Analytical, Numerical and Experimental Study of an Original Design for a Coplanar Circulator/Isolator Based on Thick and Thin Ferrite Film

This paper takes place in the field of passive microwave components. Coming from the requirements of mobile communication devices, miniaturization of microwave components is needed. Aimed at this objective, from several years we work on the development of a miniature planar circulator/isolator. The main aim in this paper is to show the circulator with different ferrite thickness and then to present a method to reduce the insertion loss of the circulator in function of the thickness of the ferrite film. The circulator is designed with new topology coplanar/microstrip. The analytical structure based on stripline circulator and analysed by using a three dimensional finite-element method. The circulator is then fabricated, and its properties in the microwave range are characterised using a network analyzer and a probing system. An additional part for the isolator with non-symmetrical was designed in order to reduce the insertion loss in the conductor and to obtain a large bandwidth comparing to the existing devices.