Abstract
The plasma sheath-surrounded hypersonic vehicle is a dynamic and time-varying medium and it is almost impossible to calculate time-varying physical parameters directly. The in-fight detection of the time-varying degree is important to understand the dynamic nature of the physical parameters and their effect on re-entry communication. In this paper, a constant envelope zero autocorrelation (CAZAC) sequence based on time-varying frequency detection and channel sounding method is proposed to detect the plasma sheath electronic density time-varying property and wireless channel characteristic. The proposed method utilizes the CAZAC sequence, which has excellent autocorrelation and spread gain characteristics, to realize dynamic time-varying detection/channel sounding under low signal-to-noise ratio in the plasma sheath environment. Theoretical simulation under a typical time-varying radio channel shows that the proposed method is capable of detecting time-variation frequency up to 200 kHz and can trace the channel amplitude and phase in the time domain well under –10 dB. Experimental results conducted in the RF modulation discharge plasma device verified the time variation detection ability in practical dynamic plasma sheath. Meanwhile, nonlinear phenomenon of dynamic plasma sheath on communication signal is observed thorough channel sounding result.
Highlights
In a hypersonic vehicle[1] exceed 10 Mach ultra-high speed flight, the aircraft surface is coated with a layer of plasma, known as the “plasma sheath.”[1]
Since the radio wave attenuation in plasma sheath is large, the proposed method must applicable for the deep fading and fast time-varying plasma sheath environment. this paper proposes a cyclic sliding correlation channel sounding method based on the constant envelope zero autocorrelation (CAZAC) sequence, which can trace the real-time changes of channel fading by cyclic correlation calculation
This paper proposes a cyclic sliding correlation channel sounding scheme based on the CAZAC sequence to satisfy the time-variation frequency detection requirement for dynamic plasma sheath environment under low signalto-noise ratio (SNR) for deep fading
Summary
In a hypersonic vehicle[1] exceed 10 Mach ultra-high speed flight, the aircraft surface is coated with a layer of plasma, known as the “plasma sheath.”[1]. The available EM propagation evaluation and channel models are based on theoretical simulation without practical test data support as well,[3,14,15] and an effective channel detection means to obtain the impact of dynamic plasma sheath on transmission signal is needed . Aiming at the requirement of in-flight electron density detection and the requirement of wireless channel sounding, this paper presents a non-contact plasma sheath time-varying detection and channel sounding integration method. On one hand, it can detect the time variation frequency of the plasma in the actual flow field, on the other hand, it can measure the influence of the dynamic channel on the amplitude and phase of the transmitted signal.
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