Efficient Gradient-Based Optimization of Pixel Antenna with Large Scale Connections

An efficient gradient-based optimisation method is proposed for designing pixel antennas with hundreds of connections, where the connections between adjacent square pixel patches are modelled by lossy materials with continuous density variables. The gradients of antenna objective functions with respect to these density variables are derived by the adjoint variable method, at the cost of less than two times of simulation. With a gradient-based optimisation solver, four antennas with 220 connections are optimised. The optimised antennas achieve different expected polarisation and/or radiation patterns. All the optimisations in this work converge in only 80 iterations which is considerably faster than the heuristic algorithms handling the same number of variables. Two of the optimised antennas are fabricated to validate the optimisations. The simulated and measured results verify the accuracy and effectiveness of this method.