Honored Contributor
Honored ContributorDear Dave, please take a look at my comments bellow.
--- Quote Start --- Do you get to control the ultrasonic source and signal? Since you indicate you plan on sampling both a reference source and the echos, I would guess not. --- Quote End --- I guess I have control over the process of exciting the ultrasonic sensor as well as receiving its signal. Take a look at the following picture with the signals I captured.https://www.alteraforum.com/forum/attachment.php?attachmentid=9670 In this case, sampling rate is 909 KSPS, which means one sample at 1.1 us. --- Quote Start --- Your transmit pulse will have a much higher amplitude than your echo, so you will need to make sure you have the gains between the two channels set correctly. --- Quote End --- That's right. I designed a pcb in order to tune the gains required to obtain the previous signals. The pcb I designed is shown in picture placa pronta.https://www.alteraforum.com/forum/attachment.php?attachmentid=9671 --- Quote Start --- What do the response echos look like? If they are noisy or have multi-path signals, you may require some additional signal processing. --- Quote End --- Take a look at the signals picture. Could you tell me which signal processing you're thinking? --- Quote Start --- How were you planning on cross-correlating the signals? Using lag correlation, or FFTs? Cheers, Dave --- Quote End --- I guess I'm using lag approach. After studying this book, http://www.ece.rutgers.edu/~orfanidi/osp2e/osp2e.pdf (http://www.ece.rutgers.edu/~orfanidi/osp2e/osp2e.pdf) I implemented in NIOS the following formula (I left in Latex type setting if you don't mind): \begin{equation}\label{eq:xcorr} R_{xy}[k]=\dfrac{1}{N}\sum_{n=0}^{N-1-k}y_{n+k}x_{n} \end{equation} Where R_{xy} is the correlator function and y and x are the signal's vectors. I hope all of this helped you to understand better my issue. Kind Regards, Tiago
