PIER Letters | PIER Journals

2026-11-05

PIER Letters

Vol. 132, 63-71, 2026

DOI:10.2528/PIERL26091601

download: 12

High-Efficiency Hybrid Continuous Mode Power Amplifier Based on Power-Dependent Input Nonlinearity

Pingfan Xu, Chuicai Rong, Fubing Ding, Mingxuan Guo, Baoli Chen, Ziye Zheng, Hongxin Ma and Yunpei Feng

This study proposes an input-output waveform-synthesis method for high-efficiency power amplifiers (PAs) operating at multiple power levels. A power-dependent complex input-nonlinearity factor captures gate-voltage distortion caused by the nonlinear gate-source capacitance, linking input second-harmonic impedance to conduction interval and drain-current harmonics. The theoretical high-efficiency load-impedance regions are derived from the prescribed waveforms at selected input-power levels within 27-30 dBm. Their intersection defines common impedance targets for synthesizing a fixed harmonic-control network. To validate the proposed method, this work designs and fabricates a hybrid continuous mode (HCM) power amplifier centered at 3.5 GHz. Under continuous-wave (CW) excitation at 3.5 GHz, the power amplifier achieves a drain efficiency (DE) of 78.2%, a power-added efficiency (PAE) of 72.2%, an output power of 40.1 dBm, and a gain of 11.1 dB. Over 3.35-3.65 GHz, the measured DE ranges from 68.8% to 78.2%.

High-Efficiency Hybrid Continuous Mode Power Amplifier Based on Power-Dependent Input Nonlinearity

2026-11-04

PIER Letters

Vol. 132, 54-62, 2026

DOI:10.2528/PIERL26091303

download: 6

High-Isolation Four-Port Circularly Polarized MIMO Antenna Using a Metasurface Ground Plane

Jingchang Nan, Fengjun Liang and Shuming Liu

The proposed CP antenna element employs a microstrip feed and a 45° rectangular slot to excite two orthogonal modes with an approximately 90° phase difference, realizing circular polarization. Based on this element, a four-port CP MIMO antenna is constructed, and a 5 × 5 metasurface array (M-array) is integrated into the ground plane to suppress mutual coupling between adjacent antenna elements. The introduced M-array provides additional electromagnetic-wave control paths and suppresses surface-wave propagation between adjacent antenna elements, reducing mutual coupling and improving the radiation performance of the CP MIMO antenna. At 10.8 GHz, the dimensions of the CP MIMO antenna are 32 mm × 32 mm × 1.6 mm. Simulated results show that the CP MIMO antenna with the M-array offers a frequency range of 20.6% (10.5 to 12.7 GHz), an inter-port isolation exceeding 40 dB with a peak value of approximately 64 dB, a 4.7% overlapping 3 dB axial ratio bandwidth from 10.5 to 11 GHz, and a high gain of 9.75 dBi. Diversity metrics ensure good diversity performance, including an envelope correlation coefficient (ECC) below 0.001, a diversity gain (DG) of approximately 10 dB, a channel capacity loss (CCL) below 0.2 bits/Hz, and a total active reflection coefficient (TARC) below -10 dB. The proposed CP MIMO antenna operates over the 10.5-12.7 GHz frequency range, which spans the upper portion of the X-band and the lower portion of the Ku-band. The measured results show good agreement with the simulated ones, validating the proposed CP MIMO antenna for radar applications.

High-Isolation Four-Port Circularly Polarized MIMO Antenna Using a Metasurface Ground Plane

2026-10-30

PIER Letters

Vol. 132, 43-53, 2026

DOI:10.2528/PIERL26070501

download: 9

A Magnetic Bead-Amplified SPR/SERS Dual-Modality Assay for EV-Associated TGF-β1 as a Companion Diagnostic for CAR-T Therapy

Sailing He, Faten Bashar Kamal Eddin, Abdur Rahim, Wen Lei, Qunyi Guo, Kaixin Zheng, Raheel Ahmed Janjua and Wenda Luo

