BSTO/MgO microstrip line 45° phase shifter with wide tuning range and low insertion loss

The design of a 7-coupled microstrip line 45° phase shifter is proposed in this paper. Tunability was achieved by utilizing the characteristic that the relative dielectric constant of ferroelectrics depends on the applied bias voltage. To obtain a large tuning range of the phase shifter, we added many couplings within the allowable loss range. In terms of control voltage, we applied 0 V and 150 V respectively to inspect the variance of phase shift. At 16 GHz and 0 V, DPS (differential phase shift) is 45°. But at the same frequency and 150 V, DPS is 126°. Thus, the tuning range of the phase shifter reaches 81°. Our frequency band of interest is from 15 GHz to 16.8 GHz. As a result of simulations, RL (return loss) is larger than 19 dB and IL (insertion loss) is less than 2.7 dB with both 0 V and 150 V in this frequency range. The size of the tunable phase shifter is 7.4 mm × 2.2 mm × 0.5 mm.