CC1101: cc1101 Occupled Bandwidth too high

readlove1 readlove1

Part Number: CC1101

The Occupled Bandwidth is 711.66KHz, while the testing mechanism requires less than 300kHZ. Which parameter should I tune on the software, DEVIATN or data rate? Is it bigger or smaller?

over 8 years ago

0 TER over 8 years ago

TI__Guru**** 317180 points

You are free to program the CC1101 with your wanted datarate and deviation. In addition you can select a different modulation if you so want.

If you require lower OBW you have to use a lower datarate/ deviation. What are you using today and why?

0 readlove1 readlove1 over 8 years ago in reply to TER

Prodigy 115 points

I'm using 2-fsk modulation. Can the data rate reduction reduce the width of the occupied bandwidth? Does deviation reduce the width of the bandwidth that can be taken?

0 TER over 8 years ago in reply to readlove1 readlove1

TI__Guru**** 317180 points

I meant which datarate/ deviation you use today.

The signal bandwidth could be approximated as follows:

Signal BW of = Data rate + 2 x frequency deviation.

The equation is valid for FSK, for GFSK the signal bandwidth is less.

Try the different settings in Smart RF Studio and see the effect on OBW.

0 readlove1 readlove1 over 8 years ago in reply to TER

Prodigy 115 points

Data rate:48.0042kBaud
Deviation:5.157471KHz
Base Frequency:868.299866MHz
Carrier Frequency:868.299866MHz
Xtal Frequency:26MHz
Modulation Format:2-FSK
RX Fiter Bw:58.035714KHz
Channel Spacing:199.951172KHz

Signal BW of = Data rate + 2 x frequency deviation

58.319142=48.0042 + 2*5.157471 Is there any error in this formula?

Thanks!

0 TER over 8 years ago in reply to readlove1 readlove1

TI__Guru**** 317180 points

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/156/48k.WMF

No, here is the spectrum when I measured with the parameters you gave.

Note that setting the deviation very low compared to the datarate will give poor performance on the RX side.

0 readlove1 readlove1 over 8 years ago in reply to TER

Prodigy 115 points

How much is the Deviation setting ?

0 TER over 8 years ago in reply to readlove1 readlove1

TI__Guru**** 317180 points

In the plot I posted I used 5.15 kHz deviation. Normally the deviation is set to 0.25 to 0.5 times the datarate to get optimal reception.

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CC1101: cc1101 Occupled Bandwidth too high