ublox JODY-W2 Antenna Reference Design Instructions
- June 6, 2024
- Ublox
Table of Contents
ublox JODY-W2 Antenna Reference Design
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Scope
This document defines the essential specifications necessary to implement the
JODY-W2 antenna reference designs as used in certification. It is part of the
equipment certification application issued to FCC and ISED. The information
contained herein and its references should be sufficient to guide a skilled
person to implement the design on a host carrier. It will provide the designer
with PCB layout details and expected performance specifications.
This document supports a connector-based design for the use of external
antennas (one for each antenna pin of the module).
General description and requirements
JODY-W2 series modules provide two RF interfaces for connecting external antennas. The antenna ports ANT0 and ANT1 have a nominal characteristic impedance of 50 Ω and must be connected to the related antenna through a 50 Ω transmission line to allow proper impedance matching along the RF path. A bad termination of the pin may result in poor performance or even damage the RF section of the module. For optimal performance in multiradio mode, the isolation between the antennas shall target the requirements as specified in Table 1 and Table 2 in order to ensure good performance.
| Item | Requirements | Remarks |
|---|---|---|
| Impedance | 50 W nominal characteristic | The impedance of the antenna RF |
connection must match
| impedance| the 50 W impedance of the antenna pins.
Frequency range| 2400 – 2500 MHz| For 802.11b/g/n and Bluetooth.
| 5150 – 5850 MHz| For 802.11a/n/ac.
Return loss| S11 < -10 dB (VSWR < 2:1)| The return loss or the S11, as
the VSWR, refers to the
| recommended| amount of reflected power, measuring how well the primary
| S11 < -6 dB (VSWR < 3:1) acceptable| antenna RF connection matches the 50 W
characteristic
impedance of antenna pins.
| | The impedance of the antenna termination must match as
| | much as possible the 50 W nominal impedance of antenna
| | pins over the operating frequency range, to maximize the
| | amount of power transferred to the antenna.
Efficiency| > -1.5 dB ( > 70% ) recommended| The radiation efficiency is
the ratio of the radiated power to
| > -3.0 dB ( > 50% ) acceptable| the power delivered to antenna input: the
efficiency is a measure of how well an antenna receives or transmits.
Maximum gain| | The maximum antenna gain must not exceed the value
| | specified in type approval documentation to comply with
| | regulatory agencies radiation exposure limits.
Reference design of RF path
JODY-W2 is certified with a set-up including JODY-W2 module board with it’s RF paths connected to the carrier board with RF coaxial cables. The antennas are connected to the carrier board through SMA connectors. Below are the relevant components listed.
- Module board including U.FL connectors with JODY-W2 mounted.
- Carrier board including U.FL connectors to interface the module board and SMA connectors to connect antennas.
- Coaxial cables with U.FL connectors connecting the module board’s RF traces to the carrier board’s RF traces.
- Antennas connected to the carrier board’s SMA connectors.
Figure 1. Definition of Module board and Carrier board 
Figure 2. Test set-up.
RF trace PCB routing
The PCB routing connecting the module’s antenna pins to module board U.FL connectors are designed with coplanar microstrips. Coplanar microstrips are also used on the carrier board connecting the U.FL connectors with the SMA connectors to which the external antennas or test equipment are connected. Figure 3 and Table 3 shows the design stack-up including dimensions of the 50 Ω coplanar microstrips implemented. Regarding the coplanar microstrips the ground planes beside the signal trace are connected to the inner layer ground plane using vias. The vias are placed with a maximum distance of 0.5 mm to the coplanar ground edge and a maximum pitch of 2 mm. The top layer is coated with generic LPI solder stop mask. The SMA connectors on the carrier board are used for mounting antennas. For Bluetooth and Wi-Fi operation in the 2.4 GHz band and Wi-Fi operation in the 5 GHz band, the module has been tested and approved for use with antennas up to 2 dBi antenna gain.
Figure 3: Coplanar micro-strip dimension specification
| Item | Value |
|---|---|
| S | 200 µm |
| W | 700 µm |
| T | 35 µm |
| H | 800 µm |
| T | 4.3 |
Table 3: Coplanar micro-strip specification
The mechanical dimensions of the module board’s microstrips and position of the pi network impedance matching components are shown in Figure 4. Figure 6 shows the components used for the PI network impedance matching. Here only series 0 ohm resistors are used. The inner layers have the same dimensions and are filled with ground. No RF traces are routed in these layers. The antenna ports shown in Figure 4 on the right hand side are from top to bottom: ANT1, ANT0, and ANT2. ANT2 is not used and shall be left unconnected.
Figure 4. Module board Antenna micro strip implementation.
Figure 5. Component selection for RF matching network on module board using 0 ohm series resistor.
The carrier board RF traces includes pi network matching components and are routed as coplanar microstrips. Here 10 pF capacitors in series are implemented.
Figure 6. Carrier board Antenna microstrip implementation.
Figure 7. Component selection for RF matching network on carrier board using 10 pF series capacitors.
Parts
Evaluation board (EVB) Evaluation board for JODY-W263 series modules.
The board includes SMA antenna connectors that connect to external antennas
for Wi-Fi and Bluetooth. It has two internal dual-band Wi-Fi/Bluetooth
antennas. 
External Antennas (2) 1 x dual band Wi-Fi/Bluetooth
- antenna,
- Linx Technologies
- ANT-DB1-RAF-SMA
Coax RF cable
- U.FL-2LP(V)-04N1-A-(40)
Revision history
| Revision | Date | Name | Comments |
|---|---|---|---|
| R01 | TBD | lber | Initial release. |
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