Frequency Sweep Range Research Articles

Investigation of dynamic response characteristics of light fixed-wing aircraft

In order to ensure the stability of light fixed-wing aircraft during flight missions, considering the effects of relative airflow velocity and angle of attack, the distribution characteristics of velocity and pressure fields under different conditions, as well as the law of change of dynamic parameters, were derived by using aerodynamic methods. In the free modal condition, the modal truncation method was used to simulate and analyze the low-order modal shapes. Based on the modal analysis results, the sweep frequency range was set to 3-50 Hz, with a step size of 1.6 Hz, for a total of 30 substeps. A harmonic load of 1500 N was applied to the fuselage, and the displacement-frequency response curves and stress-frequency response curves of the fuselage structure and wing structure were extracted after the calculation. The results shows that the maximum lift-drag ratio occurs when the angle of attack is 6°, and the peak displacement deformation of the aircraft occurred around 24 Hz.

Metamaterial Microwave Sensor for Glucose Level Measurement Based on Strip Line with Complementary Split Ring Resonator

This research focuses on investigating glucose meters utilizing metamaterial microwave sensors. The metamaterial microwave sensor is designed with a strip line loaded with a complementary split ring. The sensor is designed to conduct Ansys high‐frequency structure simulator and uses conductor material coated on a hydrocarbon ceramic laminate (Roger RO4232) substrate, with a sweep frequency range of 1–6 GHz. The signal of the metamaterial microwave sensor depends on the change in glucose permittivity and conductivity when the glucose concentration changes. The research involves designing a simulation model to explore the impact of complementary split ring size on the sensor's response to changes in glucose permittivity. Additionally, experiments are conducted using the proposed sensor to measure glucose concentration in solution, aiming to analyze trends in sensor response to varying concentrations of glucose and evaluate its sensitivity to changes in glucose concentration. The experimental results indicate that the metamaterial microwave sensor is able to respond to variations in glucose level, a sensitivity of the proposed sensor is 0.0345 dB (mg dL−1)−1 in range of 0–110 mg dL−1 with R2 0.9628.

Optical frequency domain reflectometry with broadened frequency sweep range assisted by a dual electro-optic frequency comb.

We propose an optical frequency domain reflectometry (OFDR) with the assistance of a dual electro-optic frequency comb (EOFC), which is intended to improve the system spatial resolution. As the spatial resolution of an OFDR system is inversely proportional to the frequency sweep range, the EOFC acts as a multi-frequency light source for collecting Rayleigh backscattering signals, which are combined to extend the effective frequency sweep range. By utilizing this technique, we have successfully expanded the experimental frequency sweep range to hundreds of gigahertz, achieving a sub-millimeter spatial resolution.

Ranging disambiguation of LiDAR using chirped amplitude-modulated phase-shift method.

Ranging ambiguity is the major challenge in most LiDAR techniques with amplitude modulation, which limits the performance of range detection due to the tradeoff between the ranging precision and the unambiguous range. Here we propose a novel disambiguation method using a laser with chirped amplitude modulation (sweeping modulation frequency), which can in theory infinitely expand the unambiguous range and completely solve the ranging ambiguation problem. The usage of the earlier proposed Chirped Amplitude-Modulated Phase-Shift (CAMPS) technique enables us to detect the phase-shift of chirped signals with high precision. Incorporating this technique with the proposed disambiguation method, the absolute distance well beyond the conventional unambiguous range can easily be found with merely <1% frequency sweep range. When certain conditions are met, the Non-Mechanical Spectrally Scanned LiDAR (NMSL) system employing the CAMPS method and the Dispersion-Tuned Swept Laser (DTSL) can also realize disambiguation in non-mechanical line-scanning measurement.

Parameter Optimization for Modulation-Enhanced External Cavity Resonant Frequency in Fiber Fault Detection

Fiber fault detection is crucial for maintaining the quality of optical communication, especially in well-established optical access networks with extended distances and a growing number of subscribers. However, the increasing insertion loss in fiber links presents challenges for traditional fault-detection methods in capturing fault echoes. To overcome these limitations, we propose a modulation-enhanced external-cavity-resonant-frequency method that utilizes a laser for fault echo reception, providing improved sensitivity compared to traditional photodetector-based methods. Our previous work focused on analyzing key parameters, such as sensitivity and spatial resolution, but did not consider practical aspects of selecting optimal modulation parameters. In this study, we develop a model based on Lang–Kobayashi rate equations for current-modulated optical feedback lasers and validate it through experimental investigations. Our findings reveal that optimal detection performance is achieved with a modulation depth of 0.048, a frequency sweeping range of 0.6 times the laser relaxation oscillation frequency, and a frequency sweeping step of 0.1 times the external cavity resonant frequency.

