An analytical method is introduced to assess the susceptibility of radio altimeter (RA) receivers to adjacent-band fifth-generation (5G) signal interference and to quantify its impact on RA performance. The power-series method is employed to analyze the intermediate frequency (IF) signal gain compression effect of 5G signal interference on RA receivers. A behavioral-level simulation model of the RA receiver’s radio frequency (RF) front-end is constructed based on the advanced design system (ADS), and a 5G signal injection simulation is performed. The simulation results indicate that 5G signals can induce nonlinear effects in the RF front-end circuit of the RA, leading to IF signal gain compression, thereby affecting the subsequent signal processing of RA receivers. The interference effect on the RA receiver is influenced by factors such as the power and frequency of the 5G interference signal. To investigate this, an interference injection test was conducted on a specific RA receiver to validate the aforementioned interference mechanisms. The test results indicate that when the average power of the injected 5G signal at a frequency of 4000 MHz reaches −16 dBm, the IF signal power is significantly reduced. As the power of the 5G signal increases, this nonlinear effect becomes more pronounced. Furthermore, the height error ratio significantly increases, with consistent trends observed across different test frequencies. The interference threshold for the RA is lower when the signal frequency is closer to the RA operational signal frequency. Our research results demonstrate the efficacy of this method, providing a reference basis for studies on interference mechanisms and the evaluation of interference effects related to RA receivers within the electromagnetic environment of 5G signals.

In this paper, simulation modeling was carried out using Sentaurus Technology Computer-Aided Design. Two types of high electron mobility transistors (HEMT), an AlGaN/GaN/AlGaN double heterojunction and AlGaN/GaN single heterojunction, were designed and compared. The breakdown characteristics and damage mechanisms of the two devices under the injection of high-power microwaves (HPM) were studied. The variation in current density and peak temperature inside the device was analyzed. The effect of Al components at different layers of the device on the breakdown of HEMTs is discussed. The effect and law of the power damage threshold versus pulse width when the device was subjected to HPM signals was verified. It was shown that the GaN HEMT was prone to thermal breakdown below the gate, near the carrier channels. A moderate increase in the Al component can effectively increased the breakdown voltage of the device. Compared with the single heterojunction, the double heterojunction HEMT devices were more sensitive to Al components. The high domain-limiting characteristics effectively inhibited the overflow of channel electrons into the buffer layer, which in turn regulated the current density inside the device and improved the temperature distribution. The leakage current was reduced and the device switching characteristics and breakdown voltage were improved. Moreover, the double heterojunction device had little effect on HPM power damage and high damage resistance. Therefore, a theoretical foundation is proposed in this paper, indicating that double heterojunction devices are more stable compared to single heterojunction devices and are more suitable for applications in aviation equipment operating in high-frequency and high-voltage environments. In addition, double heterojunction GaN devices have higher radiation resistance than SiC devices of the same generation.

Traditional methods are unable to effectively assess the health status of engine bleed air systems. To address the limitation, this paper proposes a methodology for constructing health indicators using multi-level feature extraction. First, this approach involves data-level feature extraction from Quick Access Recorder (QAR) data and employs a method of significance compensation to process the QAR data. Second, through unsupervised learning, the ResNet Deep Autoencoder (RDAE) is utilized to do the feature-level feature extraction from the processed data. This can solve the problem of lacking annotated data and obtain the health indicators of the engine bleed air system. Third, the method was experimented on one year of QAR data from a specific airline company. The results demonstrate that the RDAE approach achieves the best performance in constructing health indicators for the system. It achieves a miss rate of 0.0523 for the duct pressure of 5th stage bleed, reducing the miss rate by 0.2810 compared to Kernel Principal Component Analysis (KPCA). It also achieves a miss rate of 0 for the pre-cooler outlet temperature, reducing the miss rate by 0.0035 compared to the Deep Autoencoder (DAE). The results indicate that the proposed method provides a more effective assessment of the health status of the engine bleed air system.

In this manuscript, we present a novel deployment protection method aimed at safeguarding aeronautical radio altimeters (RAs) from interference caused by fifth-generation (5G) telecommunication base stations (BSs). Our methodology involves an integrated interference model for defining prohibited zones and utilizes power control and angle shutoff methods to mitigate interference. First, to ensure reliable protection, we define both horizontal and vertical prohibited zones and investigate their variations to immunize RA against 5G interference. Second, we validate the effectiveness of the model in various operational scenarios, analyzing the influence of factors such as base station types, antenna parameters, flight altitude, and aircraft attitudes to cover a wide range of real-world scenarios. Third, to mitigate interference, we propose and analyze the power control and angle shutoff methods through simulation for the RMa prohibited zone. Our results demonstrate the efficacy of the deployment protection method in safeguarding RAs from 5G interference, providing guidance for interference protection during civil aviation operations and base station deployment near airports.

The 5G frequency band is extremely close to the operating frequency band of radio altimeters (RAs), so an in-depth study of the possible interference of 5G’s key parameters on RAs is especially necessary to ensure aviation safety. In this paper, the interference magnitude of 5G waveforms on an altimeter was measured by simulating the Adjacent Channel Leakage Power Ratio (ACLR) values for different sub-carrier spacing (SCS) and channel bandwidth configurations. Furthermore, interference injection experiments on simulated 5G signals and the interference thresholds of a frequency-modulated continuous wave (FMCW) altimeter were compared to experiments on the effects of the different configurations of 5G SCSs, channel bandwidths, and center frequency points. The interference thresholds of this FMCW altimeter were found to be in the range of 1 dBm to 6 dBm and −4 dBm to 0 dBm under the interference of 5G signals at the center frequency points of 3.7 GHz and 3.9 GHz. These results provided a certain reference for the engineering judgement margin of the interference thresholds.

In order to analyze the interference mechanisms of indirect lightning effects on a low-noise amplifier (LNA), a circuit model of the LNA was constructed based on the advanced design system 2020 (ADS 2020) software. Lightning pulse injection simulations were conducted to explore the influence of lightning pulses on the performance of the LNA. A pin injection test was performed to investigate the interference and damage threshold of the LNA. A protective circuit incorporating the transient voltage suppressor (TVS) and Darlington structure was designed through simulation, employing the ADS 2020 for the LNA. The research findings reveal that the interference threshold for the LNA is 60 V, while the damage threshold is determined to be 100 V. The protective circuit demonstrates a measured insertion loss of 0.1 dB, a response time of 1.5 ns, and a peak output voltage of 20 V. The research results indicate that the protective circuit can effectively reduce the impact of lightning’s indirect effects on the LNA. In the future, we will continue the design work of the protective circuit and proceed with physical fabrication and experimental validation.