Compact low‐loss millimeter‐wave shielded asymmetrical coplanar stripline to unilateral and antipodal finline transitions

Abstract

Compact and low-loss U-band shielded asymmetrical coplanar stripline (SACPS) to unilateral and antipodal finline transitions are proposed in this article for millimeter-wave circuits and systems applications. The principles of mode conversion and impedance matching are applied to the proposed transitions. In the SACPS to unilateral finline transition, the SACPS is firstly transformed into the asymmetrical unilateral finline to convert the quasi-TEM mode to the quasi-TE10 mode and then a tapered unilateral finline section is applied to realize impedance matching. For the U-band back-to-back SACPS to unilateral finline transition, the measured return loss is larger than 15 dB and the insertion loss is less than 1.5 dB with a minimum of 0.5 dB. In the SACPS to antipodal finline transition, the SACPS is firstly transformed into the defected ground microstrip (DGM) without changing the characteristic impedance. Then, the DGM is transformed into the asymmetrical antipodal finline to make mode conversion. At last, a tapered antipodal finline section is used for impedance matching. For the U-band back-to-back SACPS to antipodal finline transition, the measured return loss is larger than 12 dB and the insertion loss is less than 1.5 dB with a minimum of 0.3 dB.