Sidelobe reduction for phased array antennas using digital phase shifters. Part 2: Two bit phase weighting

The preceding paper has described a novel method for sidelobe reduction in a phased array, using equal-amplitude elements with randomised phase reversals to create an effective amplitude taper. This can be superimposed on beam steering phase shifts by altering the first bit of some phase shifters. If we extend the one bit phase weighting scheme, we can simultaneously steer the beam and apply an effective amplitude taper using phase shifters with only two bits. The scheme has now to reduce both the first sidelobe (via the taper) and the parasitic sidelobes due to beam steering with only two bits. The variance of the random process is now increased, and the peak sidelobe levels achieved are not as low as for one bit phase weighting. For 128 array elements, the peak sidelobe level achieved is ¿¿15.6 dB and for 256 elements ¿¿17.4 dB.