http://www.micronetics.com/Noise_Diode_SMT/Surface_Mount_NC202_SM4.pdf
SM-S
ERIES
M
INI
-N
OISE
D
IODES
10 KH
Z TO
100 MH
Z
D
ESCRIPTION
Micronetics’ SM-Series Diode with its
small, surface mount SOT-23 package
is ideally suited for medium and high
volume production circuits. The ran-
dom highly stable noise characteristic
makes it ideal for several applications
from encryption, to A/D dithering.
M
INI
-N
OISE
D
IODE
S
PECIFICATIONS
FREQUENCY
(1)
MODEL BAND
RANGE
OUTPUT
(2)
dBm/Hz
(min)
BIAS
(3)
CURRENT (
typ)
TYP DC+
BIAS
SM-1 Band 1 10 KHz – 1 MHz
Band 2 1MHz – 10 MHz
Band 3 10 MHz – 100 MHz
SM-3 Band 1 10 KHz – 1 MHz
Band 2 1MHz – 10 MHz
Band 3 10 MHz – 100 MHz
SM-4 Band 1 10 KHz – 1 MHz
Band 2 1MHz – 10 MHz
Band 3 10 MHz – 100 MHz
specifies to a low end of 10 KHz.
(2) ENR is measured in a 50 ohm system.
-130
-137
-140
-138
-140
-143
-140
-141
-143
2-4mA
2-4mA
2-4mA
2-4mA
2-4mA
2-4mA
2-4mA
2-4mA
2-4mA
8.8v + 1
8.8v + 1
8.8v + 1
6.5v + 1
6.5v + 1
6.5v + 1
5.8v + 1
5.8v + 1
5.8v + 1
(1) The SM Series Noise Diodes do generate noise below 10 KHz, however, Micronetics’ only
(3) Spectral response varies with bias current. Differing levels of ENR and in-band flatness can be
realized by adjusting bias current.
Application Notes:
Encryption: In this usage, the Gaussian output of the noise is used to generate random
numbers by sampling the voltage of the noise using an A/D converter. Frequency require-
ments are usually a function of the system parameters of the random numbers desired.
As with the dithering circuit, the noise amplitude form the diode needs to be boosted with
gain. These circuits are typically high impedance.
A/D Converter Dithering Circuit: Sensitivity can be increased significantly when summing
low frequency noise (in the range of 10 KHz - 5 MHz depending on the A/D converter) with
the IF frequency prior to the input of the A/D Converter. The noise signal amplitude needs
to be boosted significantly from the output of the noise diode. Designers usually take two
approaches, one at 50 ohm in which standard radio frequency gain blocks are used and
the noise is combined with the signal at 50 ohms. The signal + noise is then converted to
high impedance prior to being fed into the A/D. The second uses op amps to boost the
noise signal and the noise is summed with the signal all at high impedance and fed directly
into the A/D.
Modulating Signal Source: The completely random nature of these analog noises have a
definite advantage over pseudo-random number generators (PRNG) chips, in that there is
no repetition. This is desired when a high level of communication security is required.
reference package style Z for dimensions
MICRONETICS / 26 HAMPSHIRE DRIVE / HUDSON, NH 03051 / TEL: 603-883-2900 / FAX: 603-882-8987
WEB: WWW.MICRONETICS.COM
MICRONETICS [ MICRONETICS, INC. ]
