PIER M | PIER Journals

2026-06-22

PIER M

Vol. 138, 87-96, 2026

doi:10.2528/PIERM26051701

download: 44

Fractal Geometry-Based Triple Band Compact MIMO Antenna with Gain Enhancement Using Frequency Selective Surface

Suvro Kundu, Dheeraj Pandey, Tej Raj and Surajit Kundu

A compact, fractal-shaped, triple-band multiple-input multiple-output (MIMO) antenna integrated with a frequency-selective surface (FSS) to improve radiation characteristics is presented in this work. The proposed design employs a fractal-based radiating element to achieve multiband characteristics while minimizing the size. The four-port MIMO configuration is developed from a single-port radiator using an orthogonal arrangement to improve the port isolation. A central square slot is introduced to suppress mutual coupling by interrupting surface current paths, thereby improving inter-element isolation across all operating bands. To enhance the gain, a multi-resonant uniplanar frequency selective surface (FSS) is designed and positioned to act as a partially reflective surface. The FSS unit cell, modelled using an equivalent circuit approach, exhibits three distinct stopbands corresponding to the desired operating frequencies of 2.7-3.5 GHz, 5.5-8.4 GHz and 9.3-10.9 GHz. The combined antenna-FSS configuration, with the overall electrical size of (0.5×0.5×0.235)λ, demonstrates a gain improvement of 3-4 dBi in all bands, without compromising bandwidth. With three frequency bands of 2.5-3.875 GHz, 5.25-6.05 GHz and 8.6-10.6 GHz, the proposed MIMO antenna achieves good MIMO characteristics, making it suitable for modern high-speed wireless technologies including sub-6-GHz 5G (WiMAX), WLAN, and ISM bands.

Fractal Geometry-based Triple Band Compact MIMO Antenna with Gain Enhancement using Frequency Selective Surface

2026-06-18

PIER M

Vol. 138, 75-86, 2026

doi:10.2528/PIERM26043004

download: 73

High-Accuracy Dual-Split-Ring-Resonator Microwave Sensor for Permittivity Characterization and Defect Detection in Solid Materials

Tata Setiawan, Syah Alam, Indra Surjati, Lydia Sari, Yuli Kurnia Ningsih, Teguh Firmansyah, Yohanes Galih Adhiyoga, Juliano Katrib and Zahriladha Zakaria

This research proposes a microwave sensor based on a dual-split-ring-resonator (DSRR) structure designed for the detection of the permittivity of solid samples and defective materials. The DSRR structure was chosen because it has a high-quality factor Q, is highly sensitive to changes in permittivity, and is easy to integrate into a planar substrate. The designed sensor is fabricated using a Rogers RO5880 substrate having a dielectric constant ε_r of 2.2, tanδ of 0.0009, and a substrate thickness h of 1.58; the sensor operates in the frequency range of 1 GHz-2 GHz and adopts a dual-port configuration by observing changes in the transmission parameter S₂₁. The measurements used the perturbation theory method, where the resonance frequency shift occurs when a material is inserted into the sensor area. This sensor area is defined as the location of maximum electric field concentration within the resonator. Polynomial equations are derived for measurements on dielectric materials with known permittivity values ranging from 1 to 9.8. The proposed sensor demonstrates high performance, with a measured accuracy of 99.6%, a normalized sensitivity of 2.6%, and a frequency detection resolution (FDR) of 0.026 GHz. These results indicate that the sensor using the DSRR method with hole integration offers reliable and precise permittivity detection, particularly for detecting defects in materials.

High-Accuracy Dual-Split-Ring-Resonator Microwave Sensor for Permittivity Characterization and Defect Detection in Solid Materials

2026-06-13

PIER M

Vol. 138, 65-74, 2026

doi:10.2528/PIERM26042706

download: 93

Gain Enhancement and Reduced Isolation of 4-Port Orthogonal Multiple-Input-Multiple-Output Antennas Based on Metamaterial for 5G Applications

Boddapati Naga Prasanna and Thokala Kalpalatha Reddy

As the need for rapid data transmission and dependable wireless networks grows, so does the need for advanced antenna technology. This has become a major focus of modern communication technologies. This paper describes the design of a 4-port multiple-input multiple-output (MIMO) microstrip patch working at 28 GHz in the Ka-band. This antenna is fabricated on a substrate measuring 21 × 21 × 3.97 mm³, composed of FR4, foam, and RT/Duroid 5880. It uses a microstrip feed. Performance enhancements are achieved by positioning the feeds orthogonally, incorporating a U-shaped slot into the MIMO antennas, and implementing a superstrate made of metamaterial (MTM) elements. Additionally, a single-layer MTM superstrate with rectangular slots is created to improve gain while keeping good impedance matching. The design process systematically improves gain and mutual coupling while keeping the overall size compact. The specific challenge addressed by the design is to improve peak gain and radiation efficiency by employing MTM elements operating at 28 GHz. The 4-port MIMO antenna achieves an impedance bandwidth (IB) of 27.11-29.21 GHz, with a peak gain of 14.05 dB, respectively. This antenna is used in next-generation communication systems, vehicular networks, and 5G systems.