Chimeric antigen receptor (CAR)-T cell therapy has achieved remarkable success in hematologic malignancies, yet its efficacy in solid tumors remains limited by the immunosuppressive tumor microenvironment. The recent clinical breakthrough of GPC3-specific dnTGFβRII-armored CAR-T (C-CAR031) has demonstrated encouraging responses, but a substantial fraction of patients still fails to achieve durable remission. A key resistance mechanism is the overwhelming burden of TGF-β1 in the tumor microenvironment, which may overwhelm the dnTGFβRII ``armor'' and lead to CAR-T exhaustion. Here, we report a magnetic bead-amplified phase-interrogated surface plasmon resonance (SPR) biosensor for the quantitative detection of TGF-β1 on tumor-derived extracellular vesicles (TEVs) in patient plasma. The platform combines anti-TGF-β1 antibody-conjugated magnetic beads for EV enrichment with a ZnSe/GO SPR chip functionalized with anti-TGF-β1 for real-time, label-free detection. The assay achieved a limit of detection (LOD) of 0.051 pg/mL with a linear range spanning 10^-1-10⁵ pg/mL (R² = 0.9894). In vitro, CAR-T + Raji co-culture significantly increased TGF-β1⁺ EVs compared with all control groups, peaking at 24 h. Orthogonal surface-enhanced Raman scattering (SERS) validation at 72 h independently confirmed this trend, exhibiting characteristic R6G reporter peaks at ~1367 cm^-1 and ~1520 cm^-1, and strictly following the hierarchy of CAR-T + Raji > Raji > CAR-T > CT + Raji > Healthy controls. Clinically, four CAR-T patients showed marked elevations in plasma EV-associated TGF-β1 (7.2-21.3 fold over baseline), with peak concentrations of 77.97, 69.22, 49.02, and 57.30 pg/mL for P1-P4, respectively. This platform provides a companion diagnostic tool to identify patients with high TGF-β1⁺ EV burden, specifically those whose ``armor'' is likely to be overwhelmed, thereby guiding combination therapy or EV clearance strategies. In this retrospective cohort of four patients who all developed Grade 1 CRS, the EV-associated TGF-β1 signal rose before clinical onset in the retrospectively aligned trajectories; prospective validation in larger, higher-grade CRS cohorts is required in future studies.

A Magnetic Bead-Amplified SPR/SERS Dual-Modality Assay for EV-Associated TGF-β1 as a Companion Diagnostic for CAR-T Therapy

2026-10-28

PIER Letters

Vol. 132, 36-42, 2026

DOI:10.2528/PIERL26080102

download: 12

A Novelty Quad-Channel Diplexer Based on Microstrip Loop-Type Resonators Loaded with Shorted Stubs

Jun-Mei Yan and Hong Jiang

loop-type resonators form four signal channels, with each resonator generating two channels. The microstrip loop-type resonator is loaded with four shorted stubs and supports four resonant modes. Because three of these four resonant frequencies can be independently tuned, the diplexer's signal channel center frequencies can be freely adjusted within a certain range. External coupling is achieved using parallel-coupled microstrip lines, which eliminates the need for additional impedance-matching circuits. Furthermore, the subsequent analysis indicates that the coupling strength between the port and the four resonant modes can be tuned in a certain range. This provides a certain degree of freedom for tailoring the filtering performance of each signal channel. This structure introduces source-load coupling, which can generate transmission zeros and improve the frequency selectivity of the signal channels. The mechanism analysis and design methodology of the proposed diplexer are presented. A prototype diplexer was fabricated and tested. The measured results agreed well with the simulated results, verifying the effectiveness of the proposed structure.

A Novelty Quad-Channel Diplexer Based on Microstrip Loop-Type Resonators Loaded with Shorted Stubs

2026-10-21

PIER Letters

Vol. 132, 30-35, 2026

DOI:10.2528/PIERL26071503

download: 10

Broadband Absorptive High-Power Shield Based on Multilayer of Dielectrics and Seawater

Bi-Ying Chen and Shen-Yun Wang

This paper presents a concept of a broadband absorptive EMI shield based on a multilayer of seawater and transformation dielectrics. The shield structure consists of one seawater layer and four matching layers, which function for EMI energy dissipation and wave impedance matching. The thickness and dielectric constant of the four matching layers are optimized by a genetic algorithm (GA) for a prescribed frequency band. To reduce the total thickness of the absorptive shield structure, the four matching layers are squeezed in the vertical direction using the method of transformation optics. Finally, a numerical prototype of an absorptive EMI shield is synthesized in the frequency band 0.5-1.5 GHz using a frequency-domain solver.

Broadband Absorptive High-Power Shield Based on Multilayer of Dielectrics and Seawater

2026-10-11

PIER Letters

Vol. 132, 24-29, 2026

DOI:10.2528/PIERL26072003

download: 73

Improvement of High-Frequency Wireless Power Transfer with Capacitively Loaded Slot

Marjorie Grzeskowiak

Near-field SGP (Slotted Ground Plane)-based systems, also known as DGS (Defected Ground Structure), are attractive for applications because they are easy to conceive, have low losses, and reduce circuit size to achieve a compact resonator. In this paper, we design a slim profile resonator at 13.56 MHz for HF (High Frequency) applications, such as HF RFID (High Frequency Radio-Frequency IDentification) or NFC (Near-Field Communication), and couple it to a resonant loop. The PTE (Power Transfer Energy) with 30 mm between transmitting and receiving coils is enhanced from 0.88% up to 14.6% in HF with adding a compact resonator between the loops.

