A wideband high-temperature superconducting (HTS) duplexer is designed and is characteristic of more than 50% fraction bandwidth in its two channels. The duplexer is composed of a linear half-wavelength resonator and two channels. Each channel is composed of five dual-mode resonators with the attenuated second harmonic. To improve the isolation of the duplexer, we loaded a quarter-wavelength resonator at the output port of Channel 2; besides, a 5-pole dual-hairpin lowpass filter is cascaded at the output port of Channel 1 to improve its out-of-band rejection. The duplexer was fabricated on a MgO substrate coated with YBCO thin film on its double sides, and the area of the duplexer is 44.42 x 8.00 mm. The measured results showed that the 1 dB bandwidth of the channels is 2.679-4.645 and 5.083-9.014 GHz, respectively; the corresponding fractional bandwidths are 55.7% and 58.1%. The rectangularity of 60/3 dB is 1.51 and 1.11, respectively. The isolation between two channels is larger than 70 dB. The out-of-band rejection in the frequency range lower than 15 GHz is larger than 36 dB. The return loss is 10.6 and 6.0 dB and will be improved by subsequent tuning.
In this letter, a highly efficient and wideband power amplifier (PA) is proposed based on resistive-resistive series of continuous modes (Res-Res SCMS) with a new microstrip low-pass filter (LPF). By employing a conventional real-to-real impedance transformer, the output and input matching networks are realized by incorporating the transistor ' s parasitic elements. A new compact microstrip LPF, which exhibits a wide stopband with high suppression and a sharp frequency response, also serves as a real-to-real impedance matching. It shows less than 0.1 dB insertion loss and greater than 20 dB attenuation in the 4.2-10 GHz frequency range. The proposed PA is designed and fabricated using a CGH40010F GaN high electron mobility transistor (HEMT). The measured result shows that over the frequency band of 0.5-2.9 GHz, the large-signal gain is bigger than 9.77 dB, the drain efficiency (DE) is 58.2%-76.5%, and the output power is 39.77-42.99 dBm when the input power is 30 dBm.
This paper presents an innovative coupling design for a bandpass substrate integrated waveguide (SIW) filter, enabling high selectivity and facilitating flexible design. The proposed filter design has two parts: one is a mixed coupling structure, and the second part is a cross-coupling path. Both parts contribute to transmission zero (TZ) near the passband. Cross-coupling creates TZ, while mixed-coupling offers TZ and filter design flexibility. The cross-coupled path is analyzed in three configurations: without a load, with an inductive load, and with a capacitive load. To demonstrate this, three filter designs are simulated and fabricated based on the type of path load. The filter achieves center frequencies near 27 GHz with a fractional bandwidth exceeding 3%. Four to five TZs are introduced to enhance selectivity. Key performance metrics include a return loss exceeding 15 dB within the passband and an insertion loss between 1.65 and 2.1 dB. The measured results align with the simulated results, validating the structure and theory of the cross-coupled load.
Orbital angular momentum (OAM) antennas have recently attracted attention for their potential to enhance communication capacity and and robustness against interference. However, most existing designs rely on complex multilayer feed structures. This work presents a compact, single-layer, series-fed dual-mode OAM antenna composed of four patches arranged in a circular array with a 29 mm radius. The series-feeding network can be excited from two ports to simultaneously generate the l = +1 and l = -1 modes. Measurements were performed in an anechoic chamber to obtain far-field realized gain patterns and holographic phase distributions in the 6 GHz band. Two identical antennas were also tested in a transmit-receive configuration in a multipath environment using a two-port vector network analyzer. The maximum realized gains are 3.65 dBi for l = +1 and 4.8 dBi for l = -1 at 6.1 GHz. The proposed single-layer topology enables dual-mode OAM generation and supports multimode multiplexing, enhancing spectral efficiency and suppressing interference without added hardware complexity.
This paper proposes a 4 x 4 beamforming network (BFN) using a novel configuration. The proposed architecture utilizes a two-layer multi-aperture and multislot coupler (MA/MSC). Power coupling between ports within each layer is achieved through designed apertures. Additionally, power distribution between the upper and lower layers is facilitated by the embedded slots between the two layers. To validate the performance of the proposed design, a four-beam antenna is fabricated by connecting a 4 x 2 SIW slot antenna to the BFN. The satisfactory performance of the proposed BFN is validated through antenna measurements. Compared with conventional designs, the proposed BFN offers several advantages: fewer components, elimination of crossovers, and compact size (approximately 20 mm x 38 mm). These features make it highly suitable for fifth-generation (5G) wireless communication applications due to its size and simplicity.
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.
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 lambda 0. lambda 0 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.
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 degrees, +90 degrees, -90 degrees, and 180 degrees were used, and the phase deviations from the designed phase shift were less than 9.59 degrees 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.
