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Output Impedance Profile Selection in Sequential LMBAs using an Automatic Method

Belchior, C. ; Nunes, L. C. ; Cabral, P. M. ; Pedro, J. C.

Output Impedance Profile Selection in Sequential LMBAs using an Automatic Method, Proc International Workshop on Integrated Nonlinear Microwave and Millimeter-Wave Circuits - INMMIC, Cardiff, United Kingdom, Vol. , pp. - , April, 2022.

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Abstract
This paper proposes an automatic method to select
the optimum impedance profile of a sequential load-modulated balanced amplifier (SLMBA) output combiner network. Based on a pre-designed 90º hybrid structure, the method can simultaneously search for the optimum impedance profiles at the fundamental and second harmonic for each device connected to the hybrid. Optimizing directly the desired output power and efficiency at back-off and full power levels, the proposed algorithm avoids the issues inherent to a manual
impedance selection. As a result, three impedance profiles
represented by their scattering parameters in a polynomial form are obtained, corresponding to the output matching networks of the balanced and control amplifiers, and the required post-matching network at the 50 Ω output port. Finally, the extracted S-parameters can be synthesized by microstrip lines, allowing the validation of the method with an SLMBA implementation.