A device for shifting the phase of an electrical signal includes a first microstrip, a second microstrip, and a ground plate. The first microstrip includes an input terminal and the second microstrip includes an output terminal. The second microstrip is spaced apart from the first microstrip such that a microstrip-to-slot transition region is defined between the first microstrip and the second microstrip. The ground plate includes a ground-plate slot that spans the microstrip-to-slot transition region. The ground plate is coupled with the first microstrip and the second microstrip such that at least one of the first microstrip and the second microstrip are movable relative to each other and to the ground plate to adjust a width of the microstrip-to-slot transition region.