New design of frequency-dependent phase shifter for array sensor applications

This article presents a microstrip phase shifter whose frequency-dependent phase response is designed to present the desired phase variation as a useful device for frequency-controlled antenna array systems. The architecture consists of the parallel connection of open-stubs on a main transmission line. The analytical model of the device is presented, its transfer function is derived and compared with a conventional transmission line. The theoretical results show that the phase and amplitude responses can be designed by selecting the number, the length, and the characteristic impedance of the open-stubs. In order to validate the frequency controlled phase shifter model an architecture is proposed, that consists of a three-port device based on a power divider with a phase shifter on one of the output ports and a conventional transmission line on the other. A prototype of this architecture has been manufactured to operate in a frequency range of 2.8 GHz to 3.4 GHz. The magnitude and phase measurements of the scattering parameters show good agreement with the theoretical predictions.