405 results about "Frequency discrimination" patented technology

A surgical technique for removing corneal tissue with scanned infrared radiation is disclosed which utilizes short mid-infrared laser pulses to provide a tissue removal mechanism based on photospallation. Photospallation is a photomechanical ablation mechanism which results from the absorption of incident radiation by the corneal tissue. Since photospallation is a mechanical ablation process, very little heat is generated in the unablated adjacent tissue. The disclosed surgical system includes a scanning beam delivery system which allows uniform irradiation of the treatment region and utilizes low energy outputs to achieve controlled tissue removal. A real-time servo-controlled dynamic eye tracker, based on a multiple-detector arrangement, is also disclosed which senses the motion of the eye and provides signals that are proportional to the errors in the lateral alignment of the eye relative to the axis of the laser beam. Temporal and frequency discrimination are preferably utilized to distinguish the tracking illumination from the ambient illumination and the surgical laser beam. A laser parametric generator for surgical applications is disclosed which utilizes short-pulse, mid-infrared radiation. The mid-infrared radiation may be produced by a pump laser source, such as a neodymium-doped laser, which is parametrically down converted in a suitable nonlinear crystal to the desired mid-infrared range. The short pulses reduce unwanted thermal effects and changes in adjacent tissue to potentially submicron-levels. The parametrically converted radiation source preferably produces pulse durations shorter than 25 ns at or near 3.0 microns but preferably close to the water absorption maximum associated with the tissue. The down-conversion to the desired mid-infrared wavelength is preferably produced by a nonlinear crystal such as KTP or its isomorphs. In one embodiment, a non-critically phased-matched crystal is utilized to shift the wavelength from a near-infrared laser source emitting at or around 880 to 900 nm to the desired 2.9-3.0 microns wavelength range. A fiber, fiber bundle or another waveguide means utilized to separate the pump laser from the optical parametric oscillation (OPO) cavity is also included as part of the invention.

The present invention discloses a new type of extremely low-noise phase-frequency detector (PFD) 500, broadband from DC to multi-GHz RF frequencies for PLL synthesizer applications. Free of any feedback mechanisms, thus inherently fast, it operates close to transition frequency fT of IC processes or frequency limits of discrete mixers. The PFD 500 utilizes complex SSB conversion in both the in-phase and quadrature arms, delaying the in-phase arm in 530, beating the delayed signal 124 with the un-delayed quadrature signal 122 in mixer 126. The output 128 contains both the frequency difference and the phase difference information between the two signals 118 and 520, providing both the frequency-discrimination (FD) and the phase detection (PD) functions. Utilizing standard mixers the PFD 500 can achieve superior CNRs of 180 dBc / Hz at multi-GHz RF. Additionally, utilizing the FD / FM demodulation capability, the present invention improves phase noise of various signals and linearity of FM modulators.

A radar imaging apparatus includes: (i) a delay code generation unit which repeats, for M scan periods, scan processing of generating, using a transmission code, N delay codes in a scan period for scanning N range gates having mutually different distances from the radar imaging apparatus; (ii) a signal storage unit which stores, in association with a range gate and a scan period, a baseband signal; (iii) a memory control unit which repeatedly writes, in the signal storage unit, for the M scan periods, N demodulated signals corresponding to a single scan period, and reads out a group of M demodulated signals corresponding to mutually different scan periods; (iv) a Doppler frequency discrimination unit which performs frequency analysis on demodulated signals having the same range gate; and (v) a direction of arrival calculation unit which estimates a direction of a target.

The present invention discloses a new type of extremely low-noise phase-frequency detector (PFD) 500, broadband from DC to multi-GHz RF frequencies for PLL synthesizer applications. Free of any feedback mechanisms, thus inherently fast, it operates close to transition frequency fT of IC processes or frequency limits of discrete mixers. The PFD 500 utilizes complex SSB conversion in both the in-phase and quadrature arms, delaying the in-phase arm in 530, beating the delayed signal 124 with the un-delayed quadrature signal 122 in mixer 126. The output 128 contains both the frequency difference and the phase difference information between the two signals 118 and 520, providing both the frequency-discrimination (FD) and the phase detection (PD) functions. Utilizing standard mixers the PFD 500 can achieve superior CNRs of 180 dBc / Hz at multi-GHz RF. Additionally, utilizing the FD / FM demodulation capability, the present invention improves phase noise of various signals and linearity of FM modulators.

