Insertion Loss Research Articles (Page 1)

This work presents a microstrip band-pass Gysel power divider (GPD) for secure wireless systems, incorporating champion-stage shaped resonators (CSSRs) to achieve strong harmonic suppression, high isolation, and low insertion loss. We use Grey Wolf Optimization (GWO) in a MATLAB↔ADS loop to optimize transmission-line impedances and electrical lengths, comparing GWO with Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) under identical settings. The design constraints include fabrication-feasible bounds for impedance, electrical lengths, and coupling gaps. GWO outperforms PSO and GA in terms of convergence speed and RF metrics, achieving return loss ≈ −21.5 dB, insertion loss ≈ −3.05 dB, and isolation ≈ −23.5 dB at 3.8 GHz. The fabricated prototype shows strong agreement with simulations, confirming the design's potential for miniaturized IoT and secure telecom applications. This work demonstrates GWO as an effective optimization tool for RF/microwave designs within practical fabrication constraints.

Abstract Programmable integrated photonic circuits are poised to drive a new revolution in information systems by synergizing with high-speed digital signals. Central to this vision is the ability to reconfigure optical signal processing for multi-functional photonic integration. Here, we design and experimentally demonstrate a thermo-optically reconfigurable adiabatic coupler monolithically integrated on a silicon photonics platform. The device combines adiabatic directional couplers with titanium nitride (TiN) micro-heaters embedded in the adiabatic transition region, enabling dynamic coupling ratio tuning via the localized thermo-optic modulation. Experimental results confirm continuous coupling ratio adjustment from 50:50 to 70:30 across 80-nm bandwidth (1,520–1,600 nm), with insertion loss kept below 0.25 dB. Leveraging its tunability, the device enables programmable spectral routing with free spectral ranges (FSR) of 20 nm and 40 nm. The proposed approach offers enhanced flexibility and scalability for high-density photonic systems, providing a promising pathway toward next-generation programmable photonic circuits and optical computing architectures.

Reliable wireless communication is a critical enabler of digital transformation in the mining industry, particularly in phosphate and mineral extraction environments, where safety, monitoring, and automation depend on robust connectivity. However, underground and semi-enclosed mining settings introduce severe electromagnetic (EM) challenges, including signal attenuation, multipath fading, and interference from dense equipment and layered geological structures. Traditional substrate engineering methods—such as buried diffused layers (BDL), metallized grids, guard rings, and electromagnetic bandgap (EBG) structures—offer partial isolation but often fail to ensure stable performance in such harsh conditions. This paper proposes the application of a game-theoretic electromagnetic isolation framework to wireless communication systems in mining operations. By modeling isolation techniques as strategic players in a non-cooperative game, the framework derives equilibrium solutions that balance isolation, insertion loss, fabrication complexity, and deployment cost. Simulation studies across the 2–12 GHz band demonstrate that the proposed method achieves 25–30 dB improvements in coupling reduction compared to conventional approaches while maintaining practical scalability. These results highlight the potential of the framework to enable safe, interference-resilient, and efficient wireless connectivity for real-time monitoring, autonomous equipment control, and worker safety systems in phosphate and mineral mining environments.

Backscatter technologies promise to enable large-scale, battery-free sensor networks by modulating and reflecting ambient radio frequency (RF) carriers rather than generating new signals. Translating this potential into practical deployments—such as distributed photovoltaic (PV) power systems—necessitates realistic modeling that accounts for deployment variabilities commonly neglected in idealized analyses, including uncertain hardware insertion loss, non-ideal antenna gain, spatially varying path loss exponents, and fluctuating noise floors. In this work, we develop a practical model for reliable backscatter communications that explicitly incorporates these impairing factors, and we complement the theoretical development with empirical characterization of each contributing term. To validate the model, we implement a frequency-shift keying (FSK)-based backscatter system employing a non-coherent demodulation scheme with adaptive bit-rate matching, and we conduct comprehensive experiments to evaluate communication range and sensitivity to system parameters. Experimental results demonstrate strong agreement with theoretical predictions: the prototype tag consumes 825 µW in measured operation, and an integrated circuit (IC) implementation reduces consumption to 97.8 µW, while measured communication performance corroborates the model’s accuracy under realistic deployment conditions.

