Active Antenna Arrays using Phase Interpolation Locking

A severe constraint on the use of electronically scanned active phased arrays is the high cost per element. This paper describes a method of r.f. phase interpolation locking applicable to transmit arrays where each element would normally have its own r.f. source and phase shifter. In a linear array, the technique requires phase shifters for alternate elements only, so the number of phase shifters is halved as is the locking power required. Furthermore, if n-bit phase shifters are used, the system performance approximates to that obtainable conventionally with (n+1)-bit phase shifters. Both theory of the method and experimental results for a 5-element X-band waveguide array are discussed.