Improvement of High-Frequency Wireless Power Transfer with Capacitively Loaded Slot

2026-10-10

PIER Letters

Vol. 132, 16-23, 2026

DOI:10.2528/PIERL26072301

download: 68

Analytical Calculation of the Electrostatic Field of a Charged Conducting Spherical Shell with a Circular Aperture

Hanyu Wu, Herui Cheng, Xinyi Jiang and Chongqing Jiao

In electrostatic shielding, previous studies have focused on shielding external electric fields using electrically neutral shielding shells. Here, we consider a new situation in which the electric field generated by the charge on the shielding shell penetrates the shield's interior through the shell's apertures. As a preliminary exploration of this situation, we started with relatively simple yet analytically solvable configurations. Specifically, we focus on configuring a thin-walled conducting spherical shell that is charged and has a circular aperture. For this configuration, we derive a series-form analytical solution for the potential distribution using the method of variable separation and present simplified solutions for the potential and electric-field strength along the central axis. Based on this analytical solution, we analyzed the characteristics of the potential and electric field distributions inside the spherical shell for different aperture sizes and found that, compared with a single aperture, placing two apertures at diametrically opposite positions on the spherical shell can significantly reduce the electric field strength in the region near the center of the sphere.

Analytical Calculation of the Electrostatic Field of a Charged Conducting Spherical Shell with a Circular Aperture

2026-10-07

PIER Letters

Vol. 132, 7-15, 2026

DOI:10.2528/PIERL26062905

download: 105

X-Band 3D-Printed Dielectric-Loaded Out-of-Band WR62 Waveguide Transmission Line for Reduced Size and Weight

Jie Xiang Chia and King Ho Holden Li

Waveguide transmission lines are known for their low insertion losses, particularly at higher GHz frequencies. However, they tend to be larger and bulkier than other transmission lines. This study investigates using dielectric-loaded waveguides to reduce the overall size and volume of waveguide-routed systems with the dielectric properties of 3D-printed plastics. Compared to other studies that use dielectric loading for size reduction, this study aims to reduce size, volume, and weight while maintaining relatively low losses. The approach is to use low-loss tangent dielectrics with a suitable dielectric constant responsible for reducing size, volume, and weight. Among 3D-printed plastics, Cyclic Olefin Copolymer (COC) is the most suitable based on its dielectric constant and loss tangent in the order of conventional dielectrics such as PTFE. The measured insertion loss of the 3D-printed dielectric-loaded waveguide was 0.22 dB, comparable to that of air-loaded WR90 waveguides of the same length (0.10 dB), while reducing the cross-sectional area by 46.35% and the weight by 26%. The advantage of 3D printing, dielectric-loaded waveguides is the ability to design less constrained waveguide profiles and intricate routing of waveguide transmission lines due to more flexible fabrication capabilities of 3D printing. Combining the benefits of 3D printing and the dielectric properties of COC, this study demonstrates the use of smaller waveguides in a higher frequency band that would be out of band in their air-loaded medium. By loading the smaller out-of-band waveguide with dielectric, the result shows that longer-wavelength signals, which would not be able to propagate without dielectric loading, can now propagate with low insertion loss. The waveguide chain is also miniaturized with a reduced size and overall volume, which would not have been possible with conventional air-loaded waveguides for a given frequency band, as it propagates below the cutoff frequency.

X-Band 3D-Printed Dielectric-Loaded Out-of-Band WR62 Waveguide Transmission Line for Reduced Size and Weight

2026-10-06

PIER Letters

Vol. 132, 1-6, 2026

DOI:10.2528/PIERL26081402

download: 125

A High-Gain Ultra-Wideband Dual-Polarized Vivaldi Antenna

Chenxi Chen and Jiade Yuan

This paper proposes a high-gain ultra-wideband (UWB) dual-polarized Vivaldi antenna. The proposed antenna consists of two identical Vivaldi elements orthogonally crossed to achieve dual polarization. A tapered stepped-impedance feed matching line combined with a petal-shaped open-slot structure is deployed for every Vivaldi element to enhance impedance matching efficiently and extend operational bandwidth. Furthermore, gradient-tapered curved slots, periodic tapered rectangular slots, and bent extended stubs are arranged on both sides of the radiating patch, which effectively improves the antenna's gain and directivity at mid and low frequencies within its operating bandwidth. The overall dimensions of the proposed antenna are 0.57λ_L × 0.8λ_L, where λ_L refers to the free-space wavelength at the lowest operating frequency. Experimental measurements demonstrate that the proposed antenna achieves an impedance bandwidth of 1.5-9.5 GHz for S₁₁ ≤ -10 dB. The dual-polarization port isolation is higher than 21 dB throughout the operating band, with a peak gain of 11.38 dBi. The antenna can be deployed for wideband communication and radar detection applications.