Magnetic card point-to-point communication terminal and group intercom method thereof

Abstract

The application discloses a magnetic card point-to-point communication terminal and a group intercom method thereof. The terminal has a card-shaped shell, a magnetic array, a license-free sub-GHz frequency band radio frequency transceiver circuit, a short-distance communication circuit, a processor and a power supply circuit. The magnetic array adsorbs the terminal on the back of a mobile terminal; the short-distance communication circuit establishes a short-distance wireless link with the mobile terminal; and the radio frequency transceiver circuit establishes a point-to-point direct communication link with a terminal at the other end without a base station, a gateway and other infrastructures. The processor sends service data such as audio, pictures, positions and text messages of the mobile terminal to group terminals at the other end in a group broadcast mode and returns the mobile terminal to play and display. Magnets are arranged around an antenna clearance area to suppress the degradation of the radio frequency performance of the magnetic adsorption component. The terminal does not contain an audio component and is used as a long-distance voice modem of the mobile terminal, the thickness of the terminal is not greater than 5 mm, real-time communication of a small team under the condition without infrastructures is realized, and the terminal has the advantages of portability and low loss rate.

Description

Technical Field

[0001] This invention relates to the field of wireless communication and mobile terminal accessories technology, specifically to a card-type point-to-point communication terminal that can be magnetically attached to the back of a mobile terminal, and a group talk method based on the terminal. Background Technology

[0002] With the increasing demand for outdoor sports, group travel, and emergency communication, the communication failure of mobile terminals in areas without cellular network coverage (mountainous areas, sea areas, wilderness, large event venues, etc.) is becoming increasingly prominent. Existing technical solutions have the following shortcomings: Firstly, the direct satellite communication solution for mobile phones is costly, requires a monthly subscription fee, and uses a store-and-forward mechanism, resulting in message sending and receiving delays on the order of minutes. It cannot support real-time group voice communication and is difficult to meet the immediacy requirements of small team collaboration scenarios.

[0003] Secondly, although traditional walkie-talkies (such as FRS / GMRS / DMR systems) can communicate in real time, they are bulky, need to be carried independently, are disconnected from the smartphone ecosystem, and lack intelligent business capabilities such as group digital management and image and location data transmission. Furthermore, antenna performance is limited by the size of the device.

[0004] Third, existing mobile phone companion-type off-network communication devices (represented by text messaging devices based on LoRa technology) only support text message transmission and do not support real-time voice communication; they are mostly stick-shaped or independent small boxes, which are carried separately from the mobile phone and are easily lost or forgotten in outdoor scenarios.

[0005] Fourth, existing magnetic mobile phone accessories (magnetic card holders, magnetic Bluetooth earpieces, etc.) only provide storage, business card exchange, or near-field audio functions, with communication distance limited to the Bluetooth range (tens of meters), lacking long-distance communication capabilities. Furthermore, the magnetic array magnets in these accessories, along with the metal and magnetic components inside the phone being attracted, significantly degrade the radiation efficiency of the internal radio frequency antenna, and current designs do not offer solutions to this problem.

[0006] Therefore, the industry needs a communication terminal that not only has long-distance, license-free, real-time group voice communication capabilities, but also is deeply integrated with smartphones, portable, and not easily lost. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a magnetic card point-to-point communication terminal and its group intercom method.

[0008] The present invention adopts the following technical solution to achieve the above objectives: a magnetic card point-to-point communication terminal, comprising a card-shaped shell, a magnetic array, a radio frequency transceiver circuit, a first antenna, a short-range communication circuit, a second antenna, a processor, and a power supply circuit (see claim 1 for details).

