Flexible Wideband Microstrip-Slotline-Microstrip Power Divider and its Application to Antenna Array

In the satellite microwave power transmission (MPT) system, antenna arrays are usually adopted for a higher gain. For the passive wideband antenna array, wideband power dividers are essential when the feed network is constructed. Because the microstrip-slotline coupled power divider could achieve wide bandwidth and compact size at the same time, it becomes a potential candidate for the feed network. However, impedance matching is always needed in the slotline, e.g., the fixed slotline length or the stepped impedance transformation. So, the power divider is not flexible. In this paper, a flexible Microstrip-Slotline-Microstrip (MSM) power divider is presented. When the ratio of the coupling coefficients $n_{1}$ of the microstrip-to-slotline transition (MST) and $n_{2}$ of the slotline-to-microstrip transitions (SMT) is 2, the MST and SMTs could be self-matched respectively. Then no impedance matching is needed anymore in the slotline. Thus, the slotline length can be arbitrarily chosen, and no stepped impedance transformations are needed. This power divider eliminates the drawback limiting the free wire routing for the microstrip-slotline coupled feed network. It could serve as a new kind of feed network, especially be considered when the simple T-junction feed network cannot achieve enough bandwidth. Besides, a wideband Vivaldi array with this feed network is presented.