Improved Insertion Loss Research Articles

A gap waveguide-based mechanically reconfigurable phase shifter for high-power Ku-band applications

This paper presents a novel design of a low-loss, reconfigurable broadband phase shifter based on groove gap waveguide (GGW) technology. The proposed phase shifter consists of a folded GGW and three bends with a few pins forming the GGW and one bend attached to a movable plate. This movable plate allows for adjustments to the folded waveguide length, consequently altering the phase of electromagnetic waves. The advantage of GGW technology is that it does not require electrical contact between different parts of a structure. Therefore, it enables the moving parts to slide freely without electromagnetic energy leakage, resulting in improved insertion loss in high-power applications. In addition, in the proposed design, the position of the input and output waveguide ports of the phase shifter remains fixed, which is advantageous from a practical point of view. As shown by measurement and simulation results, there is nearly 37% impedance bandwidth with the highest insertion loss of 0.6 dB, and the developed device has a maximum phase shift of 770° at the center frequency of 13 GHz. The phase shifter can be used for various radar and satellite applications that require phase control, such as beamforming networks and phased array antennas.

Compact circular microstrip 1:4 power divider/combiner with defected ground plane

This letter presents a methodology for the design of high-performance miniaturized Circular Power Dividers (CPDs) for wideband applications. To accomplish this objective, annular slots are strategically incorporated into patch and the ground plane of CPDs. This, in turn, increases the effective path length of the surface current flowing across the patch. This yields miniaturization, improved impedance matching, reduced insertion loss and increased isolation over a larger bandwidth. A mathematical model is developed for the design of the proposed configuration called Circular power dividers with Defected Ground Plane(CDGP). The presented model has been verified through various simulations and practical measurements. By implementing this approach, a substantial miniaturization of approximately 83% and more than threefold increase in bandwidth has been achieved when compared with non-slotted CPDs. Moreover, there is improvement in insertion loss, isolation, and return loss as well. There is good agreement between the mathematical model, simulation results and measured parameters.

Design and fabrication of waveguide‐based graded refractive index Rotman lens with an improved insertion loss at Ka‐band

AbstractThe design and optimisation of a five‐cascade layer Rotman Lens based on waveguide with a graded refractive index at Ka‐band frequency are presented. The proposed lens incorporates 5 layers within the cavity, utilises a modified three focal Rotman lens design methodology to achieve perfect phasing for true time delay beam steering, and optimises each layer's parameters such as refractive index, vertex location, and contour angle to improve insertion loss between input ports and output array elements. This approach enhances energy concentration between input and output ports, reducing spillover to dummy ports. The graded layers are formed using periodic cubic metallic posts with varying heights within a parallel plate waveguide. The results show an average improvement in the insertion loss of 16% and a peak improvement of 48% across the bandwidth when compared to conventional Rotman lenses. The normalised average phase error across the array elements for all beam ports excitation is 4 × 10−3 and the peak degradation of the main beam during beam scanning from 0° to ±22° varies from 0.7 to 1 dB at different frequencies operating in the Ka‐band (24–30 GHz) with potential applications for 5G communications. The simulation results demonstrate good agreement with the measurement results.

Packaging and Antenna-Assembled Hybrid Stacked PCB with Novel Vertical Transition for 39 GHz 5G Base Stations

This paper proposes a novel packaging and large-scale antenna-assembled structure for a printed circuit board (PCB) that reinforces productivity, facilitates cost reduction, and maintains reliability. This was achieved by splitting the antenna from the main board and packaging it into a radio-frequency integrated circuit. In addition, two innovative solutions—an externally attachable flexible PCB antenna and a PCB-embedded coaxial line—are introduced to overcome the degradation in antenna performance and vertical RF transition loss in the proposed low-cost hybrid PCB. First, the proposed externally attachable flexible PCB antenna and a parasitic aircoupled antenna, which were easily assembled on the PCB, achieved an antenna efficiency of 95% and an impedance bandwidth of 7 GHz. Second, the fabricated coaxial line exhibited enhanced impedance matching over a wide frequency range of 30–40 GHz and improved insertion loss of approximately 1.4 dB. Furthermore, the packaged antenna, composed of 256 dual-polarized antenna elements per stream, incorporated a 39 GHz CMOS-based 16-channel phased-array transceiver IC. The set-level beam-forming measurements were verified considering an effective isotropic radiated power of 55 dBm at boresight and a steering range >±60°. In addition to being suitable for mass production in terms of cost and reliability, the proposed structures and solutions met the required antenna and beam-forming performance for commercial 39 GHz base stations without sacrificing performance.

