LC structure useful in radio frequency security systems

An LC structure for use in radio frequency security systems and resonant at at least one radio frequency, said LC structure comprising:

• flexible insulative layer comprised at least of a dielectric layer (88) folded back on itself about a predetermined fold line (92;
• 111) with its inner surface either face to face or indirectly joined via at least one additional layer (62;
• 93) therebetween, said insulative layer having on one surface an electrically conductive layer (87) configured to form
• (a) first and second alike planar multi-turn spirals (89, 90;
• 109, 110), which, in cooperation, form an inductive element,
• (b) at least two substantially two-dimensionally shaped portions (107, 108;
• 114, 115), each electrically connected to a respective spiral (89, 90;
• 109, 110), symmetrically positioned on opposite sides of said fold line (92;
• 111), thereby being juxtaposed and having sandwiched therebetween at least said dielectric layer (88) to form a capacitive element, each of said portions (107, 108;
• 114, 115) having a substantially straight boarder parallel to and spaced a short distance from the respective substantially straight boarder of the other portion (107, 108;
• 114, 115), respectively, thus leaving therebetween an elongated region in which said conductive layer is at least predominantly absent, the two-dimensional shape of each of said two portions (107, 108;
• 114, 115) serving to thereby stiffen said insulative layer and to thereby cooperatively oppose any tendency of said (combined) insulative and conductive layers to fold along any line other than said predetermined fold line (92;
• 111) and thus precisely localize the fold such that
• said two symmetrically positioned portions (107 and 108;
• 114, 115) and spirals (89, 90;
• 109, 110) are precisely juxtaposed opposite each other so that each turn of said first spiral (89;
• 109) is aligned with a respective turn of said second sprial (90;
• 110) in a counter-turn relationship with respect to each other when both are viewed from the same side, to thereby form a series of stripline loops each having distributed inductive and distributed capacitive components, so that--by virtue of said precisely localized fold--a predictable capacitance for said capacitive element results which, in combination with said inductive element, causes said LC structure to resonate at said radio frequency.