The maximum oscillation frequency of low-cost off-theshelftransistors is too low for stable operation of a fundamental24GHz oscillator. Thus, we designed a 24 GHz firstharmonic oscillator, where the power generated at the fundamentalfrequency (12 GHz) is reflected resulting in effectivegeneration of output power at the first harmonic. Wemeasured a radiated power from an integrated planar antennaof more than 1mW. Though this oscillator provides superiorfrequency stability compared to fundamental oscillators, forsome applications additional stabilization is required.
As a low-cost measure, injection locking can be used tophase lock oscillators that provide sufficient stability in freerunning mode. Due to our harmonic oscillator concept injectionlocking has to be achieved at the first harmonic, sinceonly the antenna is accessible for signal injection. We designed,fabricated and characterized a harmonic oscillator usingthe antenna as a port for injection locking. The lockingrange was measured versus various parameters. In addition,phase-noise improvement was investigated. A theoretical approachfor the mechanism of first harmonic injection lockingis presented.
