- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Fabrication and electromagnetic wave absorption property of quartz ceramics with a gradient distribution of BaTiO3
摘要： Quartz ceramics with a uniform/gradient distribution of BaTiO3 (U/G–SO–BTO) are fabricated by cold pressing a powder blend with BTO followed by sintering and using a combined technique of spreading the powder blends with gradually increased BTO layer–by–layer and sintering. The electromagnetic wave absorption properties of these two ceramics are studied in detail. For U–SO–BTO samples, the primary electromagnetic re?ection is strong due to the aggravated impedance mismatch at their surfaces. The electromagnetic wave re?ectivity of U–SO–BTO could only reach ?7.0 dB when the sample thickness is 6 mm and the BTO content is 8.0 wt%, and it decreases slightly to ?8.1 dB when the sample thickness is increased to 10.0 mm and the BTO content is decreased to 5.0 wt% simultaneously. For G–SO–BTO samples, electromagnetic waves could enter with little re?ection due to the weak surface impedance mismatch, and the electromagnetic waves entering these samples could propagate forward while being absorbed gradually with little re?ection because of the weak impedance mismatch at the interfaces. The G–SO–BTO samples are promising excellent electromagnetic absorbing materials because their electromagnetic wave re?ectivity could reach a level lower than ?12.0 dB and could decrease further from –12.2 to ?13.1 dB as the layer thickness increases from 1.0 to 2.0 mm.
关键词： Impedance mismatch,Electromagnetic wave absorption,Quartz ceramics,Electromagnetic re?ection,Gradient distribution,BaTiO3
更新于2025-09-23 15:22:29
-
Analysis of a single-mode waveguide at sub-terahertz frequencies as a communication channel
摘要： We study experimentally the transmission of an electromagnetic waveguide in the frequency range from 160 to 300 GHz. Photo-mixing is used to excite and detect the fundamental TE10 mode in a rectangular waveguide with two orders-of-magnitude lower impedance. The large impedance mismatch leads to a strong frequency dependence of the transmission, which we measure with a high-dynamic range of up to 80 dB and with high frequency-resolution. The modified transmission function is directly related to the information rate of the waveguide, which we estimate to be about 1 bit per photon. We suggest that the results are applicable to a Josephson junction employed as a single-photon source and coupled to a superconducting waveguide to achieve a simple on-demand narrow-bandwidth free-space number-state quantum channel.
关键词： communication channel,TE10 mode,sub-terahertz frequencies,Josephson junction,impedance mismatch,superconducting waveguide,single-photon source,waveguide
更新于2025-09-23 15:19:57
-
[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Synchronous Pumping Terahertz Parametric Oscillator Driven by Amplified Picosecond Mode-locked Laser
摘要： This paper analyzes the effects of load impedance mismatch in power ampli?ers which linearity has been enhanced using various digital predistortion (DPD) algorithms. Two different power ampli?er architectures are considered: a class AB and a Doherty ampli?er and three model structures for the DPD model are compared: memoryless polynomial (MLP), general memory polynomial (GMP) and Kautz-Volterra functions (KV). This paper provides a sensitivity analysis of the linearized ampli?ers under load mismatch conditions and reports the performance when dynamic parameter identi?cation for the DPD is used to compensate for the changes in the load impedance. In general, power ampli?ers linearity is sensitive to load impedance mismatch. Linearity may degrade as much as 10 dB (in normalized mean square error) according to the magnitude and the phase of the re?ection coef?cient provided by the load impedance. However, depending on the ampli?er design, the sensitivity to load impedance mismatch varies. While the Doherty ampli?er studied show signi?cant linearity degradations in the in-band and out-of-band distortions, the out-of-band distortions of the studied class AB were less sensitive to the load impedance mismatch. In adaptive DPD schemes, the performance obtained in the MLP model does not bene?t from the updating scheme and the performance achieved is similar to a static case, where no updates are made. This stresses the memory requirements in the predistorter. When employing the GMP and the KV models in an adaptive DPD scheme, they tackle to a larger extent the linearity degradations due to load impedance mismatch.
