Minimum Frequency Shift Research Articles

A novel trident shaped microstrip antenna sensor for glucose detection in human blood

A novel trident-shaped microstrip patch antenna sensor with great sensitivity is developed to estimate the amounts of glucose in blood samples of human. The suggested sensor is built on a 30 × 24 × 1.6 mm3 FR-4 substrate layer with a quality factor of 64 and a dielectric constant value of 4.3 resonating at 4.5 GHz. A finger phantom is the replica of the human finger and it is originated in the electromagnetic simulator in order to forecast the glucose content. By positioning the phantom replica at various localities on the constructed antenna sensor, the frequency shifts are observed for various levels of glucose concentration in different degrees, ranging from 0 to 1000 mg/dL are detected. The proposed sensor can identify diabetic conditions in patients as it has a finger phantom positioned parallel to the feed at the top of the antenna giving a 156 MHz paramount shift in frequency, sensitivity of 156 kHz/(mg/dL), and a minimum frequency shift of 24 MHz and sensitivity of 24 kHz/(mg/dL). To confirm the suggested sensor's functionality in a real-time environment, its performance is examined for various actual human finger postures, and the resulting resonance frequencies are observed. In order to detect the levels of glucose concentration, the suggested sensor's error performance is calculated and are found to be near to 1%.

The KERATO Biomechanics Study 1: A Comparative Evaluation Using Brillouin Microscopy and Dynamic Scheimpflug Imaging.

To assess the corneal biomechanical properties in normal individuals and patients with keratoconus using the Brillouin optical scanning system (Intelon Optics) (BOSS) and compare them with ultra-high-speed Scheimpflug imaging (Corvis ST; Oculus Optikgeräte GmbH). Sixty eyes from 60 patients (30 normal and 30 keratoconus) were included in this prospective, single-center, comparative, non-interventional study. Corneal biomechanics were evaluated using the Corvis ST and the BOSS. With the BOSS, each corneal image was acquired three times, measuring 10 locations within an 8-mm diameter. Parameters extracted included mean, maximum, and minimum Brillouin shift. These 10 points were also grouped into superior, central, and inferior regions. BOSS repeatability was assessed using the coefficient of repeatability and coefficient of variation. Furthermore, normal individuals and patients with keratoconus were compared using the Corvis ST and BOSS. The BOSS exhibited good repeatability, with coefficient of repeatability ranging from 0.098 to 0.138 GHz for single points in normal individuals and 0.096 to 0.149 GHz for patients with keratoconus. Statistical analysis revealed significant differences between normal individuals and patients with keratoconus, indicating softer corneas in keratoconus, observed with both the Corvis ST and BOSS. Specifically, the BOSS showed significant differences in mean, inferior, and superior mean, maximum, and minimum Brillouin frequency shift (all P < .05), whereas the Corvis ST displayed highly significant differences in stiffness parameter at first applanation, stress strain index, deformation amplitude ratio, and inverse integrated radius (all P < .001). Corneal biomechanical measurements proved highly repeatable and effectively demonstrated significant differences between normal individuals and patients with keratoconus using both the BOSS and the Corvis ST. [J Refract Surg. 2024;40(8):e569-e578.].

STRUCTURE FEATURES OF MINIMUM FREQUENCY SHIFT KEYING SIGNAL MODEMS

The article discusses specific features of constructing modems for minimum frequency shift keying signals using various schemes with high noise immunity levels. An analysis of the formation of these signals and frequency modulation signals, which are orthogonal if enhanced, is provided, including quantitative indicators and comparative characteristics. Two schemes of minimum frequency shift keying signal demodulators (coherent and autocorrelation) are examined, including their comparative features. Operation principles of these demodulator circuits with the use of timing diagrams are described, requirements for the reference oscillator generators included in coherent demodulators are formulated, as well as the requirements for minimum frequency shift keying signals, which ensure the greatest noise immunity in autocorrelation demodulators of minimum frequency shift keying signals with binary signals quantization.

