arXiv subjects

Steven Gao

Publications and source records attributed to Steven Gao.

11 recordsLinked to original sources

arXiv2026

Flexible Wideband Filtering Monopole Antenna With Stable High Omnidirectionality

This article presents a wideband flexible filtering monopole antenna with symmetric structure for stable high omnidirectionality. It is based on a monopole antenna, which is printed on a single-layer flexible substrate. Two folded parasitic strips with different length are devised on both sides of the driven monopole, giving filtering responses in the higher and lower band without filtering circuits. Since the asymmetric filtering structure adversely affects in-band omnidirectionality, this baseline design is extended with symmetric filtering structure to improve omnidirectionality and bandwidth. In the proposed design, a pair of parasitic strips are devised on the both sides of monopole antenna symmetrically, achieving a radiation null in the higher band. Then, by loading a pair of folded parasitic strips on the both sides of feed line with slotted metal ground, a radiation null is realized in the lower band. Besides, the driven monopole is slotted symmetrically for wideband operation. By adopting a fully symmetric filtering structure, the proposed design effectively suppresses the impact of the parasitic elements on the in-band omnidirectional radiation pattern, thereby achieving high omnidirectionality. Furthermore, the proposed antenna exhibits stable performance under different bending radii. To verify our design concept, an antenna prototype is fabricated. Both the flat and bent antennas are measured. The results show that the proposed antenna has a -10 dB impedance bandwidth of 45.6%, an in-band gain about 2 dBi, and an out-of-band radiation suppression more than 11 dB. The measured omnidirectionality has variations less than 0.8 dB without bending and 1 dB with a bending radius of 30 mm. This design offers several advantages including stable high omnidirectionality across a wide bandwidth, flexible conformal capability, and filtering property.

eess.SP↗

arXiv2026

Flexible Wearable Filtering Antenna With Stable Performance for IoT Devices

In this article, a flexible and lightweight filtering wearable antenna without extra circuits is presented. The proposed antenna starts from a flexible directional antenna with lightweight structure, which includes a layer of ultra-thin flexible substrate, a metal ground layer, and a flexible foam layer sandwiched between them. Then, by introducing two pairs of vertical slots to the radiation patch printed on the flexible substrate, two radiation nulls are realized at both band edges without extra circuits. Moreover, to mitigate the deterioration of in-band radiation under different curvature, a pair of inverted Fshaped slots are loaded on the radiation patch. The coupling of Fshaped slots suppresses non-radiated lateral current components along the curvature direction, maintaining stable performance after bending. In addition, deformation analysis of the proposed antenna with a three-layer human tissue model under different bending radii is carefully carried out, showing stable bandwidth, effective out-of-band radiation suppression, and low specific absorption rate (SAR) value. To verify this method, a prototype is fabricated. Measurements are conducted both in free space and conformal on the curved body tissue. The results show that the proposed antenna achieves a bandwidth from 2.7 GHz to 3 GHz, an out-of-band radiation suppression more than 11 dB with maxmium suppression of 23 dB, and an average gain of 8.5 dBi. As a flexible wearable antenna with stable performance and integrated reliable filtering features, it has several advantages including flexible wearable structure, stable filtering properties, lightweight characteristic, and low SAR. This makes it an excellent candidate for wearable IoT applications.

eess.SP↗

arXiv2026

M*: A Modular, Extensible, Serving System for Multimodal Models

We are entering a new era of composite model architectures that integrate diverse components such as vision encoders, language backbones, diffusion and flow heads, audio codecs, action generators, and world-model predictors. Such architectures underpin a broad class of multimodal models, including unified multimodal models, omni models, speech-language models, vision-language-action policies, and world models. However, existing model serving frameworks were built on narrow assumptions about model structure, making them ill-suited to accommodate this new architectural diversity. Here we present M*, a universal serving system for efficient serving of composite AI models. M* represents models as dataflow graphs, processing requests spanning diverse modalities and tasks as traversals over these graphs. The core insight is a modular abstraction that supports arbitrary composition of model components, flexible placement onto a physical cluster, and model-agnostic optimizations within a distributed runtime. We call this abstraction the Walk Graph and show how it can concisely capture composite models from a broad range of families. We instantiate M* on representative models and find that it achieves, on average, 20% lower end-to-end latency than vLLM-Omni for text-to-image workloads on BAGEL, while delivering up to 2.9x lower real-time factor and 2.7x higher throughput for text-to-speech workloads on Qwen3-Omni. M* also outperforms the V-JEPA 2-AC rollout baseline for robotic planning by up to 12.5x. Thus, our work paves the road towards more efficient serving of complex models with minimal developer effort.

cs.LG↗

arXiv2025

Dual-Band Flexible Endfire Filtering Antenna With Conformal Capability for Emergency Communication Applications

