MICRONETICS / 26 HAMPSHIRE DRIVE / HUDSON, NH 03051 / TEL: 603-883-2900 / FAX: 603-882-8987

WEB: WWW.MICRONETICS.COM

D

ESCRIPTION

Micronetics' ST-2 Diode with

its small, surface mount SOT-

23 package are ideally suited

for medium and high volume

production circuits. Their

Gaussian wideband highly

stable noise characteristics

make them ideal for several

applications from built-in

Microwave receiver calibra-

tion, to A/D dithering.

P

INOUT

Pin 1 - Ground

Pin 2 - Bias/Noise Output

Pin 3 - N/C

See style code Z on our web-

site for additional outline

details:

http://www.micronetics.com

MODEL

FREQUENCY

OUTPUT (1)

FLATNESS (2)

TYP BIAS (2)

TYP DC+

NUMBER

RANGE

ENR dB (min)

dB (max)

CURRENT (max)

BIAS

ST-2

10 KHz - 1 MHz

33

2.0

2-4 mA

5.2v

1 MHz – 100 MHz

30

2.0

2-4 mA

5.2v

100 MHz – 3 GHz

28

2.0

2-4 mA

5.2v

(1) ENR is measured in a 50 ohm system.

(2) Spectral response varies with bias current. Differing levels of ENR and in-band flatness

can be realized by adjusting bias current.

Application Notes:

Microwave Receiver Calibration: There are two built-in tests commonly performed with

noise. One is a straightforward noise figure or noise temperature test. The other is a spec-

tral calibration, which uses the broadband flat frequency output of the noise to test frequen-

cy response. This test typically requires a higher amplitude noise signal than the noise

temperature test and may require a gain stage to boost the signal.

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.

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.