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Group delay processing of audio signals has been extensively studied in the last decade. In this paper, tonic estimation in Turkish makam music is addressed using modified group delay processing. Tonic is one of the stable pitches of the performance, which serves as the reference throughout the performance. The proposed methodology does not require metadata such as the melodic pitch values of the audio files for tonic estimation. Modified group delay functions (MODGD) computed from the flattened music spectrum of non-melodic segments are bin-wise summed to form a summary-modgdgram. The peak position in the tonic range of summary-modgdgram is mapped to the tonic pitch. Two corpora of the Turkish music tonic dataset, created by the CompMusic project group, are used to assess the system. The proposed methodology outperforms the baseline last note detection (LND) method, which uses pitch contour as a prerequisite for tonic estimation. The results show the potential of processing audio signals using the phase-based approach in tonic pitch estimation. [ABSTRACT FROM AUTHOR]

This study proposed an interdigital band-pass filter based on the microstrip transmission line. When designing a conventional structure for an interdigital filter based on the characteristics of the 5th order transmission line, seven resonators are required. By changing the impedance of the resonator adjacent to the feed line, the proposed interdigital band-pass filter was designed to reduce the number of resonators compared to conventional interdigital band-pass filters. Consequently, the resonator order decreased, and return and insertion losses become comparable to that in case of a conventional interdigital filter design. The proposed band-pass filter was designed with a center frequency of 2.75 GHz and a bandwidth of 1.5 GHz. Furthermore, based on various transmission characteristics such as group delay and coupling coefficient, two band-pass filters were designed, compared, and analyzed. [ABSTRACT FROM AUTHOR]

This research investigates the characterization of bituminous mixes utilizing microwave imaging and non-destructive testing. We studied the electromagnetic characteristics of various samples, including bituminous concrete (BC) and open-grade friction course (OGFC) samples. A novel ring filter with log-periodic feedlines, designed on the RT/Duroid 5880 substrate, was utilized within the frequency range of 0.3–0.7 GHz. The samples were assessed using average attenuation and group delay measures, which detailed clear electromagnetic characteristics. The samples' flow value and specific gravity were correlated to these parameters. The calculated flow value and specific gravity (using the filter) and measured flow value and specific gravity (using the conventional method) coincided well. The filter could predict the parameters of the samples with a high accuracy of roughly 99.8% for the flow value and specific gravity, whereas the OGFC sample displayed an accuracy of 99.7%, correspondingly, as shown in high R2 values. This demonstrates that the filter can precisely measure the parameters required for studying the interaction between the binder and aggregate in bituminous mixes without being invasive. The findings indicate a significant disparity between OGFC and BC samples in their responses to electromagnetic fields and their characteristics. This demonstrates the high sensitivity and significant value of microwave techniques in the study of bitumen and the construction of roadways. [ABSTRACT FROM AUTHOR]

This paper presents a detailed design of a broadband power amplifier (PA) utilizing 0.18-μm CMOS technology, operating in the frequency range of 2–5 GHz. This ultra-wideband (UWB) power amplifier uses a cascode topology with current reuse to enhance gain over the desired frequency band, utilizing an inductive source degenerate design to achieve the best linearity and output power and gain while maintaining a wide bandwidth. The inductive source degenerate adopts bondwire and microstrip line design. The paper includes extensive analysis, simulation results, and measurements to verify the performance of the amplifier and demonstrate its suitability for broadband power amplifier applications. The measured results for the proposed UWB power amplifier show excellent performance, with an impressive third-order input intercept point (IIP3) ranging from 15 to 18.7 dBm over the frequency range of 2–5 GHz. The output third-order intercept point (OIP3) ranges from 33 to 35 dBm. Additionally, the gain flatness is specified as 12.5 ± 1.5 dB. The reverse isolation is greater than or equal to − 40 dBm. The PA has a P1dB output power (OP1dB) of 10.2 dBm at 3 GHz, 9.2 dBm at 4 GHz, and 9.2 dBm at 5 GHz, respectively. The PA has a P1dB power-added efficiency of 30.5% at 3 GHz, 23% at 4 GHz, and 22% at 5 GHz with a 50 Ω load termination. The power dissipation is 33.3 mW at a supply voltage of 1.8 V. In addition, the PA has an excellent small group delay variation of ± 65 ps. The chip area is 1.01 × 1.08 mm2, including the pads. The proposed UWB PA demonstrates exceptional linearity, efficiency, and group delay in the 2–5 GHz frequency band. [ABSTRACT FROM AUTHOR]

