CN108880657B - Frequency conversion forwarding device based on technology detection technology in air-based relay communication enhancement system - Google Patents
Frequency conversion forwarding device based on technology detection technology in air-based relay communication enhancement system Download PDFInfo
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Abstract
The invention belongs to the technical field of wireless communication, and particularly relates to a frequency conversion repeater based on technology detection in a space-based relay communication enhancement system, aiming at designing and constructing the space-based relay communication enhancement system by utilizing the idea of technology detection and frequency conversion. The method is characterized in that: the system comprises an air signal forwarding subsystem and a ground signal forwarding subsystem; the frequency conversion repeater in the aerial signal forwarding subsystem is positioned at a relay load of the unmanned aerial vehicle, fast searches and receives an uplink signal through an antenna, then up-converts the received VHF signal into a signal of an L frequency band, and the signal is amplified and then is forwarded downwards through the antenna; the frequency conversion repeater in the ground signal forwarding subsystem is used for receiving downlink signals forwarded in the air, converting the downlink signals into original wave band signals through down-conversion by the frequency conversion repeater, and outputting the original wave band signals to an antenna for forwarding after frequency selection processing, so that the original wave band signals can be used by nearby ultrashort wave communication equipment.
Description
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a technical detection technology-based variable frequency forwarding device in a space-based relay communication enhancement system.
Background
1.1 background of the application
With the continuous popularization of mobile communication technology in China, the establishment of land mobile base stations basically realizes the full coverage of mobile signals in dense areas such as cities, towns and the like. However, in recent years, emergencies occur frequently, severe natural disasters cause great damage to social stability and life safety of people, in multiple disasters, a communication system, a network and a power supply system based on fixed infrastructure are seriously damaged and even completely paralyzed, in the prime time period of emergency relief, a communication link with the lowest standard is difficult to establish, the emergency rescue squad is not smooth to communicate with personnel in a disaster area, and the auxiliary decision-making to take rescue measures is difficult. In addition, the construction of offshore communication networks in China still needs to be improved, communication means of fishing boats and sea surveillance boats after the sea is out are very limited, and once an emergency occurs or important information is monitored, the situation is difficult to be fed back at the first time. Therefore, the demand of China for onshore emergency response communication and offshore communication is urgent.
In order to meet the above requirements, relay countermeasures for emergency communication, such as temporary deployment and distribution of satellite communication equipment, communication relay of specific equipment by unmanned aerial vehicles, and the like, have been continuously developed in real life. But the practical application situation is that the requirement of satellite communication on equipment is very strict, the price is high, and the satellite communication is difficult to popularize in a large quantity; for the existing unmanned aerial vehicle communication relay mode, the relay load on the unmanned aerial vehicle cannot be communicated with common wireless communication equipment such as interphones, radio stations and the like which are used in a large number in the folk, and the universality is poor. In view of this, this patent is oriented to a large amount of current ultrashort wave equipment in the folk, based on the lift-off platform, fully considers the problem of receiving and dispatching antenna isolation, utilizes techniques such as radio's listening and receiving and frequency conversion forwarding, under the condition that does not change current terminal protocol, antenna, port, has proposed the scheme of frequency conversion relay: the VHF (30M-88MHz) signals in the region are intercepted and received in the air, and are up-converted to the L frequency band (1.35G-1.8GHz) by the frequency converter to be transmitted downwards for being received by the ground terminal, so that the interconnection and intercommunication of the wireless communication equipment under the condition of over-the-horizon are realized.
1.2 Prior Art and its advantages and disadvantages
1.2.1 ultrashort wave radio station relay correlation technique
The ultra-short wave radio station communication system is widely applied to the fields of military use, offshore operation and the like, and users can realize the receiving and sending of radio station information in a certain area after carrying out communication networking by utilizing an electric station. Radio station communication is widely used by governments, the aviation industry and the military, as a large amount of communication infrastructure construction is not needed. However, due to factors such as wavelength and power, the direct communication distance between the stations is short, and during the transmission process, the radio waves are easily affected by the landforms of mountains, jungles and the like and the weather, and the communication capability is limited. The existing method enhances the communication capability of the radio station by establishing a radio station relay and a signal amplification load which are fixed on the ground or carried by an elevated platform. In terms of the method for relaying communication of the unmanned aerial vehicle, the most core technology is the design of relay load except for the model selection of the unmanned aerial vehicle, and currently, the main relay modes are mainly divided into three types: a legacy relay mode, a network coded relay mode, and a physical layer network coded relay mode. In the traditional relay mode, the relay node only stores and forwards information and does not process the information. The main idea of the network coding relay mode is that the relay node performs operations such as coding mapping and the like on information sent by the source node and then forwards the information, and the definition of the relay node in the traditional communication network is broken through, so that the multicast transmission reaches the maximum theoretical transmission capacity, and the throughput of the communication system and the effectiveness of the communication transmission are improved. In the physical layer network coding relay mode, the relay node maps the superimposed signals simultaneously transmitted by the source node into a galois field data bit stream, turning the interference into a part of the coding operation. Compared with the traditional mode, the mode information exchange time slot is reduced by half, and the network throughput is doubled. In terms of practical application, the relay mode of the unmanned aerial vehicle has certain limitations:
(1) a limitation of error coding; in the direct store-and-forward mode, due to the lack of corresponding error correction coding and coding modulation on the forwarding information, the indexes of the mode, such as information transmission efficiency, spectrum utilization rate, bit error rate and the like, are not as good as those of the latter two modes, and the information throughput, timeliness and accuracy are still to be improved.