High-resolution spectroscopy of liquid water with dispersive atomic vapor prism cell

This article presents an experimental demonstration of a spectroscopic method based on the dispersion of the scattering spectrum from laser-illuminated liquid water collected through a rubidium atomic vapor prism cell. Resonant absorption at 780 nm suppresses Mie/Rayleigh scattering and the steep gradients in refractive index near the 780 nm absorption lines separate Brillouin scattering from Raman scattering in liquid water. The opposing spatial displacements of the Stokes and Anti-Stokes shifted Brillouin peaks yield a measurement of their spectral shifts and thus the temperature or salinity of the water. Performance of the prism cell was mapped with a frequency tunable laser for frequency offsets from the center of the rubidium absorption feature of between −15 GHz and 15 GHz and at rubidium cell temperatures between 148 °C and 177 °C. The experimental results are compared with a numerical model and show good agreement with the scattering peak displacements within experimental uncertainties of probe frequency and cell temperature. In the present configuration, the minimum detectable frequency shift is estimated to be 15.5 MHz. Experiments were conducted in water demonstrating the utility of this method for the measurement of water temperature. Liquid water LiDAR was suggested as one of the possible applications for this method and several ways to improve the experimental setup and cell temperature stability were identified.

A BLE 5.0 Extended Advertising Backscatter with Commodity Devices in Passive IoT Scenarios

BLE-based (Bluetooth Low Energy-based) backscatter has received considerable attention, as it aims to communicate with everyday smart devices such as smartphones, smartwatches, and tablets in passive IoT. The state-of-the-art BLE backscatter systems enable communication using a specialized continuous wave (CW) generator or entirely using commodity BLE 4.0 radios as an RF source. However, the existing BLE communication systems suffer from several key issues, including a short carrier length and a large frequency shift. This paper presents a passive BLE (PBLE) backscatter communication system that utilizes commodity BLE 5.0 radios. The system uses a BLE 5.0 extended advertising packet with partial single tones as excitations transmitting on the secondary advertising channel of BLE 5.0, and the BLE backscatter tag produces bandpass frequency-shift keying modulation at 1 Mb/s, which enables compatibility with BLE advertising channels. The prototype is implemented using an NRF52832 BLE 5.0 commodity chip, smart devices, and tags with FPGAS and chips. In FPGA board-level verification, when the downlink distance is 0.5 m, the uplink distance can reach 10 m. In chip testing, the uplink distance can reach 7 m when the downlink distance is 1 m. The baseband power consumption is 2 μW, with a total power consumption of 10 μW. This system eliminates the need for expensive and costly specialized RF sources, unlike the BLE backscatter communication system that uses a specialized CW generator. Compared to the BLE backscatter communication system that uses commodity BLE 4.0 radios, this system reduces the minimum frequency shift from 24 MHz to 2 MHz and increases the length of the single tones as a CW by a factor of about seven, from 31 bytes to 254 bytes.

Designing Audible Safety with Acoustic Vehicle Alerting System for Commercial Vehicles

Abstract: Electric and hybrid vehicles, known for their environmental benefits, also present a unique challenge because of their quiet operation. In urban settings, this lack of noise increases the potential for accidents with pedestrians who rely heavily on auditory cues. In response to this concern, Acoustic Vehicle Alerting Systems (AVAS) have been introduced and many countries, including the US and EU, have mandated the installation of Acoustic Vehicle Alerting Systems. These systems produce sounds to alert pedestrians of an approaching vehicle by increasing the audibility of electric and hybrid vehicles to ensure pedestrian safety [1]. In this paper, we dive deep into designing an effective AVAS for commercial vehicles, such as trucks and buses. Any AVAS must conform the international regulations such as the ECE-R138 regulation by the United Nations Economic Commission for Europe (UNECE) and FMVSS 141 by the National Highway Traffic Safety Administration (NHTSA), so our design adheres to guidelines set by key global bodies. This endeavour was supported by The Scientific and Technological Research Council of Türkiye. Our AVAS not only offers a variety of sound options but also includes self-diagnostic features to ensure its consistent performance. An integral part of our study was the utilization of an ASIL-B functional safety-compliant embedded MCU system to generate and manipulate psychoacoustic sounds. The regulations regarding the acoustic characteristics of AVAS sounds, such as minimum sound level, frequency spectrum, and frequency shift, have been instrumental in improving awareness of the AVAS sounds of quiet vehicles[2]. The ultimate aim is to showcase a versatile, compliant, and efficient AVAS, beneficial for the future landscape of electric and hybrid commercial vehicles

