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

This study proposes a novel wideband filtering Gysel power divider with a simple structure that exhibits improved passband and stopband performances, and we derive the entire design formulas. This power divider can be easily designed using these derived equations without iterative optimization. Moreover, the stepwise design procedures are described, and the advantages are compared with those of the existing structure. The wideband Gysel power divider is designed, fabricated, and used for measurements. The measured results showed 57% in-band fractional bandwidth, −3.89 dB insertion loss, and −13.4 dB minimum isolation. Meanwhile, the out-band fractional bandwidth is confirmed to be 69.5%. Harmonic suppression and isolation at 2f₀ are measured to be 46 dBc and −64 dB, respectively. The selectivity was measured to be about 20 dB at a frequency 1GHz away from the higher frequency of the passband. An analysis of the measured data allows us to demonstrate the validity of our proposed structure and derived design formulas.

The growing need for compact and more powerful antenna design for CubeSats has led to many creative solutions. To maximize surface area and handle high data rate, this paper discusses the development of reduced weight optically transparent (OT) meshed circularly polarized (CP) antennas designed for X band applications. Two analytical models of such transparent antennas are proposed. These transparent radiating elements are to be placed on the photovoltaic (PV) modules, utilizing the available space without affecting the renewable energy generation for the satellites. The goal is to design a transparent antenna where both radiating as well as reference trace layers are meshed, and quartz-made transparent dielectric material is used, operating at a frequency around X band with at least 10 dBi antenna gain. Circular polarization is achieved using perturbations, and a CP bandwidth of at least 50 MHz is achieved. This paper explores the effects of changing the mesh wire width on the antenna characterization metrics, comparing results with a solid, nonmeshed antenna. The meshed wire antenna has a reduced overall weight, as a bulk amount of copper is removed when meshed. The optical transparency has been achieved more than 80% for the narrowest width of the mesh, maintaining a 50 MHz CP bandwidth and 10 dBi right hand circular polarization (RHCP) gain. The outcomes of this study have proven to be an efficient, lightweight, and transparent antenna solution by allowing more experimental instruments to be installed on the chassis of nanosatellites.

This paper presents a design for a band-pass filter (BPF) with a desired phase shift at the inclined frequency in the passband. This design is achieved by combining a right-handed transmission line (RHTL), which exhibits positive phase propagation and works as a low-pass filter (LPF), and a left-handed transmission line (LHTL), which exhibits negative phase propagation and works as a high-pass filter (HPF). The proposed BPF simultaneously realizes a desired frequency filtering and phase shifting by cascading proper unit cells of RHTL and LHTL. To verify our proposed idea, we designed four BPFs with similar passband frequencies but different phase delays at a certain frequency in the passband. In the actual experiment, phase delays of 0°, +90°, −90°, and 180° were used, and the phase deviations from the designed phase shift were less than 9.59° at 600 MHz for all four phase delays. The insertion losses were maintained below 1.31 dB. As the RHTL and LHTL were synthesized with lumped elements only, the circuit is compact and applicable to monolithic microwave integrated circuit design.

In this work, an artificial neural network (ANN) architecture is proposed to estimate the optical signal-to-noise ratio (OSNR) used in a dense wavelength-division multiplexing (DWDM) transmission system in operational stations. The proposed neural network model, using the TensorFlow platform and Deep SHAP and kernel shape interpretation, provides a very close approximation of the values measured by the optical spectrum analyzer (OSA). The mean absolute error (MAE) estimate in the presented work is less than 0.04 dB for OSNR values. The proposed technique provides an updated network state under test based on real periodic measurements of operational systems. Also, the consistency of the proposed model with previous theoretical studies is evaluated and found acceptable. Using complex and accurate models such as ANN for operational commercial systems does not necessarily perform according to theoretical analyses. This is due to the complexities of analyzing transmission quality in optical systems and other factors such as equipment depreciation that are not usually considered in theoretical studies. Feature importance analysis can be effective in simplifying models based on network characteristics by eliminating less influential features while maintaining the required estimation accuracy.

In the existing radio frequency identification (RFID) system, a single reader antenna is used to identify and share data with the tag. In a large complex environment with dense packing of tag users, a single antenna often leads to a collision and delay due to having a limited data rate and poor coverage. To address the current issues, a dual-sense circularly polarized (CP) quad-port multi-input multioutput (MIMO) reader antenna is proposed that provides an opposite sense of rotation at diagonal pairs in this work. It introduces multipath propagation due to spatial diversity to enhance the RFID performance. Orthogonal modes of the proposed single-element antenna are evaluated using characteristic mode analysis. In the MIMO layout, a pair of U-shaped microstrip lines and a series of electromagnetic bandgap (EBG) structures are placed at the bottom side of the substrate for isolation improvement and axial ratio enhancement. The dispersion characteristics of the EBG cell justify the bandgap properties over the operating range. It displays an invariable response of a 10 dB impedance bandwidth of 21.3% (0.77–0.954) and a 3 dB axial ratio bandwidth of 18.8% (0.80–0.97) at all ports, covering the entire RFID band. The antenna maintains more than 25 dB isolation over the operating region of any pair of antenna ports, keeping the interelement spacing of 0.02 λ₀. λ₀ is the free-space wavelength at the midpoint operating frequency. Envelope correlation coefficient (ECC) lies below 0.0003, and channel capacity loss (CCL) is 0.0001 bits/s/Hz. The key features of the proposed antenna are suitable for a RFID application to read multiple tags in a crowded tag area with low latency.

In this article, a compact high selectivity bandpass filter with four transmission zeros (TZs) based on multilayer liquid crystal polymer (LCP) is proposed. A symmetric LC feedback structure is innovatively integrated into the conventional filter topology using the design of experiment (DOE) method, introducing two additional TZs in the stopband to significantly improve frequency selectivity and harmonic suppression. For compact implementation, a three-dimensional (3D) integration scheme is employed on the LCP substrate, utilizing vertically stacked spiral inductors and interdigital capacitors to achieve a miniaturized dimensions of 7.8 × 7.2 × 0.193 mm³. Measured results demonstrate a center frequency of 3.6 GHz, with the insertion loss (IL) of 1.43 dB and the return loss (RL) better than 23 dB in the passband. Moreover, the optimized feedback structure introduces four TZs at 2.18/2.88/4.39/5.21 GHz, ensuring superior out-of-band rejection. This improved design provides a promising solution for the miniaturized design of front-end modules for modern wireless communication systems.

In this paper, an ultrawideband self-decoupled building block with two antennas is constructed, which achieves high isolation between bandwidths without any decoupling structures. An ultrawideband operation is achieved by exciting two 0.25λ open slot modes and a loop mode. The wideband decoupling is usually a thorny problem, and our self-decoupling design within ultrawideband is verified by canceling the common and differential mode currents of every resonant mode. As a result, the proposed broadband building block not only operates in a wide bandwidth of 3.39–8.2 GHz (83%), including LTE band 42 (3.4–3.6 GHz), n79 (4.4–5 GHz), and both the n46 (5.15–5.925 GHz) and n96 (5.925–7.125 GHz), but also demonstrates high isolation (> 15.2 dB) over the entire bandwidth. An eight-element MIMO array consisting of four building blocks is designed, processed, and tested. The measured results demonstrate that the antenna system can provide good isolation in the 3.39–8.2 GHz operating band with good efficiencies (> 58%) and low ECCs (< 0.09). The proposed building block, with its benefits of ultrawideband, high isolation, self-decoupling, and simple structure, is very promising for 5G mobile communications.

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.