Comtech-ef-data SDM-2020 Manual do Utilizador descarregar pdf (Página 148)

SDM-2020 Satellite Demodulator Revision 4

ASI/RS-422Data Interface MN/SDM2020D.IOM

9–4

Table 9-1. ASI/RS-422 Specifications

General Specifications

Data Framing Formats 188, 204 byte packets per ETS 300 421, and None.

Hot Pluggable Not required. Unit power is turned off prior to removal or insertion

of the data interface.

ASI Specifications

Data Rate 1.5 to 100 Mbps ASI.

Clock Rate Uncertainty

Programmed data rate ± 100 ppm.

Transport Clock ASI The transport rate is 270 Mbps for all data rates.

Impedance

75Ω.

Return Loss 15 dB, frequencies, 5 to 270 MHz.

Connectors

BNC female, 75Ω.

Electrical Properties Per TM 1449

Packet Types Burst or distributed.

Signal Types Serial data.

Voltage Level

800 mV ± 10% into 75Ω.

ASI Data Loop 3 dB

Cutoff Frequency

2 Hz (see Note 2)

Jitter Tolerance Meets ITU-T G.823 (3/93) and ITU-T G.824 (3/93)

Jitter Transfer

≤ 0.5 dB peaking up to cutoff frequency.

–20 dB per decade beyond cutoff.

Cable Length, Typical RG59

50 m

Belden 8281

70 m

RS-422 Specifications

Data Rate 1.5 to 18 Mbps, serial RS-422.

Clock Rate Uncertainty

Programmed data rate ± 100 ppm.

Connectors 25-pin D female per EIA-530.

Electrical Properties Per RS-422.

Signal Types SD, TT, ST, RD, RT, RS, RR, CS, and DM.

Data synchronization is detected by correlating the data stream

for the MPEG2 sync pattern per ETS 300 421.

Voltage Level

4-± 2V differential into 100Ω.

Notes:

1. Loopback – The yellow TEST MODE LED is illuminated when Loopback is turned

On. During Loopback input data is looped back to the terrestrial data output

connector(s) and data continues into the modulator.

2. Loop Thru – Operation is nearly identical to Loopback, except the yellow LED is not

illuminated. Conceptually, the data output is operating as a monitor point.

3. Rev. A or later assemblies include this capability. Rev. dash (-) assemblies can be

upgraded to this capability.

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