Unloaded quality factor optimization of substrate integrated waveguide resonator using genetic algorithm

&lt;p&gt;The main objective purpose of this paper is to study the enhancement techniques of the unloaded quality factor of substrate integrated waveguide (SIW) resonator, given that the quality of filters depends first on the quality of the resonators that compose it. Performance enhancement is achieved by employing a MATLAB-based genetic algorithm to optimize the geometrical parameters of the SIW resonator by iterative convergence to the target frequency (10 GHz frequency). On the other hand, the Ansys HFSS tool is used to model and optimize the SIW resonator with the suitable transition and plot the S-parameters for a frequency sweep range to validate its property. The results obtained allow increasing the unloaded Q-factor to be more than 1609 and reducing not only insertion and return losses but also reducing the size of the resonator. The proposed SIW resonator with its small size and low loss is directly useful for microwave and millimeter-wave applications.&lt;/p&gt;

Absolute distance measurement using frequency sweeping interferometry with large swept range and target drift compensation

Frequency sweeping interferometry (FSI) is an attractive absolute distance measurement (ADM) method because of the advantages of large unambiguity range, simple structure and excellent flexibility. By using a reference interferometer (RI), the calibration of the frequency sweeping range in FSI can be avoided, and the complexity and cost of the system can be further reduced. Then, the measurement accuracy is associated with the accuracy of phase demodulation, the range of frequency sweeping and the compensation of target drift. In this paper, ADM using FSI with large swept range and target drift compensation is presented. A frequency stabilized HeNe laser that travels along the same optical path with the swept source laser was employed to monitor the target drifts of the measurement interferometer and RI. Interference phases of the corresponding interferometers were extracted simultaneously using phase generated carrier demodulation technique, and an accuracy better than 1° was verified by nanometer displacement measurement. Comparative experiments of ADM at a distance of ∼4.5 m with different swept ranges before and after target drift compensation were carried out, and the results demonstrated that larger swept range and target drift compensation could greatly improve the stability and accuracy of measurement.

Admittance-Based Stability Analysis of Current-Controlled VSG Considering the Frequency Coupling Characteristics

Due to the dynamic interaction between the inverter and the grid, the inverter may have power oscillation problems under a weak grid. In this article, considering frequency coupling, the more precise broadband sequence admittance model of the current-controlled virtual synchronous generator (CVSG) is established, and the admittance characteristics of CVSG and traditional grid-connected inverter (TGCI) are compared and analyzed. The amplitude of the sequence admittance of CVSG is generally larger than that of TGCI in the low-frequency region, and in the entire frequency sweep range, the coupling admittance amplitude of CVSG is larger than that of TGCI. In the low-frequency region, the coupling admittance has a great impact on the stability of CVSG and TGCI, so the coupling admittance cannot be neglected when analyzing the stability of the system. The generalized Nyquist stability criterion is used to compare and analyze the influence of power grid strength, phase-locked loop (PLL) bandwidth, and output power on the stability of CVSG and TGCI according to the established admittance model. It can be seen from the stability analysis results that, compared with TGCI, when the PLL bandwidth is relatively large, CVSG has stronger adaptability to the weak grid and power changes. Finally, experiments verify the correctness of the theoretical analysis.

Real-Time Mode Following Based Narrow Linewidth Brillouin Fiber Swept Laser

We propose and demonstrate a novel concept of Brillouin fiber swept laser with narrow linewidth based on mode following effect. Utilizing the synergy of the Brillouin gain spectrum and cavity mode, the real-time mode following effect is achieved. In the experiment, a tunable laser source was employed to realize synchronous tuning of Brillouin gain spectrum for matching the shift of cavity mode induced by an intra-cavity piezoelectric transducer wound with gain fiber. We theoretically analyzed the influence of the driving parameters and wound fiber length on the frequency sweep range. Experimental results show that the obtained maximum continuous frequency sweep range is ∼445.76 MHz while the driving frequency is 12 kHz and the wound fiber length is 12 m, which is consistent with the theoretical analysis. This new type of fiber swept laser has huge potential application value in optical sensing and communication system.

