阅读说明：本技术 一种具有同频中继功能的车载对讲机 (Vehicle-mounted interphone with same-frequency relay function ) 是由 林志忠 黄印杰 徐庆林 魏新波 魏理俊 董清华 于 2019-09-30 设计创作，主要内容包括：本发明公开了一种具有同频中继功能的车载对讲机,其包括天线端口、收发开关电路、接收选频电路、功率放大电路、发射射频单元、接收射频单元、数字基带单元、编解码单元、外部时钟电路、微处理器和电源单元。本车载对讲机解决了以往需要两台机器分别用于接收和发射、一个双工器和至少一根天线,并且需要申请两个频率的传统的中继台架设方案的限制,实现了同频中继功能。本车载电台简化至只需要一台车载对讲机配上一根天线就可实现同频中继功能,相对于传统的异频中继台即节省频率资源、节约购买资金,同时频点选择不需要受到双工器频率带宽的限制,操作简便、通信高效有保障。(The invention discloses a vehicle-mounted interphone with a same-frequency relay function, which comprises an antenna port, a transceiving switch circuit, a receiving frequency selection circuit, a power amplification circuit, a transmitting radio frequency unit, a receiving radio frequency unit, a digital baseband unit, a coding and decoding unit, an external clock circuit, a microprocessor and a power supply unit. The vehicle-mounted interphone solves the problem that two sets of interphone are required to be used for receiving and transmitting respectively, a duplexer and at least one antenna are required in the past, and the limitation of a traditional relay station erection scheme of two frequencies is required to be applied, so that the same-frequency relay function is realized. The vehicle-mounted radio station is simplified to the condition that the same-frequency relay function can be realized only by matching one vehicle-mounted interphone with one antenna, so that compared with the traditional pilot frequency relay station, frequency resources and purchase funds are saved, meanwhile, the frequency point selection is not limited by the frequency bandwidth of a duplexer, the operation is simple and convenient, and the high-efficiency communication is guaranteed.)

1. A vehicle-mounted interphone with the same-frequency relay function is characterized in that a host circuit of the vehicle-mounted interphone comprises an antenna port, a transceiving switch circuit, a receiving frequency selection circuit, a power amplification circuit, a transmitting radio frequency unit, a receiving radio frequency unit, a digital baseband unit, a coding and decoding unit, an external clock circuit, a microprocessor, a power supply unit and a key unit; the method is characterized in that:

the power supply unit provides a working power supply for the whole vehicle-mounted interphone;

the key unit is connected with the corresponding input end of the microprocessor;

the microprocessor is in communication connection with the transmitting radio frequency unit, the receiving radio frequency unit and the digital baseband unit respectively; a same-frequency relay software module is programmed in the microprocessor, a same-frequency relay functional firmware is arranged in the digital baseband unit, and the same-frequency relay software module and the same-frequency relay functional firmware are mutually interacted to realize a software part of same-frequency relay;

the antenna port is sequentially connected with the transceiving switch circuit, the receiving frequency selection circuit, the receiving radio frequency unit and the coding and decoding unit, and the digital baseband unit is bidirectionally connected with the coding and decoding unit; the receiving channel is composed of an antenna port, a receiving and transmitting switch circuit, a receiving frequency selection circuit, a receiving radio frequency unit, a coding and decoding unit and a digital baseband unit;

the digital signal output end of the coding and decoding unit is sequentially connected with an external clock circuit, a transmitting radio frequency unit, a power amplifying circuit, a receiving and transmitting switch circuit and an antenna port; the transmitting channel is composed of a coding and decoding unit, a digital baseband unit, an external clock circuit, a transmitting radio frequency unit, a power amplifying circuit, a receiving and transmitting switch circuit and an antenna port;

the vehicle-mounted interphone is used as a relay party, and the relay party realizes the relay function in the following way:

s1: the relay enters the menu by operating the key unit of the relay, and the receiving and transmitting channel state of the relay is set in the menu, namely the working frequency and the working type of two radio frequency channels for relay receiving and transmitting are edited, so that the two radio frequency channels work at the same frequency and are in a digital mode;

