Installation guide

Troubleshooting
Block Descriptions for Option UNJ and Option 506
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Digital Modulation Block Description for All Options
Overview
Digital modulation for all options of signal generators is made from portions of two major assemblies:
• A7 Baseband Generator (Option 001 or Option 002)
• A10 I/Q Multiplexer (Option 501, 502, 503, 504 or Option UNJ)
or A10 I/Q Multiplexer (Option 506)
Together, these assemblies are responsible for generating and routing the baseband signals to the I/Q
modulator located on the A13 Output. The A7 Baseband Generator (Option 001 or Option 002) consists of
data generation, burst control, and symbol building circuitry. The output section of the A7 Baseband
Generator (Option 001 or Option 002) consists of two 16-bit DACs: one for the I signal and one for the
Q signal. The data produced from these I/Q signals is converted to analog, amplified, and filtered before being
routed to the A10 I/Q Multiplexer. The I/Q signals are routed from the A10 I/Q Multiplexer to the
I/Q modulator located on the A13 Output. These I/Q signals are used to modulate the main RF signal that
represents one of the many “Digital Modulation/Communications Standard” formats such as TDMA, CDMA,
W-CDMA, GSM, NADC and others.
A7 Baseband Generator (Option 001 or Option 002)
The A7 Baseband Generator (Option 001 or Option 002) can be used as a Dual Arbitrary Waveform Generator,
a Real Time I/Q Baseband Generator, or a Noise Generator. Waveform personalities can be purchased in
order to generate standard formats. Customer supplied waveforms can also be downloaded into the waveform
memory to generate customized formats.
The I/Q bandwidth is 80 MHz for internally generated I/Q signals and 160 MHz for externally generated
I/Q signals. The A7 Baseband Generator (Option 001 or Option 002) can generate symbol rates of up to
6.25 Msymbol/sec.
• A7 Baseband Generator (Option 001) has 8 Msamples of waveform memory
• A7 Baseband Generator (Option 002) has 32 Msamples of waveform memory
Data is sequenced from waveform memory by the Field Programmable Gate Array block (A1-FPGA), passed
on to the format builder block (A2-FPGA/Modulator/Filter), and finally to the output section. I and Q DACs at
the output convert the digital waveform data to analog. The I and Q output DACs are driven by a sample
clock generated by an on-board VCO. The VCO has a frequency range of 200 to 400 MHz. The 10 MHz
reference signal from the A18 Reference is supplied and used to phase-lock the sample clock signal of the
DACs to the A18 Reference; an external 10 MHz reference signal could also be used.
The Burst Pulse signal from the A7 Baseband Generator (Option 001 or Option 002) goes to the analog
modulation block on the A18 Reference (which is part of the Frequency Synthesis Block) and is used to drive
the pulse modulator located on the A13 Output. The Burst Pulse signal is used by the digital modulation
formats to synchronize the main RF path and ensure maximum on/off level ratio.
The I and Q output signals are the main signals out of the A7 Baseband Generator (Option 001 or Option
002). They are also the digital modulating signals that go to the A10 I/Q Multiplexer which are then routed to
the I/Q modulator on the A13 Output.
A10 I/Q Multiplexer
The A10 I/Q Multiplexer receives I/Q input signals from the A7 Baseband Generator (Option 001 or Option
002), external I/Q inputs signals from the front panel, and an I/Q sense feedback signal from the
I/Q modulator on the A13 Output. The A10 I/Q Multiplexer inverts and routes the I and Q signals to the rear