Design of injection‐locked oscillator circuits using an HBT X‐parameters™‐based model

A load independent X‐parameters‐based heterojunction bipolar transistor (HBT) model has been used for the first time in the design and behaviour prediction of injection‐locked oscillator circuits. This model has been extracted from load‐pull measurements with a large‐signal network analyser and, in order to obtain a high oscillator RF power, targeting a load impedance close to the optimum one for HBT maximum output power. A methodology is given to obtain robust injection‐locked oscillator circuits with a high‐synchronisation bandwidth. Several injection‐locked oscillator prototypes have been designed and fabricated, and their measurements compared with the simulations obtained using the X‐parameters model. Satisfactory results were obtained when the prototypes were operated as free‐running and synchronised oscillators.