H Heuer Instruments UMDT51A, Руководство пользователя

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Performance Testing
LT51 User Manual 84
Return Loss Measurement Response
a) Set the LT51 to Return Loss mode.
b) Set the LT51 Zrtx impedance to 75

and ensure the RTXa-b terminals are
shorted together.
c) Set the Oscillator level to -10 dBm and frequency as indicated in Table 8.5
d) Step down the frequencies in Table 8.5 and check that the readings are
within the ranges specified.
Tx Frequency Ret. Loss reading
10 kHz 0 dBm ± 0.25 dB (ref)
100 kHz
0 dBr

0.5 dB
1 MHz
0 dBr

0.5 dB
2 MHz
0 dBr

0.5 dB
Table 8.5
Return Loss Measurement
a) Set the LT51 to Return Loss mode.
b) Set the LT51 TX frequency to 10 kHz and TX level to -10 dBm.
c) Set the LT51 RTX impedance as indicated in Table 8.6 and connect the
load impedance to the RTX terminals.
d) Check that the readings are within the ranges specified.
RTX Impedance Load Impedance LT51 reading
50

100

9.54 dB ± 1 dB
75

100

16.90 dB

1 dB
600

590

41.5

2 dB
Table 8.6
NOTE: For other value resistors (Rm) at a Zrtx ref., calculate the Return Loss:
Return Loss = 20 log ((Zrtx - Rm) / (Zrtx + Rm)).
Intrinsic NEXT (Near End CossTalk)
a) Set the LT51 to NEXT mode and TX-RX interface mode.
b) Set the LT51 RTX impedance to 600

and ensure the RTXa-b terminals
are terminated with 600

.
c) Set the LT51 Tx Source to SWEEP and the BW to 200 kHz.
d) Ensure that the measured NEXT is <75dB for all freqs < 200 kHz.