Hi all,
Thomas has discovered that DC offset calibration for LMS is drifting a lot with temperature changes and this has detrimental effect on the modulation accuracy: http://code.google.com/p/umtrx/issues/detail?id=31
One solution proposed by Sylvain is to tune modulation a bit higher using digital modulation, which should be straightforward with UHD which has digital mixer in FPGA.
But I wonder what is a recommended solution for this temperature compensation for LMS in general. Srdjan, could you comment on this?
Hi,
We need a bit more info to see what we can do to avoid at least cooling fan as it is expensive.
1. Was that proper temperature chamber measurement or just Rx on/off?
2. I think we are talking about two issues called phase error here. 2.a IQ phase error caused by LMS Tx/Rx PLLs alone 2.b Modulation phase error
Item 2.a should not be affected by temperature so much In 900/1800MHz frequency region. If we want to get it even better we can always make a look up table vs temperature to correct IQ phase error from FPGA.
Item 2.b is affected by both 2.a and Tx DC cal. Tx DC cal has already been addressed by Thomas.
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.
Dr Srdjan Milenkovic On 26/07/2012 06:03, Alexander Chemeris wrote:
Hi all,
Thomas has discovered that DC offset calibration for LMS is drifting a lot with temperature changes and this has detrimental effect on the modulation accuracy: http://code.google.com/p/umtrx/issues/detail?id=31
One solution proposed by Sylvain is to tune modulation a bit higher using digital modulation, which should be straightforward with UHD which has digital mixer in FPGA.
But I wonder what is a recommended solution for this temperature compensation for LMS in general. Srdjan, could you comment on this?
On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovic s.milenkovic@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.
On Thu, Jul 26, 2012 at 4:37 PM, Alexander Chemeris alexander.chemeris@gmail.com wrote:
On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovic s.milenkovic@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 УмРадио http://fairwaves.ru
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
Dr Srdjan Milenkovic
On 26/07/2012 16:48, Alexander Chemeris wrote:
On Thu, Jul 26, 2012 at 4:37 PM, Alexander Chemeris alexander.chemeris@gmail.com wrote:
On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovic s.milenkovic@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 УмРадио http://fairwaves.ru
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@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@gmail.com wrote:
On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovic s.milenkovic@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 УмРадио http://fairwaves.ru
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
Dr Srdjan Milenkovic
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@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@gmail.com wrote:
On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovic s.milenkovic@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 УмРадио http://fairwaves.ru
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@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 Milenkovics.milenkovic@limemicro.com s.milenkovic@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 Chemerisalexander.chemeris@gmail.com alexander.chemeris@gmail.com wrote:
On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovics.milenkovic@limemicro.com s.milenkovic@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
It 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@gmail.comwrote:
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@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 Milenkovics.milenkovic@limemicro.com s.milenkovic@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 Chemerisalexander.chemeris@gmail.com alexander.chemeris@gmail.com wrote:
On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovics.milenkovic@limemicro.com s.milenkovic@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
Hi Robin.
Yes, I know this TI sensor and I've suggested to Alexander to include similar in the UmTRXv2 board instead of fan controller. Unfortunately, it was when we didn't known about calibration problems vs temperature. So, now we should implement temperature compensation control in HOST and FPGA, but till for external sensors like you suggest. Of course, sensors would be onboard in UmTRXv3 as Alexander mentiones.
Best regards, Andrey Sviyazov.
2012/7/28 Robin Coxe coxe@close-haul.com
It 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@gmail.comwrote:
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@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 Milenkovics.milenkovic@limemicro.com s.milenkovic@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 Chemerisalexander.chemeris@gmail.com alexander.chemeris@gmail.com wrote:
On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovics.milenkovic@limemicro.com s.milenkovic@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
BTW, due to ultra low active quiescent current of TMP102 we can reading and powering several sensors via FPGA io pins of debug connector.
Best regards, Andrey Sviyazov.
2012/7/28 Andrey Sviyazov andreysviyaz@gmail.com
Hi Robin.
Yes, I know this TI sensor and I've suggested to Alexander to include similar in the UmTRXv2 board instead of fan controller. Unfortunately, it was when we didn't known about calibration problems vs temperature. So, now we should implement temperature compensation control in HOST and FPGA, but till for external sensors like you suggest. Of course, sensors would be onboard in UmTRXv3 as Alexander mentiones.
Best regards, Andrey Sviyazov.
2012/7/28 Robin Coxe coxe@close-haul.com
It 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@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@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 Milenkovics.milenkovic@limemicro.com s.milenkovic@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 Chemerisalexander.chemeris@gmail.com alexander.chemeris@gmail.com wrote:
On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovics.milenkovic@limemicro.com s.milenkovic@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
-
Alexander Chemeris -
Andrey Sviyazov -
Robin Coxe -
Srdjan Milenkovic