s2: and starting the same-frequency relay function in the corresponding option in the menu of the relay party, and then the relay party works in the same-frequency relay mode according to the previously set transceiving channel state:

one of the two radio frequency channels works in a receiving state, the other one works in a transmitting state, only initialization is carried out at the moment, a transmitting power supply is not switched on to start transmitting, no power output exists, and the actual power output exists only when a signal is received; the microprocessor sends a call setting instruction to the digital baseband unit to set the digital baseband unit to work in a same-frequency relay mode, does not process conventional signals, and identifies and forwards a leading frame, a voice frame, a superframe and a tail frame in the digital call in any time slot;

s3: the vehicle-mounted interphones used as the sender and the receiver are respectively opened with a direct through double time slot function through the key units of the vehicle-mounted interphones; simultaneously, the transmitting frequency point of the transmitting party and the receiving frequency point of the receiving party are set to be the same as the receiving and transmitting frequency point of the relaying party through respective key units, and the transmitting and receiving are respectively and fixedly selected to be two different time slots through respective key units entering a menu;

the method comprises the steps that a sender executes digital transmission operation, converts audio signals entering a microphone of the sender into digital signals after a series of compression, encryption, coding and modulation, the digital signals enter an analog baseband unit through an external clock circuit to generate digital radio frequency signals, enter a transceiving switch circuit after being amplified through a power amplification circuit and are transmitted out through an antenna port of the transceiving switch circuit;

s4: the repeater receives a signal which is sent by a sender and has the same receiving time slot as the repeater from an antenna port, enters a receiving frequency selection circuit through a transceiving switch circuit for frequency selection and amplification, then is demodulated into a 4FSK signal by a receiving radio frequency unit, the digital baseband unit analyzes the reported data of the current 4FSK signal and sends the data to a microprocessor to identify the current working time slot, then the microprocessor sends a calling time slot setting instruction to the digital baseband unit to control the digital baseband unit to work, and switches the receiving from any time slot to the receiving of the current time slot, and stores the received current time slot data in a data buffer area of the digital baseband unit, and then the received current time slot data passes through a coding and decoding unit, the digital baseband unit, an external clock circuit, a transmitting radio frequency unit, a power amplification circuit and a transceiving switch circuit in the next time slot;

s5: in the forwarding process, the digital baseband unit of the relay party generates a level signal of 30MS hopping once to the microprocessor of the relay party according to the requirements of the DMR protocol to process the transceiving of DMR data: the microprocessor sends a carrier wave disappearance instruction and a calling time slot setting instruction to the digital baseband unit until the received signal disappears, thereby ending the relay state and returning to the standby state;

s6: the receiver sets the same relay frequency point and the same receiving time slot as the transmitting time slot of the relay to receive the digital signal of the sender transmitted by the relay, the digital signal received by the receiver from the antenna port enters the receiving circuit through the receiving and transmitting switch circuit, then is demodulated through the analog baseband to generate a demodulated signal and enters the audio codec unit to be converted into a digital form, then the demodulated signal is subjected to a series of demodulation, extraction and decryption through the digital baseband unit to reconstruct the voice signal, and the reconstructed voice signal enters the voice codec unit to be converted into an analog signal and then is played through the loudspeaker of the voice codec unit.

2. The vehicle-mounted interphone with the same-frequency relay function according to claim 1 is characterized in that: the power amplification circuit comprises a push-stage automatic power control unit and a final-stage power control unit, wherein the push-stage automatic power control unit comprises a standing wave detection circuit, a detection circuit, an amplifier, a comparator and a push-stage power amplifier; the final power control unit comprises a final power amplifier and a buffer amplifier; in the push-stage automatic power control unit, the standing wave detection circuit is connected with the detection circuit, the amplifier, the comparator and the push-stage power amplifier in sequence, and a control port of the microprocessor is connected with an input end of the comparator; in the final power control unit, a control port of the microprocessor is connected to an input of the buffer amplifier, and an output of the buffer amplifier is connected to an input of the final power amplifier.

3. The vehicle-mounted interphone with the same-frequency relay function according to claim 1 is characterized in that: the transmitting radio frequency unit and the receiving radio frequency unit are integrated radio frequency transceiving chips, and phase-locked loop circuits are arranged in the transmitting radio frequency unit and the receiving radio frequency unit and are used for transmitting and receiving independently.

