On Tue, Jun 23, 2020 at 10:38 AM Manav Kohli <mpk2...@columbia.edu> wrote:
> Hello, > > This problem is visualized here: > https://www.dropbox.com/s/w7kdmf9dewwdomx/20M_2974_20_15_nocal_packet_time_tx.png?dl=0 > > This is an OFDM packet consisting of 6 symbols: the default sync word 1&2, > SIG field and three data symbols. The data symbols are QPSK modulated and > the sync words are BPSK. > > Is there any way that I could reduce or eliminate these large spikes that > even with a moderate baseband scaling still go considerably above a > magnitude of 1? I have tried to use different data, and a different number > of packet data symbols, but to no avail. I am definitely able to reduce the > overall baseband scaling and get those spikes within range, but this is not > desirable as I am trying to maximize transmit power. > > The usage of the USRP-2974 and sampling rate is immaterial; this happens > using a variety of different radios (should not matter as this is a GNU > radio "issue") and sampling rates. > > If anyone has seen this before or may have any advice, please let me know. > It's the nature of OFDM to have a high Peak-to-Average-Power Radio (PAPR). You can look at PAPR reduction techniques, but otherwise you're in for around 10dB PAPR. Good luck. Brian >
