طراحي كوپلر مايكروويو باند وسيع با استفاده از موجبرهاي مجتمع زير لايه اي

چكيده انگليسي :

Design of Wideband Microwave Coupler with Substrate Integrated Waveguide SIW Reza Toreinia r toreinia@ec iut ac ir Date of Submission 2011 06 13 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Dr Reza Safian rsafian@cc iut ac irAbstract Substrate Integrated Waveguide SIW is a new type of wave guiding structure which can beapplicable in microwave and millimeter wave integrated circuits It has advantages of conventionalrectangular waveguide to some extent and doesn t have many of its defects High Q easy and low costfabrication low volume low weight and low profile mass producible capability of integration by planarand non planar circuits are some of its advantages This is why in the recent years it has become verypopular and different types of devices such as filters couplers resonators and etc have been fabricated withthis structure Here we first speak about the necessity of using substrate integrated circuits and thenproperties of SIW such as propagation constant attenuation constant electromagnetic bandgapphenomenon and etc Two different methods to find the rectangular equivalence of SIW have beenintroduced including an empirical and a method based on analytical method of moment MOM Oursimulation shows that the latter is more exact Then we talk about coupling from small apertures in awaveguide In this thesis design process of a 20dB wideband coupler on the basis of SIW using differentmethods including chebyshev and binomial polynomials and also modeling the coupler by distributed low pass filter prototypes and using chebyshev coefficients for these prototypes have been done A MATLABprogram is used for generation of chebyshev polynomials of low pass filter prototypes The base of work isthe Bethe coupling theory for small apertures that has been expanded for large apertures Thepolarizabilities of different type of apertures have been changed to use for large apertures The type ofapertures for our designs includes circular rectangular and square For circular aperture two coefficientshave used for correction of polarizabilities and for rectangular aperture new polarizabilities have beendefined The square aperture is a type of rectangular aperture Aperture dimensions are being designed byseveral MATLAB programs that have been written based on different methods which we had introduced inthis thesis We also introduced a new method to calibrate aperture dimensions to obtain our desiredcoupling The method is based on dimensional analysis Also a Riblet Saad coupler has been designed andsimulated by a simple method that is based on dimensional analysis Excellent results have been obtainedfrom simulations Riblet Saad has the flattest coupling The error is 0 3dB on the X band Finally we seethat the flattest coupling sequentially belongs to Riblet Saad circular aperture square aperture andrectangular aperture couplers and the bigger isolation belongs to circular aperture rectangular aperture square aperture and Riblet Saad couplers sequentially It must be pointed out that design of thetransmission line should be such that it doesn t result in exciting of higher order modes in our desired band We use dual slot arrangement to prevent exciting of TE20 mode Apertures should make perfectlysymmetric in order to suppress the TE20 mode If we do this the maximum bandwidth is limited by thecutoff frequency of TE30 mode But in practice TE20 mode will be excited and the result is small error incoupling Keywords Substrate Integrated Waveguide SIW coupler coupling large aperture Riblet Saad wide band

ترينيا، رضا

طراحي كوپلر مايكروويو باند وسيع با استفاده از موجبرهاي مجتمع زير لايه اي

تزويج , روزنه ي بزرگ , ريبلت - سعد , پهن-باند