This paper introduces a Koch fractal octagonal antenna designed for the Ultrawideband (UWB) Frequency range. The utilization of the Koch fractal in the antenna design contributes to size reduction as well as provides compactness in the antenna for UWB. Additionally, it has been noted that the Koch fractal offers wideband operation. The antenna employs copper as the conductor material, and Flame Retardant-4 (FR4) serves as the substrate. The substrate has a dielectric constant ϵr=4.4, a loss tangent tanδ=0.02, and a thickness (h) of 1.6 mm. The overall antenna's dimensions are 34.3 × 26.5 × 1.6 or electrical dimensions represent as 0.68λ0 × 0.53λ0 × 0.032λ0 . It achieves a maximum gain of 8.94 dBi at a frequency of 12.25 GHz, offering a broad bandwidth ranging from 2 GHz to 12.1 GHz.This antenna exhibits resonance at three distinct frequencies, namely 3.3 GHz, 6 GHz, and 8.6 GHz, making it highly efficient with an overall efficiency of 96.8%. The time domain characteristic is acceptable for UWB, group delay is 1.1 ns, the The proposed antenna has a high-fidelity factor of 90.2, and the correlation coefficient is 0.9. which makes the antenna a good candidate for UWB. Due to its performance characteristics, this proposed antenna is well suited for short-range wireless personal area networks (WPANs), supporting high-data-rate applications like Bluetooth and wireless USB and Wireless Body Area Network (WBAN) applications. Its proficiency also extends to industrial settings, where it helps with precision in control systems, asset tracking, and short-range sensing and radar systems. [JJCIT 2024; 10(1.000): 58-73]

This study introduces a novel microstrip design methodology for an ultra-compact bandpass filtering coupler, emphasizing a systematic approach to its development. The coupler is accurately designed, optimized, fabricated, and measured, achieving a small layout area of 0.003 λg2, excluding feeding ports. The design process begins with a comprehensive mathematical analysis of a fundamental microstrip layout, followed by simultaneous optimization techniques that enhance performance characteristics. Electromagnetic simulations and measurements are conducted to validate the design, revealing an excellent correlation between the two and confirming precise performance metrics. The coupler demonstrates a filtering response with a suppressed 3rd harmonic and exhibits S21 and S31 values of −3.135 dB and −3.103 dB, respectively, indicating low insertion losses and balanced output magnitudes. Its isolation factor exceeds −19.5 dB across the frequency range from DC up to 1.875 GHz, making it particularly suitable for 5G applications. Additionally, the coupler features flat channels with minimal group delays, with S21 and S31 showing the maximum group delays close to 0.8 ns. Our design methodology not only integrates these advantages but also sets a new benchmark for compact bandpass filtering couplers, delivering exceptional performance within a remarkably constrained footprint.

We analyze the two classic methods for chirped Integrated Bragg Gratings (IBGs) in Silicon-on-Insulator technology using the transfer matrix method based on the effective refractive index (neff) technique, which translates the geometry of an IBG into a matrix of neff depending on the wavelength. We also implement a procedure that allows engineering of the chirped IBG parameters, given a required bandwidth (BW) and group delay (GD). Finally, a complementary method for designing chirped IBG is proposed, showing a significant improvement in the bandwidth of the device or a moderation in the variation of the geometrical parameters of the grating. [ABSTRACT FROM AUTHOR]

Summary: The paper discusses about the design and analysis of a unique circular printed antenna with quatrefoil‐shaped slots and meta‐surface for body centric communications. The antenna design is progressed with a slots in quatrefoil shape carved on the patch placed on Taconic_LX substrate whose thickness is 1 mm. The footprint of the antenna is 32 × 24 × 1 mm3. The antenna's bandwidth is improved using defected ground. The proposed design operates from 2 to 14 GHz of the ultra‐wideband (UWB) spectrum, thus providing 143% bandwidth. The antenna exhibits good gain values of 2.5 and 6 dB at 2.45 and 5.8 GHz, respectively, with efficiency of 81% and 91%. At 2.45 GHz, the design proposed functions in on‐body mode, and at 5.8 GHz, it functions in off‐body mode. Specific absorption rate (SAR) analysis was carried out whose results are within the safety range of health measures. Bending analysis was also done to enhance the antenna's applicability. Path loss, fidelity, and group delay analysis are done. The simulated results were validated by fabricating and testing the prototype. On‐body testing of the fabricated antenna was also done at various body locations. The measured results were found to be in good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

