Microstrip phase inverter using slotted ground

A Phase Inverter (PI) is a device that changes the phase of a signal by 180°. It has been applied many microwave components such as rat-race hybrids [1–2], branch line couplers [3], and bandpass filters [4] to reduce size by changing the 3/4 wavelength line to a 1/4 wavelength PI integrated line, or to widen the bandwidth of the components by using the flat phase properties of the PI. A parallel strip PI [1] and a coplanar stripline (CPS) PI [5] have been used to implement these applications. However, a large proportion of microwave components are implemented on a microstrip line and these PIs are generally not applicable to the conventional components. A PI that is integrated on the microstrip hybrid requires a transition between the microstrip line and CPW [2] that requires complicated structures. This paper proposes a simple microstrip PI using a slotted ground without any complicated transitions.