Input matching circuit

A method for constructing an input matching circuit adapted to be connected to an input circuit of an amplifier, comprising the steps of:

• (a) drawing a line on a Smith chart, said lien connecting a first point and a second point, said fist point being on the Smith chart and indicating a man value of variations of an optimum signal source impedance due to manufacturing variations of the amplifier and said second point being positioned at a center of the Smith chart;
• (b) determining a third point and a fourth point on said line drawn in step (a), said third point and said fourth point being spaced from said mean value by predetermined multiples of a standard deviation of variations of said optimum signal source impedance;
• (c) obtaining a crosspoint and equi-noise index circles crossing said line drawn in step (a) at said crosspoint, said equi-noise index circles being circles of a group which respectively have said cited point and said fourth point as the optimum signal source impedance and imparting the aem noise index;
• (d) designing an input matching circuit wherein the signal source impedance as viewed from said low noise amplifier has the impedance indicated by said crosspoint;
• and
• (e) constructing an input matching circuit in accordance with the design of step (d).