Cross-coupled filters are commonly used for high-frequency, high-performance applications where narrow passbands and steep roll-off are required, for example in telecom base stations and satellites. Cross-couplings (couplings between non-adjacent resonators) can be used to modify the filter transfer function. They are mostly employed for improving the filter selectivity by producing transmission zeroes. Depending on their sign, they can also be employed for improving filter phase linearity.
In traditional filter design, the tuning of the filter and placement of the transmission zeroes required both considerable analytic work to calculate filter coefficients and manual fine-tuning. CoupleFil simplifies the process substantially by automatically calculating the necessary coupling matrix and suggesting filter topologies that match the user’s requirements. These requirements can include multiple pass-bands and arbitrary transmission and reflection zeroes.
Once CoupleFil has synthesized a filter, it can generate a 3D model of the design which can be exported directly into the 3D EM simulation tool CST STUDIO SUITE®. A full 3D simulation can then be carried out to optimize the filter and to allow its performance to be calculated as constructed using a virtual prototype. By combining synthesis and simulations, users can get from specifications to tuned design more quickly, saving both time and money.
“Many of InnoDev’s customers are also CST customers, and will benefit from the integration of CoupleFil into CST’s software range,” said Rony Füglistaller, cofounder ofInnoDev GmbH. “We look forward to working as part of the CST team in the future development of CoupleFil, and will continue to offer customer-specific software and hardware solutions.”
CST has traditionally been strong in the microwave and RF market, and CST STUDIO SUITE is used by engineers to design and analyze a very wide range of high-frequency components and systems. In recent years, CST has focused on strengthening its offering for filters in particular, with the introduction of optimization techniques especially well-suited to filter tuning and the integration of FilterDesigner 2D into CST STUDIO SUITE. The addition of CoupleFil to CST’s portfolio further increases their presence in this application area.
“Our customers demand strong synergy between synthesis and simulation tools,” said Peter Thoma, Managing Director R&D at CST. “We’ve had very positive feedback about our design tools for antennas, arrays and planar filters, and the integration of CoupleFil into CST STUDIO SUITE workflows is sure to give customers working on cross-coupled filters the same advantage.”
