Design and implementation of wideband stripline circulators

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Electrical and Electronics Engineering, Turkey

Approval Date: 2012


Supervisor: ŞİMŞEK DEMİR


Ferrite circulators are crucial elements for T/R modules of RADAR systems. Unlike many other mature devices, ferrite circulators have not been replaced by IC devices and have been used in T/R modules since 60s because of two main reasons. Firstly, they do not require environmental elements like capacitors or inductors unlike IC devices. Secondly, their performance is superior in terms of insertion loss, matching and isolation. Basically, they are used for the aim of the discrimination of the incoming and outgoing signals of a single antenna. Thus, the design of wideband circulators is an important issue for the frequency band of RADAR systems. In this thesis, it is aimed to give the details of the design, simulation, fabrication and measurement procedure of a one octave and a more than one octave circulator. Firstly, a one octave circulator is designed by using continuous tracking technique. Then, the designed circulator is fabricated and observed that it performs an insertion loss of 1dB and an isolation and a return loss of better than 13 dB in the frequency band of 8.75-18.75 GHz. In the following part of the thesis, a more than one octave circulator is designed, fabricated and measured to prove that it is possible to achieve wider band circulator applications by using composite substrates. Moreover, measurement results show that an insertion loss of 1 dB and an isolation and a return loss of better than 13 dB have been achieved in the frequency band of 7.7-18.7 GHz.