This paper proposes an optimized digital predistortion (DPD) framework. Firstly, a peak-detection-based loop-delay estimation is developed by leveraging the unique peak distribution of Orthogonal Frequency Division Multiplexing (OFDM) signals. It reduces the required number of samples to as small as two without compromising estimation accuracy. Then, a Biased Memory Polynomial (BMP) model is proposed for power amplifier modeling. It addresses low-power inaccuracies caused by circuit imperfections (e.g., DC offsets) by adding a bias term to conventional memory polynomials, improving linearization accuracy in low-power regime. Last, to improve the accuracy of coefficient derivation, Memory-Clustering Biased Memory Polynomial (MBMP) is proposed by grouping signals into clusters based on memory-attenuated input vectors and processing them with dedicated sub-models. It improves linearization accuracy in high-power regime. Experimental results demonstrate that the MBMP model reduces normalized mean square error (NMSE) by 16.12 dB, and reduces adjacent channel power ratio (ACPR) by about 12 dBm compared to conventional MP.

Orthogonal Time Frequency Space (OTFS) modulation has emerged as a leading candidate for 6G wireless systems due to its exceptional robustness against high mobility and frequency-selective fading channels. However, its multicarrier structure inherently generates a high Peak-to-Average Power Ratio (PAPR), making OTFS signals highly susceptible to nonlinear distortions introduced by High Power Amplifiers (HPAs). This paper investigates the impact of HPA nonlinearity on OTFS transmission in terrestrial radio environments, using the Rapp model to characterize amplifier behavior. We evaluate key performance metrics including PAPR, Complementary Cumulative Distribution Function (CCDF), Bit Error Rate (BER), Adjacent Channel Power Ratio (ACPR), and amplifier efficiency under varying Input Back-Off (IBO) values (0.5 dB to 4 dB). Our results demonstrate that OTFS exhibits a significantly higher PAPR than conventional 16-QAM, necessitating a larger IBO to avoid saturation. While increasing IBO improves linearity and reduces BER particularly in realistic Rayleigh fading channels it comes at the cost of drastically reduced amplifier efficiency, dropping from 70% at IBO = 0 dB to below 15% at IBO = 6 dB. Furthermore, nonlinear amplification severely degrades spectral purity: ACPR deteriorates from -37 dB (before amplification) to -15 dB (after amplification), indicating a 22 dB increase in out-of-band emissions and a substantial risk of interference with adjacent channels.

This article focuses on the necessity to enhance the current understanding of the accumulation and fate of pesticides and pharmaceuticals (emerging pollutants) in abandoned meanders and adjacent river channel bars. The primary objective of this study is to conduct a comparative analysis of pollutant concentrations in both settings and to identify the driving factors of their deposition. The studied sites are situated within two distinct catchments of the Morava and Odra rivers in the eastern part of the Czech Republic. The most prevalent pesticides were identified as propiconazole, metazachlor and tebuconazole. For caffeine and pharmaceuticals, the peak concentrations exceeded 10 µg/kg. The other pharmaceuticals frequently detected in these sediments were carbamazepine, diclofenac and metoprolol. The polycyclic aromatic hydrocarbons and polychlorinated biphenyls, selected for comparison (hereafter referred to as ‘legacy pollutants’), reached high to extremely high levels due to their frequent use in the past or present. Pollutant assemblages differed between channel bars and abandoned meanders. The maximum concentrations of emerging pollutants have been observed to be generally higher in abandoned meanders; however, the relative occurrence of pollutants has been found to be higher in channel bars. Abandoned meanders are most vulnerable to contamination in the first years following the cut-off, due to the increased frequency of flooding during this period. Consequently, they pose a higher environmental risk. Older meanders contain residual concentrations of pollutants and can serve as long-term sinks for organic pollutants, thereby providing temporal patterns. Conversely, channel bars represent current contamination levels and thus indicate spatial trends.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10661-025-14928-0.