Design of alert sound for electric vehicle based on fluctuation strength for amplitude fluctuation

The motor sound of an electric vehicle is quiet at low speeds. Thus, it is difficult for pedestrians to detect vehicles approaching them. This is not only a particular problem for visually impaired people but also for any people who cannot see the approaching vehicle, for example, in a situation where the vehicle comes from behind or an obstacle object. Therefore, the vehicle was designed to provide an alert sound to solve this problem. The UN Regulation No.138 on Quiet Road Transport Vehicles was adopted and published in 2016. The regulation introduces a minimum sound level, spectrum, and frequency shift depending on the speed of the vehicle. However, the regulation of the amplitude fluctuation has not been defined. In this study, it is assumed that pedestrians are aware of approaching gasoline vehicles by hearing the amplitude fluctuations in the exhaust sound. We propose that they can be aware of approaching EV by hearing amplitude fluctuation sounds. Our previous studies found that fluctuation frequency, non-periodic fluctuation, and amplitude envelope influence the sensation of hearing fluctuation or fluctuation strength. Their effects on pedestrian detectability were assessed in an actual environment. The results indicate that these characteristics are effective in detecting approaching vehicles.

Digital modems of minimum frequency shift keying signals and their characteristics

Background. The need to describe the features of the formation of minimum frequency shift keying signals, reveal the advantages of this type of modulation, provide circuits for digital demodulators of minimum frequency shift keying signals that provide the best reception noise immunity, and indicate ways to improve the spectral efficiency of minimum frequency shift keying signal modems. Aim. Various options for constructing digital modems for minimum frequency shift keying signals, features of modem circuits for even and odd numbers of half-periods on segments of the duration of transmitted messages, as well as the specifics of the formation of reference oscillations in coherent demodulators are considered. Methods. The principle of operation of modulators and demodulators of minimum frequency shift keying signals is explained by the timing diagrams of signals at various points in the paths for the formation and detection of minimum frequency shift keying signals. This representation ensures the reliability and clarity of the operation of modems of minimum frequency shift keying signals. Results. It is shown that coherent demodulators of minimum frequency shift keying signals provide the same noise immunity as opposite signals of relative phase shift keying, but at the same time they have a constant signal level and a smaller spectrum width. A dual-channel minimum frequency shift keying signal modem doubles the spectral efficiency of a single-channel modem, but the signal level becomes inconsistent. Conclusion. Information is given explaining the reason for the widespread use of minimum frequency shift keying signals in cellular communication systems, in space communication systems and in cordless phones, as well as ways to further improve digital modems of minimum frequency shift keying signals.

