RF Microtech

RF Microtech Develops Complex UWB Filter in Record Time


Company Profile

RF Microtech, Perugia, Italy, is a service company developing custom RF and microwave products for industries and system integrators. The company covers all areas of RF and microwave technology and offers innovative solutions for the most demanding applications in the areas telecommunication, aerospace, defense and security, safety, medical, manufacturing industry, logistics, and localization. 

RF Microtech was founded in 2007 as a spin-off out of the University of Perugia by Professor Roberto Sorrentino and his group of former students in the microwave engineering laboratory of the Department of Electronic and Information Engineering.

The Design Challenge

Expo Milano 2015 was a universal exposition that hosted over five thousand events in six months. The organizers had contracted with several mobile service providers to deploy stations throughout the expo area to provide complete mobile service coverage for the event. In addition, Italian government security services relied on mobile base stations strategically placed throughout the expo to ensure communications for the event, including the public safety network. However, the lobe of one of the mobile service antennas directly interfered with the communication signals of a critical security control base station and the issue had to be resolved immediately as the expo was opening in less than a month. RF Microtech was asked to provide a validated full-wave electromagnetic (EM) simulation of a 2-port ultra-wideband (UWB) filter that could reject all five mobile service bands with greater than 35 dB of rejection. Furthermore, the filter had to ensure 80 MHz to 6 GHz wide-band transmission with insertion losses less than 2 dB RF Microtech’s client, H3G, also required that the device fit within a 1x1x0.2 meter enclosure, while still providing acceptable levels of coexistence to 6 GHz without signal degradation. The validated EM simulation had to be delivered within two weeks and the complete deployable device by the time the expo opened.

The Solution

The RF Microtech design team immediately went to work developing a circuit model of five independent notched-band filters (NBFs) cascaded along a transmission line.
The team chose NI AWR Design Environment, specifically Microwave Office circuit design software, for this time-critical project. Each independent filter was designed as a 4th or 5th order NBF, composed of several cascaded stages of N shunt resonators. The individual filter specifications required that the filter resonators’ high unloaded Qs be > 1000, with the additional challenge of having no spurious modes under 6 GHz. Each of the transmission line and filter sections were then implemented in ANSYS HFSS full-wave electromagnetic (EM) analysis tool. The S11 and S21 results corresponded well with the initial circuit simulation. 

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