Differential NECL Fanout w/Monitor

A satellite customer in Korea needed a custom buffer and switch matrix to select feeds from 2 of 3 receivers and distribute the outputs to two pairs of frame synchronizers and a monitor/test point, so that a controller could activate the backup receiver in case of a failure.

This was designed with all off-the-shelf PRL products, and required no engineering.

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The Task:

Distribute NECL I/Q  Differential NECL streams from 3 receivers into an acquisition path and a monitor path, with each acquisition path feeding two frame synchronizers, under computer control.

    The Solution:

    A set of eight PRL-431AN-SMA, 1:2 Differential NECL Fanout Buffers, two PRL-434A, 1:4 Differential NECL Fanout Buffers, four PRL-852A-RM-SMA switches, and a PRL-4216N, 16:2 NECL Terminator/Scanner were integrated into a PRL-MRK-3-1 Rackmount Kit.

    The switches are controlled by a PRL-USB-I/O module and all the modules are powered by the internal power supply, and distributed by a PRL-730 DC Power Distribution module. 

    Each of 3 satellite receivers feeds Differential NECL I/Q streams into a pair of PRL-431AN NECL fanout buffers. One I/Q stream goes into a switch, and the other goes into a PRL-4216N Differential NECL Scanner/Terminator, where the levels are shifted to allow monitoring on a standard 50 Ohm oscilloscope.

    Each of two pairs of PRL-852A-RM, 2 x 1:2 RF Switches selects an I/Q stream either from the Primary receiver or from the Backup receiver, and the selected I/Q stream then feeds another pair of PRL-431AN fanout buffers to feed two Frame Synchronizers. 

    This architecture provides redundancy at every point in the signal chain, while providing a scannable test path to monitor for failures and switch receivers as necessary.

    The "I" half of the solution is diagrammed above; an identical "Q" path is omitted for clarity..