Changes between Version 9 and Version 10 of HardwareUsersGuides/WARPv3/RF


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Timestamp:
Sep 23, 2015, 12:05:11 PM (9 years ago)
Author:
murphpo
Comment:

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  • HardwareUsersGuides/WARPv3/RF

    v9 v10  
    134134
    135135The performance of the MAX2829 RF inputs are specified for input powers below approximately -10dBm. To connect two WARP v3 kits via a coax cable, ensure there is at lest 40dB series attenuation.
     136
     137----
     138
     139== Tx DCO Calibration ==
     140
     141Each analog Tx I/Q path on WARP v3 may have small DC offset. This is caused by normal variations in component values and inherent offsets in the analog and RF ICs. It is important this DC offset is removed to avoid carrier leakage (LO leakage) in transmitted RF waveforms.
     142
     143=== Applying Tx DCO Calibration ===
     144
     145Every node is calibrated during manufacturing, with the calibration values stored in the board's EEPROM. You should read and apply these calibration values in every custom design which uses the RF interfaces.
     146
     147The Tx DCO calibration values are stored at dedicated bytes in the EEPROM. See the [wiki:../../EEPROM EEPROM page] for details.
     148
     149The WARP v3 design uses auxiliary DACs in the AD9963 to apply small DC offsets to the differential I/Q DAC outputs. The auxiliary DACs are configured via SPI. The [wiki:/cores/w3_ad_controller w3_ad_controller] driver provides functions for writing the DAC values from user code.
     150
     151User designs should read Tx DCO calibration values from the EEPROM and update the AD9963 auxiliary DACs on every boot. The [wiki:/cores/radio_controller radio_controller] driver provides the function radio_controller_apply_TxDCO_calibration() implementing this process.
     152
     153=== Updating Tx DCO Calibration ===
     154You may wish to occasionally re-run the Tx DCO calibration process to account for drift in component values with temperature and age. We provide a pre-built FPGA design which implements the Tx DCO calibration process. To use the design:
     155
     156 1. Terminate the RF interface to be calibrated into a 50 ohm load. The SMA terminators included with the WARP v3 kit are good for this. Alternately you can connect the RF interface to a spectrum analyzer to observe the Tx DCO calibration results.
     157 1. Connect a micro USB cable to the USB-UART interface, and connect a terminal emulator to the virtual serial port with baud rate 57600bps
     158 1. Download [export:/Hardware/WARP_v3/Rev1.1/warpv3_txdco_calibration.zip warpv3_txdco_calibration.zip] and expand the archive
     159 1. Configure the WARP v3 node using {{{warpv3_txdco_calibration.bit}}} via JTAG or {{{warpv3_txdco_calibration.bin}}} with [wiki:howto/SD_Config an SD card].
     160 1. A menu will be printed to the UART; press 1 or 2 to calibrate RF A or RF B
     161 1. The calibration process is automatic and executes in ~20 seconds
     162 1. When complete, the new calibration values will be recorded to the EEPROM
     163 1. The RF interface will now transmit a pure sinusoid at 2460 MHz (8 MHz baseband tone, center frequency of 2452 MHz). You should observe a very low power tone at the 2452 MHz center frequency, resulting from any residual Tx DCO.
     164 1. You can use the keyboard to further adjust the Tx DCO, possibly improving on the auto-calibrated values. If you find values which show less energy at the center frequency, you can re-write the EEPROM by pressing {{{r}}}.
     165
     166Repeat this process for the other RF interface if desired. Always ensure the SMA connector of the active interface is terminated into a 50 ohm load (50 ohm terminator or other RF sink) before running the calibration routine.