Measurement of Complex Permittivity for Rapid Detection of Liquid Concentration Using a Reusable Octagon-Shaped Resonator Sensor

Substrate-integrated waveguides (SIWs) are widely used in microwave systems owing to their low cost and ease of integration. In this study, an SIW-based resonator that reacts to the complex permittivity variation of solutions with dimensions of 79.2 mm × 59.8 mm is introduced. This octagon-shaped sensor can be installed on a preliminary monitoring system to test water quality by observing the parameter variations caused by external factors. The resonant structure was used to test different concentrations of ethanol-water and acetone-water mixtures for verification. The resonant frequency and quality factor (Q-factor) were found to vary with the relative complex permittivity of the liquid in the S-band, and the electric field distribution varied when liquid droplets were placed in the center of the substrate. The designed sensor operates at 2.45 GHz in the air, and the observed minimum resonant frequency shift with liquid was 15 MHz. The measurement error was approximately 3.1%, and the results reveal a relationship between the resonant frequency and temperature as well. Considering the observed sources of error, the measured relative permittivity is consistent with the actual values. The proposed sensor is economically convenient and suitable for various test environments.

GMSK Demodulation Combining 1D‐CNN and Bi‐LSTM Network Over Strong Solar Wind Turbulence Channel

AbstractTo solve the problem of bit error rate (BER) performance degradation over strong solar wind turbulence channel, this paper addresses to Gaussian minimum frequency shift keying (GMSK) demodulation using machine learning. First, by analyzing the scintillation characteristics of the telemetry signal caused by solar wind turbulence during the solar superior conjunction, the K distribution channel model is innovatively established over strong solar wind turbulence channel. Then, the approximate probability density function of the K distribution of the established channel is studied by using Laguerre orthogonal polynomial for convenience. Additionally, the BER performance of GMSK over strong solar wind turbulence channel is analyzed. Second, using a one‐dimensional convolutional neural network (1D‐CNN) and bidirectional long short‐term memory network (Bi‐LSTM), two demodulators for GMSK are proposed. By integrating the 1D‐CNN and LSTM to extract local features and process the dynamic information of GMSK signals, we propose a novel GMSK demodulator over strong solar wind turbulence channel with combining 1D‐CNN and Bi‐LSTM. The simulation results show that, even if the solar wind turbulence has serious effects on the signal at a low signal‐to‐noise ratio, the proposed combining neural network demodulation can obtain better BER performance than the classical Viterbi algorithm, demodulation using only a single 1D‐CNN or Bi‐LSTM. The proposed GMSK demodulator is more suitable for the deep space exploration of the solar system.

Highly sensitive metamaterial-based microwave sensor for the application of milk and dairy products.

In this work, a novel, to the best of our knowledge, metamaterial-based microwave sensor is designed, numerically simulated, and experimentally tested for milk and dairy products in the frequency range of 8 to 9 GHz. The proposed structure is composed of copper split-ring resonators printed on Arlon Diclad 527 dielectric substrate. Reflection coefficient S11 was determined by using numerical simulation, and the structure was experimentally tested to validate the sensor at the X band frequency. The material under the test was placed in the sensor layer just behind the proposed structure, and the design was optimized to sense the change in the dielectric constant via resonance frequency shifts. The proposed study was not only used for fat contents and freshness checking of milk, it was also applied to other dairy products such as cheese, ayran, and yogurt. The maximum resonance frequency shift was observed in yogurt to be 140 MHz, and the minimum frequency shift was observed in fresh and spoiled ayran to be around 40 MHz. This work provides a new approach to the current metamaterial sensor studies existing in literature by having novel material applications with new microwave metamaterial sensors.

Algorithms for the Encoding and Reception of OFDM Signals Based on Manipulation with Minimum Frequency Shift

The developed algorithms for the encoding and reception of OFDM signals using minimum frequency shift keying (OFDM-MSK signals) are considered and investigated. OFDM-MSK signals have low out-of-band power compared to OFDM signals using phase shift keying. It is shown that the developed algorithms for the encoding and reception use a lattice structure of signals with a continuous phase with a minimum frequency shift in combination with a productive algorithm for fast spectral transformation in the Fourier basis.

