RSSI jump observed using attenuator

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wisilica
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RSSI jump observed using attenuator

Hi,

We are performing RF and rssi testing on the DA14585 chipset using SDK 6.0.2. We are using DA 14585 daughter board connected to the DA 14580 PRO development board. The Dialog board connected to one channel of the attenuator, advertises packets every one second, and the same were captured by a scanning device connected to second channel of the attenuator. The attenuation provided was gradually increased in steps of 10dB, and was varied from 10dB - 100dB. On analysis of the rssi of the packets captured, it was observed that, for each case(10dB - 100 dB loss), rssi values received varied drastically. For instance, when the PRO board was powered through CR2032 coin cell battery, for an attenuation loss of 50dB, the rssi values obtained were not constant, and fluctuated between the range 48dBm - 70dBm (HEX), which corresponds to a range of 40dBm(in decimal). This wide fluctuation was observed for all the attenuation test cases. Please suggest the possible reasons for the same. Also, please explain how accurate the rssi values of the dialog device are.

Thanks
Wisilica

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MT_dialog
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Hi wisilica,

Hi wisilica,

What is the device that is acting as a central and gets the RSSI from the advertising string of the device is it a 585 or a generic device? For the fluctuations that you are observing can you please perform some conducted measurements (in case that the above wasn't) and check if you are still observing the same variations in the RSSI ? Also have you performed the measurements without the attenuator and check if the fluctuation occurs from that ? Regarding the accurancy of the RSSI is indicated in the datasheet, about 2db.

Thanks MT_dialog 

wisilica
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Hi,

Hi,

The scanning device is a CSR 1010 module. I am concerned with the range of rssi values given out by the transmitting device in each case. I could not find infromation regarding this in the datasheet. The accuracy of 2dB in rssi values as mentioned in the datasheet is applicable in the case when the DA 14585 acts as the scanning device and captures other BLE packets know.

Thanks
Wisilica

MT_dialog
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Hi wisilica,

Hi wisilica,

The RSSI stands for Receiving Signal Strength Indicator, that means that its the signal strength that a device is getting from the remote device (how strong is the signal that reached the peer device), the accurancy of the RSSI can only be given when the device operates when receiving (not solely as a scanner but in case the device gets data), so when the 585 receives data the accurancy of the RSSI is 2db, there is no RSSI when transmitting data, this has to do with the device that receives the data.

Thanks MT_dialog

wisilica
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Hi,

Hi,

Thanks for your prompt reply. The rssi received by the scanning device has a wide range. I was wondering if that happens due to the fluctuation in the tx power of the 585 transmitter device. The tx power of the 585 device was set to 0dBm. But on analysing the output using spectrum analyzer, the tx power captured varies between 0 - -5dBm. Please suggest the possible reasons for the same.

Thanks
Wisilica

MT_dialog
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Hi wisilica,

Hi wisilica,

I suppose that this question is related to this post https://support.dialog-semiconductor.com/forums/post/dialog-smartbond-bl... can you please check that instead.

Thanks MT_dialog