[0009] Furthermore, the thickness of the card-shaped shell is no more than 5mm, and its length and width dimensions are consistent with the ISO 7810 ID-1 standard card or compatible with the magnetic accessories of the mobile terminal (claim 2); multiple magnets of the magnetic array are arranged around the periphery of the clearance area of ​​the first antenna radiator and maintain a minimum spacing to suppress the coupling degradation between the magnets and the metal parts inside the attracted mobile phone (claims 3, 4); the terminal is equipped with an adsorption status detection sensor, which switches between the intercom working mode and the independent duty mode accordingly, and listens for and caches service data at a low duty cycle during the duty period (claim 5); the radio frequency link adopts time division duplex and ultra-low code rate voice coding, combined with inter-data packet frequency hopping and channel self-learning (claims 6, 7); the terminal does not contain audio acquisition and playback components and is used as a voice modem for the mobile terminal (claim 8); the power circuit supports USB Type-C charging and reverse power supply of the mobile terminal OTG, and / or receives reverse wireless charging power through the wireless charging receiving coil in the central area of ​​the magnetic array, and the magnetic array, wireless charging receiving coil and antenna radiator are arranged in separate zones without overlapping (claim 9).

[0010] Accordingly, the present invention also provides a group intercom method based on the above-mentioned terminal, including steps such as service data delivery, time-slotted group broadcast transmission, peer backhaul and independent monitoring cache synchronization (claim 10), and further includes preferred steps such as dynamic adjustment of time slot ratio (claim 11), combination of low-power Bluetooth short-range link and unlicensed sub-GHz band, and group security pairing and authentication encryption (claim 12).

[0011] The beneficial technical effects of this invention include: (1) Dual-link converged architecture: Short-range communication links (such as Bluetooth Low Energy) are used as the control plane and human-machine interaction plane, and sub-GHz point-to-point direct links are used as the data plane. This allows the interactive capabilities of smartphones to complement the long-range radio frequency capabilities of card terminals. Users can complete long-range group intercom and image transmission through mobile applications without carrying separate intercom equipment. The card is attached to the back of the phone and carried with the phone, significantly reducing the loss rate. The terminal itself does not contain audio components and works as a long-range voice modem for mobile terminals, breaking away from the form constraints of walkie-talkies with "built-in microphones and speakers". The thickness of the whole device can be controlled within 5mm and the weight is comparable to that of a card.

[0012] (2) Design of coexistence of magnet and antenna: Multiple magnets of the magnetic array are arranged around the periphery of the first antenna radiator clearance area, maintaining the minimum distance between the magnet and the radiator and making the magnet projection outside the near field area of ​​the radiator, suppressing the degradation of the sub-GHz antenna radiation efficiency by the magnet and the metal parts inside the mobile phone that are adsorbed, thereby achieving a communication distance of kilometers under the dual constraints of card size and magnetic function.

[0013] (3) Independent monitoring and cache synchronization: The communication terminal can independently monitor the group channel and cache service data when the mobile phone screen is locked or the application is in the background. Synchronize after the mobile phone resumes interaction to avoid missing group calls and messages.

[0014] (4) Real-time group voice communication in unlicensed frequency bands: Through time-slotted transmission, ultra-low bit rate voice encoding, frequency hopping between data packets and co-channel broadcasting, real-time group voice communication for multiple users can be realized in unlicensed frequency bands without network infrastructure dependence or subscription fees. Attached Figure Description

[0015] Figure 1 is a schematic diagram of the overall structure of the communication terminal provided in an embodiment of the present invention (the terminal is attached to the back of the mobile terminal in a vertical orientation); Figure 2 is a block diagram of the circuit module in an embodiment of the present invention; Figure 3 is a schematic diagram of the layout relationship between the magnetic array and the first antenna (vertical view); Figure 4 is a flowchart of the group intercom method; Figure 5 is a schematic diagram of the time-slotted channel structure. Detailed Implementation

[0016] The present invention will be further described below with reference to the embodiments.