4. The vehicle-mounted interphone with the same-frequency relay function according to claim 2 is characterized in that: the push-stage automatic power control unit and the final-stage power control unit are synchronously set by the microprocessor, and the push-stage automatic power control unit and the final-stage power control unit are independently controlled by the microprocessor respectively.

5. The vehicle-mounted interphone with the same-frequency relay function according to claim 2 is characterized in that: the amplifier and the comparator in the push-level automatic power control unit both adopt an operational amplifier with high performance and low power consumption of Saint Band microelectronics, the model is SGM8272YMS8G, and the operational amplifier has a high conversion rate of 7V/us.

6. The vehicle-mounted interphone with the same-frequency relay function according to claim 2 is characterized in that: the buffer amplifier in the final-stage automatic power control unit adopts a Saint Pamp microelectronic high-performance operational amplifier with the model of SGM8535BYN5G, and the operational amplifier has wide input common-mode voltage and excellent output voltage swing.

7. The vehicle-mounted interphone with the same-frequency relay function according to claim 1 is characterized in that: the microprocessor uses an M4 kernel and above microcontroller.

8. The vehicle-mounted interphone with the same-frequency relay function according to claim 1 is characterized in that: the digital baseband unit adopts a digital baseband processing chip with the model of SCT 3258.

9. The vehicle-mounted interphone with the same-frequency relay function according to claim 1 is characterized in that: in the power supply unit, the output end of the power supply control circuit of the transmitting radio frequency unit has a tantalum capacitor with excellent service performance.

10. The vehicle-mounted interphone with the same-frequency relay function according to claim 1 is characterized in that: in the power supply unit, a power supply control circuit of the receiving radio frequency unit adopts a Diodes high-performance preset bias transistor, and the model is UMC 5N.

Technical Field

The invention relates to the technical field of vehicle-mounted interphones, in particular to a vehicle-mounted interphone with a same-frequency relay function.

Background

In a wireless intercom system, a relay plays an important role in increasing communication distance and expanding coverage, and is an indispensable important device in the wireless communication system.

The existing relay station usually works in the state of transmitting and receiving different frequencies, and the system composition needs two machines for receiving and transmitting, one duplexer and at least one antenna respectively, and two frequencies need to be applied. This solution has some drawbacks:

(1) the relay function realized by the duplexer is used, and the used frequency is limited due to the narrow bandwidth of the duplexer and must be limited in the frequency bandwidth range of the duplexer;

(2) due to the relay function of the double antennas, the erected antennas have strict requirements, and the erected antennas are difficult to meet in actual use when the erected antennas are required to achieve certain transceiving isolation, so that interference between transceiving is caused, and the communication distance is influenced;

(3) the pilot frequency relay function realized by using the double frequency points needs to apply for 2 frequencies during erection, so that the use cost of a user is increased, and the waste of frequency resources is also caused.

Disclosure of Invention

The invention aims to provide a vehicle-mounted interphone with the same-frequency relay function, which can realize the same-frequency relay function on one vehicle-mounted interphone and effectively overcome various problems caused by the relay through two vehicle-mounted interphones in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

a vehicle-mounted interphone with the same-frequency relay function is characterized in that a host circuit of the vehicle-mounted interphone comprises an antenna port, a transceiving switch circuit, a receiving frequency selection circuit, a power amplification circuit, a transmitting radio frequency unit, a receiving radio frequency unit, a digital baseband unit, a coding and decoding unit, an external clock circuit, a microprocessor, a power supply unit and a key unit;

the power supply unit provides a working power supply for the whole vehicle-mounted interphone;

the key unit is connected with the corresponding input end of the microprocessor;

the microprocessor is in communication connection with the transmitting radio frequency unit, the receiving radio frequency unit and the digital baseband unit respectively; a same-frequency relay software module is programmed in the microprocessor, a same-frequency relay functional firmware is arranged in the digital baseband unit, and the same-frequency relay software module and the same-frequency relay functional firmware are mutually interacted to realize a software part of same-frequency relay;

