AU2009351695B2 - An improved high frequency antenna - Google Patents

Abstract

The present invention discloses an antenna having extended read range for radio frequency identification implementations (RFID) using a tuning circuit (101) for setting operating frequency and read range, an antenna (102) which can be customised in shape and size, a coaxial cable (103) connected to the tuning circuit (101) and terminating at a computer using a BNC connector (105), that connects to the computer through a high frequency reader (106), a plastic casing (104) for housing all the components and an application software (107) for reading and displaying information.

Description

- 1 AN IMPROVED HIGH FREQUENCY ANTENNA The present invention relates to radio frequencies. More particularly, the present invention relates to an improved antenna having an extended read range for 5 radio frequency identification implementations (RFID). BACKGROUND TO THE INVENTION Radio frequency identification RFID is a technology similar in theory to bar 10 code identification. With RFID, the electromagnetic coupling in the radio frequency portion of electromagnetic spectrum is used to transmit signals. Typically, an RFID system consists of an antenna or coil, a transceiver with a decoder and a transponder or RF tag electronically programmed with unique information in it. The antenna emits radio -signals to activate the tag and to read and write data to it. 15 Antennas are the conduits between the tag and the transceiver, which controls the system's data acquisition and communication. Antennas are available in a variety of shapes and sizes; they can be built into a door frame to receive tag data from persons or mounted on specially designed walkways in shopping malls. The electromagnetic field produced by an antenna can be constantly present when 20 multiple tags are expected continually. RFID tags come in a wide variety of shapes and sizes. Animal tracking tags, inserted beneath the skin, can be as small as a pencil lead in diameter and one-half inch in length. The significant advantage of all types of RFID systems is the non-contact, non-line 25 of-sight nature of the technology. Tags can be read through a variety of substances such as snow, fog, ice, paint, and other visually and environmentally challenging conditions, where barcodes or other optically read technologies would be useless. The read/write capability of an active RFID system is also a significant advantage in interactive applications such as inventory or maintenance tracking. 30 Though it is a costlier technology (compared with barcode), RFID has become indispensable for a wide range of automated data collection and identification applications that would not be possible otherwise. 47011851 (GHMatters) P87817.AU 2/10/13 - 2 However, commercially available RFID systems come with a limited read range characteristics and fixed antenna size. This type of implementation limits the usage of the RFID and therefore does not maximize the potential of the technology. 5 SUMMARY OF THE INVENTION In a broad aspect the invention provides an antenna assembly having an extended read range for radio frequency identification implementations comprising: a housing; 10 an antenna provided in the housing and shaped to substantially follow the interior of the housing; a tuning circuit comprising two or more variable capacitors connected in parallel and arranged to adjust the operating frequency of the antenna, the tuning circuit comprising a resistor arranged to adjust the Q factor of the antenna; is a coaxial cable comprising a first end connected to the tuning circuit and a second end arranged to be connected to computer via a high frequency reader. BRIEF DESCRIPTION OF THE DRAWING 20 The present invention will now be described in greater detail, with reference to the accompanying drawing, in which: Figure 1 is a schematic diagram showing implementation of a high frequency antenna according to an embodiment of the invention; and 25 Figure 2 is a perspective view of a high frequency antenna according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE DRAWINGS 30 Referring to Figure 1, a high frequency antenna of the present invention consists mainly of a tuning circuit 101, an antenna 102, a coaxial cable 103 with variable length, a plastic casing 104, a male BNC connector 105 that is connected to a high frequency reader 106 that acts as an intermediate device to 47011851 (GHMatters) P87817.AU 2/10/13 - 3 obtain information from the antenna 102 and transmit the information to an application software installed in a computer 107. The connection between the computer and the HF Reader is through RS232. 5 The tuning circuit 101 is used to set the desired frequency for the operations of the RFID. The operating frequency is pivotal to the successful implementation of the present invention as the RF tag will also operate at the same frequency enabling the circuit board or antenna 102 to read information from the RF tag. The present invention operates at a frequency of 13.56 IVRZ at 50 ohms 10 impedence but is not limited to this frequency. The frequency may be tuned for different implementations. Still referring to Figure 1, the tuning circuit 101 is connected by circuitry to the loop of the antenna 102 that is made with a copper tape. The antenna 102 is used to 15 activate the RFID tags to read information from RF tags and relay that information using a coaxial cable 103 to an application software via the high frequency reader 106. The application software is able to display information from the RF tag, write information to the RF tag and enable / disable security measures. The antenna 102 used in the present invention comprise of an antenna 20 loop made of copper and other fixed elements such as variable capacitors, resistors and high speed switching diodes. The resonance tuning of the circuit board or antenna 102 of 13.56 MHz is achieved by using mica capacitors approximating to 1OOpF. The fixed elements include 25 variable capacitors of which the value ranges from 1OnF to 60nF; all connected in parallel to allow tuning of the antenna 102. The capacitor legs are modified to allow them to be soldered. A 40K), 2 Watt thick film resistor, adjusts the Q factor of the antenna 102. 30 The Q factor in general is used to measure the output of an antenna 102. The switching diode is used for switching the frequency bands. The antenna 102 is uniquely shaped to follow the plastic casing 104 thus allowing a larger read radius of up to 30cm from the base. The antenna 102 can be 47011851 (GHMatters) P87817.AU 2/10/13 - 4 customised to different size and different read radius which is among the novel features of the present invention. Information relay from the antenna 102 to the application software is performed 5 using a coaxial cable 103 that is connected to the tuning circuit 101 and the information will then be passed to the computer 107 through the high frequency reader 106 with the coaxial cable ending with BNC connector 105. Most commercially available computers comes with a female BNC receiver built in the circuit board therefore not requiring any additional hardware cost for the 10 implementation of the present invention. In addition, the plastic casing 104 used in the present invention offers the advantage of weight and mobility while still maintaining overall durability and also protects the antenna and tuning circuit. Referring to Figure 2, a high frequency antenna 201 in a preferred embodiment of is the invention is a cubical shape enclosed by a housing 202. A coaxial cable 203 extends out of the housing 202 and connects to the computer (not shown) via the high frequency reader 106. Preferably, the housing 202 is having, but not limited to, a dimension of 32 cm x39.5 cm x 3.1 cm. 2o The present invention will now be described by way of an example EXAMPLE In a preferred embodiment, the present invention can be used in a library for 25 tracking of tagged books. The books can be checked out for borrowing and checked in upon return of the books. The antenna will be able to read approximately 30 cm from the base enabling more books to be read at a time. This will depend on the thickness of each book. All scanned books from the antenna will display information of the book and details of the borrower in the 30 application software running on a standard computer. The antenna can also be used to activate or deactivate a surveillance system or Electronic Article Surveillance (EAS) which is an anti-theft feature that is available within the RFID tag. Typically, EAS systems are used to electronically 47011851 (GHMatters) P87817.AU 2/10/13 - 5 detect goods with tag that have not been authorised when they are removed from a retailer. For this application, this system will be able to detect if a book is leaving the library premises without being checked out first (or the EAS being disabled upon borrowing the book). In an event if the book with enabled EAS is taken out from 5 the library that passes through a gate antenna, an alarm will go off alerting the library personnel that the book is taken out from the library by an unauthorised person or it's taken without being borrowed with authorisation. The invention may be advantageous in that it provides a high frequency antenna with 10 extended read range capability. The invention may also be advantageous in that it provides an antenna that can be customized in size and shape. It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that such prior art forms a part of the common general 15 knowledge in the art, in Australia or any other country. In the claims that follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an 20 inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 47011851 (GHMatters) P87817.AU 2/10113

