Miniaturized multi-standard digital interphone

Abstract

The utility model discloses a miniaturized multi-system digital interphone, a host circuit of which comprises an antenna port, a transmit-receive conversion circuit, a transmitting unit, an analog baseband unit, a digital baseband unit, an external clock circuit, a microprocessor, an audio power amplifier unit, a loudspeaker and a microphone, and the analog baseband unit adopts an FD6818 radio frequency baseband chip. The FD6818 radio frequency baseband chip supports channel bandwidths of 12.5 kHz and 25 kHz, and communication systems with channel bandwidths of 6.25 kHz, such as dPMR, NXDN and the like. Moreover, the FD6818 radio frequency baseband chip can directly output a demodulated analog audio signal, and the requirement on the post-stage digital baseband processing performance is relatively low. Moreover, the FD6818 radio frequency baseband chip replaces a to-be-demodulated signal generation circuit composed of a phase-locked loop chip LMX2571 integrated with a voltage-controlled oscillator and a zero intermediate frequency receiver chip SCT3810 in the prior art, and the circuit is further simplified, so that the interphone is smaller in size and more compact in structure.

Description

Technical Field

[0001] The utility model relates to the field of communications, in particular to a miniaturized multi-standard digital intercom. Background Art

[0002] With the changes in market demand, how to achieve the miniaturization of walkie-talkies has been a hot topic in the industry in recent years.

[0003] The background technology of Chinese utility model patent CN208128240U mentions that there are some small digital walkie-talkie modules on the market that use zero intermediate frequency or near-zero intermediate frequency solutions and can be integrated into mobile phones, but the performance is unsatisfactory. Among them, the module that uses Litong's AT1846S as the RF transceiver is representative. Zero intermediate frequency or near-zero intermediate frequency receivers have almost stringent requirements on the phase noise of the local oscillator signal. In addition, the low-noise amplifier and mixer of the RF front end are required to have extremely high linearity. However, AT1846S is limited by the process of the chip itself, and the supply voltage of its internal analog power supply is low, which seriously affects the dynamic range of the internal low-noise amplifier and mixer, resulting in the linearity failing to meet the requirements of professional digital walkie-talkies. Secondly, due to the use of CMOS technology, the phase noise of the local oscillator signal generated by its internal voltage-controlled oscillator cannot guarantee that the working performance of the entire receiver can meet the ETSI EN 300 113 test standard for professional digital walkie-talkies. If the user wants to provide a high-quality local oscillator signal externally, AT1846S does not support this. At the same time, due to the limitation of the internal channel filter, AT1846S can only support 12.5kHz and 25kHz channel bandwidths, so it cannot support communication formats with 6.25kHz channel bandwidth such as dPMR and NXDN.

[0004] In view of the above problems, Chinese utility model patent CN208128240U proposes a high-performance, miniaturized, multi-standard digital walkie-talkie module, which includes: a zero intermediate frequency receiver chip SCT3810, which generates an IQ signal; a baseband SCT3268 chip, which includes a digital signal processor and a microcontroller. When the walkie-talkie transmits a voice signal, the baseband SCT3268 chip processes the voice signal through the digital signal processor to obtain a digital baseband signal to be modulated, and transmits it after digital-to-analog conversion and modulation; when the walkie-talkie receives a voice signal, the baseband SCT3268 chip demodulates the IQ signal, and outputs it for playback after digital-to-analog conversion; The voltage-controlled crystal oscillator receives the digital baseband signal to be modulated and modulates it by the voltage-controlled end, and outputs the reference clock signal to the outside at the same time; the RF transmitter includes the phase-locked loop chip LMX2571 with an integrated voltage-controlled oscillator, provides the local oscillator signal to the zero intermediate frequency receiver chip SCT3810, receives the reference clock signal, and performs FM modulation on the digital baseband signal modulated by the voltage-controlled crystal oscillator; the RF amplifier includes the SCT3604 RF power amplifier chip, which amplifies the power of the modulated signal and outputs it to the RF transceiver switch; the RF transceiver switching switch is connected to the RF amplifier to realize the switching of the signal output state and the external signal input state.

