EVAL BGT24LTR11 BOARD FMCW mode

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User11520
Level 2
Level 2
10 replies posted 10 questions asked 5 replies posted
Hello,
I am working with the EVAL BGT24LTR11 BOARD. It works fine in Doppler mode but I am noticing some problems when configured to FMCW mode.
I applied a sawtooth signal at the Vtune pin with a period of 1 ms and an amplitude from 1.3 V to 1.7 V in order to have 200-250 MHz of bandwidth. I have made different tests both connecting antennas to the TX and RX pins or connecting together the TX and RX pins by means of a cable and an attenuator in order to exclude possible problems caused by the antennas.
At IF, using I see different peaks with a spacing of 1 KHz. I am getting a bit confused because I worked in a similar way with the BGTMTR11 chip but I had not the same issues.
The peaks in my opinion are due to some crosstalk from the sawtooth signal but anyway I don't know how to solve.
Someone succesfully used this evaluation board in FMCW mode?
Thanks in advance
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4 Replies
User14352
Level 1
Level 1
5 replies posted First reply posted First question asked
Hi emacar:

Do you mean you are using Spectrum Analyzer and see peaks with 1KHz spacing? Try using an oscilloscope, you may see the sawtooth signal you applied at the vtune pin.
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User11520
Level 2
Level 2
10 replies posted 10 questions asked 5 replies posted
Hi,
Thanks for the suggestion.
But why am I not able to see the signal spectrum? For calculating the target distance I need to calculate the frequency peak in the spectrum as for the BGT24MTR11 chip.
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User14352
Level 1
Level 1
5 replies posted First reply posted First question asked
emacar wrote:
Hi,
Thanks for the suggestion.
But why am I not able to see the signal spectrum? For calculating the target distance I need to calculate the frequency peak in the spectrum as for the BGT24MTR11 chip.


The IF output is too small compared to the sawtooth leakage signal, it should be amplified by several dozens dB,
and the amplifier should also be a high pass filter, in order to attenuate the sawtooth leakage and the strong echos of near obstacles.
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User11520
Level 2
Level 2
10 replies posted 10 questions asked 5 replies posted
My purpose was to detect near targets from 0 to 5 m. I was able to do this with BGTMTR11 but I am understanding that this is not possible with the BGT24LTR11 board. Maybe the sawtooth leakage echoes are to strong for short distances, do you agree with this?
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