高通RF Calibration 介绍PPT

1、RF Calibration Introduction,1,Agenda,What is RF calibration. Why calibration. NV items of RF calibration. Rx Calibration. Tx Calibration.,2,What is RF calibration, RF calibration is the process of measuring data to be used in the system for the purpose of compensation of non-linear characteristics a

2、nd frequency variations, and to provide absolute power reference and temperature compensation to ensure performance of the Tx and Rx paths of a subscriber unit. Output from the calibration process is stored in non-volatile (NV) memory items in AMSS. AMSS uses calibration values during normal operati

3、on to ensure system performance is met.,3,Setup:,What is RF calibration,4,Why calibration,Subscriber units have differing RF characteristics Differences in design Part-to-part variations of components of the same design,5,Individual phones also change their own RF characteristics: over frequency cha

4、nnel over temperature,Why calibration,6,Why calibration,The subscriber unit must estimate the Rx power properly to maximize signal-to-noise ratios and to provide a basis for Tx power output. The subscriber unit must transmit at correct Tx power level over its large dynamic range. The Mobile Station

5、Modem (MSM) device and system software combination must know the RF and analog characteristics of the particular unit. Failure to compensate for differing RF/analog characteristics may cause the unit to fail minimum performance specifications,7,The compensation values are classified: Static RF NV it

6、ems: Measured once per design. Calculated RF NV items: RF NV items that are calculated based on other parameters of the design configurations. Measured RF NV items: Is determined by the RF calibration process.,NV items of RF calibration,8,Rx calibration Philosophy of Rx AGC(Automatic Gain control) l

7、oop. DVGA(Digital VGA) offset calibration. LNA(Low Noise Amplifier) offset calibration.,9,Rx calibration (Rx AGC loop),Each Rx chain has its own receiver. Receiver calibration primarily consists of measuring the DVGA offset(also called VGA gain offset) and multiple LNA offsets, all at each chosen fr

8、equency index. Software loads the frequency-compensated DVGA and LNA offset values into the hardware registers shown above.,10,Philosophy of Rx DVGA offset calibration:,Rx calibration (DVGA offset),11,Rx calibration (LNA offset),Philosophy of Rx LNA offset calibration:,12,Rx calibration (LNA offset)

9、,13,Tx calibration Philosophy of Tx AGC(Automatic Gain control) loop. Tx Linearizer Tx Compensation HDET (High power detector),14,Tx calibration (AGC Loop),The transmitter AGC must adjust the Tx power level based on the RSSI, access probe parameters, closed-loop power-control bits (PCBs), and channe

10、l-configuration attributes.,15,Tx calibration (AGC Loop),16,Tx calibration (Tx AGC Characteristic),17,Tx calibration (Tx Linearizer),18,Tx calibration (TX_GAIN_CTRL.),19,Tx calibration (HDET Feedback loop op.),20,Tx compensation(1/3):,NV_BCy_TX_COMP0_I NV_BCy_TX_COMP3_I NV_BCy_TX_COMP0_I = CDMA_TX_C

11、OMP_VS_FREQ15:0+ CDMA_TX_LIN_VS_TEMP7:0 + CDMA_TX_SLP_VS_TEMP7:0,Tx calibration (Tx Comp.),21,CDMA_TX_LIN_VS_TEMP7:0 : - Used to shift the effective Tx-linearizer curve by a constant for temperature-based gain changes. For example: Given temperature index, the element in this table is 0 x05, each of

12、 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 a graduated amount for temperature-based gain changes. Ps. typically all zeros unless extra

13、precision is desired.,Tx calibration (Tx Comp.),22,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 that maps the HDET value to Tx power level. The HDETs estimated power level is c

14、ompared 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),23,HDET (2/5):,NV_BCy_TX_LIM_VS_FREQ_I: The ADC readings of the HDET circuit may have some frequency dependenc

15、ies, this NV item can be used to compensate for such dependencies,Tx calibration (Tx HDET),24,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 scaled TX_GAIN_CTL (representing the desired Tx power), to the associated HDET circuit values at reference temperature and the reference frequency.,Procedure:,Break up the upper 1/4 of TX_GAIN_CTL into 16 segments. Vary the desired Tx power by manipulating the TX_AGC_ADJ PDM. Read the value of the HDET circuit over each of the 16 segments and store the results in NV_BCy_