I need to deploy a set of sensors in radio communication frequencies (it can be in 2.4 GHz, 915 MHz or whatever else you consider suitable) that attaches onto a metal barrier like a big shovel. The question is what type of antennas is suitable in that kind of situation?, because we do some small test and there are a lot of communication problems that we want to avoid. The nodes communicates with a base station in infrastructure mode. We planned to put a patch antenna in the base station for directional pattern pointing to sensors node. The sensors have omnidirectional antennas because the shovel moves at a times. The distance between sensors nodes and base is no more than 5 meters.
If the antennas are attached to a metal background an antenna with a ground plane like a patch should be suitable. This antenna will be less influenced by the metal back ground but will of course not Omni directional. The metal plating of the shovel could also work as a mirror so at a correct distance you could place a monopole or dipole. Normally the metal does not alone influence he radiation pattern but also the impedance of the antenna so using an antenna with a large bandwidth could help to overcome impedance mismatch.
I forgot to add a important design issue. We have a base mounting behind the shovel and the shovel always will be in front of this base, giving back. Considering that, and also that sensor only can be deployed onto the shovel, what kind of antennas can I put in there? because metal act like a mirror. So pointing antennas to the base will not be successful because waves can't pass metal barrier conductor.
I uploaded a rapid design for reference.
Are the sensors autonomous or are they powered by the vehicle? Is this shovel attached to a vehicle. In Dutch we call the whole machine (see picture a shovel). Normally you could benefit from the reflections from the environment. Could this be an option in your case? An other possibility is to place the antennas on the back of the shovel. What also could happen, because the shovel is in the near field of the antenna, that it will be detuned. Did you investigate that? Furthermore the antenna will introduce some current into the metal and thus diffraction on the edges of the shovel, this could be in you advance.
That is interesting thing. In my opinion, you must design array antenna If your designed antenna like photo deployed on big shovel, a lot of interference between antenna to antenna and antenna to edge of big shovel. Also you have difficult fed method. Consequently you calculate square of big shovel, next will design array antenna of beam pattern suite at shovel.
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