
Ltp: tft025
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VI TELEFILTER
Application Note
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1. General
The filter is symmetrical, i.e. input and output are exchangeable with each other. But the
external coupling coil has to be connected to pin 3 in any case.
The filter can be driven balanced only.
To get a balanced signal for test measurements with the Network Analyzer we use two
wideband 1:1 transformers at each port:
SMT 4, vendor NEOSID, PN 88 8529 10
The termination impedances are :
600
|| -1.45 pF
This impedance is equal for the input and the output. It has to be realized at the point were the
filter is mounted. To match this impedance to the impedance of the system a matching circuit
is required.
2. Theoretical Matching
For the matching to 50 Ohm there can be used two different matching circuits:
50 Ohm Test circuit 1
LB-IN
version 1.1
01.11.00
TFS 246M - 1/2
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VI TELEFILTER
Potsdamer Strae 18
D 14 513 TELTOW / Germany
Tel: (+49) 3328 4784-52 / Fax: (+49) 3328 4784-30
E-Mail: tft@telefilter.com
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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
Tel: (603) 598-0070 Fax: (603) 598-0075
E-Mail: vti@vtinh.com
2
1
6
5
4,7,8
LB-OUT
SAW
C1
L1
C2
L4
L2
L3
L5
3
C3
The theoretical values of the stated elements are:
L1 = L2 =L3 = L4 = 53 nH
C1 = C2 = 2.1 pF
C3 = 0 pF
L5 = 108 nH