For any Bluetooth Low Energy product, the antenna placement affects the performance of the whole system. The antenna requires free space to radiate RF signals, and it must not be surrounded by the ground plane. Thus, for the best PCB antenna performance, the RNBD451 module must be placed at the edge of the host board.
Align the RNBD451 module ground outline edge with the edge of the host board ground plane (see Figure 6-1).
A low-impedance ground plane for the RNBD451 module ensures the best radio performance (best range and lowest noise). As per the requirement, extend the ground plane beyond the minimum recommendation for the host board EMC and noise reduction.
For the best performance, keep metal structures and components (such as mechanical spacers, bump-on and so on) at least 31.75 mm away from the PCB trace antenna (see Figure 6-1).
Do not place the antenna on the RNBD451 module in direct contact with or close proximity to plastic casing or objects. Keep a minimum clearance of 10 mm in all directions around the PCB antenna (see the following figure). Keeping metallic and plastic objects close to the antenna can detune the antenna and reduce the performance of the device.
Solder the exposed GND pads on the bottom of the RNBD451 module to the host board (see Figure 6-2).
On the other hand, the entire region on the host board except the exposed ground paddle must be solder-masked.
The following figure illustrates examples of the RNBD451 module placement on a host board with a ground plane.Figure 6-1. Module Placement Guidelines
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