52 / 84
Since the market release of Mini-
Circuits’ X-Series reflectionless filters,
much testing has been conducted
to evaluatethe benefits of these
revolutionary products in comparison
to conventional filters. While
conventional filters are fully reflective
in the stopband, reflectionless
filters use a novel, patented filter
topology to absorb and terminate
stopband signals internally, avoiding
many known systemic problems
caused by reflections in the signal
chain. This new capability makes
reflectionless filters suitable for a
variety of applications beyond those
typically incorporating conventional
filters. One of the most prevalent
and practical of these applications is
filtering at mixer inputs and outputs.
Previous testing, which Mini-
Circuits has published, established
that reflectionless filters virtually
eliminate signal reflections between
the filter and the mixer output as
compared to conventional filters.The
expected effect of this reduction is
an overall improvement is system
linearity and dynamic range, but this
was inferred in previous reports.
This article will present new test
results
demonstrating
overall
improvement in system IP3 when
reflectionless filters are used on
mixer inputs and outputs in both
downconverter and upconverter
configurations in comparison to
conventional lumped element filters
and LTCC filters. The results also
expand on previous comparisons
by testing numerous mixer-filter
combinations and showing consistent
performance improvement when
reflectionless filters are used.
Up-Conversion Test
Setup
Two-tone intermodulation tests
were performed in up-converter
configuration using diode based
mixers with a variety of filters on
the IF input and RF output ports
for comparison. The test was
also performed without filters to
provide a reference.Third order
intermodulation
measurements
were made withIF input of 150 MHz
and two-tone spacing of 1 MHz, and
RF outputs of 800 MHz and 2200
MHz. The test setup is illustrated in
Figure 1, and the test conditions are
summarized in Table 1.
Each of the two mixers was tested
Reflectionless Filters Improve System IP3
in Up-converter and Down-converter
Configurations
Martina Yan, Mini-Circuits
Test & Measurement
Special Edition
52 l New-Tech Magazine Europe