Search Results (5)

This paper proposes a design method for broadband power amplifiers based on bandpass filter matching networks. The approach incorporates transistor complex impedance transformation into the filter matching network design using a low-pass filter design model. By integrating CRLH and D-CRLH structural elements, it forms LC matching structures with a bandpass filter response. This structure achieves wide-band impedance transformation while also providing excellent frequency-selective capabilities. To validate this approach, a 0.7–1.3 GHz bandpass filtering power amplifier was designed and fabricated. It achieves in-band saturated output power of 38.4–41 dBm, drain efficiency of 41–58%, and power gain exceeding 12 dB. The gain flatness is limited to within ±2 dB. Experimental measurements validate the proposed design methodology. This approach imparts exceptional frequency selectivity and superior filtering performance to the system while enabling effective circuit miniaturization. Moreover, it exhibits considerable engineering significance and promising application potential in key fields such as satellite communications, radar monitoring, and digital broadcasting. Full article

This paper presents the design, implementation, and experimental validation of a Condition Monitoring (CM) circuit for SiC-based Power Electronics Converters (PECs). The paper leverages in situ drain–source resistance (R_ds,on) measurements, interfaced with cloud connectivity for data processing and lifetime assessment, addressing key limitations in current state-of-the-art (SOTA) methods. Traditional approaches rely on expensive data acquisition systems under controlled laboratory conditions, making them unsuitable for real-world applications due to component variability, time delay, and noise sensitivity. Furthermore, these methods lack cloud interfacing for real-time data analysis and fail to provide comprehensive reliability metrics such as Remaining Useful Life (RUL). Additionally, the proposed CM method benefits from noise mitigation during switching transitions by utilizing delay circuits to ensure stable and accurate data capture. Moreover, collected data are transmitted to the cloud for long-term health assessment and damage evaluation. In this paper, experimental validation follows a structured design involving signal acquisition, filtering, cloud transmission, and temperature and thermal degradation tracking. Experimental testing has been conducted at different temperatures and operating conditions, considering coolant temperature variations (40 °C to 80 °C), and an output power of 7 kW. Results have demonstrated a clear correlation between temperature rise and R_ds,on variations, validating the ability of the proposed method to predict device degradation. Finally, by leveraging cloud computing, this work provides a practical solution for real-world Wide Band Gap (WBG)-based PEC reliability and lifetime assessment. Full article

Copper metal ions (Cu²⁺) are widely used in various industries, and their salts are used as supplementary components in agriculture and medicine. As this metal ion is associated with various health issues, it is necessary to detect and monitor it in environmental and biological samples. In the present report, we synthesized a naphthoquinoline-dione-based probe 1 containing three ester groups to investigate its ability to detect metal ions in an aqueous solution. Among various metal ions, probe 1 showed a vivid color change from yellow to colorless in the presence of Cu²⁺, as observed by the naked eye. The ratiometric method using the absorbance ratio (A₄₁₃/A₄₇₆) resulted in a limit of detection (LOD) of 1 µM for Cu²⁺. In addition, the intense yellow-green fluorescence was quenched upon the addition of Cu²⁺, resulting in a calculated LOD of 5 nM. Thus, probe 1 has the potential for dual response toward Cu²⁺ detection through color change and fluorescence quenching. ¹H-NMR investigation and density functional theory (DFT) calculations indicate 1:1 binding of the metal ion to the small cavity of the probe comprising four functional groups: the carbonyl group of the amide (O), the amino group (N), and two t-butyl ester groups (O). When adsorbed onto various solid surfaces, such as cotton, silica, and filter paper, the probe showed effective detection of Cu²⁺ via fluorescence quenching. Probe 1 was also useful for Cu²⁺ sensing in environmental samples (sea and drain water) and biological samples (live HeLa cells). Full article

This study introduces a simple and cost-effective method for the indirect determination of field capacity (FC) in soil, a critical parameter for soil hydrology and environmental modeling. The relationships between FC and soil moisture constants, specifically maximum capillary water capacity (MCWC) and retention water capacity (RWC), were established using undisturbed soil core samples analyzed via the pressure plate method and the “filter paper draining method”. The aim was to reduce the time and costs associated with traditional FC measurement methods, as well as allowing for the use of legacy databases containing MCWC and RWC values. The results revealed the substantial potential of the “filter paper draining method” as a promising approach for indirect FC determination. FC determined as soil water content at −33 kPa can be effectively approximated by the equation FC33 = 1.0802 RWC − 0.0688 (with RMSE = 0.045 cm³/cm³ and R = 0.953). FC determined as soil water content at −5 or −10 kPa can be effectively approximated by both equations FC5 = 1.0146 MCWC − 0.0163 (with RMSE = 0.027 cm³/cm³ and R = 0.961) and FC10 = 1.0152 MCWC − 0.0275 (with RMSE = 0.033 cm³/cm³ and R = 0.958), respectively. Historical pedotransfer functions by Brežný and Váša relating FC to fine particle size fraction were also evaluated for practical application, and according to the results, they cannot be recommended for use. Full article

In view of the peak-to-average power ratio (PAPR) of wireless communication base stations, a Doherty power amplifier with high efficiency maintained at output power back-off (OBO) can effectively solve the problem of low efficiency of the traditional power amplifier at the point of power back-off. In this paper, we propose a method to implement a dual-frequency Doherty power amplifier (DPA) using a step-impedance low-pass filter to improve the bandwidth and efficiency of the DPA at output power back-off (OBO). Step impedance low-pass filters are used to solve the bandwidth limitations in traditional impedance converters and improve the efficiency of Doherty power amplifiers to a certain extent. In order to verify the proposed scheme, an efficient concurrent dual-band Doherty power amplifier operating at 2.0/3.5 GHz is designed and fabricated for the first range 1 (FR1) of 5G applications. In the measured results, the concurrent dual-band DPA achieves a saturated output power of 44 dBm and drain efficiency of 62% with a 6 dB back-off efficiency of 53% at 2.0 GHz and a saturated output power of 43.5 dBm and drain efficiency of 68% with a 6 dB back-off efficiency of 58% at 3.5 GHz. Full article