Inkjet-printed bandstop filters for interference suppression in multi-standard wireless systems

This paper presents a highly compact inkjet printed microstrip bandstop filter (BSF) for interference suppression in multi-standard wireless applications. The structure is designed with strict specifications for inkjet printing such as the use of the Kapton substrate and its flexible polyimide film. The design was simulated based on Kapton substrate with a thickness of 50µm and dielectric constant of 3.4. The simulated results show a good narrowband response with good stopband attenuation of about 38 dB. When compared to other published BSFs, the proposed structure occupies the least normalized area and best return loss performance up to 10 GHz. This filter is then used to reject interference in a multi-standard wireless transmitter system with suppression of about 30 dB achieved with a great level of noise and spurious response reduction thereby improving the overall performance of the system. This type of filter will be very useful to eliminate undesired signals in next generation 4G LTE-Advanced and 5G mobile networks as well as being very attractive for modern day multi-standard wireless applications such as machine to machine (M2M) communications and internet of things (IoT).