The invention discloses a sensing device of optical fiber distribution type temperature and stress and mainly comprises a light source module (1), a frequency discriminator module (2), and a thermo tank module (3), which are all connected with one another by polarization-preserving fiber. The invention is a direct detection method which is based on optical fiber Raman scattering used as a carrier wave of temperature information, brillouin scattering used as a carrier wave of stress, rayleigh scattering used for measuring relative frequency of a outgoing laser beam to a frequency discriminator and Fabry-Perot etalon used for discriminating frequency and distributing sensing temperature and stress. The invention has the advantages of simple structure, fine stability, avoidance of outgoing power of the light source during coherent detection, outgoing frequency of the light source. Instability of acoustic modulation or electro-optic modulation frequency is directly referred to measure errors and the direct detection technology of the frequency discrimination is not sensitive to frequency drift of the light source and fluctuation of signal intensity.

The invention discloses a detection method suitable for a sensing device of optical fiber distribution type temperature and stress. The sensing device of the optical fiber distribution type temperature and stress mainly comprises a light source module (1), a frequency discriminator module (2), and a thermo tank module (3), which are all connected with one another by polarization-preserving fiber. The detection method of the invention is a direct detection method which is based on optical fiber Raman scattering used as a carrier wave of temperature information, brillouin scattering used as a carrier wave of stress, rayleigh scattering used for measuring the relative frequency of a outgoing laser beam to the frequency discriminator and Fabry-Perot etalon used for discriminating frequency and distributing sensing temperature and stress. The invention has the advantages of simple structure, fine stability, avoidance of outgoing power of the light source during coherent detection, and outgoing frequency of the light source. Instability of acoustic modulation or electro-optic modulation frequency is directly referred to measure errors and the direct detection technology of frequency discrimination is not sensitive to the frequency drift of the light source and the fluctuation of signal intensity.

Signal-processing devices having memristors are described for performing frequency-discrimination functions, amplitude-discrimination functions, and time-oriented functions. In each case, the time-domain behavior of the memristors described herein enables these functions to be performed. In one embodiment, memristance of an arrangement of memristors of a device is, after an initial transitional period, predominantly at a first level if frequency of an input signal of the device is less than a first frequency and predominantly at a second level if the frequency of the input signal is greater than a second frequency.

The invention discloses an online elastic mode testing system for magnetically suspended electromechanical equipment. The online elastic mode testing system mainly comprises a magnetically suspended system shell, a magnetically suspended rotor, a magnetically suspended control system, a signal excitation module, a vibration detection unit and an elastic mode recognizing module. The signal excitation module is integrated in the magnetically suspended control system, excitation force is applied to the rotor, unbalanced disturbance of translation and rotation and random environmental disturbance of the rotor are simulated, frequency sweeping excitation is increased under the gyroscopic action of a high-speed rotating rigid body, and output signals of a displacement sensor and the vibration detection unit are transmitted to the elastic mode recognizing module to obtain the translation and rotation elastic mode parameters of the rotor and the shell. By adopting the online elastic mode testing system, the influences of noise and unbalanced vibration on an elastic mode can be simulated close to the practical running state of a magnetically suspended, the frequency sweeping excitation output is increased, the near frequency discrimination of elastic modes is enhanced, a rotation elastic mode and a translation elastic mode can be distinguished, and the elastic modes of the rotor and the shell can be tested simultaneously.

The invention discloses a vehicle video identification and speed measuring method. The concrete steps are as follows: (a). obtain a vehicle picture; (b). search the partial threshold value of vehicle license plate on the vehicle picture to obtain the license picture; (c). redress the inclination of the license picture; (d). search the frame of the license plate on the redressed picture and calculate the height of characters; (e). standardize characters on the license plate to obtain a number of partial blocks; (f). carry out the binary system for the partial blocks of each character to obtain two-digit pictures; (g). identify characters on the two-digit pictures to obtain characters on the license plate; (h). track the moving route of the license plate through results of step b and d; (i). calculate the moving distance of the vehicle body; and (j). calculate the running speed. The invention has the advantages of high precision of identifying vehicle licenses and low impact on light reflection of license plate, easy realization, and high practical value.