(2) Limitations of the communication regime; it can be seen that in the second and third modes, the relay load needs to encode the received information, which means that the load design needs to consider the relay frequency band fully and also needs to grasp the transmitted information protocol in advance, otherwise, the received signal cannot be processed and forwarded, so as to achieve the purpose of improving throughput and information transmission rate. The premise greatly limits the extended application of the relay load, the load is difficult to be applied to other frequency bands or communication systems following other information protocols once being applied, and the limitation of a communication system to the load is large.
(3) Limitation of coverage; limited by the flight height of the unmanned aerial vehicle, the field angle of the load antenna is small, the shielding on the electric wave propagation path is more, the signal attenuation is large, the coverage range of the relay load on the ground is limited, and the communication in a large and small area with the requirement cannot be guaranteed.
(4) Limitation of user size; limited by factors such as power, terrain and the like, and the relay load supports small-scale networking users. Because the levitation platform especially needs to consider factors such as load and power, and the volume of the relay load antenna and the signal transmitting power cannot be designed to be too large, the communication relay endurance of the levitation platform is limited, a large number of networking communication terminals cannot be supported, and the support of the relay load on concurrent communication of users is weak.
1.2.2 related art
The technical reconnaissance technology is also called as communication reconnaissance technology, the main tasks of the technical reconnaissance technology are electromagnetic spectrum detection, acquisition of technical parameters and connotation information of enemy communication signals, lateral direction and positioning of radiation source signals and the like, and the technology is widely applied to military electronic information warfare. In order to better realize communication reconnaissance, three key technologies are mainly involved: (1) fast searching and intercepting communication signals; (2) identification of the modulation of the communication signal; (3) high-precision direction finding and positioning of communication signals.
(1) A rapid search and interception technology of communication signals; as a non-cooperative party, a communication scout does not always know the position of a signal of interest in advance, and does not know when the signal appears, which frequency point or frequency band the signal works in, and some of the signals are mixed in dozens or hundreds of useless signals or interference signals and possibly buried in noise, so that the search and interception of the signal are the primary tasks to be solved by the communication scout. The methods generally used are mainly: fixed threshold detection, frequency planning and filtering, and adaptive threshold detection.
(2) Modulation identification technology of communication signals; after the signal is acquired through the signal searching and intercepting technology, the communication reconnaissance system needs to identify the modulation parameters (modulation coefficient, signal bandwidth, carrier frequency, code rate and the like) of the received signal according to the statistical sample by using a signal processing method, and judge the communication system, the modulation mode, the signal type and the like of the communication reconnaissance system. At present, a modulation identification technology of communication signals is applied to actual engineering to obtain a certain effect, but how to improve the modulation identification accuracy of communication signals under the conditions of small samples and low signal-to-noise ratio, and find new identification characteristic parameters, identification methods and the like which have smaller calculated amount, are suitable for complex electromagnetic environment, are suitable for engineering realization and have better identification performance, is still the direction of efforts for a long time in the future.
(3) High-precision direction finding and positioning technologies of communication signals; and finally, measuring and calculating the emission direction and the position of the signal according to the transmission characteristics of the electric wave. The method mainly utilizes a amplitude comparison method, a correlation interferometer direction finding method and a time difference direction finding method to finish directional measurement, and utilizes a time difference positioning method, a single station positioning method and the like to finish the positioning measurement of signals.
Disclosure of Invention
The VHF band radio communication is radio communication using electromagnetic waves in an ultra-short wave band of 30MHz to 300MHz, and is also called very high frequency communication. The main characteristics are that: the ground absorption is large, the ionized layer can not reflect, and the transmission can only be realized in a linear mode, which is called line-of-sight transmission and is widely used in the fields of military application, aerospace test and the like.
