AlGaN/GaN high-electron-mobility transistors (HEMTs) with two different gate–drain distances (30 $\mathsf{\mu }$m and 10 $\mathsf{\mu }$m) were exposed to 1 MeV, 0.6 MeV, and 0.4 MeV protons at a fluence of 2.16 × 10¹² cm⁻². The gate–channel electron density and low-field mobility were obtained by measuring the capacitance–voltage characteristics and current–voltage characteristics. After proton irradiation, the gate–channel low-field electron mobility of the AlGaN/GaN HEMT with a 30 $\mathsf{\mu }$m gate–drain distance increases and that with a 10 $\mathsf{\mu }$m gate–drain distance decreases. It is studied and found that the mobility behavior is related to the polarization Coulomb field scattering, and the proton irradiation influences the intensity of the polarization Coulomb field scattering by changing the polarization/strain distribution in the barrier layer. The different gate–drain distances correspond to different variation trends of scattering intensity. The effect of 1 MeV protons on the barrier layer is smaller compared with 0.6 MeV and 0.4 MeV protons, so the mobility variation is smaller.

As a key equipment of the high-speed Electric multiple unit (EMU), the Balise transmission module (BTM) is tend to be affected by electromagnetic disturbances. However, the existing filter can not well eliminate electromagnetic disturbances. In order to improve the Signal to noise ratio (SNR) of BTM uplink signal, Variational mode decomposition (VMD) method is introduced into de-noising the uplink signal polluted by disturbance. The proposed de-noising method decomposes the noise-polluted signal into several narrow band subsignals. And then, the de-noised BTM transmitting signal is reconstructed by the sub-signals of the same frequency as the BTM carrier. To improve the accuracy of the VMD based signal decomposition, the Normalized short time fourier transform-Wigner ville distribution (NSTFTWVD) method are applied to determine the decomposition mode number of the target signal. The proposed method is used to deal with both simulation signal and measured BTM uplink signal. Results demonstrated good improvement in SNR by 20dB and 12.63dB, respectively.

AlGaN/GaN high electron mobility transistors (HEMTs) with different device sizes were prepared and exposed to 0.4 MeV proton irradiation. The low-field carrier transport characteristics of the gate channel are obtained from the capacitance-voltage curves and current-voltage curves. For the device with a longer gate-drain distance (30 μm), after 0.4 MeV proton irradiation, the gate-channel low-field carrier mobility increases by 14.3% on average. For the device with a shorter gate-drain distance (15 μm), the carrier mobility decreases by 13.4% on average after proton irradiation. This phenomenon is studied with regard to the polarization scattering effect. It is found that the polarization distribution in the AlGaN/GaN HEMTs changes after proton irradiation and different gate-drain distances correspond to different polarization distributions.