Question

A transmission line terminates in two branches each of length λ/4 as shown. The branches are terminated by 50 Ω loads. The lines are lossless and have the characteristic impedances shown. Determine the impedance as seen by the source

(a) 200 Ω

(b) 100 Ω

(c) 50 Ω

(d) 25 Ω

Answer 1

Correct option (d) 25 Ω

Explanation:

For a λ/4 line of characteristic impedance Z0 and terminated by ZL , input impedance

z1 = z20/zL

z1 = z20/zL1 = 1002/50 = 200Ω

z2 = z20/zL2 = 1002/50 = 200Ω

zL = z1 || z2 = 200 || 200 = 100Ω

zi = z20/zL = 502/100 = 25Ω