the antenna port is sequentially connected with the transceiving switch circuit, the receiving frequency selection circuit, the receiving radio frequency unit and the coding and decoding unit, and the digital baseband unit is bidirectionally connected with the coding and decoding unit; the receiving channel is composed of an antenna port, a receiving and transmitting switch circuit, a receiving frequency selection circuit, a receiving radio frequency unit, a coding and decoding unit and a digital baseband unit;

the digital signal output end of the coding and decoding unit is sequentially connected with an external clock circuit, a transmitting radio frequency unit, a power amplifying circuit, a receiving and transmitting switch circuit and an antenna port; the transmitting channel is composed of a coding and decoding unit, a digital baseband unit, an external clock circuit, a transmitting radio frequency unit, a power amplifying circuit, a receiving and transmitting switch circuit and an antenna port;

the vehicle-mounted interphone is used as a relay party, and the relay party realizes the relay function in the following way:

s1: the relay enters the menu by operating the key unit of the relay, and the receiving and transmitting channel state of the relay is set in the menu, namely the working frequency and the working type of two radio frequency channels for relay receiving and transmitting are edited, so that the two radio frequency channels work at the same frequency and are in a digital mode;

s2: and starting the same-frequency relay function in the corresponding option in the menu of the relay party, and then the relay party works in the same-frequency relay mode according to the previously set transceiving channel state:

one of the two radio frequency channels works in a receiving state, the other one works in a transmitting state, only initialization is carried out at the moment, a transmitting power supply is not switched on to start transmitting, no power output exists, and the actual power output exists only when a signal is received; a microprocessor sends a CALL _ OPTION instruction (CALL setting instruction) to a digital baseband unit to set the digital baseband unit to work in a same-frequency relay mode, does not process conventional signals, and identifies and forwards a leading frame, a voice frame, a superframe and a tail frame in digital communication at any time slot and at another time slot;

s3: the vehicle-mounted interphones used as the sender and the receiver are respectively opened with a direct through double time slot function through the key units of the vehicle-mounted interphones; simultaneously, the transmitting frequency point of the transmitting party and the receiving frequency point of the receiving party are set to be the same as the receiving and transmitting frequency point of the relaying party through respective key units, and the transmitting and receiving are respectively and fixedly selected to be two different time slots through respective key units entering a menu;

the method comprises the steps that a sender executes digital transmission operation, converts audio signals entering a microphone of the sender into digital signals after a series of compression, encryption, coding and modulation, the digital signals enter an analog baseband unit through an external clock circuit to generate digital radio frequency signals, enter a transceiving switch circuit after being amplified through a power amplification circuit and are transmitted out through an antenna port of the transceiving switch circuit;

s4: the repeater receives the signal which is sent by the sender and has the same receiving time slot with the repeater from the antenna port, the signal enters a receiving frequency selection circuit through a transceiving switch circuit for frequency selection amplification, then the receiving radio frequency unit demodulates the signals into 4FSK signals, the digital baseband unit analyzes the reported data of the current 4FSK signals to the microprocessor to identify the current working time SLOT, then the microprocessor sends a DMR _ CALL _ SLOT instruction (calling time SLOT setting instruction) to the digital baseband unit to control the digital baseband unit to switch the work from any time SLOT receiving to the current time SLOT receiving, and stores the received current time SLOT data into a data buffer area of the digital baseband unit, then, in the next time slot (another time slot), the signal is forwarded out from the antenna port through the coding and decoding unit, the digital baseband unit, the external clock circuit, the transmitting radio frequency unit, the power amplifying circuit and the transceiving switch circuit;

s5: in the forwarding process, the digital baseband unit of the relay party generates a level signal of 30MS hopping once to the microprocessor of the relay party according to the requirements of the DMR protocol to process the transceiving of DMR data: the microprocessor sends a carrier wave disappearance instruction and a calling time slot setting instruction to the digital baseband unit until the received signal disappears, thereby ending the relay state and returning to the standby state;

s6: the receiver sets the same relay frequency point and the same receiving time slot as the transmitting time slot of the relay to receive the digital signal of the sender transmitted by the relay, the digital signal received by the receiver from the antenna port enters the receiving circuit through the receiving and transmitting switch circuit, then is demodulated through the analog baseband to generate a demodulated signal and enters the audio codec unit to be converted into a digital form, then the demodulated signal is subjected to a series of demodulation, extraction and decryption through the digital baseband unit to reconstruct the voice signal, and the reconstructed voice signal enters the voice codec unit to be converted into an analog signal and then is played through the loudspeaker of the voice codec unit.