The invention provides a digital PLL (Phase-Locked Loop) based phase noise measuring device. The digital PLL based phase noise measuring device comprises a frequency power measuring unit, a phase discrimination unit, a filtering unit, a DC (Direct Current) bias compensation unit, a low-noise amplification unit, an acquisition, frequency discrimination and phase discrimination unit, a digital loop filtering unit, a phase discrimination constant detection unit, a self-adaptive digital gain control unit, a reference source unit, and a signal processing and displaying unit. According to the digital PLL based phase noise measuring device, a double-balanced mixer is adopted as a phase discriminator, the phase noise of a measured source is extracted through a digital PLL, the specific noise extraction mode is divided into frequency mixer phase discrimination and digital delay line frequency discrimination, and DC caused by a loop circuit is counteracted through a DC bias compensation circuit, so that too big DC after amplification, induced ADC saturation and induced loop lock-losing are prevented. The implementation scheme of the digital PLL based phase noise measuring device is simple, totally excellent phase noise measuring sensitivity can be realized, the realized analysis frequency spectrum range is also very wide, and phase noise testing demands of most signal sources can be satisfied.

An apparatus and a method for compensating for a mismatch in temperature coefficients of two oscillator frequencies to match a desired frequency ratio between the two oscillator frequencies over a temperature range. In one embodiment of a temperature sensor, first and second oscillators of different temperature characteristics are coupled to a differential frequency discriminator (DFD) circuit. The DFD circuit compensates for the different characteristics in order to match a frequency difference between the first and second frequencies over a temperature range.

The invention discloses a locking indication and fault diagnosis method for passive rubidium atom frequency scale, which adding a phase-adjustable square wave sampling time sequence signal on the basis of synchronization phase discrimination modulation signal and reference signal, wherein frequency of the sequence signal is fourfold of a modulation signal, and duty ratio of the sequence is 1:1. The sampling time sequence carries locking signal collection for an alternating current generated after quantum frequency discrimination, light detection amplification and square wave reshaping to estimate atom frequency scale locking condition at this point. The method uses continuous four rising edges of sampling time frequency of fourfold modulation signal as trigger pulse to carry level sampling for signal after quantum frequency discrimination, levels of the four rising edges are recorded as D1, D2, D3 and D4, atom frequency scale is estimated if it is in locking state according to recorded four sampling levels, when D1=D2 and D3=D4, the atom frequency scale is in locking state. The method can detect operation state and fault point of the passive rubidium atom frequency scale system, and can easily and conveniently exchange fault module.

This invention relates to a digital balance and carrier recover joint algorithm and its circuit structure used in high order quadrature amplitude modulation (QAM). Demodulation becomes difficult since the high-order QAM signal is influenced by the carrier frequency deviation and channel distortion, this invention applies four steps of blind balance, frequency discrimination, phase discrimination and the least square error adaptive balance to obtain the stable balance and carrier recover performance, which can capture the carrier frequency deviation of 9% baud rate. This invention also provides a structure for realizing the circuit.

The invention discloses a rubidium atomic clock with a high contrast ratio frequency discrimination signal. The rubidium atomic clock comprises a controlled crystal oscillator, a frequency multiplication synthesizer, a modulation oscillator, a direct current amplifier, a quantum system and a phase detector, wherein a first Glan-Taylor polarizer is placed on a light path between a beam expander and a physical device; a second Glan-Taylor polarizer is placed between the physical device and the photoelectric detector; and the first Glan-Taylor polarizer and the Glan-Taylor polarizer are orthogonally placed. The transmission backlight intensity is filtered, the first order light frequency shift is eliminated, and the contrast ratio of the frequency discrimination and the rubidium atomic clock property are improved. The high performance atomic clock is provided for satellite navigation, communication and precision measurement.

The invention relates to the laser frequency lock technique, in particular to a method for locking a laser to a tunable transmission peak fiber grating by means of modulation and demodulation to obtain high-frequency stability and tunable performance of the lock wave length of a laser. The method solves the problem that the laser can not be continuously tuned after being locked. Wave length modulation is performed on the laser of the grating, a lock-in amplifier is used for demodulation to obtain frequency discrimination signals, feedback signals are loaded to the modulation port of the laser, and frequency of the laser is locked to the transmission peak of the grating. Tunable wave length output of the lock laser is obtained by changing the environment temperature and regulating the fiber grating transmission wave length. The system and method compress frequency fluctuation of the laser, and achieve continuous tunable laser output with high frequency stability.

