A Real-Time SDR-Based Vehicular Scatterometer with Multi-Subband Coherent Synthesis

Area of Science:

• Remote Sensing
• Microwave Engineering
• Signal Processing

Background:

• Ground-based scatterometers are crucial for soil moisture and vegetation monitoring.
• Limited bandwidth of low-cost software-defined radio (SDR) transceivers hinders fine range resolution and real-time processing.

Purpose of the Study:

• To develop a vehicular, fully polarimetric, SDR-based scatterometer with equivalent wideband capabilities for real-time onboard processing.
• To overcome the bandwidth limitations of SDRs for quantitative backscattering measurements.

Main Methods:

• Sequential transmission of narrow subbands, coherently synthesized onboard to achieve equivalent wideband response.
• Frequency-domain synthesis-pulse-compression pipeline for real-time processing on FPGA/SoC platforms.
• Online phase calibration and coherent accumulation to enhance SNR and maintain signal integrity.

Main Results:

• Demonstrated deterministic onboard range-profile output with a minimum latency of 1.57 ms per frame.
• Validated equivalent 200 MHz bandwidth, achieving 0.75 m resolution with good sidelobe performance (PSLR -27.43 dB, ISLR -12.38 dB).
• Field scans showed consistent backscattering coefficient (σ0) trends, confirming reliable quantitative measurements.

Conclusions:

• The proposed method offers a feasible solution for real-time equivalent wideband scatterometry on low-cost SDR platforms.
• Enables enhanced soil moisture retrieval, vegetation monitoring, and satellite validation with improved resolution and processing capabilities.