The power amplification circuit comprises a push-stage automatic power control unit and a final-stage power control unit, wherein the push-stage automatic power control unit comprises a standing wave detection circuit, a detection circuit, an amplifier, a comparator and a push-stage power amplifier; the final power control unit comprises a final power amplifier and a buffer amplifier; in the push-stage automatic power control unit, the standing wave detection circuit is connected with the detection circuit, the amplifier, the comparator and the push-stage power amplifier in sequence, and a control port of the microprocessor is connected with an input end of the comparator; in the final power control unit, a control port of the microprocessor is connected to an input of the buffer amplifier, and an output of the buffer amplifier is connected to an input of the final power amplifier.

The transmitting radio frequency unit and the receiving radio frequency unit are integrated radio frequency transceiving chips, and phase-locked loop circuits are arranged in the transmitting radio frequency unit and the receiving radio frequency unit and are used for transmitting and receiving independently.

The push-stage automatic power control unit and the final-stage power control unit are synchronously set by the microprocessor, and the push-stage automatic power control unit and the final-stage power control unit are independently controlled by the microprocessor respectively.

The amplifier and the comparator in the push-level automatic power control unit both adopt an operational amplifier with high performance and low power consumption of Saint Band microelectronics, the model is SGM8272YMS8G, and the operational amplifier has a high conversion rate of 7V/us.

The buffer amplifier in the final-stage automatic power control unit adopts a Saint Pamp microelectronic high-performance operational amplifier with the model of SGM8535BYN5G, and the operational amplifier has wide input common-mode voltage and excellent output voltage swing.

The microprocessor uses an M4 kernel and above microcontroller.

The digital baseband unit adopts a digital baseband processing chip with the model of SCT 3258.

In the power supply unit, the output end of the power supply control circuit of the transmitting radio frequency unit has a tantalum capacitor with excellent service performance.

In the power supply unit, a power supply control circuit of the receiving radio frequency unit adopts a Diodes high-performance preset bias transistor, and the model is UMC 5N.

After the technical scheme is adopted, the vehicle-mounted interphone solves the problems that two sets of devices are required to be used for receiving and transmitting respectively, a duplexer and at least one antenna are required, and the traditional relay station erection scheme of two frequencies is required to be applied, and realizes the same-frequency relay function. The vehicle-mounted radio station is simplified to realize the same-frequency relay function only by matching one vehicle-mounted interphone with one antenna through corresponding software setting, saves frequency resources and purchasing funds compared with the traditional pilot frequency relay station, simultaneously does not need to be limited by the frequency bandwidth of a duplexer in frequency point selection, is simple and convenient to operate, and ensures high communication efficiency.

Furthermore, the push-level automatic power control unit and the final-level power control unit are synchronously arranged and independently controlled, so that the 30ms time sequence can be effectively controlled, the reliability of signals is ensured, and the self interference is prevented.

Furthermore, in the invention, the amplifier and the comparator in the push-stage automatic power control unit both adopt an operational amplifier with high performance and low power consumption of Saint Pont microelectronics, the model is SGM8272YMS8G, and the operational amplifier has a high conversion rate of 7V/us; therefore, the accuracy of transmitting and receiving the modulation signal of 27.5ms can be realized, and the switching between the transmission and the reception is strictly ensured to be completed within 2.5 ms.

Furthermore, in the invention, the buffer amplifier in the final-stage automatic power control unit adopts a Saint Pamp microelectronic high-performance operational amplifier with the model of SGM8535BYN5G, and the operational amplifier has wide input common-mode voltage and excellent output voltage swing and can rapidly and stably output the required voltage.

