S-ParametersSheet 1 of 11 S-PARAMETERS Scattering Matrix V1i V2i I1 I2 V1 V1r Z01 Z02 V2 V2r t1 Input T.L L1=0 V1 = V1i + V1r Reference planes t2 Output T.L L2=0 V2 = V2i + V2r Define normalised voltages a1 = Note Using normalised voltages ≡ making the characteristic impedances =1 V1i Z 01 V1r Z 01 V2i Z 01 V2r Z 01 a2 b1 = a2 = b2 = a1 b1 b2 t1 Outgoing voltage waves ∝ ingoing voltage waves . t2 b1 = S11 . a1 + S12 . a2 b2 = S 21 . a1 + S 22 . a2 S11 S12 a1 b1 b2 = S21 S22 a2 Scattering Matrix Sheet 2 of 11 Measurement of S11 & S12 (1) Apply input to Port 1 , terminate at Port 2 with a Matched Load ∴a2 = 0. ∴ S11 = b1 = reflection coefficient at Port 1 (matched load at Port 2). a1 a2=0 b2 = Voltage transfer ratio Port 1 to Port 2 (matched load at Port 2). a1 ……