A uniform reference line based differential phase shifter with wide phase range and wide bandwidth

To implement the multi-way phase shifting maintaining the compact size and simplicity in structure, the uniform reference line concept was proposed for the differential phase shifter. However, the performance in bandwidth and phase range deteriorates with the additional requirements considered. To solve this problem, a quarter wavelength coupled line section loaded with open/short stubs is proposed as the basic element to implement the main line and also reference line. According to the theoretical analysis on this basic element, the loading stubs can be used to control the phase shift and also the phase slope of the basic element without affecting the amplitude property. With the predetermined parameters of the uniform reference line, only two parameters are required for the implementation of different differential phase shifts. This demonstrates the high simplicity of the proposed structure. For demonstration, an eight-way differential phase shifter operating at 3.5 GHz was implemented using the vertically installed planar structure. The prototype was further fabricated and measured. Good agreement between simulation and measurement can be observed. The implemented phase shifter can provide a wide range of phase shifting values from 45° to 315° with reference to the uniform reference line over a relative bandwidth of 62.3%.