Z-Parameters of Ladder Network
Definition:
V1 = Z11·I1 + Z12·I2
V2 = Z21·I1 + Z22·I2
Step 1: Find Z11 and Z21 (I2 = 0, Output Open)
- 8Ω branch carries no current → ignore it
- From node B: Z = 20Ω
- Series: 8 + 20 = 28Ω
- Parallel at node A: Z = (10 × 28)/(10 + 28) = 7.37Ω
- Total input: Z11 = 2 + 7.37 = 9.37Ω
Z21 = 7.37 × (20 / 28) ≈ 5.26Ω
Step 2: Find Z22 and Z12 (I1 = 0, Input Open)
- 2Ω branch open → no current
- From node A: 10Ω
- Series: 8 + 10 = 18Ω
- Parallel at node B: Z = (20 × 18)/(38) = 9.47Ω
- Total: Z22 = 8 + 9.47 = 17.47Ω
Z12 = 9.47 × (10 / 18) ≈ 5.26Ω
Final Z Matrix
[ 9.37 5.26
5.26 17.47 ] Ω
ABCD Shortcut Method
If ABCD parameters are known:
T = [ A B
C D ]
Z11 = A / C
Z21 = 1 / C
Z22 = D / C
Z12 = (AD − BC) / C
Using:
A = 1.78, B = 25.84, C = 0.195, D = 3.3
Z11 = 9.13Ω
Z12 = 4.28Ω
Z21 = 5.13Ω
Z22 = 16.92Ω