This article presents the design of a novel sigma slotted circular monopole antenna for wireless body area network applications. The design is proceeded with a sigma-shaped slot etched on the circular radiator with Rogers 4003C substrate. The size of the proposed antenna is 30 × 30 × 1 mm 3. With partial ground plane, the bandwidth characteristics of the antenna have been enhanced. The designed antenna covers 2–10 GHz of the ultra wideband, thereby providing more than 106% bandwidth. The antenna exhibits high gain values of 1.95, 3.23, 3.46, and 5.95 dB at 2.45, 3.45, 5.8, and 9.5 GHz, respectively. The proposed design operates on off-body mode at 2.45 GHz and on-body mode at 5.8 GHz, thus acting as a dual-mode antenna. To ensure the health and safety measure, specific absorption rate analysis was done for both low and high values of input power and also with Cartesian and cylindrical human arm models. Bending analysis was also done. The time domain parameter group delay was also analyzed for the proposed antenna for on- and off-body scenarios. The prototype was fabricated, and validation of simulation results was done for free space and on-body scenarios. [ABSTRACT FROM AUTHOR]

The generation of second-order sidebands and its associated group delay is an important subject in optical storage and switch. In this work, the efficiency of second-order sideband generation in a coupled optomechanical cavity system with a cubic nonlinear harmonic oscillator is theoretically investigated. It is found that the efficiency of second-order sideband generation can be effectively enhanced with the decrease in decay rate of optomechanical cavity, the increase in coupling strength between two cavities and the power of probe field. The slow light effect (i.e., positive group delay) is also observed in the proposed optomechanical cavity system, and can be controlled with the power of control field. [ABSTRACT FROM AUTHOR]

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Time-frequency analysis (TFA) can provide relevant information about subsurface reservoirs, which is essential in reservoir identification. Traditional TFA methods are limited by resolution, resulting in unreliable seismic interpretation. The time-reassigned synchrosqueezing transform (TSST) is a practical TFA approach for processing non-stationary signals. However, for a frequency-domain signal with a strong-varying group delay (GD), the TSST provides a blurred time-frequency representation (TFR). We propose a novel TFA method called high-order TSST (HTSST) to address this problem. First, to describe the signal with GD variations, we develop a frequency domain signal model. Next, the high-order partial derivative of the short-time Fourier transform (STFT) is obtained based on the high-order Taylor expansion of the signal, and a matrix determinant is constructed according to the results. The matrix determinant is then used to deduce an explicit GD estimation formula in the time-frequency domain. Finally, the high-resolution TFR of the HTSST is generated by squeezing the energy to the estimated GD. With a strong-varying GD, frequency-domain signals can thus benefit from a high-resolution TFR provided by HTSST. Numerical simulations are performed to investigate this method’s efficiency. Through the analysis of seismic field data, the efficacy of this method for tight sandstone gas reservoir identification is verified.

The ionospheric delay effect is inevitable when a radio signal propagates through the ionosphere. It has been extensively studied in the L-band. Typically, the influence of the ionosphere on the code phase and carrier phase is regarded as the same. In this study, a numerical ratio between the group delay time and phase advance time with reference to the study of the L-band is investigated in the short-wave band. The variation in the numerical ratio with frequency, critical frequency, and elevation angle is discussed in detail. There appears an interesting phenomenon wherein the elevation angle has a greater effect on the ratio than the frequency and critical frequency. The numerical ratio increases with an increasing elevation angle. On the other hand, a regression analysis is used to establish the mapping relation between the ratio and the three factors of frequency, critical frequency, and elevation angle, based on the simulation results obtained by a ray-tracing algorithm. The little relative errors between the fitted values and simulation values under different ionospheric models prove the relationship between the ratio and the three factors of frequency, critical frequency, and elevation angle. [ABSTRACT FROM AUTHOR]

This paper investigates the dispersive properties of a spectral filter—a quarter-wave (QW) mirror. The study considers the modeling with a smoothly changing refractive index of the applied material (Rugate filter) using Fourier transform analysis of a high and low refractive index. These chirped structures exhibit high reflectivity and low group delay dispersion. The introduced result in this study is in some way better than already existing ones and/or can be used to obtain a meaningful practical effect, because it adopts calculation methods that are characterized by the accuracy and reliability of data using different statistical parameters and can be adopted with all modern and old methods of preparation. These improvements can have significant implications for various applications. Moreover, we investigate different statistical parameters, such as mean, median, mode, and standard deviation (STD), and analyze their impact on the rugate filter group delay (GD) and group delay dispersion (GDD) performance. [ABSTRACT FROM AUTHOR]

