Why I get another spectrum when upconvert an o-qpsk baseband signal with a bladerf compared to a hackrf device? I have just start working with bladerf instead of former used hackrf hardware and I need to solve a problem. Currently I use the following bladerf hardware, libraries and firmware:
bladerf (2.0 micro xA9)
libbladeRF version:         2.2.0-2018.12-rc3-2-ppabionic
Firmware version:           2.3.2
FPGA version:               0.10.2 (configured by USB host)
I tried to simply upconvert an oqpsk baseband at 1100 MHz (4 Msps) with bladerf device using
gnuradio (GRC 3.711) block osmocom-sink and I got a unexpected and pretty wierd baseband spectrum compared to hackrf hardware.
For better understanding, I have attached some hardcopies:




From my point of view, I made identical setups for hackrf and bladerf device on osmocom-sink block. Later on downconverting and demodulation works very well with hackrf hardware, with bladerf device it totaly fails.
Any suggestions, I need to check or I just made wrong ? May I need to calibrate the bladerf hardware first for proper baseband processing ?
Many thanks in advance.
Best regards
calenberger
One source of this is spectral regrowth (overdriving a device into saturation such that the pulse shaping that limits the spectrum is degraded), but compared to typical spectral regrowth spectrums I have seen, this looks more like your signal was greatly attenuated and then amplified together with noise, and then that combined signal passed through a bandpass filter. Check if there is a 5 MHz filter earlier in the Tx chain to further support this theory, and then also try to reduce the power level at the input to the device.