This study compares the coherence characteristics of intracranial macroelectrodes and microelectrodes across different stages of the sleep-wake cycle (W, R, S1, S2). It quantifies intra-group and cross-group (macro-micro) coherence differences and analyzes the modulatory effects of sleep stages on multiscale synchrony. A publicly available iEEG dataset containing 960 segments of 32-second, 16-channel recordings (channels 18: macro; channels 916: micro) was utilized. Processing included trend removal, 0.5100 Hz bandpass filtering, 50 Hz notch filtering, and resampling to 256 Hz. Coherence spectra were estimated using the Welch method and averaged across five frequency bands: (0.54 Hz), (48 Hz), (813 Hz), (1330 Hz), and (3045 Hz). Adjacent channel pairs were used within macro/micro groups, and multiple random pairs were sampled across groups. Statistical analysis involved KruskalWallis tests across stages and MannWhitney U pairwise comparisons with Bonferroni correction. Results indicate a stable scale dependence in synchrony: macroelectrodes better reflect wide-area high-frequency coordination, while microelectrodes are more sensitive to local low-frequency synchronization. This finding supports the multi-scale organization of brain networks and highlights the necessity of integrating macro- and micro-level analyses in sleep and epilepsy research.

Dual-branch adjacent connection and channel mixing network for video crowd counting

Abstract Optoelectronic synapses have attracted considerable attention for emulating biological visual perception by enabling the recognition of complex visual stimuli, including spatial patterns and multicolor information. Despite significant progress, the realization of multicolor classification with simple and scalable device architecture remains a fundamental challenge, requiring strategies that overcome the limitations of conventional device configurations. Here, a scalable van der Waals heterostructure device is presented that enables multicolor optoelectronic processing by vertically integrating solution‐processed molybdenum disulfide (MoS 2 ) as a light‐absorbing layer and single‐walled carbon nanotubes (SWCNTs) as a semiconducting channel. Unlike conventional complex architectures, such as serially connected synaptic devices and optical‐sensors, the approach employs an electronically disconnected but interactive MoS 2 layer to facilitate photon‐modulated carrier doping in the adjacent SWCNTs channel. This configuration enables bi‐directional photocurrent behavior under different wavelength illumination, essential for emulating the retina's chromatic adaptation while maintaining a structurally simple and scalable design. Leveraging this unique bi‐directional photoresponse, an optical neural network framework is integrated that independently processes distinct spectral information, enabling highly efficient multicolor pattern classification. This synergistic strategy is essential for realizing scalable optoelectronic synapses, as evidenced by a classification accuracy of 92.0%, offering a promising platform for next‐generation vision systems.

ABSTRACTThis paper presents a compact analog predistortion (APD) employing spoof surface plasmon polaritons (SSPPs) to enhance the linearization of high‐frequency radio frequency (RF) power amplifiers (PAs). The APD–SSPP architecture integrates a Schottky diode (DBES105a) with a high‐Q tank circuit to improve harmonic suppression and mitigate third‐order intermodulation distortions (IMD3). The SSPP‐enabled impedance transformation enhances electromagnetic wave confinement, suppresses parasitic resonance effects, and optimizes power transfer efficiency by minimizing impedance mismatches along the signal path. Furthermore, broadband harmonic rejection is achieved by integrating radial stub elements, effectively mitigating spectral regrowth while maintaining high‐power‐added efficiency. Applied to the PA (ZX60‐V63), the proposed APD–SSPP achieves a gain tuning range of 3 dB, a phase variation of 0.9°, and an insertion loss of 4 dB. Experimental validation confirms that by using APD–SSPP, 65.9% IMD3 suppression, 14.5% carrier‐to‐intermodulation improvement, and a 36% adjacent channel power ratio reduction are achieved, significantly reducing out‐of‐band spectral emissions and improving the linearization performance of ZX60‐V63. These results establish the APD–SSPP as a highly efficient, miniaturized predistortion solution for next‐generation RF front‐end architectures in high‐data‐rate wireless communication systems.

ABSTRACT A design strategy with multifunctional network for out‐phasing power amplifier (OPA) is proposed. The multifunctional (M‐F) network using coupled lines is implemented to achieve reactive loading compensation of the fundamental wave and harmonic controlling, thereby enhancing efficiency. Leveraging the characteristics of the coupled lines, this configuration achieves conjugate reactance matching for upper and lower branches of the OPA using single network. In addition, the multifunctional network performs as the drain bias circuit, reducing the number of components needed for the output network. Benefiting from the proposed design strategy, efficiency enhancement and simplified circuit structure can be simultaneously obtained. An OPA using GaN devices with harmonic control coupled network is designed and implemented. The designed OPA achieves 44.3‐dBm saturated power at 2.4 GHz. Meanwhile, 72.5% and 58.7% drain efficiencies are obtained respectively at 6‐dB output power back‐off and saturation output power. For the down‐link long‐term evolution (LTE) signal with a channel bandwidth of 20 MHz and a peak‐to‐average power ratio (PAPR) of 8 dB, the average adjacent channel power ratio and error vector magnitude of the fabricated OPA reach −51.2 dBc and 1.48% after digital pre‐distortion.