We present a nonvolatile, multilevel silicon photonic memory device that integrates a multimode interference (MMI) coupler with a micro-racetrack resonator (MRR) to enable broadband operation and wavelength-division multiplexing (WDM). To enhance light–matter interaction and reduce power consumption, high-index memory materials (BiFeO 3 , Al 2 O 3 ) and an elevated film stack (EFS) structure are employed to embed the resistive random-access memory (ReRAM) layer within the cavity. A transparent ITO electrode improves mode confinement while maintaining electrical conductivity. The MMI design not only provides low insertion loss and high fabrication tolerance but also induces stronger cavity coupling, which shortens the photon lifetime and significantly broadens the resonance linewidth (FWHM in the 1.8–11.7 nm range, corresponding to 0.22–1.47 THz). Together with enlarged free spectral ranges (FSRs) of 9.9–16.9 nm, this MMI-enabled broadening improves memory state distinguishability, channel spacing, and operational stability. Three configurations were characterized under BFO cladding (i.e., ReRAM-integrated devices at 0 V bias): a 50 µm racetrack with an FSR of 16.86 nm and an FWHM of ∼7.9 nm (Lorentzian fit), a 100 µm racetrack with an FSR of 16.40 nm and an FWHM of ∼11.7 nm, and a cascaded 50 µm + 100 µm dual-racetrack filter with an FSR of 9.91 nm and an FWHM of ∼1.8 nm (Lorentzian fit). After integrating with high-index ReRAM layers, all configurations demonstrated tunable resonance shifts and robust broadband operation; notably, the 100 µm racetrack provided the widest linewidth (∼11.7 nm, corresponding to ∼1.47 THz). Under 0 V operation , logic states L1 and L2, compared to the initial state, exhibited wavelength shifts of 4.72 nm and 5.49 nm, with extinction ratios of 6.44 dB (77.3%) and 8.73 dB (86.6%), respectively, confirming the nonvolatile, multistate capability. Overall, this CMOS-compatible architecture offers broadband, scalable memory functionality with THz-level static optical bandwidth inferred from the FWHM, indicating strong potential for high-data-rate operation. This work opens opportunities for optical storage, logic circuits, and neuromorphic computing, and shows promising potential for future implementation in reconfigurable photonic systems.

This work presents an experimental investigation into a novel microwave band-pass filter architecture based on interacting conducting ring resonators. Leveraging the inherent resonant behavior of copper rings, the design achieves multiple narrow passbands within the 1– 12 GHz frequency range. By systematically varying both the inter-resonator spacing and the number of rings, the study identifies an optimal configuration—particularly at an inter-ring distance of 6.75 mm—that maximizes the quality factor and transmission amplitude. Experimental results reveal distinct resonances at 2.2, 4.2, 6.6, 8.6, and 11.2 ± 0.2 GHz, corresponding to the fundamental and higher-order harmonic modes. The demonstrated filtering mechanism, characterized by compact size, tunable frequency response, and low insertion loss, offers a scalable solution for modern wireless communication systems. These findings indicate significant potential for integration into next generation 5G and emerging 6G networks, providing a cost-effective alternative to conventional filter designs.

This paper presents the design and analysis of a compact microstrip fixed-frequency double-inductive-coupled filter with selected band suppression. The filter can be used as an input filter in wireless IoT sensors. The proposed structure has reduced dimensions and improved out-of-band attenuation, achieved through the use of radial stub lines as elements of the resonators. These lines act as capacitors within the passband, while in a selected sub-band as series resonant circuits, effectively enhancing attenuation. The frequency response of the filter is shaped using two transmission zeros: the first one improves the steepness of the frequency response at the upper transition band, while the second increases attenuation in a chosen sub-band of the stopband. An analysis of the filter is presented, and key equations describing its properties are derived. An example filter for the frequency band 2.391–2.525 GHz, with additional suppression introduced in the U-NII 5 GHz band was designed, manufactured and examined. The insertion loss achieved by the proposed filter is lower than 1.6 dB, its attenuation across the whole stopband exceeds 30 dB and reaches over 40 dB in the 4.7–5.9 GHz frequency band.