Bottom-tracking: the possibilities and physical meaning of keeping the bottom of the frequency shift in atomic force microscopy

In ultrahigh vacuum atomic force microscopy, the frequency of an oscillator holding the scanning tip takes a typical Lennard–Jones like curve with a local minima just before contact. We demonstrate here the application of a control scheme to keep this local minima, or the bottom of the frequency shift curve (FC) as the working point for imaging in UHV, and discuss its physical meaning and possible applications. Tip-sample distance modulation and Lock-in detection were used to obtain the gradient of the FC, where null control of the gradient signal resulted in implementing the designated control. Atomic resolution was confirmed for Si(111) and solder. The histogram of minimum frequency shift on the apex of atomic features on solder showed two to four peaks, implying the ability of the method to map characteristic differences of the depth of the FC per site. The method is an alternative to the existing constant-frequency-shift mode and constant-height mode, with the possibility to access chemical information on-the-fly.

Fabrication and characterization of thin-film silicon resonators on 10 m-thick polyimide substrates

MEMS fabricated on polymer substrates can allow for a range of new applications that require bending or lightweight, unbreakable substrates. The surface micromachining of hydrogenated amorphous silicon resonators on 10 µm-thick flexible polyimide substrates is presented. Clamped-clamped (bridges) and clamped-free (cantilevers) resonators are fabricated and characterized, exhibiting quality factors as high as 2.0 × 103 and natural resonance frequencies in the 104–106 Hz range. The deflection of an 80 µm long bridge was measured to be over 100 pm, using laser Doppler vibrometry. The electrical addressing of the devices was demonstrated to be reliable when bent to radii of curvature larger than 10 mm. The resonators on ultra-thin polymer are characterized using different actuation voltages and pressures, showing comparable performance to resonators on rigid (glass) substrates. However, the flexible substrate allows the relaxation of the residual stress of the structural film in clamped-clamped structures, lowering the resonance frequency. Resonators on PI were found to be suitable for mass-sensing applications, achieving a minimum frequency shift detectable Δfmin = 30 Hz which results in a calculated mass sensitivity of 25 pg in vacuum. Ultimately, the reliable performance of the resonators developed in this work make them good candidates for applications that require mass-sensing on ultra-thin, flexible substrates.

Miniature Sensing System With FBAR-Based Oscillators and Frequency Shift Detector

This paper describes a highly sensitive sensing system for remote sensing applications. Typically, a resonant sensor based on film bulk acoustic resonator (FBAR) requires a frequency counter, impedance analyzer, or network analyzer to measure the shift of the resonant frequency. This paper presents a hand-held, low-cost but highly sensitive sensing system built with an FBAR-based oscillator and a phase-locked-loop for ppm-level detection of frequency shift as well as signal processing. The achieved voltage-frequency sensitivity is 1.035 V/kHz with the minimum detectable frequency shift of 4.81 ppm (5.21 kHz) and the dynamic range of 134 ppm (145 kHz). Also, the output of the sensing system is purposely designed to be a DC voltage that is linearly related to the frequency shift. To our knowledge, it is the first FBAR-based sensing system that converts the frequency shift to DC voltage.

A Graphical Method for LTE-A System and Digital Broadcasting Interoperability Studies

The co-primary basis operation between long term evolution-advanced (LTE-A) and current digital television (TV) receiver systems is a significant issue when working in cochannel or adjacent channel in the 800 MHz. This policy aims to efficient use of frequency spectrum, but leads to an intersystem interference phenomenon, which may disturb the Interoperability between LTE-A and digital TV receiver. In this paper, we propose an effective, simple and graphical approach based on the operating band unwanted emission technique to evaluate all possible intersystem interference scenarios. A variety of practical and substantial spectrum sharing elements that can seriously influence the coexistence situation of LTE-A and TV receiver have been studied. The findings show that co-channel sharing scenario will have much more coexistence difficulty for macro (urban/suburban/rural) areas without employing some interference mitigation techniques. However, in order to make the two systems interoperate in adjacent channel situation, the minimum frequency shift should be at least half of the interferer system bandwidth without mitigation technique. Additionally, the wider channel bandwidth of LTE-A system is preferable more than narrower bandwidth for peaceful compatibility, which helps to support high data rate for LTE-A system.