Upper Sweeping Frequency Selection for Cable Defect Location Based on STFT

A frequency domain reflection (FDR) method has been widely used to locate cable defects. Generally, the performance of the FDR method can be enhanced by extending the sweeping frequency range of the signal. However, with the increase in the signal frequency, misdiagnosis can easily occur owing to the attenuation of the signal and noise. Thus, this paper’s authors propose the upper sweeping frequency (UF) selection method of FDR to improve the accuracy of cable defect location. First, the cable’s three-dimensional location spectrum, including the frequency and spatial information, is obtained at a wide frequency range based on short-time Fourier transform with excellent time-frequency aggregation characteristics. Second, the reasonable UF is selected through the energy change characteristics of the cable end. Then, the optimal localization result of the cable defect is calculated by interpolating the sum of energy among the effective frequency bands. Finally, two single-and multi-defect cases are used for the YJV-8.7/10kV XLPE power cable in the experiment to demonstrate the performance of the proposed method. The experimental results show that with the UF selection method, the impact of high-frequency signal attenuation on defect location is eliminated, and cable defect can be localized with more accuracy.

Effect of electrode design and dust particle size on electrodynamics dust shield procedure

In order to reduce water consumption (especially in remote areas) for the self-cleaning dust removal systems, the efficiency of a three-phase traveling electromagnetics wave for some designed Electrodynamics Dust Shield (EDS) setups are simulated and also experimentally tested. The designed Fresnel rings electrodes EDS system showed about 25% enhancement on light collecting power and a substantial improvement on dust removal efficiency, as well. On the other hand, for the fabricated EDS systems the dust removal efficiency has been tested as a function of the dust particle size, respectively. In this study, the removal dust particles has been sampled from three different Iran's desserts with a vast size ranges, which matches with many of the remote areas in the world. It was confirmed that the sweeping frequency range from 5 to 100 Hz improved the cleaning efficiency and also the sweeping time lasting reduced about half for the zigzag electrode EDS system in comparison to a simple parallel bar one. For designing the different EDS systems, the well-known Finite Element calculation method (COMSOL Multiphysics software) has been employed, respectively.

Effect of hyaluronic acid on milk properties: Rheology, protein stability, acid and rennet gelation properties

Hyaluronic acid (HA) is gaining popularity and acceptance as a food ingredient. HA has certain properties such as water binding, viscosity manipulation which can be exploited in food products. However, there are limited studies available for the effect of HA on the properties of food, especially in milk and milk products. Studying the effect of HA treatments on milk properties such as viscosity, heat stability, phase separation, rennet, and acid gelation would be beneficial to the processors. The objective was to study the effect of HA at different concentrations on various physico-chemical properties of milk. Whole milk treated with HA showed increased viscosity as a function of HA concentration in both cold and pasteurized milk samples. The frequency sweep results indicated that only a higher HA concentration (0.5%) was able to achieve the viscoelastic solid behavior (G′ > G″), which was stable over the entire frequency sweep range of 10–150 rad/s. Heat stability of skim milk was negatively impacted as a function of HA concentration. The gravimetric protein phase separation during skim milk storage was also negatively impacted as a function of HA concentrations up to 0.25%. However, higher HA concentration (0.5%) reduced the phase separation. In the case of rennet gel and acid gel studies, the gelation properties and the gel structure was negatively impacted as a function of HA concentration. The negative effect of HA on rennet and acid gelation properties could be as a result of depletion–flocculation mechanism leading to micro-phase separation interference by HA polymer in the formation of continuous protein gel network.

Interrelating Grain Hardness Index of Wheat with Physicochemical and Structural Properties of Starch Extracted Therefrom.

To investigate the physicochemical, structural, and rheological characteristics of starch from wheat cultivars varying in grain hardness index employed in making jiuqu and to interrelate grain hardness index with physicochemical and structural properties of starch. Starch extracted therefrom was investigated for structural and physicochemical properties. Starch granules showed relatively wide granule size distribution; large size granules showed lenticular shapes while medium and small size granules exhibited spherical or irregular shapes. Starch from wheat with a lower grain hardness index exhibited a relatively higher degree of crystallinity. Chain-length profiles of amylopectin showed distinct differences; among the fractions of fa, fb1, fb2, and fb3 representing the weight-based chain-length proportions in amylopectin, the fa fractions ranged from 19.7% to 21.6%, the fb1 fractions ranged from 44.4% to 45.6%, the fb2 fractions ranged from 16.2% to 17.0%, and the fb3 fractions ranged from 16.1% to 18.8%, respectively. To, Tp, Tc, and ∆H of starch ranged from 57.8 to 59.7 °C, 61.9 to 64.2 °C, 67.4 to 69.8 °C, and 11.9 to 12.7 J/g, respectively. Peak viscosity, hot pasting viscosity, cool pasting viscosity, breakdown, and setback of starch ranged from 127 to 221 RVU, 77 to 106 RVU, 217 to 324 RVU, 44 to 116 RVU, and 137 to 218 RVU, respectively. Both G’ and G” increased in the frequency range of 0.628 to 125.6 rad/s; the wheat starch gels were more solid-like during the whole range of frequency sweep.

