nRF24L01+

[JasonWu]

Dear Nordic engineer,

        Here is a question when we use the chip's automatic response function, the MCU PRX can download the packet, but PTX can not receive the ACK signal every time. I want to know why this is the case, or what causes the ACK signal can not always be received.

        We are extremely anxious to know why, which is very important for our products to achieve mass production. Hope you to answer it as soon as possible.

        Thanks

        Best wish!

Jason

[ketiljo]

Try connecting the shield of the coax cable to the module, the antenna won't work well without this. So it's possible that it's the antenna that causes the ACK to be lost. You might be better off using the U.FL connector that was (?) on the module with a corresponding connector on the antenna coax.

Note that if you get the module from another place than our distributors, it's a chance that the nRF24L01+ chip may be counterfeit and may have reduced RF performance. 

[JasonWu]

Thank you for your answer. We will connect the coaxial cable to the module according to your method. Then test the receiver performance.          

However, according to your method, there will be some electromagnetic compatibility problems, such as electrostatic discharge immunity test. Static electricity will enter the PCB board through coaxial cable, causing damage to the equipment.

[JasonWu]

Do you have any good ways to solve this problem?

[ketiljo]

That must be solved by using special protection diodes if necessary. Disconnecting ground isn't the way to protect a radio against ESD 

[JasonWu]

Does this special protection diodes have a recommended model? and which position does the diode add to our board?

I'm very sorry that my expression may not be very clear when I describe the problem.by the way, the function of my device is to transmit a message from one device to another(like a bridge).  For example, the signal comes from a temperature sensor is received by our device , and then sends to another device. That means our device firstly is in RX state and then changes to Tx state when received message.  The secitivity of Rx AND Tx is OK, but only sometimes lost ACK when Tx status at A rate about 40%.

antenna.docx

[ketiljo]

There's no reason for just ACK to be lost like this. Connect the antenna properly first and then check how it works. 

ESD protection diodes for RF must have very low capacitance, < 0.5 pF. Protection on the antenna pin is rarely needed though.