Visualisation of the array factor of phased arrays using time delay units and digital phase shifters

To avoid the beam squint due to wide frequency band operation with a large array, a common approach is to associate a phase shifter for each element with a true-time delay (TDD) unit at the sub-array level. Using a combination of these two devices is a trade-off between scanning performance, size and cost of the system. In this paper, the characteristics of such arrays are graphically investigated over a frequency range. The TTD units can be analog or digital. The lengths of the TDDs are such that each TTD unit produces the required phase at the centre of the sub-array to steer the main beam in the highest scan-angle direction. Therefore, the TTD-units of an array have different lengths. the phase shifters are 3-bit switched-line phase shifters (SLPSs). The phase shifters are designed to operate at 30 GHz. The TTD units are analog and their lengths are calculated for a 35° steering angle.