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Chapter 2 255
Performance Verification Tests
30. Spurious Responses: Agilent E4401B and E4411B
30. Spurious Responses: Agilent E4401B and
E4411B
This test is performed in two parts. Part 1 measures third order
intermodulation distortion. Part 2 measures second harmonic
distortion.
To test second harmonic distortion, a low pass filter is used to filter the
source output, ensuring that harmonics read by the analyzer are
internally generated and not coming from the source. To measure the
distortion products, the power at the mixer is set 25 dB higher than
specified.
For example, if the specification states that with
−40 dBm at the input
mixer, the distortion products should be suppressed by >75 dBc, the
equivalent second harmonic intercept (SHI) is >35 dBm(
−40 dBm +
75 dBc). Measuring with
−15 dBm at the mixer and verifying the
distortion products suppressed by >50 dBc also ensures the SHI is
>35 dBm (
−15 dBm + 50 dBc).
For third order intermodulation distortion, two signals are combined in
a directional bridge to provide isolation. These two signals are applied
to the analyzer input. The power level of the two signals is several dB
higher than specified, so the distortion products should be suppressed
by less than the amount specified. In this manner, the equivalent third
order intercept (TOI) is measured.
For example, if the specification states that with two
−30 dBm signals
at the input mixer, the distortion products should be suppressed by
>80 dBc, which yields a third order intercept of >10 dBm (
−30 dBm
+ (80 dBc/2)). Measuring with
−20 dBm at the mixer and verifying the
distortion products are suppressed by >60 dBc, the equivalent TOI is
also >10 dBm (
−20 dBm + (60 dBc/2)).
There are no related adjustment procedures for this performance test.
Equipment Required
Synthesized signal generator
Synthesized sweeper
Power meter, dual channel
RF power sensor
Power splitter
Directional bridge
50 MHz low pass filter
Cable, BNC, 120-cm
Cable, APC 3.5, 91-cm (2 required)
Adapter, Type-N (m) to APC 3.5 (f) (3 required)
Adapter, Type-N (m) to SMA (m)