Experimental evaluation of basic circuit components using buried microstrip lines for constructing high-density microwave integrated circuits

The buried microstrip line (BMSL) is a promising transmission line structure for realizing low crosstalk characteristics. The measured crosstalk characteristics of model BMSL´s have shown good agreement with the estimated ones based on the rectangular boundary division method and the finite-difference time-domain (FDTD) method, indicating that these calculation methods are appropriate for estimating the performance of BMSL´s. These results also confirm our expectation that BMSL´s have extremely low crosstalk characteristics such as -100 dB in real circuits at high microwave frequencies. The basic circuit components to construct high-density microwave circuits using BMSL´s, couplers, stub matching circuits, and gap-coupled resonance filter circuits, were fabricated and experimentally evaluated