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Hi,
we have tested some new IWR1642 BOOST radars with the out of the box demo
using the mmWave Demo Visualizer, working with the demo bin file of SDK 1.1.0.2
We have seen a strange phenomena with some of the radars where the main lobe is directed
upwards at ~20 [degrees] (tilted upwards in elevation).
We suspect that there is some kind of antenna calibration procedure that should have been performed and
haven't.
We work in a mode of 2 Tx and 4 Rx. The configuration is attached.
We did 6 experiments:
1. Mounting a corner reflector of RCS = 1.5 [m^2] in a distance of 1.3 [m] and angle 0 ("Nominal Mode") - the visualizer did not detect the corner reflector.
2. We then tilted the radar at -20 [deg] in elevation - the reflector was detected with very high peak.
3. We tilted the radar back to elevation angle = 0 but this time mounted the corner reflector at the height of 45 [cm] above the radar - the corner is detected with high peak.
4. Working in a mode of 1 Tx and 1 Rx in "Nominal Mode"- the corner is detected.
5. Working in a mode of 1 Tx and 2 Rx in "Nominal Mode"- the corner is detected.
6. Working in a mode of 1 Tx and 4 Rx in "Nominal Mode"- the corner is sometimes detected and sometimes not.
We want to emphasize that we have purchased a few IWR1642 in the past and haven't seen such a phenomena.
Do you know what is the reason of such phenomena?
We also tried to use the option of "compRangeBiasAndRxChanPhase" but it didn't help.
We will be glad for some help with this issue.
Thanks,
Boaz
The configuration:
sensorStop
flushCfg
dfeDataOutputMode 1
channelCfg 15 3 0
adcCfg 2 1
adcbufCfg -1 0 0 1 0
profileCfg 0 77 69 7 28.55 0 0 50 1 128 6250 0 0 30
chirpCfg 0 0 0 0 0 0 0 1
chirpCfg 1 1 0 0 0 0 0 2
frameCfg 0 1 128 0 100 1 0
guiMonitor -1 1 1 0 0 0 1
cfarCfg -1 0 0 8 4 4 0 3000
cfarCfg -1 1 0 8 4 4 0 3000
peakGrouping -1 1 0 0 1 127
multiObjBeamForming -1 1 0.5
clutterRemoval -1 0
calibDcRangeSig -1 1 -5 4 256
extendedMaxVelocity -1 0
compRangeBiasAndRxChanPhase 0.0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0
measureRangeBiasAndRxChanPhase 0 1.26 0.3
sensorStart
Hello,
We have asked the antenna designer. The antenna azimuth boresight is based on the frequency of the chirp. In the range of 78.5Ghz center frequency, the azimuth boresight is estimated at 5 degrees. At 81Ghz the elevation boresight is ~17 degrees.
It is also possible that from old to new IWr1642 EVMs, that there is some tolerance difference between the L1 antenna pad structure, and the L2 ground structure.
If you look at swru521a, the Antenna figure for elevation shows 0 degree. The Antenna designer has output these two graphs at 78.5Ghz 5-7degree elevation, 81Ghz 15-17 degree elevation.
a) suggest you rerun your test with mmWave SDK 1.0 - to check if its a software concern
b) if you have an old EVM, run with mmWave SDK 1.1 - this would also check hardware/ software (I only have a 6mo old version)
c) change the Chirp so that you can isolate the frequency band (see if starting at 77 vs 79 shows a different behavior
profileCfg - startfreq 77Ghz
Freqslope - 28.55
ramp_end_time - 50
endfreq = startfreq + (Freqslope * ramp_end_time)
freqcenter = avg(startfreq, endfreq) 77.7 Ghz
d) please send us the board serial numbers, we will see if we can find one in this block. So we can test it.
Note: in the newest antenna graph the antenna has a higher sensitivity at 15-17 degrees, but at higher frequency ~80Ghz.
Regards,
Joe Quintal
Hi Joe,
I have placed a corner reflector in a distance of 1 [m] from the radar at
the same height and then rotated the radar in the elevation angle phi, and
documented the received power in dB as shown in the "mmWave Demo Visualizer".
This is the results I get:
As you can see, we lose around 20 [dB] when mounting the radar at phi=0 because of this radiation pattern.
Can you explain this?
Is it normal?
Thanks,
Boaz
Hello,
If you use Radar Studio which can be downloaded from the Ti website, and you have the Devpack board, You can use the sample configuration attached, and add one set of manual operations, (RegOps tab) to write a debug value, @0x4320140C, read, modify bits 16.19 with 0x7. This will activate the 40Mhz crystal clock to the J2 connector, should be 1v amplitude, 40Mhz with 50 ppm. This can be used to validate the 40Mhz clock.
we have evaluated a returned EVM with the test procedure described in AntennaMeasurementCompare.xlsx, we are working on the cause of the problem.
Hi Joe,
After following the instructions above I don't see any signal coming out to the J2 connector.
I do see the 40 MHz sine wave when I connect directly to the oscillator.
Boaz