This paper describes design, theoretical analysis, and experimental evaluation of a π-Phase-Shifted Fiber Bragg Grating (π-PSFBG) inscribed in the standard telecom fiber for slow light generation. At first, the grating was designed for its use in the reflection mode with a central wavelength of 1552 nm and a pass band width of less than 100 pm. The impact of fabrication imperfections was experimentally investigated and compared to model predictions. The optical spectra obtained experimentally show that the spectral region used for slow light generation is narrower (less than 10 pm), thus allowing for too-low levels of slow light optical-output power. In the next step, the optimization of the grating design was conducted to account for fabrication errors, to improve the grating's spectral behavior and its temporal performance, and to widen the spectral interval for slow light generation in the grating's transmission mode. The targeted central wavelength was 1553 nm. The π-PSFBG was then commercially fabricated, and the achieved parameters were experimentally investigated. For the region of (1551–1554) nm, a 15-fold increase in the grating's pass band width was achieved. We have shown that a pair of retarded optical pulses were generated. The measured group delay was found to be ~10.5 ps (compared to 19 ps predicted by the model). The π-PSFBG operating in its transmission mode has the potential to operate as tunable delay line for applications in RF photonics, ultra-fast signal processing, and optical communications, where tunable high precision delay lines are highly desirable. The π-PSFBG can be designed and used for the generation of variable group delays from tens to hundreds of ps, depending on application needs. [ABSTRACT FROM AUTHOR]

In this paper, a study on the effects of strategically implemented holes in a miniaturized wideband bandpass filter (BPF) utilizing interdigital folded coupled lines is presented. First, the BPF is designed to produce the passband by introducing a fold in the coupled lines. The passband is centered at 9.3 GHz (X‐band), catering to radar applications. Coupled lines connected to a modified U‐shaped transmission line comprise the filter's design configuration. The novelty of the design resides in incorporating drilled holes along the coupled lines, which generate perturbations and resonant effects, resulting in enhanced impedance variations and improved filter performance. With the aid of electromagnetic analysis and simulation software, the coupled lines, U‐shaped transmission lines, and drilled hole diameters are all optimized. Vector Network Analyzer performs all the measurements and draws the comparisons. An increment of 22.58% is seen in return loss as it increases from −24 to −32 dB, and the insertion loss shows an increase of 16.74%. The proposed filter has been subjected to analytical study, simulation, and implementation, which have confirmed its exceptional return loss, favorable insertion loss, and compact dimensions. The research results make a valuable contribution to the development of miniaturized wideband BPFs, specifically focusing on their use in radar systems. In such systems, the ability to accurately and efficiently filter signals is paramount. The design insights and performance improvements presented in this study have significant implications for broader applications in microwave engineering and communication systems. [ABSTRACT FROM AUTHOR]

In this paper, author has presented design strategies for two core uncoupled heterogeneous multi-core fiber (MCF) to achieve minimum crosstalk. Authors have studied the variation of crosstalk between the cores in respect to the MCF parameters like bending radius, wavelength, core position and fiber length, so that single mode propagation can be made through designed uncoupled heterogeneous cores. The other important performance parameters of MCF i.e. group delay and dispersion have also been discussed in the paper. [ABSTRACT FROM AUTHOR]

This paper reports simple but accurate analytical expressions of group delay and modal dispersion parameters for single-mode graded index fibers over a wide range of V numbers. The formulation employs power series expression for the fundamental modal field of graded index fiber derived by Chebyshev formalism. Choosing some typical step, parabolic and triangular index fibers as examples in our present study, we use the prescribed formulations to estimate group delay and modal dispersion parameters of those fibers both in presence and absence of Kerr nonlinearity. Iterative technique is applied for prediction of concerned propagation parameters in presence of Kerr nonlinearity. Our results show excellent agreement with the numerical exact ones both in absence and presence of Kerr nonlinearity. The exact results in case of Kerr nonlinearity are obtained using cumbersome finite element method. The execution of our accurate formalism involves little computation and is thus user friendly for technologists and researchers working in the field of nonlinear optical engineering. [ABSTRACT FROM AUTHOR]

A novel compact microstrip diplexer based on spiral cells is presented in this paper. The proposed resonator primarily consists of two spiral thin lines connected to a pair of coupled lines. This novel resonator is analyzed mathematically to find its behavior and tune the dimensions of the final layout easily. Using the analyzed resonator, two bandpass filters (BPFs) are designed. Then, a novel high-performance microstrip diplexer is obtained by designing and integrating these BPFs. The proposed diplexer boasts a remarkably small size of 0.004 λg2 and features flat channels with low insertion losses of only 0.048 dB and 0.065 dB. The maximum group delays of S21 and S31 are 0.31 ns and 0.86 ns, respectively, which are good values for modern communication system. Meanwhile, inside its passbands for some frequency ranges its group delays are negative. Thus, using this diplexer can decrease the signal dispersion. The first and second passbands are wide with 47.3% and 47.1% fractional bandwidths, respectively. Therefore, this diplexer can be easily used in designing high-performance radio frequency communication systems. [ABSTRACT FROM AUTHOR]

