AWR2243: Spurious Signals

radar_pete

Part Number: AWR2243
Other Parts Discussed in Thread: AWR1843BOOST

Tool/software:

Hi,

We are using 4 x cascaded AWR2243 radar chips in a radar system and are currently going through compliance testing. The test house have observed an issue with spurious signals being generated at around 60-62 GHz and at frequencies above the chirp bandwidth - with settings in attached mmwaveconfig file we should have chirp bandwidth from 77.4-80.63 GHz but you can see that chirp bandwidth is from 77.4-83.27 GHz. Can you see anything in our chirp settings that could account for this?

Best regards,

Peter.

Fullscreen mmwaveconfig_mode_01.txt Download

#
#For detailed view of mmWave Radar configuration structure
#please refer
#ti\control\mmwavelink\docs\doxygen\html\index.html
#

# Chirp config (tx_enable) is different for master and each slave
# cascading=1 for master and cascading=2 for slaves

# UPDATED for 4-chip cascade configuration
#
#
#
# Chip vs Chirp enable
#                CHIRP   0 1 2 3  4 5 6 7  8 9 10 11
# Master ID0 txEnable = {0,0,0,4, 0,0,0,0, 2,1,0,0}
# Slave1 ID1 txEnable = {0,0,0,0, 0,4,2,1, 0,0,0,0}
# Slave2 ID2 txEnable = {0,0,0,0, 1,0,0,0, 0,0,4,2}
# Slave3 ID3 txEnable = {4,2,1,0, 0,0,0,0, 0,0,0,0}

#
#Global configuration
#Advanced frame test enable/disable; 1 - Advanced frame; 0 - Legacy frame
#Continuous mode test enable/disable; 1 - Enable; 0 - Disable
#Dynamic chirp test enable/disable; 1 - Enable; 0 - Disable; This should not be enabled if Advanced chirp test is enabled
#Dynamic profile test enable/disable; 1 - Enable; 0 - Disable
#Advanced chirp test enable/disable; 1 - Enable; 0 - Disable; The legacy chirp API is not required if this is enabled
#Firmware download enable/disable; 1 - Enable; 0 - Disable
#Flash present/absent; 1 - Present; 0 - Absent
#Calibration enable/disable; To perform calibration store/restore; 1 - Enable; 0 - Disable
#Calibration Store/Restore; If CalibEnable = 1, then whether to store/restore; 1 - Store; 0 - Restore
#Cascade device map; 1 - Master ; 2 - Slave1 ; 4 - Slave2 ; 8 - Slave3
#Transport mode; 1 - I2C; 0 - SPI
#
LinkAdvanceFrameTest=0;
LinkContModeTest=0;
LinkDynChirpTest=0;
LinkDynProfileTest=0;
LinkAdvChirpTest=0;
EnableFwDownload=0;
EnableMmwlLogging=0;
CalibEnable=0;
CalibStoreRestore=1;
CascadeDeviceMap=15;
TransferMode=0;
IsFlashConnected=1;
#END

#
#power on master arguments, please modify if needed.
#rlClientCbs_t: crcType 0:16Bit/1:32Bit/2:64Bit, ackTimeout
#
crcType=1;
ackTimeout=1000;
#END

#
#channel config parameters, please modify if needed.
#rlChanCfg_t
# Note: cascading manually set when using 4x config files
channelTx=7;
channelRx=15;
cascading=0;
#END

#
#ADC out config parameters, please modify if needed.
#rlAdcOutCfg_t
#
adcBits=2;
adcFormat=1;
#END

#
#DATA format config parameters, please modify if needed.
#rlDevDataFmtCfg_t
#
rxChanEn=15;
adcBitsD=2;
adcFmt=1;
iqSwapSel=0;
chInterleave=0;
#END

#
#Low power config Paramters, please modify if needed.
#rlLowPowerModeCfg_t
#
anaCfg=0;
lpAdcMode=0;
#END

#
#Data Path config parameters, please modify if needed
#rlDevDataPathCfg_t
#
intfSel=0;
transferFmtPkt0=1;
transferFmtPkt1=0;
cqConfig=0;
cq0TransSize=0;
cq1TransSize=0;
cq2TransSize=0;
#END

#
#LVDS clock config parameters, please modify if needed
#rlDevDataPathClkCfg_t
#
laneClk=1;
# 600Mbps / HSI clock = 9
dataRate=1;
# 300Mbps / HSI clock = 10
# dataRate=4;
#END

#
#SET HSI clock parameters, please modify if needed.
#rlDevHsiClk_t
#
# 1200MHz, data rate = 1
hsiClk=9;
# 600Mhz, data rate = 4
#hsiClk=10;
#END

#
#LANE config parameters, please modify if needed.
#rlDevLaneEnable_t
#
laneEn=3;
#END

#
#LVDS Lane Config parameters, please modify if needed.
#rlDevLvdsLaneCfg_t
#
laneFmtMap=0;
laneParamCfg=1;
#END

#
#CSI2 Lane Config parameters, please modify if needed.
#rlDevCsi2Cfg_t
#
lanePosPolSel=196641;
#END

#
#Programmable Filter config parameters, please modify if needed.
#rlRfProgFiltConf_t
#
profileId=0;
coeffStartIdx=0;
progFiltLen=14;
progFiltFreqShift=100;
#END

