Microwave and Optical Technology Letters最新文献

This paper proposed an accurate series resistance model tailored for Schottky diode-based terahertz multipliers. Compared to the conventional electrothermal model (E-T model) only considering thermal effects, this model comprehensively accounts for both thermal and frequency effects of the series resistor components, including the temperature-dependent epilayer resistance (R_epi) and the temperature-frequency-dependent spreading resistance (R_spreading). The evaluation of thermal effects relies on steady-state thermal simulation and the corresponding electrothermal model. Notably, the frequency-dependent spreading resistance part is derived from the fitting conductivity of doped buffer layers and extracted by auxiliary three-dimensional electromagnetic simulations. Based on this model, a balanced 225–300 GHz frequency tripler with AlN substrate has been designed and manufactured. By introducing this model, a significant improvement in the consistency between simulated and measured results has been achieved compared to the single E-T model, regardless of whether the input power is low (80 mW) or high (160 mW).

In frequency regions where ultra-wide band log-periodic antennas exhibit negative group delay (NGD), the effect of higher-order modes upon amplitude-modulated signals is examined using convolution theory. It is shown that in these frequency regions, the group delay and the effect of the higher order modes upon amplitude-modulated signals vary throughout the antenna's radiation pattern. It is also shown that the signal time advances predicted by the NGD are due to signal distortion when undesired higher-order modes are present on the antenna.

This paper presents a novel wideband dual-polarized air-patch antenna with enhanced port isolation. The proposed design consists of a suspended metal patch, two feeding slots, and novel composite decoupling structures (CDS). The CDS is composed of two reactive loads (RLs), an additional square slot (ASS), and two neutralizing lines (NLs). The reactive loads and one NL are connected to the feeding slots. The other NL is connected to the ASS. The CDS plays a critical role in achieving wideband high port isolation. The decoupling principles are illustrated by using a circuit model and through rigorous mathematical derivation. Design evolution of the proposed antenna (Ant 1–5) was carefully explained. Experimental results demonstrate that the proposed antenna has a −15 dB refection coefficient bandwidth covering the frequency range of 3.32–3.67 GHz. Additionally, it exhibits high port isolation (>35 dB), low cross polarization, high gain, and excellent total efficiency (>85%).

This article introduces a new, low cost and complexity, wideband Ku/K-band combined low-noise amplifier (LNA) Filter designed for large satellite phased array systems in advanced 22 nm Fully Depleted Silicon on Insulator Technology. The LNA achieves the required 20 dB gain through a two-stage configuration using the cascode configuration. To effectively reject the transmitter (TX) signal, the LNA integrates 4 distributed parallel LC notch filters. Measured IP1dB at 29 GHz (TX band) demonstrates a 25 dB increase compared to IP1dB at 19 GHz (RX Band), with a remarkable 15 dB enhancement over the LNA without the filter. The 1-dB gain bandwidth spans from 16 to 21 GHz, representing a 27% fractional bandwidth. Over the entire bandwidth, input/output return losses exceed 10 dB, maintaining a low noise figure (NF) of less than 3.5 dB. Inclusion of two filters at the input and middle of the first stage results in approximately 0.6 dB of increase in NF when compared to the LNA without the filter.

In this letter, we present a tunable band pass filter (BPF) using a dual-mode circular waveguide cavity resonator using a single tuning element. For the proof of the concept, a 2nd order tunable BPF has been designed and developed over a tuning range from 4.92 to 6.1 GHz (21.4%). The measured bandwidth is 85 ± 10 MHz over the entire tuning range. The peak insertion loss is within 1.3 dB and return loss is better than 15 dB. The tunable filter is proposed to be used in high Q reconfigurable radio systems.