The invention designs a communication relay of ultrashort wave radio station equipment, loads are positioned on a long-endurance unmanned aerial vehicle with the flying height of 20KM, and the air-based relay communication enhancement system is designed and constructed by the aid of the technical detection and frequency conversion thought in consideration of that strong same-frequency interference can be generated by receiving and transmitting signals through antennas at the same frequency so as to influence communication effects. The system mainly comprises an air signal forwarding subsystem and a ground signal forwarding subsystem, and the system framework is shown in figure 1. The frequency conversion repeater in the aerial signal forwarding subsystem is located in a relay load of the unmanned aerial vehicle, fast searches and receives an uplink signal through an antenna, then up-converts the received VHF signal into a signal of an L frequency band, and the signal is amplified and then is forwarded downwards through the antenna. The frequency conversion repeater in the ground signal forwarding subsystem is used for receiving downlink signals forwarded in the air, converting the downlink signals into original wave band signals through down-conversion by the ground signal frequency conversion repeater, outputting the original wave band signals to an antenna for forwarding after frequency selection processing, and supplying the original wave band signals to adjacent ultrashort wave communication equipment for use. The subsystem equipment has the characteristics of small size and low power consumption, and is convenient to flexibly configure and use.
The space-based relay communication enhancement system can support more than 250 users to use simultaneously by carrying out aerial reconnaissance, relay and frequency conversion forwarding processing on wireless signals, better solves the communication problem caused by the lack of a ground communication relay system in a specific area within a certain time range, and has great significance for communication guarantee under the scenes of disaster rescue, offshore operation, battlefield unmanned areas, anti-terrorism maintenance, space flight tests and the like.
The invention is realized by the following steps:
a frequency conversion forwarding device based on technology detection technology in a space-based relay communication enhancement system comprises an air signal forwarding subsystem and a ground signal forwarding subsystem; the frequency conversion repeater in the aerial signal forwarding subsystem is positioned at a relay load of the unmanned aerial vehicle, fast searches and receives an uplink signal through an antenna, then up-converts the received VHF signal into a signal of an L frequency band, and the signal is amplified and then is forwarded downwards through the antenna; the frequency conversion repeater in the ground signal forwarding subsystem is used for receiving downlink signals forwarded in the air, converting the downlink signals into original wave band signals through the frequency conversion repeater through down conversion, outputting the original wave band signals to an antenna for forwarding after frequency selection processing, and supplying the original wave band signals to adjacent ultrashort wave communication equipment for use.
The frequency conversion repeater in the air signal forwarding subsystem is divided into two parts, namely an antenna and a communication process: the antenna performs transparent forwarding after detecting and receiving and frequency conversion processing on a communication signal sent by the ground equipment; the frequency conversion repeater completes frequency conversion, amplification and forwarding of signals and is divided into a plurality of subunits such as frequency selection amplification, frequency conversion, a local oscillator network and a power amplifier; the remote measurement and control module is a flight control module of the ground-to-unmanned aerial vehicle; the frequency selection amplifying module filters and amplifies the detected electric wave, and then provides the electric wave to the frequency conversion unit; the frequency conversion module is responsible for up-converting the radio waves after frequency selection to an L frequency band, the local oscillator network is responsible for generating local oscillator frequency signals, and the power amplifier module is responsible for amplifying the signals after frequency conversion and then transmitting the signals downwards through an antenna.
The frequency conversion repeater in the air signal forwarding subsystem is provided with a power supply interface, a communication interface, a radio frequency interface and a 1pps interface; the power interface is internally provided with a battery which supports external power supply and battery charging; the communication interface is used for connecting a data line and supporting local parameter configuration; the radio frequency interface is used for connecting an antenna; the 1pps interface is used for internal clock synchronization.
The frequency conversion repeater in the air signal forwarding subsystem firstly utilizes an uplink signal receiving antenna to detect and receive signals transmitted by user equipment; then, the received signals are sequentially processed by a frequency selection amplifying module, a frequency conversion module and a power amplification module; the frequency selection amplification module performs frequency selection and low-noise amplification on the received signals: firstly, carrying out attenuation self-control on received electric waves by using an amplitude limiter in a frequency-selecting amplification module to obtain signals which are positioned in a frequency range of 30M-88MHz and have stable power, and carrying out primary amplification by using a low-noise amplifier; then, a 5-order LC filter is adopted for frequency selection, and out-of-band interference signals are suppressed; the filtered signal and the useful signal secondarily extracted by the detector pass through an automatic level control device to obtain a stable level; finally, the signal is secondarily amplified by an amplifier in the frequency selection amplifying module and is transmitted to the frequency conversion module;
in the frequency conversion module, the up-conversion of the radio wave after frequency selection and amplification is completed: firstly, a serial peripheral equipment interface device and a clock device are utilized to ensure the continuous transmission of information from a controller; in order to better filter out unnecessary stray components caused by frequency mixing, a frequency converter in the frequency conversion module converts the processed signals into signals of a higher frequency band to obtain pure carrier signals; the processed electric wave is filtered and frequency-selected by a cavity filter, amplified by an amplifier and finally passed through an LC low-pass filter to obtain a required carrier wave;
in the power amplifier module, a carrier signal is amplified through a power amplifier: firstly, filtering clutter generated in the transmission process by a notch filter, and then stabilizing the level by using an ALC (adaptive logic controller) device and transmitting the level to a power amplifier; because the signal transmitted by the current general communication equipment is relatively wide in bandwidth and the loss of a space link is different during the signal propagation, the signals with different frequencies are compensated by utilizing an equalizer; and finally, filtering and frequency-selecting the processed signal and a useful signal extracted by a detector in the power amplification module through a cavity filter, and radiating the signal through an antenna.