[0017] Example 1: Terminal Hardware Structure. See Figures 1 to 3. The card-shaped housing measures 85.6mm × 54mm × 4.0mm (the overall thickness can be controlled between 3.5 and 4.5mm due to the absence of audio components), and uses an aluminum alloy frame and a fiberglass composite panel. The magnetic array consists of several N52 neodymium iron boron magnets, arranged in a ring around the perimeter of the housing, its layout matching the magnetic adsorption positions of mainstream mobile terminals; the central area of ​​the housing enclosed by the magnetic array is used to arrange the wireless charging receiving coil (if installed), and the clearance area of ​​the first antenna is set along the long side of the housing. In typical use, the terminal is attached to the back of the mobile terminal with its long side parallel to the long side of the mobile terminal, adapting to the hand shape of the user holding the mobile terminal with one hand, making it easy to hold and pick up; the first antenna radiator runs along the long vertical side, away from the metal components and wireless charging devices inside the mobile terminal, further reducing coupling effects. The RF transceiver circuit employs a sub-GHz transceiver system-on-a-chip operating in the unlicensed 902-928MHz frequency band (it can use TurMass-style DPFSK modulation, time-division duplex, and unlicensed random access schemes, or other equivalent sub-GHz schemes), with a maximum transmit power not exceeding 22dBm, meeting the requirements of FCC Part 15.247 for frequency-hopping spread spectrum systems. When targeting other regional markets, the RF front-end and antenna can be adapted to tune to unlicensed sub-GHz frequency bands permitted by local regulations, such as 433MHz and 868MHz. The first antenna is a flexible circuit board antenna, with the radiator running along the long side of the housing and located within the clearance area. The magnetic circuit directions of multiple magnets are consistent, and the projections of each magnet on the housing are located outside the near-field region of the radiator, with a minimum distance between the magnet and the radiator not less than a preset value (exemplarily not less than 5mm) to suppress the coupling effect between the magnet and the metal components inside the attracted mobile phone. The short-range communication circuit is a BLE 5.0 chip, and the second antenna is an inverted F-type Bluetooth antenna. The terminal itself does not have a microphone, speaker, or audio codec components. All voice acquisition, playback, and encoding / decoding are handled by the mobile terminal's application. The terminal only handles voice modulation / demodulation and radio frequency transmission, minimizing the overall thickness and weight (the overall weight is, for example, no more than 35g). The power circuit includes a 500mAh (400 to 600mAh range) lithium polymer battery and a charging management circuit. The charging interface is USB Type-C, and the charging management circuit supports reverse charging via the mobile terminal's USB OTG. Some models may have a wireless charging receiving coil located in the central area enclosed by the magnetic array, not overlapping with the first antenna radiator section, used to receive the reverse wireless charging power output by the mobile terminal in the adsorption state. The magnetic array also serves as the alignment structure for wireless charging and adsorption. The adsorption state detection sensors include a Hall sensor and a triaxial accelerometer, used to detect the adsorption state and attitude.

[0018] Example 2: Group Intercom and Image Transmission Method. See Figures 4 and 5. The radio frequency link uses time-division duplex, with a time slot length of 20ms as an example. Voice is encoded and encapsulated into voice data packets at a bit rate of no more than 0.5kbps and transmitted in the data time slot; the physical frame includes beacon time slots and data time slots. The group uses a shared-channel broadcast: the transmitter sends with one click, and all member terminals in the group receive on the same channel, achieving single transmission and full group listening; carrier sensing and collision avoidance are performed before transmission. The terminal performs frequency hopping between data packets, with no less than 300 available channels, and converges to the frequency band with the least interference based on channel quality through self-learning. For example, an 8-person group can achieve clear voice communication of no less than 5km in open areas, 2 to 5km in mountainous areas, and 1 to 3km in urban areas, with an end-to-end latency of no more than 300ms. The transmitter dynamically adjusts the time slot allocation and transmission duty cycle according to the group size and channel occupancy status, taking into account both latency and power consumption. Image service: The terminal divides the compressed image sent by the mobile terminal into data packets, and transmits them with a lower priority than voice during the channel idle period. After verification and reconstruction by the receiving end, the data is sent back to the mobile terminal for display via a short-range communication link. The location data of group members and short messages are also carried in the same low-priority data packet manner.

