wireless communication between two pxi chasis equiped with FlexRio module

[wangminfeng]

i am trying the 802.11ac wireless communication between two PXI chasis. each PXI chasis is equipped with a control, two fpga module named FPGA7966 and RF module nemad NI5791. so this system have  2 TX antennas and 2 RX antennas.besides ,it is OFDM system.

but at the receiver, after equlization ,the constellation is as follows:

i have considerd the LO offset of the different RF module, can anyone do the same research or can explain this phenomenon? thank you.

[darkpirate12]

Hi Wangminfeng,

I saw your constellation, seems it was totally srewed. I have one question, you mention your system has 2 TX and 2 RX, so this is a 2x2 MIMO system? 

And what is the constellation represents? one of the RX? 

[wangminfeng]

thanks for your reply.

i have four flexrio, each flexrio is equiped with one TX antenna and one RX antenna. i use two of them act as transmitter and another two act as receiver. in this way, it is a 2x2 MIMO system, and local oscillator offset exists between the transmitter and receiver.

the picture represents constellation of one TX.

i have respectively done carrier frequency offset compensate for baseband data in time domain after frame synchronization  . the constellation plot the data after equalization. it is hard to explain this phenomenon.