Furthermore, the output end of the power supply control circuit of the transmitting radio frequency unit has a tantalum capacitor (C1) with excellent performance, the tantalum capacitor has good filtering and stray inhibiting capabilities, and the power supply control circuit also has the advantages of good low-frequency characteristic linearity, no resonance to high frequency, smooth radio frequency signal conversion and no radio frequency oscillation or overshoot.

Further, in the invention, the receiving radio frequency unit power supply control circuit adopts a Diodes high-performance preset bias transistor (Q4) with the model number of UMC 5N. The power supply unit supplies power to each unit and each module independently through the high-performance switch circuit, so that the energy is saved, the efficiency is high, and the reliable and stable work and the non-interference between each unit and each module are ensured. Furthermore, a band elimination triode (Q3) is added to the control pin of the preset bias transistor, so that the turn-off speed is improved.

Drawings

FIG. 1 is a schematic block diagram of the circuit of the present invention;

FIG. 2 is a schematic block diagram of a power amplifier circuit according to the present invention;

FIG. 3 is a power control circuit of the receiving RF unit and the transmitting RF unit in the power supply unit according to the present invention;

fig. 4 is a flowchart of the operation of the same-frequency relay function in the present invention.

Detailed Description

As shown in FIG. 1, a host circuit of the vehicle-mounted interphone with the same-frequency relay function comprises an antenna port 1, a transceiving switch circuit 2, a power amplification circuit 3, a transmitting radio frequency unit 4, a receiving frequency selection circuit 5, a receiving radio frequency unit 6, a microprocessor 7, an external clock circuit 8, a coding and decoding unit 9, a digital baseband unit 10, a power supply unit 11 and a key unit 12;

the power supply unit 11 provides working power supply for the whole vehicle-mounted interphone;

the key unit 12 is connected to a corresponding input terminal of the microprocessor 7;

the microprocessor 7 is respectively in communication connection with the transmitting radio frequency unit 4, the receiving radio frequency unit 6 and the digital baseband unit 10; a same-frequency relay software module is programmed in the microprocessor 7, a same-frequency relay functional firmware is arranged in the digital baseband unit 10, and the same-frequency relay software module and the same-frequency relay functional firmware are mutually interacted to realize a software part of same-frequency relay;

the antenna port 1 is sequentially connected with a transceiving switch circuit 2, a receiving frequency selection circuit 5, a receiving radio frequency unit 6 and a coding and decoding unit 9, and the digital baseband unit 10 is bidirectionally connected with the coding and decoding unit 9; a receiving channel is formed by an antenna port 1, a transceiving switch circuit 2, a receiving frequency selection circuit 5, a receiving radio frequency unit 6, a coding and decoding unit 9 and a digital baseband unit 10;

the digital signal output end of the coding and decoding unit 9 is sequentially connected with an external clock circuit 8, a transmitting radio frequency unit 4, a power amplifying circuit 3, a receiving and transmitting switch circuit 2 and an antenna port 1; a transmitting channel is formed by a coding and decoding unit 9, a digital baseband unit 10, an external clock circuit 8, a transmitting radio frequency unit 4, a power amplifying circuit 3, a receiving and transmitting switch circuit 2 and an antenna port 1;

as shown in fig. 4, the vehicle-mounted intercom serves as a relay, and the relay realizes the relay function thereof by the following method:

s1: the relay enters the menu by operating the key unit of the relay, and the receiving and transmitting channel state of the relay is set in the menu, namely the working frequency and the working type of two radio frequency channels for relay receiving and transmitting are edited, so that the two radio frequency channels work at the same frequency and are in a digital mode;

s2: and starting the same-frequency relay function in the corresponding option in the menu of the relay party, and then the relay party works in the same-frequency relay mode according to the previously set transceiving channel state:

one of the two radio frequency channels works in a receiving state, the other one works in a transmitting state, only initialization is carried out at the moment, a transmitting power supply is not switched on to start transmitting, no power output exists, and the actual power output exists only when a signal is received; a microprocessor sends a CALL _ OPTION instruction (CALL setting instruction) to a digital baseband unit to set the digital baseband unit to work in a same-frequency relay mode, does not process conventional signals, and identifies and forwards a leading frame, a voice frame, a superframe and a tail frame in digital communication at any time slot and at another time slot;

