Channel processing module based on HF / VHF dual-band autonomous frequency selection communication system

Abstract

The utility model discloses a channel processing module based on an HF / VHF dual-band autonomous frequency selection communication system, which comprises an antenna feeder unit, a radio frequency receiving channel, an MCU module, a frequency transmitting channel and a post-stage power amplifier unit which are sequentially connected, the front end of the radio frequency receiving channel is provided with a high-speed numerical control sub-band filter, and the channel processing module is also provided with an AGC composed of an LNA, a fixed attenuator and a step attenuator. The LNA and the fixed attenuator form-10dB,-20dB, 0dB and + 15dB gain attenuation circuits, the AGC controls two SP4T to switch, the stepping attenuator is a digital control variable 1dB stepping attenuator, the transmitting frequency path is provided with an ALC formed by a voltage-controlled variable gain amplifier and a low-distortion amplifier, and the variable gain amplifier provides-14dB-+ 17dB radio frequency signal adjustment. According to the utility model, a zero intermediate frequency scheme is adopted, signals are directly converted from RF to baseband, intermediate frequency modulation is not needed, the circuit is simple, the control is flexible, the stability and reliability are high, the development and production cost is low, the circuit can be used after assembly, and repeated debugging is not needed.

Description

Technical Field

[0001] The utility model relates to the technical field of wireless communication, in particular to a channel processing module based on an HF / VHF dual-band autonomous frequency selection communication system. Background Art

[0002] The HF / VHF dual-band transceivers currently used in the market are limited by the chip design and manufacturing technology at the time. The shortwave communication band and ultra-shortwave communication band transceivers are physically spliced ​​together, and the ARM control module is used to integrate the device and appearance. When working, it is necessary to manually switch it to the corresponding band to meet the communication needs of different frequency bands.

[0003] The RF channel processing modules of this system all adopt the superheterodyne solution, and use the spectrum shifting technology to achieve multiple frequency conversion of shortwave and ultra-shortwave RF signals to relatively low frequencies to meet the signal processing capabilities of low-speed ADC and DAC chips, realize the mutual conversion of analog signals and digital signals, and then send them to the corresponding front-end or back-end processing modules for processing. Since the spectrum shifting of superheterodyne requires the local oscillator frequency, mixing constitutes the channel receiving channel, which not only increases the complexity of the system and increases the cost, but also greatly reduces the reliability of the system. In addition, traditional reception also has the disadvantages of more combination frequencies generated by the nonlinearity of channel components, long frequency switching time of frequency synthesizers, and complex circuit implementation.

[0004] With the rapid improvement of VLSI design and manufacturing technology, the FPGA, DSP, ADC and DAC broadband processing capabilities of communication equipment are capable of integrating HF / VHF communication systems and realizing full-band autonomous frequency selection communication functions. Traditional RF channel processing modules require local oscillator and intermediate frequency conversion, and the intermediate frequency requires a fixed high-rectangular coefficient and high-stopband suppression high-performance filter, which makes the system complex and costly. The most important thing is that the fixed intermediate frequency and intermediate frequency bandwidth do not meet the requirements of the software radio architecture at all, and cannot meet the reloading of the system waveform. Utility Model Content

[0005] The technical solution adopted by the utility model to solve the above technical problems is:

[0006] The channel processing module based on the HF / VHF dual-band autonomous frequency selection communication system includes an antenna feed unit, a receiving and RF path, an MCU module, a transmitting and RF path, and a post-stage power amplifier unit which are sequentially connected. The front end of the receiving and RF path has a high-speed digitally controlled sub-band filter, and also has an AGC composed of an LNA, a fixed attenuator, and a step attenuator. The LNA and the fixed attenuator form a gain attenuation circuit of -10dB, -20dB, 0dB, and +15dB, which is switched by two SP4Ts controlled by the AGC. The step attenuator is a digitally controlled variable 1dB step attenuator.

[0007] The transmitting frequency path has an ALC composed of a voltage-controlled variable gain amplifier and a low-distortion amplifier. The variable gain amplifier provides -14dB to +17dB radio frequency signal adjustment.

[0008] Furthermore, the MCU module includes ADC, DAC, FPGA, DSP, CPLD and auxiliary interface circuits, and the MCU module is also externally connected to Flash, DDR3 SDRAM, RS232 and a network port.

[0009] Furthermore, the model of the high-speed numerically controlled sub-band filter is BT-STEF2M-90M-N15.

[0010] Furthermore, the model of the LNA is LTC6433AIUF-15_PBF, which provides a fixed gain amplification of +15dB.

[0011] Furthermore, the fixed attenuator is composed of two π-type fixed attenuation circuits, which respectively achieve fixed attenuation of -10dB and -20dB.

[0012] Furthermore, the model of the step attenuator is PE43704MLCA-Z.

[0013] Furthermore, the model of the SP4T is PE42540E-Z.

