SDM-9000 Satellite Modem
Maintenance
Rev. 4
6–3
6.1.2 Modulator
Use the following procedure and the test setup shown in Figure 6-1 to check out the
modulator PCB. Refer to Chapter 5 for the modulator specifications. Section 6.1.4.2 lists
the modulator test points and signal names. Figure 6-6 shows the test point locations.
1. Set up the modem for IF loopback operation by using the Configuration
Demodulator front panel menu, or use an external IF loop with attenuation. Refer
to Chapter 4 for a block diagram of the IF loopback operation.
2. Clear all TX faults by correct use of data and clock selection (refer to
Chapter 4).
3. Measure the E
b
/N
0
with a receiver that is known to be properly operating. Refer
to Figure 6-2 and the following tables to check for proper E
b
/N
0
level:
Modulation Type
Table
QPSK
6-1
8PSK
6-2
16QAM
6-3
Figure 6-2 is an example of a 1/2 rate carrier operating at an E
b
/N
0
of 7.8 dB.
The (S+N)/N is measured by taking the average level of the noise and the
average level of the modem spectrum top as shown. Use this measurement for
the first column on the appropriate table as listed above. Read across the page to
find the S/N and E
b
/N
0
for the specific code rate. Once the demodulator has
locked to the incoming signal, the Monitor menu will display signal level, raw
BER, corrected BER, and E
b
/N
0
.
4. Connect a spectrum analyzer to the modem as shown in Figure 6-1. Ensure the IF
output meets the appropriate mask and spurious specifications. Measure the
power output at different levels and frequencies. A typical output spectrum is
shown in Figure 6-3.
5. To check the frequency and phase modulation accuracy:
a.
Set the modem to the continuous wave Normal mode by using the Carrier
Mode front panel menu (refer to Chapter 4). This sets the Carrier mode in
the OFF condition. A pure carrier should now be present at the IF output.
This should be used for frequency measurement only. Spurious and power
measurements will be inaccurate.
b. Set the modem to the continuous wave Offset mode by using the Carrier
Mode front panel menu (refer to Chapter 4). This generates a single upper
side-band suppressed carrier signal. Ensure the carrier and sideband
suppression is less than -30 dBc.
Summary of Contents for SDM-9000
Page 2: ......
Page 5: ...8 Mbit s w IDR Figure 1 7 16QAM BER Performance Curves with Reed Solomon Filename T_ERRATA 3...
Page 8: ......
Page 27: ...SDM 9000 Satellite Modem Introduction Rev 4 1 5 Figure 1 3 SDM 9000 Block Diagram...
Page 42: ...Introduction SDM 9000 Satellite Modem 1 20 Rev 4 This page is intentionally left blank...
Page 64: ...Configuration SDM 9000 Satellite Modem 3 6 Rev 4 JP1 Figure 3 4 Interface PCB AS 3971...
Page 65: ...SDM 9000 Satellite Modem Configuration Rev 4 3 7 Figure 3 5 Interface PCB AS 4477...
Page 66: ...Configuration SDM 9000 Satellite Modem 3 8 Rev 4 JP1 JP6 JP7 Figure 3 6 Interface PCB AS 5618...
Page 70: ...Configuration SDM 9000 Satellite Modem 3 12 Rev 4 Figure 3 7 Nyquist Filter Installation...
Page 83: ...SDM 9000 Satellite Modem Operation Rev 4 4 9 This page is intentionally left blank...
Page 87: ...SDM 9000 Satellite Modem Operation Rev 4 4 13 This page is intentionally left blank...
Page 104: ...SDM 9000 Satellite Modem Operation Rev 4 4 31 This page is intentionally left blank...
Page 107: ...Operation SDM 9000 Satellite Modem 4 34 Rev 4 This page is intentionally left blank...
Page 124: ...SDM 9000 Satellite Modem Operation Rev 4 4 51 Figure 4 17 RF Loopback Figure 4 18 IF Loopback...
Page 150: ...Theory of Operation SDM 9000 Satellite Modem 5 22 Rev 4 Figure 5 6 Interface Block Diagram...
Page 158: ...Theory of Operation SDM 9000 Satellite Modem 5 30 Rev 4 This page is intentionally left blank...
Page 186: ...Maintenance SDM 9000 Satellite Modem 6 28 Rev 4 This page is intentionally left blank...
Page 218: ...Options SDM 9000 Satellite Modem A 32 Rev 4 This page is intentionally left blank...
Page 242: ...Remote Control Operation SDM 9000 Satellite Modem B 24 Rev 4 ref SE_ command...
Page 254: ...Glossary SDM 9000 Satellite Modem g 6 Rev 4 This page is intentionally left blank...
Page 256: ...2114 WEST 7TH STREET TEMPE ARIZONA 85281 USA 480 333 2200 PHONE 480 333 2161 FAX...