According to the nonlinear response characteristics of magnetron, this article proves that a 2.45 GHz band continuous-wave magnetron can perform as a modulator in communication system. The intermediate frequency (IF) signal coupled to the power supply of magnetron, as the ripple of anode voltage, can be modulated to a nearby band centered on the resonant frequency of magnetron. We deduced the output expression of free oscillating magnetron under the influence of anode voltage ripple. And electromagnetic simulation was accomplished to testify the validity of the theoretical derivation. Moreover, we designed the circuit to couple signal with frequencies of 2, 3, and $4$ MHz to the anode voltage. The output spectrum of magnetron changed as the frequencies were tuned, to satisfy the frequency requirements for modulating. Finally, a simultaneous information and power transfer system based on a magnetron combined with the power supply coupling circuit was developed and tested. This system achieved the modulation, amplification, transmission, and demodulation of low-frequency signal which is equivalent to human voice. This research reveals that the proposed techniques have great potential for future simultaneous wireless information and power transfer (SWIPT) system because they provide higher power at lower cost.

A compact circularly-polarized (CP) rectenna based on wide-slot antenna is designed at 5.8 GHz. The feed-back wide-slot antenna is used for its broadband, easy-to-integrate circuitry, simple structure, and low sidelobes. The designed receiving antenna has a bandwidth of 31.8%. In order to minimize the profile of the rectenna, the rectifier is integrated on the back side of the substrate with a matching circuit and a DC-pass filter. It features stable conversion efficiency on three azimuthal planes. The maximum efficiency of 66.2 % and an output DC voltage of 6.33 V have been measured with a 900 Ω load at the power density of 11.4mW/cm2. A 5 $\times$ 5 rectenna array is built for large physical aperture and increased output power. The maximum conversion efficiency of 62 % is observed with the array. Taking the advantage of immunity to misalignment of the CP antenna, the proposed rectenna and array are suitable to be used in mobile applications for wireless power transfer (WPT).

Microwave selective/localized heating has been widely used in special areas, e.g., medical treatment and food processing, but the control of selective/localized heating in restricted space, e.g., microwave ovens, is difficult to accomplish. In this article, a Giuseppe Peano fractal phased-array antenna is designed, and the phase of each radiator is derived to achieve the arbitrary spatial division of the electromagnetic field in a cavity based on the superposition principle of waves. Then, a multiphysics model of microwave heating is established by coupling the electromagnetic field and heat transfer to simulate the directional control of microwave heating in a cavity. An experimental system is built, and the heating results are measured using an infrared thermal imager to verify the temperature distribution in different spatial regions. Finally, the feasibility of the model for different heating targets is discussed.

Microwaves have been widely used in the treatment of materials, such as heating, drying, and sterilization. However, the heating in the commonly used microwave applicators is usually uneven. In this paper, a novel multi-material turntable structure is creatively proposed to improve the temperature uniformity in microwave ovens. Three customized turntables consisting of polyethylene (PE) and alumina, PE and aluminum, and alumina and aluminum are, respectively, utilized in a domestic microwave oven in simulation. During the heating process, the processed material is placed on a fixed Teflon bracket which covers the constantly rotating turntable. Experiments are conducted to measure the surface and point temperatures using an infrared thermal imaging camera and optical fibers. Simulated results are compared qualitatively with the measured ones, which verifies the simulated models. Compared with the turntables consisting of a single material, a 26%–47% increase in temperature uniformity from adapting the multi-material turntable can be observed for the microwave-processed materials.

Microwave processing of materials has been found to deliver enormous advantages over conventional processing methods in terms of mechanical and physical properties of the materials. However, the non-uniform temperature distribution is the key problem of microwave processing, which is related to the structure of the cavity, and the placement and physical parameters of the material. In this paper, a new microwave cavity structure with a sliding short based on phase-shifting heating is creatively proposed to improve the temperature uniformity. An electronic mathematical model based on the Finite Element Method (FEM) is built to predict the temperature distribution. Meanwhile, a new computational approach based on the theory of transformation optics is first provided to solve the problem of the moving boundary in the model simulation. At first, the experiment is carried out to validate the model, and heating results from the experiment show good agreement with the model’s prediction. Based on the verified model, materials selected among a wide range of dielectric constants are treated by stationary heating and phase-shifting heating. The coefficient of variation (COV) of the temperature and temperature difference has been compared in detail between stationary heating and phase-shifting heating. A significant improvement in heating uniformity can be seen from the temperature distribution for most of the materials. Furthermore, three other materials are also treated at high temperature and the heating uniformity is also improved. Briefly, the strategy of phase-shifting heating plays a significant role in solve the problem of non-uniform heating in microwave-based material processing. A 25%–58% increase in uniformity from adapting the phase-shifting method can be observed for the microwave-processed materials.

A compact circularly polarized (CP) rectenna with harmonic suppression for wireless power transmission at 5.8 GHz is proposed in this paper. The substrate integrated waveguide (SIW) structure is adopted for enhanced gain, unidirectional patterns and surface wave suppression. A rectifier, which consists of a matching network, a diode and a DC-pass filter, is integrated with the antenna at the back side. The proposed rectenna is fabricated and measured. It features 6.9 dB gain, 0.67dB axial ratio (AR) and 30 dB return loss. The conversion efficiency is 65.87 % with a 700 $\Omega$ load. A rectenna array is also build for increased aperture. It shows 61.49 % conversion efficiency with 650 $\Omega$ load in measurement. Both the rectenna and array are satisfactory choices for wireless power transfer (WPT) usage.