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A Complete Design Example 331
R,,(lossy) = 67.49.
X gI =29.49.
~I = 114.83.
L gi =46.93, C I =42.01, L I = 164.31, L 12 =97.47,
C 12 = 13.26, L,=248.01, C,=28.14, L 23 =365.12,
C 23 = 1.734, C 3 =28.14, L 3
=214.67, L 34 =227.34,
L 4 = 42.49, C 4 =70.77 (in pF, nH).
(72)
(73)
(74)
(77)-(79)
8.6.12. Perfomumce and Sensitivity Analysis. The preceding component val·
ues, applicable to Figure 8.2, were used to obtain an exact S" frequency
response by analysis; the result is equivalent to the graph in Figure 8.3, except
that the midband loss was 0.400 dB and the minimum selectivity response
above f'2 = 200 MHz was 83.75 dB instead of the specified L" = 80 dB. This
excess selectivity is partly attributable to the 9.54-dB contribution of (0.47), as
opposed to the more exact contribution of 3.54 dB of (0.46) using Qo=0.603.
(The value of Qo is known only near the end of the procedure.) This 6-dB
difference would give an estimate 2.25 dB low, which is attributable to the
marginal condition in (0.55) and the approximation in (0.49). As computed,
the selectivity slightly exceeded specifications, and the predicted midband loss
of 0.322 dB was slightly exceeded.
As indicated in (0.80)-(0.83), the important parameter in the sensitivity of
S" to load SWR is the value of IS22I; the typical behavior of this value is
shown in Figure 8.30. These data, used in (0.81) and (0.82), indicate that in
the passband the transfer response can vary by as much as ± 0.8 dB, and the
transfer phase can vary by as much as ± 1.2 degrees for a 1.2: I load SWR of
arbitrary reflection phase.
0.3
-
'""
0.1
105
100
MH,
Figure 8.30. Typical behavior of the S2~ load sensitivity parameter.