and receiving signals are sampled, the transmission time of sound waves in the fluid is calculated through sampled data, and the effective transmission time of each sound channel is recorded; and judging the effectiveness of sound channel sampling based on the sampled data and the effective transmission time of the sound channel, and establishing a multi-sound channel weighted average flow rate model. According to the invention, by introducing a multi-factor weighting model and a fluid dynamic working condition real-time compensation mechanism, the weight in the whole measurement can be dynamically adjusted according to the signal quality of each sound channel.

The invention provides a communication radiation source individual identification method based on time domain and time sequence coding constellation diagram feature fusion. The method is used for realizing stable identification of different transmitters under non-ideal conditions of carrier frequency offset, noise interference and the like. The method comprises the following steps: firstly, carrying out normalization and fixed-length interception on a received I / Q signal, and calculating an oversampling multiple according to a symbol rate and a time resolution; then, a time domain and time sequence coding constellation diagram double-branch feature extraction network is constructed, a time domain structure feature is extracted from a time domain branch by adopting a one-dimensional modified ResNet18, and a constellation diagram with time information is generated from a time sequence coding constellation diagram branch through a time sequence coding constellation module and the feature that the phase changes along with time is extracted; and carrying out joint modeling on the two types of features through a trainable weighted fusion mechanism. In the training stage, the performance of the model is improved by adopting cross entropy loss, an Adam optimizer, learning rate scheduling and an early stop strategy. In the reasoning process, input signals are classified by using the model weight with the highest verification accuracy, and a communication radiation source individual identification result is output. Experimental results show that the method can effectively enhance the frequency offset robustness and generalization ability of the model, realizes high-precision identification of the individual communication radiation source, and is suitable for the fields of security access of the Internet of Things, spectrum monitoring, electronic countermeasures and the like.

The invention relates to the technical field of broadband signal synthesis and high-speed digital-to-analog conversion, in particular to an oversampling-based real-time frequency interleaving digital-to-analog conversion system aliasing suppression method and system, and aims to solve the problem of spectrum aliasing caused by non-ideal characteristics of a digital sub-band decomposition filter and an analog filter under a real-time architecture of the system. In the invention, the sub-band decomposition is completed by adopting the linear phase complementary filter bank, so that distortion introduced by a transition band of a digital filter is avoided; by restraining system parameters such as passband and stopband frequencies and local oscillation frequency of a sub-band decomposition filter, a protection band is set by an oversampling mechanism, a frequency margin is reserved for a transition band of the filter, and aliasing components are suppressed. According to the method, extraction aliasing of a digital domain and mirror image aliasing of an analog domain are avoided at the same time from the system architecture, the frequency spectrum purity of output signals is improved, the method is suitable for a real-time system for processing continuous data streams, and technical support is provided for achieving a high-performance broadband signal source.

An electronic interface device is configured for use with associated optics for employing coded light for illuminating a liquid, gaseous, or other analyte or target, such as for measuring or determining a composition or other property of the analyte or target. The arrangement can help enable a far higher level of performance, such as for spectral analysis, imaging, or both. A shared common clock on both the illumination and receive sides of the system can be included, such as together with one or more of reference detection, per-channel wavelength-dependent modulation, multiple concurrent feedback loops at different levels, orthogonal and circulant codes, phase-scrambling to better utilize ADC dynamic range, oversampling, and other signal processing can be provided. Modulation codes can optionally employ a clock divider, such as which can be configured to satisfy one or more specified constraints.

The invention discloses an OFDM (Orthogonal Frequency Division Multiplexing) signal time-frequency collaborative equalization distortion suppression method, and belongs to the field of wireless communication. According to the invention, the problems of high complexity and poor transmission reliability of the existing short cyclic prefix method are solved. According to the invention, an OFDM system based on time domain oversampling and frequency domain interpolation equalization is adopted at a receiving end, and the oversampling algorithm can enhance the power of useful signals by properly broadening an equalization frequency band, so that the equalization effect is enhanced; according to the frequency domain interpolation equalization algorithm, weighted interpolation processing is carried out on frequency domain receiving signals, so that spectrum details can be better captured, and compensation and correction of an energy migration phenomenon generated by spectral lines in a frequency band due to a channel effect are realized. Through time-frequency cooperative processing at a receiving end, interference can be efficiently suppressed, stable and reliable demodulation precision and communication quality can be ensured, frequency spectrum resource loss caused by additional extension of a cyclic prefix can be avoided, and the frequency spectrum utilization efficiency of the system is further remarkably improved. The method can be applied to the field of wireless communication.