Abstract We focus on the numerical analysis of a polygonal discontinuous Galerkin scheme for the simulation of the exchange of fluid between a deformable saturated poroelastic structure and an adjacent free-flow channel. We specifically address wave phenomena described by the low-frequency Biot model in the poroelastic region and unsteady Stokes flow in the open channel, possibly an isolated cavity or a connected fracture system. The coupling at the interface between the two regions is realized by means of transmission conditions expressing conservation laws. The spatial discretization hinges on the weak form of the two-displacement poroelasticity system and a stress formulation of the Stokes equation with weakly imposed symmetry. We present a complete stability analysis for the proposed semi-discrete formulation and derive a-priori hp-error estimates.

Neural networks are increasingly attractive for digital predistortion applications due to their demonstrated superior performance. This is mainly attributed to their ability to capture the intrinsic traits of nonlinear systems. This paper presents a novel hybrid predistorter labeled as the look-up table assisted bidirectional long-short term memory (BiLSTM) neural network (LUT-A-BiNN) that combines a neural network cascaded with a look-up table in a manner that both sub-models complement each other. The main motivation in using this two-box arrangement is to eliminate the highly nonlinear static distortions of the PA with the look-up table, allowing the neural network to focus on the compensation of the dynamic distortions. The proposed predistorter is experimentally validated using 5G test signals. The results demonstrate the ability of the proposed predistorter to achieve a 5 dB enhancement in the adjacent channel leakage ratio when compared to its single-box counterpart (BiLSTM neural network predistorter) while maintaining the signal-agnostic performance of the BiLSTM predistorter.

The rapid deployment of 5G/B5G networks necessitates power-efficient solutions for linearizing compact power amplifiers (PAs) in micro-cell base stations. Conventional Basis-Propagating Selection (BAPS) models face challenges including candidate explosion, collinearity, and diminishing contributions of basis functions. This paper proposes the Z-score Pruned BAPS (ZP-BAPS) model, a dual-strategy enhancement framework that integrates statistical significance validation with dynamic basis pruning to optimize digital pre-distortion (DPD). By embedding Z-score hypothesis testing into the greedy basis selection process, the framework systematically evaluates and eliminates statistically insignificant basis functions while preserving structural integrity through leaf-node prioritization. Experimental validation on a 6W GaN Class AB PA demonstrates that ZP-BAPS achieves significant performance improvements under computational complexity constraints (243 FLOPS): compared to conventional BAPS, it reduces normalized mean square error (NMSE) by 0.44 dB and adjacent channel power ratio (ACPR) by 0.71 dB for 64QAM-OFDM signals. Furthermore, it outperforms the DOMP model by 1.03 dB in NMSE and 1.14 dB in ACPR. Hardware implementation on FPGA confirms real-time feasibility with deterministic latency below 1.2 s. The proposed method establishes a statistically regularized paradigm for energy-constrained DPD, addressing the efficiency-accuracy tradeoff in low-power 5G deployments.

In a two-year experiment, we examined whether increasing plant diversity in the margins of processing tomato fields could attract pollinators and natural enemies of pests compared to weed flora, and questioned the effect on crop yield. Two plant mixtures sown in winter (WM) and spring (SM) were compared with weed vegetation along a tomato crop (CT) and an adjacent irrigation channel (CC). Flower cover was higher in the sown mixtures than the weedy margins, and brought in more visits of pollinating bees (including potential tomato pollinators) than the latter. Flowering species were mainly Eruca vesicaria (WM, SM), Coriandrum sativum and Lathyrus sativus (WM), Fagopyron esculentum and Phacelia tanacetifolia (SM), and Ammi majus, Rapistrum rugosum (CC, CT). Parasitoids (Eulophidae, Braconidae, Scelionidae) were more abundant in the sown and CC margins compared to the CT margin, while the abundance of predators (Aeolothripidae, Orius sp., Thomisidae) was similar among all types of margins. Fruit weight was higher in the field with the sown margins, while pest incidence in the crop was not affected by the margin type. Our findings provide new insights into the contribution of managed and existing field margins in attracting beneficial arthropods, and their implications on yield.

