I'm using PGA460 with transformer driven method. To decrease the minimum measurable distance I wanted to try bi-static mode. The first issue was to reduce acoustic coupling. But there also seems to be a considerable electric coupling between OUT and IN signal. How can I reduce this coupling. Actually I can't get a benefit from using bi-static mode.
Hi Marc,
The electrical coupling between OUTA/B and INP is unintended, but this is one of the negative trade-offs of the integrated driver and receiver IC. To more ideally isolate the two would require a large package, and increased costs. Fortunately, the design team has done a great job mitigating this unintended coupling since the amplitude of the internal electrical coupling is far weaker than the actual acoustic return echos at short range.
I have demonstrated this to be true using the following example:
In the first screen capture, you will see the false positive generated by the internal electrical coupling. This false positive is repeatable at approximately 5cm with an amplitude of 140. The actual object was positioned between 10~25cm (see the overlapping echo data dump results):
In this second plot, the object was moved as close as possible to nearly 0cm. Here you will see that the actual acoustic echo returns far exceed the amplitude of the internally generated false positive:
If you set the threshold to an initial level of 150, you can ignore the peak of the false positive, but still capture actual acoustic returns with override/mask the false positive.
Here are the ultrasonic measurement results (UMR) when using the following register map config:
|
UMR:
|
Register Map: ;GRID_USER_MEMSPACE |
