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Lower LNA Gain measured on NanoVNA Saver (ADF4350 TX POWER setting not available)


Kevil 2021/12/09 11:38

I am trying to measure the gain of the Infineon BGA524N6BOARDTOBO1 Evaluation Board ( https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSEPZdgUmVl3YfPSnZSiFNpjUn-GHATXYp9fg&usqp=CAU ) to test the BGA524N6 LNA by NanoVNA 2.2 (SAA2) with firmware nanovna-v2-20201013-v2_2_8.bin

With the default settings I didn't get expected gain 19.7 dB at 1575 MHz, I got 5.8 dB only at Vcc = 3.3V/2.6mA, When I changed the NanoVNA settings "ADF4350 TX POWER" from default "3" to "0" I got the expected gain 19.08db at 1.275 GHz.

I don't fully understand what the TX POWER means and what is the TX Power in dBm send by NanoVNA to LNA.

I would like to get bigger chart that's why I use NanoVNA Saver v0.3.9 but S21 Gain (db) shows clipped jagged chart with max. gain 8.946 dB. Is there any setting in  NanoVNA Saver similar to "ADF4350 TX POWER" on the NanoVNA to get the same result (19.08 dB)?

W0LEV 2021/12/10 17:20

One can easily overdrive an amplifier with too much input power. Once it
is driven into compression, all bets on correct measurements are off. That
point is usually referred to as the "1 dB compression point". This is the
point where the Power Input vs Power output curve deviates (or drops) from
a linear progression to 1 dB less on the output power as compared to the
linear progression.

dBm is a standard unit of measuring power in the world of RF. A 50-ohm
non-reactive system is assumed in most cases. The small "m" indicates the
reference is milliwatts. The dB represents the log base 10 of the ratio of
power referenced to 1 milliwatt. For example, 0 dBm = 1 milliwatt, -10 dBm
= 0.1 milliwatts, + 10 dBm = 10 milliwatts, and +30 dBm = 1 Watt.

It's been a while since I worked with Fibre Channel and don't remember the
max levels for the bus.

Dave - WØLEV

On Fri, Dec 10, 2021 at 3:49 AM Kevil via groups.io <tiputa=
yahoo.com@groups.io> wrote:

> I am trying to measure the gain of the Infineon BGA524N6BOARDTOBO1 Evaluation
> Board
> <https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSEPZdgUmVl3YfPSnZSiFNpjUn-GHATXYp9fg&usqp=CAU>
> to test the BGA524N6 LNA by NanoVNA 2.2 (SAA2) with firmware
> nanovna-v2-20201013-v2_2_8.bin
>
> With the default settings I didn't get expected gain 19.7 dB at 1575 MHz,
> I got 5.8 dB only at Vcc = 3.3V/2.6mA, When I changed the NanoVNA settings
> "ADF4350 TX POWER" from default "3" to "0" I got the expected gain 19.08db
> at 1.275 GHz.
>
> I don't fully understand what the TX POWER means and what is the TX Power
> in dBm send by NanoVNA to LNA.
>
> I would like to get bigger chart that's why I use NanoVNA Saver v0.3.9 but
> S21 Gain (db) shows clipped jagged chart with max. gain 8.946 dB. Is there
> any setting in NanoVNA Saver similar to "ADF4350 TX POWER" on the NanoVNA
> to get the same result (19.08 dB)?
>
>
>
>

--
*Dave - WØLEV*
*Just Let Darwin Work*

Jim Lux 2021/12/10 10:04

On 12/9/21 11:38 AM, Kevil via groups.io wrote:
>
> I am trying to measure the gain of the Infineon BGA524N6BOARDTOBO1
> Evaluation Board
> <https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSEPZdgUmVl3YfPSnZSiFNpjUn-GHATXYp9fg&usqp=CAU>
> to test the BGA524N6 LNA by NanoVNA 2.2 (SAA2) with firmware
> nanovna-v2-20201013-v2_2_8.bin
>
> With the default settings I didn't get expected gain 19.7 dB at 1575
> MHz, I got 5.8 dB only at Vcc = 3.3V/2.6mA, When I changed the NanoVNA
> settings "ADF4350 TX POWER" from default "3" to "0" I got the expected
> gain 19.08db at 1.275 GHz.
>
> I don't fully understand what the TX POWER means and what is the TX
> Power in dBm send by NanoVNA to LNA.
>
> I would like to get bigger chart that's why I use NanoVNA Saver v0.3.9
> but S21 Gain (db) shows clipped jagged chart with max. gain 8.946 dB.
> Is there any setting in  NanoVNA Saver similar to "ADF4350 TX POWER"
> on the NanoVNA to get the same result (19.08 dB)?
>
You've got two problems:

1) you're overdriving the amplifier (datasheet says P1dB is -12dBm on
the input) - that's a GNSS LNA, and it's designed to operate with input
signals at the noise floor.

2) you're probably overdriving the CH1 input on the VNA. I don't know
what the max input is, but it's probably in the 0dBm, maybe +10dBm range.


The ADF4350 Power number isn't the power, it's an arbitrary number maybe
in dB for an internal attenuator, but it could also be something like
the step number on a current source.  But then it goes through a variety
of circuitry in the VNA before it appears at the CH0 output.



https://www.mouser.com/datasheet/2/196/Infineon_BGA524N6_DataSheet_v03_05_EN-337101.pdf

Kevil 2021/12/10 14:32

I have tested the LNA with the GPS dipole wire antenna 130 mm (lambda*1,25 @ 1575 MHz) tuned by NanoVNA to minimum VSWR 1.541. My GPS LNA PCB will use 2x BGA524N6 to get gain 39.2 dB.

The picture shows the signal from the GPS dipole wire antenna amplified by BGA524N6 Evaluation Board and fed to u-Blox ZOE-M8Q GPS Receiver.

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