Insertion loss design of RF filters with mixed lumped-distributed realization

In this study, the purpose was to develop a user friendly software tool which enables to design microwave filters with lumped circuit elements, distributed transmission lines and mixed lumped-distributed circuit elements. For the design tool, modern insertion loss approach is preferred because of several advantages such as flexible filter specification and easy control of filter characteristic. The work is mainly concentrated on low pass Butterworth and Chebyshev type filter designs. For the lumped element and distributed element filter designs the available insertion loss methods are explained and implemented. Solution to filter problems with lumped elements alone is well established in literature. However at microwave frequencies use of lumped elements or distributed elements alone in the circuit realization has serious implementation problems. Thus mixed lumped and distributed filter design have several advantages and flexibilities in monolithic integrated circuit layouts. Unfortunately, designing filters with both lumped and distributed elements has not been solved analytically yet. Beacuse of this reason, in this work a new approximation scheme is proposed to construct filters with lumped and distributed elements. Our new proposed approximation for mixed lumped-distributed filter design and microwave filter design tool will provide new possibilities and flexibilities in designing microwave filters.