In this letter, a single-layer dual-band flexible conformal filtering endfire antenna is presented. The proposed antenna is based on two co-designed folded dipoles (FDs) working at two frequencies, where the lower-frequency FD acts as a reflector for the higher-frequency one. Then, by devising an additional reflector for lower-frequency FD, dual-band endfire radiation is realized. Parasitic strips are deliberately introduced around the FDs to generate electric coupling and magnetic coupling in the two operating bands, resulting in significant filtering performance with four radiation nulls. With flexible structure and single-layer configuration, the antenna design exhibits flexible conformability with cylindrical surfaces of diverse diameters, thereby enabling seamless integration into scalable emergency communication systems. To verify our design concept, an antenna prototype is fabricated and measured. The measured working frequency ranges from 1.37 to 1.45 GHz and 1.89 to 2.07 GHz. Out-of-band radiation suppression more than 11 dB is achieved under different bending radii. The proposed design offers several advantages including dual-band endfire filtering radiation, flexible conformability and low-profile.

eess.SY↗

arXiv2025

Novel Physics-Aware Attention-Based Machine Learning Approach for Mutual Coupling Modeling

This article presents a physics-aware convolutional long short-term memory (PC-LSTM) network for efficient and accurate extraction of mutual impedance matrices in dipole antenna arrays. By reinterpreting the Green's function through a physics-aware neural network and embedding it into an adaptive loss function, the proposed machine learning-based approach achieves enhanced physical interpretability in mutual coupling modeling. Also, an attention mechanism is carefully designed to calibrate complex-valued features by fusing the real and imaginary parts of the Green's function matrix. These fused representations are then processed by a convolutional long short-term memory network, and the impedance matrix of the linear antenna array can be finally derived. Validation against five benchmarks underscores the efficacy of the proposed approach, demonstrating accurate impedance extraction with up to a 7x speedup compared to CST Microwave Studio, making it a fast alternative to full-wave simulations for mutual coupling characterization.

eess.SP↗

arXiv2025

A High-Efficiency Reconfigurable Bidirectional Array Antenna Based on Transmit-Reflect Switchable Metasurface

This paper proposes a reconfigurable bidirectional array antenna with high-efficiency radiations and flexible beam-switching capability by employing a novel transmit-reflect switchable metasurface (TRSM). To realize the electromagnetic (EM) wave transmitted or reflected manipulation, a dedicated transmit-reflect switch layer (TRSL) with periodically soldered PIN diodes is introduced between two transmitted metasurfaces. By switching ON/OFF the embedded diodes, the TRSL performs as a mesh-type ground layer or polarization-grid layer, exhibiting a reflect or transmit property to the incident wave respectively. Further, utilizing the above TRSM configuration in conjunction with a microstrip feed antenna, bidirectional radiations are obtained at the same frequency and polarization. To further reduce the number of PIN diodes and control complexity, an enhanced TRSM using a single diode to control two unit cells is also investigated, resulting in half PIN diodes reduction. Since the bidirectional beam-switching is achieved by only controlling PIN diodes integrated in the ground plane instead of directly acting on the radiation element, which reduces insertion loss and avoids phase quantization errors, the proposed antenna can maintain a high aperture efficiency. To verify this concept, a prototype was designed, fabricated, and measured, demonstrating a successful realization of backward and forward patterns with peak gains of 22.3 and 22.1 dBi, and aperture efficiencies of 47.2% and 43.8%. The 3-dB gain bandwidths of reflected and transmitted modes are 13.7% and 12.3%. This antenna has the advantages of high gain, high aperture efficiency, simple configuration, cost-effectiveness, and flexible and digital beam control.

eess.SY↗

arXiv2024

Hybrid Voxel Formats for Efficient Ray Tracing

Voxels are a geometric representation used for rendering volumes, multi-resolution models, and indirect lighting effects. Since the memory consumption of uncompressed voxel volumes scales cubically with resolution, past works have introduced data structures for exploiting spatial sparsity and homogeneity to compress volumes and accelerate ray tracing. However, these works don't systematically evaluate the trade-off between compression and ray intersection performance for a variety of storage formats. We show that a hierarchical combination of voxel formats can achieve Pareto optimal trade-offs between memory consumption and rendering speed. We present a formulation of "hybrid" voxel formats, where each level of a hierarchical format can have a different structure. For evaluation, we implement a metaprogramming system to automatically generate construction and ray intersection code for arbitrary hybrid formats. We also identify transformations on these formats that can improve compression and rendering performance. We evaluate this system with several models and hybrid formats, demonstrating that compared to standalone base formats, hybrid formats achieve a new Pareto frontier in ray intersection performance and storage cost.

cs.GR↗

arXiv2024

Multibeam Hybrid Transmitarray Based on Polarization Rotating Metasurface With Reconfigurable Bidirectional Radiation