Disclosed is a GPS (global positioning system) software receiver tracking method based on an FPGA (field programmable gate array). Inputted digital intermediate-frequency signals are transmitted into a code correlator after multiplying two channels I and Q of a carrier generator to obtain six channels of relevant results; in a carrier tracking loop, IP and QP in six channels of relevant outputs are transmitted into a phase decision device, frequency discrimination computation is carried out by a carrier frequency discriminator when phase deviation meets the condition that delta theta is larger than theta H, phase discrimination computation is carried out by a carrier phase discriminator if the phase deviation meets the condition that delta theta is smaller than theta H, a result is transmitted into the carrier generator after being filtered by a carrier loop filter so that carrier frequency is adjusted; and in a code tracking loop, IE, IL, QE and QL are taken to be transmitted into a code loop discriminator to be in phase discrimination computation, and results are transmitted into a CA (coarse acquisition) code generator after being filtered by a code loop filter so that phase ofCA codes is adjusted. The two loops are cross-coupled, the carrier frequency and the phase of the codes are synchronously tracked, accordingly, locally reproduced carriers and codes are aligned with signals, and navigation data bits are obtained after integral judgment for the IP is carried out by a posterior integral accumulation decision device.

The invention discloses a high-speed multi-channel clock data recovery circuit. The circuit comprises: an oversampling frequency discriminator which is used for receiving a reference clock, and outputting a digital signal after frequency discrimination; a digital filter which is used for receiving and processing the digital signal, and then outputting a comparing control signal; a distributed oscillator which is used for receiving the comparing control signal and generating a high-speed clock signal; a first frequency divider and a second frequency divider which are used for receiving the high-speed clock signal, wherein, an obtained result is transmitted to the oversampling frequency discriminator after the high-speed clock signal is processed by the first frequency divider, and a clock signal which is needed in an operation performed by the digital filter is generated after the high-speed clock signal is processed by the second frequency divider; a delay loop which is used for receiving the high-speed clock signal and generating n pairs of clock signals; and n oversampling data clock generators each of which receives a pair of clock signals output by the delay loop and one channel of high-speed data corresponding to the pair of the clock signals, and processes and recovers the clock signals and the high-speed data corresponding to the clock signals. The high-speed multi-channel clock data recovery circuit has the advantages of strong programmability and wide adaptability.

The invention discloses a phase lock loop frequency synthesizer with quick lock function, comprising a phase lock loop (101) and a quick lock logic unit (102). The phase lock loop (101) consists of a frequency discrimination phase discriminator (501), a charge pump (502), a voltage control oscillator (503), a programmable multimode frequency divider (504) and a loop filter (511). The quick lock logic unit (102) consists of a logic control circuit (508), a unit gain follower (509) and a phase lock monitor (510). The invention realizes the quick lock of the frequency synthesizer, and the quick lock logic unit has simple structure and low power consumption. The invention is especially suitable for a wireless radio frequency communication system which requires low power consumption and quick lock.

The invention discloses a loop response time measuring device and method used for an atomic frequency standard. The device comprises an oscillation module, an executing module and a signal detecting module, wherein the oscillation module is used for receiving an output signal of a servo loop of an atomic frequency standard and outputting the signal after reversing the phase of the output signal of the servo loop of the atomic frequency standard; the executing module is used for acting according to the output signal of the oscillation module to control the quantum system of the atomic frequency standard to finish the quantum frequency discrimination; and the signal detecting module is used for measuring the oscillation period of the oscillation loop according to the output signal of the oscillation module, and the oscillation loop consists of an oscillation module, an executing module and an atomic frequency standard. The method comprises the following steps of: obtaining the oscillation period of the oscillation module; measuring the oscillation period of the oscillation loop; and calculating the loop response time of the atomic frequency standard according to the oscillation period of the oscillation loop and the oscillation period of the oscillation module. By adopting the device and the method provided by the invention, the loop response time of the atomic frequency standard system can be measured accurately.

