A novel parameter extraction method for the Schottky diode’s large-signal equivalent-circuit model is proposed, and used to design high-efficiency microwave rectifying circuits. This method extracts the nonlinear SPICE parameters in the equivalent-circuit from measured I-V and C-V data, and the linear parasitic parameters from the broadband small-signal S-parameters. Moreover, it employs a de-embedding technology that adopts an equivalent circuit to remove the influence of the test fixture in the S-parameters measurement, thereby additional TRL calibration kits are not required. As a sample, large-signal equivalent-circuit parameters of the Schottky diode with model number MA4E1317 are extracted by the proposed method. Then it was used to design two Class-F microwave rectifying circuits working at 2.45 GHz and 5.8 GHz, respectively. Owing to the high accuracy of the extracted parameters by the proposed method, the simulation results such as the large-signal transient voltage waveforms across the diode agree well with the measured ones. Furthermore, two rectifying circuits exhibit very high rectifying efficiencies (e.g. 83.5% at 2.45 GHz and 82.1% at 5.8 GHz with 16.8 dBm input power).

A high-efficiency 35-GHz rectifier is proposed in this letter. By employing a shielded microstrip line instead of the commonly used open microstrip line, the rectifier reduces its radiation loss and is fed by a rectangular waveguide rather than a microstrip line to lower the insertion loss. It is designed by an HFSS-ADS cosimulation technology, and consists of a Schottky diode MA4E1317, a waveguide-to-microstrip probe transition, an impedance matching circuit, a dc-pass filter, and a dc load. The proposed rectifier exhibits higher conversion efficiency than the same structure that is designed with an open microstrip line. A prototype is fabricated and measured. High MW-to-dc conversion efficiency up to 67% is obtained at 35 GHz with 19-dBm input power.

A novel waveguide-integrated rectenna with high conversion efficiency is proposed and implemented at 35 GHz in this letter. A metallic Fabry-Perot resonator antenna is designed as the receiving antenna. Using the metallic structure instead of the microstrip structure that is widely used in the conventional rectenna design, the dielectric loss is avoided and a high radiation efficiency of 95.5% is achieved at 35 GHz. The rectifier is designed with a shielded microstrip line and fed with a rectangular waveguide to lower its radiation loss and insertion loss. At 35 GHz, a rectifying efficiency of 67% is measured for the waveguide-fed cavity rectifier. By integrating the receiving antenna and the rectifier with the rectangular waveguide, a waveguide-integrated 35-GHz rectenna is proposed for the first time. A prototype is fabricated and measured. The measured highest RF-to-dc conversion efficiency is 68.5% at 35 GHz when the power density is 39.3 mW/cm².

In a microwave heating process, part of microwave power may be reflected on the air-heating sample interface due to the impedance mismatching, caused by the relative dielectric permittivity difference between the air and the heating sample. To overcome this problem, a novel impedance matching based technology is proposed. It designs and inserts an impedance matching structure between the air and the heating sample, which mitigates the drastic permittivity difference on both sides. This realizes good impedance matching and obtains the minimized reflection on the interface, hence highly efficient microwave heating is achieved. In this work, the mechanism of the proposed technology and the synthesis of such an impedance matching structure is illustrated, and then verified by an experiment using 500W 2.45GHz microwave power to heat a box of water. An impedance matching structure consisting of three homogeneous dielectric slabs is designed, and the heating cases with and without the impedance matching structure are compared. Both simulation and measurement results show that the impedance matching structure decreases the reflection coefficient of the microwave power from -1.8 dB to -25.6 dB, and correspondingly improves the heating efficiency from 34% to above 86.15%. A further analysis estimates the technology’s robustness and effectiveness for various heating sampling, showing that the heating efficiency maintains above 80% even when the heating sample’s relative permittivity ranges from 27 to 75.

A ultrawideband magnetoelectric dipole (MED) antenna fed by a ridged waveguide is presented in this letter. Different from the widely used Γ-shaped probe feeding structure, a novel ridged waveguide aperture-coupled feeding technology is employed to excite the MED antenna and an ultrawideband MED antenna with an impedance matching of 104% from 1.92 GHz∼6.08 GHz and directional pattern is realized. To verify this design, an antenna prototype is fabricated using the metallic 3-D printing technology. The measured impedance bandwidth of VSWR<2 is 104% from 1.99 GHz to 6.14 GHz. The directional patterns with a stable gain varying from 5.5 dBi to 7.5 dBi are achieved. Besides, high radiation efficiency of above 89% is obtained owing to its all-metallic structure which avoids the dielectric loss.

A three-dimensional (3-D) printed Fabry–Pérot resonator antenna (FPRA), which designed with a paraboloid-shape superstrate for wide gain bandwidth is proposed. In comparison with the commonly-adopted planar superstrate, the paraboloid-shape superstrate is able to provide multiple resonant heights and thus satisfy the resonant condition of the FPRA in a wide frequency band. A FPRA working at 6 GHz is designed, fabricated, and tested. Considering the fabrication difficulty caused by its complex structure, the prototype antenna was fabricated by using the 3-D printing technology, i.e., all components of the prototype antenna were printed with photopolymer resin and then treated by the surface metallization process. Measurement results agree well with the simulation results, and show the 3-D printed FPRA has a |S₁₁| < −10 dB impedance bandwidth of 12.4%, and a gain of 16.8 dBi at its working frequency of 6 GHz. Moreover, in comparison with the planar superstrate adopted in traditional FPRAs, the paraboloid-shape superstrate of the proposed FPRA significantly improves the 3-dB gain bandwidth from 6% to 22.2%.