CC2640 conducted power

Hi Ameya,

I will forward this question to our HW expert.

- Cetri

Hello Fredrik,

I am using spectrum analyzer to measure conducted power. Spectrum analyzer will show relative power only right? because noise level (reference) will change according to RBW setting hence peak power will also change. Any idea how to measure absolute power? Is it possible to measure conducted absolute power using spectrum analyzer or you have any setting value of RBW, VBW and power measured for reference so that I can conclude whether o/p power at DC block is 5 dBm or not?

Hi Ameya,

The spectrum analyzer will measure absolute power. RBW does not matter that much as long as it is wide enough to include all the power in the signal. You can for example transmit an unmodulated signal and use a quite narrow BW.

Cheers,
Fredrik

Hello Fredrik,

Thanks for your quick reply!
1. Actually I measured conducted power after pi filter with RBW= 1 KHz, VBW= 3 KHz, Attenuation= 0 dB, Power was about -12dBm. Again I measured power with RBW= 10 KHz and VBW= 30 KHz, attenuation=0 dB, I measured power as -1 dBm, so why was there shift with change in spectrum analyzer setting?

2. If I keep BTLE device in advertising mode, transmitting unmodulated signal then each of three channels of advertising mode will read around 5 dBm, right?

3.If modulated signal is being measured then how much will be deviation in conducted power?

Hello Fredrik,
Can you please also tell transmitting narrow BW unmodulated signal means what shall be BW?

RBW = 1 kHz is a very narrow BW. If you use this on a modulated signal you will only measure a part of the power. I would recommend changing RBW to 1 MHz.

You can use smart RF studio to transmit both unmodulated and modulated continuous signals. The same can be achieved with HCI commands, these are listed in the SW Developer Guide.

Ok I will keep RBW = 1MHz , can you please also specify other settings like VBW, sweep time, attenuation?

You can typically use the auto settings.

Hello,
BTLE advertises on 3 channels, 2.40, 2.42 GHz, 2.48 GHz. Shall I kept 80MHz (2.48GHz - 2.40GHz) as bandwidth and measure power?

Or is it possible to have only one advertising channel?

You must configure the radio to transmit continuously on single channels. You can use a HCI command for this. See the production test article on the BLE wiki for details.