Patent ID: 8378223

Claim:
A differential flat spiral delay line structure disposed on a substrate, the substrate including a dielectric base layer, a layout layer and a grounding layer, the dielectric base layer being formed with a plurality of vias, the layout layer and the grounding layer being spaced apart by the dielectric base layer, the grounding layer having a grounding circuit, the delay line structure comprising: a spiral delay line pair including two parallel spiral delay lines, said spiral delay line pair being disposed in the layout layer and including a first outer straight section extending in a manner from an input end along a first direction to a first outer end, a first outer bent section extending in a manner from said first output end along a second direction perpendicular to said first direction and a third direction opposite to said first direction to terminate at a first inner end, an inner spiral region located between said first inner end and said first outer straight section, extending in a manner from said first inner end to bend reciprocally along said first and third directions adjacent to said first outer straight section and terminating at a second inner end proximate to said input end, thereby forming a plurality of inner bent parts and a plurality of inner straight parts parallel to first outer straight section, a second outer bent section extending in a manner from said second inner end along said second direction and bending relative to said first direction and terminating at a second outer end proximate and exterior to said an inner spiral region, and a second outer straight section extending in a manner from said second outer end along said first direction toward an output end; and at least one grounding guard trace extending through the vias in the dielectric base layer to couple electrically to the grounding circuit of the grounding layer, and being disposed on the layout layer along said first direction at a position matching one of the following requirements: (a) proximate and exterior to said first outer straight section; (b) between said first outer straight section and said inner spiral region; (c) between said plurality of inner straight parts; (d) between said inner spiral region and said second outer straight section; and (e) proximate and exterior to said second outer straight section; wherein, each of said first and second outer bent sections and said plurality of inner bent parts has a width smaller than each of said first and second outer straight sections and said plurality of inner straight parts.