
Ltp: tft025
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VI TELEFILTER
Application Note
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1. General
The filter is balanced driven. It is matched to 50
The matching element values given below are valid on the test PCB. If the parasitics on the
customer PCB and on this PCB are different, the matching elements have to be optimised
regarding the circuit and PCB design.
There are ground pin thru’s under the filter and in the other area of the PCB but additional pin
thru’s to decrease cross talk.
The matching elements have been chosen from the E12- series (European standard series with
fixed tolerances) to get the best agreement between the PCB measurement and the
measurement in a reference test fixture.
Please note that all plotted data contain the insertion loss of two baluns. The insertion loss of
one balun can be assumed as 0.7 dB. So the insertion loss of the filter is 1.4 dB lower than
shown in the plots.
2. Theoretical matching
The balanced driven source and load impedances of the filter are:
Source impedance:
520
|| - 0.85 pF
Load impedance:
520
|| - 0.85 pF
Coupling coil
91 nH
The values of the matching elements, which are given below, are calculated from the source
and load impedance. If the values of the matching elements are not equal to standard values
the best standard values are given in brackets.
50
Test circuit 1
LB-IN
version 1.0
28.08.2000
TFS360F
1/4
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
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
2
1
5
6
4,7,8
LB-OUT
SAW
C1
L1
C2
L4
L2
L5
L3
3