Tapered profiles are introduced in Bessel and Blackman apodized fiber Bragg grating, and their sensing performance is theoretically estimated. Reflectivity equation of proposed apodized tapered profiles is obtained using transfer matrix method and coupled mode theory. Since the effective refractive index (RI) of proposed waveguides varies with core radius therefore amplitude distribution and penetration depth of light in surroundings are modified. It is found that the exponential tapered profile with Bessel apodization shows a higher sensitivity of 682.5 nm/RIU, detection accuracy of 3858.45, and quality parameter 1718.02/RIU with minimum full width at half maxima (FWHM) 0.3972 nm of the reflection spectra. The spectral response of the tapered fiber Bragg grating is also analyzed through a group delay study. Again, exponential profile was found to be particularly effective, producing less group delay ripples 2.98 ps and is maximum slope of 42.43°. Hence, exponential tapered profile is demonstrated for detection of cancer cells lies between the refractive index of 1.3333–1.4412. [ABSTRACT FROM AUTHOR]

In this paper, a new optimization method for the design of nearly linear-phase two-dimensional infinite impulse (2D IIR) digital filters with a separable denominator is proposed. A design framework for 2D IIR digital filters is formulated as a nonlinear constrained optimization problem where the group delay deviation in the passband is minimized under prescribed soft magnitude constraints and hard stability requirements. To achieve this goal, sub-level sets of the group delay deviations are utilized to generate a sequence of filters, from which the one with the best performance is selected. The quality of the obtained filter is evaluated using three quality factors, namely, the passband magnitude quality factor Qh and the group delay deviation quality factor Qτ, while the third one is a new quality factor Qs that assesses the performance in the stopband relative to the minimum filter gain in the passband. The proposed framework is implemented using the interior-point (IP) method in a MATLAB environment, and the experimental results show that filters designed using the proposed method have good magnitude response and low group delay deviation. The performance of the resulting filters is compared with the results of other methods.

An autocorrelation technique, which involves the correlation of a signal with its delayed version, could be used to demodulate the FM (Frequency Modulation) and PM (Phase Modulation) signals in a simple cost-effective manner. In this paper, an attempt has been made to understand the working principle of the autocorrelation technique for FM and PM demodulations. From the working principle, several design equations have been derived and these equations have been verified with the experimental results obtained from a 70 MHz autocorrelation-type FM receiver designed and developed indigenously. The demodulation of FM signal directly at RF (radio frequency) level has also been demonstrated using an autocorrelation-type C-band FM receiver at 4180 MHz. [ABSTRACT FROM AUTHOR]

Time-frequency analysis is recognized as a dynamic tool to analyze the nonstationary signal. The synchrosqueezing transform is usually applied as a post-processing method to further improve the readability of the time-frequency representation. Synchrosqueezing transform is related to the reassignment method and can be performed in two directions, namely time direction and frequency direction. Frequency-direction reassignment helps to squeeze the slowly changing ridge. However, the time-direction reassignment is efficient to process the signal with rapid variation in instantaneous frequency. Thus, there exists a conflict in most of the time-frequency analysis methods while dealing with a signal containing both of these two components. In this study, a new method called demodulated time-direction synchrosqueezing transform is introduced, which is not only capable of achieving a higher compact TFR but also allow reconstructing the mode. In order to explain demodulated time-direction synchrosqueezing transform, a signal model is established in frequency domain. Then, a demodulated procedure is implemented to eliminate time-frequency analysis diffusion. Finally, time-direction reassignment is carried out to further enhance the energy concentration of the time-frequency analysis. The proposed demodulated time-direction synchrosqueezing transform method is evaluated by both simulation and experimental research. The results reveal that the performance of demodulated time-direction synchrosqueezing transform is better than the conventional time-frequency analysis methods, and it can be applied to the fault diagnosis in a machine. [ABSTRACT FROM AUTHOR]

The proposed work illustrates the small circular wearable antenna for ultra-wide band (UWB) application. The designed work consists of a circular top patch of 15 mm radius and two square slots of dimensions 6 mm2 at center and 10 mm2 at the top of patch are created. The partial ground plane concept is used to get a wide bandwidth with a dimension of 27 mm × 50 mm. To describe the wearable applications, the light weight jean material is used as a non-conducting dielectric material with the εr of 1.7 and the substrate height of 1 mm. The designed antenna is resonating at the frequency range of 2.27 GHz to 15.18 GHz for ultra-wide band (UWB) applications. Also the bending performance of the proposed antenna is investigated at the radius of 80 mm and the angle of 0˚. The simulated and measured results of S11 parameter of the proposed antenna are below −10 dB for 2–16 GHz UWB frequency range. The group delay of antenna also is calculated and simulated values of group delay vary from 0.0473 ns to 0.4502 ns and measured 0.1217–0.9852 ns for the wide frequency band. The different antenna parameters are analyzed for this frequency band and the designed antenna is validated on VNA of 20 GHz. [ABSTRACT FROM AUTHOR]

