MEMtronics Integrated Filters

MEMtronics’ filters are designed to achieve the lowest loss possible using a 3-D, integrated waveguide technology. The gold metallization has the lowest conductor losses possible with thin-film deposition, while the substrate incorporates ultra-stable fused silica with unmatched low loss tangents at microwave and millimeter-wave frequencies. Depending on the configuration and layout, our filters embody loss factors ranging from 400 to over 1000 at X-band frequencies and above. These high unloaded quality factors (a measure of filter performance) provide the lowest possible insertion loss, sharpest passband-stopband roll-off, and ensure high rejection at frequencies above and below the passband.

For comparison, stripline and microstrip filters are readily available and usually built not only by multiple filter companies, but internally by many system integrators. With suitable design choices, these parts are often small and lightweight, and can be inexpensively produced in-house, at a myriad of printed circuit board shops or thin-film providers. However, the performance achievable with these parts tends to be low, with unloaded quality factors in the range of 100-200. This means the resulting RF performance is low, often less than desirable.

The graph below shows the impact of building a microwave or millimeter-wave filter with a low-quality factor (rounded frequency response, poorly defined return loss poles) and that of a higher quality factor (sharper rejection rolloff, better return loss and return loss definition).

Alternatively, the highest performing microwave or mmW filters tend to be built with metal waveguide. These filters use a solid metal housing, machined with waveguide cavities, to achieve the ultimate in low-loss, with unloaded quality factors of 1000 or even higher. However, manufacturing these filters requires complex metal machining, and the final performance is achieved by adjusting large numbers of adjustment screws throughout the metal housing. The complex manufacturing and hand-adjustment of these parts causes the final parts to have a comparatively high cost. In addition, the metal construction of these filters requires significant size and weight.

MEMtronics’ integrated filter technology occupies a position in the middle of the “size and performance gap” achieved by these two filter technologies. MEMtronics uses a substrate integrated waveguide technology (SIW) which is far smaller than traditional waveguide technology and achieves a performance far more than that achievable with printed stripline filters.

MEMtronics filters small size, combined with semiconductor batch processing methods, produces filters built with computer automation to achieve the best performance value. This achieves a “sweet spot” in filter technology – high performance, small size, and attractive cost. In summary, the advantages of MEMtronics’ integrated waveguide technology are compact, high performance, and a reasonable cost for meeting difficult filter requirements.