Hi, I sincerely apologize for the inconvenience... Reading the warning prompt, it is specifically pointed out that the bandwidth requires an even ratio.... Setting it to, e.g., masterClockRate/4 does not cause a "hump".... Once again, I apologize for stealing your time.
Kind regards, Tobias ________________________________ Von: Marcus D. Leech <[email protected]> Gesendet: Montag, 11. April 2022 16:41 An: Tobias Kronauer <[email protected]> Cc: [email protected] <[email protected]> Betreff: Re: AW: [USRP-users] Re: [x410] Frequency Selectivity? On 2022-04-11 07:07, Tobias Kronauer wrote: thanks for your prompt reply! Indeed, my description was lacking a bit of details. In short: - We transmit with 50MHz sample rate and 400MHZ analog bandwidth (according to RF config setup) - We generate a signal that consists of sections with pure (complex) tones of different frequencies with constant amplitude, ranging from -25MHz to +25MHz frequency in baseband (-25, -19.5, -14, -8, -3, 3, 8, 14, 19.5, 25). - We receive the signal on the same USRP and plot the time domain of the TX and RX signal. (first figure row) - As visible, already the 8MHz tone is attenuated by around 3dB compared to the center frequency. Higher frequencies are more attenuated. This is also visible in the spectrogramm. We know and expect that the passband of the X410 is not totally flat. However, we do not expect the passband to be as severely shaped as we measured. We know we cannot expect the edges to be not attenuated, but actually we would have expected at least say -20..20MHz to be relatively flat (for 50MHz sampling rate). Hence we wonder: - if the problem can be reproduced on your (or other's side)? - if the seen behaviour is correct and more flatness cannot be expected? Thank you. I updated the plot as well. How are you connecting your TX and RX? Antenna or direct-wired? If direct-wired, make sure that your cable has at least 30dB of attenuation in it and that your TX power levels aren't producing more than about 0dBm at the output. With a master clock rate of 250MHz, 50Mhz delivered bandwidth requires an odd decimation rate. This has historically caused a passband response with a half-band "shape" that is like a "hump" as you describe. I don't know whether this applies to X410 or not. It REALLY would be helpful for you to plot the RX response using a normal FFT plot--with the gain turned up and a terminator on the RX input, you should be able to see the instrumental response of the device. The "uhd_fft" example code with Gnu Radio produces nice plots for this sort of thing. Barkhausen Institut www.barkhauseninstitut.org Barkhausen Institut gGmbH | Sitz: W?rzburger Stra?e 46, 01187 Dresden, Germany | Registergericht: Amtsgericht Dresden, HRB 37267 | Gesch?ftsf?hrer: Prof. Dr. Gerhard Fettweis, Dr. Tim Hentschel | Vorsitzender der Gesellschafterdelegation: Dr. Andreas Handschuh Hinweise zum Datenschutz und zur Verarbeitung Ihrer Daten finden Sie unter: https://barkhauseninstitut.org/data-privacy This email and any attachments are intended only for the person to whom this email is addressed and may contain confidential and/or privileged information. If you received this email in error, please do not disclose the contents to anyone, but notify the sender by return email and delete this email (and any attachments) from your system. Information on data protection and processing of your personal information: https://barkhauseninstitut.org/data-privacy
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