This paper proposes a bidirectional multibeam hybrid transmitarray (HTA) employing a transmission polarization-rotating metasurface (TPRM). A novel configuration is introduced to facilitate bidirectional beam scanning by combining the transmitarray (TA) and folded-transmitarray (FTA). To accomplish the reconfiguration of both unidirectional and bidirectional radiation states in the +z, -z, and +/-z directions, a polarization switchable multi-feed array (MFA) is placed at the focal plane between the TA and FTA, radiating x-polarization, y-polarization, and 45-degree oblique polarization waves, respectively. Meanwhile, the proposed antenna can achieve multibeam radiation in the three aforementioned states by switching the polarization of the MFA. To demonstrate the operating principle, a prototype has been designed, simulated, and fabricated. The measured results agree well with the simulated results. The simulated and measured results indicate that the proposed design can generate reconfigurable multibeam in both forward and backward directions, either separately or simultaneously. In the unidirectional states, forward and backward beam scanning is achieved within an angular range of +/-30{\deg} and +/-22{\deg}, respectively, with peak gains of 23.6 dBi and 23.1 dBi. A simultaneous forward and backward beam scanning of +/-40{\deg} and +/-22{\deg} is achieved in the hybrid radiation state, with peak gains of 19.4 dBi and 19.3 dBi, respectively. The proposed antenna array design offers several advantages, including bidirectional low-loss beam scanning, a simple structure, low power consumption, and a low profile.

eess.SY↗

arXiv2023

A Multifunctional Array System Based on Adjustable-Phase Antenna for Wireless Communications

In this work, an innovative method for controlling the current distribution of the radiating patch by adjusting the input phase is investigated to achieve both pattern and polarization reconfigurable characteristics for the multifunction. A compact and low-profile antenna with four fed ports is designed to implement the proposed method, which can operate linear, right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) with different beam directions in the operating band from 4.0 to 5.0 GHz. Even more, a four-by-four passive planar array is designed and fabricated based on this antenna element, which can scan the coverage of 70{\deg} with low gain fluctuation and low sidelobe with dual-polarization. Meanwhile, it can realize the wide-angle scanning capability up to 60{\deg} with low sidelobe with RHCP and LHCP. More important, the dual- and triple-beam with different directions can be obtained by the proposed array. Good agreement has been shown between measured and simulated results. Therefore, the proposed antenna is a good solution for wireless communication systems because of its simple-configuration, multifunction, and beamforming capability.

physics.app-ph↗

arXiv2022

Design of Switchable Frequency-Selective Rasorber with A-R-A-T or A-T-A-R Operating Modes

This work presents a switchable frequency-selective rasorber (SFSR) with two operating modes. Switching from transmission to reflection can be achieved by appropriately adding feeders and PIN diodes based on cascaded two-dimensional lossy and lossless frequency-selective surface (FSS) screens. The proposed SFSR can realize out-of-band absorption. Analysis of the equivalent circuit model (ECM) can be useful for achieving a switchable rasorber. As the state of the PIN diodes changes, the working state of the SFSR can be switched from low-frequency reflection and high-frequency transmission to low-frequency transmission and high-frequency reflection, respectively. In the final-revision simulation of the working band of the SFSR, in the ON state, reflection and transmission peaks of -0.55 dB at 4.06 GHz and -0.52 dB at 5.97 GHz, respectively, are achieved; in the OFF state, the transmission and reflection peaks of -0.31 dB at 4.04GHz and -0.26 dB at 6.01 GHz, respectively, are obtained. A prototype sample is developed and validated. The results are in good agreement with those of the full-wave simulation. The proposed design can be used in intelligent anti-jamming communication.

physics.app-ph↗

arXiv2021

Band-Notched Frequency-Selective Absorber with Polarization Rotation Function

This paper presents the theoretical analysis, design, simulations, and experimental verification of a novel band-notched frequency-selective absorber (BFSA) with polarization rotation function and absorption out-of-band. The BFSA consists of multiple layers including one lossy layer, one polarization-rotary layer and an air layer. The lossy layer is loaded with lumped resistances for obtaining a wide absorption band. A new four-port equivalent circuit model (ECM) with lossy layer is developed for providing theoretical analysis. The BFSA realizes -0.41dB cross-polarization reflection at 4.5GHz. In the upper and lower bands, the BFSA realizes a broad absorption function from 2.2GHz to 4.1GHz and 5.03GHz to 6.5GHz. The fractional bandwidth of co-polarization reflection is 98.8% with 10dB reflection reduction. The full-wave simulation, ECM, and experimental measurements are conducted to validate the polarization conversion of the band-notched absorbers, and good agreement between theory and measurement results is observed.

physics.app-ph↗