Frequency Measurement Method Research Articles

Microwave frequency measurement method using microwave phase detection

In modern warfare, communication carrier frequency of opponent's communication radar should be frequently measured, so as to make demodulation and obtain its binary communication information for declassification. To make demodulation on opponent's communication signal, certain method must be adopted to estimate the frequency of such communication microwave signal. Therefore, the measurement of the frequency of unknown microwave signal is an important application in military warfare. In this study, a new microwave frequency measurement method is proposed based on the detection of unknown microwave signal's phase shift. Theoretical analysis has been made. The formula of theoretical derivation can prove the feasibility of the project. Relevant experimental verification has been conducted. The final experiment in this study also proves the practicality and feasibility of the method.

Real-Time Determination of Absolute Frequency in Continuous-Wave Terahertz Radiation with a Photocarrier Terahertz Frequency Comb Induced by an Unstabilized Femtosecond Laser

A practical method for the absolute frequency measurement of continuous-wave terahertz (CW-THz) radiation uses a photocarrier terahertz frequency comb (PC-THz comb) because of its ability to realize real-time, precise measurement without the need for cryogenic cooling. However, the requirement for precise stabilization of the repetition frequency (f rep) and/or use of dual femtosecond lasers hinders its practical use. In this article, based on the fact that an equal interval between PC-THz comb modes is always maintained regardless of the fluctuation in f rep, the PC-THz comb induced by an unstabilized laser was used to determine the absolute frequency f THz of CW-THz radiation. Using an f rep-free-running PC-THz comb, the f THz of the frequency-fixed or frequency-fluctuated active frequency multiplier chain CW-THz source was determined at a measurement rate of 10 Hz with a relative accuracy of 8.2 × 10−13 and a relative precision of 8.8 × 10−12 to a rubidium frequency standard. Furthermore, f THz was correctly determined even when fluctuating over a range of 20 GHz. The proposed method enables the use of any commercial femtosecond laser for the absolute frequency measurement of CW-THz radiation.

High-precision measurement of terahertz frequency using an unstabilized femtosecond laser

Frequency is one of the most important physical quantities of electromagnetic (EM) waves. With the development of terahertz (THz) technology, high-precision measurement of THz frequency is required in THz laser development, wireless communication and ultra fine spectrum measurement. The traditional Fabry-Perot (F-P) interferometry and heterodyne detection method are both difficult to achieve high-precision measurement of THz frequency. Within the range of light wave band, the femtosecond optical frequency comb has long been applied to the light wave frequency measurement due to its extremely high accuracy and stability. By using frequency comb method, measurement with accuracy in the order of 10-11 can also be achieved in THz band. To generate THz frequency combs with stable and controllable frequency, it is required to conduct precise stabilization control on repetition frequency of the femtosecond laser. As a result, some special designs are needed for the femtosecond laser in addition to repetition frequency control devices, including the reference signal source, servo-control module, HV drive module, temperature control module, etc., resulting in a rather complicated system. In this paper, a new method for THz frequency measurement by using an unstabilized femtosecond laser is introduced. The laser is free running and the repetition frequency continuously reduces approximately 8 kHz in 6 h, which is the result of a lengthened laser cavity due to the thermal expansion caused by temperature rise after the laser has been switched on. The repetition frequency and beat signal frequency are simultaneously and continuously measured by two frequency counters. The THz frequency can be calculated from the data with accuracy in the order of 10-10. Although the measurement precision is reduced by one order compared with that obtained by using stabilized femtosecond laser, the system is greatly simplified. The femtosecond laser and complicated repetition frequency control devices no longer need to be specifically designed. This new method will greatly expand the applicable scope of the frequency comb method in measuring THz frequency.

Research of Electrical Conductivity Measurement System for Mine Bursting Water Based on Dual Frequency Method

This paper presents a double frequency conductivity measurement method for measuring mine bursting water, to solve the capacitance effect of the conductivity sensor itself has the help. The core controller of the system is the single chip microcomputer ATMEGA128. This paper introduces the basic principle of the measurement of the existing problems and the dual frequency measurement method, and then introduces and analyzes the hardware. To test and analyze the collected data, the double frequency method is found to have good stability and accuracy in the measurement of the electrical conductivity of mine inrush water. It is proved that the method and the system design of the hardware circuit can accurately measure the electric conductivity of the mine inrush water source.

Frequency Domain Sensors and Frequency Measurement Techniques

Getting fast and accurate information is of paramount importance for most monitoring, data acquisition, and monitoring systems; there are sensors that transform their input into a frequency domain output, this kind of sensors are known as Frequency Domain Sensors (FDS); when the value of the output frequency is measured in a FDS, the value of the sensor’s input (measurand) can be calculated, that is why the frequency measurement in the output of FDS is critical for using such sensors. In this work different kinds of resonant sensors (FDS) are reviewed; also frequency measurement techniques are explored; finally a novel frequency measurement method is proposed and analyzed for resolution improvement in frequency domain sensors.

