CN110334557A - Method for increasing card reading distance of RFID card reader and RFID card reader - Google Patents

Abstract

The invention discloses a method for increasing the card reading distance of an RFID card reader and the RFID card reader. The RFID card reader is attached with an independent second resonant antenna. The second resonant antenna is arranged on one side of the card reading area of the first resonant antenna of the card reader circuit. The coil of the second resonant antenna is arranged in parallel with the coil of the first resonant antenna. The resonant frequency of the resonant antenna is the same as that of the first resonant antenna, and the first resonant antenna and the second resonant antenna realize signal transmission through resonant inductive coupling; the increased reading area of the RFID card reader is located on both sides of the second resonant antenna coil . The RFID card reader of the present invention has a simple structure and can expand the reading and writing area by more than 50%. The second resonant antenna does not need to be connected with any wires and cables.

Description

Method for increasing card reading distance of RFID card reader and RFID card reader

[technical field]

The invention relates to radio frequency identification technology, in particular to a method for increasing the card reading distance of an RFID card reader and the RFID card reader.

[Background technique]

Passive RFID has three commonly used frequency bands: low frequency (LF), high frequency (HF) and ultra high frequency (UHF). The low frequency has two frequency bands of 125KHz and 134.2KHz, and the high frequency uses 13.56MHz. In low-frequency and high-frequency passive RFID systems, the energy and information transfer between the reader and the tag is realized by the principle of near-field electromagnetic coupling. The reader includes an LC resonant antenna composed of a coil and a matching capacitor, which emits electromagnetic waves and receives electromagnetic waves reflected by the tag through the antenna; the tag includes a resonant antenna composed of a coil and matching capacitors, which receives the electromagnetic waves emitted by the reader. The electromagnetic wave is powered by the electromagnetic wave, and the matching degree is adjusted through the internal logic to realize the back coupling of the electromagnetic wave, thereby transmitting information.

The communication distance between the reader and the tag, usually called the reading and writing distance, is the main performance index of the low-frequency and high-frequency RFID system, and the parameters such as the transmit power, antenna efficiency, receiving sensitivity of the reader, and the wake-up threshold and antenna efficiency of the tag related.

The technology of low-frequency and high-frequency RFID readers is relatively mature, and the technical scheme of improving the reading and writing distance through the above parameters has basically reached its limit range. In some application fields that need to further increase the reading and writing distance, the optimization degree of the existing technology is relatively limited.

In the case where the maximum communication distance between the reader and the tag has been determined, in practical applications, if the engineering requirements cannot be met, the multi-antenna method is generally used to expand the area for reading and writing tags by adding antennas. Both the utility model patent with publication number CN206058212U and the utility model patent with publication number CN202632300U describe the application of multiple antennas. There are two ways to add antennas, one is that each antenna is equipped with an independent RF read and write circuit, and the other is that multiple antennas share a set of RF read and write circuits, which are switched by electronic switches. No matter which of the utility model patents mentioned above, there is a complex structure and a connecting cable that needs to add an antenna, which brings inconvenience to the construction.

[Content of the invention]

The technical problem to be solved by the present invention is to provide a method that is convenient for construction and can increase the card reading distance of the RFID card reader.

Another technical problem to be solved by the present invention is to provide an RFID card reader with simple structure, convenient construction and large card reading distance.

In order to solve the above technical problems, the technical solution adopted by the present invention is a method for increasing the reading distance of an RFID card reader. The RFID card reader is attached with an independent second resonant antenna, and the second resonant antenna is arranged on the first card reader circuit. One side of the resonant antenna card reading area, the coil of the second resonant antenna is arranged in parallel with the coil of the first resonant antenna, the resonant frequency of the second resonant antenna is the same as the resonant frequency of the first resonant antenna, the first resonant antenna and the second resonant antenna The antenna realizes signal transmission through resonant inductive coupling; the increased reading area of the RFID card reader is located on both sides of the second resonant antenna coil.

An RFID card reader includes a card reader circuit and a second resonant antenna, the card reader circuit includes a first resonant antenna and a resonant circuit, the first resonant antenna includes a first coil, the first coil is connected to the resonant circuit, and the second The resonant antenna includes a second coil and a matching capacitor, the two ends of the second coil are connected to the two ends of the matching capacitor; the second coil is arranged in parallel with the first coil, and the resonant frequency of the second resonant antenna is the same as that of the first resonant antenna, The two are resonantly coupled inductively.

