PGA460: Short range with bi-static transducer pair

Hi MartinW,

You have made the appropriate changes to enable a bi-static configuration on the transformer mode of the daughtercard based on SLAA755-4.4.5. There are no additional changes required on the hardware or software.

If you heard an audible click in the mono-static mode, you should still be able to hear the audible click in the bi-static mode since the bi-static hardware modifications do not affect driver operation. Can you probe OUTA/B and the positive terminal of the transducer to check for driver activity during the burst/listen command? Depending on the probe results, I may be able to provide additional troubleshooting guidance.

Once the driver failure is resolved, you should be able to achieve the <0.3m minimum range requirement. The addition of the horn is what makes a 0.3m minimum more difficult to achieve due to the extended localized echo reflection taking place within the horn's cavity. A separate receive-only sensor is recommended if you have already attempted to optimize the damping resistor and tuning capacitor. Which specific transducer part number are you evaluating at this time?

If you want to eliminate the horn, and still be able to detect 0.3~8m in a narrow field-of-view, I recommend the Prowave 400EP250.

Dear Akeem,

Thank you for your feedback.

I have measured the voltage at the transducer.
When R36 is desoldered, there is no voltage at the transducer.
If R36 (=0Ohm) is soldered, the transducer works and I can measure distances...

??

I follow Figure 12 (SLAA733 - page 12). I have change nothing else.

I think I need a horn for my application, because I want to measure a person (with cotton clothes,...) in 8m. I have tested various closed transducers, but could only measure up to 5-6m with horn. Even if the transducer has a pressure level up to 100dB (@30cm) and a very narrow angle of the beam. But I haven't check the Prowave 400EP250.

Currently I am using an open transducer EKULIT A-16PT/R10 with +120dB SPL; -65dB sensitivity; 40kHz; 60° directivity.

Best regards,

MartinW

Dear Akeem,

I "solved" the problem with the transducer. I replaced the transducer, then it worked...

But now I am faced with the same problem of measuring a person between 0.3m and 8m. I increase the pulse rate or the current I reach the 8m, but I do not come under 0.35cm. 3cm closer than in the monostatic application.
If I damp more, I won't reach the 8m.

Now I use transmitter and receiver, each with horn.

Without a horn I can't get to 8m in any way.
I tested 10 different transducers (closed & open).
A wall in 10m is no problem.

Unfortunately, the specified transducer from Prowave will only be available in a few weeks.

Is there another recommendation?
Ideally with a diameter of 14 - 18mm?

Best regards

Hi Martin,

You can also add a separate damping resistor to the receiver to help reduce the ring-decay time.

I recommend that you keep your initial gain as low as possible to prevent the receiver from saturating too early. A TVG leve initialized at 32.5dB with a short range digital gain of x1~2 is recommended for short ranging with a bi-static solution. After the decay subsides after several centimeter (i.e. 10~20cm), you then quickly ramp-up the TVG level to +50dB, and increase the digital gain to x8~x32 for long range detection.

I do not have any transducers to recommend for very long range with a small diameter. A  transducer horn / wave-guide is your only other option when considering small diameter transducers.