Four-channel card reader

Abstract

The utility model relates to the technical field of card readers, and provides a four-channel card reader in order to solve the technical problems that an existing single-channel card reader is limited in coverage area and insufficient in signal processing capacity, the four-channel card reader comprises a transmitting circuit, a receiving circuit and a microcontroller U15, the transmitting circuit is a push-pull circuit composed of a triode Q10 and a triode Q2, and the receiving circuit is a push-pull circuit composed of a triode Q10 and a triode Q2. The antenna coil is driven to generate an electromagnetic field. The receiving circuit comprises an antenna coil L3, an antenna coil L4, an antenna coil L5, an antenna coil L6, an operational amplifier U6, an operational amplifier U7, an operational amplifier U12, an operational amplifier U13, a radio frequency conditioner U16 and a secondary amplification filter circuit, wherein the operational amplifier U6, the operational amplifier U7, the operational amplifier U12 and the operational amplifier U13 are used for amplifying signals of the four antenna coils respectively, and the radio frequency conditioner U16 is used for conditioning four paths of radio frequency signals respectively. The microcontroller U15 generates carrier signals through an SOUT pin of the microcontroller U15, collects and receives signals through an SIN pin of the microcontroller U15, and transmits decoded UI D data through a UART interface of the microcontroller U15. Through the four independent antenna coils and the corresponding amplification and conditioning circuits, processing of multiple paths of signals is realized, and the coverage range is expanded.

Description

Technical Field

[0001] This utility model relates to the field of card reader technology, and in particular to a four-channel card reader. Background Technology

[0002] Radio Frequency Identification (RFID) technology is a technology that enables contactless data transmission through radio waves and magnetic fields. It is widely used in access control systems, logistics management, payment terminals, and identity authentication. With the rapid development of the Internet of Things (IoT), RFID technology has gradually become one of the core means of intelligent identification and data collection. In practical applications, the card reader, as a crucial component of the RFID system, directly affects the system's identification efficiency, coverage, and anti-interference capabilities.

[0003] Existing RFID readers typically employ a single-channel design, meaning they support only one antenna coil for signal transmission and reception. While this design is structurally simple, it suffers from the following problems in practical applications:

[0004] Limited coverage: Single-channel card readers have a small antenna coverage area, making it difficult to meet the application needs of multiple directions or multiple areas. For example, in large warehouse management systems, multiple card readers need to be deployed to achieve coverage of the entire space, increasing equipment costs and installation complexity.

[0005] With limited signal processing capabilities, traditional card readers typically only perform simple amplification and filtering after receiving signals, lacking an efficient multi-level signal conditioning mechanism, resulting in low decoding accuracy, especially under weak signal conditions. Utility Model Content

[0006] The purpose of this invention is to provide a four-channel card reader to solve the technical problems of limited coverage and insufficient signal processing capability of existing single-channel card readers.

[0007] To achieve the above objectives, this utility model provides a four-channel card reader, including a transmitting circuit, a receiving circuit, and a microcontroller U15. The transmitting circuit is a push-pull circuit composed of transistors Q10 and Q2, used to drive the antenna coil to generate an electromagnetic field.

[0008] The receiving circuit includes antenna coils L3, L4, L5, and L6; operational amplifiers U6, U7, U12, and U13 for amplifying the signals from the four antenna coils; an RF conditioner U16 for conditioning the four RF signals; and a two-stage amplification and filtering circuit.

[0009] The microcontroller U15 generates a carrier signal through its SOUT pin, acquires and receives signals through its SIN pin, and transmits the decoded UID data through its UART interface.

[0010] By using four independent antenna coils and their corresponding amplification and conditioning circuits, parallel processing of multiple signals is achieved, improving signal reception sensitivity and anti-interference capability. The two-stage amplification and filtering circuit effectively enhances the processing capability of weak signals and improves decoding accuracy. It also expands the signal coverage range to meet the application needs of multiple directions and regions. At the same time, the microcontroller integrates carrier generation, signal sampling, decoding, and data transmission functions, simplifying the system structure and enhancing the reliability and practicality of the device. This solves the problems of limited coverage and insufficient signal processing capability of traditional single-channel card readers, making it suitable for efficient identification and data acquisition in complex scenarios.

[0011] Furthermore, transistor Q10 is an NPN transistor, and transistor Q2 is a PNP transistor. The emitter of transistor Q10 is connected to the emitter of transistor Q2 in sequence through resistors R32 and R42. Transistors Q10 and Q2 share a common base and are connected to the SOUT port of microcontroller U15 through resistor R48.

