Ltp: tft025

version 1.0

19.06.2001

Application Note

TFS 321

1/3

TELEFILTER GmbH

Potsdamer Straße 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.

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 both, balanced and unbalanced. The current specification is valid only

for unbalanced use. Please contact us if the filter shall be used balanced at one or both ports.

The termination impedances are : 480

Ω || -1.6 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.

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.

2. Theoretical matching

For the matching of termination impedances to 50 Ohm there can be used two different

matching circuits

50 Ohm Test circuit 1

1

5

2, 4, 6, 7, 8

SAW

C1

L1

C2

L2

L3

3

The theoretical values of the stated elements are: