Regarding nRF51822 Range Extend

[Nazmus Sakib]

Hi All.

For my project I need a very long range BLE Communication. Don't know if its possible to get a range close to 1 Mile LoS. But my goal is to meet max possible range.

I made a custom Board using nRF51822 and with good RF tuning I have achieved close to 200 Feet LoS range using Chip Antenna. Now I like to have your advise regarding implementing RF Power Amp to get a max possible range.

Ca anyone share a such reference design of nRF51822 with PA implementation? Or any good PA chips?

Thanks in advance.

Awaiting for your revert.

Regards.

[Asbjørn]

The Bluetooth core spec states that you cannot have Bluetooth Smart (Low energy) with more output power than +10 dBm. Also, you would have to implement a PA on both ends of the link in order to make this work unless you only want to broadcast.

If you already have control over both ends of the link I would recommend you to have a look at running this with proprietary 2.4 GHz implementation on the nRF51822 instead. Then you can in addition turn down the on-air-data rate to 250 kbps and get additional dB on you link budget from that.

Regarding PA we don't have any specific vendor we recommend. You can use any kind of PA made for 2.4 GHz. That includes PA designed for WiFi and Bluetooth. We have seen some interest regarding a PA from RF Axis, but we haven't made any tests or designs on this ourselves, it's just a vendor name I've seen other customers have been asking about. Remember to follow our recommended layout and the PA vendors recommendation with regard to implementation.

[Nazmus Sakib]

Hi Asbjørn.

Thanks much for reply.

Actually my project need both communication. Device to Device (for Bidirectional Data) as well as Device to SmartPhone (For Bidirectional and Broadcast).

In this case, as Device to SmartPhone also needed, so I am not able to choose other RF than BLE.

I have some more ques:

• To achieve Extend Range, do I need to consider LNA too? Or only PA will be Ok? There are some RF Front-End (PA+LNA) Chip ... do I need to consider that?

• My project don't need always Extend Range of communication. So, when short range communication is needed, then I wanted to Bypass PA (and back to +4dBm) to save Power. In summery, I want to have an option to enable/disable PA (to Switch from Extend to Normal Range Mode and Vice-Versa). Is there any way to do this?

• With +20dbm Output Power and good Antenna (Chip) Tuning ... what can be the max LoS Range in practical?

Waiting for your comment and advise.

Regards.

[Asbjørn]

Q1: You can use an LNA, but our experience is that it won't give you any improvements on the link. This is due to the fact even though you get better sensitivity you also keep the same blocking performance and noise will be amplified as well in the same degree the actual desired signal is. So at best you end up with a much higher current consumption, but not much over all improvement on the link.

Q2: You could do this by using a RF switch and control this from a GPIO.

Q3: Normally with 0 dBm output power in both ends we say that you can achieve 15-20 meters indoors and twice that LoS. That's usually a good estimate for the average use, but of course it can be much worse and it can be better depending on the implementation. So if you start of with ~40 meters LoS and then add 20 dB. Every 6 dB is double the range, so you could in theory have something around 300 to 350 meters. Estimating range is difficult as there are a lot of parameters outside our control that could affect this. This estimate is based on experience from testing application in our office.

[Nazmus Sakib]

Hi Asbjørn.

Thanks for explaining abut PA and LNA.

For now I am thinking to use the below PA.

www.skyworksinc.com/.../SE2604L_202437B.pdf

can you please comment if its a good choice with nRF51822?

Regards.

[Floyd Ashbaugh]

Nordic nRF51_Range_Extension_with_RFaxis RFX2411N_Rev2.0.pdfHere at RFaxis, we are dedicated to providing high quality low cost range extension solutions that integrate well with the Nordic BLE transceivers. I have attached a white paper written specifically about the nRF51 including test results and application schematics. Please refer to www.rfaxis.com for more details. Floyd Ashbaugh Applications RFaxis, Inc.