On the analysis and design of three coupled microstrip lines
Abstract
The general configuration of a system of three coupled microstrip lines is analyzed and its parameters (mode numbers, effective dielectric constants, and modal impedances) are derived in terms of the system capacitances. It is shown that for a system of three equal-width lines, there are, in general, five normal-mode impedances (four of which are independent). This would make the design of a system based on three equal-width lines, mainly with narrow strips and narrow separations, rather complicated. For a system of three equal-impedance lines, the number of mode impedances reduces to only three, which would facilitate the design. This latter system can be achieved by an appropriate increase of the width of the center line relative to that of the outer lines. Thus, a set of curves and a corresponding formula are obtained to determine this relative increase as a function of the geometric parameters.
- Publication:
-
IEEE Transactions on Microwave Theory Techniques
- Pub Date:
- November 1985
- DOI:
- 10.1109/TMTT.1985.1133197
- Bibcode:
- 1985ITMTT..33.1217A
- Keywords:
-
- Couplers;
- Electrical Impedance;
- Microstrip Transmission Lines;
- Capacitance;
- Network Analysis;
- Permittivity;
- Propagation Modes;
- Electronics and Electrical Engineering