Scaling instantaneous frequency measurement method inspired by hawk'S eye

A scaling instantaneous frequency measurement (IFM) method inspired by hawk's eye is proposed, by which the frequency measurement precision can be improved to 5–10 times comparing to conventional digital IFM method. The hawk's eye has nasal fovea and temporal fovea. The nasal fovea searches out preys in large scale, and then, the temporal fovea acquires preys' detail by shrinking the scale. Similar to the hawk's eye, the proposed method measures the instantaneous frequency in a large scale first; then, shrinks the scale and measures the frequency in small scale to obtain high precision. A microwave scaling IFM system was developed to evaluate the method. The theory simulation and experimental results prove its high precision. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1383–1385, 2015

一种改善实时性的光辅助微波频率测量方法的研究

一种改善实时性的光辅助微波频率测量方法的研究

Frequency Measurement Method Based on Signal Delay Detection

A frequency measurement method based on signal delay detection is presented. The method adopts multi-path same delay line to generate multi-path delayed signal whose period is almost the same with that of the reference signal, the average delay time of two adjacent signals that are detected is selected as the interval between the reference signal's rising edge and gate's opening and closing time to calculate the frequency of the measured signal. Error analysis and measurement uncertainty evaluation show that the precision of measurement of the method is determined by the delay time. Experimental data verify that the method could ensure testing speed while effectively reduce the error of ± 1 count.

Research on Fm Telemetry Signal Demodulation Based on Instantaneous Frequency Measurement

According instantaneous frequency measurement theory, we propose a new PCM/FM telemetry signal demodulation method. This paper introduces the basic principles of this demodulation method and implementation process, the influence of instantaneous frequency measurement accuracy and the impact of factors on the Doppler frequency demodulation performance is proposed to improve the accuracy and instantaneous frequency measurement method demodulation performance. Simulation results show that this method is superior demodulation performance, strong anti-jamming capability, ease of software programming and DSP devices to achieve.

Windowed DFT Method for Frequency Measurement Involving Amplitude Modulation

A windowed DFT method is proposed for power system frequency measurement involving amplitude modulation. First, an error analysis of conventional DFT based method considering amplitude modulation is given. Second, a noval a window DFT function is proposed method to eliminate these errors is given based on the relation among three consecutive DFT values. Due to its high precision and low required processing effort, the proposed algorithm is a good candidate for online frequency measurement.

Research on Demodulation of Pulse Code Modulated Signal Based on Instantaneous Frequency Measurement

According instantaneous frequency measurement theory, we propose a new PCM / FM telemetry signal demodulation method. This paper introduces the basic principles of this demodulation method and implementation process, the influence of instantaneous frequency measurement accuracy and the impact of factors on the Doppler frequency demodulation performance is proposed to improve the accuracy and instantaneous frequency measurement method demodulation performance .

FPGA‐based high accuracy burst carrier frequency measurement method

A burst carrier frequency measurement scheme combined with a timestamping counting method based on a field programmable gate array (FPGA) is proposed. With the multiplication and phase shift of count clock, multiple parallel counters are continuously counted, and the times of the rising edge of the unknown frequency fx are counted simultaneously. To obtain the frequency of fx , linear regression by use of least-squares line fitting is used. Experimental results show that the proposed approach can effectively reduce the error introduced by the quantisation error of ±1, improve measurement accuracy by about 2 to 3 bit, reduce measurement uncertainty by more than 20% and diminish the processing time to 200 ns compared with the traditional methods under the same conditions.

Wide Frequency Operation of the Inductive Current Transformer with Ni80Fe20 Toroidal Core

—During transformation of the power frequency currents, inductive current transformers are characterized by the values of current errors and phase displacement, which determine their accuracy class. However, current transformers catalogues do not specify these metrological parameters of transformation for the sinusoidal signals at frequencies higher than 50 Hz (60 Hz). The aims of this article are the descriptions of the metrological and magnetic circuit properties of the inductive current transformers with an Ni80Fe20 toroidal core in condition of sinusoidal currents transformation of frequencies from 50 Hz to 20 kHz. Determined magnetization characteristics of tested current transformer magnetic circuit are the justification for the course of its measured wide frequency metrological characteristics. Moreover, they may be used in designing the current transformers with an Ni80Fe20 toroidal core for transformation of the above 50-Hz frequency currents. The classification procedure was used in this article to define the current transformers accuracy for wide frequency operation and measurement method for determining their current errors and phase displacement for transformation of sinusoidal signals at frequencies from 50 Hz (60 Hz) to 20 kHz are presented.

