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Genesys S/Filter Software Directly Synthesizes Filters with Arbitrary Transmission Zero Placement White Paper The Agilent Genesys S/Filter synthesis program accepts design specifications from the user and directly synthe- sizes arbitrary custom filter schematic solutions. Beyond `Look-up' design approach Many electronic circuit synthesis programs today use a "look-up" approach to design. This technique involves fit- ting a preexisting schematic to the user's design criteria. Over the years, hundreds of designs have been calculated, and these designs can be frequency-and impedance-scaled to fit many different scenarios. This technique usually works well -- unless an engineer needs a slightly different topology than the existing ones, or when a finite transmis- sion zero needs to be added to an existing schematic to notch-out an unwanted frequency. In the past, engineers would often take a preexisting design, add some custom- izing elements to it and launch a linear optimizer to recover the desired network response. This approach requires more of the engineer's time, and the engineer must often settle for a nonoptimal response. Genesys S/Filter synthesis program directly synthesizes schematic solutions based on user input. Direct synthesis A filter's transfer function can be represented as a ratio of S/Filter uses a technique called direct synthesis that sums of products, or as a ratio of products of sums: does not suffer from these weaknesses. Contrary to the "look-up" approach described above, direct synthesis takes the user's design criteria, forms a purely mathematical representation -- a transfer function -- and extracts a schematic. Figure 1. Solutions for the Chebyshev bandpass example Figure 2. Solutions for the Chebyshev bandpass example with series elements first with shunt elements first Using the products-of-sums representation, the equivalent S/Filter extracts a permutation in order from left to right filter network can be obtained by extracting one product at (from the source to the load). The six permutations for a time, where each successive product represents some the Chebyshev bandpass example correspond to the six combination of circuit elements. S/Filter adds functionality schematics shown in Figure 1, when using the "series ele- over existing direct synthesis programs by automating the ment first" option. The schematics shown in Figures 1 and element extraction process and by providing high level