The invention discloses a loudspeaker detection system in a high-reliability demand environment, and relates to the technical field of loudspeaker detection, and the loudspeaker detection system is used for generating and outputting a preset level signal, and supporting the switching of a single-path manual detection mode, a multi-path manual detection mode, an automatic multi-path detection mode and an aging detection mode; output signals are collected in real time through a current sampling resistor connected to the output end of the loudspeaker in series, sound frequency and intensity parameters of the output signals are analyzed, and whether the loudspeaker function is normal or not is judged; wherein the frequency parameter is consistent with the output signal frequency of the driving board, and the intensity parameter is positively correlated with the output signal current; sampling results of multi-channel manual detection are received, cross interference data of multi-channel test units are collected at the same time through a sampling resistor, and a compatibility rating result is generated; and receiving data of automatic multi-path detection as a health index calculation benchmark, and evaluating a performance attenuation trend and residual life.

The invention relates to the technical field of radars, in particular to a weather radar distance resolution calibration method and system. The method comprises the following steps: collecting oversampling original baseband I / Q data of a point target in a plurality of continuous pulse periods; determining a pulse signal-to-noise ratio, and screening out effective pulses according to a threshold value; carrying out sub-sampling stage time alignment on the effective pulses based on cross-correlation analysis, and carrying out incoherent averaging on power module values of all the aligned pulses to generate an average pulse power envelope; converting the average pulse power envelope to a logarithm domain, and selecting discrete data points in a main lobe region; according to the discrete data points, a nonlinear least square method is adopted to carry out iterative fitting on the generalized Gaussian mathematical model, and a continuous analytic function describing the pulse envelope is obtained; according to the continuous analytic function, determining a pulse time width when the power is reduced to a peak value of-6dB; and determining the real distance resolution according to the pulse time width. The measurement robustness is improved, and sub-meter calibration precision is achieved.

The invention discloses a fault detection method for a flexible DC power transmission system and a related device, and the method employs a voltage gradient algorithm to detect whether the flexible DC power transmission system breaks down, and carries out the fault type discrimination based on the ground model voltage polarity through a sampled voltage signal when the system breaks down. And determining a high-frequency impedance difference value ratio of a rectification side and an inversion side in the flexible DC power transmission system based on the voltage signal and the sampled current signal, carrying out fault direction discrimination based on the high-frequency impedance difference value ratio, and finally determining a fault detection result according to a fault type and a fault direction. Therefore, the fault pole selection is realized based on the ground model voltage polarity, and the internal and external faults are accurately distinguished through the high-frequency impedance difference ratio, so that the reliability of fault detection of the flexible direct-current power transmission system is improved.

Using “in-situ on-die time-domain reflectometry (TDR)” with data signal paths of integrated circuits, printed circuit boards, and data processing equipment and systems allows testing, verification and troubleshooting of data channel signal path impedance variations including the package, escape routing, socket, board, and cable / connectors provides fast characterization thereof. Operation of “in-situ on-die TDR” uses existing analog-to-digital converter (ADC) and data transmitter (TX) drivers of an integrated circuit to act as a TDR sampling head by performing a user interface-based TDR sampling with a step-waveform generated by an integrated circuit TX driver. Then sampling the step-waveform with the ADC of the integrated circuit using spline interpolation to obtain the over-sampled waveform. Once the sampled step-waveform is obtained, the TDR profile of the sampled data channels may be calculated. Large amounts of impedance variation data may thus be collected during either integrated circuit manufacturer or customer-built data communications channel testing.

Methods, systems, and devices for a wakeup receiver operation is described. A receiver may include a conversion circuit that converts an RF signal to a baseband signal, where the baseband signal comprise a set of symbols received at a symbol rate. The receiver may include an analog-to-digital converter that converts the baseband signal to samples at a sample rate greater than the symbol rate. The receiver may include a set of correlators, each correlator of the set may receive a respective subset of the samples of the baseband signal and generate a respective output. The receiver may include a compare circuit that receives the respective outputs from the set of correlators and compares the respective outputs with a threshold, where the compare circuit also generates a wakeup command based at least in part on at least one output of the respective outputs satisfying the threshold.

