GLOBALSTAR PROPRIETARY AND CONFIDENTIAL INFORMATION
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document.
06/18/20
Subject to Change without Notice
P a g e | 80
7
ANTENNA TUNING GUIDANCE
7.1
GPS / Satellite Antenna Tuning
If the VAR wants to tune the internal GPS / satellite antenna on the PCB for a specific enclosure / environment, the
following should be used as guidance.
1.
An appropriate vector network analyzer (VNA) should be used to measure return loss (S11) of the antenna. The
VNA output should be 50 ohms, and the frequency range should go up to about 3MHz but can be higher if the
VNA allows. A two port VNA is not necessary but can be used (only one port measurements will be done for
antenna tuning). The VNA should have the Port Extensions feature, which will allow for more accurate antenna
tuning. In this manual, the TR5048 VNA from Copper Mountain Technologies is used.
2.
Two ST100 boards will be used for the antenna tuning: one board will be used as a calibration board, and the
other board will be used for tuning the GPS / satellite antenna.
3.
The ST100 board should be placed in the plastics/enclosure where it will be used, and in an orientation that best
represents the end-application. When tuning the antenna, try not to have metallic surfaces nearby. Placing a
cardboard box under the ST100 is one way to move the antenna aw
ay from the surface it’s rest
ing on.
4.
Both ST100 boards will have hardware modifications (swapping resistors, etc.) done to it during the tuning
process. This procedure assumes that the user has some experience with soldering surface mount components
(0201 inductors, resistors).
5.
On both PCBs, make sure there are no components installed on R2, R16, L13, and L14.
6.
On the calibration ST100 PCB, install a 0 ohm, 0402 resistor as shown below, and connect the left pad of L21 to
GND, as shown. Note: some solder mask can be scraped away on the GND plane to access GND.
