AN0015
(iii) S12:
From Symmetry arguments:
S
= S
= –6dB
12
21
(iv) S22:
From Symmetry arguments:
= S = –53dB (matched in a 50Ω system).
S
22
11
Generally speaking the same arguments and techniques apply to a “T” configured network. The general representation
of each network is shown in Figure 2.
"PI" Attenuator
RS
"T" Attenuator
RS
RS
RP
RP
RP
Figure 2. General representation of “PI” and “T” network with parallel (Rp) and series (Rs) resistors.
The values for a 50Ω matched “T” attenuator network are given in Table 1. The complete values for a 50Ω matched “PI”
attenuator network are given in Table 2. The attenuation value (S21) usually determines which network is more realistic to
construct.
15
Copyright 1997-2002 RF Micro Devices, Inc.
15-37
RFMD [ RF MICRO DEVICES ]
