Very compact transformer-coupled balun-integrated bandpass filter using integrated passive device technology on glass substrate

This paper presents a transformer-coupled resonator structure to integrate a balun into a bandpass filter using integrated passive device technology on glass substrate. The use of the transformer not only greatly reduces the size of the bandpass filter, but also easily provides the coupling to the balanced output ports. In addition, the tapped feed-lines are used to obtain a good impedance match at all ports, and create extra transmission zeros to enhance the desired stopband rejection. The presented balun-integrated bandpass filter has an overall smaller area and lower insertion loss than the separate designs, showing a great potential to be embedded in a glass carrier for wireless 3D packaging and integration.