Antenna for transponder

• US 6,885,342 B2
• Filed: 01/15/2001
• Issued: 04/26/2005
• Est. Priority Date: 02/08/2000
• Status: Expired due to Term

• Current Assignee: Q-Free ASA
• Original Assignee: Q-Free ASA
• Inventors: Vavik, Geir, Saegrov, Atle
• Primary Examiner(s): Vannucci, James
• Application Number:
  US10/169,763
• Publication Number:
  US 20030117329A1
• Time in Patent Office: 1,562 Days
• Field of Search: 343/700.MS, 343/756, 343/909, 343/769, 343/846
• US Class Current: 343/700.0MS
• CPC Class Codes: H01Q 1/2208 associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142

Abstract

Antenna for sending and receiving microwave radiation, e.g. for use in a transponder in a transponder system for wireless payment of tolls, or the like. It has an excited antenna element (13) placed on a dielectric antenna carrier or substratum (11), e.g. on a printed circuit board laminate with a copper covered plastic basis suitable for manufacturing of so-called printed circuits. To increase the performance of the antenna for high production rates with cheap materials, the antenna element is placed such that it gets a directional effect mainly perpendicular to a bearing plane (12) of the substratum (11).

Claims

1. An antenna for sending and receiving microwave radiation for use in a transponder system for wireless toll payment, comprising:

a dielectric antenna supporter (11) having a bearing surface (12),

a frame shaped or loop shaped excited antenna element (13) extending in a first plane disposed on the dielectric antenna supporter bearing surface (12),

a polarization transformer (22), wherein the excited antenna element is linearly polarized and disposed at a predetermined distance from the polarization transformer (22) to transform linearly polarized radiation to circular or elliptical polarized radiation, and wherein the polarization transformer (22) operates as a director,

a reflector disposed at a predetermined distance from the excited antenna element,

at least one parasite element or director placed in a predetermined distance from the excited antenna element,

wherein the frame or loop antenna comprises two substantially equal shaped frames or loops placed at a predetermined distance, and a diode (25) connected to the frames or loops (14, 15) for demodulation, and

a capacitor (23) connected to the frames or loops (14, 15).

2. Antenna according to claim 1, wherein at least one additional antenna element assigned to the excited antenna element (13) is selected from the group consisting of a reflector, directors, and a polarization transformer, and is radiatively connected to the excited antenna element (13) via a medium having a constant and low dielectric losses, to give the lowest relative dielectric rate possible.

3. Antenna according to claim 1, wherein the excited antenna element (13) and/or at least one additional antenna element selected from the group consisting of a reflector, directors and a polarization transformer are arranged with strip-line technology on a thin plastic film, said thin plastic film being held in a predetermined distance from the bearing plane (12) of the dielectric antenna supporter (11).

4. Antenna according to claim 1, wherein the antenna capacity or resistance is increased to achieve a low Q-factor of 5-10.

5. Antenna according to claim 1, wherein the reflector (16) is a metallic plate.

6. Antenna according to claim 5, wherein said polarization transformer (22) is octagonally shaped metallic plate.

7. Antenna according to claim 6, wherein the frame or loop antenna is shaped as a Quad antenna having one or more quadratic frames or loops (14, 15).

8. Antenna according to claim 6, wherein the frame or loop antenna is shaped with one or more ring-shaped, elliptical or polygonal frames or loops.

9. Antenna according to claim 1, wherein the circumference of the frames or the loops is in the size of the wavelength (λ

) of the received and respectively sent microwave radiation.