Re: [Discuss-gnuradio] IEEE 802.15.4_OQPSK PHY Constellation issues

[Bastian Bloessl]

Hi,

On 05/23/2017 02:45 AM, Tellrell White wrote:
> Hi All,
> I'm currently using the the IEEE 802.15.4 testbed developed by Bastian 
> Bloessl, and company, specifically the offset-qpsk PHY. The only changes 
> I've made to the flow-graph developed by Bastian is adding  a vector 
> source consisting of 0's and 1's as my input source and adding a 
> constellation sink. I've attached the flow-graph for reference. When 
> running the flow-graph, the output of the constellation doesn't look 
> quite correct. For instance I'm not quite sure why there are 
> constellation points at 0 + j and 0 - j as well as at 1 + 0j  and 1- 0j. 
> A picture of the constellation plot is also attached.

I'm not sure what you are irritated about. With OQPSK you don't change 
abruptly, but transition from one constellation point to the other on a 
circle. Depending on the sample rate, there are multiple points 
in-between the final constellation at +-0.707 +- 0.707i. (in that case 
it is just one).


Best,
Bastian