Instantaneous Frequency Measurement Research Articles

A Novel Method Based on Probability Density Function Used in Instantaneous Frequency Measurement System for Wider Range and Less Error

A Novel Method Based on Probability Density Function Used in Instantaneous Frequency Measurement System for Wider Range and Less Error

Photonic architecture for remote multi-parameter measurement and transmission of microwave signals

Photonic architecture for remote multi-parameter measurement and transmission of microwave signals

All-optical instantaneous RF signal frequency measurement system based on a linear ACF with a steep slope

A new microwave photonic structure for measuring the frequency of an RF signal, to the best of our knowledge, is presented. The frequency of an unknown RF signal can be determined by simply measuring the system output optical powers. The proposed frequency measurement system can be designed so that the ratio of the two system output optical powers as a function of the RF signal frequency or the amplitude comparison function (ACF) has a steep linear slope over a wide frequency range. This enables the RF signal frequency to be measured in high resolution and high accuracy. The proposed frequency measurement system has a simple and compact structure, and is free of high-speed photodetectors as well as RF components and instruments. It also has a fast response time compared to many reported photonics-based frequency measurement systems. A proof-of-concept experiment is carried out. Experimental results show a linear ACF with a slope of more than 4.4 dB/GHz over a frequency measurement range of 5–26 GHz and a frequency measurement accuracy of better than ±0.1GHz.

An instantaneous frequency measurement system based on quantum dash mode-locked laser

An instantaneous frequency measurement system based on quantum dash mode-locked laser

Instantaneous frequency measurement based on photonic compressive sensing with sub-Nyquist pseudo-random binary sequences.

We propose a novel, to the best of our knowledge, approach to realizing instantaneous frequency measurement with ultrahigh measurement bandwidth, which utilizes three-channel photonic compressive sensing (CS) with sub-Nyquist pseudo-random binary sequences (PRBSs). In each CS channel, an alias frequency is recovered due to the sub-Nyquist property of the applied PRBS. A frequency identification algorithm is employed to determine the frequency of the signal under measurement according to the three alias frequencies. The proposed approach significantly reduces the bit rate of the applied PRBSs and the sampling rate required by the digitizers in CS. A proof-of-concept experiment for measuring frequency in the Ku band is demonstrated using PRBSs at 1 Gb/s and digitizers with a sampling rate of 250 MS/s.

Machine-Learning-Assisted Instantaneous Frequency Measurement Method Based on Thin-Film Lithium Niobate on an Insulator Phase Modulator for Radar Detection.

A simple microwave photonic, reconfigurable, instantaneous frequency measurement system based on low-voltage thin-film lithium niobate on an insulator phase modulator is put forward and experimentally demonstrated. Changing the wavelength of the optical carrier can realize the flexibility of the frequency measurement range and accuracy, showing that during the ranges of 0-10 GHz, 3-15 GHz, and 12-18 GHz, the average measurement errors are 26.9 MHz, 44.57 MHz, and 13.6 MHz, respectively, thanks to the stacked integrated learning models. Moreover, this system is still able to respond to microwave signals of as low as -30 dBm with the frequency measurement error of 62.06 MHz, as that low half-wave voltage for the phase modulator effectively improves the sensitivity of the system. The general-purpose, miniaturized, reconfigurable, instantaneous frequency measurement modules have unlimited potential in areas such as radar detection and early warning reception.

