Mitigating interference via spatial and spectral nulling: Open air experimental results

Phase only transmit nulling may help the next generation of radar systems operate in an over-crowded RF spectrum. Open air experimental results from an eight-channel X-band radar test bed are presented that demonstrate an approach for generating constant modulus waveforms that possess spatial nulls when transmitted from an antenna array. The Re-iterative Uniform Weight Optimization (RUWO) algorithm is utilized to generate phase only weights using both a deterministic and adaptive approach. The two strategies are compared. The results demonstrate that RUWO can be used to create spatial nulls and highlight the need for careful calibration of both the transmitter and receiver.