This letter proposes a novel broadband, high-efficiency power amplifier (PA). The high-efficiency characteristics of Class-EF PAs and the large bandwidth advantages of Class-J PAs are effectively combined in the proposed PA. By theoretically analyzing the impedances of traditional Class-EF PAs and class-J PAs, we can consider the possibility of combining these two types of PAs. The conditions that need to be met are derived. In order to verify the effectiveness of the proposed method, a high-efficiency wideband Class-EFJ PA is designed and fabricated by using CGH40010F GaN HEMT. The measurement results demonstrate that the Class-EFJ PA has saturated output power of 40.5-42.7 dBm in 1.2-3.6 GHz. Drain efficiency of 63%-73% was achieved over the same frequency band. The Adjacent Channel Leakage Ratio (ACLR) was also better than -31.2 dBc at an average output power of 35.6 dBm.

In this paper, a highly sensitive microwave microfluidic sensor for measuring the complex dielectric constant of liquid samples is proposed. The proposed sensor is based on a triple complementary split ring resonator loaded with interdigital electrodes (TCSRR-IDE). The proposed sensor adopts an annular structure composed of interdigital electrodes (IDE) in middle ring, so as to further improve the field confinement and obtain the highest electric field strength. The outer ring is optimized to further enhance the performance of the sensor. A specimen container made of acrylonitrile-butadiene-styrene (ABS) plastic placed on the middle and outer rings with high electric field strength is employed to inject different solutions under test. The complex dielectric constant of the liquid sample is calculated by using the variations of resonance frequency and peak attenuation. The proposed sensor resonates at 2.64 GHz with a maximum frequency offset of 1030MHz. In addition, the measurement error of the real part of the complex permittivity of this sensor is 2.8% and the measurement error of the imaginary part is 8%. The measured results are consistent with the simulation consequences. Compared with the previous similar works, the sensor is small in size and has an average sensitivity of 1.23%.

An extended version of the continuous-mode Class-GF power amplifier (PA) design theory is first proposed in this letter by analyzing the impact of input voltage waveform alterations caused by input nonlinearity on the drain current waveform. Then, a novel impedance design space is explored under the extended continuous-mode drain voltage waveform. Thereafter, a multioctave, high-efficiency extended continuous Class-GF (ECCGF) PA component was implemented, fabricated, and measured with a 10-W GaN HEMT device over a 150% bandwidth from 0.4 to 2.8 GHz. The test result shows that the 39–42-dBm output power, 63%–73.2% drain efficiency (DE), and 9–12-dB gain are achieved in the target band.

Characterization of the dielectric constant of solid materials has many applications. Among them, improving the sensitivity and reducing the error of solid sensors is the key to the design. A design of a highly sensitive substrate-integrated waveguide (SIW) microwave sensor is proposed in this letter. An electric-LC (ELC) resonator is etched on the surface of the SIW to sense changes in the dielectric characteristic. Furthermore, to improve the sensitivity, both sides of the ELC are designed with an interdigital electrodes (IDEs) structure to achieve high electric field confinement in the sensing area. Meanwhile, the permittivity of the material under test (MUT) is calculated by the resonant frequency offset. The experimental results show that the sensor has a sensitivity of 8.33%, a frequency detection resolution (FDR) of 120.5 MHz, and a measurement error of 2.33% with a size of 16 $\times$ 20 mm. This work can be used for the detection of permittivity of solid materials in industrial applications.

In this paper, a design method for a high-efficiency power amplifier (PA) with a three-octave operation bandwidth is proposed. A unique impedance matching structure with three paths (TPs) and a series of inverse continuous modes (SICMs) are combined to achieve outstanding performance in terms of operating bandwidth as well as efficiency. Especially, a buffer stage of impedance matching is generated by the proposed TPs structure, which further promotes the expansion of target bandwidth. To verify the proposed methodology, an ultra-wideband PA component is implemented with a 10-W GaN HEMT device. The measurement results demonstrate a fractional bandwidth of 155.6 % from 0.5 to 4.0 GHz, with saturated output power of 39.5–42.2 dBm, drain efficiency (DE) of 57 –79 %, and a large signal gain of 9.5–12.2 dB. These results show that the PA realized by the proposed TPs impedance matching design is suitable for small-base station and multiband applications.

In this article, a high-sensitivity differential microwave sensor based on open comprehensive split-ring resonator (OCSRR) is proposed to extract the complex dielectric constant of liquid samples. An OCSRR structure is etched on the metal plate attached to the upper layer of the substrate. In addition, the outer ring of OCSRR adopts a hexagonal structure to reduce the original capacitance of OCSRR, and the inner ring of OCSRR adopts a rectangular structure to facilitate optimization and obtain the highest electric field intensity. The polydimethylsiloxane (PDMS) microfluidic channel is placed on the side of the outer ring with high electric field intensity and injects different concentrations of water–ethanol mixture. During resonance, the electric field is concentrated along the slit where the microfluidic channel is located. When the liquid sample is injected, the corresponding reflection coefficient changes. The designed sensor is fabricated and tested, and the experimental results are in good agreement with the simulation results. Compared with the previous similar sensors, the sensor can suppress the influence of environmental factors and has an average high sensitivity of 0.88%.