FireFox Synthesizer User Manual
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© 2006 Jackson-Labs
1.6.4 DDS Synthesizer
The FireFox variable output frequency is generated by a Direct Digital Synthesizer with 48bit
resolution.
Figure 1.5
shows the block diagram of the FireFox synthesizer, with the DDS module
visible on the upper part of the image. The DDS generates sine wave signals ranging from 10µHz to
410MHz using a 10bit DAC and a 1GHz reference input. A 400MHz low pass reconstruction filter is
used at the output of the DDS to reduce aliasing and improve spurious performance. The output
signal of the DDS drives a PLL module that multiplies the output frequency of the DDS up to
1.64GHz for output signals above 400MHz. The DDS phase accumulator may be controlled by the
user via the keypad to shift the output signal phase arbitrarily from -180 to +180 degrees with 0.1
degree resolution.
1.6.5 RF Output Buffer
The FireFox synthesizer has multiple digital outputs and one analog RF signal output. This RF output
is factory-calibrated and leveled, and the amplitude is adjustable via the keypad. The output is a pure
sine wave with low phase noise, and low spurs and harmonics. A buffer and variable-gain amplifier
allow signal levels above +10dbm typ. with a control range down to -40dbm typ. The user can either
select a calibrated leveled output signal (indicated in dBm) or a relative output level (0-100%) via the
keypad. The maximum relative output level varies with frequency. The RF output can be periodically
calibrated using an Agilent E4418B or E4419B power meter and an Agilent 8482A power sensor
connected to the FireFox synthesizer. Calibration is fully automatic, and can include user cabling and
amplifiers etc. to compensate for cable losses.
Figure 1.6 FireFox Desktop Unit Rear Panel
Summary of Contents for FireFox
Page 1: ...FireFox Synthesizer User Manual Document 0012008 Version 004 Date 10 April 2008...
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