High Accuracy Adaptive Microwave Ranging Using SNR-Based Perception for Coherent Distributed Antenna Arrays

We present a high accuracy, adaptive cooperative internode ranging system for coherent distributed antenna arrays. Coherent distributed antenna arrays are networks of wireless systems coordinated at the level of the wavelength of the wireless signal to support distributed beamforming. Enabling coherent operation between separate mobile nodes at microwave frequencies requires accurate and robust knowledge of the relative positions of the nodes in the array in the presence of changing conditions. We present an adaptive microwave ranging system operating at 4 GHz that is capable of maintaining a designated ranging accuracy in the presence of changing signal-to-noise ratio (SNR) conditions. The system is based on a novel perception process that evaluates the SNR of the radar returns and estimates the accuracy of the internode ranging measurement; the output of this process feeds into a controller which determines the changes necessary in the waveform to maintain the desired accuracy. Experimental results show the ability to maintain ranging accuracy of 5 mm, which enables 90% of the ideal distributed coherent gain at frequencies up to 4 GHz.