Approximate Calculation of Line Parameters of Coupled Microstrip Lines

Abstract一 We calculate， by the Green s function technigve， the liRe capacitances and the effective filling fragtions for even一 and odd：．medes．in coupled microstrip lines which have zero-thic｝〈ness strips and an isorropic substrare． Using these results tabulated， an approximate method is shown for calculating line parameters of agey coupled microscrip lineS with zero-thickness strips． This method has a high degree of accuracy and is the useful one being able to caiculate the line parameters only with the aid of the pocket calculator． 1． lntroductionUnder the guasi-TE1糠assumption， we can obta重織theまnductancc matrix if we know the capacitance matr圭x of coup王e(l microstrip lines｛1］一［3］．The cleme鍛ts of the capacita，nce matrix can be calcula宅ed by using the 1圭ne capac至ta燕ces per u鍛it le澱gth for even-and odd-modes． Therefore， we can complcte王アdescr三be the elec亡rical behavior of coupled micros宅rip lines in terms of the linc capacitances【2］ 一【71．We can obtain these line capacitances by the method show簸ln this paper and then ob￡a三n the characteristics◎f coupled microstrip lines；characteristic impedances， phase velocities， coupling coefficients， directiviry， insertion loss， isolation etc， ｛3ト［9｝．