AI 中文总结
本文通过在UHF、C、Ka频段对3型军用直升机开展信道测量，分析旋翼叶片调制特性，建立阻塞衰减模型，其微多普勒特征可用于直升机分类与无源雷达应用。
AI 中文摘要
本文提出了用于无线传播信道直升机旋翼叶片调制实验表征的度量指标与测量方法。在德国曼兴的德国联邦国防军技术与适航飞机中心，针对3型军用直升机（CH-53、Tiger、UMAT），在3种间隔较大的载波频率（UHF频段302 MHz、C频段4.9 GHz、Ka频段27.1 GHz）下开展了宽带双基地信道测量。通过多普勒功率谱、均方根多普勒扩展、多普勒语谱图和功率时间分布对时变信道进行分析，发现均方根多普勒扩展值处于中等水平（最高达106 Hz），这归因于叶片相对于视线路径的主要侧向运动；功率时间分布显示Ka频段存在周期性阻塞衰减，最高达15 dB，且随载波频率升高显著增大，而302 MHz下阻塞衰减不超过2.3 dB，均方根多普勒扩展保持在10 Hz以下。采用双刃峰衍射模型对测得的阻塞衰减进行建模，结果与测量值吻合良好，语谱图中可见的独特微多普勒特征被确定为直升机分类与无源雷达应用的潜在资源。
英文摘要
This paper presents metrics and measurement methods for the experimental characterization of helicopter rotor blade modulation of the wireless propagation channel. Broadband bistatic channel measurements were conducted at three widely separated carrier frequencies (302 MHz in the UHF band, 4.9 GHz in the C-band, and 27.1 GHz in the Ka-band) for three military helicopters (CH-53, Tiger, and UMAT) at the Bundeswehr Technical and Airworthiness Center for Aircraft in Manching, Germany. The time-variant channel was analyzed in terms of the Doppler Power Spectrum and the RMS Doppler spread, the Doppler spectrogram, and the Power Time Profile. The RMS Doppler spread values were found to be moderate (up to 106 Hz), which is attributable to the predominantly lateral blade motion relative to the line-of-sight path. The Power Time Profiles revealed periodic blockage attenuations of up to 15 dB at Ka-band, increasing significantly with the carrier frequency; at 302 MHz, the blockage attenuation does not exceed 2.3 dB and the RMS Doppler spread stays below 10 Hz. The measured blockage attenuation was modeled using the double knife-edge diffraction model, showing good agreement with the measurements. The distinct micro-Doppler signatures visible in the spectrograms are identified as a potential resource for helicopter classification and passive radar applications.
