F
ULLBAND
H
IGH
ENR M
ICROWAVE
N
OISE
S
OURCES
S, C
AND
X B
ANDS
There are several primary uses for employing a noise signal for built-in-
test.
1. Using Noise for Built in Test::
These high output moduels are ideal
for buidl-in-test wehrer there is a significant path loss between the noise
source and the point at which the noise signal is used. For an example
an 8-way splitter in an array antenna receiver will allow enough power at
the receiver plane at each of the eight receive paths. Another example
allows a high directivity coupler to be used (i.e., 30 dB) allowing better
receiver noise figure.
2. Noise Temperature (noise figure) or Sensitivity Testing:
This test
uses the noise source to supply a known excess noise ratio (ENR) to a
device under test for a Y-factor measurement. By taking two receiver
readings, one with the noise on and one with it off, Y-factor can be deter-
mined. By knowing the ENR and Y-factor, one can calculate noise tem-
perature (figure) or sensitivity.
3. Frequency Response:
The noise source being broadband can be
used as a replacement of a swept source to calculate frequency
response of a receiver or other device. By putting in a known spectral
signal at the input and taking a reading at the output, one can determine
the gain or loss over frequency of the entire system. Noise sources are
inherently extremely stable devices. In addition, the circuitry is much
simpler than a swept source which increases reliability and lowers cost.
4. Amplitude Reference Source:
The noise source can be used as a
known reference signal. By switching in the noise source from the live
signal, a quick test can be performed to check the health of the chain or
calibrate the gain/loss. For this test, noise can be injected into the IF
system as well as the RF to test/calibrate the path.
For more information on using noise for built-in-test, read the Feb 2004
Microwave Journal article authored by Patrick Robbins of Micronetics.
http://www.micronetics.com/articles/microwave_journal_02-04.pdf
H
O
W TO
O
RDER
R F N 5 5 X -X
Model
L = L band *
S = S band *
C = C band
C1 = C band
C2 = C band
X = X band
* waveguide not
available on S
and L models
Option
0 = Plain
1 = Coax Isolator
2 = Waveguide
3 = Waveguide Isolator
U
S E F U L
N
OISE
E
Q U ATIONS
Calculating Y-Factor:
Y
Fact
= N
2
/ N
1
Where N
2
is measured power output with noise
source on and N
1
is the measured power output with noise source off.
Calculating Noise figure from ENR and Y-factor:
NF(dB) = ENR (dB) - 10 log10 (Y
Fact
-1)
Converting ENR to Noise spectral density (N
0
):
0 dB ENR = -174 dBm/Hz
Calculating noise power in a given bandwidth (BW) from noise
spectral density:
Power (dBm) = N
0
+ 10log(BW)
MICRONETICS [ MICRONETICS, INC. ]