Improving Insertion Loss of Sonic Crystal Active Noise Barrier by Reinforcement Learning and Finite Difference Time Domain Simulations

Improving Insertion Loss of Sonic Crystal Active Noise Barrier by Reinforcement Learning and Finite Difference Time Domain Simulations

A Comparative Study of Conventional Transition Model and Reverse Transition Model for Wireless and Radar Applications

Microstrip line-to-waveguide transitions (MLWT) finds various applications in the field of RADAR engineering, navigation science, medical electronics, household equipment, satellite tracking equipment, wireless communications etc. Conventionally, the MLWT is designed so that the microstrip line is inserted in E-plane and perpendicular to the waveguide’s side wall, while the microstrip probe’s radiating face is towards the waveguide’s open end port. In this paper, an MLWT has been designed for Ka-band applications and the transition has been designed in such a way that the radiating face of the inserted microstrip line probe is towards the short circuit end of the waveguide. The method is called the reverse transition method. The microstrip signal reflected from the short circuit end comes in additive phase with the traveling wave and the strength of the traveling wave increases. MLWT has been developed using this method and results for Ka-band applications are presented in this paper. This work reported more than 20 dB improvement in return loss (RL), 0.1dB improvement in insertion loss (IL) and almost 7 to 8% enhancement in 10dB fractional bandwidth compared to the conventional method. Comparative analysis of the two methods has been shown in tabular form at the end of the paper.

Inverse Design and Numerical Investigations of an Ultra-Compact Integrated Optical Switch Based on Phase Change Material.

The miniaturization of optical switches is a promising prospect with the use of phase-change materials (PCMs), and exploring various strategies to effectively integrate PCMs with integrated optical waveguides represents an intriguing research question. In this study, an ultra-compact integrated optical switch based on PCM is proposed. This device consists of a Ge2Sb2Te5 nano-disk and an inverse-designed pixelated sub-wavelength structure. The pixelated sub-wavelength structure offers customized refractive indices that conventional materials or structures cannot achieve, leading to an improved insertion loss (IL) and extinction ratio (ER) performance of the device. Furthermore, this structure enhances the interaction between the optical field and GST, resulting in a reduction of the device size and the inserted GST footprint. With an ultra-compact device footprint of 0.9 µm × 1.5 µm, the simulation results exhibit a low IL of 0.45 dB, and a high ER of 18.0 dB at 1550 nm. Additionally, relevant studies show that this device is able to perform reliably despite minor variations in the manufacturing process.

Signal Integrity Analysis of Through-Silicon Via (TSV) With a Silicon Dioxide Well to Reduce Leakage Current for High-Bandwidth Memory Interface

In this paper, we propose and analyze a through silicon via (TSV) with a silicon dioxide well (SDW) to reduce leakage current in the design of a high-speed signaling and low-power consumption high-bandwidth memory (HBM) interface. In the proposed TSV, the SDW is inserted into the silicon substrate area between TSVs. By inserting the SDW, the silicon substrate’s effective conductivity and permittivity are lowered compared to a conventional TSV. The proposed TSV with the SDW improves insertion loss by up to 0.079 dB at 4 GHz by minimizing the leakage current. In addition, by reducing the effective permittivity of the silicon substrate, the difference in ratio between the capacitive coupling and inductive coupling is minimized. It is also possible to obtain a reduction in far-end crosstalk (FEXT) in the range of HBM interface signaling. RLGC modeling of the proposed TSV with the SDW is presented, and is physically analyzed based on the frequency-dependent equivalent capacitance and conductance of the silicon substrate. The proposed TSV with SDW is finally evaluated using an eye diagram, and the eye height and width improved by up to 13.7 % and 4.7 % at 8 Gb/s, respectively, compared to the conventional TSV. The proposed TSV also reduced dynamic power consumption by 48.1 % at 8 Gb/s, verifying the low-power structure.

