Valve-integrated transponder

A valve-integrated transponder comprising:

• a detecting element that detects a condition inside a tire;
• a substrate on which the detecting element is mounted;
• an inverse F antenna element that outputs information detected by the detecting element to an outside;
• and
• a synthetic-resin casing that houses the detecting element, the substrate, and the antenna element, the casing being fitted to an end of an air valve attached to a wheel rim, the end of the air valve being located inside the tire, the casing being disposed at an outer side of a well of the wheel rim as viewed in a radial direction of the tire,
• wherein the substrate is disposed within the casing such that a longitudinal direction of the substrate is substantially perpendicular to an axial direction of the air valve and that a lateral direction of the substrate is parallel to the axial direction, and
• wherein the antenna element is disposed on a surface of the substrate that is opposite to a surface thereof facing the well, and wherein a central section of the antenna element in a longitudinal direction thereof is provided with a feed terminal and a ground terminal, the antenna element having a substantially line symmetrical shape where a pair of radiation conductors extend symmetrically from the feed terminal and the ground terminal toward opposite longitudinal ends of the antenna element, the pair of radiation conductors being inclined with respect to the substrate so as to be disposed substantially in parallel to the well that extends at an inner side of the transponder as viewed in the radial direction of the tire.