oq2538u NXP Semiconductors, oq2538u Datasheet - Page 11

• Manufacturer Part Number: oq2538u
• Description: Sdh/sonet Stm16/oc48 Main Amplifiers
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Noise figure measurements
The noise figure is the ratio of signal-to-noise ratio at the
input (S
the amplifier. This definition is true for both single-ended
and differential amplifiers, provided the correct values for
S
figure is measured using the differential set-up shown in
Fig.10. The total noise on the output (N
measured using the spectrum analyzer at the frequency of
interest. From this value, the actual (differential) noise
figure for that frequency (spot noise figure) can be
calculated using the following formula:
The factor 2 in the denominator is present to compensate
for the fact that S
2000 Sep 29
F
handbook, full pagewidth
i
/N
SDH/SONET STM16/OC48 main amplifiers
=
i
and S
termination
-----------------
S
S
50
o
i
i
/N
N
N
SMA
termination
i
) to signal-to-noise ratio at the output (S
50
i
o
o
/N
=
o
SMA
-------------------------- -
2 S
are substituted in the formula. The noise
21
N
is the single-ended power gain,
21
o
N
i
50
50
=
--------------------------- -
2 S
semi rigid
semi rigid
N
21
o
kT
100
Fig.10 Noise figure measurement set-up.
o
in dBm) is
100 pF
100 pF
100
o
/N
o
) of
IN
INQ
V EE = 4.5 V
11
OQ2538HP
test PCB
whereas the differential power gain is applicable in this
situation. N
power at the input, which is kT under matched conditions
(k is Boltzmann’s constant). The formula expressed in
dBm makes calculation easier:
assuming log(kT) is 173.8 dBm (T = 298 K) and
N
For the OQ2538HP, in the differential configuration
(including the 100
typical noise figure of 11 dB.
While the performance of this measurement set-up cannot
match that of a dedicated noise analysis system, the
results are comparable for an amplifier with a noise figure
of 11 dB.
F
o
OUTQ
=
measured in 1 Hz bandwidth and expressed in dBm.
OUT
N
o
100
–
S
i
can be replaced with the available noise
21
+
3
IN
Z o = 50
100
SPECTRUM
+
ANALYZER
OQ2538HP; OQ2538U
matching resistors), this yields a
173.8
50
50
semi rigid
semi rigid
dB
,
Product specification
50
termination
MGM112
SMA