[0005] A high-performance, miniaturized, multi-standard digital walkie-talkie module with Chinese utility model patent CN208128240U adopts the high-linearity zero intermediate frequency receiver chip SCT3810 to directly convert the high-quality local oscillator signal and the RF signal into an IQ signal for demodulation by baseband. The transmitter uses the signal source that provides the high-quality local oscillator signal to the receiver, uses the voltage-controlled crystal oscillator as the reference clock, uses the modulation signal to control the voltage-controlled end of the crystal oscillator and cooperates with the appropriate loop bandwidth setting to achieve the final FM modulation. While having a very high degree of integration, it can fully meet the test standards such as ETSI EN300 086, ETSI EN 300 113, and ETSI EN 301 166 required by professional walkie-talkies. It not only overcomes the complex circuit structure and large physical size brought about by the superheterodyne structure of traditional high-performance walkie-talkies, as well as the inconsistency brought about by a large number of discrete components, but also avoids the defect of insufficient anti-interference ability of the receiver caused by the pursuit of miniaturization by the zero intermediate frequency structure.

[0006] However, the miniaturized multi-standard digital intercom module provided by the Chinese utility model patent CN208128240U still has the following problems:

[0007] 1. The zero-IF receiver chip SCT3810 generates an IQ signal, which means that the baseband SCT3268 chip in the subsequent stage of the solution must have the IQ signal demodulation function, which places relatively high requirements on the device.

[0008] 2. The demodulated signal generation circuit is composed of the phase-locked loop chip LMX2571 with integrated voltage-controlled oscillator and the zero intermediate frequency receiver chip SCT3810, but the circuit is not simple enough. Utility Model Content

[0009] The utility model aims to provide a miniaturized multi-standard digital interphone which has lower performance requirements on a digital baseband unit and a simpler structure.

[0010] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0011] A miniaturized multi-standard digital intercom, whose host circuit includes an antenna port, a transceiver conversion circuit, a transmitting unit, an analog baseband unit, a digital baseband unit, an external clock circuit, a microprocessor, an audio power amplifier unit, a speaker and a microphone, wherein:

[0012] The microprocessor is communicatively connected with the analog baseband unit and the digital baseband unit respectively;

[0013] The antenna port, the transceiver conversion circuit, the analog baseband unit, the digital baseband unit, the audio power amplifier unit and the speaker connected in sequence form a receiving channel;

[0014] The microphone, the digital baseband unit, the external clock circuit, the analog baseband unit, the transmitting unit, the transceiver conversion circuit and the antenna port connected in sequence constitute a transmitting channel;

[0015] The analog baseband unit adopts the FD6818 radio frequency baseband chip.

[0016] Furthermore, a high-pass filter is connected between the transceiver conversion circuit and the analog baseband unit.

[0017] Furthermore, the high-pass filter selects a UHF high-pass filter or a VHF high-pass filter according to different frequency bands.

[0018] Furthermore, a coupling capacitor is connected between the analog baseband unit and the digital baseband unit, and the capacity of the coupling capacitor is 10uF-22uF and the specification is 0603.

[0019] Furthermore, the digital baseband unit adopts a SCT3288 digital baseband processing chip.

[0020] After adopting the above scheme, the utility model is a miniaturized multi-standard digital walkie-talkie, the analog baseband unit adopts the FD6818 RF baseband chip, the FD6818 RF baseband chip optimizes the linearity of the low-noise amplifier and mixer of the internal RF front end, optimizes the phase noise of the local oscillator signal generated by the internal voltage-controlled oscillator to ensure that the working performance of the entire receiver can meet the digital walkie-talkie test standard, optimizes the internal AGC control to improve the ability to resist intermodulation interference and blocking interference, and optimizes the internal filter to support 12.5kHz and 25kHz channel bandwidths, dPMR, NXDN and other 6.25kHz channel bandwidth communication standards, with high selectivity and good compatibility. Moreover, the FD6818 RF baseband chip can directly output the demodulated analog audio signal, and the requirements for the digital baseband processing performance of the subsequent stage are relatively low. Moreover, in the utility model, the FD6818 radio frequency baseband chip replaces the demodulated signal generation circuit composed of the phase-locked loop chip LMX2571 with an integrated voltage-controlled oscillator and the zero intermediate frequency receiver chip SCT3810 in the prior art, further simplifying the circuit, making the walkie-talkie smaller in size and more compact in structure. At the same time, because the circuit structure is simpler, it has a great advantage in the power consumption of the whole machine, which can greatly extend the working time of the walkie-talkie. Compared with the prior art, it has a very large advantage in material cost and production difficulty.

