GW Instek GRF-3300 Series Teacher Manual - Manual (Page 11)

16 Microstrip Line Filters
3 319
E
L
2
=L
2
Ro/Z
h
=1.2470*50/101.73
=0.613 rads (16-24)
Combining 16-8 and 16-24, the line length of
L
2
and
L
6
is:
L
2
=0.613/
E
=86.087*0.613/(2*
S)
=8.4 mm.
The section 4 is:
E
L
4
=0.983 rads
L
4
=13.5 mm
We have to consider another issue in addition to the filter itself. The transmission
line contains 50
: impedance and is frequently put in front of the filter at both ends. Its
width is 2.3mm defined by the PCB structure. In addition, SMA terminals are attached to
the test module for external connection. The 2.3mm transmission line is too wide to be
directly connected to the SMA terminals, therefore an extra 1.6mm line section is
necessary for bridging them together.
Summarizing the above results, the entire filter is designed as in Figure 16-6.
x L1, L7: 5 [3.3 mm
x L2, L6: 0.5 [8.4 mm
x L3, L5: 5 [13.4 mm
x L4: 0.5 [13.5 mm
x Lo: 2.3 [5 mm, for 50
: transmission line