This invention provides an adaptive AGC control circuit and method for broadband RF front-ends. The circuit includes: a gain tuning circuit connected to the RF link of the broadband RF front-end; and a signal detection circuit connected to the gain tuning circuit. The signal detection circuit is used to sample the RF signal in the RF link of the broadband RF front-end through an ADC, and to perform signal processing and gain control on the sampled RF signal based on an FPGA, thereby controlling the gain tuning circuit. This invention uses an FPGA+ADC hardware solution to achieve real-time detection and closed-loop fast control to realize adaptive AGC control of the broadband RF front-end, which has the following characteristics: 1. Simple circuit structure, clear logic, and easy implementation; 2. Real-time signal acquisition and processing with low state control delay; 3. High accuracy of dual-threshold signal detection and discrimination; 4. Flexible and controllable gain, and wide applicability.

The application provides a new hybrid nested noise shaping architecture suitable for noise shaping SAR ADC, which adopts a dynamic working closed-loop cascode FIA as a residual amplifier to reduce power consumption by eliminating the static current of the amplifier and removing the gain calibration circuit; the shaping architecture performs fourth-order noise shaping through the nested second-order CIFF and second-order EF noise shaping loops to achieve high precision in noise shaping at the same oversampling rate, and integrates the sampling noise cancellation (SNC) method to reduce the capacitance of the sampling capacitor to save chip area; the architecture adopts a closed-loop cascode FIA as a residual amplifier and CIFF and EF as noise shaping loops to solve the problem that the traditional noise shaping SAR ADC is difficult to simultaneously achieve high precision and low power consumption. In addition, the sampling KT / C noise cancellation (SNC) technology is integrated to reduce the capacitance of the sampling capacitor and save chip area.

The application discloses a kind of calibration method and device for rotary variation soft decoding, calibration method includes: according to N times oversampling frequency respectively sampling rotary variation feedback sine and cosine feedback signal envelope surface and obtaining positive, cosine oversampling signal;Positive, cosine oversampling signal is handled to obtain the zero position offset of rotary variation positive, cosine envelope signal;Positive, cosine oversampling signal is handled to obtain the amplitude of rotary variation positive, cosine envelope surface;Positive, cosine oversampling signal is handled to obtain the phase deviation of rotary variation positive, cosine envelope surface;Through the amplitude, zero position offset, phase deviation obtained by calculation, the envelope surface of rotary variation positive, cosine is compensated, and the signal after compensation is sent into phase-locked loop to obtain the angle and rotational speed information of rotary variation.The application obtains accurate amplitude, zero position offset, phase difference in turn, and then carries out error compensation, finally obtains corrected positive, cosine signal, effectively guarantees the efficiency of motor.

The invention relates to a ground-based radar super-resolution imaging method based on sparse reconstruction and local super-sampling. The ground-based radar super-resolution imaging method comprises the steps of ground-based radar signal modeling and data preprocessing; constructing a measurement model and sparse representation; sparse reconstruction of coarse grids; peak detection and local window selection; local oversampling and fine inversion are carried out; sub-pixel fitting and coordinate refining are carried out; carrying out continuous nuclear least square refining; and imaging fusion and result output are carried out, so that smooth transition among a plurality of overlapped regions is realized. According to the invention, high-precision reconstruction and detail enhancement of ground-based radar observation data are realized, the imaging quality and the target positioning precision can be effectively improved, and the method is suitable for various application scenes such as surface deformation monitoring, slope stability analysis and engineering structure safety detection.

The invention relates to the technical field of quantum information, in particular to a quantum random number generation method and system. The method comprises the following steps: sampling ASE noise analog electric signals at a rate greater than the bandwidth of a photoelectric detector and a rate less than the bandwidth of the photoelectric detector through a sampling oscilloscope to obtain two original random sequences; through a post-processing module, moving each element in each original random sequence rightwards according to a preset digit of the sequence; vacancies generated after right shifting are circularly complemented by starting elements on the left side of the sequence, and a target random sequence of the original random sequence is obtained; performing differential operation on each original random sequence and a target random sequence thereof, setting elements greater than 0 as 1, setting elements less than 0 as 0, rejecting elements equal to 0, and constructing a binary sequence of each original random sequence; and performing XOR operation on the binary sequence of each original random sequence to obtain a target quantum random number. According to the invention, the quantum random number generation cost is reduced, and the generation rate is improved.

