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We are using a 2G modem controlled by an MCU in our device and we want to do an automated test routine that tests our firmware for bad mobile network scenario. How can we create a system where a computer like Raspberry Pi can through software both 'tamper' and 'restore' GSM signal so that the RSSI drops and increases as controlled by software?

We are looking for creating scenario no network connectivity at all, barely any network (say -90 dBm to -100 dBm) and good network (> -70 dBm). Note that GSM antenna connection is through a U.FL connector by using a decent antenna we get -60 dBm in our location.

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  • \$\begingroup\$ Is the Raspberry Pi the MCU that controls your modem, or is it separate? \$\endgroup\$
    – SteveSh
    Commented Sep 22, 2022 at 14:27
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    \$\begingroup\$ A programmable or stepped attenuator in series with your antenna, or someplace else in the the RF path seems like a logical starting point. \$\endgroup\$
    – SteveSh
    Commented Sep 22, 2022 at 14:29
  • \$\begingroup\$ Do have to test with the antenna connected? If not, couldn't you just use a RF signal generator that can generate a proper GSM signal? \$\endgroup\$
    – SteveSh
    Commented Sep 22, 2022 at 15:17
  • \$\begingroup\$ Is this a test that is to be performed on every piece of production equipment, or is it a single device that tests production software? because if it's the latter blow the modem off the board and emulate all it's functions with the PI or or suitable computer. \$\endgroup\$
    – Bryan
    Commented Sep 22, 2022 at 15:54
  • \$\begingroup\$ You need to quantify your pass/fail criteria. \$\endgroup\$
    – SteveSh
    Commented Sep 22, 2022 at 16:54

1 Answer 1

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Consider altering the environment instead of the equipment:

How about get any kind of linear actuator and slide metal plate over the device:

enter image description here

Or a hinged metal box, open and close with a servo:

enter image description here

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    \$\begingroup\$ "How about get any kind of linear actuator and slide metal plate over the device:". You would have to calibrate that setup to determine signal level/attenuation vs position. \$\endgroup\$
    – SteveSh
    Commented Sep 22, 2022 at 15:19
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    \$\begingroup\$ @SteveSh certainly you'd have to do some calibration, but the question is suggesting only three settings: none, barely, and good. None=fully enclosed, Good=fully exposed, "barely": have to test it a bit. \$\endgroup\$
    – jonathanjo
    Commented Sep 22, 2022 at 15:21
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    \$\begingroup\$ @EarthLord - You were probably getting leakage through the seams & hinge joint. Even a small crack can ruin your expected attenuation. \$\endgroup\$
    – SteveSh
    Commented Sep 23, 2022 at 14:21
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    \$\begingroup\$ @EarthLord Yes the quality of the seams will affect it too, probably a lot more than the thickness. See faraday cage for some thoughts. \$\endgroup\$
    – jonathanjo
    Commented Sep 23, 2022 at 15:10
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    \$\begingroup\$ @jonathanjo we haven't had the time to implement this yet. Will comment here once we have results. \$\endgroup\$
    – EarthLord
    Commented Sep 29, 2022 at 12:42

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