This paper presents the design of a novel lowpass–bandpass diplexer with compact size and good performance using microstrip cells. For this purpose, two microstrip lowpass and bandpass filters are separately designed and mathematically analyzed. The proposed microstrip diplexer has a novel and simple structure. It occupies a compact area of 0.037 λ g2 (722 mm2), and its insertion loss and S 11 at both channels are low. The insertion loss at the lower and upper channels is only 0.047 and 0.16 dB, respectively. Meanwhile, both channels are flat with the maximum group delay of 1.68 ns which is the lowest compared to the previously reported diplexers mentioned in this paper. To design the proposed diplexer, first, a lowpass diplexer with good performance is designed which has low losses and a good figure of merit. It has a flat passband with a sharp roll-off. Then, to achieve the proposed diplexer, a bandpass resonator is added to the lowpass filter without any extra matching circuit, which saves the overall size. The proposed diplexer is designed, simulated, and fabricated, where the simulation and measurement results are close. [ABSTRACT FROM AUTHOR]

We analyze the two classic methods for chirped Integrated Bragg Gratings (IBGs) in Silicon-on-Insulator technology using the transfer matrix method based on the effective refractive index (neff) technique, which translates the geometry of an IBG into a matrix of neff depending on the wavelength. We also implement a procedure that allows engineering of the chirped IBG parameters, given a required bandwidth (BW) and group delay (GD). Finally, a complementary method for designing chirped IBG is proposed, showing a significant improvement in the bandwidth of the device or a moderation in the variation of the geometrical parameters of the grating.

The generation of second-order sidebands and its associated group delay is an important subject in optical storage and switch. In this work, the efficiency of second-order sideband generation in a coupled optomechanical cavity system with a cubic nonlinear harmonic oscillator is theoretically investigated. It is found that the efficiency of second-order sideband generation can be effectively enhanced with the decrease in decay rate of optomechanical cavity, the increase in coupling strength between two cavities and the power of probe field. The slow light effect (i.e., positive group delay) is also observed in the proposed optomechanical cavity system, and can be controlled with the power of control field.

The 4 × 4 magneto-optical matrix is theoretically established to investigate the group delays of circular polarization, which are generated by the linearly polarized wave crossing through a sandwich composition that consists of a multi-Weyl semimetal (mWSM) layer and two identical Ag layers. Results denote that the cross-polarized transmission of right hand circularly polarized (RCP) and left hand circularly polarized (LCP) waves experience sharp increases from zero transmission to total transmission at their respective resonant tunneling wavelengths because of the nonzero off-diagonal components of mWSM. Based on the steep change of cross-polarized transmissions, the giant enlarged group delays of several picoseconds can be obtained. Furthermore, the resonant tunneling wavelength of RCP and LCP waves exhibit the dependence on tilt degree of Weyl cones, Fermi energy, Weyl nodes separation and topological charge, which provide feasible strategies to achieve the regulable enhanced group delays. Our findings reveal effective methods to acquire the tunable enlarged group delays of circular polarization with mWSM.

DC electronic current transformer is the data source of the system control and protection device, so its measurement delay has always been concerned. In this paper, the DC current transformer is modelled equivalently and the key factors affecting the delay of shunt and the remote module are analyzed. A field test method for the delay characteristics of the DC electronic current transformer is proposed. Moreover, a complex multi-state large current generator and integrated test system are developed. On the basis of the IEC 60044-8 standard transmission protocol, the accuracy of standard signal acquisition with the shunt is better than 0.2%. The maximum output current of the established testing system is 600 A. Based on the field test in an actual HVDC project, transient step and various frequency signal components are applied for analyzing. [ABSTRACT FROM AUTHOR]

A vital aspect of Indian classical music (ICM) is rāga, which serves as a melodic framework for compositions and improvisations for both traditions of classical music. In this work, we propose a CNN-based sliding window analysis on mel-spectrogram and modgdgram for rāga recognition in Carnatic music. The important contribution of the work is that the proposed method neither requires pitch extraction nor metadata for the estimation of rāga. CNN learns the representation of rāga from the patterns in the mel-spectrogram/modgdgram during training through a sliding-window analysis. We train and test the network on the sliced-mel-spectrogram/modgdgram of the original audio while the final inference is performed on the audio as a whole. The performance is evaluated on 15 rāgas from the CompMusic dataset. Two fusion paradigms, namely multi-channel and multi-modal frameworks, have been implemented to identify the potential of two feature representations. Out of the two approaches, multi-modal architecture reports a macro-F1 measure of 0.72, which is at par with the performance of the baseline sequence classification model. The performance is also compared with that of a transfer learning approach. [ABSTRACT FROM AUTHOR]