Microbead-assisted high resolution microwave planar ring resonator for organic-vapor sensing

A microbead-assisted planar microwave resonator for organic vapor sensing applications is presented. The core of this sensor is a planar microstrip split-ring resonator, integrated with an active feedback loop to enhance the initial quality factor from 200 to ∼1 M at an operational resonance frequency of 1.42 GHz. Two different types of microbeads, beaded activated carbon (BAC) and polymer based (V503) beads, are investigated in non-contact mode for use as gas adsorbents in the gas sensing device. 2-Butoxyethanol (BE) is used in various concentrations as the target gas, and the transmitted power (S21) of the two port resonator is measured. The two main microwave parameters of resonance frequency and quality factor are extracted from S21 since these parameters are less susceptible to environmental and instrumental noise than the amplitude. Measured results demonstrate a minimum resonance frequency shift of 10 kHz for a 35 ppm concentration of BE exposure to carbon beads and 160 kHz for the polymer based adsorbent at the same concentration. The quality factor of the resonator also changed for different concentrations, but a distinguishable variation is observed for the BAC adsorbents. The high quality factor of the sensor provides the opportunity of real time monitoring of the adsorbent behaviors in remote sensing mode with very high resolution.

Study of field shifts of Ramsey resonances on ultracold atoms and ions

The effect of the finite laser radiation line width and spontaneous relaxation of levels on the efficiency of the suppression of the field shift of the central resonance for the generalized Ramsey scheme with pulses of different lengths and with a phase jump in the second pulse has been considered. The optimal parameters of the scheme corresponding to the minimum frequency shift and maximum amplitude of the resonance have been determined.

Tuning the resonant frequency of resonators using molecular surface self-assembly approach.

In this work, a new method to tune the resonant frequency of microfabricated resonator using molecular layer-by-layer (LbL) self-assembly approach is demonstrated. By simply controlling the polymer concentration and the number of layers deposited, precisely tuning the frequency of microfabricated resonators is realized. Due to its selective deposition through specific molecular recognitions, such technique avoids the high-cost and complex steps of conventional semiconductor fabrications and is able to tune individual diced device. Briefly, film bulk acoustic resonator (FBAR) is used to demonstrate the tuning process and two types of LbL deposition methods are compared. The film thickness and morphology have been characterized by UV-vis reflection spectra, ellipsometer and AFM. As a result, the maximum resonant frequency shift of FBAR reaches more than 20 MHz, meaning 1.4% tunability at least. The minimum frequency shift is nearly 10 kHZ per bilayer, indicating 7 ppm tuning resolution. Pressure cooker test (PCT) is performed to evaluate the reliability of LbL coated FBAR. Furthermore, applications for wireless broadband communication and chemical sensors of LbL coated FBAR have been demonstrated.

Performance evaluation of MSK and OFDM modulations for future GNSS signals

The objective of this work is to investigate the performances of orthogonal frequency division multiplexing (OFDM) and minimum frequency shift keying (MSK) modulations as potential future global navigation satellite systems (GNSS) signal modulation schemes. MSK is used in global system for mobile communications because of its spectral efficiency, while OFDM is used in WLAN and digital video broadcast-terrestrial because of its multipath mitigation capability. These advantages of MSK and OFDM modulations render them as promising modulation candidates for future GNSS signals to offer enhanced performances in challenging environments. Gabor bandwidth and multipath error envelopes of these two modulations were computed and compared with those of the current global positioning system (GPS), Galileo, and Beidou signal modulations. The results show that OFDM modulation demonstrated promises as a viable future GNSS modulation, especially for signals that require pre-filtering bandwidths larger than 2 MHz, while MSK modulation is more desirable for pre-filtering bandwidth below 2 MHz where it exhibits the largest Gabor bandwidth.