Chapter 2 273
Performance Verification Tests
32. Spurious Responses: Agilent E4404B, E4405B, E4407B, and E4408B
32. Spurious Responses: Agilent E4404B,
E4405B, E4407B, and E4408B
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.
A power meter, power sensor, and power splitter are used to
characterize the frequency response of the analyzer so this uncertainty
can be eliminated.
For example, if the specification states that with −30 dBm at the input
mixer, the distortion products should be suppressed by >75 dBc, the
equivalent second harmonic intercept (SHI) is >45dBm (−30 dBm
+ 75 dBc). Measuring with −15 dBm at the mixer and verifying the
distortion products suppressed by >60 dBc also ensures the SHI is >45
dBm (−15 dBm + 60 dBc).
For third order intermodulation distortion, two signals are combined in
a directional bridge or directional coupler 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
>75 dBc, which yields a third order intercept of >7.5 dBm (−30 dBm +
(75 dBc/2)). Measuring with −20 dBm at the mixer and verifying the
distortion products are suppressed by >55 dBc, the equivalent TOI is
also >7.5 dBm (−20 dBm + (55 dBc/2)).
There are no related adjustment procedures for this performance test.
Equipment Required
Synthesized sweeper (2 required)
Power meter, dual channel
Microwave power sensor
Microwave power splitter
Directional bridge
Directional coupler
300 MHz low pass filter
1 GHz low pass filter