Tommy, I'm either misunderstanding your email, or you're misunderstanding the purpose of the tool, or maybe both. Some facts:
- If you're unclear about the arguments, just use the default values, they're probably fine. - These tools are only suitable for direct-conversion (i.e., zero-IF) daughterboards and don't work elsewhere. Maybe by "direct frequency conversion" you mean something else (like the Basic boards?) but as I said, you can't calibrate those with these tools. - The duplex-ness of your application is not relevant here, the uhd_cal_rx_iq_balance will calibrate RX IQ imbalance, the uhd_cal_tx_iq_balance will calibrate TX IQ imbalance, and so on. - The way these tools work is that we capture our own signal with our own device, in a loopback mode, so you need to "listen" somewhere for the signal. The Tx cal tools will have an rx_offset parameter to tell the tool where to listen to the signal output. If we set that to zero, then the RX LO could interfere with the TX LO, and that would affect our calibration. - I'm not entirely sure about the exact provenance of the default value, but it is a) small enough to work for all devices and rates, and b) is not a multiple of anything, so it's less likely that the RX can interfere with the TX. The problem with the calibration is that it is single-point (i.e., not frequency-selective). However, if you want to optimize the point where we calibrate, the `tx_wave_freq` parameter is the one you want to tune, and not the `rx_offset`. I recommend you run the tools with the default values, based on your description. --M On Fri, Jun 6, 2025 at 12:40 AM Tommy Tsui <tommyt...@w5tech.com> wrote: > > > Hi, > > > > I have some open questions about tx_offset and rx_offset parameter usage > for the UHD calibration utility uhd_cal_rx_iq_balance, > uhd_cal_tx_iq_balance, and uhd_cal_tx_dc_offset. > > > > The cal util –help output indicates tx_offset is the TX LO offset from the > RL LO in Hz. Likewise, for the rx_offset. If the usrp app uses a direct > frequency conversion and no LO is involved, then tx_offset is zero. One > strange thing is that when the parameter is not specified, the cal util > will use a default value 934400 internally. I don’t know where this > constant came from. Does it mean for direct frequency conversion, I should > specify tx_offset of 0 (to override the default 934400) when performing a > calibration? > > > > My application runs on X310 with 2 UBX-40 installed for duplex operation. > It does specify a Rx LO on the receive and a Tx LO on the transmit, but the > difference between the Tx LO and Rx LO is 40MHz, which exceeds the > tx_offset/rx_offset max limit of 20MHz. Therefore, my only option is to run > the calibration without tx_offset and rx_offset specified, but I wonder how > the calibration result would impact my application performance. > > > > I appreciate it if anyone can share his/her experience on the UHD cal > utility rx_offset & tx_offset usage. > > > > Thanks, > > Tom > > > ------------------------------ > The information contained in this e-mail and any attachments from W5 > Technologies, Inc. may contain confidential and/or proprietary information, > and is intended only for the named recipient to whom it was originally > addressed. If you are not the intended recipient, any disclosure, > distribution, or copying of this e-mail or its attachments is strictly > prohibited. If you have received this e-mail in error, please notify the > sender immediately by return e-mail and permanently delete the e-mail and > any attachments. > _______________________________________________ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-le...@lists.ettus.com >
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