Synthesizing and Optimizing a Hairpin Bandpass Filter with AWR Tools App Note

AWR published a new application note about the synthesis and design of complex filters. The app note uses a hairpin bandpass filter to illustrate how AWR’s iFilter synthesis software in conjunction with Microwave Office high-frequency design software and AXIEM 3D planar electromagnetic (EM) solver can help designers create filters that conform to specific manufacturing constraints and costs. The title of the paper is Synthesizing and Optimizing a Hairpin Bandpass Filter with AWR Tools.

Overview
Like all RF and microwave components, a differential filter design will remain only a simulation exercise if it is not created with its manufacturing process in mind. That is, the tight dimensional tolerances required to meet a set of performance goals must be within the capabilities of the filter’s manufacturing process in order to realize a reliable, repeatable filer. Geometries that are difficult to manufacture, such as very wide lines with very narrow gaps or very narrow lines with very wide gaps, are typically accompanied by extreme resonator impedance swings. A filter synthesis tool must be able to automatically manage these impedances using analytical and empirical techniques (such as Norton and Kuroda transforms, and m-derived and constant-k end sections) to mitigate extreme impedances and produce geometries that can be easily realized. A hairpin bandpass filter with a target center frequency of 5.8 GHz will be used in this application note as an example to illustrate how this can be accomplished using AWR’s Microwave Office software with iFilter technology to synthesize the structure, and then AWR’s AXIEM 3D planar electromagnetic (EM) solver to validate it.

Conclusion
Filtering is becoming ever more important in wireless network deployments at frequencies also occupied by other services, for IEEE 802.11n WiFi in the 5 GHz band, and in the upcoming services that will operate in the new 700 MHz allocations, among others. Consequently, in order to reduce the potential for interference, the ability to rapidly and accurately produce filters with high levels of rejection and other desirable characteristics is critical. Filter synthesis tools such as AWR’s iFilter software were specifically developed to enable designers to quickly and easily create filters that incorporate features to ensure they conform to specific manufacturing constraints and costs. While a distributed-element filter was used in this application example, iFilter is equally adept at handling lumped-element designs as well.

More info: Synthesizing and Optimizing a Hairpin Bandpass Filter with AWR Tools (pdf)