GPS-Fiber Transmitter

GPS-Fiber Transmitters (Downlink) Example: Fiber Optic Transmitter Remote Unit 
AMDI’s GPS over Fiber system is used to bring GPS signals to locations that are too far from the antenna to accommodate RF cable losses. This method of optical signal processing eliminates the need for large coaxial cables and booster amplifiers. Systems are available in various channel configurations and power options.

The design and build of GPS over Fiber systems requires an understanding of the GPS signals and levels. Receiving low level (-130 dBm) signals, and converting these signals to light and back to RF, requires high linearity and extremely low group delay. AMDI brings this knowledge to the commercial market with the 1478GPSFO family of products.

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The Model 1478GPSFOT3 Remote Unit consists of Fiber Optic Transmitters and a dual (redundant) power supply. The Transmitter converts the RF signal from a GPS antenna to fiber optic. An on-board Bias-T provides +5 V to power the LNA in the GPS antenna. The transmitters are housed in a card cage and plugged into a backplane board. The card cage accommodates from one to four boards Fiber Optic Transmitter boards.

Each Fiber Optic Transmitter board contains the Fiber Optic transmitter module (FOT), a micro-controller, a Cross Band Coupler (CBC), and a 2.4 GHz spread spectrum (SS) module. The controller constantly samples the status of the FOT.  The status information is  converted into a serial message that is input to the SS module. The output of the 2.4 GHz SS module is combined with the GPS signal (1565 MHz to 1585 MHz) in the CBC, and this combined RF signal is input to the FOT.

Transmitting the status information down the fiber allows for remote monitoring of the transmitter status at the base station. A USB port is provided at the transmitter module to allow for local maintenance and diagnostic functions.

Fiber Optic cables connect the transmitters  1478GPSFOT3 Remote Unit to the receivers in the 1478GPSFOR3 Base Station. The 1478GPSFOR3 Base Station is described in a separate data sheet.