Use of viscoelastic polymer sheet as an acoustic control treatment in ceramic tiles to improve sound insertion loss

Ceramic tiles are commonly used in non-structural components of a building such as walls, partitions, floors, and roofs. However, due to their high surface hardness and density, ceramic tiles are not an ideal soundproof material. To improve the sound properties, this study introduced the use of a viscoelastic polymer sheet (VPS) as an acoustic control treatment. The VPS was attached to ceramic tiles in 4 different patterns: X, Cross, Corner, and Strip. The ceramic tiles with VPS were tested for the damping property and sound insertion loss (IL) and then compared to the ones without VPS. Results indicated that the attachment of VPS improved the damping property of the ceramic tiles. All tiles with VPS exhibited higher damping loss indexes than the ones with no VPS. The highest damping loss index of 0.017–0.018 was observed in the specimens with VPS in X and Cross patterns. In the case of IL, the performance of all ceramic tiles was indifferent when tested at sound frequencies smaller than 1000 Hz. At the sound frequencies above 1000 Hz, the best performance was observed in the specimen with VPS in the Cross pattern, followed by X, Strip, and Corner patterns, respectively. This concluded that the use of VPS can improve the damping property of a ceramic tile which also leads to the improvement in sound insertion loss.

Improved TM Dual-Mode Filters With Reduced Fabrication Complexity

This work presents an alternate and improved approach for the design of dual-mode filters that utilize transverse magnetic (TM) and nonresonating modes. The method that is proposed in this work allows for an improvement of the typical TM dual-mode filter design through the reformation of the coupling irises that connect the TM dual-mode cavity to the source/load waveguide ports, where the new interconnection means takes the form of resonate slot-irises. In this manner, a fourth-order quasi-elliptic response can be achieved within a very limited physical geometry and able to cover more than double the usable fractional bandwidth than previously reported. Furthermore, the selectivity and insertion loss of the filter response is significantly improved when compared to the typical single-cavity TM dual-mode filter response that uses coupling irises, while on the comparison of equal-order structures, a reduction in fabrication complexity and improved insertion loss is achieved. A characterization of the dimensional variations and effects of altering one of the source/load port positions in the proposed filter design is investigated in order to demonstrate notable effects on the rejection characteristics and positions of transmission zeros. A presentation on the design theory is given and formulations of various filter responses are examined. The fabrication of an experimental prototype with approximately 7.3% fractional bandwidth (FBW), centered at 90 GHz is conducted using high-precision computer numerical control (CNC) milling in order to demonstrate that the unique simplicity and overall compaction of this method can be easily applied at millimetre-wave frequencies without the need of tuning means. The results which are presented demonstrate highly accurate measurements throughout the W-band range, while an additional Q-factor analysis is provided in order to compare the improved filter scheme with other known design methodologies.

Experimental demonstration of robust nanophotonic devices optimized by topological inverse design with energy constraint

In this paper, we present the experimental results for integrated photonic devices optimized with an energy-constrained inverse design method. When this constraint is applied, optimizations are directed to solutions that contain the optical field inside the waveguide core medium, leading to more robust designs with relatively larger minimum feature size. We optimize three components: a mode converter (MC), a 1310 nm/1550 nm wavelength duplexer, and a three-channel C-band wavelength demultiplexer for coarse wavelength division multiplexing (CWDM) application with 50 nm channel spacing. The energy constraint leads to nearly binarized structures without applying independent binarization stage. It also reduces the appearance of small features. In the MC, well-binarized design, improved insertion loss, and cross talk are obtained as a result. Furthermore, the proposed constraint improves the robustness to fabrication imperfections as shown in the duplexer design. With energy constraint optimization, the corresponding spectrum shifts for the duplexer under ± 10 nm dimensional variations are reduced from 105 nm to 55 nm and from 72 nm to 60 nm for the 1310 nm and 1550 nm channel, respectively. In the CWDM demultiplexer, robustness toward ± 10 nm fabrication error is improved by a factor of 2. The introduction of the energy constraint into topological optimization demonstrates computational gain with better-performing designs.

