Kengo Onaka

28 GHz wideband filter using quartz crystal waveguide for massive MIMO antenna unit

Massive MIMO technology and mm-wave band radio communication are effective solution of a high data rate for 5G. This paper presents a novel 28GHz wideband filter for those antenna units. To realize a wide fractional bandwidth of 10%, a new terminal configuration of “Y-shaped” structure is proposed. A TEM-TE mode transition function using the new structure was analyzed, and the shape was optimized. Applying the new terminal structure to an 8-pole with 2 trap quartz waveguide filter, high performances such as very low loss of 1.2 dB, wide relative passband of 10.4% and high attenuation of more than 50dB were obtained with a small size and SMD structure.

A novel switchable SAW Duplexer for band 28

Band 28 has wide bandwidth of 45MHz and narrow duplex gap of 10MHz in 700MHz band, and since digital terrestrial TV channels in some countries are overlapped with lower frequency range of the uplink band, two types of duplexer which have slightly shifted passbands need to be used. This paper describes a novel switchable SAW duplexer which can cover both bands in one duplexer. By using a filter design technique with unique switching circuit, and wideband and low temperature drift SAW resonator technology, high performance such as 2.6/3.0dB insertion loss and 55dB isolation have been achieved, in addition to more than 13/16dB near point attenuation only 5/8MHz apart from the passband edge. The developed switchable duplexer can lead the reduction of 40% in mounting area on RF front-end circuit of mobile terminals.