Is measuring RSSI enough for mass production?

Question

Hi, 
 
 In production line, I was supposed to do BLE test using DTM with UART interface and MT8852B from Anritsu. 
 However, the antenna is specifically tuned for plastic enclosure assembly. 
 After assembly, UART interface is no longer exposed so I think I cannot conduct BLE test using DTM. 
 I can just do BLE test before assembly but I doubt that whether I can get meaningful test results without the enclosure. 
 So I think the only way to test BLE after enclosure assembly is measuring RSSI and pairing test. 
 I would like to ask that it's enough and safe for mass production instead of using DTM. 
 Thanks.

run_ar · Accepted Answer

Remember that our chips are tested and screened in our factory before they are shipped to distributors/customers. So as mentioned above a minimal test level would be to use rssi or an attenuator to check that the tx power level is higher than a given threshold. (chek the level of a good product and use that as a reference when setting the limited for screening) 
 You could also use a proprietary input to change channels/mode during dtm testing as explained in this app note from anritsu . 
 There are also companies like Litepoint that can measure tx power and rx sensitivity +++ based on advertisement and scan response packets.

AmbystomaLabs · Answer

RSSI is normally a composite number for all BLE channels. Doesn't really represent the variations you will likely see across the whole ISM band. You can use RSSI for power output if you do custom code and measure it while exclusively on a channel. Your test jig will have a big affect on the numbers. Measuring near field power can be plagued with inaccuracy. Small changes in the position of the EUT or someone just placing their hand in wrong place can make the numbers go up or down. Spend time on making a nice reliable test jig. 
 Also, RSSI says nothing about channel accuracy and receiver functionality. 
 A minimum test plan would be power output and channel accuracy on 3 ism channels (low, mid, high) and a similar receiver test with current monitoring so you can verify the board draws the correct current during these tests. Then you just need some sort of functional test where some packets go back and forth from test station to EUT.