Significantly enhanced isolation of SPDT switch using punched hole structure

Experimental results of a series-connected single pole double throw (SPDT) switch in a novel punched-hole-structure (PHS) are presented. In the PHS, the dielectric and ground layers are punched out in a specific size from the microstrip line, and diodes are placed over the punched holes to connect the microstrip lines. Radio performance of the novel SPDT switch can be improved due to additional L-C parameters introduced by the punched holes. When the radius of punched hole is the same as the width of microstrip line, 0.03 /spl lambda//sub c/ (/spl lambda//sub c/: wavelength of 2.7 GHz), the implemented SPDT switch shows an increase of about 20-dB isolation between two output ports, compared to a conventional SPDT switch without holes. Furthermore, by tuning capacitors around the punched holes, the operating frequency band can be widened by approximately 250% in the SPDT.