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CC1352P7: High PA for +20dBm Tx Output Power Doesn't Work

Part Number: CC1352P7
Other Parts Discussed in Thread: SYSCONFIG,

Tool/software:

Hello,

This is my second attempt to get the answer regarding the issues I am observing on output power in high PA mode. 

I am trying to use +20 dBm Tx output power, however I am seeing some discrepancy on the output if I set the "High PA "to true on sysconfig. For my test I am using a custom PHY setting at sub-GHz. For any setting of power I use upto 12.5 dBm seem to be working fine. For the verification, I am using Siglent SSA3032X spectrum analyzer connected directly to the SMA connecter on the launchpad. 

Let go through the setup and test process, 

Test 1

1) An demo application configured with custom PHY setting as on the following screenshot. 

2) There a continuous transmission while observing the value on the spectrum analyzer. The output power is around +10.2 dBm wihtout the consideration for connector and cable losses. So, it looks to be alright on this configuration. 

3) When opening the sysconfig on the text editor (this is important on subsequent tests), we see the following. (Emphasis on the Tx power)

 

Test 2

1) Custom PHY setting for the second test. Here, the "High PA" is turned on and the power is set to +20dBm.

2) So, we expect the output power to be +20dBm, right? Wrong. On spectrum analyzer we see the output power around -22 dBm. Which is even worse than without turning on the PA. 

3) Interestingly, when opening up the sysconfig in the text editor. We see this. Regardless of what I choose on the output power it is always set to a value from old configuration. But, the "High PA" is set up to True.

One additional test, if I use WiSun instead turning on the High PA automatically sets the output power to 0 dBm. With this however, we do observe the +20 dBm output power. 

 

  • Hi,

    There are three RF ports for the CC1352P7:

    1. 2.4 GHz port

    2. Sub-1 GHz port for Tx up to 14 dBm and Rx

    3. Sub-1 GHz port for 20 dBm Tx only

    These three RF ports all go to a SP3T switch. If you are measuring up to 14 dBm OK, then the switch GPIO are configured for this port. When selecting 20 dBm, this will use a different port on the RF switch so the control lines must be changed. Otherwise, you will have 20 dBm output power that will be attenuated by the switch isolation if the switch control lines are not properly set. If you have typical 30 dB of isolation with your switch, then having the incorrect switch control will produce about -10 dBm at the output.

    Double check your GPIO control of your switch as a first step.

  • I know that there is three port connected to the SP3T RF switch. The sysconfig is default configuration for the CC1352P7-1 LP. The GPIO control configuration look all right. But shouldn't that turn on while turning on High PA as they already have been configured. If not so, does that me I have to manually trigger the High PA GPIO to be high?

  • Hi,

    If you are using the LP-CC1352P7-1 then this should work when you select an output power of 20 dBm.

    Are you using a LP-CC1352P7-1 or your own hardware ?

  • LP-CC1352P7-1. We are using the CC1352P7-1 LaunchPad from TI. All the tests were performed on the same board with it's default board configuration with modification on the board changing the filter cap from antenna to SMA. 

  • Hi Saugat,

    I noticed in your radio_config.c file you are missing pOverridesTxStd[] and pOverridesTx20[] array, which are automatically added by sysconfig to radio_config.c when high PA is enabled. These overrides are needed when the high PA is enabled.

    Have you disabled "include in build" for ti_radio_config.c and ti_radio_config.h in sysconfig?