Content for  TR 38.877  Word version:  18.1.0

The following discusses a use case of diplexer in FR2 multiband RIB architecture. To support across the different frequency group with dual input stacked patch multi-band antenna and multi-band PA, a diplexer is useful to divide each frequency group's signals as Figure 5.3.5-1. To implement a diplexer between multi-band antenna and PA, diplexer should be smaller than antenna elements interval of phased array.

The following simulation result shows the feasibility of a diplexer and its performance impact based on the above condition. Figure 5.3.5-2 is for a diplexer for 28+39GHz (n257/n261, n260) band combination. 1dB insertion loss and >50dB attenuation are achieved.

The dimension of this diplexer is 4.0 mm x 1.8 mm or less in LTCC substrate, and dielectric constant of this substrate is 6.4, Q value is 200. Most of the current base station supports dual polarization, so the required area to implement a diplexer should be doubled and it becomes 4.0mm x 3.6mm. In case of 28+39GHz combination, 0.5λ at the centre frequency is 4.51mm. So if antenna element interval is 0.5λ or larger, it is possible to implement diplexer below each antenna elements. For other multi-band combinations such as 26+40GHz (n258, n259/n260) and 28+40GHz (n257/n261, n259/n262), the following examples are provided. Over 50dB attenuation is achieved for the all band combinations and their performance impact is around 1dB.