Variation of the gain through coupling networks of Narrow Band Amplifiers

Variable gain microwave amplifiers are widely used today. A new method for the variation of gain is presented for narrow band microwave amplifiers. The technique is based on the variation of inductance and capacitance in LC matching networks. The theoretical model is presented, in which maximum gain for unconditionally stable transistor is assumed and reflection coefficient follows a segment of a constant resistance or conductance circle. An algorithm based on the method is presented that permits to design an amplifier of variable gain. A brief discussion of noise is also included. Results of simulation are presented.