关键词： load impedance,Digital predistortion,power ampli?ers,impedance mismatch
更新于2025-09-19 17:13:59
-
[IEEE 2019 IEEE Transportation Electrification Conference and Expo, Asia-Pacific (ITEC Asia-Pacific) - Seogwipo-si, Korea (South) (2019.5.8-2019.5.10)] 2019 IEEE Transportation Electrification Conference and Expo, Asia-Pacific (ITEC Asia-Pacific) - Technical Evaluation of Utility-Interactive Photovoltaic Power Generation System with Energy Storage based on the Experimental Setup
摘要： This paper analyzes the effects of load impedance mismatch in power ampli?ers which linearity has been enhanced using various digital predistortion (DPD) algorithms. Two different power ampli?er architectures are considered: a class AB and a Doherty ampli?er and three model structures for the DPD model are compared: memoryless polynomial (MLP), general memory polynomial (GMP) and Kautz-Volterra functions (KV). This paper provides a sensitivity analysis of the linearized ampli?ers under load mismatch conditions and reports the performance when dynamic parameter identi?cation for the DPD is used to compensate for the changes in the load impedance. In general, power ampli?ers linearity is sensitive to load impedance mismatch. Linearity may degrade as much as 10 dB (in normalized mean square error) according to the magnitude and the phase of the re?ection coef?cient provided by the load impedance. However, depending on the ampli?er design, the sensitivity to load impedance mismatch varies. While the Doherty ampli?er studied show signi?cant linearity degradations in the in-band and out-of-band distortions, the out-of-band distortions of the studied class AB were less sensitive to the load impedance mismatch. In adaptive DPD schemes, the performance obtained in the MLP model does not bene?t from the updating scheme and the performance achieved is similar to a static case, where no updates are made. This stresses the memory requirements in the predistorter. When employing the GMP and the KV models in an adaptive DPD scheme, they tackle to a larger extent the linearity degradations due to load impedance mismatch.
关键词： power ampli?ers,Digital predistortion,impedance mismatch,load impedance
更新于2025-09-16 10:30:52
-
[IEEE 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Atlanta, GA, USA (2019.7.7-2019.7.12)] 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Optimization of Coplanar Waveguide Structure for Ultra Wideband Integrated Electro-optic Mach Zehnder Modulator
摘要： Using numerical tools, coplanar waveguide (CPW) transmition line is optimized to be utilized in ultra-compact traveling wave electro-optic modulators (EOMs). Important factors such as minimization of the radio frequency (RF) loss, impedance mismatch, and velocity mismatch are investigated. Our results reveal that coplanar waveguide can provide conditions for ultra compact Mach-Zehnder modulators (MZM) to operate at frequencies up to terahertz range.
关键词： velocity mismatch,electro-optic modulators,impedance mismatch,RF loss,coplanar waveguide
更新于2025-09-12 10:27:22
-
Noise Behavior and Implementation of Interferometer-Based Broadband VNA
摘要： This paper analyzes and accurately models the complex noise behavior of vector network analyzers (VNAs) when measuring large-mismatch devices and subsequently shows how the VNA measurement noise performance is enhanced through implementation of a high-speed, broadband, active RF interferometer module. The presented VNA noise model provides a solid framework, benchmarked by measurement data, to analyze existing RF interferometer approaches. The performance improvement of the proposed interferometer implementation is then benchmarked in terms of magnitude and phase stability of the renormalized impedance level. A test bench employing the novel add-on RF interferometer module is presented and demonstrated to achieve high-speed cancellation of the scattered wave over a broad frequency band. The first experiment shows ultralow noise in a 1–18 GHz broadband measurement of co-planar waveguide 0.5-Ω and 5-kΩ impedance standards. Employing the proposed hardware setup improves the noise uncertainty for the 5-kΩ impedance standard by a factor of 8 and 20 at 1 and 18 GHz, respectively. In the second experiment, a factor of 2 height-resolution enhancement is achieved in a scanning microwave microscope when the RF interferometer module is added to the instrument.
关键词： vector network analyzer (VNA),impedance mismatch,noise,Extreme impedance measurement,microwave interferometry,nanoelectronics,nanostructures
更新于2025-09-09 09:28:46