This paper presents a highly linear two-stage InGaP/GaAs power amplifier integrated circuit (PAIC) using a dynamic predistorter for 5G small-cell applications. The proposed predistorter, based on a diode-connected transistor, utilizes a supply voltage to accurately control the linearization characteristics by adjusting its dc current. It is connected in parallel with an inter-stage of the two-stage PAIC through a series configuration of a resistor and an inductor, and features a shunt capacitor at the base of the transistor. These passive components have been optimized to enhance the linearization performance by managing the RF signal’s coupling to the diode. Using these optimized components, the AM−AM and AM−PM nonlinearities arising from the nonlinear resistance and capacitance in the diode can be effectively used to significantly flatten the AM−AM and AM−PM characteristics of the PAIC. The proposed predistorter was applied to the 2.6 GHz two-stage InGaP/GaAs HBT PAIC. The IC was tested using a 5 × 5 mm2 module package based on a four-layer laminate. The load network was implemented off-chip on the laminate. By employing a continuous-wave (CW) signal, the AM−AM and AM−PM characteristics at 2.55–2.65 GHz were improved by approximately 0.05 dB and 3°, respectively. When utilizing the new radio (NR) signal, based on OFDM cyclic prefix (CP) with a signal bandwidth of 100 MHz and a peak-to-average power ratio (PAPR) of 9.7 dB, the power-added efficiency (PAE) reached at least 11.8%, and the average output power was no less than 24 dBm, achieving an adjacent channel leakage power ratio (ACLR) of −40.0 dBc.

Abstract Improving the efficiency of Trombe wall systems requires a focus on key influencing parameters. This study investigates the effect of temperature variations near the storage wall and insulation layer in a composite Trombe wall system using modified thermal equations. The results demonstrate that increasing solar radiation significantly enhances the thermal performance of the storage wall, leading to higher temperatures in the adjacent air channel. In contrast, the insulated wall exhibits minimal temperature changes due to its low thermal conductivity. The generalized reduced gradient algorithm was employed to optimize the model parameters, ensuring accurate and reliable results. The findings highlight the effectiveness of the proposed approach in analyzing and improving the thermal performance of Trombe wall systems, offering valuable insights for their design and optimization in practical applications.

This study explores the material basis and biological functions of meridian interstitial channels in mini-pigs proximal to the stomach meridian by analyzing differential proteomics between interstitial channels and adjacent non-interstitial channel tissues. Liquid chromatography-mass spectrometry (LC-MS) under data-dependent acquisition mode was employed to analyze and identify the proteome of subcutaneous connective tissues along the stomach meridian and adjacent tissues. SWATH MSALL method and omicsbean online analysis platforms were used for protein quantification and differential proteomic analysis. Differential proteins were subjected to Gene Ontology annotation and KEGG pathway analysis to understand their functions and biological processes. Combining traditional Chinese meridian theory with modern meridian research, proteins most relevant to meridian functions were selected, and their expression levels were assessed using Western blotting. GO annotation and KEGG pathway analysis revealed differences in molecular functions, biological processes, and metabolic pathways among differential proteins. Most downregulated proteins were enzyme functional proteins involved in amino acid metabolism (GOT1), adenosine nucleotide balance conversion (AK1), and calcium ion-binding processes (ANXA6). Most upregulated proteins were structural proteins in the extracellular matrix-collagen proteins (COL3A1, COL6A1, COL6A3, COL6A6, COL12A1, COL14A1) and proteoglycans (DCN, BGN, FMOD)-involved in influencing and regulating collagen fiber generation and arrangement. Intriguingly, almost all differential proteins were associated with gastrointestinal diseases, implying a pathological correlation of differential proteins in the stomach meridian interstitial channel. The stomach meridian interstitial channels in mini-pigs show 72 differentially expressed proteins compared to adjacent tissues. These differences include the upregulation of structural proteins and downregulation of functional proteins, potentially forming the molecular biological basis for the structural and functional specificity of meridians.

