Mex-Wcalc: coupled_microstrip

Mex-Wcalc: coupled_microstrip_syn

coupled_microstrip_syn - Coupled microstrip transmission line synthesis

SYNOPSIS

[w_out, s_out, l_out] = coupled_microstrip_syn(z0, k, z0e, z0o, w, s, h, l, tmet, rho, rough, er, tand, f, flag)

PARAMETERS

INPUT PARAMETERS

z0 : desired characteristic impedance (Ohms)
k : desired coupling coefficient
z0e : desired even mode characteristic impedance (Ohms)
z0o : desired odd mode characteristic impedance (Ohms)
w : width of coupled microstrip line (meters)
s : spacing between coupled microstrip lines (meters)
h : substrate thickness (meters)
l : length of coupled_microstrip line (meters)
tmet : metal thickness (meters)
rho : resistivity of wire (relative to copper)
rough : conductor surface roughness (meters-rms)
er : substrate relative permitivitty
tand : substrate loss tangent
f : synthesis frequency (Hz)
flag : indicates which parameters should be optimized
- flag=1 : synthesize based on characteristic impedance and coupling coefficient
- flag=0 : synthesize based on even and odd mode characteristic impedances

OUTPUT VALUES

w_out : calculated metal width
s_out : calculated gap
l_out : calculated metal length

DESCRIPTION

Function to synthesize the physical dimenstions of a coupled microstrip transmission line to achieve a desired characteristic impedance and electrical length. The desired characteristic impedance and some of the physical dimensions of the coupled_microstrip line are given as inputs and the remaining dimensions are calculated. The line may be specified either in terms of an even mode and odd mode characteristic impedance or a characteristic impedance and coupling coefficient. The model accounts for dispersion (frequency dependent propagation velocity).


              |<--W-->|<-S->|<--W-->|
               _______       -------
              | metal |     | metal | <- rho,rough
    ----------------------------------------------
   (  dielectric                         /|\     (
    )   er,tand                       H   |       )
   (                                     \|/     (
    ----------------------------------------------
    XXXXXXXXXXXXXXXXXX ground XXXXXXXXXXXXXXXXXXXX

EXAMPLE

 % mils to meters conversion factor
sf=25.4e-6;
 % desired impedance 
z0=75;
 % desired coupling
k=0.3;
 % desired electrical length (degrees)
elen=90;
 % width (we'll synthesize this)
w=0;
 % spacing (we'll synthesize this)
s=0;
 % height
h=15*sf;
 % length
l=1100*sf;
 % metal thickness
tmet=1.4*sf;
 % resitivity of copper
rho=1.72e-8;
 % metal surface roughness
rough=0.05*sf;
 % relative dielectric constant
er=4.5;
 % loss tangent
tand=0.01;
 % frequency
f=2.4e9;
 % synthesize from z0 and k (instead
flag=1;
 % of z0e and z0o)

[w_out,s_out,l_out] = ...
    coupled_microstrip_syn(z0,k,elen,w,s,h,l,tmet,rho,rough,er,tand,f,flag);
disp(sprintf('w=%8.4g mils, s=%8.4g mils, l=%8.4g mils',w_out/sf,s_out/sf,l_out/sf));