Gain Enhancement and Reduced Isolation of 4-Port Orthogonal Multiple-Input-Multiple-Output Antennas Based on Metamaterial for 5G Applications

2026-06-12

PIER M

Vol. 138, 55-64, 2026

doi:10.2528/PIERM26032606

download: 87

Broadband and Switchable VO2-Based BI-Functional THz Polarization Converter Combined with a Deep-Learning-Assisted Design Method

Haohan Xie, Shuning Wei, Wenting Qu, Xinlei Zhang, Chenshan Le, Jinlin Li and Jun Dong

This study presents a broadband, switchable, and bi-functional terahertz device based on the phase transition of vanadium dioxide (VO₂). When VO₂ is in the metallic state, the device operates as a linear polarization converter (LPC). When VO₂ transitions to the insulating state, the device functions as a broadband linear-to-circular polarization converter (LTC-PC). Numerical simulations are conducted to verify the device performance. To further optimize metamaterial performance and accelerate the design process, a deep learning framework that integrates convolutional neural networks (CNNs) and the Transformer architecture via an adaptive mechanism is proposed. Numerical simulations indicate that this LPC achieves a polarization conversion ratio (PCR) exceeding 90% across the 1.92-2.93 THz band and maintains angular stability for incidence angles up to 50°. The LTC-PC operates effectively within the 2.40-4.33 THz range. Featuring broadband operation and bi-functional capabilities, the converter holds significant potential for applications in terahertz imaging, sensing, solar energy harvesting, and communications.

Broadband and Switchable VO2-Based Bi-Functional THz Polarization Converter Combined with a Deep-Learning-Assisted Design Method

2026-05-24

PIER M

Vol. 138, 44-54, 2026

doi:10.2528/PIERM26040704

download: 117

Electromagnetic Parameter Extraction for Asymmetric Metamaterials under Oblique Incidence

Meiling Li, Zelong Fan, Dan Zeng and Zixuan Yi

An improved scattering (S-)parameters extraction method, based on the forward and backward propagating waves under oblique incidence on metamaterials (MMs), is proposed to accurately extract electromagnetic parameters for asymmetric uniaxial MMs in a broad frequency range. The proposed approach equivalently models asymmetric MMs as two isotropic media (distinct from the 3 × 3 matrix-form anisotropic medium). To validate the effectiveness of the proposed method, a low-thickness asymmetric absorptive frequency-selective surface (AFSS) and a high-thickness 7-layer absorber were designed, simulated, and analyzed.

Electromagnetic Parameter Extraction for Asymmetric Metamaterials under Oblique Incidence

2026-05-19

PIER M

Vol. 138, 33-43, 2026

doi:10.2528/PIERM26020604

download: 121

Frequency-Tunable and Attenuation-Controlled Sub-6 GHz Antenna Using Miniaturized Multilayer Graphene Pads

Pandillapalli Janardhana Reddy and Gummadi Kameswari

This paper presents a wideband four-port microstrip antenna operating from 2.75 GHz to 6.75 GHz with frequency reconfigurability and controllable notch characteristics. The antenna employs an asymmetric radiating structure to realize circular polarization around 5.5 GHz, while multilayer graphene(MLG) pads are introduced to enable bias-controlled frequency tuning and adjustable band rejection. The four-port configuration, implemented on an RT/Duroid 5880 substrate (ε_r = 2.2, thickness = 1.6 mm), achieves inter-element isolation better than 20 dB without additional decoupling structures. The proposed design also exhibits strong diversity performance with an envelope correlation coefficient below 0.02 and diversity gain above 9.97 dB. The results demonstrate that the proposed antenna provides a compact and low-complexity solution for wideband and reconfigurable sub-6 GHz wireless communication applications.

