Instantaneous measurement for radar target polarization scattering matrix

Adopting ＂simultaneous transmitting, simultaneous receiving＂ operational scheme, instantaneous polarization radar （IPR） can measure target polarization scattering matrix （PSM） using only once target echoes in two orthogonal polarization channels. Firstly, signal model and signal process are advanced under narrowband condition. Secondly, measurement performances of two typical IPR waveforms are analyzed in detail. At last, field experiments are carried out using X-band IPR system designed by National University of Defense Technology （NUDT）, China. Compared with results obtained by alternative polarization measurement scheme, following results can be obtained： the difference of relative amplitude measurement results is smaller than 2 dB and that of relative phase measurement results is smaller than 10？, verifying the validity of instantaneous polarization measurement scheme.

High Sensitivity Digital Instantaneous Frequency Measurement Receiver for Precise Frequency Analysis

There are numerous applications, such as Radar, that leverage wideband technology. However, the presence of noise introduces certain limitations and challenges. It is crucial to harness wideband technology for applications demanding the rapid and precise transmission of diverse information from one point to another within a short timeframe. The ability to report a signal without tuning within the input bandwidth stands out as one of the advantages of employing a digital wideband receiver. As indicated, a digital wideband receiver plays a pivotal role in achieving high precision and accuracy. The primary distinction between Analog and Digital Instantaneous Frequency Measurement lies in the fact that analog Instantaneous Frequency Measurement (IFM) receivers have traditionally covered extensive input bandwidths, reporting one accurate frequency per short pulse. In the contemporary landscape, digital IFM systems utilize high-sampling-rate Analog-to-Digital Converters (ADC) along with Hilbert transforms to generate two output channels featuring a 90-degree phase shift. This paper explores the improvement of sensitivity in current digital IFM receivers. The optimization efforts target the Hilbert transform and autocorrelations architectures, aiming to refine the system’s ability to report fine frequencies within a noisy wide bandwidth environment, thereby elevating its overall sensitivity.

Instantaneous rotation speed measurement and error analysis for variable speed hydraulic system

In order to monitor the working state of piston motor and measure its instantaneous rotation speed accurately, the measuring principle and method of instantaneous rotation speed based on industrial personal computer and data acquisition card are introduced, and the major error source, influence mechanism and processing method of data quantization error are dis- cussed. By means of hybrid programming approach of LabVIEW and MATLAB, the instantaneous rotation speed measurement system for the piston motor in variable speed hydraulic system is designed. The simulation and experimental results show that the designed instantaneous speed measurement system is feasible. Furthermore, the sampling frequency has an important influ- ence on the instantaneous rotation speed measurement of piston motor and higher sampling frequency can lower quantization er- ror and improve measurement accuracy.

Instantaneous frequency measurement using two parallel I/Q modulators based on optical power monitoring

A scheme for instantaneous frequency measurement(IFM)using two parallel I/Q modulators based on optical power monitoring is proposed.The amplitude comparison function(ACF)can be constructed to establish the relationship between the frequency of radio frequency(RF)signal and the power ratio of two optical signals output by two I/Q modulators.The frequency of RF signal can be derived by measuring the optical power of the optical signals output by two I/Q modulators.The measurement range and measurement error can be adjusted by controlling the delay amount of the electrical delay line.The feasibility of the scheme is verified,and the corresponding measurement range and measurement error of the system under different delay amounts of the electrical delay line are given.Compared with previous IFM schemes,the structure of this scheme is simple.Polarization devices,a photodetector and an electrical power meter are not used,which reduces the impact of the environmental disturbance on the system and the cost of the system.In simulation,the measurement range can reach 0 GHz-24.5 GHz by adjusting the delay amount of the electrical delay lineτ=20 ps.The measurement error of the scheme is better at low frequency,and the measurement error of low frequency 0 GHz-9.6 GHz can reach-0.1 GHz to+0.05 GHz.