Claims (9)

1. An antenna assembly having an extended read range for radio frequency identification implementations comprising: 5 a housing; an antenna provided in the housing and shaped to substantially follow the interior of the housing; a tuning circuit comprising two or more variable capacitors connected in parallel and arranged to adjust the operating frequency of the antenna, the tuning circuit 10 comprising a resistor arranged to adjust the Q factor of the antenna; a coaxial cable comprising a first end connected to the tuning circuit and a second end arranged to be connected to computer via a high frequency reader.

2. An antenna assembly as claimed in claim 1 where the housing dimensions are 15 approximately 32cm x 39.5cm x 3.1cm.

3. An antenna assembly as claimed in claim 1 or claim 2 where the read range is approximately 30cm from the base of the housing. 20

4. An antenna assembly as claimed in any one of claims 1 to 3 where the capacitors are mica capacitors.

5. An antenna assembly as claimed in any one of claims 1 to 4 where the capacitors have a capacitance of between 1OnF and 60nF. 25

6. An antenna assembly as claimed in any one of claims 1 to 5 where the resistor is a thick film resistor.

7. An antenna assembly as claimed in any one of claims 1 to 6 where the resistor 30 is a 40KO, 2W resistor.

8. An antenna assembly as claimed in any one of claims 1 to 7 comprising a BNC connector connected to the second end of the coaxial cable. 47011851 (GHMatters) P87817.AU 2/10/13

9. An antenna assembly substantially as herein described with reference to the accompanying drawing. 47011851 (GHMatters) P87817.AU 2/10/13