Frequency-Tunable and Attenuation-Controlled Sub-6 GHz Antenna Using Miniaturized Multilayer Graphene Pads

2026-05-03

PIER M

Vol. 138, 22-32, 2026

doi:10.2528/PIERM26031804

download: 262

A Compact Shared-Aperture MIMO Antenna System for Microwave and Millimeter-Wave V2X Communications

Xiao-Mei Ni, Xin-Hao Ding, Zhen Tan, Xin Wang and Ming-Zhu Du

To meet the stringent space constraints and diverse connectivity requirements of modern intelligent connected vehicles, a compact MIMO antenna system designed for microwave and millimeter-wave (mm-wave) vehicle-to-everything (V2X) communications is presented. The proposed antenna features a compact footprint adaptable for integration into space-limited automotive modules, such as shark fin antenna housings. By employing a structure reuse technique, the system integrates a four-element microwave MIMO array and two orthogonal mm-wave phased arrays within a size of 30 mm × 30 mm × 2 mm. In the microwave band, a parasitic patch is introduced to achieve dual-mode resonance, ensuring a wide bandwidth for reliable control signaling. Two orthogonal rows of metallized cavities serve a dual purpose: acting as decoupling structures for the microwave MIMO system and functioning as mm-wave arrays to enable two-dimensional beam scanning. This capability is crucial for overcoming blockage effects in dynamic vehicular environments. Experimental results demonstrate that the proposed antenna achieves wide coverage in the microwave band (4.62-5.11 GHz) and high-gain beam scanning (±40°) in the mm-wave band (25.8-30.4 GHz). The measured isolation exceeds 17 dB with an envelope correlation coefficient below 0.11, validating its suitability for next-generation vehicle terminals.

A Compact Shared-Aperture MIMO Antenna System for Microwave and Millimeter-Wave V2X Communications

2026-04-27

PIER M

Vol. 138, 10-21, 2026

doi:10.2528/PIERM26010103

download: 178

Performance Evaluation of a Dual-Band h -Shaped Metamaterial Perfect Absorber with Polarization-Insensitive Characteristics for Satellite Communication Applications

Vanam Chinna Narasimhulu, Govardhani Immadi and Madhavareddy Venkata Narayana

A compact, double split-ring H-shaped resonator-based polarization-independent dual-band metamaterial microwave absorber (MMA) with an outstanding absorption efficiency was designed and analyzed for satellite communication applications. The H-shaped resonator-based unit cell was printed on an FR4 material using copper as the conducting material. Copper material was chosen for the radiating patch and the ground plane. A detailed parametric analysis was performed by tuning the geometrical parameters of the H-shaped MMA to achieve dual absorption bands with broad bandwidth and high absorptivity. The recommended H-shaped absorber exhibits dual absorption bandwidths of 710 MHz and 1630 MHz with FBW of 22.95% and 19.35%. Furthermore, it maintains an absorptivity of greater than 90% across the entire spectrum of dual operating bands with almost perfect absorption of 99.99% at the resonant frequencies (3.17 GHz, 7.78 GHz) of each band. The MMA maintains an area of 0.09λ × 0.09λ. A simulated absorber model was fabricated, and the results have been tested using an Anritsu Combinational Analyzer (MS2037C) for experimental validation. The simulated and tested outcomes of the developed prototype are in strong alignment, rendering the absorber suitable for S-band and LEO and geostationary satellite uplinks/downlinks, with specific bands often at 7.145-7.235 GHz (uplink) and 8.4-8.5 GHz (downlink).

Performance Evaluation of a Dual-band H-shaped Metamaterial Perfect Absorber with Polarization-insensitive Characteristics for Satellite Communication Applications

2026-04-14

PIER M

Vol. 138, 1-9, 2026

doi:10.2528/PIERM26021201

download: 231

A Dual-Band Shared-Aperture Antenna Employing a Meshed Patch and AMC-Backed Fabry-Perot Cavity

Chaoyuan Guo, Zhihan Liu and Yufeng Liu

A low-profile, dual-band, shared-aperture antenna with a large frequency ratio is presented, based on a meshed patch and an AMC-backed Fabry-Perot (F-P) cavity. By taking advantage of the weak frequency sensitivity of grid slotting in meshed patches, the upper meshed patch is utilized as both the parasitic patch for the low-frequency antenna and the partially reflective surface (PRS) for the high-frequency F-P cavity, thereby simplifying the overall structure. Meanwhile, the AMC ground is employed to control the reflection phase and reduce the cavity height to λ/4, which enables both antennas to share the same aperture within an 8-mm profile. A prototype is fabricated and tested at 1.6 GHz and 15.14-15.46 GHz. Measured results demonstrate a frequency ratio of 1:9.6, a peak gain of 6.2 dBi at 1.6 GHz, a peak gain of 11.8 dBi in the high-frequency band, and a port isolation better than 17 dB. The proposed antenna features compact size, low profile, and efficient structural reuse, making it attractive for integrated multi-band communication systems.