s3: respectively starting a direct connection double-time slot function for vehicle-mounted interphones serving as a sender and a receiver, specifically, respectively entering a channel menu by the sender and the receiver through own key units, selecting a DMR mode menu, and setting the DMR mode menu as a direct connection double-time slot mode; meanwhile, the transmitting frequency point of the transmitting party and the receiving frequency point of the receiving party are set to be the same as the receiving and transmitting frequency point of the relaying party through respective key units, and the transmitting and receiving are respectively and fixedly selected two different time slots through respective key units entering a menu (at the moment, the transmitting party and the receiving party cannot recognize each other under the time slots, only a single time slot is processed, and the content of the time slot of the other party is ignored, so that the transmitting party and the receiving party can independently communicate with each other two by two under the same frequency point without mutual interference);

the method comprises the steps that a sender executes digital transmission operation, converts audio signals entering a microphone of the sender into digital signals after a series of compression, encryption, coding and modulation, the digital signals enter an analog baseband unit through an external clock circuit to generate digital radio frequency signals, enter a transceiving switch circuit after being amplified through a power amplification circuit and are transmitted out through an antenna port of the transceiving switch circuit; (the working principle of digital transmission refers to the related contents in the paragraphs [ 0041 ] to [ 0042 ] in the specification of the invention patent application 'a dual-band DMR handheld interphone' with the Chinese patent application number of 201711160890.2.

S4: the repeater receives the signal which is sent by the sender and has the same receiving time slot with the repeater from the antenna port, the signal enters a receiving frequency selection circuit through a transceiving switch circuit for frequency selection amplification, then the receiving radio frequency unit demodulates the signals into 4FSK signals, the digital baseband unit analyzes the reported data of the current 4FSK signals to the microprocessor to identify the current working time SLOT, then the microprocessor sends a DMR _ CALL _ SLOT instruction (calling time SLOT setting instruction) to the digital baseband unit to control the digital baseband unit to switch the work from any time SLOT receiving to the current time SLOT receiving, and stores the received current time SLOT data into a data buffer area of the digital baseband unit, then, in the next time slot (another time slot), the signal is forwarded out from the antenna port through the coding and decoding unit, the digital baseband unit, the external clock circuit, the transmitting radio frequency unit, the power amplifying circuit and the transceiving switch circuit;

s5: in the forwarding process, the digital baseband unit of the relay party generates a level signal which jumps once for 30ms according to the requirements of the DMR protocol to a microprocessor of the relay party to process the transceiving of DMR data: the microprocessor does not send CARRR _ LOST instruction (carrier disappearance instruction) and DMR _ CALL _ SLOT instruction (calling time SLOT setting instruction) to the digital baseband unit until the received signal disappears, thereby ending the relay state and returning to the standby state;

s6: the receiver sets the same relay frequency point and the same receiving time slot as the transmitting time slot of the relay, and can receive the digital signal of the sender forwarded by the relay, the digital signal received by the receiver from the antenna port enters the receiving circuit through the transceiving switch circuit, then the digital signal is demodulated through the analog baseband to generate a demodulated signal and enters the audio encoding and decoding unit to be converted into a digital form, then the demodulated signal is demodulated, extracted and decrypted in a series through the digital baseband unit to reconstruct the voice signal, and the reconstructed voice signal enters the voice encoding and decoding unit to be converted into an analog signal and then is played through the loudspeaker (the working principle of digital receiving refers to the relevant content of the sections [ 0037- [ 0038 ] in the specification of the invention patent application No. 201711160890.2 in the 'a dual-frequency DMR handheld interphone').

After the technical scheme is adopted, the vehicle-mounted interphone solves the problems that two sets of devices are required to be used for receiving and transmitting respectively, a duplexer and at least one antenna are required, and the traditional relay station erection scheme of two frequencies is required to be applied, and realizes the same-frequency relay function. The vehicle-mounted radio station is simplified to realize the same-frequency relay function only by matching one vehicle-mounted interphone with one antenna through corresponding software setting, saves frequency resources and purchasing funds compared with the traditional pilot frequency relay station, simultaneously does not need to be limited by the frequency bandwidth of a duplexer in frequency point selection, is simple and convenient to operate, and ensures high communication efficiency.