[0014] Furthermore, the model of the voltage-controlled variable gain amplifier is ADL5331ACPZ-R7, so as to meet the 30dB control requirement of ALC and realize output power control.

[0015] Furthermore, the model of the low distortion amplifier is LMH6703MA.

[0016] The beneficial effects of the utility model are: when receiving: the bandwidth is adaptive, the RF signal has a large power range, and the AGC control range is wide; when transmitting: the ALC processing has high-speed and continuous adjustable capabilities to meet the super-jump working requirements of VHF. The zero intermediate frequency solution is adopted, and the signal is directly changed from RF to baseband without intermediate frequency modulation. The hardware circuit is simple, the control is flexible, the system stability is high, the reliability is higher, the R&D and production costs are low, and the debugging is convenient. It can be used after assembly without repeated debugging, which improves productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the utility model;

[0018] Figure 2 It is a schematic diagram of the high-speed digitally controlled sub-band filter and auxiliary circuit of the utility model;

[0019] Figure 3 It is a circuit diagram of a fixed attenuator and a step attenuator of the utility model;

[0020] Figure 4 It is a circuit diagram of the LNA of the utility model;

[0021] Figure 5 It is a circuit diagram of the ALC of the utility model. DETAILED DESCRIPTION

[0022] The terms used in this utility model are all commonly defined in the field of wireless communication technology. Specifically, HF is high frequency, VHF is very high frequency, MCU is microcontroller unit, AGC is automatic gain control, ADC is analog-to-digital converter, ALC is automatic level control, LNA is low noise amplifier, DAC is digital-to-analog converter, FPGA is field programmable logic device, DSP is digital signal processor, CPLD is complex programmable logic device, Flash is flash memory, DDR3 SDRAM is dual-channel triple synchronous dynamic random access memory, RS232 is serial communication interface, SP4T is single-pole four-throw radio frequency switch. For other terms not listed, those skilled in the art should understand their definitions and interpretations in accordance with the commonly used definitions in this technical field.

[0023] The utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0024] like Figure 1-Figure 5As shown, the channel processing module based on the HF / VHF dual-band autonomous frequency selection communication system includes an antenna unit, a receiving RF path, an MCU module, a transmitting RF path and a post-stage power amplifier unit. The MCU module is adapted to the integrated service unit to realize a channel module with simple circuit, high system stability, low R&D and production cost, and convenient debugging. The utility model solves the following problems when receiving the HF / VHF channel: bandwidth adaptation, large RF signal power range, and wide AGC control range to meet the requirements of the high-performance ADC chip for limiting the amplitude and frequency changes of the input RF front-end signal; when transmitting: due to the super-jump working requirements of the VHF, the channel ALC processing needs to have high-speed and continuous adjustable capabilities to meet the equipment's requirements for setting the output power. The utility model has a simple hardware circuit, flexible control, higher reliability, and low production cost. It can be used after assembly, and does not require repeated debugging like the traditional superheterodyne solution, which improves productivity and reduces manufacturing costs.

[0025] Both the receiving and transmitting RF channels adopt the zero intermediate frequency solution. The receiving and transmitting RF channels use a high-speed digitally controlled sub-band filter to complete the band division and reorganization of the front-end signal. The time-varying RF signal is processed by a combination of LNA, fixed attenuator and step attenuator to complete the AGC processing of the receiving RF signal. The step attenuator is a digitally controlled attenuator with a variable 1dB step, which effectively solves the ADC input signal overflow problem. The transmitting RF channel uses a combination of a voltage-controlled variable gain amplifier and a low-distortion amplifier to complete the ALC control of the transmission excitation signal, which meets the frequency response problem of the post-stage power unit of the transmitting RF channel processing and ensures that the system output signal power meets the ±1dB requirement.

[0026] The transceiver channel control circuit is provided by the MCU module, which includes ADC, DAC, FPGA, DSP, CPLD and auxiliary interface circuits to complete various processing and control. The MCU module is connected to serial port Flash, DDR3 SDRAM, RS232 serial port and network port and other interfaces; the FPGA external CPLD chip realizes the control expansion of the channel processing module and other modules, providing a wealth of built-in and external interfaces for this utility model, so that the device is more in line with the reloading requirements of the software radio system.

[0027] The high-speed CNC sub-band filter model preferably uses BT-STEF2M-90M-N15 to solve the out-of-band interference of broadband signals.

[0028] The RF switching of LNA, fixed attenuator and step attenuator is completed by two RF switches SP4T. The model of SP4T is preferably PE42540E-Z to realize the conversion of LNA, fixed attenuation and step attenuation during reception.

[0029] The preferred model of the step attenuator is PE43704MLCA-Z, which can meet the small value step attenuation between fixed attenuation during reception.

[0030] The LNA model preferably uses LTC6433AIUF-15_PBF, which provides +15dB fixed gain amplification for the front end of the receiving channel, reduces the noise coefficient of the whole machine, and meets the high sensitivity requirements under weak signal conditions.

