In EFTF 2001 an extension of Leeson's model for an oscillator was used to describe and demonstrate the properties of injection-locked oscillators, at 10MHz and 2GHz [1]. An explanation of the characteristic spectrum shape of a partially locked oscillator was also put forward Some further comments on this are included here. In this paper, Leeson's model is used to describe the behaviour of a cascaded pair of injection locked oscillators operating at the same frequency of about 2GHz. The oscillators this time are single ended and not the 'balanced' configuration used previously at 2GHz. One oscillator is injected with a lower sub-harmonic frequency and this one provides an injection signal for the second oscillator. The objective is to obtain good suppression of the unwanted harmonics of sub-harmonic injection frequencies. Measurements of the lock in range and capture range are compared with the theoretical predictions. Also measured and compared with theory is the suppression of the unwanted harmonics of the injection frequencies.
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