A new time-domain method for frequency measurement of sinusoidal signals in critical noise conditions

Frequency measurement of sinusoidal signals corrupted by noise is dealt with. A new time-domain, digital signal processing method, based on an enhanced version of the zero-crossing technique, is in particular proposed. To obtain the desired frequency value, the method exploits the histogram of time intervals between consecutive zero-crossing events, and works with success in the presence of zero-mean additive noise.Several tests conducted on simulated and actual sinusoidal signals highlight the good performance of the method also in critical noise conditions, which make high-end measurement instruments like digital counters poorly fail. Moreover, the obtained results concur with those granted by competitive digital signal processing proposals operating in the frequency domain. With respect to these latter, the main advantage of the method relies on the limited computational resources required, which suggests its implementation even in low-performance processing devices for the realization of cost-effective measurement instruments.

High-resolution frequency measurement method with a wide-frequency range based on a quantized phase step law

A wide-frequency and high-resolution frequency measurement method based on the quantized phase step law is presented in this paper. Utilizing a variation law of the phase differences, the direct different frequency phase processing, and the phase group synchronization phenomenon, combining an A/D converter and the adaptive phase shifting principle, a counter gate is established in the phase coincidences at one-group intervals, which eliminates the ±1 counter error in the traditional frequency measurement method. More importantly, the direct phase comparison, the measurement, and the control between any periodic signals have been realized without frequency normalization in this method. Experimental results show that sub-picosecond resolution can be easily obtained in the frequency measurement, the frequency standard comparison, and the phase-locked control based on the phase quantization processing technique. The method may be widely used in navigation positioning, space techniques, communication, radar, astronomy, atomic frequency standards, and other high-tech fields.

High-precision time and frequency measurement method combining time-space conversion and different frequency phase detection

According to the time & space conversion relations and different frequency phase detection principle, an ultra-high precision time & frequency measurement method is proposed in this paper. The higher accuracy and stability of the speed of light and electromagnetic signals during the transmission in space or a specific medium enable the measurement of short time interval which uses the coincidence detection of signal’s transmission delay in length. The measurement precision better than 10 picoseconds can be easily obtained. The method develops the length vernier utilizing the stability of signal’s transmission delay, minimizes the fuzzy region of phase coincidence between the standard frequency signal and the measured signal, approaches the best phase coincidences and therefore improves the measurement precision which is higher than the precision provided by the traditional methods based on frequency processing. Besides, the method costs less than the traditional methods and can also solve the problem of the measurement of super-high frequency. Experimental results show the method can improve the measurement precision to 10−12/s in the time & frequency domain.

Application Research of Sweep Frequency in GMI Test

Because of inefficiency of many tests needed in GMI research, this paper put forward the sweep frequency measurement method to implement the measurement of GMI effect under multi frequency at the same time in a single test. Experiments proved that the GMI effect curves which are measured by the sweep measurement method are consistent with other method's results, and the sweep frequency measurement method can greatly reduce the time of GMI test and improving the efficiency of the test.

Study on the Transfer Function Test Method for Electro-Optical Tracking Servo Control System

The error of gain of servo control system transfer function is larger by the method of frequency measurement, In this paper, By appying voltage on the both ends of the motor, measure DC response of system to tmeasure the DC gain of control object.Experimental results show that the gain accuracy by the measurement method increases 2.5 times than the traditional measurement.

A Comparative Study on Frequency Estimation Methods

In this paper, a comparative study on the frequency estimation methods using IRDWT (Improved Recursive Discrete Wavelet Transform), FRDWT(Fast Recursive Discrete Wavelet Transform), and GCDFT(Gain Compensator Discrete Fourier Transform) is presented. The 345[kV] power system modeling data of the Republic of Korea by EMTP-RV is used to evaluate the performance of the proposed two kinds of RDWT(IRDWT and FRDWT) and GCDFT. The simulation results show that the frequency estimation technique based on FRDWT could be the optimal frequency measurement method, and thus can be applied to FDR(Fault Disturbance Recorder) for wide-area blackout protection or frequency measurement apparatus.

광역 보호계전 지능화를 위한 동적 주파수 모니터링 S/W 개발

The social and economic level of damages might be highly increased in the case of wide-area black-outages, because of heavy dependence of electricity. Therefore, the development of a wide-area protection relay intelligence techniques is required to prevent massive power outages and minimize the impact strength at failure. The frequency monitoring and prediction for wide-area protection relaying intelligence has been considered as an important technology. In this paper, a network-based frequency monitoring system developed for wide-area protection relay intelligence is presented. In addition, conventional techniques for frequency estimation are compared, and a method for advanced frequency estimation and measurement to improve the precision is proposed. Finally, an integrated monitoring system called K-FNET(Korea-Frequency Monitoring Network) is implemented based on the GPS and various energy monitoring cases are studied.