In the aforementioned RFID card reader, the distance between the second coil and the first coil is greater than the limit distance for card reading by the first coil of the card reader circuit.

In the aforementioned RFID card reader, the distance between the second coil and the first coil is 150% to 200% of the limit distance of the first coil for reading cards.

In the RFID card reader described above, the RFID card reader is an access door reader, the first coil and the second coil are placed vertically, and a card reading access door is formed between them.

The above-mentioned RFID card reader includes a casing, the card reader circuit is arranged in the casing, the second coil is arranged on the casing, and the card reading area is outside the second coil.

In the RFID card reader described above, the card reader circuit includes a circuit board, and the first coil is arranged on the circuit board as a printed antenna.

The RFID card reader of the present invention has a simple structure and can expand the reading and writing area by more than 50%. The second resonant antenna does not need to be connected with any wires and cables, and is easy to install and convenient to construct.

[Description of drawings]

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a schematic diagram of an RFID card reader according to an embodiment of the present invention.

Fig. 2 is a structural diagram of an RFID card reader according to Embodiment 1 of the present invention.

Fig. 3 is a structural diagram of an RFID card reader according to Embodiment 2 of the present invention.

[Detailed ways]

The RFID card reader in the embodiment of the present invention is a low-frequency or high-frequency RFID reader-writer, and its principle is shown in FIG. 1 , including a card reader circuit and a second LC resonant antenna 21 .

The card reader circuit includes a first LC resonant antenna 11 and a resonant circuit 10 , the first LC resonant antenna 11 includes a first coil L1 and a first matching capacitor C1 , and the first coil L1 is connected to the resonant circuit 10 . The first matching capacitor C1 resonates with the first coil L1, and the resonant frequency is the transmitting frequency of the reader.

The second LC resonant antenna 21 includes a second coil L2 and a second matching capacitor C2, and the two ends of the second coil L2 are connected to the two ends of the second matching capacitor C2. The second coil L2 is arranged parallel to the first coil L1, and the resonant frequency of the second LC resonant antenna 21 is the same as that of the first LC resonant antenna 11. In order to obtain a better space expansion effect, the second coil L2 is generally connected with the first Coil L1 adopts the same physical dimensions.

The first LC resonant antenna 11 and the second LC resonant antenna 21 realize signal transmission through resonant inductive coupling; the enlarged reading area of the RFID card reader is located on both sides of the second LC resonant antenna coil L2.

When the RFID card reader starts to read the card, the electromagnetic wave signal is transmitted through the first resonant antenna, and the coil of the second resonant antenna starts to resonate after receiving the electromagnetic wave excitation of the same frequency. The area between the first resonant antenna and the second resonant antenna is electromagnetic wave High energy density area, between this area, electronic tags can be effectively read and written. In addition, there is also an effective read-write area on the side of the second resonant antenna coil away from the first resonant antenna, which further expands the read-write range of the reader.

The structure and principle of the RFID card reader in Embodiment 1 of the present invention are shown in FIG. 2 .

The RFID card reader in Embodiment 2 is a 134.2KHz low-frequency channel door card reader, including a reader-writer circuit, a first resonant antenna, and a second resonant antenna. The first resonant antenna includes a coil and multiple high-voltage film capacitors. The coil is wound by copper wire with an inductance of 350uH. During the winding process, there may be errors in inductance, which can be tuned by adjusting the size of the resonant capacitor. All high-voltage film capacitors are first connected in parallel, and then connected in series with the coil. The sum of the capacitance of the film capacitors is based on the formula Sure.

The second resonant antenna uses the same coil as the first resonant antenna and a resonant capacitor with the same capacity, and the two ends of the coil L2 are respectively connected to the two ends of the capacitor C2.

Both the first coil L1 and the second coil L2 are placed vertically with a distance of 60 cm between them, forming a passage door. The distance between the second coil L2 and the first coil L1 is greater than the card reading limit distance of the first coil L1 of the card reader circuit. The distance between the two can generally be 150% to 200% of the limit distance for reading the card by the first coil L1.