[0031] The fixed attenuator consists of two π-type fixed attenuation circuits, which respectively achieve coarse attenuation of -10dB and -20dB fixed attenuation.

[0032] The preferred model of the voltage-controlled variable gain amplifier for the transmit frequency path is ADL5331ACPZ-R7, which meets the 30dB control requirement of ALC and realizes the output power control of the system.

[0033] The preferred low distortion amplifier model is LMH6703MA.

[0034] During transmission: the modulated signal generated by the DAC of the MCU module is sent to the ALC processing circuit of the transmitting frequency path, and the voltage-controlled variable gain amplifier provides -14dB to +17dB RF signal adjustment. The adjusted signal is amplified by a low-distortion amplifier and sent to the subsequent power amplifier unit.

[0035] LNA and fixed attenuator form a fixed gain attenuation circuit, including 4 paths of -10dB, -20dB, 0dB and +15dB, which are switched by SP4T.

[0036] The MCU module implements AGC control of the broadband receiving RF. The process is that the ADC completes the sampling of the broadband receiving RF signal, and then sends it to the FPGA for processing, and then submits it to the DSP for evaluation and calculation. Finally, the AGC control signal is sent to the receiving channel control interface of the channel module through the control interface to control the SP4T to achieve amplification or attenuation. Similarly, when transmitting, the transmitted power signal is sampled, and the processed control signal is sent to the transmitting channel control interface to control the output gain of the variable gain amplifier so that the system output power meets the ±1dB change requirement.

[0037] Workflow: When receiving: The RF signal is transmitted to the receiving RF channel through the antenna unit. First, the high-speed digitally controlled sub-band filter completes the band division and reorganization of the front-end signal, and then passes through the fixed gain attenuation circuit composed of LNA and fixed attenuator. The AGC of the MCU module controls the SP4T to switch the gain, pass through or attenuation, and then passes through the step attenuator for small value step attenuation, and finally enters the MCU module for processing and control.

[0038] During transmission: The modulated signal generated by the DAC of the MCU module is transmitted to the voltage-controlled variable gain amplifier, the output power is controlled by the ALC, and then amplified by the low-distortion amplifier and sent to the subsequent power amplifier unit.

[0039] The present utility model is not limited to the above-mentioned optimal implementation mode. Any other products identical or similar to the present utility model derived by anyone under the inspiration of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. A channel processing module based on an HF / VHF dual-band autonomous frequency selection communication system, comprising an antenna feed unit, a receiving radio frequency path, an MCU module, a transmitting radio frequency path and a post-stage power amplifier unit connected in sequence, characterized in that: The front end of the receiving radio frequency path has a high-speed digitally controlled sub-band filter, and also has an AGC composed of an LNA, a fixed attenuator and a step attenuator. The LNA and the fixed attenuator form a gain attenuation circuit of -10dB, -20dB, 0dB and +15dB, which is switched by two SP4Ts controlled by the AGC. The step attenuator is a digitally controlled attenuator with a variable 1dB step. The transmitting radio frequency path has an ALC composed of a voltage-controlled variable gain amplifier and a low-distortion amplifier. The variable gain amplifier provides -14dB to +17dB radio frequency signal adjustment.

2. The channel processing module based on the HF / VHF dual-band autonomous frequency selection communication system according to claim 1, characterized in that: The MCU module includes ADC, DAC, FPGA, DSP, CPLD and auxiliary interface circuits. The MCU module is also externally connected to Flash, DDR3 SDRAM, RS232 and a network port.

3. The channel processing module based on the HF / VHF dual-band autonomous frequency selection communication system according to claim 1, characterized in that: The model of the high-speed numerically controlled sub-band filter is BT-STEF2M-90M-N15.

4. The channel processing module based on the HF / VHF dual-band autonomous frequency selection communication system according to claim 3 is characterized in that: The LNA model is LTC6433AIUF-15_PBF, which provides a fixed gain amplification of +15dB.

5. The channel processing module based on the HF / VHF dual-band autonomous frequency selection communication system according to claim 4 is characterized in that: The fixed attenuator is composed of two π-type fixed attenuation circuits, which respectively realize fixed attenuation of -10dB and -20dB.

6. The channel processing module based on the HF / VHF dual-band autonomous frequency selection communication system according to claim 5, characterized in that: The model of the step attenuator is PE43704MLCA-Z.

7. The channel processing module based on the HF / VHF dual-band autonomous frequency selection communication system according to claim 6, characterized in that: The model of the SP4T is PE42540E-Z.

8. The channel processing module based on the HF / VHF dual-band autonomous frequency selection communication system according to claim 1, characterized in that: The model of the voltage-controlled variable gain amplifier is ADL5331ACPZ-R7, which can meet the 30dB control requirement of ALC and realize output power control.

9. The channel processing module based on the HF / VHF dual-band autonomous frequency selection communication system according to claim 8, characterized in that: The model of the low distortion amplifier is LMH6703MA.

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