Vertical RF Transition Using Spring Contact Probes with Passively Switched DGS Compensating for Impedance Matching

In this paper, a novel vertical radio frequency (RF) transition with a passively switched defected ground structure (DGS) compensating for the RF connection between different substrates is presented. The proposed transition consists of spring contact probes (SCPs), dielectric supporters for SCPs, microstrip lines with DGS on dielectric substrates, and the metal chassis on which they are installed. For this type of vertical transition using SCPs, the substrate is pushed up by the pressure of SCPs, which produces an air gap between its ground plane and metal chassis and causes an impedance mismatch. A passively switched DGS is utilized to compensate for it. Without the air gap, the DGS is in an OFF state since both sides of the DGS are short-circuited by the metal chassis. Furthermore, with the air gap, the DGS is ON and operates as a compensation circuit. The operation and effectiveness of the proposed transition is verified by electromagnetic simulation, fabrication, and measurement. The measurement results show that the vertical transition utilizing the proposed DGS achieves a better return loss than the one without the DGS by 3 dB at X-band with the simulated air gap.