A New Class of Components for Simultaneous Power Splitting Over Microwave and Millimeter-Wave Frequency Bands

The co-existence of the microwave and millimeter-wave technologies becomes the inexorable trend of the future wireless communication systems. The corresponding components within the system are required to cover these two frequency bands simultaneously. But the existing dual-/multiband components cannot satisfy this requirement. For the first time, a new class of components are proposed to provide simultaneous power splitting functions at microwave and millimeter-wave frequency bands. To achieve such a large frequency ratio, an effective feeding approach should be proposed to properly route the signal between the input/output ports and the two elements which operate at microwave and millimeter-wave frequency bands respectively. For universality, the popular microstrip line and substrate integrated waveguide (SIW) structures are utilized for the implementation of microwave and millimeter-wave elements, respectively. An aperture coupling mechanism which can suppress the high order mode of the microstrip structure and excite the TE10 mode of the SIW structure at the same time is proposed. A simple transmission model is utilized to explain the working principle along with the theoretical analysis. Based on this novel feeding approach, fourdual-/tri-band components which can achieve a large frequency ratio up to 33.3 were designed, fabricated, and measured. Besides the flexibility in operating frequency, the proposed structure can provide arbitrary coupling coefficients (3-10 dB) and even different functionalities at the two frequency bands, which had not been reported in the literature.