A new method for high precsion instantaneous speedmeasurement of hydraulic system

The instantaneous speed of a hydraulic system contains a wealth of operational information,and its accurate extraction is the basis for condition monitoring and fault diagnosis.In order to solve the problem of high hardware requirement for instantaneous speed measurement based on data acquisition card,a new method of high precision measurement is proposed.In this method,the time-displacement information of each tooth is obtained from the pulsed square wave signal of the gear disk collected by magnetoelectric sensors.The time-displacement curve is interpolated by the cubic spline interpolation method,and then the instantaneous speed is calculated by the five-point digital differential formula.The experimental results show that the method improves the speed measurement resolution and reduces the quantization error.The high precision instantaneous speed signal can also be acquired by hardware devices with less teeth and low sampling frequency.The related research results provide a theoretical basis and a method for improving the accuracy of instantaneous speed measurement.

Switchable instantaneous frequency measurement by optical power monitoring based on DP-QPSK modulator

We propose and analyze an instantaneous frequency measurement system by using optical power monitoring technique with improved resolution.The primary component adopted in the proposal is a dual-polarization quadrature phase shift keying(DP-QPSK) modulator which is used to modulate the microwave signal that has a designed time delay and phase shifting.The generated optical signal is sent to polarization beam splitter(PBS) in DP-QPSK modulator.Owing to the complementary transmission nature of polarization interference introduced by PBS,the frequency information is converted into the optical power and the relationship between the amplitude comparison function(ACF) and microwave frequency to be measured is established.Thus,the frequency of the microwave signal can be easily measured through monitoring the optical powers of the two output ports of the PBS.Furthermore,by adjusting the direct current(DC) biases of the DP-QPSK modulator instead of changing the electrical delay,the measurement range and resolution can be switched.In this paper,the basic principle of the instantaneous frequency measurement system is derived in detail,and simulation has been performed to investigate the resolution,the measurement range,and the influence of imperfection devices.The proposed scheme is wavelength-independent and its measurement range is switchable,which can avoid the laser wavelength drifting problem and thus greatly increasing the system flexibility.

Photonic-assisted approach for instantaneous microwave frequency measurement with tunable range by using Mach-Zehnder interferometers

A novel photonic-assisted approach to microwave frequency measurement is proposed and experimentally demonstrated. The proposed scheme is based on the frequency-to-power mapping with different transmis- sion responses. A polarizer is used in one output branch of a phase modulator to simultaneously implement phase modulation and intensity modulation. Owing to the complementary nature of the transmission re- sponses and the Mach-Zehnder interferometers （MZIs）, this scheme theoretically provides high resolution and tunable measurement range. The measurement errors in the experimental results can be kept within 0.2 GHz over a freauencv ranee from 0.1 to 5.3 GHz.

Broadband instantaneous multi-frequency measurement based on chirped pulse compression

A broadband instantaneous multi-frequency measurement system based on chirped pulse compression,which potentially has a sub-megahertz(MHz)accuracy and a hundred-gigahertz(GHz)measurement range,is demonstrated.A signalunder-test(SUT)is converted into a carrier-suppressed double-sideband(CS-DSB)signal,which is then combined with an optical linearly frequency-modulated signal having the sweeping range covering the+1 st-order sideband of the CSDSB signal.With photodetection,low-pass filtering,and pulse compression,accurate frequencies of the SUT are obtained via locating the correlation peaks.In the experiment,single-and multi-frequency measurements with a measurement range from 3 to 18 GHz and a measurement accuracy of<±100 MHz are achieved.

Chip-scale Brillouin instantaneous frequency measurement by use of one-shot frequency-to-power mapping based on lock-in amplification

We demonstrate a chip-scale scheme of Brillouin instantaneous frequency measurement(IFM) in a CMOS-compatible doped silica waveguide chip. In the chip-scale Brillouin IFM scheme, the frequency-to-power mapping process is achieved by one-shot detection without additional time averaging and implemented by lock-in amplification, which successfully detects the Brillouin gain of the doped silica waveguide chip in the time domain. A Costas frequency modulated signal ranging from 8 GHz to 9 GHz is experimentally measured, and the frequency measurement errors are maintained within 58 MHz.