hai every one, i have one doubt, with FM broadcast signals i started modeling the passive bistatic radar, where i received one signal from target(echo signal,moving target with constant velocity), another signal from direct path(called reference signal) these two signals were correlated and got some peak(s), now my problem is how can i prepare threshold and how can i detect the target,
Forming the threshold depends on the the algorithm of detection. Generally you need to uassign the false alarm rate then depending on the algorithm you use , the threshold is formed. You can use fixed threshold or CFAR detectors. To adjust the threshold at certain false alarm rate , inject the noise only to your system them modify your threshold to maintain the required false alarm rate. If you want to use CFAR detectors , I advise you to model the threshold as the output of a filter . If you need more details on the modelling of radar detectors and the calculation of detection probability, I can help.
i agree with Ahmed and add , You correlate the echo and the the direct signal you find correlation peaks and you want to decide if your target is is hit or not. Then you have to calibrate your system to find the correlation peak when not hitting the target and the correlation pea when hitting the target. Through this calibration you can find your threshold.
But a question when you your target is moving you will get Doppler shift, would you determine this Doppler shift and how. YOU have to send a single carrier frequency and mix with it the received echo signal, the difference will be the Doppler shift. it can be an indicator of the target and its speed.
best wishes
If a Doppler shift is considered, Moving Target Detector (MTD) can be used. It is implemented in the form of FFT along the PRIs of the recived target and it is easily fitted with a correlator receiver.
thank you for your answers, i performed correlation ( using FFT' s) on both echo signal and direct path signal and i found peak(s) , for moving target with constant velocity, now i want to know how to prepare the threshold value and modeling of radar detectors and calculation of detection probability. and how can i calibrate tge system.
you should first set the threshold for a fixed value of false alarm rate. This is done by injecting noise only to your system and calculate the number of noise samples exceed threshold. Change the threshold value till you get the required false alarm rate. In most cases, 10^-6 is a good value for false alarm rate.
One good way of verifying the proper functioning of your detector is through Monte Carlo simulations. They allow estimating the exact threshold value for guaranteeing a given false alarm probability. I have used this method for the Weibull distribution in the following paper.
Good Luck!
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Hello all i want ask Venu Dunde how can you performecorrelation using FFT, is it possible to help me?
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