THEORETICAL STUDY OF MICROWAVE TRANSISTOR AMPLIFIER DESIGN IN THE CONJUGATELY CHARACTERISTIC-IMPEDANCE TRANSMISSION LINE (CCITL) SYSTEM USING A BILINEAR TRANSFORMATION APPROACH

Conjugately characteristic-impedance transmission lines (CCITLs) are a class of transmission lines possessing conjugately characteristic impedances ([Z.sup.±.sub.0]) for waves propagating in the opposite direction. A typical [Z.sub.0] uniform transmission line is a special case of CCITLs whose argument of [Z.sup.±.sub.0] is equal to 0°. This paper aims to generalize the CCITL system by demonstrating a theoretical study of CCITLs and their applications in the microwave transistor amplifier design. It is found that the bilinear transformation plays an important role in transforming circles in the reflection coefficient [Γ.sub.0]-plane in the [Z.sub.0] system to the Γ-plane in the CCITL system. In addition, Meta-Smith charts, a graphical tool developed for solving problems in the CCITL system, are employed to design matching networks to achieve desired amplifier properties. Results show that stability regions on Meta-Smith charts can be determined, and source and load reflection coefficients can be selected properly to obtain desired operating power gain. In addition, an example shows that Meta-Smith charts offer a simple approach for matching network design using open-circuited single-stub shunt tuners.