Installation guide

Troubleshooting
Block Descriptions for Option UNJ and Option 506
1-140
pin diodes are biased off and on thus providing maximum or minimum attenuation. This causes the RF signal
to pulse on and off. For narrow pulse widths, the ALC is opened. To maintain power level accuracy, a
Power Search routine may be used through the front panel. The Power Search routine shuts down the
modulation, momentarily closes the ALC loop, and levels. The ALC is then opened up and the modulation is
turned back on.
The I/Q modulator is also located on the A13 Output and may be switched in or out of the RF path. Baseband
modulation for the I/Q modulator is provided by the A10 I/Q Multiplexer. User selectable low pass filtering
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 to minimize offset. When I/Q modulation is
enabled, the pre-level bias for the A16 Frac-N is provided by the I/Q modulator.
A14 Extended Frequency Output (Option 506)
Option 506 extends the output frequency from 4 GHz to 6 GHz by adding a second output board. For CW and
modulated signals 4 GHz and above, the A14 Extended Frequency Output is used. The board has the same
modulation capability as the A13 Output and the baseband modulation signals are routed to both boards.
The A13 Output and A14 Extended Frequency Output are almost identical with the following differences:
• The YO signal on the A21 YTO Driver is coupled off and routed to the input of the A14 Extended
Frequency Output.
• Having the YO bypass the A16 Frac-N, pre-leveling occurs on the A14 Extended Frequency Output.
• The pre-level circuit is prior to the I/Q modulator.
• Unlike the A13 Output, the I/Q modulator on the A14 Extended Frequency Output does not have a bypass
path. The modulator is biased off for CW operation.
• The A14 Extended Frequency Output doesn't contain a heterodyne circuit; since this circuit is only used
for frequencies below 250 MHz, the heterodyne circuit on the A13 Output is used.
• The A13 Output, 250 kHz to 4 GHz, is routed to the A14 Extended Frequency Output which contains a
switch that routes either the A13 Output or the A14 Extended Frequency Output to the optional
AT1 Attenuator and to the RF Output connector.
AT1 Electronic Attenuator (Option 501, 502, 503, 504 or Option UNJ)
with A28 Reverse Power Protection (Option 501, 502, 503, 504 or Option UNJ)
or AT1 High-Power Mechanical Attenuator (Option UNB)
with A29 DC Blocking Capacitor (Option 506)
There are two different attenuator modules available. A high-speed, solid state, 130 dB electronic attenuator
is available for signal generators with Option 501, 502, 503, 504 and Option UNJ. Signal generators with
Options 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 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 incorporated internally to the attenuator module circuitry.
The mechanical attenuator has the RPP circuit as an external module with used with Option 501, 502, 503,
504 and Option UNJ signal generators; the RPP is externally attached to the mechanical attenuator. Signal
generators with Option 506 do not use this same RPP because the frequency range of the RPP is limited to
4GHz.