DN038 helical antenna for 1.24mm PCB
Part Number: CC1310
I am creating a custom PCB with the CC1310 RF transceiver and the DN038 antenna layout. For packaging reason, the antenna layout will be close to a metal plane, so I am looking for some suggestions about the minimal distance required between the antenna and such undesired ground plane in the vertical direction (beneath the antenna) for acceptable performance. Obviously, I imagine that I have to optimize the antenna network matching due to this ground plane, but probably the efficiency will be limited if such distance is limited to few mm. Do you have any minimal distance? Is there also a minimal distance required between the antenna and a plastic wall? Can the DN024 layout, instead, be used with a bottom ground plane to overcome this problem? Many thanks.
I presume the metal plane will also be grounded. The closer the GND plane/metal to the antenna, will reduce the BW and the efficiency of the antenna since it will be loading the antenna. DN038 is a nice little antenna for 868 MHz or 915 MHz but the bandwidth (BW) is quite small. Most final products would like to cover both 868 MHz (Europe) and 915 MHz (US) ISM bands. If you are just looking at a single band then this reduces the requirement slightly.
A "general rule of thumb" is to try to maintain at least 5% of the wavelength distance to the antenna in order not to severely reduce/affect the performance.
Both DN038 and DN024 are monopole antennas which are dependent on the GND plane size so the effects will be similar. However, DN024 is a larger antenna with a larger BW and greater efficiency. Also, the exact length of the antenna is dependent on the GND plane size.
The tricky part with antennas is the mechanical constraints of the final product will always affect the performance. If you try to maximize the volume that you have available for the antenna whilst maintaining a clearance distance in order not to load the antenna to the surroundings will give the best performance.
If you can share your layout and mechanical constraints then I can review it more.
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