Multi-tier dynamic sampling weak RF signal estimation theory

This paper presents a theoretical analysis in discrete time for a multi-tier weak radiofrequency (RF) signal estimation process with N simultaneous signals. Discrete time dynamic sampling is introduced and is shown to provide the capability to extract signal parameter values with increased accuracy compared with accuracy of estimates obtained in prior work. This paper advances phase measurement approaches by proposing discrete time dynamic sampling which our paper shows offers the desirable capability for more accurate weak signal parameter estimates. For N=2 simultaneous signals with a strong signal at 850 MHz and a weak signal at 855 MHz, the results show that dynamically sampling the instantaneous frequency at 24 times the Nyquist rate provides weak signal frequency estimates that are within 1.7 times 10^{-5} of the actual weak signal frequency and weak signal amplitude estimates that are within 428 PPM of the actual weak signal amplitude. Results are also presented for situations with N=2 simultaneous 5G signals. In one case, the strong signal is 3950 MHz, and the weak signal is 3955 MHz; in the other case the strong case is 5950 MHz, and the weak signal is 5955 MHz. The results for these cases show that estimates obtained with dynamic sampling are more accurate than estimates provided using a single sample rate of 65 MSPS. This work has promising applications for weak signal parameters estimation using instantaneous frequency measurements.

Photonic instantaneous microwave frequency measurement based on frequency-phase mapping with high precision

This paper presents an instantaneous microwave frequency measurement scheme based on a frequency-phase mapping technique. In our scheme, a low-frequency (LF) reference signal and two microwave signals with a relative time delay are modulated on the optical carriers via two dual-parallel Mach–Zehnder modulators. The generated electrical signal has the same frequency as that of the LF reference signal, but with a phase shift, which depends on the microwave signal frequency and the time delay. Therefore, a linear frequency-phase mapping function with a high slope is constructed, which improves the accuracy of the whole frequency measurement range. The scheme has a compact structure without an optical filter and polarization devices, which enhances the long-term stability of the system. The simulation shows that our scheme has a 4.1–40 GHz frequency measurement range with errors less than ±0.04 GHz.

Radiophotonic methods and means for the resolution increase of a continuous-wave radar with an FBG discriminator

During the development of a radiophotonic systems for instantaneous microwave frequencies measurement, ever higher requirements are placed on their range, accuracy, and resolution, which can only be satisfied by the creation of a new devices and operating principles. Three types of analysis of frequency components after modulation are possible: analysis of each component separately (differential analysis), analysis of the envelope of each two-frequency pair (integral-derivative analysis), and analysis of all components (integral analysis). All these methods are realizable and correspond to one-, two-, and polyharmonic FBG probing using a limited number of optical band-pass filters. Based on the results of a comparative analysis, it was shown that the problem of the resolution increase of the instantaneous frequency measurement of microwave signals in symmetrical circuits on selective elements can be solved by transferring the frequency components of the measured signal to the middle of the linear section of the FBG; using radiophotonic multiplication and using polyharmonic transformation of the measured frequency on TAPM. Among the advantages of such solutions, the possibility of the resolution increase of the frequency measurement of microwave signals lies in low frequencies measurement in the linear section of the FBG when transferring the frequency components of the measured signal, a multiple decrease in the measurement error by a factor equal to the number of multiplication stages for radiophotonic multiplication and a multiple of the number of harmonics used for the method of polyharmonic transformation.

A Simple Radiophotonic Device for Instantaneous Frequency Measurement of Multiple Microwave Signals Based on a Symmetrical Unequal Comb Generator

A Simple Radiophotonic Device for Instantaneous Frequency Measurement of Multiple Microwave Signals Based on a Symmetrical Unequal Comb Generator

Application of slow-light engineered chalcogenide and silicon photonic crystal waveguides for double-dimensional microwave frequency identification

Four-wave mixing effect was utilized within short dispersion-engineered slow-light silicon and AMTIR1 chalcogenide photonic crystal waveguides with group velocities of c/33 and c/23, respectively, for simultaneous measurement of frequency and power level of an RF tone over a frequency range of 0.01–80 GHz. In our numerical simulations, we considered the impact of various nonlinear phenomena that affected the system outputs. An FWM conversion efficiency of approximately − 45 dB was achieved for a 10 mW continuous-wave pump and probe in an 80 µm AMTIR1 PhC waveguide. In our system, two orthogonal and independent outputs were generated simultaneously. These independent outputs were achieved using a microwave photonics Hilbert transformer implemented using the transversal filtering approach. Since the process was inherently incoherent, the nonlinearity of the four-wave mixing did not affect the resulting signals orthogonality. The ability to simultaneously identify both the RF frequency and the power level of a microwave signal would make this system a perfect candidate for various applications, such as instantaneous frequency measurement receivers.

