Design of Compact Reflection-Type Phase Shifters With High Figure-of-Merit

This paper presents reflection-type phase shifters (RTPSs) with very high figure-of-merit (FoM) and low insertion-loss variation, achieving up to 360°relative phase shifts. Two compact topologies are proposed. They were implemented at the working frequency of 2 GHz on a printed circuit board technology. The reflection loads are based on the use of one transmission line loaded by varactors, forming L- or π-type networks. An automatic procedure is given to design the electrical length and the characteristic impedance of the transmission line of the reflection loads as well as the output impedance of the 3-dB branch-line coupler in order to get phase shifters with the highest possible FoM. Measurement results of the first L-type network RTPS showed a relative phase shift of 201°for only 0.54 dB ± 0.09 dB of insertion loss, leading to a FoM of 319°/dB. A relative phase shift of 385°was achieved for the π-type network RTPS with insertion loss of only 0.98 dB ± 0.58 dB, leading to an FoM of 246°/dB. In both cases, simulation and measurement results fit very well. Moreover, the return loss over a 10% bandwidth is always better than 10.9 dB for the first RTPS and better than 12.3 dB for the second one, respectively. The comparison with previous works shows more compact reflection loads with electrical performance equal to the state-of-the-art.