#
#Profile config parameters, please modify if needed.
#rlProfileCfg_t
#
profileId=0;
pfVcoSelect=2;
startFreqConst=1442845425;
idleTimeConst=3850;
adcStartTimeConst=550;
rampEndTime=8390;
txOutPowerBackoffCode=0;
txPhaseShifter=0;
freqSlopeConst=798;
txStartTime=0;
numAdcSamples=1024;
digOutSampleRate=13120;
hpfCornerFreq1=0;
hpfCornerFreq2=0;
rxGain=176;
#END

#
#Frame configuration parameters, please modify if needed.
#rlFrameCfg_t
# Set frameCount to 0 for infinite frames
chirpStartIdxFCF=0;
chirpEndIdxFCF=11;
#chirpEndIdxFCF=1;
frameCount=0;
loopCount=32;
periodicity=10000000;
triggerDelay=0;
numAdcSamples= 2048;
triggerSelect=1;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=0;
chirpEndIdx=0;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=0;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=1;
chirpEndIdx=1;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=0;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=2;
chirpEndIdx=2;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=0;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=3;
chirpEndIdx=3;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=4;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=4;
chirpEndIdx=4;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=0;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=5;
chirpEndIdx=5;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=0;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=6;
chirpEndIdx=6;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=0;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=7;
chirpEndIdx=7;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=0;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=8;
chirpEndIdx=8;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=2;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=9;
chirpEndIdx=9;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=1;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=10;
chirpEndIdx=10;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=0;
#END

#
#Chirp Configuration parameters, please modify if needed.
#rlChirpCfg_t
#
chirpStartIdx=11;
chirpEndIdx=11;
profileIdCPCFG=0;
startFreqVar=0;
freqSlopeVar=0;
idleTimeVar=0;
adcStartTimeVar=0;
txEnable=0;
#END

over 1 year ago

0 aozer over 1 year ago

TI__Mastermind 30715 points

Hello,

There are two possibilities.

1. This is distortion caused by non-linearity of external mixer. If the test house is using an external mixer the test house should be able to debug this and understand the cause.

2. This is a harmonic of the LO signal. The LO is operating at your RF frequency / 4 (i.e. 20GHz at 80GHz RF) so this would roughly be the third harmonic of the LO. Based on the programmed frequency (77.4 - 80.63 GHz) we would expect the third harmonic of LO to be at 58.05 - 60.4725 GHz, so to me this does not seem like it is caused by the LO. It most likely is due to item #1.

Regards,

Adrian

0 radar_pete over 1 year ago in reply to aozer

Intellectual 400 points

Thanks for coming back so quickly on that Adrian, we have queried this with the test house, hopefully is down to their measurement setup as you say.

0 radar_pete over 1 year ago in reply to radar_pete

Intellectual 400 points

Hi,

We've been back and forward with the test house several times on this - they said that 'the test lab used an external mixer before the spectrum analyzer, however, the test equipment including the external mixer was calculated before performing the tests, and using an external mixer is common for mm wave transmitter measurements.' They also provided a spectrum analyser plot from a measurement on another radar operating at 76-77 GHz, which didn't have the spurious signals at 60 GHz or > 81 GHz. Can you think of any other possible cause of these spurious signals to be appearing? We could send our schematic/layout if that would help.

0 aozer over 1 year ago in reply to radar_pete

TI__Mastermind 30715 points

Hello,

No, it is almost certainly due to the mixer or pre-amp if they are using one. There is no clock operating inside the radar that would generate a harmonic at the frequencies you are seeing so it does not make sense that the radar would cause this. The synthesizer is operating at your chirp frequency divided by 4 so if the harmonics of this do not line up with the emissions you are seeing then it is not from the radar, especially with the wideband emissions you are seeing.

We have EU RED reports for AWR1843BOOST which uses same front end as AWR2243. If this was a known behavior, we would have seen it before. We have had same discussion on this issue with other customers and it always ends up being an issue with the mixer or setup.

If they put an attenuator at the input of the source of the non-linearity (pre-amp or mixer) they should see that the distortion amplitude decreases by order of magnitude more than the fundamental. i.e. if a 10dB attenuator is used the radar frequency and harmonics will decrease by 10dB and the non-linearities will decrease by significantly more. If they see this behavior it will confirm that the noise they are seeing is due to non-linearity and not from the radar.

/cfs-file/__key/communityserver-discussions-components-files/1023/12554995_2D00_E2V2-EN-302-264-v2.1.1-AWR1843-Series-Final-Report.pdf

/cfs-file/__key/communityserver-discussions-components-files/1023/12554995_2D00_E1V2-EN-301-091-AWR1843-Series-Final-Report.pdf

Regards,

Adrian

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AWR2243: Spurious Signals