A compact transition structure includes a printed circuit board, wherein there is a rectangular region on one side of the printed circuit board and the rectangular region has a pair of long edges and a pair of short edges; a transition probe on the one side of the printed circuit board, wherein the transition probe extends into the rectangular region through a long edge of the rectangular region and has a terminal near a center of the rectangular region; and a coupler probe on the one side the printed circuit board, wherein the coupler probe extends into the rectangular region through a short edge of the rectangular region and has a terminal before the center of the rectangular region such that the coupler probe is electrically insulated from the transition probe.