In the invention, the transmitting radio frequency unit 4 and the receiving radio frequency unit 6 are integrated radio frequency transceiver chips, and digital integrated phase-locked loop circuits are arranged in the transmitting radio frequency unit and the receiving radio frequency unit for independent use of transmitting and receiving. The traditional phase-locked loop circuit has poor performance and slow frequency locking, adopts a large loop feedback simulation comparison phase-locked mode of a discrete voltage-controlled oscillation circuit and a phase-locked IC, the phase-locked speed is determined by loop simulation parameters and frequency division phase-locked parameters, the set frequency cannot be locked quickly, the phase-locked IC is required to gradually approach comparison locking voltage, the frequency cannot be locked quickly under the influence of the frequency of a modulation signal, and the characteristic of the simulation phase-locked circuit determines the phase-locked speed; the digital integrated phase-locked loop circuit used by the invention adopts a direct decimal frequency division frequency synthesis mode, has quick frequency setting and high frequency division precision, and is not influenced by the frequency of a modulation signal and the like.

As shown in fig. 2, the power amplification circuit 3 includes a push-stage automatic power control unit including the standing wave detection circuit 13, the detection circuit 31, the amplifier 32, the comparator 33, and the push-stage power amplifier 36; the final power control unit includes a final power amplifier 35 and a buffer amplifier 34; in the push-stage automatic power control unit, the standing wave detection circuit 13 is connected with the detection circuit 31, the amplifier 32, the comparator 33 and the push-stage power amplifier 36 in sequence, and the control port of the microprocessor 7 is connected with the input end of the comparator 33; in the final power control unit, the control port of the microprocessor 7 is connected to the input of a buffer amplifier 34, and the output of the buffer amplifier 34 is connected to the input of a final power amplifier 35.

In the invention, two control ends of a microprocessor 7 synchronously set the push-stage automatic power control unit and the final-stage power control unit, and the microprocessor synchronously sends instructions to the push-stage automatic power control unit and the final-stage power control unit when synchronous setting is needed. Moreover, the microprocessor 7 respectively controls the push-stage automatic power control unit and the final-stage power control unit independently, so that the 30ms time sequence can be effectively controlled, the reliability of signals is ensured, and the self interference is prevented.

The amplifier and the comparator in the push-level automatic power control unit both adopt an operational amplifier with high performance and low power consumption of Saint Band microelectronics, the model is SGM8272YMS8G, and the operational amplifier has a high conversion rate of 7V/us. Therefore, the accuracy of transmitting and receiving the modulation signal of 27.5ms can be realized, and the switching between the transmission and the reception is strictly ensured to be completed within 2.5 ms.

The buffer amplifier in the final-stage automatic power control unit adopts a Saint Pamp microelectronic high-performance operational amplifier with the model of SGM8535BYN5G, and the operational amplifier has wide input common-mode voltage and excellent output voltage swing and can rapidly and stably output the required voltage.

In the present invention, the microprocessor 7 uses an M4 core and above microcontrollers. The operation speed of the kernel above M4 can meet the requirement of the invention for fast switching between relay receiving and transmitting.

In the present invention, the digital baseband unit 10 employs a digital baseband processing chip with a model SCT 3258.

As shown in fig. 3, the output terminal of the power control circuit of the transmitting rf unit uses a tantalum capacitor C1 with excellent performance. The tantalum capacitor has good filtering and stray inhibiting capabilities, and also has the advantages of good low-frequency characteristic linearity, no resonance to high frequency, smooth conversion of radio frequency signals, and no radio frequency oscillation or overshoot.

The power supply control circuit of the receiving radio frequency unit adopts a Diodes high-performance preset bias transistor Q4 with the model number of UMC5N, so that the power supply unit 11 provides power for each unit and module independently through the high-performance preset bias transistor Q4, energy is saved, efficiency is high, and the units and the modules are guaranteed to work reliably and stably without interference. Furthermore, a band elimination transistor Q3 is added to a control pin of the preset bias transistor Q4, so that the turn-off speed is improved.