The invention discloses a microwave differential gain-based coherent Doppler wind lidar. According to the technical scheme of the invention, a balanced detector is connected with a bandpass filter, so that invalid signals, away from the Doppler frequency shift, are filtered and eliminated. A pre-amplifier is adopted to amplify an electrical signal outputted by the detector. Meanwhile, a power divider is adopted to divide amplified electrical signal into a monitoring channel and a detection signal. The detection signal is filtered by a pre-emphasis filter. The frequency-domain change of the detection signal is converted to the intensity change of the signal. Through the comparison with the monitoring channel and the transmittance curve of the pre-emphasis filter, the Doppler shift information is obtained. The interference of invalid echo signals is reduced. By adopting the pre-emphasis filter, echo signals are subjected to frequency discrimination, so that the computation amount of signal processing is reduced. The sensitivity and the signal-to-noise ratio of the system are improved. The coherent Doppler wind lidar is higher in resolution distance.

There is provided a physical random number generation method and a physical random number generator by which safe random numbers can be obtained at high speed. The physical random number generator comprises a laser equipment which irradiates laser light, a frequency discrimination filter which discriminates frequencies of the laser light, an photodetector which converts intensity of laser light into electric signals, an on-off detector or an A / D converter which converts analogue signals output from the photodetector as a detected result into digital data. First, the laser light irradiated from the laser equipment is allowed to pass through the frequency discrimination filter. Transmitted light changes in intensity depending on frequency fluctuations of the laser light. Then, this intensity of the transmitted light is converted into electric signals by the photodetector to be converted into binary random numbers using the on-off detector or the A / D converter. Finally, the binary random number data thus generated are imported into a PC.

An all-fiber Doppler lidar wind field detection system comprises a laser emission system, an optical receiving system, a frequency discrimination and optical detection system and a signal processing system, wherein the frequency discrimination and optical detection system is connected with the signal processing system; the laser emission system and the optical receiving system are connected with the frequency discrimination and optical detection system through multi-mode / single-mode converters; the laser emission system emits laser light into the atmosphere; the optical receiving system receives backscattering light of atmospheric molecules and couples the backscattering light into multimode fibers, then, the backscattering light is fed into the signal processing system after entering the frequency discrimination and optical detection system for processing through the multi-mode / single-mode converters, and wind speed information is obtained after the backscattering light is processed. A fiber M-Z interferometer is used as a frequency detector, the wavelength range is wide, the selectivity of a laser light source is high, the ability to resist external interference is high, and spectral resolution and light splitting efficiency are high; in this way, the stability of detection is improved, detection accuracy is high, and the all-fiber Doppler lidar wind field detection system is convenient to use.

The invention provides a microwave photon doppler frequency shift measuring system and a regulating method thereof. Electro-optical modulation is realized by a radio-frequency signal and an echo signal through a polarization multiplexing mach-zehnder modulator, balance detecting is combined, through digital signal processing, frequency discrimination information is obtained to realize doppler frequency shift measuring of a broadband radio-frequency signal, meanwhile, second order intermodulation distortion is suppressed in a photocurrent detected by a balance detector, and thus measuring performance of the doppler frequency shift measuring system is greatly improved. According to the adopted broadband microwave photon doppler frequency shift measuring system, PDM-MZM is driven by the ratio-frequency signal in a push-pull mode, and second order intermodulation distortion is suppressed by PBS and balance detecting. The microwave photon doppler frequency shift measuring system and the regulating method thereof are simple in structure and high in operability; and the modulator with the high symmetry degree, accurate bias control, and BPD with good responsivity balance and the high common-mode rejection ratio can be adopted to improve the suppression effect of second order intermodulation distortion so as to realize high-accurate broadband microwave photon doppler frequency shift measurement.

The invention discloses an optical fiber microwave and optical frequency simultaneous transmission device and transmission method. The optical fiber microwave and optical frequency simultaneous transmission device comprises a local end, an optical fiber link and a user end. Microwave and optical frequency are coupled at the local end through a broadband electro-optical coupling and frequency shifting unit, and THE coupled signals comprise two paths of optical frequency signals and are sent to the user end through the optical fiber link. the user end returns the received signals to the local end again through the same path via the frequency shift unit and the light reflection unit. The phase noise introduced by the optical fiber link is obtained by comparing the signals subjected to electro-optical conversion and frequency mixing processing with the phase frequency discrimination of a microwave signal to be transmitted at the local end, and the dynamic compensation of the phase noise introduced by the optical fiber link is realized by dynamically adjusting the working frequency loaded to the electro-optical coupling and frequency shifting module at the local end. Two paths of optical frequencies with stable phases and microwave signals with stable phases between the two paths of optical frequencies are obtained at the user end, so that simultaneous transmission of microwaves andoptical frequencies is realized. Broadband coupling of microwave and optical frequency and system compensation of phase noise are achieved through the broadband electro-optical coupling and frequencyshift module, integrated optical fiber microwave and optical frequency simultaneous transmission is achieved, and the system is simple in structure and high in reliability.

