Ahmed Manavi Alam

Ahmed Manavi Alam

ECE PhD Candidate at North Carolina State University

SDR-Based Dual-Polarized L-Band Microwave Radiometer for Small UAS Platforms

SDR-Based Radiometer

This project presents the design, development, and deployment of a dual-polarized L-band microwave radiometer built on a software-defined radio (SDR) architecture for operation on small unmanned aerial systems (UAS). The system enables flexible, cost-effective, and high-quality passive microwave remote sensing for applications such as soil moisture monitoring, vegetation studies, and cryospheric observations.

Key Features

  • Dual-Polarization Capability: Measures both horizontal (H) and vertical (V) brightness temperatures for improved geophysical parameter retrieval.
  • SDR Architecture: Allows reconfigurable signal processing, firmware updates, and flexible bandwidth control without hardware redesign.
  • Compact & Lightweight: Optimized for small UAS payload limits while maintaining radiometric sensitivity.
  • Frequency Band: Operates in the protected L-band (~1.4 GHz) for soil moisture and ocean salinity measurements.

Methodology

The SDR-based radiometer architecture includes:

  • Front-End Module: Low-noise amplifiers, bandpass filters, and polarization switching network.
  • SDR Back-End: High-speed digitization, digital downconversion, and onboard FPGA-based signal processing.
  • Calibration System: Internal noise diode and hot/cold reference loads for real-time radiometric calibration.

Evaluation

  • Flight Campaigns: Demonstrated from multi-rotor UAS platforms over agricultural fields and coastal zones.
  • Performance: Achieved brightness temperature measurement precision comparable to larger airborne radiometers.
  • Advantages: Lower cost, greater deployment flexibility, and rapid reconfiguration for mission-specific needs.

Impact

This work highlights the potential of small-UAS-borne SDR radiometers to complement satellite missions by providing higher spatial resolution, targeted coverage, and rapid response measurements for environmental monitoring.

Read the full paper: IEEE Xplore – SDR-Based Dual-Polarized L-Band Microwave Radiometer for Small UAS Platforms