This paper presents the design and analysis of a low-cost all-metal frequency-selective surface (AM-FSS). The proposed structure is manufactured using a laser cutting method on a 0.6 mm thick stainless steel sheet. The unit cell consists of a square ring with four stubs positioned off-center toward the middle of the structure. The AM-FSS functions as a bandpass filter, with measured resonance 5.91 GHz, a fractional bandwidth of 38.9 % , and an insertion loss of less than 1.0 dB. The design is remarkably thin, measuring just 0.011 λ 0 , where λ 0 is the free-space wavelength and has compact dimensions of 0.3 λ 0 × 0.3 λ 0 , making it suitable for miniaturized microwave applications. The proposed design is polarization-insensitive, exhibiting steady angular performance in both TE and TM modes, with a steady response for incidence angles up to 45 ∘ . An equivalent circuit model was utilized to evaluate the frequency response. A prototype of the design has been fabricated, and experimental results closely match the simulations, confirming the validity of the proposed design. The all-metal construction eliminates the need for commercial laminates, ensuring durability, high power handling capabilities, and cost efficiency. This makes the AM-FSS ideal for applications in microwave filtering and radar systems.

This work investigates the application of HfZrO ferroelectric material for the tuning of high-frequency bandpass filters. By integrating HfZrO with a two-dimensional HfSe semiconductor to form a heterostructure, the device achieves wideband tunability with low power requirements. Under a bias of ±4 V, the bandpass filter demonstrates a 3.4 GHz tuning range—from 7.8 GHz to 11.2 GHz—corresponding to a fractional tunability of approximately 43% in the X-band. The insertion loss remains below −1.8 dB across the tuning window, indicating low-loss operation. These results highlight the potential of the HfZrO/HfSe heterostructure as a promising platform for energy-efficient, CMOS-compatible, high-frequency tunable devices.

BackgroundTranscranial focused ultrasound treatments rely on precisely delivering ultrasound through the inhomogeneous human skull. Full‐wave ultrasound simulations are a means to predict and correct the resulting ultrasound aberrations and attenuation. To do this, the acoustic properties of the skull, including phase velocity and attenuation, must be determined. A common approach relates computed tomography (CT) Hounsfield Units (HU) to these acoustic properties. In the trabecular regions of skulls, the CT HU values will depend on the fraction of bone and marrow within an image volume element, but they are typically insensitive to the microstructure of the bone and marrow.PurposeThis study explores the influence of bone/marrow microstructures on determining the relationship of acoustic properties, particularly loss, to CT HUs. The typical clinical CT resolution (0.5 mm) cannot resolve fine trabecular bone microstructure, suggesting the relationship of attenuation to HU may be ill‐determined.MethodsThe ultrasound insertion loss was found through various skull‐mimicking digital phantoms consisting of two constituent materials (red marrow and cortical bone) from 0% to 75% porosity. The phantoms were assigned one of six pore diameters ranging from 0.2 to 1.0 mm. Ultrasound simulations were computed using k‐Wave with a continuous 230 or 650 kHz uniform pressure source. The insertion loss with and without absorption was defined as the mean pressure through the phantom with respect to the mean pressure in a water‐only reference.ResultsThe simulations at 230 kHz showed that the loss changed with porosity, but specific microstructure had little effect. However, in both nonabsorbing and absorbing 650 kHz source simulations, the insertion loss depended on porosity and pore diameter. Larger pore diameter phantoms generally had higher losses than smaller pore diameter phantoms at the same porosity. In the nonabsorbing phantoms, the maximum range in insertion loss was 2%–52% over the range of pore diameters, which occurred at 20% porosity. Absorbing phantoms increased the loss by an average of 8.2%, with the greatest increase of 13% occurring for the smallest pore diameter at 2.5% porosity. Coherent multiple reflections from the phantom's planar interfaces influenced the loss within smaller pore diameter phantoms. The phase coherence of these reflections was disrupted by increased scattering within the larger pore diameter phantoms.ConclusionThe results suggest that the relationship between attenuation and clinical HUs is ill‐determined at 650 kHz, since the insertion loss depends on both porosity and pore diameter. The demonstrated uncertainty has important implications for developing CT‐derived acoustic models of skull bone, as no single attenuation value can be related to HUs comprised of variable microstructures. Generally, our results show larger pore diameters (coarse microstructures) have higher loss than smaller pore diameters (fine microstructures) at the same porosity, which is consistent with scattering theory.

