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1、1RFIC/IMS 2008 WSB-3 Arya BehzadRFIC/IMS 2008 WSB-3 Arya Behzad WSL - 3 Calibration Techniques for Wireless SoCs Arya Behzad Broadcom Corporation San Diego, CA 2RFIC/IMS 2008 WSL-3 Arya Behzad Outline Why Calibrate? Calibration Techniques Resistor Calibration RC Time Constant Calibration VCO Calibra
2、tion Automatic Frequency Control (Agile Frequency Offset Calibration) Quadrature Error and LO Feedthrough Calibration LO Generation Amplitude Control System and Calibration Other Calibrations Process Sensing and Calibration Temperature Sensing and Calibration Power Detector Calibration 3RFIC/IMS 200
3、8 WSL-3 Arya Behzad Calibrations Frequency Offset: 200kHz Start: -26 carrier index Stop: +26 carrier A: Ch1 Spectrum 60% LinMag 6%/div 0% Span = 36MHz A: Ch1 OFDM Err Vect Spectrum AFC DisabledAFC Enabled 60% LinMag 6%/div 0% Span = 36MHz A: Ch1 OFDM Err Vect Spectrum A: Ch1 Spectrum Start: -26 carr
4、ier index Stop: +26 carrier MMAFC Performance 43RFIC/IMS 2008 WSL-3 Arya Behzad AFC DisabledAFC Enabled RX EVM: -24.3dB RX EVM: -28.4dB Rx EVM Improved by 4.1dB A: Ch1 OFDM MeasA: Ch1 OFDM Meas MMAFC Performance 44RFIC/IMS 2008 WSL-3 Arya Behzad VCO Calibration Coverage over a wide frequency range i
5、s required for many standards One way to achieve this is to design a VCO with a high gain factor (Kvco) The problem with a high gain VCO is the sensitivity of the VCO to noise on the control line and the supplies, and hence often a poor phase noise An alternate method to achieve a wide tuning range
6、while maintaining a low Kvco is to use banks of switch capacitors in the VCO The switch capacitor setting sets the VCO to a frequency that is “close enough” and then the varactor is used in conjunction with the PLL to set the exact frequency Due to process, temperature and supply variations, it is n
7、ot sufficient to set the switch capacitor banks for a required channel based on a a-priori programmed lookup table It is essential to use an auto-calibration loop to ensure proper operation over PVT and to ensure the operation of the charge pump over a compliant voltage range The auto-calibration ca
8、n be done wit the PLL in open-loop mode, closed-loop mode, or a combination of the two Tradeoffs of calibration accuracy against calibration time need to be accounted for 45RFIC/IMS 2008 WSL-3 Arya Behzad 0.40.50.60.70.80.911.11.21.31.4 5100 5400 VCO Control Voltage V VCO Output Frequency MHz VCO Tu
9、ning Curves VCO switch capacitor tuning curves covering the lower U.S. 802.11a band. The calibration algorithm selects the optimal curve such that the VCO can operate at a voltage around the middle of the charge pump compliance range. 46RFIC/IMS 2008 WSL-3 Arya Behzad Compact -41dB 2.484GHz) TX Cons
10、tellation (Po=-5dBm; EVM= -40dB 5.24GHz) Ref: A. Behzad, et al, ISSCC 2007, JSSC 2007 53RFIC/IMS 2008 WSL-3 Arya Behzad Conclusion We have only touched upon a few calibration techniques that are utilized today to achieve transceivers with outstanding performance, low cost, and high yield Many, many
11、additional calibrations are possible and being applied to various transceivers Transmit power calibrations Temperature sensor based calibrations Power amplifier linearizations and calibrations LINC Amplifier based calibrations Receiver IP3 and IP2 based calibrations Polar transmitter one-point and two-point based calibrations SWC/MRC based calibrations Beam-former based calibrations Pipeline ADC digital background calibrations