In this embodiment, the reader circuit is connected to the first resonant antenna to read the card. Without the second resonant antenna, the reader can read the glass tube electronic tag 100 for animal injection with a diameter of 1.2mm at a maximum distance of 35cm, which has reached the industry-leading level; after adding the second resonant antenna, the first resonant antenna and Effective card reading can be performed in the 60cm channel space formed between the second resonant antennas.

The structure and principle of the high-frequency 13.56MHz RFID reader-writer in Embodiment 2 of the present invention are shown in FIG. 3 .

The RFID reader has a housing 30, and the high-frequency RFID reader generally adopts a PCB printed coil antenna, and the reading distance is 0-10 cm.

The circuit board 40 of the reader/writer circuit is arranged in the lower part of the casing 30 , and the first coil L1 is arranged on the circuit board 40 as a printed antenna 41 . Due to structural limitations, the reader circuit board 40 is installed a certain distance below the casing 30 , resulting in a very small reading and writing distance outside the casing 30 , which cannot meet the usage requirements.

In this embodiment, a resonant antenna is added outside the reader to expand the reading area. The added resonant antenna consists of a flexible printed circuit board and a capacitor, where a coil is etched on the flexible printed circuit board, there are pads at both ends of the coil, and the capacitor is soldered. The resonant frequency of the capacitor and coil inductance is 13.56MHz.

The coil L2 of the second resonant antenna is arranged on the top plate 31 of the casing 30, at the reading limit of the printed antenna 41 of the high-frequency reader, and a new reading area can be added outside the coil L2 of the second resonant antenna. In this embodiment, the extended reading and writing area of the RFID reader is above the second coil L2, and the electronic tag 100 is above the second coil L2 when reading and writing.

When the reader emits electromagnetic waves through the built-in antenna (the first resonant antenna), the second resonant antenna is excited by the electromagnetic waves and starts to resonate with the same frequency, and forms a new electromagnetic field area on the side away from the reader. The intensity of the electromagnetic field in this area is much greater than the intensity of the electromagnetic wave emitted by the reader antenna, which reaches the same position after space attenuation. In this area, the electronic tag 100 can be activated and couple back signals. The return signal also first reaches the second resonant coil, and then is coupled to the built-in antenna of the reader by the second resonant coil.

Claims (7)

1. a kind of method that RFID card reader increases card reading distance, which is characterized in that it is humorous that RFID card reader adds independent second Shake antenna, and the second resonant antenna is arranged in the side in card reader circuit the first resonant antenna card reading region, the second resonant antenna The coil of coil and the first resonant antenna parallel arrangement, the resonance frequency of the second resonant antenna and the resonance frequency of the first resonant antenna Rate is identical, and the first resonant antenna is coupled by resonant inducing with the second resonant antenna and realizes signal transmission；RFID card reader increases Card reading region be located at the two sides of the second resonant antenna coil.

2. a kind of RFID card reader, including card reader circuit, card reader circuit includes the first resonant antenna and resonance circuit, first Resonant antenna includes first coil, and first coil is connect with resonance circuit, which is characterized in that including the second resonant antenna, second Resonant antenna includes the second coil and matching capacitance, the both ends of two termination matching capacitances of the second coil；Second coil and first Coil parallel arrangement, the resonance frequency of the second resonant antenna is identical as the resonance frequency of the first resonant antenna, the two resonant inducing Coupling.

3. RFID card reader according to claim 2, which is characterized in that the second coil is greater than at a distance from first coil to be read The critical distance of card device circuit first coil card reading.

4. RFID card reader according to claim 3, which is characterized in that the second coil is first at a distance from first coil The 150% to 200% of the critical distance of coil card reading.

5. RFID card reader according to claim 3, which is characterized in that the RFID card reader is access door card reading Device, first coil are placed vertically with the second coil, form the access door of card reading between the two.

6. RFID card reader according to claim 2, which is characterized in that including shell, card reader circuit is arranged in shell In, the second coil is arranged on shell, and card reading region is on the outside of the second coil.

7. RFID card reader according to claim 2, which is characterized in that card reader circuit includes circuit board, first coil On circuit boards as printed antenna arrangement.