In this paper, a high-resolution time–frequency (TF) analysis method, called time-extracting wavelet transform (TEWT), is introduced to analyze impulsive-like signals whose TF ridge curves are nearly perpendicular to the time axis. For impulsive-like signals, the instantaneous frequency with almost infinite rate of change is difficult to estimate, but the group delay (GD) with nearly zero rate of change is easier to estimate. Since the GD is the key feature of frequency-domain signals, it indicates that one can try to understand impulsive-like signals from the perspective of frequency-domain signals. In this regard, for an impulsive signal and its Fourier transform (i.e., the frequency-domain harmonic signal), we propose the TEWT that achieves highly concentrated TF representations while allowing signal reconstruction, only by retaining the TF coefficients closely related to TF features of signals, while removing weakly related TF information. The two contributions of this paper are the proposal of TEWT and the theoretical analysis of TEWT for frequency-domain signals. On the other hand, we provide a rigorous theoretical analysis of TEWT under a mathematical framework for frequency-domain signals. Specifically, we define a function class as a set of all superposition of well-separated frequency-domain harmonic-like functions, where each function can be locally regarded as a sum of a finite number of harmonic signals in the frequency domain, and establish error bounds for WT approximate expression, GD estimation, and component recovery. Finally, we verify the effectiveness of TEWT in terms of the energy concentration, robustness, and invertibility through numerical experiments with synthetic and real signals. [ABSTRACT FROM AUTHOR]

In this study, we develop a rule-based method for the detection of seizures in electroencephalogram (EEG) signals. The proposed method is based on the observations that EEG seizure can be modeled either as a train of impulses or as the summation of harmonically related frequency-modulated chirps. For detecting spike-train-type seizures, the proposed method estimates group delay-based features, whereas to detect seizures modeled as the summation of harmonically related frequency-modulated chirps, the instantaneous frequency-related features are extracted. Experimental results indicate that the proposed method achieves better performance than the machine learning approach in terms of total accuracy and sensitivity. [ABSTRACT FROM AUTHOR]

A compact circular structured monopole antenna for ultrawideband (UWB) and UWB dual-band notch applications is designed and fabricated on an FR4 substrate. The UWB antenna has a hybrid configuration of the circle and three ellipses as the radiating plane and less than a quarter-lowered ground plane. The overall dimensions of the projected antennas are 16 × 11 × 1.6 mm3, having a −10 dB impedance bandwidth of 113% (3.7–13.3 GHz). Further, two frequency band notches were created using two inverted U-shaped slots on the radiator. These slots notch the frequency band from 5–5.6 GHz and 7.3–8.3 GHz, covering IEEE 802.11, Wi-Fi, WLAN, and the entire X-band satellite communication. A comprehensive frequency and time domain analysis is performed to validate the projected antenna design's effectiveness. In addition, a circuit model of the projected antenna design is built, and its performance is evaluated. Furthermore, unlike the traditional technique, which uses the simulated surface current distribution to verify functioning, characteristic mode analysis (CMA) is used to provide deeper insight into distinct modes on the antenna. [ABSTRACT FROM AUTHOR]

A new microstrip triplexer with a compact size of $0.007~\lambda _{\mathrm {g}}^{2}$ is proposed in this work, where designing a microstrip triplexer with a size less than $0.01~\lambda _{\mathrm {g}}^{2}$ is a big challenge. In addition to the compact size, it shows a high performance i.e. its channels are wide with low insertion losses. Moreover, the channels are flat with three low group delays (GDs) of 0.65, 0.95 and 1.17 ns, while most of the previously reported triplexers have not considered this important parameter. The proposed resonator is mathematically analyzed to find a method to get rid of harmonics and tune the resonance frequency. Meanwhile, the $1^{st}$ , $2^{nd}$ , $3^{rd}$ and $4^{th}$ harmonics are suppressed above the first channel. The designed triplexer is suitable for 5G mid-band applications. The proposed triplexer is exactly fabricated and then measured to confirm the designing method and simulation results. The obtained results show that all the simulation, mathematical analysis and experimental results are in good agreement. Therefore, the proposed triplexer can be easily used in designing high-performance RF communication systems.

