Time Modulated Array offers a simple way to synthesize radiation patterns with low sidelobe levels, in timeaverage, using an optimized strategy of switching ON and OFF the elements of the array. In this work we show that the complexity of the optimization strategy can be reduced by first shrinking the search space to a subset, or database, of useful solutions over which the optimization will be launched. This reduction is obtained by applying the constraints in a progressive and hierarchical order. In this way, this problem of exponential growth is reduced to a polynomial growth, with respect to the size of the antenna array. We present the case of designing the time modulated array for radar applications where constant directivity and ability of intereference rejection is needed.

4-arm spiral antennas have a wide bandwidth and circular polarization when operating in mode 1 (fundamental mode). Switching to mode 3 (to obtain opposite circular polarization) dramatically reduces the antenna bandwidth compared to mode 1. In this work we reduce the arm sizes of the spiral (for example with RF switches) to increase the bandwidth of mode 3 at the higher mode 1 frequencies. In this way the antenna has the same wide bandwidth for both polarizations (modes).Index Terms-4-arm spiral antenna, archimedean spiral, reconfigurable antenna, circular polarization, spiral antenna modes