Antenna device

An electronic instrument comprising:

• a housing;
• an antenna device disposed inside the housing and including:
• a flat antenna comprising:
• an antenna-side insulator that has a flat shape;
• an antenna-side signal line path conductor that is disposed on the antenna-side insulator;
• an antenna-side first ground conductor that is disposed on the antenna-side insulator along the antenna-side signal line path conductor and disposed at a distance from the antenna-side signal line path conductor;
• and
• a matching circuit that matches an impedance of the antenna-side signal line path conductor to an impedance of the antenna-side first ground conductor;
• a signal transmission cable comprising:
• a cable-side insulator;
• a cable-side signal line path conductor that is disposed along a longitudinal direction of the cable-side insulator with a first end connected to a power feeding circuit;
• and
• a cable-side ground conductor disposed at a distance from the cable-side signal line path conductor with a first end connected to a ground;
• and
• a radiation area setting member disposed in a signal path from the signal transmission cable to the flat antenna, with the radiation area setting member configured to demarcate the flat antenna as a radiation area and to set a signal path in the signal transmission cable as a non-radiation area,
• wherein, in the antenna-side insulator, the antenna-side signal line path conductor is disposed to face the antenna-side first ground conductor at a predetermined interval therefrom,
• wherein the signal transmission cable is a coaxial cable, and
• wherein the radiation area setting member is a magnetic member.

A rack for displaying merchandise each having an RFID tag attached thereto, the rack comprising:

• an antenna device configured to communicate with the RFID tag and being disposed in a space having the merchandise displayed therein or laid facing the space, wherein the antenna device comprises:
• a flat antenna comprising:
• an antenna-side insulator that has a flat shape;
• an antenna-side signal line path conductor disposed on the antenna-side insulator;
• an antenna-side first ground conductor disposed on the antenna-side insulator along the antenna-side signal line path conductor and disposed at a distance from the antenna-side signal line path conductor;
• and
• a matching circuit that matches an impedance of the antenna-side signal line path conductor to an impedance of the antenna-side first ground conductor;
• a signal transmission cable comprising:
• a cable-side insulator;
• a cable-side signal line path conductor disposed along a longitudinal direction of the cable-side insulator with a first end connected to a power feeding circuit;
• and
• a cable-side ground conductor disposed at a distance from the cable-side signal line path conductor with a first end connected to a ground;
• and
• a radiation area setting member disposed in a signal path from the signal transmission cable to the flat antenna, with the radiation area setting member configured to demarcate the flat antenna as a radiation area and to set a signal path in the signal transmission cable as a non-radiation area,
• wherein, in the antenna-side insulator, the antenna-side signal line path conductor is disposed to face the antenna-side first ground conductor at a predetermined interval therefrom,
• wherein the signal transmission cable is a coaxial cable, and
• wherein the radiation area setting member is a magnetic member.