[0021] Furthermore, in the utility model, a high-pass filter is connected between the transceiver conversion circuit and the analog baseband unit, which can improve the impedance matching with the RF input end of the analog baseband unit and filter out the out-of-band signal to reduce out-of-band interference and improve the spurious response.

[0022] Furthermore, in the present invention, a coupling capacitor is connected between the analog baseband unit and the digital baseband unit, and the capacity of the coupling capacitor is 10uF-22uF, and the specification is 0603, so that the integrity of the digital short message format data can be effectively retained. Moreover, the coupling capacitor is selected in the specification of 0603, so that the capacitor with the smallest volume specification can be used under the premise of ensuring large capacity performance.

[0023] Furthermore, in the utility model, the digital baseband unit adopts the SCT3288 digital baseband processing chip, which has a built-in codec (codec) inside, has a higher degree of integration, and is more conducive to the miniaturization of the digital walkie-talkie. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The utility model is a circuit principle block diagram of a miniaturized multi-standard digital intercom.

[0025] Figure 2 for Figure 1 In the figure, the circuit schematic diagram of the UHF segment high-pass filter.

[0026] Figure 3 for Figure 1 In the figure, the circuit schematic diagram of the VHF band high-pass filter. DETAILED DESCRIPTION

[0027] The utility model discloses a miniaturized multi-standard digital intercom, such as Figure 1 As shown, the host circuit includes an antenna port 1, a transceiver conversion circuit 3, a transmitting unit 5, an analog baseband unit 6, a digital baseband unit 7, an external clock circuit 8, a microprocessor 9, an audio power amplifier unit 10, a speaker 11 and a microphone 12, wherein:

[0028] The microprocessor 9 is communicatively connected with the analog baseband unit 6 and the digital baseband unit 7 respectively;

[0029] The antenna port 1, the transceiver conversion circuit 3, the analog baseband unit 6, the digital baseband unit 7, the audio power amplifier unit 10 and the speaker 11 connected in sequence constitute a receiving channel;

[0030] The microphone 12, the digital baseband unit 7, the external clock circuit 8, the analog baseband unit 6, the transmitting unit 5, the transceiver conversion circuit 3 and the antenna port 1 connected in sequence constitute a transmitting channel;

[0031] The analog baseband unit 6 uses the FD6818 radio frequency baseband chip.

[0032] During transmission, the audio signal emitted by the microphone 12 is gain controlled, compressed, encrypted, encoded, and modulated by the digital baseband unit 7 to generate a digital signal. This digital signal enters the analog baseband unit 6 via the external clock circuit 8 to generate a digital RF signal, enters the transceiver conversion circuit 3 via the transmitting unit 5, and is transmitted from the antenna port 1.

[0033] During reception, the digital signal input from the antenna port 1 enters the transceiver conversion circuit 3, is demodulated by the analog baseband unit 6, and generates a demodulated signal. The demodulated signal enters the digital baseband unit 7 and is converted into a digital signal and demodulated, extracted, compressed, and decrypted to reconstruct the voice signal. The reconstructed voice signal is converted back into an analog voice signal and output and played through the audio power amplifier unit 10 and the speaker 11.

[0034] The utility model is a miniaturized multi-standard digital intercom, the analog baseband unit adopts the FD6818 radio frequency baseband chip, and makes full use of the excellent performance of the FD6818 radio frequency baseband chip itself. Specifically, the FD6818 radio frequency baseband chip optimizes the linearity of the low noise amplifier and mixer of the internal radio frequency front end, optimizes the phase noise of the local oscillator signal generated by the internal voltage-controlled oscillator to ensure that the working performance of the entire receiver can meet the digital intercom test standard, optimizes the internal AGC control to improve the ability to resist intermodulation interference and blocking interference, and optimizes the internal filter to support 12.5kHz and 25kHz channel bandwidths, dPMR, NXDN and other communication systems with 6.25kHz channel bandwidths, with high selectivity and good compatibility. Moreover, the FD6818 radio frequency baseband chip can directly output the demodulated analog audio signal, and the processing performance requirements for the digital baseband unit of the subsequent stage are relatively low. Moreover, in the utility model, the FD6818 radio frequency baseband chip replaces the demodulated signal generation circuit composed of the phase-locked loop chip LMX2571 with an integrated voltage-controlled oscillator and the zero intermediate frequency receiver chip SCT3810 in the prior art, further simplifying the circuit, making the walkie-talkie smaller in size and more compact in structure. At the same time, because the circuit structure is simpler, it has a great advantage in the power consumption of the whole machine, which can greatly extend the working time of the walkie-talkie. Compared with the prior art, it has a very large advantage in material cost and production difficulty.

