California Eastern Laboratories ZICM357SP2 ZigBee Development Kit User Manual Professional Letter

California Eastern Laboratories ZigBee Development Kit Professional Letter

Contents

  • 1. manual
  • 2. external antenna trace instructions

external antenna trace instructions

4590 Patrick Henry Driv
e
Santa Clara, CA 95054-1817
Telephone: (408) 919-2500
Facsimile: (408) 988-0279
Host Board Layout Requirements
For using external Antenna with
ZICM357SP2-1
California Eastern Laboratories (CEL) MeshconnectTM ZICM357SP2-1 module has been
certified for use with an external antenna through the use of the ZICM357SP2-1
castellation Pin, a U.FL connector, and a U.FL cable assembly with Nearson Whip
Antenna. This document details the implementation used to obtain the regulatory
certification. This implementation may be used on other Host boards provided the
implementation follows the requirements presented in this document.
The RF signal can be routed to castellation pin 32 during manufacturing by ordering
CEL Part Number ZICM357SP2-1C. The module has castellation pins 31 and 33
connected to ground to provide the ability to implement a 50Ω co-planer transmission
line on a standard two layer FR4 printed circuit host board with thickness of 0.062
inches.
Coplanar Waveguide
The coplanar with ground plane waveguide structure is made up 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.
An screen shot of the gerber layout is shown below. 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. The image in red
represents the top layer, while the green is the bottom layer on the two layer FR4
printed circuit board.
Components Used in the implementation
The following components specify the requirements for this implementation.
• CEL Module Part Number: ZICM357SP2-1C
• U.FL Connector Part Number: U.FL-R-SMT(10) from Hirose Electric Co. Ltd.
• External Antenna: Nearson S181AH-2405S Half-Wave Dipole
• Host Board: FR4 two layer, 0.062” thick with dielectric constant of 4.2 typical.
The transmission line between the module and the U.FL connector should be
a straight line with a width of 40mils, and ground plane spaced 8 mils apart on
the top layer. The bottom layer should be a continuous ground plane under
the transmission line. Ground vias should be included between the module
castellation pins and the U.FL connector ground pads to provide a good RF
ground connection.
• Cable assembly between the U.FL connector on the host board and the
Nearson Whip antenna must be a minimum of four inches in length.
An photo showing the implementation is shown below for reference.
Design Verification Test Procedure
Any manufacturer that chooses to implement the external antenna on their Host board
should verify that the implementation was done properly. To assist with this, the
following Test Procedure can be used. The procedure uses a Network Analyzer
capable of making return loss measurements at 2.4GHz.
1. Calibrate the network analyzer for a one port measurement with a center
frequency of 2.44GHz and a span of 200 MHz.
2. Take a blank Host Board and solder a 100Ω resistor between castellation Pin 31
& 32.
3. Solder a second 100Ω resistor between castellation Pin 32 & 33.
4. Solder the U.FL connector on the Host board.
5. Using the appropriate U.FL to SMA adapter for your network analyzer, measure
the Return Loss of the trace. (Either S11 or S22 depending on which port was
chosen during the 1-port calibration).
6. A return loss of -15dB or lower indicates an acceptable implementation (PASS).
A screen shot of the measurement is shown below where Port 2 was used as the
measurement Port.
Production Test Procedure for Ensuring Compliance
During production, Host boards should be tested to ensure compliance. CEL would
recommend that when the Host board is manufactured, Electrical Test is specified to
guarantee that a short is not present anywhere on the host board, including the trace
between the U.FL connector location and the module RF castellation pad. This greatly
simplifies the production test to simply verify that a solder short did not occur during the
component placement and reflow of the host board assembly. This can be confirmed
by verifying an open circuit between castellation pins 32 & 33 using a DC multi-meter.

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