Non Data-Aided Estimation of Modulation Index of USB TT&C Waveform with Sinusoidal Tone

Electronic reconnaissance technology has received increased attention in aerospace applications owing to its ability to analyze signals from space radiation sources. As the routine signal of satellites, the Unified S-Band (USB) Telemetry Tracking and Command (TT&C) waveform has become a crucial target of electronic reconnaissance. The modulation index of the USB TT&C waveform is a critical factor that affects the spectral characteristics of the waveform and quality of TT&C services. This parameter can be regarded as a critical feature for identifying non-cooperative targets. Considering the estimation of this parameter is an imminent requirement, a non data-aided method of modulation index is proposed. The algorithmic framework of the proposed method is based on Fourier transform and spectral analysis. The theoretical root mean squared error of the method is derived in detail, and the factors affecting the accuracy of the method are discussed. The accuracy of the method is assessed via the Monte Carlo simulation and the robustness of the method is verified using actual signals. The experimental results reveal that the accuracy of the method can reach 10−2 in a real-life electromagnetic environment where the signal-to-noise ratio is approximately −8 dB.