Objective.Transcranial focused ultrasound (tFUS) for neuromodulation has attracted increasing attention, yet accurate pre-procedural planning and dose estimation is constrained by oversimplified skull representations and by the neglect of transducer-skull spacing induced wave interactions. This study aims to develop and validate a computationally efficient, CT-informed analytical framework for predicting frequency-dependent insertion loss.Approach.We propose a multi-layer analytical framework that incorporates four key factors-skull thickness, skull density ratio, ultrasound insertion angle, and the transducer physical geometry and spacing from the skull, to predict frequency-dependent pressure insertion loss. Model accuracy was evaluated against k-Wave simulations and hydrophone measurements in 20ex-vivohuman skulls across 100 kHz to 1000 kHz frequency range.Main Results.Median prediction deviations for peak pressure insertion loss were +1.1 dB (interquartile range (IQR): +0.2 dB to +2.2 dB) relative to measurement and -1.7 dB (IQR: -2.7 dB to -0.7 dB) relative to simulation. The relative median percentage errors were +30.1% (IQR: +9.5% to +35.6%) and -20.3% (IQR: -31.7% to -10.1%), respectively. Median spearman correlation and cosine similarity values reached 0.92 (IQR: 0.86-0.98,p< 0.001) and 0.73 (IQR: 0.49-0.82), respectively. Uncertainty analysis showed that varying transducer-skull spacing resulted in a median absolute percentage uncertainty of 18.1% (IQR: 17.2% to 21.3%).Significance.The balance of accuracy and efficiency of the proposed CT-informed multi-layer model makes it a practical tool for transducer positioning, frequency selection, and dose control in tFUS neuromodulation, with potential to improve reproducibility and safety in clinical applications.

Graphene offers a promising pathway for ultra-high-speed data transmission in optical communications. Owing to its unique properties, including a zero bandgap, ultra-high carrier mobility of up to 2105cm2V-1S-1, and strong interaction with optical fields, graphene is considered an ideal material to overcome the limitations of bandwidth, speed, and Complementary Metal-Oxide-Semiconductor (CMOS) compatibility faced by traditional electro-optic modulators. This paper first reviews the three major physical mechanisms through which graphene achieves optical modulation, the all-optical threshold switching effect brought about by saturable absorption, the Mach-Zehnder phase modulation driven by refractive index changes induced by strong light fields, and the subwavelength localization and absorption enhancement caused by the coupling of graphene and plasmas. Based on this, the paper focuses on the latest advancements in three typical graphene optical modulation devices since 2020, including the miniaturization and CMOS compatibility achieved through waveguide integration, the expansion of free-space types in optical interconnection applications, and the enhancement of plug-and-play characteristics in fiber-end types. It also elaborates on the optimization of modulation depth, insertion loss, and energy consumption in these three types of devices. Finally, the paper points out that environmental oxidation-induced performance degradation, technical bottlenecks in material transfer processes, and insufficient compatibility between large-area h-BN packaging and processes remain core challenges that restrict its large-scale industrial application.

