11-13-2015 01:18 AM
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.
11-16-2015 03:35 AM
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?
11-16-2015 04:54 AM
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.