A compact X-band CPW branch-line coupler using glass integrated passive device (GIPD) technology

In this paper, a compact X-band CPW branchline coupler is proposed using the glass integrated passive device (GIPD) technology. To reduce the circuit size and retain a similar return-loss bandwidth to that of conventional coupler, the asymmetrical CPW branch-type T-structures are employed to implement the proposed coupler. Each T-structure is realized by two sections of high-impedance lines with unequal lengths and a set of branch-type shunt stubs. The developed coupler has a 31.5 % 10-dB return loss bandwidth and only occupies a 17.79 % circuit size of the conventional one. The measured results of the developed branch-line coupler are in a good agreement with simulated results.