A Demodulation Method for HF 3G-ALE Signal Based on Pre-Despreading

A demodulation method for the link layer protocol information carried by HF 3G-ALE signal based on pre-despreading is researched on. This method directly makes correlation despreading on the level of baseband signal, instead of making octal symbol demodulation. The experiment results show that compared with the demodulation method based on post-despreading, this method has better robustness to carrier frequency estimation error. Meanwhile, the demodulation performance is superior under the condition of low signal-to-noise ratio and low oversampling rate within a certain range of signal synchronization error, so that this method is more applicable for implementation requirement of non-cooperative communication countermeasure.