Atec Agilent-81618A - Manual (Page 66)

Performance Tests Performance Tests
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Agilent 81618A/9A and Agilent 81622B/3B/4B/6B/7B/8B User’s Guide, Second Edition
N O T E The nonlinearity of the 81622B is not regularly tested up to the
specified power level of +27 dBm. Instead, limited testing up to
+9 dBm is used to test the electronic circuitry of the 81622B. Above
+9 dBm, the largest contribution to nonlinearity comes from the
absorbing glass filter (which is tested on a sample basis) that does not
change its nonlinearity with time. This way it is guaranteed by design
that testing the 81622B up to +9 dBm ensures specification compliance
up to +27 dBm.