Continuous Tunable Phase Shifter Based on Injection Locked Local Oscillators at 30 GHz

Injection locking is used to achieve a continuous tunable phase shift over 280° at 30 GHz. By locking a free running VCO at 15 GHz to an external reference source and doubling the output signal a very linear phase tuning range can be achieved. A phase noise of -117 dBc/Hz and -140 dBc/Hz at 100 KHz and 1 MHz offset frequency, respectively, have been measured. The prototype phase shifter is build on high ϵr = 10.2 RT/Duroid substrate to test later implementation in LTCC. The architecture is scalable to higher frequencies and can be made broadband by utilizing hybrids instead of T-junctions.