AnsweredAssumed Answered

different spectrum for each run

Question asked by jchenak on Apr 23, 2018
Latest reply on Apr 23, 2018 by Vinod


I am using a custom board FMCOMMS3 with Zynq board to design a FM project. My baseband modulated data is generated by a self-design IP core and sent to AD9361 up-conversion. When I observe the spectrum after tx channel on analyser, I found that the result is different for each run (the program is completely same). Sometimes the spectrum is not symmetric that makes my very confused. Can anybody helps to explain what reasons may cause this problem?


I use the FDD mode and add a command to set FDD mode in the end of TX Quad Calibration. 


SPIRead 0A3 // Masked Read:  Read lower 6 bits, overwrite [7:6] below
SPIWrite 0A0,15 // Set TxQuadcal NCO frequency
SPIWrite 0A3,00 // Set TxQuadcal NCO frequency (Only update bits [7:6])
SPIWrite 0A1,7B // Tx Quad Cal Configuration, Phase and Gain Cal Enable
SPIWrite 0A9,FF // Set Tx Quad Cal Count
SPIWrite 0A2,7F // Set Tx Quad Cal Kexp
SPIWrite 0A5,01 // Set Tx Quad Cal Magnitude Threshhold
SPIWrite 0A6,01 // Set Tx Quad Cal Magnitude Threshhold
SPIWrite 0AA,25 // Set Tx Quad Cal Gain Table index
SPIWrite 0A4,F0 // Set Tx Quad Cal Settle Count
SPIWrite 0AE,00 // Set Tx Quad Cal LPF Gain index incase Split table mode used
SPIWrite 169,C0 // Disable Rx Quadrature Calibration before Running Tx Quadrature Calibration
SPIWrite 016,10 // Start Tx Quad cal
WAIT_CALDONE TXQUAD,2000 // Wait for cal to complete (Done when 0x016[4]==0)
SPIWrite 16A,75 // Set Kexp Phase
SPIWrite 16B,95 // Set Kexp Amplitude & Prevent Positive Gain Bit
SPIWrite 169,CF // Enable Rx Quadrature Calibration Tracking
SPIWrite 18B,AD // Enable BB and RF DC Tracking Calibrations
SPIWrite 012,10 // Cals done, Set PPORT Config
SPIWrite 013,01 // Set ENSM FDD/TDD bit
SPIWrite 015,0C // Set Dual Synth Mode, FDD External Control bits properly

SpiWrite 014,23 ;  //Set FDD mode, add by myself


The first run of program. 

The second run, not symmetric.