Xin Xu

This letter proposes an ultrawideband tightly coupled dipole rectenna array (TCDRA) for wireless power transfer (WPT). Compared to conventional designs of the same aperture area, the tightly coupled dipole array (TCDA) exhibits enhanced radiation efficiency and bandwidth, showing strong potential for WPT systems. Operating from 1 to 10 GHz, the proposed array employs a feeding structure combining a T‐junction and tapered baluns, which simplifies the design, ensures ultrawideband impedance matching, and reduces the need for subsequent power combining. The wide‐angle matching layer and resistive frequency selective surface (RFSS) are jointly optimized to minimize the RFSS impact on antenna efficiency. The ultrawideband rectifier, using a voltage‐doubling topology and an L‐type matching network, achieves a power conversion efficiency (PCE) above 50% from 0.03 to 10.37 GHz. A WPT system is built and tested at 1, 2.4, and 5.8 GHz, confirming that the proposed rectenna efficiently receives and converts RF energy over a wide frequency range, demonstrating suitability for diverse scenarios and complex electromagnetic environments.

This letter presents a novel miniaturized high- $Q$ combline bandpass filter (BPF) with highly controllable transmission zeros (TZs) using ceramic-lid-loaded coaxial resonator (CLLCR). The proposed CLLCR is formed by integrating a ceramic lid with a metal cavity, creating a heavily capacitively loaded structure of very compact size. Moreover, this ceramic-metal hybrid configuration enables flexible cross-coupling structures, providing a high degree of control over the TZs. As a proof-of-concept, a tenth-order BPF operating at 3.485 GHz with a 370 MHz bandwidth has been designed and implemented, and its overall dimensions of $50\times 19\times 7$ mm³ represent a 74% size reduction over conventional designs without ceramic loading. Meanwhile, the BPF achieves up to six controllable TZs using various cross-coupling mechanisms introduced by the proposed configuration to significantly enhance sideband selectivity. Measurements confirm the simulations, exhibiting excellent in-band performance, sharp out-of-band rejection, and a wide spurious-free range up to 9.77 GHz. Targeting 5G/5G-Advanced (5G-A) base station applications, the proposed BPF achieves a significant volume reduction and robust electrical performance compared to various alternatives.

This article presents a novel compact high-Q bandpass filter (BPF) utilizing a 3-D stacked stripline configuration. T-shaped stepped impedance resonators (SIRs) are employed to achieve miniaturization. By folding the filter geometry from an inline arrangement into a U-shape along the broadside direction, both broadside and edge coupling structures are realized, enabling various cross-coupling schemes for flexible placement of transmission zeros (TZs). A comprehensive analysis of both electric and magnetic coupling structures is conducted to support the overall filter design. To validate the concept, a tenth-order general Chebyshev BPF prototype centered at 3.485 GHz with a 1 dB bandwidth of 380 MHz is designed, fabricated, and measured. The filter is constructed by vertically soldering two patterned sheet metal layers together with three stacked cavities. Despite having an electrical size of only 0.58 × 0.23 × 0.19 λ_g³, the filter exhibits a high unloaded Q-factor (Q_u) of 1200, along with up to six TZs and a spurious-free frequency range extending to 12 GHz. Measured results show an insertion loss of 0.58 dB at the center frequency and a return loss of better than 20 dB within the passband, demonstrating favorable agreement with simulations. Featuring solid electrical performance, the proposed filter is ideally suited for 5G and 5G-Advanced (5G-A) communication base stations.

This letter proposes a simple ultrawideband rectifier operable up to the Ku band for wireless power transfer (WPT). A feedback line is introduced in the traditional voltage-doubling structure, which enhances second-harmonic recycling and high-frequency (HF) impedance matching, leading to a significant expansion of rectifier bandwidth. In addition, the combination of filtering capacitors and radial stubs forms an efficient dc filtering network, further extending the operating bandwidth. To validate the design, an ultrawideband rectifier is fabricated and measured. Measurement results show that the power conversion efficiency (PCE) exceeds 50% from 0.03 to 16.5 GHz. The peak PCE reaches 70.71% at an input frequency of 5.8 GHz, an input power of 24 dBm, and a $200~\Omega $ dc load. Compared to existing ultrawideband rectifiers, the proposed design demonstrates superior bandwidth performance and great potential for WPT applications.

In this article, we propose a digital encoding sensor network based on the Electromagnetically Induced Transparency (EIT) effect for industrial multi-point temperature monitoring applications, which has high sensing precision, miniaturization, spectrum saving and excellent expansibility characteristic. The sensor uses high-temperature coefficient multilayer ceramic capacitors for precise temperature sensing and utilizes an EIT structure for digital encoding. In order to validate the idea, a 4-bit sensor network is designed, which achieves 98.125 kHz/°C sensing precision and 20 MHz/bit encoding density within a compact dimension of 0.14 λ0*0.14 λ0*0.0015 λ0. Experimental results confirm the precision and linearity of the temperature-frequency response and the distinguish-ability among different encoding states. Additionally, the paper presents a 4-bit adjustable temperature sensor using varactor diodes, which can be applied in complex industrial temperature monitoring scenarios. The proposed sensor network provides high-precision temperature monitoring and efficient spectrum utilization, offering a new approach to multi-point temperature monitoring.

This letter proposes a self-diplexing shared-aperture (SA) omnidirectional rectenna for simultaneous wireless information and power transfer (SWIPT). Unlike the traditional frequency splitting (FS) methods, this approach reuses the same antenna aperture to achieve omnidirectional reception and separation of power and communication signals at different frequencies, thereby enhancing system integration and environmental adaptability. The antenna is designed using characteristic mode analysis (CMA), with a monopole mode at low-frequency (LF) and a quasi-monopole mode excited by an equal-amplitude in-phase feeding network at high-frequency (HF), achieving omnidirectional radiation with vertical polarization (VP) at both bands. Additionally, a low-power rectifier is designed and verified, and a practical SWIPT system is constructed for testing, where the HF signal is used for communication and the LF signal for RF energy harvesting (REH). The results demonstrate that the designed rectenna and architecture are suitable for SWIPT applications.

This paper proposes an efficient and wide dynamic range rectifier based on power reflection structure. The rectifier consists of a branch-line coupler and two sub-rectifiers operating at different input power levels. The branch-line coupler is used as power reflection structure. Due to the electromagnetic symmetry of the branch-line coupler and the non-linear characteristics of the rectifier, the power reflection structure can reflect mismatched energy caused by load variations or input power fluctuations back into the sub-rectifier, which can improve the reflection coefficient of the rectifier. For validation in different application scenarios, two rectifiers operating at 5.8 GHz were designed, fabricated, and characterized. For the proposed rectifier I (with load resistances RL1 = 750Ω and RL2 = 300Ω), the measured PCE maintains exceeding 50% when the input power ranges from 8 to 29.2 dBm, and the peak PCE is 68.01% at 18 dBm input power. While for rectifier II (with load resistances RL3 = 800Ω and RL4 = 300Ω), the measured PCE remains over 50% with input power from −1.2 to 28.8 dBm, and the peak PCE is 68.51% at 15 dBm input power. Theoretical analysis and performance comparison are carried out that excellent performance of proposed rectifiers in extending the input power range, which can widely apply in WPT system.