Minimising the losses due to EM field discontinuities in a compact LC tunable microstrip line phase shifter

We present here our recent result on reducing the losses of a multiple-folded tunable microstrip line phase shifter based on liquid crystal (LC) for the regime of low microwave (MW) frequencies. It is shown that the insertion and return losses can be decreased through the minimization of the electromagnetic (EM) wave discontinuities in the folded microstrip line structure. Based on a modified 6-folded microstrip line structure, the return loss of the currently developed LC phase shifter was reduced by 10 dB and the insertion loss was limited to <;10 dB in the frequency range up to 10GHz. In addition, the impact of LC material loss in low MW frequency regime is discussed.