This application provides a synchronous data acquisition card, which includes a conversion unit, a signal acquisition module, and a control chip. The control chip generates training instructions, and the conversion unit switches the data channel to the synchronous signal training channel according to the training instructions. Next, the control chip generates a first synchronous training signal and a second synchronous training signal with the same phase frequency. Then, the signal acquisition module samples the first synchronous training signal and the second synchronous training signal respectively through the synchronous signal training channel to obtain a first training sampled signal and a second training sampled signal. Finally, the control chip calibrates the signal acquisition module based on the first training sampled signal and the second training sampled signal, and synchronously samples through the sampling channel. The above scheme ensures that the data acquired simultaneously from different channels are synchronous data, reduces the lag relationship between data from different channels, and obtains the best state of data synchronization across different channels.

The invention relates to a multifunctional liquid level detection method, which comprises the following steps of: 1, sending an instruction and initializing an MCU (Microprogrammed Control Unit) through an upper computer, and determining a detection task and an initial parameter; step 2, on the basis of the initialization parameters in the step 1, a sampling needle is put into a test tube to scan a capacitance detection module, and the capacitance detection module captures a capacitance change signal after the sampling needle is in contact with the liquid level; the sampling needle is of a double-needle-tube structure comprising a sampling needle tube and a mixing needle tube; 3, on the basis of the capacitance change signal in the step 2, liquid level position judgment and sample size state judgment are completed through MCU algorithm processing; and step 4, based on a sample size judgment result in the step 3, respectively completing mixing or direct sampling operation through function division and hardware cooperation of the sampling needle tube and the mixing needle tube. The method has the advantages that the accuracy is greatly improved, the anti-interference capacity is high, and the operation process is simplified.

One or more examples refer to a procedure that includes: applying oversampling to data on a receive data path of a physical layer; generating a first signal indicating relationships between patterns shown by oversampled data portions and a predetermined pattern; generating a second signal indicating an observed feature of the first signal, the observed feature indicating a highest relationship between the patterns shown by respective oversampled data portions and the predetermined pattern; and providing the second signal to indicate the presence of a data portion corresponding to the predetermined pattern at a coupled portion of the receive data path of the physical layer.

The application provides a VCO digital circuit control method and system with temperature compensation, relates to the technical field of circuit control, and comprises the following steps: obtaining a VCO output frequency and real-time temperature, and calculating an initial frequency deviation; correcting the frequency deviation based on a temperature compensation coefficient, and generating a temperature-frequency deviation characteristic curve; determining an optimal compensation factor through Monte Carlo sampling; dynamically adjusting the compensation factor by using a Bayesian iteration to calculate a compensation parameter adaptive weight; and generating a control signal through a digital integrator to realize frequency calibration. The application realizes high-precision frequency stability of the VCO under the condition of temperature change, and improves circuit reliability.

The invention discloses a phase convergence method, circuit and chip for XGSPON uplink burst data transmission, and the method comprises the steps: obtaining first sampling data generated by a lead code of double oversampling burst data, recording even-number-bit data as a first even-number-bit sequence, and recording odd-number-bit data as a first odd-number-bit sequence; lagging the sampling clock phase of the burst data by a first preset angle; acquiring second sampling data generated by oversampling the preamble by two times of a sampling clock phase lagging behind the first preset angle, recording the even-number bit data as a second even-number bit sequence, and recording the odd-number bit data as a second odd-number bit sequence; performing preset logic processing on the first even bit sequence, the first odd bit sequence, the second even bit sequence and the second odd bit sequence, and determining a hopping edge position of the lead code according to a preset logic processing result; and adjusting the sampling clock phase of the burst data according to the jump edge position of the lead code. According to the invention, the time window of phase convergence is shortened, and the effective bandwidth of XGSPON uplink communication is improved.

This invention relates to the field of data encoding and compression technology, specifically to a lossless compression format for motion data used in artificial intelligence training, along with its encoding and decoding method and system. It includes the following steps: acquiring raw FIT data files collected by a motion device; parsing the message header and data body using a FIT parser to extract device information, motion session metadata, and time-series records containing timestamps, GPS coordinates, and multi-channel sensor data to generate a structured internal data object; establishing a HAD compression container and sequentially writing the file header and compression metadata area into the HAD compression container; and compressing the timestamps based on the structured internal data object using sampling interval detection. This invention significantly reduces structural redundancy in temporal, spatial, and multi-channel physiological parameters by introducing mechanisms such as timestamp frame encoding, GPS coordinate differential and run-length compression, and sensor data stationary segment detection and hybrid encoding.

