Design of Bias Tee for an S Band Power Amplifier

Abstract

A detailed design procedure for an S band bias tee used in a high power application is provided in this paper. A substrate with 3.66 relative permittivity and 0.762 mm in thickness is used. The proposed bias tee design utilizes an RF short-circuit in the form of a radial stub and a λ/4 transformer to implement the RF choke. A capacitor with appropriate specifications are used as the bias tee's DC block to complete the bias tee. To optimize the bias tee's form factor, a meandering approach with mitered lines are used. The resulting bias tee achieved RF - DC isolation, insertion loss, and return loss of better than -20 dB, -0.1 dB, and -24 dB respectively from 2.9 GHz to 3.5 GHz. Evidence of the realized bias tee's functionality is also provided in its utilization on an balanced S band power amplifier.