On the Equivalent Radius of a Radiating Slot in Impedance Calculations

ON THE EQUIVALENT RADIUS OF A RADIATINGSLOT IN IMPEDANCE CALCULATIONSA. K. TiwariRadioFrequencySystemsandControlsDivisionRajaRamannaCentreforAdvancedTechnologyIndore,MP452013,IndiaD. R. PoddarElectronicsandTele-communicationEngineeringDepartmentJadavpurUniversityCalcutta,WB700032,IndiaB. N. DasDepartmentofElectronicsandElectricalCommunicationEngineeringIndianInstituteofTechnologyKharagpur,WB721302,IndiaAbstract—Bymeansofevaluatingimpedanceofaslotbyspectraldomainanalysis,theradiusoftheequivalentcylindricaldipoleisfoundintermsofslotparameters. Theanalysisproceedsfromtheintegralequationforthesurfacecurrentdensityinducedonaplanarstrip.Explicitexpressionsforrealandimaginarypartsofimpedancesarederivedinvisibleandinvisibleregionsrespectively.1. INTRODUCTIONWaveguidefedslotarraysareusedinmanyradarandcommunicationsystems.Considerableinvestigationshavealreadybeencarriedoutontheevaluationofadmittanceofradiatingslotusingvariational[1–3]aswellasmomentmethod[4]formulations.Thespecificadvantageofvariationalformulationisthatitenablesevaluationoftheparametersofthecomplexequivalentcircuit[1,3].Asaresulttheentireproblemreducestoasimplecircuitanalysisproblem,whichisnecessaryforslot radiator using multilayered junctions [5]. In many cases [14–16] it is convenient to replace the slot by an equivalent planar or