We propose a modified split-cylinder resonator (SCR) with open slits, which can suppress the majority of TM modes while lowering the quality factors of nonzero azimuthal mode TE modes compared with grooves or protrusions. Thereby, the interference of unwanted modes on the TE $_{0n1}$ measurements can be considerably reduced, which ultimately allows almost ten modes of TE $_{0n1}$ ( $n = 1$ –10) to be used for excellent broadband and high-accuracy measurement. In addition, we newly derive a rigorous analysis of the SCR with the coaxial-type slits based on the mode matching method in detail, along with a joint iterative algorithm for considering simultaneously flange and slit. Then the numerical validation results suggest the accuracy and validity of the scheme over a wide range of dielectric sample thicknesses and slit widths. Finally, two cavities operating at 10–40 GHz and 20–78 GHz, respectively, were machined for experiments, and the improved SCR method is further validated by measuring several specimens processed from well-known materials, such as PTFE and several commercial substrates. The results demonstrate that the proposed method can perform broadband and high-accuracy measurement of the complex permittivity for dielectric samples of different thicknesses. In addition, the main sources of measurement uncertainty are also analyzed.

In this paper, in-band continuous mode transferring (CMT) method is presented for designing broadband Doherty power amplifier (DPA). Specifically, transferable continuous mode, transferring between class-J continuum to class-F-1 continuum, is introduced into DPA at output back-off (OBO) power level for improving bandwidth and efficiency. For validation, a broadband DPA with operation mode transferring from continuous class-J to continuous class-F-1 is designed, fabricated and measured. Experimental results show the drain efficiencies (DEs) of the fabricated DPA are 46.3%-57.7% and 58.4%-69.1% at 6 dB OBO and peaking power levels over 1.7-2.6 GHz. The saturation power of this DPA is 43.1-45.2 dBm with a gain of 9.1-11.2 dB in the interested band. Furthermore, when the fabricated DPA is stimulated by a 20 MHz wideband signal with a peak-to-average power ratio (PAPR) of 7.05 dB at 2.4 GHz, the measured average power is 36.5 dBm with an average DE of 45.7%, and the measured adjacent channel leakage ratios (ACLRs) are -31.9 dBc and -50.4 dBc before and after DPD technique, respectively.

A communication network integrating multiple modes can effectively support the sustainable development of next-generation wireless communications. Integrated sensing, communication, and power transfer (ISCPT) represents an emerging technological paradigm that not only facilitates information transmission but also enables environmental sensing and wireless power transfer. To achieve optimal beamforming in transmission, it is crucial to satisfy multiple constraints, including quality of service (QoS), radar sensing accuracy, and power transfer efficiency, while ensuring fundamental system performance. The presence of multiple parametric constraints makes the problem a non-convex optimization challenge, underscoring the need for a solution that balances low computational complexity with high precision. Additionally, the accuracy of channel state information (CSI) is pivotal in determining the achievable rate, as imperfect or incomplete CSI can significantly degrade system performance and beamforming efficiency. Deep reinforcement learning (DRL), a machine learning technique where an agent learns by interacting with its environment, offers a promising approach that can dynamically optimize system performance through adaptive decision-making strategies. In this paper, we propose a DRL-based ISCPT framework, which effectively manages complex environmental states and continuously adjusts variables related to sensing, communication, and energy harvesting to enhance overall system efficiency and reliability. The achievable rate upper bound can be inferred through robust, learnable beamforming in the ISCPT system. Our results demonstrate that DRL-based algorithms significantly improve resource allocation, power management, and information transmission, particularly in dynamic and uncertain environments with imperfect CSI.

To determine the complex permittivity of material mounted on the metal surface, the free-space reflection method is a good candidate due to its advantages of being nondestructive and contactless. When using the method, the extraction of the complex reflection coefficient (CRC) of the metal-backed material is the key to realize accurate measurement. Traditionally, the free-space reflection method assumes that the interrogating wave is a single plane wave, and the plane-wave reflection model is used. However, a focused beam is usually used in practice for reducing the edge effect that leads to the difference between the actual test scene and the traditional test model. In this study, a focused-wave reflection model is constructed to invert the complex permittivity, where the focused wave is considered as a Gaussian beam. The CRC of the Gaussian beam is deduced by using the plane-wave spectrum technique and plane-wave scattering-matrix (PWSM) theory. Based on the difference between the CRCs of the focused-wave and plane-wave, inverted complex permittivity corresponding to two reflection models is compared. Numerical results are given to show how the errors introduced by the plane-wave assumption are related to the waist size of the incident beam and the thickness and relative complex permittivity of the material. Measurement of a Teflon slab is given to further demonstrate the capability of the proposed procedure.

An experimental method and apparatus for investigating the interaction mechanism between microwave field and semiconductor material are presented in this paper. The investigation is based on a dual-mode compressed rectangular cavity, which includes the TE ₁₀₂ and TE ₁₀₃ modes. The TE ₁₀₂ mode is used for providing the stimulus signal, which supplies the microwave field during the experiment, and the TE ₁₀₃ mode is for testing. The two modes are individually coupled to the cavity, and two band-stop filters are introduced to isolate the signals coming from both the modes. A directional coupler is utilized to monitor the power level of the stimulus signal. Experimental results demonstrate that microwave field may affect the inherent characteristics of indium phosphate, a typical kind of semiconductor materials, which eventually leads to the nonlinear behavior of the dielectric property. After the microwave field strength exceeds a critical value, the nonlinear behavior of the microwave materials becomes more and more drastic along with further increasing field strength, and according to the particular experiment setup, we conclude that the nonlinear behavior is not caused by microwave thermal effect, but some inherent characteristics of the material itself. In addition, the experimental method and apparatus can also be employed to predict the consequences of the non-thermal action of microwave effect of other high-power microwave material under microwave field.

Next-generation communication systems demand the integration of sensing, communication, and power transfer (PT) capabilities, requiring high spectral efficiency, energy efficiency, and low cost while also necessitating robustness in high-speed scenarios. Integrated sensing and communication systems (ISACSs) exhibit the ability to simultaneously perform communication and sensing tasks using a single RF signal, while simultaneous wireless information and power transfer (SWIPT) systems can handle simultaneous information and energy transmission, and orthogonal time frequency space (OTFS) signals are adept at handling high Doppler scenarios. Combining the advantages of these three technologies, a novel cyclic prefix (CP) OTFS-based integrated simultaneous wireless sensing, communication, and power transfer system (ISWSCPTS) framework is proposed in this work. Within the ISWSCPTS, the CP-OTFS matched filter (MF)-based target detection and parameter estimation (MF-TDaPE) algorithm is proposed to endow the system with sensing capabilities. To enhance the system’s sensing capability, a waveform design algorithm based on CP-OTFS ambiguity function shaping (AFS) is proposed, which is solved by an iterative method. Furthermore, to maximize the system’s sensing performance under communication and PT quality of service (QoS) constraints, a semidefinite relaxation (SDR) beamforming design (SDR-BD) algorithm is proposed, which is solved using through the SDR technique. The simulation results demonstrate that the ISWSCPTS exhibits stronger parameter estimation performance in high-speed scenarios compared to orthogonal frequency division multiplexing (OFDM), the waveform designed by CP-OTFS AFS demonstrates superior interference resilience, and the beamforming designed by SDR-BD strikes a balance in the overall performance of the ISWSCPTS.