[Farhad Hagh Panah ShirvanParticipant]

Hi guys,

I have designed the system but I have no idea why the received 16 QAM constellation is strange. I would be grateful if you would kindly help me to find where the problem is.

Regards,

Attachments:

1. 

   Image.jpg
   

1. Heterodyne_test_5km.osd

[Farhad Hagh Panah ShirvanParticipant]

Hi Alistu,

I tried to simulate with lower Sample-per-bit numbers but although carrier frequency of QAM was on 60 GHz, RF Spectrum analyzer was showing the output signal of the Quadrature Modulator around very lower frequency (if my memory serve me right, I set the QAM’s frequency on 60 GHz and Sample-per-bit on 128 and got a signal at frequency of ~10 GHz at the output of Quadrature Modulator), so I increased the Sample-per-bit to 1024 in order to satisfy Nyquist criterion such that sample rate be greater than the twice as highest frequency of system (sampling rate>2*60 GHz). On the other hand when I decreased the number of sequence length, Software got an error in calculations and terminated when software was calculating the OFDM Demodulator.

Regards,

[Farhad Hagh Panah ShirvanParticipant]

Hi Gokul,

Yes. The problem was pertained to the considerations regarding amount of bit rate and sampling rate (Nyquist–Shannon sampling theorem) which I had overlooked; thanks to Damian for reminding that. My system was working until I added the fiber. Then I found that sampling rate at OFDM Modulator is decreased (I don’t know why). Since I need to do the simulations at 60 GHz, sampling rate must be twice as higher than highest frequency in the system. So, I increased the ‘Sample per bit’ at Global parameters from 512 to 1024 and now the simulation is like a never-ending-thing.

Regards,

Attachments:

1. 

   Untitled21.jpg
   

1. OFDM-16QAM-LTE_1024SC_20MHz_at-60-GHz-1024-sample-per-bit-with-fiber1.osd

[Farhad Hagh Panah ShirvanParticipant]

Hi Alistu,

I’m afraid not. Because calculations regarding the fiber is done successfully. So far the only process that cannot be successfully done is RF spectrum analyzer in high sample-per-bits as I need to run the system at 60 GHz I need 1024 samples per bit.

Regards,

Attachments:

1. 

   Untitled2.jpg
   

1. OFDM-16QAM-LTE_1024SC_20MHz_at-60-GHz-1024-sample-per-bit-with-fiber.osd

[Farhad Hagh Panah ShirvanParticipant]

Dear all,

Thanks for your answers, Alistu and Dhananjay. You helped me a lot. In my case in order to take carrier frequency to 60 GHz; due to Shannon sampling theorem, I’ve increased ‘Samples per bit’ in Global parameters from 64 to 512 but; as you can see in the attached picture, suspiciously the simulations took so long (more than 12 hours) as RF Spectrum Analyzer can’t be wrapped up. I was wondering if anyone knows where the problem is.

Yours sincerely,

Attachments:

1. 

   Untitled1.jpg
   

[Farhad Hagh Panah ShirvanParticipant]

Hi Rend Alrays,

I am working on a project and need to generate LTE OFDM signal with 1024 sub-carriers and 20 MHz of signal width (channel band width). The only problem I have so far is that my signal width (channel bandwidth) is ~1 Ghz and don’t know how to generate signal with width of 20 MHz. I have also raised this problem in an other top that I created yesterday and extremely need the solution for it.

Best regards,

[Farhad Hagh Panah ShirvanParticipant]

Hi Alistu,

I have checked them and actually the file I have uploaded is the modified version of the Direct Detection OFDM 4QAM file. I’d like to generate an 16QAM LTE OFDM signal with the bandwidth of 20 MHz, 100 Resource Blocks, and 1200 sub-carriers. Thanks a lot in advance.

Best regards,

[Farhad Hagh Panah ShirvanParticipant]

Hello Damian,

I working on a very similar project. How can I use “OFDM Modulation (OS12)” instead of current “OFDM Modulation” in the osd file you reformed? My project has been attached to this message. I would be grateful if you would kindly help me out.

Best regards,

Attachments:

1. LTE-RoF.osd