Power combining by means of harmonic injection locking

The 24 GHz ISM-band is very interesting for low-cost radars. Due to cost demands no expensive phase stabilization of oscillators is possible. In this work, a free running first harmonic oscillator with a 12 GHz fundamental oscillation and a 24 GHz output signal is presented. For power combining purposes we investigated the injection locking mechanism at the first harmonic. Two-arrays consisting of three and 16 oscillators, respectively were developed and built. Mutual phase locking was achieved by means of coupling structures integrated in the antennas resulting in power combining without the requirement of costly amplifiers and frequency stabilization due to injection locking is very advantageous for low-cost radar systems. Additional stabilization can be obtained by coupling the system with an external source.