I. Introduction
The substrate integrated wave guide (SIW) technology has Deen introduced quite recently [1]. This new technology has now reached its maturity with more and more industrials (particularly from the defense and aerospace sectors) implementing it in their products. The reason is that SIW offers an altemative to the bulky but high performance air-filled metallic waveguide and the lossy but low cost conventional printed circuit board (PCB) technologies [2].