RTOS/Cc1310: Measurement of Rx/Tx level respectively correct reading RSSI values

Hi Fredrik,

I am absolutely aware of the params that involve my measurement. During my measurement I only changed the angle of device. My aim was finding out the antenna diversity only. Therefor I only needed to be sure that the measured power level of the receiver is correct. "There is no space for an antenna in the device, we need to bend it here that way" is the thing Iam facing in my project . With the measurement I had to find out that the antenna, of course, has got not the "standard diversity" this antenna should have.
With your information Fredrik I still don't understand one thing:
For my tests I needed to prepare a specialized board config for the tool. Otherwise IOs would deactivate electronics immediately. Secondly there is a list of uint16_t values corresponding to a specific Tx power level. For my understanding this means there is no direct connection between values and power levels. If so it is the same for Rx isn't it? When you say the power levels were measured without antenna I guess you optimized the conduction to the chips needed impedance, didn't you? In consequence it means the better the connected antenna is to the needed impedance the more reliable are the indicated power levels to reality? If I use a bad Antenna network the power levels differ to the awaited values as the driver cannot push maximum current to it?

As next step on my side I will try to find out at least for one Tx value which power output is given. I will use again the launchpad as receiver and measure different distances from my module. With this I should be able removing all my unknown Paramus and getting the really "transported power".
Fredrik if I find out the power levels for my module I guess the implemented 802.15.4 of the chip needs those to work correct, doesn't it?

Kind regards

Markus

user5257008 said:

For my tests I needed to prepare a specialized board config for the tool. Otherwise IOs would deactivate electronics immediately

What do you mean by this?

user5257008 said:

Secondly there is a list of uint16_t values corresponding to a specific Tx power level. For my understanding this means there is no direct connection between values and power levels.

There is absolute a direct connection between PA table values and TX power levels. These values are derived from characterization of the device. 

user5257008 said:

If so it is the same for Rx isn't it? When you say the power levels were measured without antenna I guess you optimized the conduction to the chips needed impedance, didn't you? In consequence it means the better the connected antenna is to the needed impedance the more reliable are the indicated power levels to reality? If I use a bad Antenna network the power levels differ to the awaited values as the driver cannot push maximum current to it?

You are mixing up conducted and radiated power and how the antenna gain influences it. As we have no control of the antenna gain in your application we can only provide conducted power levels delivered to the antenna. Actual transmitted power from the antenna is for you to measure.

Sorry Fredrik,

Quite to compact explained. With the tool I mean the Smart RF tool.

Once I choose a cc1310 device in the main panel the secondary window for configurations and test operations appear.

As my module that includes the cc1310 has got some peripherals that will cause undefined behaviour if NO pins aren't configurred correct(e.g.  switch off power supply manually) I created a target configuration for my module.

Within this target configuration there is an index tab called output power. Here I can say, e.g. if I want to send with 2dBm the value 0x231F has to be used. For my understanding it means there is a need for a table inside the cc1310 what value is to set to the RF core reaching e.g. 2dBm. For my tests I used the same values the launchpad has saved within its specific target configuration.

         Fredrik

         You are mixing up conducted and radiated power and how the antenna gain influences it. As we have no control of the antenna gain in your application we

          can only provide conducted power levels delivered to the antenna. Actual transmitted power from the antenna is for you to measure.

In the end my interest is in the radiated power via my antenna. That is what I want to know for e.g. max. distance calculations and so on. I know that we have got several influences that have direct impact on the resulting Rx power level I see from launchpad side. What I want to try is:

1.) Keeping the Tx power (or related value) fixed for my module

2.) Keep the orientation fixed to sender and receiver

3.) Making different distance measurements while 1,2 still are given

4.) Using all information of the launchpad that are there e.g. antenna gain

5.) Eliminating all unknown Params finding out which exact power level the sender transmits

I am using friis transmission equation for it. Of course, I am simplifying this, but for a first idea it will help me.

May I ask another last question about mixing conducting and radiating power? The CC1310 documentations says the optimal impedance of antenna and its network is 44+j15. If the isn't given the transceiver of the cc1310 neither is able to send with expected power level nor can receive respectively transport as much current to the receiving circuit as possible, right? Thus the RF core won't "deliver" the power the application is programmed for, won't it?

I have got here several devices of my type using them inside a mesh network. To have a good overview of them I am using a launchpad as a slip device. As part of 802.15.4 packets each node is sending the Frame check sequence including rssi value. Up to now I don't know if I can believe the values or not. If you say the rssi value is measured in the means of an power inside the rf core then OK. If the measurement expects a line adjusted antenna for correct results it means for my understanding the worse the antenna  the less correct the rssi values are.

Kind regards

Markus

See e2e.ti.com/.../612071 for what the .txPower bits means.

Hello TER,

Thanks for the Link. I think I got this point now: using the same values the launchpad is using should the 're core let drive with expected power level. If the antenna is bad only a part of power is transmitted but the 're core on its own is driving with this strength. So I have to expect the same for receiving signals? If the antenna is bad only a part of incoming signal will arrive the rf core. The rssi the rf core is receiving is seen from input pins of cc1310, right?

In other words the gain of antenna is not included included in all those calculations? The frame checking sequence does not say what power level my device is receiving but what power level the cc1310 itself is?

Kind regards

Markus

user5257008 said:

In other words the gain of antenna is not included included in all those calculations? The frame checking sequence does not say what power level my device is receiving but what power level the cc1310 itself is?

Yes, measured at the 50 ohm point in the RF match.