Wideband High-Speed and High-Accuracy Instantaneous Frequency Measurement System

A new photonic-assisted instantaneous frequency measurement system is presented. It overcomes the latency problem in the reported structures based on the frequency-to-time mapping technique or the frequency-to-power mapping technique that involves a long length of fiber, and at the same time, enables the incoming microwave signal frequency to be measured over a wide frequency range with only small errors. The system generates three low-frequency signals. The phases of the three low-frequency signals are compared. One of the two low-frequency signal phase differences is used to estimate the incoming microwave signal frequency unambiguously over a wide frequency range and the other is used to provide accurate microwave signal frequency measurement. A proof-of-concept experiment is set up. Experimental results show, by measuring the phase difference of two low-frequency signals, the frequency of the input microwave signal can be determined unambiguously in 15 GHz and 500 MHz frequency ranges with errors below ±220 MHz and ±10 MHz respectively. Hence, by using two low-frequency signal phase differences, the input microwave signal frequency can be determined accurately over a wide frequency range. The new photonic-assisted frequency measurement system has a fast response time, which is an order of magnitude shorter than that of the systems based on the frequency-to-time mapping technique and the frequency-to-power mapping technique with a kilometer-long fiber.

Instantaneous Frequency Measurement Using Photonics-Assisted Broadband Signal Generation and Processing

A photonics-based instantaneous microwave frequency measurement with broadband signal generation and processing is proposed and demonstrated. In this scheme, a broadband triangular linear frequency-modulated (LFM) signal is first optically generated, and photonic mixing of the LFM signal with a signal under test (SUT) is implemented before extracting the frequency information in the oscilloscope. In the experiment, both accurate single-frequency and multifrequency measurements are successfully realized using low-speed electronic devices. The experimental results confirm a measurement accuracy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&lt;$</tex-math> </inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 50 MHz within a frequency range from 1 to 39 GHz.

Ultra-wideband instantaneous frequency measurement based on differential photonic time-stretch

A novel technique to perform ultra-wideband instantaneous frequency measurement in real-time based on differential photonic time-stretch is proposed and experimentally demonstrated. Wideband frequency measurement is enabled by time-stretching the RF input signal via the dispersion compensating fiber. Distortion of the measured frequency signal caused by the non-uniformity of the spectrum of the pulsed laser source, which can be found in most of traditional time-stretch systems, is eliminated here by implementing a dual-output Mach–Zehnder modulator (DOMZM) with complementary outputs and a balanced photodetector. Multi-tone tests with a 20 GHz frequency measurement range are conducted to verify the feasibility of the system of measuring multiple frequency signals. Followed by the proposed automated digital signal processing algorithms, our instantaneous frequency measurement system offers an ultra-fast sweep time of 10 ns, a frequency resolution of 660 MHz, and a measurement error within ±380 MHz. A larger frequency measurement range can be realized by implementing a DOMZM with a larger bandwidth.

Microwave Photonic Reconfigurable High Precision Instantaneous Frequency Measurement System Assisted by Stacking Ensemble Learning Method

This paper reports a microwave photonic reconfigurable high precision simple instantaneous frequency measurement system. With the first assistance of stacking ensemble learning method, it can achieve high measurement accuracy over a wide bandwidth. For introducing electrical and optical delays, the range and accuracy of the instantaneous frequency measurement method can be flexibly adjusted to suit the needs of various scenarios. Sufficient and systematic experimental results show that from 11 GHz to 17 GHz, the average measurement error is 4.39 MHz. This simple system acquits reconfigurability and on-chip integration possibilities without dispersion elements, which reveals great potential in the future integrated array radar, detection, and other fields.

