Anritsu MG3641A - Manual (Page 99)

SECTION 5 MEASUREMENT
5.2.2 Measuring spurious response
The spurious sensitivity reduces as the receiver output obtained at reception of the modulated desired-frequency is
different from that obtained at reception of the modulated spurious frequency. To measure the spurious response,
adjust the output level of the signal generator of the spurious frequency so that these two receiver outputs are equal.
Then, obtain that value from the difference between the output level of the signal generator of the desired frequency
and that of the signal generator of the spurious frequency.
When the desired frequency of the receiver is fd; IF frequency is fi; local frequency is fL, the following frequency
is assumed to be spurious frequency fs.
• Image frequency ......... fs = fL
±fi = fd ±2fi
• Higher harmonic ......... fs = fL
±fi/2, fs = nfd ±fi/2
If a frequency that sets the difference from the local frequency to fi/2 is input, the second
higher harmonic of fi/2 changes to an IF frequency and an interference occurs.
• Harmonic frequency of local frequency ....... fs = nfL
±fi
This section shows an example of fd = 154.45 MHz, fs = fd + 2 fi. fi = 10.7 MHz to explain the measurement
procedure.
(1) Setup
Fig. 5-4. Measuring Spurious Sensitivity
MG3641A/MG3642A
DA FM RX DL LM
(154.45MHz)
Pseudo-
antenna
FM
receiver
Standard
pseudo-load
Level
meter