Experimental Time-Modulated Beamformer for Interference Mitigation in a Radio Spectrometer

This paper presents experimental results using time modulation to implement inexpensive sidelobe blanking. The Allen Telescope Array is used to save time-series data for the L-band hydroxyl maser W3(OH), which presents a narrow-band source among significant narrow-band interference. A software beamformer processing these data rapidly switches between antenna weights composed of the sum and difference of the acquisition and sidelobe suppression beams. This switching both forms and multiplexes the two beams for the computational cost of a single beamformer, making this technique less expensive than similar approaches. Results show that this approach blanks most sidelobe interference in the experimental data, and also highlight the challenge of coefficient synthesis for sparse arrays.