Revista: Microwave Journal. Vol. 23. No. 6.  Pp. 70-82. June 2000.

Autores: Gustavo López Risueño and José I. Alonso

Some commercial microwave CAD progrmas do not incorporate models for more than three coupled lines. This facta is especially critical in the design and analysis of multiple-line planar structures, such as interdigital, combline and hairpin  filters, meander lines, spiral inductors and couplers. In this paper, a new and very simple technique to simulate circuits with multiple coupled lines in commercial simulators without the suitable models is presented. The proposed method, called NTL (Negative Transmission Line) method, uses pairs of two-coupled lines, single transmission lines, current controlled current sources (CCCS) and voltage controlled voltage sources (VCVS), which are availablr in any commercial microwave CAD program.