[0012] The push-pull circuit efficiently converts the square wave signal output by the microcontroller U15 into a carrier signal with a larger amplitude, enhancing the driving capability of the antenna coil, thereby generating a stronger electromagnetic field and expanding the signal coverage. The common-base connection of the transistor effectively improves the switching speed and stability of the circuit and reduces signal distortion. The reasonable configuration of resistors R32, R42, and R48 not only optimizes the current distribution but also reduces power consumption, enhances the reliability and anti-interference capability of the circuit, thereby further improving the overall efficiency and practicality of the card reader.

[0013] Furthermore, the secondary amplification and filtering circuit includes operational amplifier U3 and operational amplifier U4. The output terminal of operational amplifier U3 is connected to the non-inverting input terminal of operational amplifier U4 in sequence through capacitor C8, resistor R20, and operational amplifier U4. Operational amplifier U3 and operational amplifier U4 form a secondary amplification circuit for amplifying and filtering the received signal. The output terminal of the RF conditioner U16 is connected to the non-inverting input terminal of operational amplifier U3 in sequence through resistor R28, diode D10, and resistor C13. The output terminal of operational amplifier U4 is connected to the SIN pin of microcontroller U15.

[0014] After the RF conditioner U16 performs initial conditioning on the multi-antenna signals, it rectifies the signals through diode D10 and filters them with capacitor C13, effectively improving the signal-to-noise ratio. Operational amplifier U3, as the first-stage amplifier, initially amplifies the rectified signal, enhancing the detectability of weak signals. Operational amplifier U4, as the second-stage amplifier, further amplifies the signal and filters out high-frequency noise, ensuring the stability and purity of the output signal. Capacitor C8 and resistor R20 optimize signal coupling and amplification, reducing signal distortion. Finally, the signal, after two stages of amplification and filtering, is input to the SIN pin of microcontroller U15, significantly improving the accuracy and reliability of signal decoding, thereby enhancing the reader's recognition performance and anti-interference capability in complex environments.

[0015] The beneficial effects of this utility model are:

[0016] By using four independent antenna coils and their corresponding amplification and conditioning circuits, parallel processing of multiple signals is achieved, improving signal reception sensitivity and anti-interference capability. The two-stage amplification and filtering circuit effectively enhances the processing capability of weak signals and improves decoding accuracy. It also expands the signal coverage range to meet the application needs of multiple directions and regions. At the same time, the microcontroller integrates carrier generation, signal sampling, decoding, and data transmission functions, simplifying the system structure and enhancing the reliability and practicality of the device. This solves the problems of limited coverage and insufficient signal processing capability of traditional single-channel card readers, making it suitable for efficient identification and data acquisition in complex scenarios. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Among them:

[0018] Figure 1 The push-pull circuit diagram of the four-channel card reader provided by this utility model.

[0019] Figure 2 The circuit diagram of the diode amplifier in the four-channel card reader provided by this utility model.

[0020] Figure 3 The microcontroller, signal conditioner, and peripheral circuit diagram of the four-channel card reader provided by this utility model. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining this utility model and are not intended to limit this utility model.

[0022] See Figures 1 to 3 This utility model provides a four-channel card reader. The transmitting circuit includes transistors Q10 and Q2. Transistor Q10 is an NPN transistor and transistor Q2 is a PNP transistor, which is used to drive the antenna coil.

[0023] The SOUT pin of the microcontroller U15 outputs a 125kHz square wave signal, which drives transistors Q10 and Q2 after passing through resistor R48.

[0024] Transistors Q10 and Q2 form a push-pull circuit, generating a 125kHz carrier signal with a large amplitude, which is transmitted outward through the antenna coil and connected to the antenna at connector SIG.

[0025] The antenna coil is connected between the emitters of transistors Q10 and Q2 to transmit an electromagnetic field of 125 kHz.

[0026] The four-channel conditioning circuit includes antenna coils L3, L4, L5, and L6. It also includes operational amplifiers U6, U7, U12, and U13 to amplify the four antenna coils, and an RF conditioner U16 to condition the four RF signals. After conditioning, the signals are connected to connector SIG through two output ports SIG2.

[0027] Receiver circuit

[0028] ID card response signal:

[0029] When the ID card enters the antenna's magnetic field, the LC oscillation circuit inside the ID card is activated, changing the impedance of the antenna coil through load modulation.

[0030] This change causes a change in the antenna coil current, forming a modulation signal.

[0031] Signal conditioning:

[0032] The received signal is sequentially converted from an AC signal to a unidirectional pulse signal by the radio frequency conditioner U16 and the diode D10.

[0033] The rectified signal is further smoothed by an RC filter circuit consisting of resistor R27 and capacitor C11.