[0019] Example 3: Working Mode Switching. The processor switches the working mode based on the output of the adsorption state detection sensor: In the adsorption state, it enters intercom mode, enabling intercom, group management, and data services via the mobile application; after detecting separation for more than a preset time (exemplarily 30 seconds), it enters independent monitoring mode, where the RF transceiver circuit listens to the group broadcast channel with a low duty cycle and buffers received audio data; upon re-detection of adsorption, the buffered data is synchronized to the mobile phone via a short-range link. When the mobile phone is locked or the application is in the background, the terminal also enters independent monitoring mode to ensure no group calls are missed.

[0020] Example 4: Secure Group Pairing and Authentication. When a user creates or joins a group in a mobile terminal application, the application generates or obtains a group identifier, pairing key, and group configuration information (member list, working channel, and frequency hopping sequence parameters, etc.), which is then transmitted to the attached communication terminal via a Bluetooth Low Energy link and stored in the terminal's non-volatile memory. The communication terminal authenticates members within the group on a shared channel based on the pairing key and group configuration information, and performs encryption and decryption on the service data broadcast by the group (exemplarily using AES-128 symmetric encryption). When a new member joins the group, the group administrator initiates key distribution on the application side; when a member leaves or their card is lost, the application side updates the group key and pushes it to all terminals within the group, rendering the old key invalid. The distribution and updating of the key and group configuration are all completed locally via a short-range communication link, requiring no network connection throughout, consistent with the infrastructure-free operation characteristics of the terminal.

[0021] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. All equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0022] 100 — Communication Terminal (Magnetic Card Point-to-Point Communication Terminal) 10 - Card-shaped casing 20 - Magnetic Array 21—Magnet 30—RF transceiver circuit 31—First antenna (radiator) 32 — Antenna clearance area 40—Short-range communication circuit 41 - The Second Line 50 — Processor 60—Power Supply Circuit 61 - Built-in rechargeable battery 62—Charging Management Circuit 63—USB Type-C charging port 64—Wireless charging receiver coil 70—Adsorption State Detection Sensor 200—Mobile Terminal 210 - Application 300 — peer communication terminal.

Claims

1. A magnetic card-based point-to-point communication terminal, characterized in that, include: Card-shaped housing; magnetic array, disposed inside the card-shaped housing, for detachably attaching the communication terminal to the back of the mobile terminal; A radio frequency transceiver circuit, housed within the card-shaped housing, operates in the unlicensed sub-GHz band and is used to establish a point-to-point direct communication link with a peer communication terminal of the same type. This point-to-point direct communication link does not rely on base stations, gateways, or satellite infrastructure. A first antenna, electrically connected to the radio frequency transceiver circuit, is housed within the card-shaped housing and avoids the area occupied by the magnet in the magnetic array. A short-range communication circuit, also housed within the card-shaped housing, is used to establish a short-range wireless communication link with the mobile terminal. A second antenna is electrically connected to the short-range communication circuit. A processor, coupled to both the radio frequency transceiver circuit and the short-range communication circuit, is configured to: receive service data and control commands transmitted by the mobile terminal via the short-range wireless communication link; the service data includes audio data, image data, location data, and / or text message data; and, in response to an intercom trigger command, transmit the service data via the point-to-point direct communication link in a group broadcast manner to at least one peer communication terminal. In addition, the service data received from the peer communication terminal via the point-to-point direct communication link is transmitted back to the mobile terminal via the short-range wireless communication link for playback, display and presentation; and a power supply circuit is disposed in the card-shaped housing to supply power to the above circuits.

2. The terminal according to claim 1, characterized in that, The thickness of the card-shaped housing is no more than 5mm, and its length and width dimensions are consistent with the dimensions of the ISO 7810 ID-1 standard card or adapted to the dimensions of the magnetic accessories for mobile terminals.

3. The terminal according to claim 1, characterized in that, The magnetic array includes multiple magnets arranged in a ring or distributed manner around the periphery of the radiator clearance area of ​​the first antenna. Each magnet maintains a preset minimum distance from the radiator of the first antenna to suppress the coupling effect of the magnets and the metal components inside the attracted mobile terminal on the radiation performance of the first antenna.