A high‐performance empty substrate integrated waveguide filter with mixed electric and magnetic coupling

AbstractAn empty substrate integrated waveguide (ESIW) bandpass filter with enhanced electric and magnetic coupling is proposed in this letter. ESIW uses the air as dielectric in order to reduce the dielectric loss caused by usual medium materials. However, the existence of air cavities requires at least three layers of structure, which greatly increases the difficulty of designing complex circuits with high‐performance and multiple requirements. The proposed mixed coupling structure creates the finite transmission zeros based on ESIW technology for the first time, which makes it possible to realize complex high‐performance circuits with ESIW technology. Taking advantage of the multilayer structure of the ESIW, the proposed cross‐coupling is conveniently realized with higher frequency selectivity and lower insertion loss while maintaining the substrate of three layers and the self‐encapsulation characteristics of ESIW. A fourth‐order filter with an H‐shaped slot line on the top metal plane of two adjacent air cavities is produced. A good agreement between the measurements and simulations indicates that the proposed filter achieves an insertion loss as low as 0.7 dB and the 6.1% bandwidth at 9.85‐GHz X band. It demonstrates the improvement of insertion loss and frequency selectivity, which lays a foundation for the design of complex microwave devices.

MQWC BPFS WITH IMPROVED HORMONIC REJECTION FOR RADAR APPLICATIONS

In this paper, the design and realization of optimized microstrip quarter wave coupled bandpass filters for 1.8-6.2 and 5.8-10.2 GHz frequency bands with improved harmonic rejection are discussed with the center frequencies (f<sub>0</sub>) of 4 and 6 GHz. The designed microstrip quarter wave coupled bandpass filters reject the second and third harmonics at the higher frequencies and having the improved insertion loss of < 1 dB and return losses of 36 and 38 dB, respectively. For the proposed optimized bandpass filters implementation Rogers substrate material with the relative dielectric constant of 3.55, a standard thickness of 0.020 is used and the simulation performed on high frequency simulation software. The proposed filters are fabricated and tested in a vector network analyzer, and obtained test results are compared to the simulated results.

A compact low‐cost dual‐band bandpass filter with enhanced suppression using substrate integrates suspended line technology

AbstractA compact dual‐band bandpass filter based on the substrate integrates suspended line platform is proposed in this letter. The design is implemented using low‐cost FR‐4 material, while the loss can be reduced by 3D metal connections with substrate cutout. 0.97 dB/1.6 dB improvement of insertion loss is achieved and verified at 3.45 GHz/4.9 GHz. By paralleling quarter wavelength step impedance resonators with different operating frequencies, two paths formed between source and load. Both bandwidth and location of transmission zeros can be adjusted independently. Two stubs are added working not only as feed structure but also as a stop band resonator, which can provide 20 dB out‐of‐band suppression up to 4.4f0. The obtained performances are good enough to compare with the state of art, though very low‐cost FR‐4 materials are used.

Design of Coaxial TGV Substrates; Enhancing RF Via to Via Isolation

ABSTRACT Enhanced electronic substrate design objectives for higher frequency products (5G telecom systems) can now be achieved with the use of novel coaxial-thru-via configurations in glass (TGVs). When compared with standard pillar filled thru-vias in glass, coaxial-thru-vias exhibit greater than 40dB improvement in via-to-via crosstalk isolation and 0.5dB improvement in insertion loss both at 30 GHz. Coaxial-Thru-Vias provide precise unadjusted 50 Ohm impedance matching device designs at the 5G product frequencies. The coaxial dielectric core chemistry is modifiable to tune electrical parameters to meet specific design requirements. This paper summarizes all designs, simulations, and modeling performed to date. The superior properties of coaxial vias in glass and fused silica over standard pillar vias are documented and captured in sweeps to 100 GHz. Via and pitch dimensions of 100/200 and 50/100 um have been assessed. Manufacturing methods have been demonstrated using thick film conductor materials in prototype designs. Coaxial vias can optionally be fabricated as dual-purpose configurations reducing thru-via count requirements, substrate footprints, and package/module costs.

