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MEMtronics Filter Innovation Technology

As the electromagnetic environment becomes more populated, frequency-agility and narrow operating bandwidths are becoming highly desirable characteristics for bandpass filters in RF front ends. As such, bandpass filters having a high unloaded quality factor (Qu) are a requirement for maintaining low insertion loss and minimum noise figure. In addition, size and cost are also important considerations.

While microstrip or stripline filter technology offers a low cost solution within a small footprint, their unloaded quality factor, Qu, is limited by system losses rendering them inadequate for many applications. When high-selectivity is required, metal waveguide technology is employed. While this technology offers very high unloaded quality factors in the thousands, their size and weight make them prohibitive in many applications. In addition, they are much more costly than their printed circuit counterparts. MEMtronics Filter Innovation Technology (MFIT) address’ the gap between microstrip or stripline and metal waveguide that offers very high quality factors approaching waveguide, with the size and cost advantages of printed circuits.

We are actively engaged in the development of filters for a variety of applications in the electromagnetic spectrum. As demonstration vehicles, we have developed MFIT prototypes in X-band and Ka-band. Custom filters to meet specific user requirements are also possible from 2 GHz through 50 GHz, with passband bandwidths ranging from 0.5% to 10%, in implementations with 2-5 poles of filtering.

Filter platform criteria for our prototype designs is extremely low-loss (performance), planar (size and weight) and a precise, repeatable manufacturing process (cost). To address these criteria, MEMtronics has developed miniature waveguide technology that combines advantages of planar printed circuits that are compact, light, easy to fabricate, flexible, and cost effective while preserving the advantages of conventional metallic waveguides, namely, complete shielding, low-loss, high quality-factor and high power-handling capability.

MEMtronics X-band filters utilize dielectrically-loaded evanescent waveguide cavities built with uni-body construction for the ultimate in small size with excellent loss characteristics. The filters are constructed from quartz for ultra-stable operation over temperature. Evanescent waveguide operates below its cutoff frequency and behaves like a lumped inductor. Evanescent waveguide in concert with a shunt capacitive post forms a cavity resonator. Cavity resonators are coupled via a section of evanescent waveguide (series inductor) forming a waveguide filter.

Photo of MEMtronics X-Band filter

Photo of X-band Filter (Part Number MFITX401)

X-band filter MFITX401 is a 4-pole filter function centered at 11.8 GHz with a 5.1% bandwidth (11.5 - 12.1 GHz), exhibiting a nominal 1.1 dB insertion loss over the passband. Spurious rejection is > 35 dB. Unloaded quality factor is > 450. Performance over temperature is very stable, with Df ~ 3.5 MHz from 25^oC to 125^oC. The small, light weight WG filter chip is 12.0 x 35.3 x 0.76 mm (chip area is 424mm²) and weighs only 0.73 grams.

X-band Filter MFITX401 Insertion and Return Loss

Miniature X-band Filter Data Sheet MFITX402 (pdf)

The MEMtronics Ka-band miniature waveguide filter is designed to be surface mountable for straight forward circuit board interconnect (CPW interfaces) and utilizes dielectrically-loaded propagating waveguide cavities built with uni-body construction for the ultimate in low-loss with a small form factor. The filter is constructed from quartz for ultra-stable operation over temperature.

Photo of Ka-band Filter

Photo of Ka-band Filter (Part Number MFITKa401)

The Ka-band MFITKa401 filter provides a 4-pole filter function centered at 35.5 GHz with a 1.7% bandwidth (35.2 - 35.8 GHz), exhibiting a nominal 2.3 dB insertion loss and a minimum 14 dB return loss over the passband. Spurious rejection is > 35 dB. Unloaded quality factor ranges from 600 – 800, depending on frequency and configuration. Performance over temperature is very stable, with Df ~ 32 MHz from 25^oC to 125^oC. The small, light weight WG filter chip is 5.9 x 24.4 x 0.76 mm (chip area is 144mm²) and weighs only 0.25 grams.

Ka-band Filter MFITKa401 Insertion and Return Loss

Filter performance at 25^oC (blue), 75^oC (green), and 125^oC (red)

Df/DT ~ -0.32 MHz/^oC
Filter demonstrates excellent temperature stability

MFITKa401 - Ka-band 35.2GHz to 35.8GHz Bandpass Filter (PDF)

Next generation Ka-band filter designs incorporate innovative approaches to reduce circuit loses and increase Qu even further. Achieving high quality factors with low-cost, light weight, small packaged die in a precise and repeatable manufacturing process represent unparalleled performance / cost advantages that are an attractive alternative to competing technologies. Please contact us for the progress of these designs.

If you have microwave or millimeter-wave applications similar to these, please feel free to contact a MEMtronics representative. We are always interested in talking with potential customers and collaborators on how MEMtronics Filter Innovation Technology (MFIT) may benefit their application.

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