Broadband tunable instantaneous frequency measurement system based on stimulated Brillouin scattering

Broadband tunable instantaneous frequency measurement system based on stimulated Brillouin scattering

An Efficient Digital Channelized Receiver for Low SNR and Wideband Chirp Signals Detection

Synthetic aperture radar (SAR) is essential for obtaining intelligence in modern information warfare. Wideband chirp signals with a low signal-to-noise ratio (SNR) are widely used in SAR. Intercepting low-SNR wideband chirp signals is of great significance for anti-SAR reconnaissance. Digital channelization technology is an effective means to intercept wideband signals. The existing digital channelization methods have the following problems: the contradiction of reception blind zone and signal spectrum aliasing, high computational complexity, and low estimating accuracy for chirp signals with a low SNR. This paper proposes a non-critical sampling digital channelized receiver architecture to intercept chirp signals. The receiver architecture has no blind zone in channel division and no aliasing of signal spectrum in the channel, which can provide reliable instantaneous frequency measurements. An adaptive threshold generation algorithm is proposed to detect signals without prior information. In addition, an improved instantaneous frequency measurement (IFM) algorithm is proposed, improving low SNR chirp signals’ frequency estimation accuracy. Moreover, a simple channel arbitration logic is proposed to complete the cross-channel combination of wideband signals. Simulations show that the proposed receiver architecture is reliable and robust for low SNR and wideband chirp signal detection. When the input SNR is 0 dB, the absolute frequency root-mean-square error (RMSE) of bandwidth and the center frequency is 0.57 MHz and 1.05 MHz, respectively. This frequency accuracy is great for radio frequency (RF) wideband systems.

Instantaneous photonic frequency measurement based on compressive sensing

Frequency measurement of microwave signal in a wide band range is a very important task in electronic warfare. In this paper, an instantaneous photonic frequency measurement approach based on chromatic dispersion and compressive sensing is proposed. More than two chromatic dispersion related optical power outputs are used for frequency measurement. The relationship between power ratio and frequency is nonlinear and least square matching is not an optimal solution. Compressive sensing is used for better frequency measurement. The dictionary of compressive sensing is constructed using empirical data, the vector of optical power ratios is used as the target vector, and frequency measurement is achieved by compressed observation. In the experiment, it is found that most frequency measurement errors of the proposed system are quite small, but some errors are quite large. Except about 8% frequencies with extremely large or small power ratios, frequency measurement error within ±0.09 GHz in the frequency range of 6∼30 GHz is achieved by the proposed optical system, which is much better than least square matching.

Photonics-Based Instantaneous Microwave Frequency Measurement System With Improved Resolution and Robust Performance

This paper presents a photonics-based instantaneous microwave frequency measurement system. The system operates based on the frequency-to-power mapping technique. The trade-off between frequency measurement range and resolution, which is present in the reported frequency-to-power-mapping based frequency measurement systems, is addressed by designing the system to produce two amplitude comparison functions (ACFs). Using two ACFs enables an RF signal frequency in a specified range to be determined while having an improved resolution and smaller errors compared to using only one ACF for frequency measurement. The proposed frequency measurement system is designed to have a simple structure and robust performance suitable for use in real world applications. The effect of the higher order sidebands and harmonics on the system performance are investigated. Proof-of-concept experiments are carried out with results showing frequency measurement errors can be reduced by using the proposed system that generates two ACFs for frequency measurement.

Microwave frequency measurement based on a frequency-to-phase mapping technique.

A new frequency-to-phase mapping technique for measuring a radio-frequency (RF) signal frequency is presented. The concept is based on generating two low-frequency signals where their phase difference is dependent on the input RF signal frequency. Hence, the input RF signal frequency can be determined by using a low-cost low-frequency electronic phase detector to measure the phase difference between the two low-frequency signals. The technique can measure the frequency of an RF signal instantaneously and has a wide frequency measurement range. The proposed frequency-to-phase-mapping-based instantaneous frequency measurement system is experimentally verified over the 5 to 20 GHz frequency measurement range with errors of less than ±0.2 GHz.