Antenna Placement And Routing; Transmission Line Considerations - Texas Instruments SimpleLink BoosterPack BOOSTXL-CC3120MOD Manual

6.4 Antenna Placement and Routing
The antenna is the element used to convert the guided waves on the PCB traces to the free space
electromagnetic radiation. The placement and layout of the antenna are the keys to increased range and
data rates. Table 6‐2 provides a summary of the antenna guidelines.
Item
1 Place the antenna on an edge or corner of the PCB.
2 Ensure that no signals are routed across the antenna elements on all the layers of the PCB.
3 Most antennas, including the chip antenna used on the booster pack, require ground
clearance on all the layers of the PCB. Ensure that the ground is cleared on inner layers as
well.
4 Ensure that there is provision to place matching components for the antenna. These must be
tuned for best return loss when the complete board is assembled. Any plastics or casing must
also be mounted while tuning the antenna because this can impact the impedance.
5 Ensure that the antenna impedance is 50 Ω because the device is rated to work only with a
50‐Ω system.
6 In case of printed antenna, ensure that the simulation is performed with the solder mask in
consideration.
7 Ensure that the antenna has a near omni‐directional pattern.
8 The feed point of the antenna is required to be grounded. This is only for the antenna type
used on the CC3120MOD BoosterPack. Refer to the specific antenna data sheets for the
recommendations.
6.5 Transmission Line Considerations
The RF signal from the device is routed to the antenna using a Coplanar Waveguide with ground (CPW‐
G) structure. The CPW‐G structure offers the maximum amount of isolation and the best possible
shielding to the RF lines. In addition to the ground on the L1 layer, placing GND vias along the line also
provides additional shielding. Figure 6‐5 shows a cross section of the coplanar waveguide with the
critical dimensions.
Table 6‐2: Antenna Guidelines
Figure 6‐5: Coplanar Waveguide (Cross Section)
Guidelines