Abstract Thin-film lithium niobate (TFLN) has emerged as an attractive platform for integrated tunable photonic filters owing to its strong electro-optic response and low optical loss. However, conventional resonant filters, such as micro-rings, are intrinsically constrained by a limited free spectral range (FSR), which hinders their use in broadband and multi-channel operations. Here we present a TFLN-based add-drop filter that overcomes this limitation by employing a side-coupled travelling-wave Fabry–Pérot (FP) cavity formed with asymmetric multimode waveguide gratings (AMWGs). By engineering the inter-modal coupling through waveguide width tailoring and the reflection bandwidth of AMWGs, we realize a cavity with an intrinsic quality factor of 2.5 × 10 5 . The add-drop filter device also exhibits an FSR-free response across 1,500–1,630 nm wavelength band. A single resonance with a through-port extinction ratio of 20.23 dB and a drop-port insertion loss of 1.81 dB. Wavelength tuning by thermo-optic and electro-optic effect is demonstrated with efficiencies of 34.82 pm/K and 6.9 pm/V, respectively. Furthermore, a four-channel add-drop filter array with 3.2 nm channel spacing and 1.35 dB total through-port insertion loss validates the scalability of the present device. This work demonstrates an efficient approach to overcome the FSR constraint of sharp wavelength filters on TFLN. It can be potentially adopted in dense-wavelength-division-multiplexing communication systems, narrow-bandwidth microwave photonic filters, or high-resolution spectrometers.

ABSTRACT This paper presents a low insertion loss frequency reconfigurable magnetless nonreciprocal filter based on time‐modulated microstrip resonators. To achieve nonreciprocity, modulation signals are applied to the varactors through the microstrip circuits connected to each resonator. The center frequency of the proposed filter can be continuously tuned by changing the DC bias voltage applied to the varactors. We designed, simulated, and experimentally validated a fourth‐order microstrip nonreciprocal bandpass filter at L‐band. The results confirm that the center frequency of the proposed nonreciprocal filter can be tuned from 1.37 to 1.78 GHz (1.3:1 tuning) with a forward insertion loss from 2.1 to 2.6 dB and a backward isolation from 25 to 32 dB.

Abstract Chip‐scale nonreciprocal devices such as isolators and circulators are essential for optical communications, all‐optical signal processing, and LiDAR systems, owing to their compact footprint, manufacturability, and portability. Devices capable of handling short optical pulses are particularly desirable, as they enable reduced energy consumption, higher processing speed and improved ranging resolution and accuracy. In this work, a novel all‐optical, passive, bias‐free nonreciprocal silicon chip leveraging the high‐speed free carrier dispersion effect is introduced, pioneering new prospects of short‐pulse nonreciprocal silicon devices. An asymmetric and scalable silicon resonator is fabricated using standard CMOS techniques with a footprint of merely 100 µm 2 , achieving a nonreciprocal transmission ratio of 25 dB and an insertion loss as low as 1.65 dB. A noticeable blueshift of 0.05 nm is observed under a 1 ns pulse with incident peak power ranging from 9.3 to 234.4 mW. Furthermore, it is applied as a chip‐based isolator in LiDAR, exhibiting isolation and measuring consistency. This nonreciprocal device, optimized for short pulses, can significantly enhance the spatial resolution of LiDAR or increase on‐chip integration density by reducing the reflecting‐safe distance. Consequently, this work lays the foundation for high‐performance chip‐scale LiDAR and high‐density optical processing and communication devices.

Active Noise Cancellation (ANC) technology in headsets has revolutionized our audio experience in noisy environments. This paper presents a comprehensive study on the calibration of ANC headsets in the Standards and Calibration Laboratory. The calibration process involves precise measurements of passive and active insertion losses, both critical to the noise-cancelling effectiveness of the headsets. Additionally, the frequency response and total harmonic distortion characteristics are evaluated to ensure high-fidelity sound reproduction. The calibration frequency ranges from 100 Hz to 20 kHz. The calibration processes utilized a Head and Torso Simulator equipped with embedded Type 3.3 artificial ears within a free-field anechoic chamber, allowing for precise measurements and reliable results. This method allows for a comprehensive evaluation of ANC technology by examining both passive and active insertion losses, thereby assessing its effectiveness in attenuating external noise. Furthermore, the analysis of frequency response and total harmonic distortion ensures that the audio output remains true to the original signal across various frequency ranges. This paper describes (i) methods for measuring the acoustic parameters, (ii) the measurement model and uncertainty evaluation, and (iii) the measurement results and details of the calibration system.