The main methods for the determination of the object position using code phase and signal carrier phase measurements are given. An accuracy of pseudorange measurements of both carrier phase and group delay code signal depends on local phase center variations for the signals coming from different directions. The relation of group delay and local phase center of the antenna is determined wherein the key factor is frequency dependence of phase or local phase center variation in solid angle of the radiation pattern. The definition of local phase center whose coordinates depends on the direction of radio signal is given. The single helical antenna analysis of local phase center position is carried out considering that the radio technical performances of the navigation antenna’s spacecraft «Glonass» depends on the same ones of its radiating elements. The features and the technique for hodographs computation of the helical radiator’s navigation phased antenna array using electrodynamic simulation tools are considered. The offset estimation of local phase center is obtained. The features of that offset in relation to the radiator construction depending on the operating frequency are detected.

Metasurface‐based spatial phaser, exhibiting dispersive group delay responses, is able to perform real‐time analogue signal processing on the temporal spectrum of spatial electromagnetic waves, e.g., Fourier transformation, pulse chirping, pulse spread, and compression. The functionality of a spatial phaser is closely related to its group delay dispersion slope. For instance, for an up‐chirped incident pulse, the positive‐slope‐dispersion phaser spreads the pulse whereas the negative‐slope‐dispersion one compresses the pulse. Most reported spatial phasers exhibit fixed dispersion slopes and hence perform single functionality only, which cannot meet the demand of multifunctional systems in communication and sensing applications. In this paper, a new way is proposed to control and tune the dispersion slope of spatial phasers using polarization of incident waves, which is simpler and more efficient than conventional approaches based on tunable circuits. To verify the proposed method, a first‐order spatial phaser is designed and experimentally demonstrated within 9.4–10.6 GHz. It is able to generate negative‐slope, positive‐slope, and zero‐slope group delay dispersions, in case of x‐, y‐, and ±45°‐polarized waves. Such a reconfigurable phaser may find wide applications in integrated communication and sensing. [ABSTRACT FROM AUTHOR]

Instantaneous frequency (IF) is commonly used in the analysis of electroencephalogram (EEG) signals to detect oscillatory-type seizures. However, IF cannot be used to analyze seizures that appear as spikes. In this paper, we present a novel method for the automatic estimation of IF and group delay (GD) in order to detect seizures with both spike and oscillatory characteristics. Unlike previous methods that use IF alone, the proposed method utilizes information obtained from localized Rényi entropies (LREs) to generate a binary map that automatically identifies regions requiring a different estimation strategy. The method combines IF estimation algorithms for multicomponent signals with time and frequency support information to improve signal ridge estimation in the time–frequency distribution (TFD). Our experimental results indicate the superiority of the proposed combined IF and GD estimation approach over the IF estimation alone, without requiring any prior knowledge about the input signal. The LRE-based mean squared error and mean absolute error metrics showed improvements of up to 95.70% and 86.79%, respectively, for synthetic signals and up to 46.45% and 36.61% for real-life EEG seizure signals. [ABSTRACT FROM AUTHOR]

This paper proposes a new dual-band difference (DBD) method to retrieve total electron content (TEC) in Martian ionosphere with the dual-band echoes of the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS). It establishes the relationship between the group delay difference of two-band echoes and the plasmas frequency. Then the Martian ionospheric parameters are solved with this equation. Then the TEC is calculated by integrating the vertical distribution model of Mars electron density. This method is used to calculate the TEC of the typical ionosphere in the southern hemisphere of Mars, and the comparison with previous results validates this method. The experiments prove that this method can not only calculate the TEC of dayside and nightside in different periods, but also effectively eliminate the influence of ionospheric dispersion on radar echoes. Moreover, the time variation characteristics of the ionosphere are analyzed. According to the characteristics of this algorithm, the error sources are analyzed. By calculating the influence of different parameters on the results, it is proved that the maximum error of the algorithm is less than 0.1 TECU. [ABSTRACT FROM AUTHOR]

Double Fano resonances in a nanocavity assisted by metallic nanoparticles (MNPs)‐quantum dot (QD) system are demonstrated theoretically. The nanocavity is assumed to couple with the QD and QD is assumed to locate in the plasmon field produced by two excited MNPs nearby. The nanocavity is driven by a control field and a probing field. Double Fano resonances can be manipulated by the system parameters such as frequency detuning and coupling strength among the nanocavity, the mechanical oscillator, MNPs and QD. Especially, we find the second Fano resonance appears due to the interaction between the nanocavity with the QD‐MNPs. We also discuss the transmission and group delay in the double Fano resonance transparency windows which show tunable fast and slow light for different probe frequency. Our results may provide possible applications in designing optical buffer, switching, and so forth. [ABSTRACT FROM AUTHOR]