Method of Coaxial Accelerations Correlation for Quality Assessment of Structural Joints

Assessment of the stiffness of joints is important for the joints’ design, monitoring the condition of building structures and prognosis of the lifetime and safety of buildings or its elements. Typically, such assessment is done in a non-destructive way using either shock or vibration analysis with a network of accelerometers as sensors. To improve the quality of diagnostics of structural joints and make it more specific, a method and measurement system implementing the principle of correlation of normalized coaxial accelerations measured in 3D space was proposed. The method is based on the mathematical analysis of vibrations of structural joints in 3 spatial directions using 3D accelerometers located at different parts of a joint and orientated coaxially. The correlation method was verified in a laboratory experiment using rigid, semi-rigid and pinned joints of timber beams. Stand with timber beams joined at right angles by steel plates and screws were fabricated and tested by static loading to confirm the present state of the joint. Timber beams with 150X50 mm solid sections made C18 strength class were used for the timber stand. The decrease of the joint’s stiffness in the case of probable damages was modelled by the loosening of the steel screws. The stand was subjected to a vibration load provided by electrodynamics actuators fixed on one of the joint elements. This element was excited by a chirp signal in a frequency sweep range from 10 to 500 Hz, where the most prominent resonance of the stand was found. Acceleration responses were recorded by 3D accelerators placed on the loaded and connected beams. Peak values of the cross-correlation function between the responses from the correspondingly orientated pairs of coaxial accelerometers were determined. It was shown that the difference between the peak values of the correlation functions obtained for the rigid, semi-rigid and hinge joints enabled specification of the joints’ stiffness.

Harmonic response analysis of an impeller of a gas turbine engine which modelled by using high entropy alloy materials

One of the problems in a gas turbine’s impeller design is to predict the frequency-stress response caused by the harmonic force resulted from the unbalanced mass. To avoid from impeller’s flaws that may occur, designers must essentially determine the stress conditions of machinery parts under high-speed rotations. The present research explores, for the first time, the effects of modelling with high entropy alloy materials for an impeller of a gas turbine engine on harmonic responses. In order to conduct harmonic analysis, a finite element model established for an impeller of gas turbine engine by using commercial Ansys finite element package. In the finite element model, the impeller and its shaft modelled by using solid elements and beam elements, respectively. The influence of materials having different high entropy alloys on stress responses is examined for an impeller of a gas turbine engine. The results show that the highest stress exists in AlCoCrFeNi high entropy alloy material for along the sweep frequency range. In addition, the highest stress-percentage ratio is in CoCrFeNi high entropy alloy material for first resonance frequencies. Also, computations illustrate the minimum stress-percentage ratio is in AlCoCrFeMo0.1Ni high entropy alloy material for first resonance frequencies. Another finding is that the maximum percentage ratio is in CoCrFeNi high entropy alloy material for second resonance frequencies. Furthermore, the lowest percentage ratio is detected in AlCoCrFeMo0.1Ni high entropy alloy material for second resonance frequencies.

Rapid-scan electron paramagnetic resonance using an EPR-on-a-Chip sensor.

Electron paramagnetic resonance (EPR) spectroscopy is the method of choice to investigate and quantify paramagnetic species in many scientific fields, including materials science and the life sciences. Common EPR spectrometers use electromagnets and microwave (MW) resonators, limiting their application to dedicated lab environments. Here, novel aspects of voltage-controlled oscillator (VCO)-based EPR-on-a-Chip (EPRoC) detectors are discussed, which have recently gained interest in the EPR community. More specifically, it is demonstrated that with a VCO-based EPRoC detector, the amplitude-sensitive mode of detection can be used to perform very fast rapid-scan EPR experiments with a comparatively simple experimental setup to improve sensitivity compared to the continuous-wave regime. In place of a MW resonator, VCO-based EPRoC detectors use an array of injection-locked VCOs, each incorporating a miniaturized planar coil as a combined microwave source and detector. A striking advantage of the VCO-based approach is the possibility of replacing the conventionally used magnetic field sweeps with frequency sweeps with very high agility and near-constant sensitivity. Here, proof-of-concept rapid-scan EPR (RS-EPRoC) experiments are performed by sweeping the frequency of the EPRoC VCO array with up to 400 THz s, corresponding to a field sweep rate of 14 kT s. The resulting time-domain RS-EPRoC signals of a micrometer-scale BDPA sample can be transformed into the corresponding absorption EPR signals with high precision. Considering currently available technology, the frequency sweep range may be extended to 320 MHz, indicating that RS-EPRoC shows great promise for future sensitivity enhancements in the rapid-scan regime.