[0035] Furthermore, the miniaturized multi-standard digital walkie-talkie of the utility model is also connected to the antenna port 1 and the transceiver conversion circuit 3 with a low-pass filter 2. Through the filtering effect of the low-pass filter 2, the noise and clutter in the received signal are reduced, making the signal received by the walkie-talkie cleaner and more stable, thereby improving the communication effect.

[0036] Furthermore, a high-pass filter 4 is connected between the transceiver conversion circuit and the analog baseband unit. The high-pass filter 4 uses a UHF high-pass filter or a VHF high-pass filter according to different frequency bands. The specific circuits of the UHF high-pass filter and the VHF high-pass filter are as follows: Figure 2 and Figure 3 As shown, by connecting a high-pass filter 4 between the transceiver conversion circuit 3 and the analog baseband unit 6, the impedance matching with the RF input end of the analog baseband unit 6 can be improved, and out-of-band signals can be filtered out to reduce out-of-band interference and improve spurious response.

[0037] Furthermore, a coupling capacitor is connected between the analog baseband unit 6 and the digital baseband unit 7, and the capacity of the coupling capacitor is 10uF-22uF, and the specification is 0603, so that the integrity of the digital short message format data can be effectively retained. Moreover, the coupling capacitor uses the 0603 specification, which can use the capacitor with the smallest volume specification while ensuring large capacity performance.

[0038] Although the high-pass filter 4 and the coupling capacitor are added in the present invention, the high-pass filter 4 and the coupling capacitor are both composed of resistors and capacitors, which are much smaller than the integrated chip and have little effect on the overall volume.

[0039] Furthermore, in the present invention, the digital baseband unit 7 adopts the SCT3288 digital baseband processing chip, which has a built-in codec (codec) inside, has a higher degree of integration, and is more conducive to the miniaturization of the digital walkie-talkie.

[0040] In the present invention, the transmitting unit 5 adopts a conventional transmitting unit.

[0041] In the present invention, the audio power amplifier unit 10 adopts a conventional audio power amplifier unit.

[0042] In the present invention, the transceiver conversion circuit 3 adopts a conventional transceiver conversion circuit, such as an antenna radio frequency switch diode.

[0043] In the present invention, the external clock circuit 8 adopts a conventional external clock circuit, such as a voltage-controlled crystal oscillator.

[0044] In the present invention, the microprocessor 9 adopts a conventional microprocessor, such as a microprocessor of model N32G452REL7.

[0045] The receiving and transmitting performances of the intercom designed by the specific embodiment of the utility model are shown in the following table:

[0046]

[0047] The above is only a preferred embodiment of the present invention, and all equivalent changes and modifications made within the scope of the claims of the present utility model shall fall within the scope of the claims of the present utility model.

Claims

1. A miniaturized multi-standard digital intercom. Features: The host circuit includes an antenna port, a transceiver conversion circuit, a transmitting unit, an analog baseband unit, a digital baseband unit, an external clock circuit, a microprocessor, an audio power amplifier unit, a speaker and a microphone, wherein: The microprocessor is communicatively connected with the analog baseband unit and the digital baseband unit respectively; The antenna port, the transceiver conversion circuit, the analog baseband unit, the digital baseband unit, the audio power amplifier unit and the speaker connected in sequence form a receiving channel; The microphone, the digital baseband unit, the external clock circuit, the analog baseband unit, the transmitting unit, the transceiver conversion circuit and the antenna port connected in sequence form a transmitting channel; The analog baseband unit adopts the FD6818 radio frequency baseband chip.

2. A miniaturized multi-standard digital intercom according to claim 1, Features: A high-pass filter is connected between the transceiver conversion circuit and the analog baseband unit.

3. A miniaturized multi-standard digital intercom according to claim 2, Features: The high-pass filter selects a UHF high-pass filter or a VHF high-pass filter according to different frequency bands.

4. A miniaturized multi-standard digital intercom according to claim 1, Features: A coupling capacitor is connected between the analog baseband unit and the digital baseband unit, and the capacity of the coupling capacitor is 10uF-22uF, and the specification is 0603.

5. A miniaturized multi-standard digital intercom according to claim 1, Features: The digital baseband unit adopts the SCT3288 digital baseband processing chip.

Images