Reading device
A reading device includes an antenna element, a substrate including a communication circuit and a ground plane, a connecting member protruding from the substrate in a thickness direction of the substrate and configured to electrically connect the communication circuit and the antenna element, and a casing configured to retain the antenna element, the substrate, and the connecting member. The antenna element is arranged separately from the substrate toward one side in the thickness direction. The casing includes a first surface portion that covers the substrate when viewed from the other side in the thickness direction. In a case where a distance in the thickness direction from a feed point to the ground plane is a first distance, and a distance in the thickness direction between the substrate and the first surface portion is a second distance, the first distance is greater than the second distance.
1 . A reading device comprising:
an antenna element;
a substrate including a communication circuit configured to perform transmission and reception of radio signals with an RFID tag via the antenna element, and a ground plane configured to provide a reference potential of the antenna element;
a connecting member protruding from the substrate in a thickness direction of the substrate and configured to electrically connect the communication circuit and the antenna element; and
a casing configured to retain the antenna element, the substrate, and the connecting member, the casing having a plate-like outer shape whose dimension in the thickness direction is smaller than dimensions in a height direction and a width direction when viewed in the thickness direction,
wherein the antenna element is arranged separately from the substrate toward one side in the thickness direction,
wherein the casing includes a first surface portion that covers the substrate when viewed from the other side in the thickness direction, and
wherein in a case where a distance in the thickness direction from a feed point at which the connecting member comes into contact with the antenna element to the ground plane is a first distance, and a distance in the thickness direction between the substrate and the first surface portion is a second distance, the first distance is greater than the second distance,
wherein the casing includes a second surface portion that covers the substrate when viewed from the one side in the thickness direction, and
wherein the antenna element is supported either (i) on a surface of the second surface portion at an inner side of the casing, or (ii) on a surface of the second surface portion at an outer side of the casing.
2 . The reading device according to claim 1 , wherein the reading device is configured to radiate an electromagnetic wave into a reading range, and to read information returned from the RFID tag using an energy of the electromagnetic wave.
3 . The reading device according to claim 1 ,
wherein the antenna element is supported on the surface of the second surface portion at the inner side of the casing.
4 . The reading device according to claim 1 ,
wherein the antenna element is supported on the surface of the second surface portion at the outer side of the casing.
5 . The reading device according to claim 1 , further comprising:
an external communication portion configured to perform wireless communication with a target that differs from a target of wireless communication performed via the antenna element;
a control portion configured to control the communication circuit and the external communication portion;
a battery; and
a power supply portion configured to supply a power of the battery to the communication circuit, the external communication portion, and the control portion.
6 . The reading device according to claim 5 , wherein a distance between the feed point and the communication circuit on the substrate is shorter than any of a distance between the feed point and the control portion, a distance between the feed point and the external communication portion, and a distance between the feed point and the power supply portion.
7 . The reading device according to claim 5 ,
wherein the communication circuit, the external communication portion, the control portion, and the power supply portion are arranged collectively on a surface of the substrate at which the substrate faces the antenna element, and
wherein the surface of the substrate that faces the antenna element is offset toward the other side in the thickness direction from a center position of the casing in the thickness direction.
8 . The reading device according to claim 5 , further comprising:
a parasitic antenna element that does not receive feeding of power from the communication circuit,
wherein the antenna element and the parasitic antenna element are arranged in parallel in the width direction, and
wherein the communication circuit is arranged on a same side as the antenna element with respect to the width direction.
9 . The reading device according to claim 8 , wherein the communication circuit, the external communication portion, the control portion, the power supply portion, and the battery are arranged collectively on one side in the height direction with respect to the antenna element and the parasitic antenna element.
10 . The reading device according to claim 9 ,
wherein the casing has a rectangular shape whose dimension in the height direction is greater than a dimension in the width direction when viewed in the thickness direction, and
wherein the antenna element, the communication circuit, the control portion, and the external communication portion are arranged in the named order from a first side to a second side in the height direction at one side in the width direction on the substrate, and the parasitic antenna element, the power supply portion, and the battery are arranged in the named order from the first side to the second side in the height direction at the other side in the width direction on the substrate.
11 . The reading device according to claim 9 ,
wherein the casing has a rectangular shape whose dimension in the height direction is greater than a dimension in the width direction when viewed in the thickness direction, and
wherein the antenna element, the communication circuit, and the power supply portion are arranged in the named order from a first side to a second side in the height direction at one side in the width direction on the substrate, and the parasitic antenna element, the external communication portion, and the battery are arranged in the named order from the first side to the second side in the height direction at the other side in the width direction on the substrate.
12 . The reading device according to claim 5 ,
wherein the substrate includes a recess portion accommodating at least a portion of the battery when viewed in the thickness direction, and
wherein the battery and the substrate overlap when viewed in a direction orthogonal to the thickness direction.
13 . The reading device according to claim 5 , wherein the connecting member includes a body portion having a cylindrical shape, a contact portion that is supported at a tip of the body portion, and a spring configured to urge the contact portion in a direction in which the contact portion protrudes from the body portion.
14 . The reading device according to claim 5 , further comprising:
a measurement portion disposed on the substrate and configured to measure information of a moving amount of the reading device or information of an environment in which the reading device is placed,
wherein a distance between the feed point and the communication circuit on the substrate is shorter than a distance between the feed point and the measurement portion.