Synthetic approach to the design of wide-band microwave injection-locked amplifiers

In this work, a synthesis-based approach to the realization of wide-band microwave injection-locked amplifiers (ILA) is proposed. To this purpose, a transmission-type topology is combined with a feedback structure in which the "core ILA" is intentionally separated from the output (power) amplifier. A modular, matched, design of individual building blocks of the core ILA is then adopted, which allows their first-approximation exact modeling in the dynamical complex-envelope domain, following the theory earlier developed by Calandra-Sommariva. On this basis, analytic expressions for the main operating characteristics of the ILA (such as the locking bandwidth under small signal operation) are derived in a straightforward manner. A diakoptical analysis can then be applied for the dimensioning of the free circuit parameters of each block to satisfy the overall system-level design constraints. As example of application, a DRO-based single transistor core ILA prototype operating at X-band was designed and built, showing quite satisfactory performances and agreement with stated goal specifications.