ADL5375-05 for operation between 300 and 400 MHz

Document created by analog-archivist Employee on Feb 23, 2016Last modified by analog-archivist Employee on Aug 10, 2016
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We have a need for an IQ modulator in a new design that will operate over the
range 300 – 3000 MHz.  Our two options are currently the LTC5588-1 from Linear
Tech and the ADL5375-05. 
 
The ADL5375-05 is only spec’d down to 400 MHz whereas the LT part is spec’d
down to 200.  However, the output level of the ADL5375-05 appears to be much
more consistent over frequency that the LT part and, with the exception of the
lower frequency limit, is our preferred option.  Is it possible for you to send
me any useful information on the ADL5375-05 that might shed some light on its
operation below 400 MHz?  Operation down to 380 MHz is essential; operation
down to 300 MHz is our target.
 
In particular we are interested in understanding how its output level (for 1Vpp
input), OP1dB and, if known, its IQ phase and amplitude error degrade below 400
MHz.  Output impedance information for this frequency range would also be
useful.
 
Assuming the main problem is that IQ phase and amplitude error will increase
below 400 MHz, is it likely that we will be able to compensate for this by
calibrating the device and applying suitable IQ phase and amplitude adjustments
to the digital baseband signal?

 

The limitation at operating frequency comes from the limitation in generating
accurate quadrature LO signal. So operating ADL5375 at lower frequencies is
impractical because the sideband starts to fall apart at 400 MHz (green circle
area on Figure 11 attached). If you can  apply an LO of 400 MHz along with a
complex IF of 100 MHz, this would yield a single sideband output (a complex IF)
at 300 MHz. Since the LO quadrature splitter is seeing 400 MHz, sideband
suppression should be ok. You can optimize sideband suppression through phase
and amplitude adjustment in analog or digital domain. Most of our customers do
it at DAC like AD9122, AD9142. Unfortunately, we don’t have performance data
below 400MHz.

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