Amplifying nRF24L01P signal

[kwas]

Hi guys,

I am trying to use a TM2001 amplifier (Taiwan Microelectronics, google returns the PDF) to amplify the signal from an nRF24L01P.

The TM2001 seems to accept a 50ohm signal. I use the "application example" on the nordic chip on page 66.

I simply connect the TM2001 RADIO input to the 50 ohm line instead of a chip antenna. Then TM2001 has its own output which goes to an antenna.

I have used TM2001 before with no problems. However now it is giving very strange effects.

There is way too much power consumption from it. If I touch the antenna it affects how much power is drawn. No radio output is observed unless I artificially raise the resistance of the battery supply (by adding a 10 ohm resistor). Is it delusional to think that I can just hook up the TM2001 like I described? The only part of this circuit I don't understand is the inductors/capacitors between ANT1 ANT2 and VDD_PA. Are the inductors causing this problem? Should I just connect ANT1 or ANT2 to the TM2001?

thanks

[Andreas]

Hi,

 

What you describe is the correct way to go, the RADIO input should be connected to the 50Ohm trace in the application example, it should not be delusional at all.

 

The high current consumption should indicate that it is on at least. For reference what kind of current consumption are you seeing? The fact that it changes if you touch the antenna is probably because touching the antenna will change its impedance, thus changing the load impedance of the PA. Have you tuned the antenna?

 

The inductors/capacitors between ANT1/ANT2 and VDD_PA should be as it is, power is supplied to the nRF radio from VDD_PA through the ANT pins. You can use VDD_PA to toggle TX on, but you can not draw power from it. I am not able to decipher from the product description I found if this is the case or not.

 

Best regards,

Andreas

[kwas]

Hi,

I've tracked down the issue to the NRF24 forgetting register settings.

For instance, I set channel to #10. The first packet is sent on channel 10. Any subsequent packets are sent on channel 2 (default).

I have two boards. On one, powering the board from Pickit (bypassing the regulator) solves the problem. On the other one it does not. I tried soldering, resoldering all ICs, substituting new ICs thinking that they were broken, but it did not help. The power supply is good at 3.3V.

Under what circumstances will the NRF reset itself and lose register information?

[kwas]

Tried several TM2001, there is only one that works when dropped into either board. All these TM2001 chips all work when used with another RF module (not Nordic). Something tells me that something about TM2001 (which may have some inter-part variation) is interfering with the ANT circuit, either inside NRF24 or in the balun/matching circuit from the application example :(

[kwas]

After trying all possible permutations, it appears as if a 56 ohm resistor is needed between NRF24 output (after the matching network) and before TM2001 radio input. Without this only one TM2001 out of many works properly when duty cycling. Without duty cycle, they all work.

Is this reducing my radio power? What is the reason that this makes it work?

[Andreas]

Hi,

 

This is very strange. It would be interesting to have a look at your schematic and layout files, feel free to create a new private case if you do not want to share the files publicly.

 

Best regards,

Andreas

[kwas]

How can I post files? I have Mentorgraphics PADS SCH and PCB files.

[kwas]

New information

- it's a NRF24L01 not the + version

- even with the 56 ohm resistor, if I touch the bottom of the board (ground) the radio stops (not everything else).

I noticed that the non-+ version needs a 1M R across the crystal, is that just because of the specific crystal that is used in the demo board? I have a crystal I have been using with a series R not parallel and it seems it won't work without series R and with a parallel R. I haven't tried using both yet but I will.

[kwas]

Adding R1 (1M across crystal leads) does not change anything. Touching ground wipes NRF registers. Only when I reset the MCU and it reinitializes, does it start transmitting again. Same issue with not using 56 OHM resistor, it sends one packet and then dies. What could be wrong? Do you have an email I can send files to?