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Robin Coxe coxe at close-haul.comIt might make sense to do some thermal cycle tests with a few temperature sensor breakout boards like this one: https://www.sparkfun.com/products/9418 On Sat, Jul 28, 2012 at 11:17 AM, Andrey Sviyazov <andreysviyaz at gmail.com>wrote: > Hi Srdjan. > > Can we measure of all important for us instabilities of calibrations vs > temperature and then write it to EEPROM for mass production? > I mean, do you have information about repeatability of curves (laws) of > deg C instabilities for chips with same and different date codes of > manufacture? > > Also, how near should be temperature sensor to the LSM chip? > I mean, can be used averaged relative temperature of the housing heatsink, > with known gradient, of course? > Please recommend us measure method, even if we need personal temperature > sensor for each onboard LMS's. > > Best regards, > Andrey Sviyazov. > > > > 2012/7/28 Srdjan Milenkovic <s.milenkovic at limemicro.com> > >> Hi Alexander, >> >> I understand. It is the same with WCDMA and other FDD modulation >> standards, BTS can not stop transmitting/receiving. However, we can not >> expect temperature to change from -40 to +85 deg C without doing anything >> about it. >> >> LMS is quite robust regarding temperature change. For example, PLL will >> stay locked within +/-20 deg C from the tuning point. >> >> The graph below shows DC/LO leakage calibration stability vs temperature. >> Applications based on OFDM (LTE, WiMAX for example) do not need to wary >> about DC/LO leakage recalibration as DC OFDM carrier is not used. Other >> modulation schemes will have to take care of this. If we define the spec of >> -60dBc LO leakage, the graph below shows that LMS IC is OK within +/-10 deg >> C offset from the calibration point. >> >> BTW, you do not need UmTRXv3 at the moment. You can build a small board >> with temperature sensor alone and interface it back to BB/FPGA. >> >> Best regards, Srdjan >> >> >> >> >> >> ** ** >> >> **** >> On 28/07/2012 03:15, Alexander Chemeris wrote: >> >> Hi Srdjan, >> >> Thank you for the comment. >> >> Unfortunately, we can't perform regular re-calibration, because a GSM >> base station can't stop transmitting. This means we need a full blow >> temperature sensor and this is a bad news, as we have to create >> UmTRXv3 to add it. This is something you should definitely consider >> for your next-gen chip - an embedded temperature sensor. >> >> Do you know how sensitive those parameters are to a temperature? I.e. >> should we calibrate adjust them every centigrade or every five >> centigrade? >> >> On Fri, Jul 27, 2012 at 6:28 PM, Srdjan Milenkovic<s.milenkovic at limemicro.com> <s.milenkovic at limemicro.com> wrote: >> >> Hi Alexander, >> >> As I mentioned before, IQ phase error is quite stable over temperature in >> 900/1800MHz region so let us put it aside. This can be tuned and fixed in >> production. >> >> On the other hand, DC offset and LO leakage are temperature dependent as one >> would expect. However, they can be calibrated in the product as well not >> just in the lab. You need just to trigger built in DC cal blocks and >> optionally use RF loop back to further improve LO leakage. If you want to >> avoid temperature sensor you have an option to do these calibrations >> regularly, every 30min-1h for example. This should track the temperature >> change without having the sensor on board. >> >> Our other customers are using both approaches, with and without temperature >> sensor, depending on application and spec. If they have on board temperature >> sensor they are using it for multiple purpose such as monitoring BB, PA, >> etc. >> >> Best regards, Srdjan >> >> >> >> On 26/07/2012 16:48, Alexander Chemeris wrote: >> >> On Thu, Jul 26, 2012 at 4:37 PM, Alexander Chemeris<alexander.chemeris at gmail.com> <alexander.chemeris at gmail.com> wrote: >> >> On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovic<s.milenkovic at limemicro.com> <s.milenkovic at limemicro.com> wrote: >> >> Combining Thomas's idea of DC recalibration and, if necessary, making >> look >> up table for IQ phase error correction vs temperature should put us in >> good >> position to meet the specs. >> >> Well, AFAIK, LMS6002D doesn't have a temperature sensor built in and >> this means we have to install an external one, which again increase >> BoM cost. Is that's how this issue is solved by your other customers? >> I wonder is there a way to solve this without introducing a >> temperature compensation loop. >> >> Let me clarify - DC offset re-calibration is (more or less) fine in >> lab setup, but it's expensive to manufacture if we have to add >> temperature sensors and put every unit into a temperature camera for >> calibration. >> >> -- >> Regards, >> Alexander Chemeris. >> CEO, Fairwaves LLC / ООО УмРадиоhttp://fairwaves.ru >> >> >> > -- Robin Coxe | Close-Haul Communications, Inc. | Boston, MA +1-617-470-8825 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/umtrx/attachments/20120728/2bfbfafb/attachment.htm>