AN L-BAND DIGITAL PHASE SHIFTER

a digitally controlled phase shifter was developed which has potential application to fixed array radar systems. The device is capable of producing shifts in phase in steps of 2-1316 degrees from 0 to 360 degrees. The phase shifter, which operates throughout at 1200 mc, utilizes G.E. type 6299 uhf-shf triodes, and different lengths of strip transmission lines, in seven stages to produce 128 steps of phase shift. A phase-shift accuracy of 3 degrees was maintained at the center frequency with a power gain of 14 to 17 DB. A maximum phase error of 20 degrees was observed over a 10-mc bandwidth centered at 1200 mc. Within certain rather narrow limits of frequency, triode grid and plate voltages, rf drive power, and tube characteristics, the circuit is capable of giving excellent control of phase shift. Once the phase shifter is tuned, there is no measurable change in phase with time.