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Noise-Source-with-2xGALI.php    7420 Bytes    08-07-2024 13:49:19


An easy to build Noise Source


With just 2 x GALI or 2 x GVA or anything in a SOT-89 case.





The photomodel comes without a Voltage regulator. Supply was 9 V, 200 mA. The final Version also has an Attenuator at the output. For Fine Adjustement of the Level and Improvement of the Matching. BOM is approx. 99 CHF.





✈ Motivation




We have heard, that there are budget friendly Noise Sources out there, but those I saw don't show a flat amplitude response. Yes, you can calibrate that away, but thats not what we wanted. So we searched a wideband transistor with a high Noise Figure. And found many of them. We now can tailor the ENR value just by changing the assembly. Nice.

Some theroretical max. ENR values (without attenuator) mayst be :

TYPENF [dB]GAIN [dB]ENR [dB]
GVA-81+7.41024.8
GVA-82+6.613.827.0
GVA-83+6.217.129.5

In order to calculate the ENR value from the Noise Floor Measurement, we used this website. The above ENR was measured with two identical Gain Blocks. The 50Ω Resistor produces a Noise of -113.1 dBm in a 300 kHz Bandwidth at 290 K.


Depending on your Selection of Amplifiers, the Bias Network as well as the Voltage Supply mayst need to be altered. Bias Calculator for MCL's Monolithics Amplifiers.




✈ Performance





With 2 x GVA-81+ and PAT-3 the ENR value is : 25.85 dB @ 1.5 GHz
And yes, we know that graphs end, where data becomes unflattering. Please believe me, I only have a FSP-3 from Rhode & Schwarz (3 GHz) High Precision Spectrum Analyzer 🙁




✈ Increasing S22 - #0002




ON ... better 20 dB
OFF ... better 20 dB

As some Tester will switch the Noise Source ON and OFF, the Output matching must be very good, in both cases. This can be accomplished by increasing the attenuator at the output to higher values. Using an attenuator of 10 dB, we can increase the matching by 20 dB. Yes, the ENR will drop by 10 dB. In terms of ENR, we measured the following values :
FREQUENCY [MHz]ENR [dB]
50021.60
100021.43
200020.90
300021.34




✈ Downloads








✈ Share your thoughts



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t1 = 6577 d

t2 = 269 ms

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