Phased array antenna limitations for ultra-wideband focusing

The fundamentals of ultra-wideband (UWB) focused phased array antennas are reviewed, and some basic limitations are outlined. It is shown that when phase shifters are used within the architecture of the array, the focal point moves as a function of frequency, which degrades the focusing performance of the antenna. To mitigate these limitations, time-delay units are proposed, and it is revealed that perfect focusing across a wide bandwidth can be achieved by this approach. To validate this concept, an UWB Vivaldi focused antenna array using time delays is designed which demonstrates good focusing capability across the UWB spectrum.