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32 DESIGN007 MAGAZINE I MAY 2018 by John Coonrod ROGERS CORPORATION Millions of cellphones trying to connect voices and download unimaginable numbers of files worldwide point to the inevitability of fifth generation (5G) wireless communications networks. 5G is coming, and it will require the right circuit materials for many different types of high-frequency circuits, including power amplifiers (PAs). 5G represents the latest and greatest in wireless technology, and it will be challenging to design and fabricate, starting with the circuit board materials, because it will operate across many different frequencies, such as 6 GHz and below, as well as at milli- meter-wave frequencies (typically 30 GHz and above). It will also combine network access from terrestrial base stations and orbiting satel- lites. But by careful consideration of mechani- cal and electrical requirements, high-frequency circuit materials can be specified that enable the design and development of 5G PAs no mat- ter the frequency. Ideally, a single circuit material would be a suitable starting point for PAs at all frequen- cies. However, amplifiers at different frequen- cies have different design requirements and are best supported by circuit materials with differ- ent characteristics best suited to the different frequencies. For example, insertion loss or dis- sipation factor can be more or less depend- ing on the type of circuit material. Every cir- cuit material will suffer some amount of loss, which typically increases with increasing fre- quency. The loss performance of a given circuit material may be acceptable within the micro- wave frequencies to be used in 5G networks but not within the millimeter-wave frequency range, where signal power tends to be less with increasing frequencies. The circuit material that provides the low loss needed for high PA gain and output power at microwave frequen- cies may not be the best choice of material for a PA at millimeter-wave frequencies. The design requirements for a key circuit material parameter, dielectric constant (Dk), are much different for microwave frequencies, Making the Most of PCB Materials for 5G Microwave and mmWave Amps