
file: A-420A.doc
Ltp:tft035
version 1.1
TFS 420A - 1 / 7
24.10.2000
VI
TELEFILTER
Application Note
VI TELEFILTER
Potsdamer Strae 18
D 14 513 TELTOW / Germany
Tel: (+49) 3328 4784-0 / Fax: (+49) 3328 4784-30
E-mail: tft@telefilter.com
VI TELEFILTER reserves the right to make changes to the product(s) and/or information contained herein without notice. No liability is assumed as a result of their
use or application. No rights under any patent accompany the sale of any such product(s) or information.
Vectron International, Inc.
267 Lowell Road
Hudson, NH 03051 / USA
Phone: (603) 598-0070 Fax: (603) 598-0075
e-mail: vti@vtinh.com
1. General
The filter is driven in an unbalanced way. It is matched to
50
The matching element values given below are theoretical calculations based on measured values for
termination impedance of test fixture (Q-value of matching elements is equal 50...70 ), given in the
specification and S-parameters of the filters on PCB. If there are parasitics on the customer PCB, the
matching elements have to be optimised as far as the circuit and PCB design are concerned.
We have tested on the PCB (tft035) two different versions of matching network (scheme 1 and scheme 2).
2. Theoretical matching
The unbalanced driven source and load termination impedances based on measured values of test fixture
(Q-value of matching elements is equal 30 ), given in the specification of the filter, and simulated optimal
values ( different Q-value ) , given below are :
Frequency
Source termination impedance [
Z
in
]
416 MHz
13,02 + j 51,58
≡
217,36
– 6,97255 pF
420 MHz
13,02 + j 52,01
≡
220,78
– 6,85616 pF
424 MHz
13,05 + j 52,45
≡
223,85
– 6,73906 pF
2.1 Scheme 1.
The values of the matching elements that are given below are calculated from the source and load
impedance, given above. The calculation was made under consideration of the parasitic capacities of
C
1p
and
C
2p
on the board.
Input elements (theory.)
Q-value
L
1
[nH]
L
3
[nH]
C
1p
[pF]
C
2p
[pF]
∞
35
39
0
∞
35
33
0,7
0,7
∞
35
33
0,7
1,6
The values of the matching elements that are given below are calculated under consideration of the
different Q-values of the matching elements and based on measured S-parameters of the filter TFS 420A.
Based on measured S-parameters we calculated the following theoretical matching components
Input elements (theory.)
Q-value
L
1
[nH]
L
3
[nH]
C
1p
[pF]
C
2p
[pF]
∞
35
39
0
∞
35
33
0,7
∞
35
33
0,7
100
35
33
0,7
50
35
33
0,7
30
35
33
0,7
Load termination impedance [
Z
out
]
21,07 + j 64,31
≡
217,36
– 5,37262 pF
21,08 + j 66,86
≡
220,64
– 5,28434 pF
21,09 + j 65,40
≡
223,90
– 5,19897 pF
Output elements (theory.)
L
4
[nH]
0
68
51
39
ILo
[dB]
-19,0
-19,0
-19,0
L
2
[nH]
35
35
35
Output elements (theory.)
L
4
[nH]
68
51
39
39
39
39
ILo
[dB]
-19,0
-19,0
-19,0
-19,5
-20,0
-20,3
L
2
[nH]
35
35
35
35
35
35
0
0,7
1,6
1,6
1,6
1,6
Z
(out)
Z
(in)
10
11
12
7 8 9
6
5
4
3 2 1
L
2
L
4
C
2p
L
1
L
3
C
1p