Design of Transition Circuits for Chip Assembly at Terahertz Band

In this paper, two transition circuits to assemble chips using coplanar waveguide (CPW) without back conductor at terahertz (THz) band are presented. The first transition circuit is adopting a CPW to microstrip line (MSL) transition circuit. Quarter wavelength radial MSL is used for RF ground connection between CPW and MSL. The second transition circuit is using flip-circuit structure. This transition circuit has CPW pad on one end, and a E-plane probe for CPW to waveguide mode transition. The circuit is suspended in a channel, and flip mounted on the CPW pad of the chip. Impedance matching with several step impedance CPW lines are adopted. All the transition circuits are simulated with HFSS. The results show that the return loss of the radial MSL transition circuit is less than −10dB at 100 to 170 GHz. The return loss of the flip-circuit is less than −15dB at 100 to 170 GHz. Compared with traditional gold wire bonding, the proposed transition structures significantly improve the performance at THz band.