Due to the limitations of low-resolution radar system and background clutter, the task of target classification with conventional low-resolution radars is relatively difficult. This paper introduces fractional Fourier transform (FrFT) to process aircraft echoes in order to find the optimal fractional Fourier domain, in which signal to noise ratio can reach the maximum, and then applies multifractal theory to the feature extraction of radar targets. Based on the above, we use SVM to do target classification. Experiments show that the multifractal characteristics of aircraft echoes can be enhanced by FrFT, and the features extracted from the optimal fractional Fourier domain can be used effectively to classify different types of aircraft even in the case of low SNR.
In this paper, a scalable large signal GaN HEMT model including nonlinear thermal sub-circuit is described. Only two scalable parameters are needed in the I ds scalable model by introducing a simple correction factor. The established model can predict the I-V curves at different-in-size AlGaN/GaN HEMTs devices accurately. Small signal S-parameters and large signal load pull tests with on-wafer measurement is used to further validate the proposed model. Finally, the proposed scalable model is used to design a broadband high efficiency continuous class-E power amplifier (PA). Experimental results show that this class E PA is realized from 2.5-3.5 GHz with drain efficiency of 60%-70%, over 8.2 dB gain and over 35.2 dBm output by using a GaN HEMT with 1.25 mm total gate width. The results show that the proposed model is useful for high efficiency amplifier design.
Metal−organic frameworks (MOFs) have come into the limelight in the field of microwave absorption since they can be developed into porous carbon-based MOF derivatives with a variety of features, such as controlled defects, tunable structures, and variable compositions. In this paper, Cu 3 [Co(CN) 6 ] 2 Prussian blue analogue (CuCo-PBA) precursors with a regular cubic morphology were synthesized by a simple co-precipitation method and converted into CuCo nanocube/N-doped carbon nanotube (CuCo/NCNT) derivatives by annealing them in argon. It was found that when the annealing temperature was 850 °C, the minimum reflection loss (RL min ) of CuCo/NCNT could reach −54.13 dB with an effective absorption bandwidth of 4.01 GHz. The excellent microwave absorption properties were attributed to the mutual synergy of conduction loss, interfacial polarization, magnetic resonance loss, and eddy current loss. Therefore, this work provides an effective preparation method for the design of lightweight carbon-based microwave-absorbing materials with heterogeneous interfaces using Prussian blue.
The effects of parasitic inductance of transistor on finite dc-feed inductance type class E microwave power amplifier is analyzed in this letter. We find that the frequency bandwidth can be improved by fully consideration of the output parasitic inductance of transistor. To validate the method, a GaN power amplifier by using the proposed topology is designed for demonstration purpose. Experimental results show that the amplifier is realized from 2.5 GHz to 3.5 GHz (33.3%) with measured drain efficiency larger than 60%, which show good agreement with the simulated results.
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