4. The terminal according to claim 3, characterized in that, The first antenna is a flexible circuit board antenna or a laser-formed antenna, and its radiator is routed along the long side of the card-shaped housing; the magnetic circuit directions of the plurality of magnets are consistent, and the projection of each magnet on the card-shaped housing is located outside the near field region of the radiator.

5. The terminal according to claim 1, characterized in that, It also includes an adsorption state detection sensor, disposed within the card-shaped housing, for detecting whether the terminal is adsorbed onto the mobile terminal; the processor is further configured to: control the terminal to enter an intercom working mode when an adsorption state is detected; control the terminal to enter an independent monitoring mode after a separation state has been detected for a preset duration; in the independent monitoring mode, the radio frequency transceiver circuit listens to the group broadcast channel with a low duty cycle and buffers the received service data, and after the adsorption state is detected again, synchronizes the buffered service data to the mobile terminal.

6. The terminal according to claim 1, characterized in that, The radio frequency transceiver circuit operates in time-division duplex mode. Voice data is encapsulated into voice data packets at a coding rate of no more than 0.5 kbps and transmitted in a time-slotted channel. The processor is further configured to perform inter-data packet frequency hopping and self-learn to converge to the frequency band with the least interference based on channel quality.

7. The terminal according to claim 1, characterized in that, The group broadcast is a shared-channel broadcast, in which each communication terminal in the same group receives the voice data of the group members on the same channel, so as to achieve single transmission and full group listening; the processor performs carrier sensing and collision avoidance processing before sending voice data packets.

8. The terminal according to claim 1, characterized in that, The terminal does not include an audio acquisition component or an audio playback component; all voice acquisition and playback are performed by the mobile terminal. The terminal serves as a voice modem between the mobile terminal and the point-to-point direct communication link.

9. The terminal according to claim 1, characterized in that, The power circuit includes a built-in rechargeable battery and a charging management circuit. The built-in rechargeable battery has a capacity of 400 to 600 mAh. The terminal is equipped with a USB Type-C charging port. The charging management circuit supports charging via USB OTG reverse power supply from the mobile terminal. And / or, the terminal is equipped with a wireless charging receiving coil located in the central area enclosed by the magnetic array, used to receive the reverse wireless charging power output by the mobile terminal in an attracted state. The magnetic array, the wireless charging receiving coil, and the radiator of the first antenna are arranged in sections within the card-shaped housing and do not overlap.

10. A group intercom method based on the terminal according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. The first mobile terminal sends a talk request and service data to the communication terminal via a short-range communication link attached to it. The service data includes audio data, image data, location data and / or text message data. S2. The communication terminal encodes and encapsulates the audio data into voice data packets, compresses and packets the image data into image data packets, and encapsulates the location data and text message data into message data packets. These are then sent via a point-to-point direct communication link to at least one peer communication terminal within the group via group broadcast. The time slot scheduling priority of image data packets and message data packets is lower than that of voice data packets to ensure the real-time performance of the voice intercom. S3. The peer communication terminal receives and processes the data packets. Through a short-range communication link between itself and the attached second mobile terminal, the processed service data is transmitted to the second mobile terminal for playback, display, and presentation. S4. When the first mobile terminal is in a locked screen state or the communication application is in the background, the communication terminal it is attached to enters an independent monitoring mode, listens to the group broadcast channel with a low duty cycle and caches the received service data. After the first mobile terminal resumes interaction, the cached data is synchronized to the first mobile terminal.

11. The method according to claim 10, characterized in that, In step S2, the communication terminal at the transmitting end dynamically adjusts the time slot allocation and transmission duty cycle according to the group size and channel occupancy status, so as to reduce power consumption while ensuring that the end-to-end delay of the group voice is not greater than a preset threshold.

12. The method according to claim 10, characterized in that, The short-range communication link is a Bluetooth Low Energy link, and the point-to-point direct communication link operates in the 902-928MHz unlicensed frequency band or other unlicensed sub-GHz frequency bands permitted by regional regulations; the method also includes a group secure pairing step: each communication terminal obtains the pairing key and group configuration information from the mobile terminal it has attracted through its own Bluetooth Low Energy link, and thereby completes the authentication and encryption of members within the group.

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