Design of an asymmetrical Horn for ch-201

Hello together,

I am working on a project where the sensor is part of a traveling object and is aligned, so that the sensor faces 90 ° left to the direction of travel.
What I am looking for is the possibility to restrict the detection angle on the front side of the moving object.
The numbers are not set in stone and need more testing. But what I am looking for is close to this:

Angle of detection in reference to direction of travel: from 45° CCW to ~160° CCW.

The usecase is, that I want to be able to distinguish between an object that is coming from behind or from the front.

Thanks a lot.
Kind regards
Helge