This paper presents a class-D outphasing power amplifier (PA) that incorporates a non-isolating balun combiner employing a 180° phase shift. Both isolating and non-isolating outphasing combiners are analyzed for signal restoration and combining efficiency. The proposed non-isolating balun combiner employing the 180° phase shift was experimentally evaluated and compared with a commercial isolating Wilkinson combiner. When two constant-envelope signals derived from a 10 MHz long-term evolution (LTE) signal are applied to the inputs of the outphasing combiners, both combiners demonstrate successful signal reconstruction. The measured adjacent channel leakage ratios (ACLRs) are −47 dBc for the Wilkinson combiner and −46 dBc for the proposed balun combiner. At 6 dB power back-off (PBO), the proposed balun combiner achieves a combining efficiency of 85.1%, representing an improvement of nearly 60% over the Wilkinson combiner. With a center frequency of 650 MHz, targeting 5G FR1 applications, a class-D outphasing PA was designed in a 28 nm CMOS process using the measured S-parameter data from both outphasing combiners. Simulation results show that the class-D outphasing PA incorporating the proposed balun combiner achieves a peak drain efficiency (DE) of 82.9% with an output power of 17.7 dBm. At 6 dB PBO, the DE reaches 61%, which is approximately 37% higher than that of the outphasing PA using the Wilkinson combiner. Moreover, the designed outphasing PA supports broadband operation over the 360–860 MHz range.

With the continuous expansion of communication bandwidth, accurately modeling the non-linear characteristics of power amplifiers has become increasingly challenging, directly affecting the performance of digital pre-distortion (DPD) technology. The high peak-to-average power ratio and complex modulation schemes of wideband signals further exacerbate the difficulty of DPD implementation, necessitating more efficient algorithms. To address these challenges, this paper proposes a wideband DPD algorithm based on edge signal correction. By acquiring signals near the center frequency and comparing them with equally band-limited feedback signals, the algorithm effectively reduces the required processing bandwidth. The incorporation of cross-terms for model calibration enhances the model fitting accuracy, leading to significant improvement in pre-distortion performance. Simulation results demonstrate that compared with traditional DPD algorithms, the proposed method reduces the error vector magnitude (EVM) from 1.112% to 0.512%. Experimental validation shows an average improvement of 11.75 dBm in adjacent channel power at a 2 MHz frequency offset compared to conventional memory polynomial DPD. These improvements provide a novel solution for power amplifier linearization in wideband communication systems.

ABSTRACTThis paper presents a two‐port folded monopole antenna to be used as a signal combiner and radiating element in outphasing applications, enhancing the system efficiency by minimizing insertion loss. A simple but effective circuit model is proposed to estimate radiated and reflected power based on impedance values and the outphasing angle. The equivalent circuit was validated through analytical and experimental methods, using standard measurement techniques to obtain the ‐parameters. Additionally, a custom setup utilizing a software‐defined radio platform was implemented to overcome the limitations of conventional instruments in measuring outphasing systems and to verify the proposed model. Measurements performed on a prototype resonating at 933 MHz demonstrated excellent linearity and spectral performance, achieving an adjacent channel power ratio (ACPR) below −45 dBc, superior to other combining antennas in the literature. Additionally, a reasonable error vector magnitude (EVM) of −32 dB was observed for broadband signals modulated with QPSK, 16‐QAM, and 64‐QAM.

Due to advancements in technological trends, interest in frequency multipliers is increasing in the research community. However, the linearization approach on frequency multipliers differs from that of power amplifiers and hence cannot be directly implementable for end-to-end high-frequency systems. This paper discusses recent computational approaches and proposes a model for improving performance metrics, especially the adjacent channel power ratio. This paper shows theoretical trends, mathematical approaches to current trends, and the proposed model. It then establishes the theory by experimental implementation and compares the proposition results to the models in the literature.

This paper presents a comprehensive review of GaAs HBT-based Doherty power amplifiers (DPAs) targeting 5G New Radio (NR) handset applications. Focusing on the critical challenges of linearity enhancement, back-off efficiency improvement, bandwidth extension under low-voltage (3.4 V) operation, and chip thermal management, the authors analyze state-of-the-art DPAs published in recent years. Key innovations including dynamic power division technique, third order intermodulation (IM3) cancellation technology, and compact output combiners are comparatively studied. Using 5G NR signals, the critical performance of the latest reported PA such as maximum linear power, back-off efficiency, bandwidth, and operating voltage are quantitatively investigated. The measurement results demonstrated that the best performance in recent DPAs achieved high linear power of 31 dBm with 34% PAE and 30 dBm with 31% PAE at the N78 and N77 bands, respectively. The corresponding adjacent channel leakage ratios (ACLRs) were lower than −36.5 dBc without digital pre-distortion (DPD). This review provides a comprehensive understanding of the latest advancements and future directions in highly efficient and linear DPA designs for 5G handset front-end modules.