The design and analysis of nanoelectromechanical systems (NEMSs) provide significant challenges due to the dominance of surface forces, quantum-scale effects, and complex material properties, where classical electrostatics and continuum mechanics become inadequate. Numerical modeling has therefore emerged as a powerful approach to predict device behavior prior to fabrication by ensuring reliability and stability. In this paper, a novel 3-bit distributed NEMS transmission line (DNTL) phase shifter is proposed and modeled using the quasilinear reproducing kernel particle method (QL-RKPM). Unlike conventional finite element or finite difference methods, the QL-RKPM provides enhanced accuracy and convergence in capturing the electromechanical behavior of nanoscale membranes by incorporating singular moment matrices and emphasizing linear approximations suitable for large deformations. The proposed DNTL phase shifter is designed with 33 periodically loaded NEMS membranes integrated over a coplanar waveguide (CPW) transmission line, enabling discrete phase control at three states (45 degrees, 90 degrees, and 180 degrees). Each membrane is modeled with 101 particles within its structural boundary to accurately extract the up (Cu) and down (Cd) capacitance values using QL-RKPM. The extracted capacitances, 7.06 fF and 20 pF, respectively, are incorporated into a capacitor-inductor-resistor (CLR) equivalent circuit model and simulated in the Advanced Design System (ADS) to evaluate the RF performance. The phase shifter achieves a low phase error of +/- 2 degrees with an average insertion loss of -0.6 dB and a return loss of -26 dB at 22 GHz by demonstrating excellent signal integrity and efficiency. The novelty of this work lies in the integration of QL-RKPM-based nanoscale electromechanical modeling with RF circuit-level performance evaluation, which allows precise prediction of capacitance variations and phase states without resorting to expensive or iterative fabrication. Furthermore, the proposed design provides multibit discrete phase shifting capability with compact size, low insertion loss, and improved reliability, making it a promising candidate for high-frequency phased arrays used in 5G wireless systems.
Multiple-input multiple-output (MIMO) technology has garnered widespread attention due to its remarkable ability to significantly augment system channel capacity. With the objective of boosting the channel capacity for the fifth-generation (5G) mobile communication, we propose a 5G terminal MIMO antenna with a compact structure and high isolation operating in 3.4-3.6 GHz. In order to achieve greater channel capacity while ensuring maximum isolation among MIMO elements, 14 miniaturized units utilizing self-decoupling technology are positioned under the chassis model. This results in a significant decrease in mutual coupling, reaching a level of -13.5 dB, while simultaneously increasing the channel capacity to a level of 55.5-59 bps/Hz. Additionally, the feasibility of the proposed mobile terminal MIMO antenna is demonstrated through simulations involving human hand models, thereby confirming its practical application.
A novel frequency selective surface (FSS) element consisting of multilayer Jerusalem cross and double ring is proposed in this paper, which could independently achieve transmission/reflection polarization conversion at higher/lower frequency bands. Based on this fascinating characteristic, a dual-band transmissive-reflective circular polarizer is designed, fabricated, and measured by employing a set of these FSS unit cells. The designed circular polarizer consists of 19 x 19 elements and is capable of flexibly transforming linearly polarized (LP) incident wave into circularly polarized (CP) transmitted/reflected counterpart at higher/lower frequencies. Both simulated and measured results are basically consistent, which prove our proposed circular polarizer has the advantages of planar integration, easy manufacture, and dual-band operation. The fabricated polarizer prototype shows 3-dB axial ratio bandwidths of 10.7% (11.5-12.8 GHz) and 11.7% (8.8-9.9 GHz) for the transmitted and reflected wave at normal incidence, respectively. The proposed approach provides a new way to develop multifunctional devices for generating transmissive and reflective CP signals at different bands, which is promising for applications in modern satellite communication systems.
This paper presents a highly efficient and high-gain single-port dual-band antenna designed for WLAN applications. The antenna offers -10 dB impedance bandwidths of 450 MHz (2.3-2.75 GHz) and 2300 MHz (3.95-6.25 GHz), covering the WLAN 2.4 and 5 GHz bands. It consists of a radiating patch and an artificial magnetic conductor (AMC) reflector with overall dimensions of 50 x 80 x 28.2 mm. Both the radiating element and the AMC unit are attached to an FR-4 substrate with a relative dielectric constant epsilon r of 4.4 and loss tangent tan delta of 0.02. By incorporating the reflector, the antenna achieves directional radiation and high gain. The proposed antenna prototype was tested, demonstrating total efficiencies exceeding 83% in both frequency bands. Additionally, at the operating frequency of 2.4 GHz, the simulated and measured half-power beamwidths are approximately 100 degrees and 86 degrees, respectively. At the frequency point of 5.5 GHz, the simulated and measured half-power beamwidths are approximately 56 degrees and 50 degrees, respectively.
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.
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.
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 mu m 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 x 230 mu m.
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.
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 degrees. 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.
