The downconverter design is partitioned into blocks for amplification, including filtering, mixers, oscillators, buffer ampli-
fiers, digital divider, and phase-locked loop (PLL) dynamics (Figure 3). Each block can be represented in simulation by a
high-level behavioral model or detailed circuit level sub-circuit as that information becomes available to the design team
integrating the individual radio blocks. Since it is often the case that each block will be developed by a different designer, it
is critical that the module flow supports the analysis of all these designs assembled into a single project.
At the downconverter subsystem level, the performance was simulated using Cadence AWR Visual System Simulator (VSS)
software. The AWR VSS behavioral and measured circuit-based models enable designers to perform budget, spectral, and
time-domain analyses to aid in all phases of module development, from architectural studies to design verification. Cadence
AWR Microwave Office software was used to develop the individual radio blocks in the downconverter, including all amplifier,
filter, and mixer designs.
Figure 3: Top-level downconverter symbol in schematic editor and individual downconverter radio blocks defined with behavioral models.
Downconverter Module Design
Once all the radio blocks are designed at the circuit level (not
discussed are the passive coupler, DRO buffer, and divider),
the entire downconverter can be assembled from these
subcircuits into a single hierarchy for analysis, as shown in
Figure 4. The electrical specification of the module requires
conversion of microwave signals to a lower IF range, which
can be investigated with circuit-level accuracy.
Figure 4: Complete downconverter module design with system-
level behavioral models replaced with circuit-based models.
A final step in the overall design and verification of the
downconverter prior to manufacturing may include the
analysis of any potential interaction between the planar
subcircuits and the 3D enclosure (housing). Enclosure
resonances (modes) can be simulated using Cadence AWR
Analyst™ EM software. The mechanical design was imported
and analyzed with the Analyst Eigenmode solver, which can
plot the fields and surface currents on the enclosure to help
designers visualize potential trouble areas.
Conclusion
RF/microwave modules integrate diverse technologies to
address cost and performance concerns associated with
low- to medium-volume wireless applications. This white
paper has demonstrated the combined use of system-level
analysis for design partitioning and component specifi-
cation along with circuit-level simulation and EM analysis in
the development of a complete hybrid downconverter.
To read the white paper in its entirety , visit
awr.com/resource-library/design-complete-
rf-downconverter-module-test-equipment.
12 www.cadence.com/go/awr
