With the development of Internet of Things (IoT), which is one of the national development strategies, ultra-wideband (UWB) technology has developed rapidly for the application of the indoor accurate positioning. The radio frequency (RF) and microwave devices are the vital components of the UWB system for realizing the transmitting and receiving functions, whereas the wideband and ultra-wideband design of these components is still a great challenge. With the supports from the National Natural Science Foundation of China (NSFC), the Macao Science and Technology Development Fund (FDCT), and the Multi-Year Research Grant of University of Macau, this research project was proceeded on the field of microwave technique and it has focused on the study of the resonant elements and circuits of RF and microwave systems. In this research, the multi-mode wideband transmission and the multi-mode phase shift theories have been firstly proposed in the world. Furthermore, a series of multi-mode filter, impedance transformer and phase shifter theories have been evolved respectively with synthetic design methods and techniques. These theories have been verified scientifically by the novel wideband/ultra-wideband RF/microwave circuits developed for UWB devices in the IoT. Through this research, 80 international SCI journal papers have been published in total, in which 64 are published in Institute of Electrical and Electronics Engineers (IEEE) journals. Moreover, 30 papers were published in the IEEE Transactions on Microwave Theory and Techniques, which has the highest impact factor (IF) in the field. The results of this project not only have attracted great attentions and gained lots of citations in many relevant fields worldwide, but also have made Macao’s significant contributions to the major global scientific and technological research and development.

Fig 1 Wideband phase characteristics of multi-mode resonator

Fig 2 Multi-layer wideband/ultra-wideband filters based on multi-mode slot-line resonator