Comtech EF Data CDM-Qx Manual de usuario descargar pdf (Pagina 2)

Optimizing Satellite Communications

CDM-Qx Multi-Channel Modem with DoubleTalk™ Carrier-in-Carrier™

DOUBLETALK CARRIER-IN-CARRIER EXAMPLE

Normal carrier positioning is shown in Figure 1, reflecting

two carriers positioned side-by-side. Each carrier occupies

a unique frequency band and (for practical purposes) they

do not overlap or interfere with each other.

DoubleTalk Carrier-in-Carrier

allows the two carriers to

occupy the same spectral space, as shown in Figure 2.

Initially, Carrier 1 and Carrier 2 are displayed to show the

carriers in the same space when only one carrier is

enabled. Carrier 1 is slightly higher in level than Carrier 2.

When both carriers are transmitted simultaneously, the

combined energy of both carriers is shown in the

composite trace above the two individual carriers.

Operation with asymmetric data rates is permitted as long

as the symbol rates of the two carriers are maintained

within a factor of 3.

MODEM INTERFACES

CDM-Qx Shown With:

Slot 1 Modulator Card with G.703 Balanced Interface

Slot 2 Modulator Card with G.703 Balanced Interface

Slot 3 Modulator Card with EIA-530 Interface

Slot 4 Modulator Card with EIA-530 Interface

IF 75Ω

Notes:

1. Also shown, placed above the modem are the

modulator and demodulator cards with G.703

Unbalanced (BNC) interface.

2. Select one per modem (i.e. modulator and

demodulator card combination) OR one per

modulator card and demodulator card, if using

independently.

3. Redundant units do not need an interface.

Figure 1

Figure 2

With DoubleTalk Carrier-in-CarrierWith DoubleTalk Carrier-in-Carrier

Composite

Carrier 2

Carrier 1

Without DoubleTalk Carrier-in-Carrier Without DoubleTalk Carrier-in-Carrier

Carrier 1 Carrier 2

A white paper, DoubleTalk



Carrier-in-Carrier



Bandwidth Compression Providing Significant

Improvements in Satellite Transponder Bandwidth, is

available on the Comtech EF Data web site in the

Download section under White Papers.

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