Hi, I'd like to create (imitate) the sinc(f/fs) spectrum that would be generated from an unfiltered zero-order hold DAC output, clocked at 10 Mhz. Main characteristics are a peak around center frequency, rolling off to nulls at +- 10 MHz around the center frequency.
The IF signal is a random BPSK sequence. When I stream the BPSK sequence at 10 MHz , I get a flat spectrum between +- 5MHz since the DUC is doing its job in upsampling to 200MHz DAC rate. I have tried to add skip_duc=1 which is mentioned in some of the documentation, but the output spectrum does not change. Is this command outdated or not supported? I wonder since the HG FPGA image has listed that the routing between DUC and radio are "static". I have noticed that I get something closer to what I want if I choose an odd interpolation order, by setting master_clock_rate to 190 MHz instead of 200MHz. The upsampling ratio becomes 190MHz/10MHz = 19, which is odd, and I get some warnings about half-band filters and CIC roll-of in the console. In this mode, what does the DUC do to the signal? Is it equivalent to bypassing the DUC? How do I best avoid any effects introduced by DUC? Regards, Andreas. ________________________________ CONFIDENTIALITY This e-mail and any attachment contain KONGSBERG information which may be proprietary, confidential or subject to export regulations, and is only meant for the intended recipient(s). Any disclosure, copying, distribution or use is prohibited, if not otherwise explicitly agreed with KONGSBERG. If received in error, please delete it immediately from your system and notify the sender properly.
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