Software Tool Proves its Merit for Filter Design

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To accomplish their design goals, RF/microwave filter designers have various options to choose from in terms of software tools. One such tool is currently offered by WaveCon, which was founded back in 1989. Today, WaveCon’s software can be utilized to design a wide range of filter types, including microstrip, stripline, and round-rod.

WaveCon’s original program is known as Parfil, which can be used to design bandpass, lowpass, highpass, and bandstop filters. In addition to Parfil, WaveCon offers the Elliptic and ProCap design tools. Elliptic is intended to be used for the design of elliptic filters, while ProCap is a nodal analysis program.

As stated, the Parfil tool can be used to design bandpass, lowpass, highpass, and bandstop filters. Figure 1 shows the software’s filter selection menu, with filter types that include Parallel Coupled Half Wave, Interdigital Tapped Input, Combline Tapped Input, Hairpin Coupled Line Input, and many others.

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Microstrip Bandpass Filter Example

As an example, when selecting the Parallel Coupled Half Wave filter type, users are presented with a list of input parameters that includes Transmission Media, Filter Center Frequency, Filter Bandwidth, Ripple, Number of Filter Sections (Poles), and many more (Fig. 2). One simply has to enter the parameters that are needed to satisfy the specific design requirements. Figure 2 shows the input parameters for a microstrip filter with a center frequency of 10 GHz.

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Figure 3 shows the computed results for the specified filter. The lengths and widths of the sections are shown along with the gap separation values. In addition, the even- and odd-mode impedance values are shown in Fig. 3.

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At this stage, users have a number of options at their disposal. For example, the Plot Window menu item includes a number of display options, such as Gain/Return Loss and Gain/Group Delay (Fig. 4). Furthermore, the Tune option allows users to adjust the filter’s response.

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Further Analysis

Of course, a designer may also want to use an electromagnetic (EM) simulator to verify the filter’s performance at this stage in the design process. The results obtained from Parfil could then be incorporated into an EM simulator for performance verification and optimization. In essence, Parfil is effective in terms of obtaining numerical filter values and then viewing results.

The process described is similar for other filter types. For example, Fig. 5 shows the input parameter list when selecting the Interdigital Tapped Input filter type. Users essentially follow the same approach of entering the required parameters for this type of filter.

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In addition to Parfil, WaveCon offers the Elliptic program. This software tool is intended for the design of elliptic filters. Figure 6 shows the program’s filter selection menu, which includes Parallel Coupled Half Wave Elliptic, Interdigital Shorted Line Input Elliptic, Combline Shorted Line Input Elliptic, and several others. A similar list of input parameters is displayed after a filter type is selected.

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In summary, WaveCon’s software is certainly a helpful tool for filter design. While this article focused on the Parfil and Elliptic software programs, the ProCap program also offers its own analysis capabilities. For additional information about any of the company’s offerings , visit its website.