By Assoc. Prof. Dr. Wong Peng Wen
Mobile wireless communication has seen an explosive growth in the past decades driven mainly by the massive use of smartphones and tablets. In order to meet the increasing demands, a revolutionary 5G networks with unprecedented data speeds are explored. A 5G mobile communication system is expected to support large number of wide area network (WAN) bands, radios, and personal area network (PAN) and FM services. This leads to the innovation for reconfigurable filters in order to replace the large number of fixed frequency filters such that the overall size can be reduced.
UTP has embarked on a few research projects since 2010 that are tailored for future 5G implementation. One of these is a new reconfigurable bandpass filter based on switched delay line which contrasts conventional tunable filters. The approach distinguishes itself through its ability to provide a wide tuning bandwidth, low passband loss and high linearity performance. This technique allows for small size, light weight and fast tuning capability while the changing of filter bandwidth can be reconfigured to perform intelligent management of adjacent interferences.
Another project is a novel miniaturized matched band-stop filter with high rejection level. This filter results in a 50% size reduction compared to the dual-mode ring resonator that has an electrical length of 360°. The filter design is cascaded to achieve dual-band, band-stop filter at center frequencies of 0.99 GHz and 1.04GHz. The benefits and applications of a switchable band-stop to an all-pass filter are envisioned to include general system flexibility, at no cost to the physical space. They allow the receiver to take advantage of the benefits of a band-stop filter centric front end, while dynamically allowing for a mode of operation, which allows signal at all frequencies to be received in low-power environments. For a wide-band 5G system, an electronically switchable band-stop to all pass filters was developed.