The invention provides a method of performing magnetic resonance imaging on a body using a magnetic resonance imaging scanner, the method comprising applying to the body a time-varying magnetic field gradient (Gx, Gy, Gz) defining a continuous trajectory (ST) in k-space, the trajectory complying with a set of constraints comprising constraints on a maximum amplitude and a maximum slew rate of the time-varying magnetic field gradient, sampling points (KS) belonging to the trajectory define pseudo-random sampling of k-space approximate to a predetermined target sampling density, the trajectory in k-space minimizing a cost function under the set of constraints, the cost function being defined by a difference between a first term, referred to as an attraction term, and a second term, referred to as a rejection term, the first term promotes the distribution of sampling points in the k-space to follow a predetermined target sampling density, the second term promotes the separation of the sampling points in the k-space, and the exclusion term represents the sum of contributions corresponding to each pair of sampling points; wherein the trajectory (ST, MT) in the k-space defines a Cartesian sample of a central region (S) of the k-space.

The invention provides a phase-locked loop and electronic equipment, a reference clock signal and a feedback clock signal are respectively received through a first input end and a second input end of a sampling phase discrimination module, and an output end of the sampling phase discrimination module is coupled to an output node; the two input ends of the clock feed-forward offset module receive a reference feed-forward clock signal and a feedback feed-forward clock signal respectively, the output end of the clock feed-forward offset module is coupled to the output node, and the clock feed-forward offset module is used for outputting a reference disturbance compensation signal and a feedback disturbance compensation signal to the output node respectively, the reference disturbance compensation signal is configured to be opposite in phase and identical in amplitude with a disturbance component of the reference clock signal coupled to the output node, and the feedback feedforward clock signal is configured to be opposite in phase and identical in amplitude with a disturbance component of the feedback clock signal coupled to the output node. Thus, reference spurs at the output node of the phase-locked loop are suppressed.

The invention relates to the field of environment monitoring and analyzing instruments, and particularly discloses a portable radon detector which comprises a silicon photomultiplier sensor unit, a low-noise preamplifier unit, a comparator circuit and an STM32 main control module. By adopting the EQR-15 series silicon photomultiplier, the 300 [mu] m epoxy resin protective layer on the surface of the EQR-15 series silicon photomultiplier can directly emit light under the bombardment of alpha particles, the advantages of the integration of a photodiode and the high signal amplitude of a scintillator are integrated, and the detection sensitivity and the signal-to-noise ratio are remarkably improved while an independent scintillator is omitted. Aiming at weak current signals, a low-noise pre-amplification circuit with a TL084CDR operational amplifier as a core is designed, and a pulse shaping and emitter follower is arranged, so that the problems of signal amplification and interference resistance are effectively solved. The main control module realizes accurate capture and counting of alpha particle pulses through ADC sampling, hardware triggering and DMA storage in combination with a threshold self-adaption and baseline tracking algorithm.

The invention relates to the technical field of electrophysiological signal recording and stimulation of cerebral neurons, in particular to a distributed electrophysiological signal recording and stimulation system for cerebral neurons. The system comprises a recording path and a stimulation path, wherein the recording path is composed of an analog switch, a multi-stage cascade amplifier, a plurality of analog-to-digital converters, an FPGA main control board and a computer, and electrophysiological signals are collected and uploaded; the stimulation channel is composed of the computer, the FPGA main control board, a digital-to-analog converter and the analog switch and is used for issuing an electrical stimulation signal; wherein the amplifier, the converter and the power supply module are integrated on an independent PCB (Printed Circuit Board) and are connected with the FPGA main control board through an FMC (Frequency Management Controller) interface. The system configures the oversampling multiplying power of the analog-to-digital converter through the FPGA main control board so as to optimize the actual sampling rate and the signal-to-noise ratio. According to the invention, integration of acquisition and stimulation functions, hardware modularization and dynamic adjustment of signal quality are realized, and the flexibility and signal fidelity of the system are improved.

It is possible to reduce noise or power consumption when reading signals from pixels. [Solution] A photoelectric conversion device comprising: a photoelectric conversion unit that accumulates charge in response to incident light, a pixel that generates a photoelectric conversion signal in response to the accumulated charge and outputs the generated photoelectric conversion signal; a sample-and-hold unit that samples and holds a first photoelectric conversion signal and a second photoelectric conversion signal output from the pixel; and an oversampling type conversion unit that performs analog-to-digital (AD) conversion of the first photoelectric conversion signal and the second photoelectric conversion signal output from the sample-and-hold unit, characterized in that, in the processing from the generation of the first photoelectric conversion signal and the AD conversion of the first photoelectric conversion signal and the second photoelectric conversion signal, the gain set in response to the first photoelectric conversion signal and the gain set in response to the second photoelectric conversion signal are different.