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July 21, 2021

Two New Solutions for RF/Microwave Filter Design

Engineers with filter design skills are in demand. 5G development is driving the need for more filter designs in newer frequency bands and new topologies across an ever-increasing number of products and equipment, resulting in the need for more engineers to develop filter design skills. However, high-performance microwave and millimeter wave filter design has traditionally required highly experienced, specialist engineers. Due to the high Q nature and sensitivity of radio frequency (RF) filters, the design and tuning process can be tedious. It’s enough to force some engineers to take shortcuts and compromise design performance to meet schedule demands, which can also lead to design failures in the prototyping and testing phases.

To help address these needs in filter design, Ansys is introducing two new tools for RF/microwave filter design and analysis. Both can save weeks of design and test time for new filter development. These tools allow less-experienced engineers to be successful filter designers. In conjunction with Ansys multiphysics analysis, first pass success is assured.

The Ansys Nuhertz FilterSolutions “filter quick” synthesis screen

Faster Filter Design With Nuhertz FilterSolutions

The first new tool is Ansys Nuhertz FilterSolutions, which dramatically speeds up the design of lumped element (surface mount) and planar filters. A variety of standard designs and a library of vendor components is available for lumped element designs for instant prediction of circuit performance.

For planar filters, Nuhertz FilterSolutions offers a list of geometries relevant to the type of filter chosen and instantly predicts the filter response as the user selects each one. The planar geometry is generated, and the overall size of the filter is predicted automatically. Nuhertz frequency response predictions are built on models derived from finite element solutions of the components of the filter. With a single button click, the full filter geometry can be exported to Ansys HFSS for a high-fidelity prediction and optimization of filter performance.

Finally, Nuhertz FilterSolutions also include synthesis tools for active, switched capacitor and digital filters. The netlist of active filters can be exported in SPICE format. The digital filter synthesis module can export C-code for the generated filter.

Geometry of a low pass filter in Ansys HFSS, generated by Ansys Nuhertz FilterSolutions

SynMatrix Optimization Sets it Apart

The second tool is offered by the Ansys partner company SynMatrix. The SynMatrix solution offers arbitrary topology filter synthesis, analysis and optimization. It is an excellent tool for cavity, waveguide and ceramic filters. The tool supports synthesis of diplexer/triplexers as well as multiband filters.

SynMatrix Synthesis of a filter response and coupling matrix

It includes sensitivity, power handling, dispersion and coupling matrix calculation from a given touchstone file (.s2p). The touchstone file can be from a network analyzer or from Ansys HFSS. The optimization capability is what really sets SynMatrix apart. It interfaces with HFSS to take a roughly tuned filter model and adjusts the physical parameters until the model is properly tuned. It also interfaces with a network analyzer to guide filter tuning on the bench. The utility of a completely tuned filter model to do accurate prediction of tuning range, power handling and sensitivity cannot be over-emphasized. Having an accurate and complete 3D model can save costly prototyping and rework later in the design cycle.

Complementary Filter Design Tools

A common question that comes up is which solution is better. In fact, the Nuhertz and SynMatrix tools are quite complementary. The Nuhertz FilterSolutions is recommended for planer and surface mount (lumped element) filter designs. The SynMatrix tool is better suited for cavity filter design and where flexible filter topologies are required. Furthermore, SynMatrix can extend planar distributed filter designs synthesized through Nuhertz to drive additional AI-based optimization of these filter designs.

SynMatrix Automated Tuning shows error levels and optimization progress


Together with other unique 3D electromagnetic simulation technologies in HFSS, such as analytical derivatives and automatic adaptive meshing, these two filter solutions are making RF and microwave filter design a much smoother process that is accessible to more engineers.

To learn more about these RF and microwave filter design solutions, register for the webinar: 2021 R2 - Introducing New Ansys Solutions for RF/Microwave Filter Design

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