高通RF-Calibration-介绍课件.ppt

1、 What is RF calibration.Why calibration.NV items of RF calibration.Rx Calibration.Tx Calibration.RF calibration is the process of measuring data to be used in theRF calibration is the process of measuring data to be used in thesystem for the purpose of compensation of non-linearsystem for the purpos

2、e of compensation of non-linearcharacteristics and frequency variations,and to provide absolutecharacteristics and frequency variations,and to provide absolutepower reference and temperature compensation to ensurepower reference and temperature compensation to ensureperformance of the Tx and Rx path

3、s of a subscriber unit.performance of the Tx and Rx paths of a subscriber unit.Output from the calibration process is stored in non-volatile(NV)Output from the calibration process is stored in non-volatile(NV)memory items in AMSS.memory items in AMSS.AMSS uses calibration values during normal operat

4、ion to ensureAMSS uses calibration values during normal operation to ensuresystem performance is met.system performance is met.Setup:Subscriber units have differing RF characteristics Differences in design Part-to-part variations of components of the same design Individual phones also change their o

5、wn RF characteristics:over frequency channel over temperaturel The subscriber unit must estimate the Rx power properly to The subscriber unit must estimate the Rx power properly tomaximize signal-to-noise ratios and to provide a basis for Txmaximize signal-to-noise ratios and to provide a basis for

6、Txpower output.power output.l The subscriber unit must transmit at correct Tx power level over The subscriber unit must transmit at correct Tx power level overits large dynamic range.its large dynamic range.l The Mobile Station Modem(MSM)device and system software The Mobile Station Modem(MSM)device

7、 and system softwarecombination must know the RF and analog characteristics of thecombination must know the RF and analog characteristics of theparticular unit.particular unit.l Failure to compensate for differing RF/analog characteristics may Failure to compensate for differing RF/analog characteri

8、stics maycause the unit to fail minimum performance specificationscause the unit to fail minimum performance specifications The compensation values are classified:Static RF NV items:Measured once per design.Calculated RF NV items:RF NV items that are calculated based on other parameters of the desig

9、n configurations.Measured RF NV items:Is determined by the RF calibration process.NV items of RF calibration Rx calibration Philosophy of Rx AGC(Automatic Gain control)loop.DVGA(Digital VGA)offset calibration.LNA(Low Noise Amplifier)offset calibration.Rx calibration(Rx AGC loop)Each Rx chain has its

10、 own receiver.Receiver calibration primarily consists of measuring the DVGA offsetDVGA offset(also called VGA gain offset)and multiple LNA offsetsLNA offsets,all at each chosen frequency index.Software loads the frequency-compensated DVGA and LNA offset values into the hardware registers shown above

11、.Philosophy of Rx DVGA offset calibration:Rx calibration(DVGA offset)Rx calibration(LNA offset)Philosophy of Rx LNA offset calibration:Rx calibration(LNA offset)Tx calibration Philosophy of Tx AGC(Automatic Gain control)loop.Tx Linearizer Tx Compensation HDET(High power detector)Tx calibration(AGC L

12、oop)The transmitter AGC must adjust the Tx power level based on the RSSI,access probe parameters,closed-loop power-control bits(PCBs),and channel-configuration attributes.Tx calibration(AGC Loop)Tx calibration(Tx AGC Characteristic)Tx calibration(Tx Linearizer)Tx calibration(TX_GAIN_CTRL.)Tx calibra

13、tion(HDET Feedback loop op.)Tx compensation(1/3):NV_BCy_TX_COMP0_I NV_BCy_TX_COMP3_I NV_BCy_TX_COMP0_I=CDMA_TX_COMP_VS_FREQ15:0+CDMA_TX_LIN_VS_TEMP7:0+CDMA_TX_SLP_VS_TEMP7:0Tx calibration(Tx Comp.)CDMA_TX_LIN_VS_TEMP7:0:-Used to shift the effective Tx-linearizer curve by a constant for temperature-b

14、ased gain changes.For example:Given temperature index,the elementin this table is 0 x05,each of the 36 offsets in the adjusted master curve table will be increased by five,when the temperature corresponds to that given index.CDMA_TX_SLP_VS_TEMP7:0 -Used to shift the effective Tx-linearizer curve by

15、a graduated amount for temperature-based gain changes.Ps.typically all zeros unless extra precision is desired.Tx calibration(Tx Comp.)High-power detector(HDET)(1/5):1.Output at the power level defined by TX_GAIN_CTL.2.The HDET circuit measures the output power.3.The HDET value is sampled.4.Table th

16、at maps the HDET value to Tx power level.The HDETs estimated power level is compared to TX_GAIN_CTL to determine an error value.TX_GAIN_LIMIT is adjusted by that error value.Note:Only the maximum powerlimitis affected by the HDET circuit.Tx calibration(Tx HDET)HDET(2/5):NV_BCy_TX_LIM_VS_FREQ_I:The A

17、DC readings of the HDET circuit may have some frequencydependencies,this NV item can be used to compensate for such dependenciesTx calibration(Tx HDET)HDET(4/5):NV_BCy_EXP_HDET_VS_AGC_I:AMSS uses this NV item to build a lookup table,which indexes Tx power estimation via a scaledTX_GAIN_CTL(represent

18、ing the desired Tx power),to the associated HDET circuit values atreference temperature and the reference frequency.Procedure:1.Break up the upper 1/4 of TX_GAIN_CTL into 16 segments.2.Vary the desired Tx power by manipulating the TX_AGC_ADJ PDM.3.Read the value of the HDET circuit over each of the 16 segments and store the results in NV_BCy_EXP_HDET_VS_AGC15:0.4.Commit NV:Ex:TX_GAIN_CTL has a 102.4 dB range from 60.4 to 42 dBm:Then Tx_Lim_vs_Freq_Pwr_Level0=16.4Tx_Lim_vs_Freq_Pwr_Level1=18.0Tx_Lim_vs_Freq_Pwr_Level2=19.6Tx_Lim_vs_Freq_Pwr_Level15=40.4Tx calibration(Tx HDET)