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5/25/2007
Document number: 060-FSA-ABQ-AAS-AGZ
Rev. 001
down to the application’s receiver(s). As such, each input and output port of the S14WI
includes a “Bias-T” functionality which allows for DC voltages to be applied on the center pins of
the RF connectors. In this arrangement, DC voltages for powering the antenna may be applied
to the center pin of the RF outputs. The DC voltage passes through the RF chokes to the DC
Bias Select System and on to the RF input connector to power the antenna. This DC voltage is
blocked from the RF section by DC blocking capacitors.
Antenna DC Bias Select System
The S14WI splitter requires that a DC voltage be applied to one or more of the RF output ports
by way of the RF connector center conductor. If DC voltages are applied to more than one of
the RF output ports, the S14WI DC Bias Select System will choose one of these DC inputs to
power the active circuitry of the S14WI and will also pass this DC voltage through the splitter to
the center conductor of the RF input port. The DC voltage available on the RF input port can
then be used to power the application’s active antenna. The DC voltages applied to the RF
outputs that are not chosen by the DC Bias Select circuitry will be automatically switched
through an RF choke to 200Ohm DC loads. The DC voltages may be applied to any or all of the
RF outputs; however, the DC Bias Select circuit will always select the DC voltage on the lowest
numbered RF port that has a DC voltage applied to power the S14WI and the application’s
antenna. If the chosen DC input were to be removed or fail, the DC Bias Select circuit will
automatically switch to the next higher numbered RF port to which a DC voltage is applied.
The S14WI requires that only one RF output port have an external DC voltage applied (i.e. the
device will operate properly even if any one, two, or three ports do not have a DC voltage
applied or if a DC voltage is removed from one of the ports). Ports that do not have an external
DC voltage applied or from which an external DC voltage is removed are internally pulled down
so as to ensure that false input voltage indications do not occur.
Example:
Assume DC voltages are applied to RF outputs 1, 3 and 4. In this scenario, the DC voltage on
port 1 will be used to power the S14WI and the application antenna. Ports 3 & 4 will be
switched to 200Ohm DC loads.
Now assume that the DC voltage on port 1 is removed. The S14WI will automatically terminate
the input internally with a pull down resistor and switch operation of the splitter and antenna to
the DC voltage applied to the next high numbered port with a DC voltage applied: port 3. Port 4
will remained switched to a 200 Ohm load.
Active GPS Antenna Monitoring System
