Not achieving expected blocking performance on CC1200

Could you please write which frequency, datarate, modulation and deviation used? Could you post the settings used?

The attachment contains exported settings from the “SmartRf Studio 7” for the following tests:

1)  Frequency 915 MHz

Rx Filter BW: 230 kHz

Symbol rate: 115.2 kbps

Modulation: 2GFSK

Deviation: 68 kHz

 8640.CC1200_915MHz_Rate115_2kbps_Dev68kHz_RxBW230kHz_2GFSK .h

2) Frequency 915 MHz

Rx Filter BW: 280 kHz

Symbol rate: 115.2 kbps

Modulation: 2GFSK

Deviation: 68 kHz

 4442.CC1200_915MHz_Rate115_2kbps_Dev68kHz_RxBW280kHz_2GFSK .h

3) Frequency: 915 MHz

Rx Filter BW: 230 kHz

Symbol rate: 172.8 kbps

Modulation: 2GFSk

Deviation: 68 kHz

 1732.CC1200_915MHz_Rate172_8kbps_Dev68kHz_RxBW230kHz_2GFSK .h

4) Frequency 915 MHz

Filter Bandwidth 330 kHz

Symbol rate: 172.8 kbps

Modulation: 2GFSk

Deviation: 68 kHz

6874.CC1200_915MHz_Rate172_8kbps_Dev68kHz_RxBW330kHz_2GFSK .h

We can’t reach declared in the data sheet “Low Power, High Performance RF Transceiver CC1200”parameter “Blocking and Selectivity 100 kbps 2-GFSK, 50 kHz deviation,

208 kHz channel filter Freq ± 2 MHz , which should be 63dB.

I haven't had access to a test system today so I haven't been able to look into this in detail but a couple of observations:

SYNC_CFG0.RX_CONFIG: Why is this set to '1'?

Case 1 and 3, have you checked that your signal actually fit into the RX bandwidth you are using?

The parameter SYNC_CFG0.RX_CONFIG_LIMITATION is set to 1 when RX Filter BW is less than 2*SymbolRate. We tried both SYNC_CFG0.RX_CONFIG_LIMITATION=0 and SYNC_CFG0.RX_CONFIG_LIMITATION=1.

We have better reception (less missed SYNCs and errors) using these RX Filter BWs in cases 1 and 3. We tested these settings on Evaluation Board and on our hardware.

The SmartRF Studio doesn’t give us optimized parameters that match all users’ requirements: there are just most popular combinations of settings.

The “CC120X Low-Power High Performance Sub-1 GHz RF Transceivers User’s Guide” refers very often to the SmartRF Studio without any explanations. Could TI provide any other more detailed information?

Is it possible to get optimized settings for the following link rates:

1)      Link rate 115.200 kbps, Freq. Deviation 58 kHz, 2FSK

2)      Link rate 172.800 kbps, Freq. Deviation 58 kHz, 2FSK

3)      Link rate 9.600 kbps, Freq. Deviation 3.6 kHz, 2GFSK

I plan to look at this in more detail when I get access to a test system... Do you have a typo in 1) and 2)? The cases in one of the first posts stated GFSK, now you state FSK.

They tested both 2GFSK and 2FSK. Their current modems use GFSK.

Please find settings and blocking results in the attached excel file. 1234.E2E_settings.xlsx

The sync word chosen is not optimal. If they get issues with false sync in the field they should use SYNC_CFG0.STRICK_SYNC_CHECK=0.

These settings are for FSK, for GFSK the SYNC_THR should be set to 7 or 8. Note that when increasing the RX BW the blocking performance will go down, hence the small difference between the datasheet values and these results.