Radyne OM20 Specifications download pdf (Page 43)

OM20 Universal Outdoor Modem OM20 Theory of Operation

MN-OM20– Revision 5 4–5

4.2.2 Tx Baseband Processing

The Tx Data and Clock enters the Baseband Processor, passes through a Rate Adapting FIFO,

and enters the Framer/Drop Processor. In Closed-Net Mode, the data passes through the Framer

unaltered. In IDR, IBS, and D&I Modes, the framer adds the appropriate framing and ESC as

defined in IESS-308 and 309. In D&I Mode, the framer acquires the terrestrial framing structure,

E1 or T1, and synchronizes the Drop Processor. The Drop Processor extracts the desired time

slots from the terrestrial data stream and feeds these channels back to the framer. The framer then

places the ‘dropped’ terrestrial time slots into the desired satellite channel slots. The data is then

sent to the Reed-Solomon Encoder.

The Reed-Solomon Encoder encodes the data into Reed-Solomon Blocks. The blocks are then

interleaved and synchronized to the frame pattern as defined by the selected specification (IESS-

308, IESS-309, DVB, etc.). After Reed-Solomon Encoding, the composite data and clock are

applied to the Baseband Loopback Circuit.

4.2.3 Rx Baseband Processing

The Receive Processor performs the inverse function of the Tx Processor. Data received from the

satellite passes through the Baseband Loopback Circuit to the Reed-Solomon Decoder to the

Deframer. The Deframer acquires the IBS/IDR/DVB frame, synchronizes the Reed-Solomon

Decoder and extracts the received data and overhead from the frame structure, placing the data

into the PD Buffer, sending the overhead data to the UIM. In Closed-Net Mode, the data is

extracted from the buffer and is sent to the UIM. Backward Alarm indications are sent to the

M&C Subsystem. In Drop and Insert Mode, the Insert Processor synchronizes to the incoming

terrestrial T1/E1 Data Stream, extracts satellite channels from the PD Buffer, and then inserts

them into the desired terrestrial time slots in the T1/E1 Data Stream.

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Radyne OM20 Specifications Page 43