Installation guide

Troubleshooting
Block Descriptions for Option 501, 502, 503, 504
1-124
may be applied to the baseband I and Q signals. The user may also perform a front panel I/Q calibration. The
calibration doesn’t require any external stimulus and will minimize quadrature and gain errors. A portion of
the I and Q signals are fed back to the A10 I/Q Multiplexer which minimize offset. When I/Q modulation is
enabled, the pre-level bias for the A17 Synthesizer (Option 501, 502, 503, 504) is provided by the I/Q
modulator.
AT1 Electronic Attenuator (Option 501, 502, 503, 504 or Option UNJ)
or AT1 High-Power Mechanical Attenuator (Option UNB)
with A28 Reverse Power Protection (Option 501, 502, 503, 504 or Option UNJ)
There are two different attenuator modules available. A standard instrument has a high-speed solid state
130 dB electronic attenuator. Option UNB and Option 506 have a 135 dB mechanical attenuator. The
mechanical attenuator is standard hardware for Option 506. Both attenuators step in 5 dB increments. When
the attenuator changes values, the new attenuation section is switched into the RF path prior to switching
the unused attenuator section out. This prevents damage to sensitive devices under test due to high power
being applied. Attenuation sections are switched into operation in a specific order to achieve the best input
and output matching for each level of attenuation. The attenuator modules are field replaceable, but not field
repairable.
The standard electronic attenuator has the RPP circuitry incorporated internally with the attenuator module
circuitry. In contrast, the mechanical attenuator has the A28 Reverse Power Protection
(Option 501, 502, 503, 504 or Option UNJ) circuit as an external module that is attached to the attenuator.
The RPP circuitry prevents instrument damage when power is mistakenly applied to the instrument’s
RF output. Operationally, the RPP circuitry opens an RF relay when 1 Watt of energy is sensed on the
RF output. Repeated high levels of reverse power degrade the performance of the RPP or completely bypass
the open RF relay. The RPP may be reset through front panel softkeys.