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BOOSTXL-TUSS4470: Noise on Bistatic configuration

Part Number: BOOSTXL-TUSS4470

Hello, I'm trying capture echo signal with two 1Mhz transducers on two sides on 9cm water tank. I was using just one transducer but blind zone was longer than echos returning time. In my application i must measure echos frequency and i'm using zero-crossing output(O3) for that.

With 2 transducers I was thinking i can get rid of ringing on RX transducer after burst pulses because that ringing also triggering zero-crossing.

In that photo above Yellow is Tx transducer, Blue is zero-crossing

Second picture is Rx transducer(Yellow) , Tx transducer(Blue) 

As you can see Rx transducer also ringing at the beginning of the burst pulses and that triggering zero-crossing and I can't capture the frequency of echo signal.

That's my registers.

What can i do for solve this problem can you help me ?

Thank you for your kind interest,

Regards

  • Hello Omer,

    Thank you for posting to the PS forum. Please allow me to review your question on Monday and I will get back to you with a response. We appreciate your patience!

    Best,

    Isaac

  • Hello Omer,

    Just to verify, did you remove resistor R12 from the BOOSTXL-TUSS4470 EVM board? Out of the box the device is configured for monostatic measurements so if you add a transducer to the J3 jumper then you will receive the return echo but then you will also see it capture data but the ringing of transducer will also be present.

    Removing R12 still have some signal coupling into your return path but the decay should be much faster. If you could please verify that you have done this and we can review any possible next steps.

    Best,

    Isaac

  • Hey Omer,

    Thanks for confirming that. It is pretty common to see energy coupling from the TX path to the RX path  when working on the same EVM although it should be far less than you would see when only using one transducer.

    There should be a couple of things that you can do to ensure your ringing period is as small as possible. Some of the items you can do outside of hardware would be to ensure that your transducers are mounted to the tank properly. You want to make sure they have good contact and that you apply a dampener to the back of the transducer. This will lessen the ringing period. You can also add a damping resistor in parallel to the transducer to reduce the ringing-decay time.

    The damping resistor make a huge difference as far as ringing and decay goes here is an image from one of our app notes for reference:

    Your register settings look pretty good, I dont see much are of concern there. How long of a decay time are you seeing on the RX during the ringing period?

    Best,

    Isaac

  • Hey Isaac,

    thanks for your reply. Without damping resistor decay time was 124us. With 10ohm damping resistor its around 20us but i can't capture the echo this way.

    But maybe it's because of how I mounted the transducers to the tank.

    I will inform you on monday.

  • Hello Omer,

    Thanks, I look forward to hearing your update on Monday. Just as a quick question is the damping resistor placed on the TX or RX transducer?

    Best,

    Isaac

  • It's parallel to Rx transducer

  • Awesome just wanted to confirm Omer. Could you provide a scope capture of the TX and Rx channel during the burst?

    I want to make sure that the RX channel ringing period is indeed lower  than the Tx channel ringing period.

    Best,

    Isaac

  • Sorry for my late response Isaac. I fixed the problem. It was all about with my setup. I was mounted transducer to the tank wrong. I fixed it And probably 20us decay time is okay with my project.

    Yellow is Tx and the Blue is Rx

  • Hey Omer,

    Nice glad to hear it is better now!

    Best,

    Isaac