PIER Letters | PIER Journals

2026-08-07

PIER Letters

Vol. 131, 34-39, 2026

doi:10.2528/PIERL26052102

download: 117

Design of Broadband Gradient-Radius Magnetic Induction Antennas

Mingxuan Hu and Lihua Li

To address the challenge of limited bandwidth in magnetic induction communication, this study proposes a magnetic induction antenna adopted a gradient-radius structure. The antenna adopts a discretized gradient-radius design, which effectively broadens the system bandwidth by increasing the antenna's resistance-to-inductance ratio. The study integrates theoretical analysis, simulation, and experimental testing to systematically investigate the effects of different taper ratio structures on resistance, inductance, and bandwidth. Experimental results demonstrated that the gradient-radius structure can significantly extend the bandwidth, and the extension effect became stronger as the taper ratio increased. Meanwhile, combined with simulation and experimental data, the attenuation effect of this structure on the near-zone magnetic field was evaluated, verifying that the bandwidth improvement came at the cost of coupling strength. Specifically, when the bandwidth was extended to nearly twice its original value, the received signal strength decreased by approximately 6.4 dBm. This study provides a simple and practical implementation approach for the broadband design of magnetic induction communication systems.

Design of Broadband Gradient-Radius Magnetic Induction Antennas

2026-07-11

PIER Letters

Vol. 131, 26-33, 2026

doi:10.2528/PIERL26041807

download: 131

Front-to-Back Ratio Improvement of Wideband Circularly Polarized Antenna with Tilted-Slot Fences

Bei-Wen Lin, Tian-Yuan Gao and Rui Wu

This paper presents a wideband circularly polarized (CP) antenna featuring a significantly enhanced front-to-back ratio (FBR). The proposed design employs a composite structure that integrates a dipole with a loop resonator and is fabricated using a multilayer architecture. The top layer is a dielectric substrate loaded with a cyclic zigzag patch. The middle layer contains an L-shaped radiating patch with etched rectangular grooves, and the bottom layer comprises a metal ground plane and surrounding vertically tilted-slot fences. Circular polarization is achieved by exciting orthogonal degenerate modes via strategic rectangular-groove perturbations that work in concert with the loop resonator's inherent asymmetric current path. The tilted-slot fences, in conjunction with the zigzag patch layer, function collectively to suppress backward radiation and improve the FBR. Measured results demonstrate that the antenna achieves a 3 dB axial ratio (AR) bandwidth of 54% from 2.45 to 4.3 GHz, a stable FBR of more than 27.5 dB with 2.5 dB variation, and a peak gain of 9.3 dBic. This design offers a high-performance, planar antenna solution well-suited for satellite communication and radar systems.

Front-to-Back Ratio Improvement of Wideband Circularly Polarized Antenna with Tilted-Slot Fences

2026-07-06

PIER Letters

Vol. 131, 18-25, 2026

doi:10.2528/PIERL26040203

download: 199

A High-Reliability Fiber-Optic Transmission System with Hybrid Power Supply

Lichao Zhang, Zheng Sun, Qi Zhang and Lihua Shi

Conventional fiber-optic measurement systems for pulsed electromagnetic fields are limited by power-supply instability due to the temperature sensitivity of photocells. To address this issue, we developed a highly reliable broadband fiber-optic transmission system featuring a hybrid power supply. In our design, a lithium battery serves as the primary power source for the optical transmitter, while a compact photocell provides short-term supplemental power and simultaneously recharges the battery. An additional shunt resistor (5-50 Ω) is added to avoid damping oscillations. Results: The system achieves a -3 dB bandwidth from 5 Hz to 122 MHz. The optical transmitter volume is reduced to one-fifth of a previous design. Ten repeated electric-field measurements show relative errors below 3%. Conclusion: The proposed system offers stable operation, low power consumption, wide dynamic range, and strong anti-interference capability, making it well-suited for harsh electromagnetic environments.

A High-Reliability Fiber-Optic Transmission System with Hybrid Power Supply

2026-06-05

PIER Letters

Vol. 131, 9-17, 2026

doi:10.2528/PIERL26041704

download: 235

A Compact Four-Port Circularly Polarized MIMO Antenna Using a Polarization Conversion Superstrate

Jingchang Nan, Siyao Zhao and Yifei Wang

A compact four-port circularly polarized multiple-input multiple-output (CP-MIMO) antenna with a dual-layer architecture is proposed for low-altitude communication applications. In compact MIMO arrays of CP-capable monopole elements, strong mutual coupling makes stable CP radiation difficult to achieve. To address this issue, the proposed antenna uses a lower layer for dual-polarized MIMO generation and an upper layer for polarization conversion. The antenna is fabricated on two FR-4 substrates with an overall size of 0.85λ × 0.85λ × 0.084λ. In the lower layer, a dual-polarized feed backplane (DPFB) forms a ±45° dual-polarized MIMO array with port isolation exceeding 17 dB. In the upper layer, a polarization conversion superstrate (PCS) converts the incident dual-polarized waves into CP radiation. The PCS extends the impedance bandwidth by 36%, from 7.55 to 10.08 GHz, and enables LHCP radiation with a 3 dB AR bandwidth of 8.22-8.89 GHz. A gain enhancement of 48% is also achieved. Measured results verify the design and show good MIMO diversity performance.

A Compact Four-Port Circularly Polarized MIMO Antenna Using a Polarization Conversion Superstrate

2026-05-17

PIER Letters

Vol. 131, 1-8, 2026

doi:10.2528/PIERL26021601

download: 308

Terahertz Wave Shielding of Carbon Nanotube-Organic Silicone

Jin-Rong Li, Jiu-Sheng Li and Ri-Hui Xiong

We have developed a carbon nanotube organic silicone rubber (CNT-OSR) composite medium, composed of methyl trifluoropropyl silicone rubber as the matrix, with different mass fractions of carbon nanotubes added and formed through vulcanization using a bis (cyclopentadiene) vulcanizing agent. The CNT-OSR composite media with carbon nanotube contents of 2wt%, 5wt%, and 8wt% were tested, and the maximum absorption and shielding efficiencies of the media for terahertz waves in the 0.5-1.0 THz frequency range were found to be 69.77 dB, 76.28 dB, and 63.69 dB, respectively. Through impedance matching theory analysis, the absorption and shielding effectiveness of the medium for terahertz waves were confirmed. Additionally, the composite medium exhibits excellent hydrophobic properties. It provides a simple and feasible approach for developing lightweight, efficient, and multifunctional terahertz wave absorbing and shielding materials for the next generation of terahertz wireless communication.