User's Manual

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Document No:
0011-00-16-11-000 (Issue C)
Technical Note
This document is subject to change without notice.
Document No: 0011-00-16-11-000 (Issue C)
Date Published: July 21, 2016
0011-00-16-11-000
Mini Module External Antenna Implementation
INTRODUCTION
This Technical Note describes the host board layout
requirements for using an external antenna with the
MeshConnect™ ZigBee, Thread, and Bluetooth Smart
Mini Modules from California Eastern Laboratories
(CEL). The ZigBee and Thread ZICM35x Mini Modules
have been certied for use with an external antenna
through the use of the Mini Module castellation pin, a
U.FL connector, a U.FL cable assembly and the specied
external antenna. For the B1010SPx Mini Modules please
refer to the datasheet for latest regulatory certication.
This document details the implementation required
to be compliant with the regulatory certication. This
implementation is applicable to any host board provided
the implementation follows the requirements presented in
this document.
The RF signal is routed to castellation pin 32 on the
modules with Part Number ending in "-1C". The module has
castellation pins 31 and 33 connected to ground to provide
the ability to implement a 50 Ω co-planer transmission line
on a standard two layer FR4 printed circuit board with a
thickness of 0.062 inches.
COPLANAR WAVEGUIDE
The coplanar with ground plane waveguide structure
consists of the RF trace on the topside of the printed circuit
board with adjacent ground planes spaced close to the
RF transmission line. A ground plane under the RF trace
should also exist directly below the transmission line.
Since the module castellation pad is 40 mils wide on the
bottom of the module, an RF trace width of 40 mils, along with
a gap of 8 mils separation from the ground plane, will result
in a good 50Ω transmission line. Using the transmission line
width equal to the castellation pad width eliminates any RF
discontinuity which could degrade the return loss.
Figures 1 and 2 below detail the Gerber layout. The
transmission line is 40 mils wide with an 8 mil gap to the
ground. The length of the transmission line is 200 mils long
from the castellation pad to the edge of the U.FL connector.
Figure 1 below represents the top layer, while Figure 2 is
the bottom layer on the two layer FR4 printed circuit board.
Figure 1. Top Layer
Figure 2. Bottom Layer