A comparison of in-band linearity between element-digital arrays and active electronically-steered arrays

This work analyzes the differences in nonlinear performance between analog active electronically-steered and element-digital array architectures. The differences studied are based solely on receive array architecture. That is, the same low-noise amplifiers and receiver components were assumed in both architectures. The analysis demonstrates that for main-beam interferers the system third-order nonlinearity is worse for the analog architecture because its receive components after the beamformer are subjected to higher signal gain than in the digital array case. In the case of sidelobe interference, the analog beamformer acts as a spatial filter, reducing the power level coming into the nonlinear receiver proportionally to the sidelobe level. For sufficiently low sidelobe levels, the receiver nonlinear contribution is then smaller. However, for the highly-linear receiver chosen for this analysis, the element-digital architecture still maintains a linearity advantage. This allows a relaxation of the receiver linearity required in element-digital arrays to attain system-level linearity equal to that of the analog array. Coupled with an increasing level of integration, this linearity relaxation can balance the cost and power consumption associated with having a receiver in each array element, enabling the flexibility of element-level digitization.