Patent ID: 8779293

Claim:
A coaxial cable comprising: an inner conductor located at a center portion of the cable; an insulator surrounding a surface of the inner conductor; an outer conductor surrounding an outside surface of the insulator; and a sheath surrounding the outer conductor, wherein the outer conductor has a corrugated tube shape having corrugation crests and corrugation troughs formed therein, and wherein an outer diameter I of the insulator, an inner diameter D 1 of the corrugation crest formed in the outer conductor, and an inner diameter D 2 of the corrugation trough formed in the outer conductor have the following relationship: D 1 + D 2 ⁢ 2 ≥ I ≥ D 2 , wherein a space between the inner conductor and an inner surface of the outer conductor is filled up with the insulator so that an air layer isolated within a corrugated portion of the outer conductor is formed between the insulator and the corrugation crest of the outer conductor, wherein a highest point of the corrugation crest formed in the outer conductor is expanded in the longitudinal direction of the cable, forming a straight line section in the corrugation crest on a cross-section of the longitudinal direction of the cable, wherein the outer diameter I of the insulator is larger than the inner diameter D 2 of the corrugation trough, wherein the straight line section in the corrugation crest and the outermost surface of the insulator which contacts with the air layer are substantially parallel to each other so that the air layer has a uniform thickness, wherein an above-to-below ratio of the lengths of the outer conductor above and below a median line between a maximum height of the corrugation crest and a minimum height of the corrugation trough of the outer conductor, has a range from 0.5 to 0.8.