Microstrip impedance step

The equivalent circuit of a microstrip impedance step is the same as for the microstrip corner (figure 11.4). The values are according to [38]:

$$C_S \textrm{ [pF] } = \sqrt{W_1\cdot W_2}\cdot\left( (10.1\cdot\l... ..._r} + 2.33)\cdot \dfrac{W_1}{W_2} - 12.6\cdot\log{\varepsilon_r} - 3.17 \right)$$ (11.202)

for $\varepsilon_r\le 10$ and $1.5\le W_1/W_2\le 3.5$ the error is $<10$%.

$$L_1 = \frac{L_{W1}}{L_{W1}+L_{W2}}\cdot L_S$$ (11.203)

$$L_2 = \frac{L_{W2}}{L_{W1}+L_{W2}}\cdot L_S$$ (11.204)

with

$$L_{W1,2} = \dfrac{Z_{L,1,2}\cdot\sqrt{\varepsilon_{r,eff,1,2}}}{c_0}$$ (11.205)

$$\frac{L_S}{h} \textrm{ [nH/m] } = 40.5\cdot\left( \dfrac{W_1}{W_2... ... - 75\cdot\log{\dfrac{W_1}{W_2}} + 0.2\cdot \left( \dfrac{W_1}{W_2}-1 \right)^2$$ (11.206)

With $c_0$ = 299 792 458 m/s being the vacuum light velocity. The error is less than 5% for $W_1/W_2\le 5$ and $W_2/h = 1$.