Design and Implementation of Ultra-Wideband Passive High Frequency Phase Shifter with Single Layer Microstrip Structure

In this paper, a method is presented for design and realizing ultra-wideband phase shifter in frequencies beyond 10 GHz with about a hundred percent fractional bandwidth. Its structure is composed of microstrip transmission lines and short circuited stubs. Its combination has advantages, from fabrication and realization viewpoint, over conventional structures that utilize coupled transmission lines and multi-layer structures. With this design and optimization method, it is possible to manufacture phase shifters with arbitrary phase shifts as well as arbitrary input and output impedances. The values of circuit dimensions is obtained using the optimization of least mean square combination of error function. To design phase shifters, a computer program is written which utilizes circuit models of microstrip transmission lines and microwave network relations. Its results are then improved using full-wave electromagnetic softwares to consider parasitic effects of T-junctions. 45 degree phase shifter with 50 ohms input-output impedances is designed, simulated and fabricated. Also, the 90 degree phase shifter was designed and simulated in the case that the input and output impedances be unequal, assuming to be 50 and 75 ohms. By investigation of the results of transmission and reflection coefficients and phase shifts obtained from full-wave simulation and practical realization, it is clear that the design goals are highly satisfied.