Microwave Ferroelectric Phase Shifters Based on the Periodical Structures

Integrated phase shifters with a periodic structure that includes BaSrTiO₃ ferroelectric varactors parallel- or series-connected to the transmission line are investigated theoretically and experimentally. The phase shifters are designed for the frequency range 26-32 GHz. The dispersion characteristics and insertion losses in the transmission line of the phase shifters are analyzed with regard to the dependence of the capacitance and loss tangent of the varactors on control voltage and temperature. It is shown that parasitic amplitude modulation in the phase shifters can be suppressed if the connection scheme of the varactors takes into account the voltage dependence of the their loss tangent. In the phase shifters with series-connected varactors, the temperature dependence of the phase shift is much weaker than in those with parallel-connected varactors