### Java applet to calculate characteristics of a coupled pair of microstrip lines

Input dimensions are such that distance to the lower ground plane is unity. Set r = 0 if there is no upper ground plane (n.b. upper ground plane is not yet implemented). K is the dielectric constant of the substrate relative to vacuum. Calculated quantities:

• Z = sqrt(Ze*Zo), characteristic impedance
• S = (Ze - Zo)/(Ze + Zo), coupling
• ve, even mode propagation velocity
• vo, odd mode propagation velocity
• C, capacitance between either line and ground
• C', capacitance between lines

### A note on dimensionless lengths

Transverse scaling of a microstripline does not change the TEM characteristics. This is why the algorithm is written for h=1 and dimensionless w and s.

If the transverse lengths with units are H for substrate thickness, W for electrode width, and G for gap, you should scale these lengths by 1/H to get dimensionless quantities

h = H/H = 1 (always)
w = W/H
s = G/H

The dimensionless quantities w and s are the ones you should feed the applet. e.g., if H=3mm, W=15mm, and G=6mm then just divide everything by H so in new units h=1, w=5, s=2.

The answer always comes out in SI, except for velocities, which are given in units of c (speed of light in vacuum).