We designed a novel elliptical topology fiber-optic sensing network to improve the coverage and reliability of fiber-optic sensing networks. A sensitive area model detection experiment of fiber Bragg-grating sensors was conducted, and a fiber-optic sensing network based on an elliptical topology model was established based on the optimal coverage. To further optimize the network performance, the graph theory's adjacency matrix, coupled with the shortest-path algorithm, efficiently uncovers and establishes the demodulation pathway for failed sensors in the fiber-optic sensing network at a higher rate, thereby improving the response speed of self-repair. Floyd's algorithm demonstrated a significant improvement in repair time compared with the standard practice, specifically reducing the repair time by approximately 88.25%.

In this work, we present a numerical and experimental study of the photothermal heating of microholes array (MHA) bowtie antennas on gold metal films. The article first shows how MHAs in gold metal films can absorb more heat depending on the geometry or placement of the MHA in each gold metal films. We show numerically and experimentally that the photothermal heating exhibits a maximum when the MHAs are patterned in a bowtie-like geometry. Numerical studies were carried out by using COMSOL multiphysics and experimental results were obtained using thermal imaging microscopy for several different MHAs geometries, respectively. Our results showed a good agreement between experimental data and the numerical simulations, validating that MHAs bowtie antennas on gold metal films heat significantly more and make them ideal for use in photothermal applications.

Organic matter is the material basis of life, which is widely present in people's products and lives. The rapid and accurate detection of organic matter can be applied to the identification of fake and inferior products, the traceability of the origin of agricultural products, and the early warning of explosives in antiterrorism. By combining laser-induced breakdown spectroscopy (LIBS) with argon, the spectral characteristics of five common organic compounds (nitroglycerin, metronidazole, polyformaldehyde, polypropylene, and phenolic resin), the plasma lifetime, the parameters of plasma thermodynamic state, and the distribution of three existing forms of the element C in two gas environments were compared, the influence of argon on organic LIBS results and the reasons for its enhancement were analyzed. The results indicate that argon makes the atomization of carbon chain structures in organic matter more complete, and reduce the interference of the element N in air on the organic LIBS results to a certain extent. The intensity differences of different organic substances are more obvious. support vector machine optimized by principal component analysis and particle swam optimization algorithm was used to classify five kinds of organic matter. The prediction accuracy of classification in air is 94.4%, and it improves to 100% in argon. This result provides a powerful method for high-precision, real-time in-situ, and rapid identification of organic substances, which has important scientific significance for the study of organic substances LIBS.

In this paper, a coupled-line-based wideband four-way filtering power divider (FPD) with unequal power division is presented. It is composed of three groups of coupled lines (CLs), four types of open-ended stubs, and three kinds of resistors. By setting the CLs in each group with different parameters, unequal power distribution is obtained. Besides, open-ended stubs with different characteristic impedances are inserted to each output port to generate two extra transmission zeros, at the same time maintaining good impedance matchings. Resistors are inserted to each group of the CLs to improve the isolations. By applying twice parity mode analysis, the exact synthesis of the proposed FPD is first derived. For demonstration, a prototype with power division ratio of 1:1.2:1.5:1.8 is designed and manufactured. Measurement results verified that more than 60% fractional bandwidth (FBW) is obtained under the criterion of 10 dB return loss and 10 dB isolation. Besides, the 3 dB passband FBWs for the four outputs reach 70% with high frequency selectivity and low insertion loss. And more than 15 dB out-of-band rejections are achieved for both the lower and upper stopbands.

We present a high-speed burst-mode optical receiver operating at 25-Gb/s with the shortest reconfiguration time of 4.52-ns reported up to date. The receiver consists of a burst-mode trans-impedance amplifier (TIA) with 1/8-rate clock-assisted DC offset cancellation loop as well as automatic gain control loop, and a burst-mode clock-data recovery (CDR) with two-stage injection-locking architecture. Both designed and fabricated in a 28-nm CMOS process, the TIA + CDR optical receiver consumes 101-mW from a 0.9-V supply. With a continuous-time linear equalizer, series inductive peaking and shunt inductive peaking, the 3-dB bandwidth of Z_T(O-E) of TIA is 20 GHz with 14-dB gain dynamic range (45–59 dB). The sensitivity of the burst-mode receiver is −10.1 dBm at BER = 1E-12.