As the demand for faster communications across consumer and commercial devices continues to increase, operating frequencies of RF devices are being pushed higher and higher. This creates a number of challenges for RF device designers as filter size must be reduced to compensate for smaller device sizes and shorter wavelengths while also maintaining high levels of performance.
While surface mount technology (SMT), and in particular microstrip implementations, are an excellent option to meet these demands, it is important to note that not every SMT microstrip filter is created equal. There are a variety of choices to discuss with your filter supplier, such as substrate type, plating technology, and topology, that can dramatically reduce the size and increase the performance of an SMT microstrip filter. One particular choice that Knowles Precision Devices has guided customers through for decades is the decision to use thin film for these filters.
At a high-level, thin film is a layer of material used to fabricate electronic components that generally ranges from fractions of a nanometer to several micrometers in thickness. Since circuits constructed with thin film are built using a distributed element structure created lithographically on a ceramic substrate, this brings the following advantages over other filter development techniques such as printing on PCBs:
- High-precision patterning
- Tight tolerance filter structures with less part-to-part variation and lower loss
- The ability to develop components that are much more compact