Design of directional couplers using multilayer thick-film technology

The performance of multilayer directional couplers using a range of different thick-film dielectrics has been investigated. The properties of multilayer coupled lines are examined using their coupled-mode parameters. It is found that the optimum performance of multilayer directional couplers is largely affected by the thick-film dielectric used. A practical design strategy for multilayer directional couplers is developed, which overcomes the problem of excessive computation that is normally associated with the optimization of multilayer circuit designs. The methodology has been verified through the design and measurement of wide bandwidth 2 dB and 3 dB directional couplers that were fabricated using multilayer thick-film technology.