Transients at start and end of TX

[Damien]

Hi

We have a product with Nordic nRF9E5 coupled to Texas CC1190 amplifier.

We are seeing transients at start and end of TX; worst at end. We appear to be non-compliant wth en300220.  I have tried reducing Nordic TX power before end of TX (ramping) but the command to change power seems to stop TX immediately and transient occurs.

Any suggestions

Thanks

[ketiljo]

There will be some transients before and after the carrier due to how the PA is switched on an off. So far, this hasn't been a problem even with 10 dBm output power. How much power are you planing to use and what are the level of  the transients?

You can't change any radio parameters while the radio is operating.

[Damien]

Thanks for your reply; I was away, so just seeing it now.
We are hoping to use the full 27dBm that the PA is capable of.
The transient levels vary according to the frequency we are checking on. Typically 0dBm  (Peak detector)

I tried changing radio power level during period after packet TX, while still continuing to TX the carrier.

The observed behavior was:
- stop TX  momentarily,
- produce a transient
- resume TX at lower power
- produce a transient, but of lower level

So I deduce that power level can be changed, but existing TX stops and a "turn off" transient occurs.

( Note that we are trying to comply with EN_303204 which allows 500 mW transmissions in the band from 870 MHz to 873 MHz)

[Damien]

On a related matter concerning  EN_303204 compliance, can you tell me the receiver bandwidth of the nRF9E5? (  I can't seem to find this in the Product Specification document.)

[Damien]

The document "RF Performance Test Guidelines White Paper" contains the following:

"How to set up a specific nRF device for this test can be found in the nRF performance test instructions for each nRF device."

Is there a performance test instructions document available for the nRF9 series?

[ketiljo]

The radio is controlled by a state machine internally. You can't and and should not write to any registers while the radio is on.

Frequency allocation of short range devices in Europe is regulated by ERC 70-03. According to this, maximum output power on this band is 25 mW. This is the case on most of the 868 MHz band. Check the implementation status in the countries you plan to operate in.

The 99% bandwidth will be ~300 kHz

There's no performance test instructions written for the nRF9x5, sorry.

 

[Damien]

Thanks for the reply.

The recent ETSI EN 303 204 standard permits 500 mW transmissions in the band from 870 MHz to 873 MHz. This would be very attractive to us: it is already adopted in several European countries, and planned in others.

However, our preliminary tests suggest that we will have difficulties complying with at least two aspects of this standard:
- Transient Power (because it specifies Peak detector rather than the RMS detector  that is in EN 300 220)
- Adjacent Channel Selectivity which, based on 300 kHz receiver bandwidth, will have limit of - 22.3 dB; the nRF9E5 seems to have a figure of -7dB for this.

Comments welcome.

[ketiljo]

870-875.6 MHz is listed as Annex 2, band d2 at page 13, with 500 mW but the use of this is limited to data networks. Licencing may be required. 

We haven't tested the nRF9x5 against EN 303 204 as has always been EN 300 220 that has been a requirement. EN 303 204 may have requirement the nRF9X5 won't pass.