International Journal of RF and Microwave Computer-Aided Engineering最新文献

The current techniques in performance improvement of space traveling wave tubes (TWTs) have limitations. It is difficult to consider the balance of several technique indexes, optimized design accuracy, and calculation cost. To tackle such a burden, a multiobjective optimization framework based on the Kriging model is proposed in this research. This framework takes advantage of what Kriging models approximate the responses of the electromagnetic simulation process. It reduces the obstacles caused by multiple-task calculations of TWTs due to the high cost of accurate simulation. In the design of the L-band helix TWT in this research, the predicted values of the model are used as the objective functions, and the multiobjective optimization of its interaction segment is carried out. Also, the proposed infill sampling criterion based on the subtractive clustering method in this research raised the efficiency of building the Kriging model. The numerical results demonstrate that the proposed multiobjective optimization framework is reliable for designing TWTs. It can quickly produce an optimal design scheme, significantly improving the performance of the designed TWTs compared to the original design.

In this paper, a W-band broadband vialess microstrip (MS)-to-MS vertical transition based on coplanar waveguide (CPW) multimode resonators (MMRs) on a four-layer liquid crystal polymer (LCP) substrate has been proposed. In this four-layer structure, the CPW MMRs are located in the second layer, the top layer T-type MS and the third layer MS are combined to form the feeding structure and excite the resonant modes. The proposed CPW MMRs can achieve multimode excitation by shifting the location of the feeding points, and then mutual coupling is to form a broadband vialess vertical transition. In order to further improve the transmission performance of this vialess vertical transition in W-band, the offset distance between two feeding points of the CPW MMRs is optimized by HFSS, thus three resonant modes are introduced within the frequency range from 70.38 to 100.03 GHz. To verify this design, a three-pole broadband vertical transition fabricated on a four-layer LCP substrate is measured. The measured results indicate that a broadband structure ranging from 75.66 to 97.71 GHz can be obtained with a minimum in-band insertion loss (IL) of 1.8 dB and a return loss (RL) of above 10 dB. Therefore, the superiority of the proposed CPW MMRs in the realization of broadband vialess vertical transition is effectively verified.

In this paper, an area-efficient low-noise amplifier for GPS L1 band application is designed. Besides the requirements of noise figure (NF), bandwidth, and input matching, the design methodology has been focused on the area efficiency. As a design example, a prototype L1 band LNA is implemented using standard 0.11 μm CMOS technology. The design is based on a conventional cascode inductive source-degenerated topology, but special care has been dedicated to the three inductors. To reduce cost, specifically by minimizing on-chip area and imposing constraints on power consumption, the source inductor is implemented using a bond wire. As the dominant contributor of silicon area, the drain inductor has been optimized in a very area-efficient way. The design trade-off between input matching and noise matching is consequently adopted to achieve minimized NF. Measurement results indicate that the LNA achieves a measured power gain of 14.3 dB at 1.57 GHz with a NF of 1.37 dB, while consuming 1.9 mA from a standard 1.8 V supply and occupying a chip area of 300 × 230 μm.

This paper proposes a compact and high-gain filtenna array based on substrate-integrated waveguide (SIW) technology for the W-band (75–110 GHz) high-speed wireless communication systems and imaging/detection systems. By utilizing the high integration of SIW technology, the SIW filter, butterfly slot antenna array, and patch antenna array are vertically integrated to form a filtenna array. Due to the vertical integration of two antenna arrays, the filtenna array achieves a smaller footprint. The use of butterfly-shaped slot antennas increases the bandwidth of the antenna. The butterfly slot antenna array and patch antenna array each have five units. After fabrication and testing, the filtenna array achieves high gain as well as filtering function, reducing the size of the overall circuit. The filtenna array has a center frequency of 95 GHz, a bandwidth of 3 GHz, and a maximum gain of 12.95 dB.

A data transmission system is designed for the SDGSAT-1 small satellite to meet the high-speed data processing and transmission requirements. The data transmission system consists of two principal components: the transmitter and the steerable transmission antenna. To satisfy the satellite link budget requirement, the 37.5 dBm X-band transmitter has been developed for an 810 Mbps data rate with 8PSK modulation. The dual circularly polarized antenna with a pointing mechanism has a gain of over 20 dBi, and the pointing accuracy error is less than 0.110°. The data transmission system’s EIRP exceeds 28 dBW. On-orbit operations have demonstrated that the data transmission system exhibits excellent performance and high reliability.

