Enhancing Space Situational Awareness: Robust Millimeter-Wave Satellite Communication Solutions

Space Situational Awareness (SSA) assumes heightened significance in the contemporary space domain, given the proliferation of satellites and space debris. The precise monitoring of fast-moving targets in distinct orbital trajectories is a crucial aspect of SSA, demanding advanced tracking and predictive capabilities. Managing the complexities arising from the dynamic interactions between objects in different orbits necessitates a nuanced understanding of their orbital dynamics, velocities, and altitudes. In satellite communications, particularly at millimeter-wave frequencies, waveforms are susceptible to increased bandwidth and vulnerability to white noise interference. Also, multipath signals can pose challenges to reception, while the Doppler effect introduces frequency or wavelength changes, further complicating the tracking process. In dealing with these moving targets, sophisticated technologies such as radar systems and optical telescopes are deployed to accurately track and predict their trajectories. To address these issues, we propose a baseband link capable of detecting and compensating for Doppler shifts or Carrier Frequency Offsets (CFO) in received signals. Leveraging the Direct Sequence Spread Spectrum (DSSS) technique offers numerous advantages. Spread spectrum technology spreads the original signal across a wider bandwidth before transmission, enhancing resilience against interference. Moreover, DSSS receivers demonstrate improved performance in low Signal-to-Noise Ratio (SNR) environments compared to non-DSSS designs. Furthermore, the proposed system is designed to support multiuser environments, accommodating different users with distinct Pseudo-Noise (PN) sequences at a relatively low cost. In the proposed solution, we have developed two links capable of transmitting data rates of up to 350 Mbps. Quadrature Phase Shift Keying (QPSK) modulation is chosen due to its ability to achieve the same error probability as other modulation techniques with lower required SNR $\left(E_{\mathrm{b}} / N_0\right)$ for demodulation. Additionally, QPSK enables the transmission of two bits of data per symbol, effectively doubling the data rate without increasing bandwidth requirements or reducing the bandwidth for the same data rate. On the receiver side, the proposed solution has simulated all necessary synchronization circuits essential for operational satellite links. The design incorporates mechanisms to detect and compensate for Doppler shift frequencies due to moveable targets, align PN sequences with precision to within one sample, and adjust signal phase to enable coherent demodulation for QPSK. By implementing these techniques, the proposed solution aims to mitigate the challenges associated with mm-wave satellite communications, ensuring robust and efficient data transmission in dynamic and noise-prone environments.