The invention provides an ultrasonic ranging method and ranging device with high anti-interference performance. Frequency modulation is conducted on a sine wave signal generated by a sine-wave generator through a pseudo code, and transmitting ultrasonic wave is generated and transmitted; echo frequency discrimination demodulation is conducted on the ultrasonic wave echo, so that echo identification is achieved, and the detection is more accurate; moreover, the pseudo code has a good self-correlation characteristic and a good cross-correlation characteristic, and when the pseudo code is applied to the spread spectrum communication, good noise interference-resistant performance and good mutual crosstalk-resistant performance are represented, so that the problem of mutual crosstalk of the ultrasonic wave is solved and the result is accurate; furthermore, the FFT technology is adopted, so that the received wave can be accurately modulated through a few sampling data, frequency resolution is guaranteed, data collecting time of the received wave is shortened, real-time work of the ranging device is greatly improved, and an efficient solution for accurate and rapid ranging and positioning is provided for an autonomous mobile robot.

The invention discloses an improved rubidium atom frequency scale, which comprises a voltage controlled crystal oscillating module, an isolation amplifying module, a microprocessor, a digital frequency synthesis module, a radio frequency multiplication module, a physical system module, a first synchronous phase discrimination module and a temperature compensating module. The isolation amplifying module is used for isolating and amplifying output frequencies of the voltage controlled crystal oscillating module; the microprocessor is used for generating a frequency synthetic instruction, a key-controlled frequency modulation signal and a synchronous phase discrimination reference signal; the digital frequency synthesis module is used for generating a comprehensive modulation signal according to the frequency synthetic instruction and the key-controlled frequency modulation signal generated by the microprocessor; the radio frequency multiplication module is used for generating a microwave polling signal; the physical system module is used for carrying out frequency discrimination on the microwave polling signal and generating a quantum frequency discrimination signal; the first synchronous phase discrimination module is used for carrying out phase discrimination on the quantum frequency discrimination signal and generating a first voltage control signal and the temperature compensating module is used for measuring surrounding temperature of the voltage controlled crystal oscillating module and generating a second voltage control signal according to the temperature. The invention can compensate the influence on the output frequencies of the voltage controlled crystal oscillating module due to the temperature so as to improve the stability of the output frequency of the rubidium atom frequency scale.

The short range radio receiver for motor vehicle data comprises antenna circuits (1–4) connected to a unit (10–15) for processing a carrier in a plurality of specific frequency bands which is modulated by a data signal, the unit (10–15) comprising frequency-transposing circuits (11, 23–28) connected to demodulation circuits (13) supplying the demodulated data, and frequency discrimination circuits (21, 22) are provided, connected to the antenna circuits (1–4), to determine respective reception levels within the bands in order to compare them with each other and to control the frequency transposing circuits (11, 23–28) depending on the result of the comparison.

The embodiment of the invention discloses a frequency discrimination phase discriminator. The phase discriminator comprises two D triggers D1 and D2, as well as a nand gate NA1 and a buffer 1, the output ends of the two D triggers D1 and D2 are utilized as an input end of the nand gate; an output end of the nand gate NA1 passes through the buffer 1 to utilize as a second reset terminal RST 2 of the two D triggers, and the output ends of the D trigger D1 and the D trigger D2 can respectively obtain signal Q1 and Q2; and the phase discriminator also comprises a timing control unit, the signals Q1 and Q2 are input signals of the timing control unit, and the timing control unit is used for controlling phase and pulse width of an output signal of the frequency discrimination phase discriminator. The invention also discloses a charge pump phase locked loop applying to the frequency discrimination phase discriminator and a method of a phase locked loop applying to the frequency discrimination phase discriminator. The technical scheme of the phase discriminator and the phase locked loop and the method can effectively avoid an error caused by mismatch charge pump current through a simple circuit structure.