A high-gain microstrip antenna array is proposed. The dual-frequency and dual-polarization characteristics of the array allow a satellite communication system to transmit and receive signals with a single antenna. To avoid high losses in microstrip feed lines for large apertures, the array is divided into subarrays, each fed by a low-loss separate feed network. The dual-frequency dual-polarization function is realized by utilizing two orthogonal modes of a corner-fed rectangular patch in a single-layer substrate. Moreover, to minimize losses in the separate feed network, semi-ridged coaxial lines and five four-way radial power dividers are employed. The power divider, composed of a cylindrical cavity and five SMA connectors, features very low insertion loss. Finally, to validate the design concept, a prototype of the proposed 32 × 32-element array operating at 12.5 GHz and 14.25 GHz is fabricated and measured. The measured results are in good agreement with the simulated ones. The −10 dB return loss frequency bands for the two operating frequencies are 12.04 GHz–12.69 GHz and 13.82 GHz–14.66 GHz, respectively. The measured gains at the two operating bands are 34.5 dBi and 35.2 dBi, respectively.

The heat shock response of Escherichia coli represents a canonical example of how bacteria can recognize a stress and invoke a protective response by altering specific gene regulation. However, most understanding of the processes involved arises from experiments where cells have been subjected to immediate heat shock. In this study, we identified the populations of transposon mutants in E. coli BW25113 involved in response to sudden heat shock and stepwise heat stress conditions. We used Transposon-Directed Insertion Site Sequencing with expression (TraDIS-Xpress) to identify genes whose function or expression contributed to survival under 5 different heat conditions. These conditions included direct exposure to 44°C, 47°C, or 50° C referred to as “heat shock” or half an hour exposure at 44°C, followed by exposure to 47°C or 50°C referred to as “stepwise heat stress”.A total of 530 genes were identified as contributing to one or more of the heat stress conditions tested, including known heat shock resistance genes. Only 8 genes were common to all 5 conditions, with 4 of these 8 genes being associated with energy generation. The results showed fundamentally different responses between shock and stepwise stress. In heat shock conditions, most genes conferring a fitness benefit contained an increase in insertions (loss of function) as compared to the control (37°C), while in stepwise heat stress, most genes conferring a fitness benefit had fewer insertions (representing protection of function) as compared to the control. Cell envelope genes involved in lipopolysaccharide biosynthesis (lpxM, lptC), the Tol-Pal system (tolABQR-pal), and outer membrane biogenesis (BAM complex) were detrimental during heat shock but essential for stepwise adaptation, while regulatory genes relA (stringent response) and the rsx operon (redox regulation) were specifically required for stepwise heat stress response.Prior exposure to sub-lethal heat stress dramatically alters the genetic landscape for survival, allowing energy-intensive adaptive responses rather than the cellular simplification strategies required during immediate heat shock. This work shows that stress responses are dependent on stepwise heat exposure whilst providing significant new information about the sudden heat shock.

ABSTRACT In this study, a new liquid crystal reflectarray unit configuration is proposed, which can significantly reduce the thickness of the liquid crystal layer with little impact on figure of merit (FOM). Based on the configuration, a polarisation-variable unit with polarisation-insensitive characteristics is presented in this work. By adjusting the distribution of liquid crystal states, the designed unit enables 2-bit phase control with extremely low insertion loss in both co-polarisation mode and cross-polarisation mode. Additionally, an array of 15 × 15 units is constructed to validate the performance, with simulations showing large-angle beam scanning capabilities in both modes.

ABSTRACT This paper presents a low-frequency wideband transmission frequency selective rasorber (FSR) based on topological optimization. The proposed method uses binary codes to represent the discretized surface structure of the lossy layer. The binary codes are integrated with structural parameter coding into an intelligent optimization algorithm, enabling efficient and automated FSR design. To tackle the binary discrete optimization problem effectively, an improved estimation of distribution algorithm (IEDA) is employed. This algorithm effectively circumvents the issue of building block disruption encountered by traditional evolutionary algorithms when handling discrete domain optimization problems through the use of a probabilistic model. The optimized FSR achieves an insertion loss below 3 dB across a wideband range of 0–5.44 GHz. It also attains over 90% absorptivity, with a peak of 99%, in the broadband range of 8.30–18.62 GHz. For validation, the FSR was fabricated and experimentally measured. The results agree well with simulations, confirming the feasibility of the design method and the reliability of the optimized structure.