Voltage standing wave ratio reading circuit design for inductance capacitance wireless passive ammonia sensors.

It is not easy to conduct wired tests on sensors in harsh environments, and network analyzers are large, heavy, and inconvenient to carry. At the same time, the price of network analyzers is usually very high, which greatly limits their application. In this study, a voltage standing wave ratio reading circuit is designed to test inductively coupled (LC) wireless passive sensors. By introducing the theory of the standing wave ratio, the design concept and function of each module are analyzed from each specific module. The resonant frequency reading circuit of the sensor is designed and fabricated, and its sweep frequency range covers the frequency range of the commonly used LC wireless sensor, which widens the bandwidth measurement range. The main control chip adopts STM32 series, which makes the circuit and sensor module simple in structure and low in cost. This circuit can accurately obtain the resonant frequency of the sensor through the standing wave ratio and can measure the dynamic change in the sensor standing wave ratio. The output frequency range and output precision of the linear sweep source of the signal reading circuit were tested, and the dynamic testing ability of the circuit to the changing frequency was verified and improved the measurement accuracy.

A Liquid-Metal-Based Freestanding Triboelectric Generator for Low-Frequency and Multidirectional Vibration

There are a lot of vibrational energies, which are low frequency, multidirectional, and broadband, in the nature. This creates difficulties for devices that aim at harvesting vibration energy. Here, we present a liquid-metal-based freestanding triboelectric generator (LM-FTG) for vibration energy harvesting. In this device, the fluidity of liquid is used to increase sensitivity to vibration for better low-frequency response and multidirectional vibration energy harvesting capability. The freestanding power generation mode is able to increase power generation stability. Experiments show that the bandwidth of LM-FTG can almost cover the entire sweep frequency range, and a 10 μF capacitor can be charged to 6.46 V at 7.5 Hz in 60 s by LM-FTG. In particular, 100 LEDs are illuminated in the low-frequency environmental experiment successfully. The proposed LM-FTG can work in low frequency with large working bandwidth, which provides an effective method for energy harvesting of low-frequency and multidirectional vibrations.

Smart needle to diagnose metastatic lymph node using electrical impedance spectroscopy

ObjectivesThe cause of cervical lymphadenopathy varies from inflammation to malignancy. Accurate and prompt diagnosis is crucial as delayed detection of malignant lymph node can lead to a worse prognosis. To improve the diagnostic accuracy of metastatic lymph node, electrical spectroscopy was employed to study human normal and metastatic lymph nodes using a hypodermic needle with fine interdigitated electrodes on its tip (EoN). Subjects and MethodsThe electrical impedance of samples collected from 8 patients were analyzed in the sweeping frequency range from 1 Hz to 1 MHz. To align the impedance level data of the patients, normalized impedance was employed. ResultsThe optimal frequency exhibiting the best discrimination results between the normal and cancerous tissues was introduced based on a discrimination index. A high sensitivity (86.2%) and specificity (88.9%) were obtained, which implied that the EoN holds the potential to improve the in vivo diagnostic accuracy of metastatic lymph node during biopsy and surgery. ConclusionEoN has a promising potential to be utilized in real-time in actual clinical trials without a need for any pre/post-treatment during FNA or surgery. We believe that the EoN could reduce unnecessary operations with its associated morbidity.

Optimization of Wide-Field ODMR Measurements Using Fluorescent Nanodiamonds to Improve Temperature Determination Accuracy.

Fluorescent nanodiamonds containing nitrogen-vacancy centers have attracted attention as nanoprobes for temperature measurements in microenvironments, potentially enabling the measurement of intracellular temperature distributions and temporal changes. However, to date, the time resolution and accuracy of the temperature determinations using fluorescent nanodiamonds have been insufficient for wide-field fluorescence imaging. Here, we describe a method for highly accurate wide-field temperature imaging using fluorescent nanodiamonds for optically detected magnetic resonance (ODMR) measurements. We performed a Monte Carlo simulation to determine the optimal frequency sweep range for ODMR temperature determination. We then applied this sweep range to fluorescent nanodiamonds. As a result, the temperature determination accuracies were improved by a factor ~1.5. Our result paves the way for the contribution of quantum sensors to cell biology for understanding, for example, differentiation in multicellular systems.