Design of high‐isolation and low‐loss single pole double throw switch based on the triple‐coupled transformer for ultra‐wideband phased array systems

AbstractThis paper proposes a single pole double throw (SPDT) switch based on the triple‐coupled transformer. The triple‐coupled transformer utilizes a novel structure with three stacked coupled inductors which are placed in nonconcentric positions to ensure the isolation of SPDT switch. The SPDT switch obtains additional optimization space to improve insertion loss performance under the premise of reassuring isolation. The equivalent circuit model is built to interpret the mechanism of the SPDT switch and transformer. The proposed switch is implemented with the 65‐nm CMOS process, the simulated results show the isolation between input‐to‐output ports are better than 25 dB at 24–38 GHz. The proposed SPDT switch achieves a minimum insertion loss of 1.56 dB with compact chip size 625 × 370 μm2 (with PADs).

Compact empty substrate integrated waveguide with high performance and its application in microwave

A compact slow-wave empty substrate integrated waveguide (SW-ESIW) structure is proposed in this article. This structure is composed of an empty substrate with a bottom layer including several rows of internal metallised via holes. In order to decrease both the lateral and longitudinal dimensions, the slow wave effect, caused by physical separation of electric and magnetic fields, is introduced while retaining the advantages of ESIW, such as high quality factor, small insertion loss, and the advantages of SIW, such as low cost and easy processing. Compared to the classical ESIW, the proposed SW-ESIW structure achieves a size reduction of 37% and retains the triple-layer structure. At the same time, in contrast with general SW-SIW structure, which needs double layer with dielectric material, the novel waveguide obtains a significant performance improvement in insertion loss and quality factor. In the article, a fourth-order filter is designed to verify the idea that the SW-ESIW technology provides the low loss, high quality factor and compact structure. By combining the advantages of SW-SIW and ESIW technology, the proposed SW-ESIW structure can be widely applied to the microwave integrated circuits with miniaturisation and high quality factor.

Compensating deep focusing distortion for femtosecond laser inscription of low-loss optical waveguides.

Various beam shaping approaches were examined to counter the negative influence of surface aberration arising when inscribing optical waveguides deeply inside of glass with a femtosecond laser. Aberration correction was found unable to completely recover the low-loss waveguide properties, prompting a comprehensive examination of waveguides formed with focused Gaussian-Bessel beams. Diverging conical phase fronts are presented as a hybrid means of partial aberration correction to improve insertion loss and a new, to the best of our knowledge, means of asymmetric beam shaping. In this way, low-loss waveguides are presented over shallow to deep writing depth (2.8 mm) where morphological and modal properties could be further tuned with conical phase front.

Metasurface-based sound diffusers for noise barrier applications

2-D sound diffusers installed with Helmholtz resonators have been investigated as top-edge noise barrier devices. The aim of this work was to study the effect of incorporating metasurfaces in sound diffusers on the broadband performance of noise barriers. This device can be exploited to use the astounding reflection and scattering properties of resonant metasurfaces and sound diffusers to achieve improvement in insertion loss. A three-dimensional indirect boundary element study was conducted to show promising improvement in noise barrier performance.

Low insertion loss air-coupled ultrasonic transducer with parallel laminated piezoelectric structure

This work presents a low insertion loss air-coupled ultrasonic transducer with a parallel laminated piezoelectric structure. The relevant parameters of this structure are theoretically analyzed. For overcoming the enormous acoustic impedance mismatch between the piezoelectric material and air, a 1–3 connectivity piezoelectric composite, and a stack of two low acoustic impedance matching layers are adopted. The experimental results show that the insertion loss of −17.5 dB is obtained under the pitch-catch mode with the length of the air column of 50 mm by selecting a suitable air-coupled ultrasonic transducer combination. The insertion loss improvement is 3.8 dB compared with a monolayer piezoelectric structure with an identical active area.