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Blind spot monitoring unit teardown!

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Hello guys!
I just wanted to share my teardown of a defective Blind spot monitoring unit! This unit was installed on Mazda CX-9 2011.
I want to know more information about how the system works and any useful information about it!
Thanks in advance

The third pic looks like a second board.  What's on its other side?  The side you show sure looks like phase array radar transmit and receive antennas.  The three round cross shaped soldered objects are MMIC amplifiers.  There - I have exhausted my knowledge of what I see here - others who deal with this stuff every day surely can add more detail.

I attached the bottom picture of the antenna!

It has three receiving antennas (with three MMICs or microwave FET amplifiers). Gate pin of each amplifier is biased using thin feeding line with two radial stubs and a resistor. Antennas RX1/RX2 are for azimuth (horizontal) angle sensing when TX-A is transmitting . Antenna RX3 is most likely only for long range distance sensing when TX-B is transmitting. Theoretically, RX3 can be used together with RX1 or RX2 to measure elevation (vertical) angle. Probably not doing any elevation angle measurements here. Transmitting antenna TX-B is narrow-beam high-gain for long-range distance measurement mode (when RX3 is receiving). In this mode, it work as simple fsk/fmcw radar with single TX / single RX  antenna. Transmitting antenna TX-A is wide-beam low-gain for short-range distance AND angle measurements (when RX1 and RX2 are receiving). Angle measurement is usually done using phase monopulse method (unambiguous angle measurement range depends on antenna center spacing d1/d2) In some older designs, the same MMIC/FET is used as active device for oscillator (under shield on the back side). In my design I also used FET as resistive mixer, but it is kind if rare. More interesting stuff may be under the shield on the back of the antenna.

DSP/control board contains bunch of operational amplifiers. Depending on MCU/ADC performance and modulation type, there are few options how it can be made. Microwave module has inputs and outputs: power, vco control, some other control inputs. Outputs: signals from each antenna's receiving mixer. Those outputs are fed to operational amplifiers, and then amplified and filtered (low pass+high pass) signal goes to multi-channel ADC. MCU prepares digitized data from each channel to go through FFT algorithm. E.g., if it's FSK radar, MCU can control VCO using GPIO or DAC. This process is synchronized with ADC reception, so for TWO fsk frequencies we can extract TWO signals from ONE antenna. Using signal from single antenna is already enough to measure distance (e.g. digitized 2048 samples, made two 1024 arrays A1 A2, performed FFT1 FFT2, found peak value at element N, calculated phase difference between FFT1 and FFT2 at element N. Used formula to convert N to Hz (Doppler) and then to speed (km/h). Used another formula to convert phase difference FFT1[N]-FFT2[N] to distance). Perform the same for second antenna (FFT3 and FFT4). It will provide the same speed and distance, and also target angle can be extracted using FFT phase of adjacent antennas FFT[1]-FFT[3] or FFT[2]-FFT[4]. E.g., on STM32H7 I have 8 channel FFT extraction of all peaks and angles for my "Radar for the blind and the deaf project", with sampling time offset compensation, sliding window and other for best performance. On STM32F1, it is possible to process radar signals like on your photo, but ADC may be a limitation on F1, but can be solved using analog sample-and-hold circuit (opamp + spdt + 2 X capacitors + 2 X opamps). This circuit will extract two copies of 1024 data points for FSK f1 and f2 carrier frequencies analog way. It doubles number of required ADC channels but lowers sampling rate frequency down to few kHz instead of MHz. And the trick is to use CMSIS FFT followed by fast optimized ATAN2 phase difference extraction. I use ATAN2 based on ATAN lookup table. Many radars use FMCW, and it is pretty simple too. Need to distinguish between "slow" and "fast" FMCW. Radar on the photo is 24GHz (or near) band. Such radars use "slow" FMCW, and some use MFSK (FSK superimposed on FMCW ramp). Newer 77GHz  radars usually use "fast" FMCW. But there are more mofulations and algorithms, e.g. "MUSIC" and others. Just Google for those. So where to start? Find out power pins, control pins and mixer output pins, and you can start experimenting by observing signals on oscilloscope or microcontroller, and try different modulation, FFT, etc. If DSP board is not severely damaged, you can reuse it's opamp part, but it will require good soldering skills. I'll be checking this thread! Thanks for the photos, I collect them.

Edit: probably most important thing that can help is to experimenting with recorded signals.  E.g., you can record two channels from two antennas using stereo microphone input, and then try different algorithms using Matlab, Python, custom cpp wav reader with fft, peak finding, extract target speed and angular position.


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