Pagina 76 - TELE-satellite-1205

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SPAUN electronic GmbH & Co. KG, Germany
SMF 790
LTE Stop Band Filter
Pass band
5-790 MHz
Pass Band Attenuation
1 dB typ.
Stop Band
822-1000 MHz
Stop Band Attenuation
50 dB typ.
Jacek Pawlowski
Test Center
TELE-satellite International — The World‘s Largest Digital TV Trade Magazine
— 04-05/2012
plifier, it will still make sense
to connect the SMA filter be-
fore the next active compo-
nent (amplifier, multiswitch,
According to its specifi-
cations, it should pass the
range from 5 through 790
MHz with minimum attenua-
tion while severely attenuate
the frequency band from 822
through 1000 MHz (where
LTE signals are transmitted).
The range from 790 to 822
MHz is a transition region
where attenuation gradually
changes from single decibels
to over 50 dB.
In order to check whether
the SMF 790 complies with
the published specifications,
we used a noise generator
and a signal analyzer capa-
ble of measuring the signal
up to1000 MHz. Perhaps
the term “noise generator”
does not sound as a meas-
urement equipment to non-
specialists but in fact it is
a very useful device. When
combined with a spectrum
analyzer it produces nice
spectral views that reveal
the true frequency charac-
teristics of a filter.
As our measurements re-
vealed (and you can see
that on the attached screen
shots), the SMF 790 starts
rolling off at about 792 MHz
and reaches its maximum
attenuation at 815 MHz. So
it is even sharper than the
specifications promise. We
confirm that it attenuates
signals more than 50 dB in
the range 815-1000 MHz. We
took two additional meas-
urements at -10 dB and -30
dB. As this happened at 799
and 807 MHz, we can cal-
culate that the filter roll-off
is: 20 dB per 8 MHz. That
is a very steep transfer
characteristic what you can
evidently see in our screen
shots. We can do nothing
but praise SPAUN for such
excellent performance! It
safely blocks the LTE signals
from entering your DVB-T/
T2 terrestrial receiver.
1. The SPAUN SMF 790 has a very sharp roll off at the higher end of
the terrestrial/cable frequency range.
2. Up to 792 MHz there is practically no attenuation.
3. At approx. 799 MHz the filter has a 10 dB attenuation.
4. Attenuation increases to 30 dB at approximately 807 MHz.
5. Full 50 dB attenuation is reached at 815 MHz.
6. In accordance with specifications, there is more than 50 dB
attenuation at 822 MHz and above
Very steep frequency characteristics
Low attenuation in the pass band and high
attenuation in the stop band
Actual performance better than specification
Expert Opinion