Continuously Tunable K/Ka-Band Phase Shifter Implemented Using Coplanar Waveguides

A continuously tunable phase shifter operating from 20 GHz to 30 GHz based on a broadside-coupled structure is presented. In this design, the broadside-coupled structure is constructed using a grounded coplanar waveguide instead of a microstrip line or stripline. As a result, the proposed structure can be implemented on both sides of a single piece of printed circuit board, leading to reduced manufacturing complexity and cost. To validate the proposed structure, a tunable phase shifter operating from 20 GHz to 30 GHz is designed and fabricated. The measured results show that the return loss of the design is above 10 dB across the entire operating bandwidth. Meanwhile, the design achieves a tunable phase shift range of more than 90° with ±6.7° phase imbalance and the insertion loss is below 1.25 dB from 20 GHz to 30 GHz. The simple structure and the achieved performance make the proposed design a promising candidate for building tunable feeding networks in the upcoming K/Ka-band low Earth orbit satellite communications systems.