This paper presents a multifunctional wearable antenna that operates in multiple frequency bands, including 2.4, 4.5, 5.8, and 6.4 GHz. The proposed antenna structure is designed for both industrial scientific medical (ISM) and wireless body area network (BAN) frequency bands. The antenna employs metamaterial (MTM) unit cells to enable modes with different radiation patterns, implementing monopole-like (null at broadside) and patch-like patterns for on- and off-body communications. The maximum gain achieved is 7.6 dB at 4.5 GHz, and the antenna also provides circular polarization in the off-body frequency (5.8 GHz) with a minimum 1.13 dB axial ratio (AR). The structure is fed by a microstrip feedline for user convenience, and a full-ground plane is included to protect the human body from backward radiation. To validate the advantages of the proposed design, the antenna was fabricated, and its parameters were measured. The results showed good agreement between simulation and measurement. The effect of antenna bending was also investigated, and the results indicated that the antenna operates acceptably for bending radii up to 60 mm. Additionally, the specific absorption rate (SAR) was investigated, and low values below the standard rates were confirmed.

The fusion of deep learning techniques with conventional methods has garnered significant attention within the field of electromagnetic inverse scattering. The utilization of a traditional noniterative method for acquiring a presolution, followed by an enhancement procedure via neural networks, presents notable benefits such as simplicity and fast computational speed. However, the accuracy of this approach is usually impacted by the precision of the presolution, especially for strong scatterers. To alleviate this limitation, this research introduces a novel learning-based variational backpropagation method (VBPM). Through the utilization of variational operations, the proposed method refines the initial induced current obtained by the backpropagation (BP) method. Subsequently, an appropriate neural network is constructed to establish the relationship between the refined presolution and the true solution. Compared with the BP scheme (BPS) without variational operations, the proposed approach effectively enhances the solution accuracy with almost the same inversion time.

Wavelength division multiplexing (WDM) technology is widely used in high-capacity optical communication systems, enabling the simultaneous transmission of multiple signals over optical fiber. However, signal attenuation and dispersion pose significant challenges to long-distance optical transmission. To mitigate these effects, this study investigates the performance of a four-channel dense wavelength division multiplexing (DWDM) network with and without the use of an erbium-doped fiber amplifier (EDFA) and linear chirped fiber Bragg grating (LCFBG). In the absence of EDFA and LCFBG, the signal quality factor (QF) deteriorates as the bit rate increases, with a marked degradation at higher transmission speeds. Our results show that the introduction of EDFA significantly reduces the bit error rate (BER) and improves the QF. Moreover, combining EDFA with LCFBG provides superior performance, effectively compensating for dispersion and attenuation across various transmission distances (0.5, 1, 1.5, and 2 km) and data rates (2, 5, 8, 10, 15, and 20 Gbps). The combination of EDFA and LCFBG outperforms other configurations in terms of signal quality, with a notable improvement in the QF and overall system reliability. These findings suggest that the integrated use of EDFA and LCFBG is an effective solution for enhancing the performance of DWDM systems, especially for long-haul, high-capacity optical transmission.

Improving the efficiency of backward wave oscillators (BWOs) operating in a low magnetic field regime remains a significant research challenge. In this field regime, increased transverse motion of electrons leads to variable interaction impedance. Consequently, the beam wave synchronization with the desired mode is disrupted, resulting in reduced efficiency. To partially overcome this challenge, an adiabatically varying nonuniform slow wave structure (SWS) with a circular ridged wall profile is proposed. The SWS helps in maintaining the synchronization of the beam bunch with the desired normal mode throughout the interaction length. The circular SWS increases the field breakdown limit of the electrodynamic structure. This, in turn, results in an average output power of 810 MW at 9.8 GHz with a power increment of 50% compared to the uniform SWS, guided by a 0.6 T magnetic field. The low magnetic field operation helps in the implementation of a permanent magnet, which results in a repetitive microwave system. The novelty of this work lies in the use of an adiabatically tapered, nonuniform SWS geometry to ensure continuous synchronism at low magnetic fields, which is rarely addressed in conventional BWO designs. This method offers practical significance in reducing system size, weight, and cost by eliminating bulky electromagnets. Further efficiency enhancement is limited by overbunching, which induces Coulomb instability and leads to back-streaming of electrons, as observed in particle-in-cell simulation conducted using CST Microwave Studio.

We propose a multifunctional cascade metasurface designed for manipulating electromagnetic waves in the microwave frequency range with comprehensive theoretical analysis, design optimization, and experimental validation. A set of electrically thin metasurfaces based on planar spirals with free space impedance is used to manipulate electromagnetic waves. The metasurfaces simultaneously generate distinct, independent, and mutually compatible wave transformations at various frequencies. A multifunctional cascade metasurface integrates several functional devices, including a reflective cross-polarizer, a transmissive cross-polarizer, and a nonreflective absorber. Each designed metasurface has a free space impedance over a sufficiently wide frequency range that encompasses the operating frequencies of all metasurfaces. This attribute guarantees the autonomous and mutually noninterfering functioning of all metasurfaces in the cascade.