[0034] Signal Amplification and Filtering

[0035] The output of operational amplifier U3 is connected in sequence through capacitor C8, resistor R20 and the non-inverting input of operational amplifier U4. Operational amplifiers U3 and U4 form a two-stage amplifier circuit for amplifying and filtering the received signal.

[0036] Operational amplifier U3 acts as the first-stage amplifier, providing initial amplification to the rectified signal. The output of operational amplifier U3 is connected to its inverting input via resistor R24, and the inverting input is grounded via resistor R23. Resistors R23 and R24 are used to set the amplification factor.

[0037] Operational amplifier U4 acts as the second-stage amplifier, further amplifying the signal and filtering out high-frequency noise through a filter circuit composed of C9 and C10. The output signal is then coupled to subsequent circuits for sampling and decoding by microcontroller U15.

[0038] Control and Signal Processing

[0039] Processed by microcontroller U15, its SOUT pin generates a 125kHz carrier signal to drive the transmitting circuit.

[0040] Its SIN pin acquires the received ID card signal and samples it through an internal ADC or digital input.

[0041] The received signal is demodulated and decoded to extract the unique identifier (UID) of the ID card.

[0042] The microcontroller U15 has a UART interface, where the TXD and RXD pins are used to communicate with external devices and send out the decoded UID data through the UART interface.

[0043] Working principle

[0044] initialization:

[0045] Initialize the microcontroller U15 and configure peripherals such as GPIO, UART, and timers.

[0046] Initiate the generation of a 125kHz carrier signal.

[0047] Transmit carrier:

[0048] The microcontroller U15 outputs a 125kHz square wave signal through the SOUT pin to drive transistors Q10 and Q2, generating a 125kHz electromagnetic field.

[0049] Received signal:

[0050] When the ID card enters the magnetic field, the ID card changes the impedance of the antenna coil through load modulation, generating a modulation signal.

[0051] The modulated signal is rectified, filtered, and amplified before being sent to the SIN pin of the microcontroller U15.

[0052] Signal demodulation and decoding:

[0053] The microcontroller U15 samples the signal from the SIN pin via an ADC or digital input, performs demodulation and decoding, and extracts the UID of the ID card.

[0054] Data transmission:

[0055] The decoded UID data is sent to an external device via the UART interface (TXD and RXD).

[0056] The beneficial effects of this utility model are:

[0057] By using four independent antenna coils and their corresponding amplification and conditioning circuits, parallel processing of multiple signals is achieved, improving signal reception sensitivity and anti-interference capability. The two-stage amplification and filtering circuit effectively enhances the processing capability of weak signals and improves decoding accuracy. It also expands the signal coverage range to meet the application needs of multiple directions and regions. At the same time, the microcontroller integrates carrier generation, signal sampling, decoding, and data transmission functions, simplifying the system structure and enhancing the reliability and practicality of the device. This solves the problems of limited coverage and insufficient signal processing capability of traditional single-channel card readers, making it suitable for efficient identification and data acquisition in complex scenarios.

[0058] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A four-channel card reader, characterized in that, It includes a transmitting circuit, a receiving circuit, and a microcontroller U15. The transmitting circuit is a push-pull circuit composed of transistors Q10 and Q2, which is used to drive the antenna coil to generate an electromagnetic field. The receiving circuit includes antenna coils L3, L4, L5, and L6; operational amplifiers U6, U7, U12, and U13 for amplifying the signals from the four antenna coils; an RF conditioner U16 for conditioning the four RF signals; and a two-stage amplification and filtering circuit. The microcontroller U15 generates a carrier signal through its SOUT pin, acquires and receives signals through its SIN pin, and transmits the decoded UID data through its UART interface.

2. The four-channel card reader according to claim 1, characterized in that, The transistor Q10 is an NPN transistor, and the transistor Q2 is a PNP transistor. The emitter of the transistor Q10 is connected to the emitter of the transistor Q2 in sequence through resistors R32 and R42. The transistors Q10 and Q2 share a common base and are connected to the SOUT port of the microcontroller U15 through resistor R48.

3. The four-channel card reader according to claim 1, characterized in that, The secondary amplification and filtering circuit includes operational amplifiers U3 and U4. The output terminal of operational amplifier U3 is connected to the non-inverting input terminal of operational amplifier U4 in sequence through capacitor C8, resistor R20, and operational amplifier U4. Operational amplifiers U3 and U4 form a secondary amplification circuit for amplifying and filtering the received signal. The output terminal of the RF conditioner U16 is connected to the non-inverting input terminal of operational amplifier U3 in sequence through resistor R28, diode D10, and resistor C13. The output terminal of operational amplifier U4 is connected to the SIN pin of microcontroller U15.

Images