The frequency conversion repeater in the ground signal forwarding subsystem is divided into an antenna and a frequency conversion repeater; the antenna receives and retransmits the frequency-converted signal of the lift-off platform after frequency recovery; the frequency-conversion repeater completes frequency-selection amplification and frequency-conversion forwarding of signals and is divided into a frequency-selection amplification subunit, a frequency conversion subunit, a local oscillator network and an ALC amplification subunit, wherein the frequency-selection amplification subunit and the frequency conversion subunit complete filtering and frequency conversion of detected and received electric waves, and the ALC amplification unit is used for ensuring that a power amplifier is kept basically stable when input signals change.
The frequency conversion repeater in the ground signal forwarding subsystem is provided with a power interface, a communication interface, a radio frequency interface and a 1pps interface; the power interface is internally provided with a battery which supports external power supply and battery charging; the communication interface is used for connecting a data line and supporting local parameter configuration; the radio frequency interface is used for connecting an antenna; the 1pps interface is used for internal clock synchronization.
The frequency conversion repeater in the ground signal forwarding subsystem firstly receives the signal forwarded by the lift-off platform by using the downlink signal receiving antenna, filters out the out-of-band signal by using the cavity filter, and then sequentially passes the received signal without the out-of-band signal through the frequency selection amplification module, the frequency conversion module and the power amplification module. The frequency selection amplifying module firstly performs frequency selection and low-noise amplification on the received signal: firstly, performing first low-noise amplification on a signal by a low-noise amplifier in a frequency-selecting amplification module, then automatically controlling the level of the amplified signal by an ALC (automatic level control) device, and finally performing secondary amplification by the amplifier and transmitting the amplified signal to a frequency conversion module;
the frequency conversion module carries out frequency conversion processing on the control signals transmitted by the frequency selection amplification module and the main control module: the controller signal realizes the continuous transmission of the control information through the SPI device and the clock device, and is transmitted to the frequency converter together with the signal processed by the frequency selection amplification module; the frequency converter carries out down-conversion on the transmitted signal to obtain a clean carrier wave with VHF frequency, the carrier wave is amplified by the amplifier, and finally filtering processing is carried out through the LC low-pass filter;
the power amplification module performs power amplification on the frequency-converted signal: firstly, an ALC device is used for realizing automatic level control on a signal and an amplifier is used for amplifying the signal at one time; and then, an equalizer in the power amplification module performs power compensation on signals with different frequencies and then performs secondary amplification, and finally, a 5-order LC filter is adopted to suppress interference components caused by frequency mixing and send out the signals by using an antenna in consideration of the fact that the intermediate frequency of the frequency conversion repeater is higher than the local oscillation frequency.
The invention has the beneficial effects that:
(1) the frequency conversion forwarding design based on technical investigation solves the problem of cross-regional user concurrent communication
The invention provides a technical detection-based frequency conversion forwarding design, which realizes the detection and the reception of various equipment signals in the same frequency band and the concurrent communication of multiple users in an area. In the conventional airborne platform relay, equipment with the same communication system is used as a load to be lifted into the air, and limited ground user signals are received and forwarded by using an antenna, so that point-to-point and small-quantity multipoint relay can be realized. This patent has designed the relay load that the frequency conversion that is located on the 20Km flight altitude unmanned aerial vehicle was forwardded, at first reconnoiters and receives and frequency conversion processing all signals to same frequency channel, then utilizes repeater and antenna to carry out transparent retransmission. The communication system and the communication protocol of the ground terminal do not need to be mastered, the system can realize the concurrent use of various devices, the radius of the coverage range of 50KM and more than 250 users, and the relay communication capacity is improved.
(2) The design of aerial pilot frequency forwarding solves the problem of antenna isolation
The invention provides a method for carrying a relay load on an aerial platform to relay and forward signals transmitted by a ground station, which is limited by the carrying capacity of an ascending platform, the direct forwarding of VHF signals by the load has serious same-frequency interference, and the isolation problem of a transmitting antenna and a receiving antenna is difficult to solve. The patent provides a design scheme of pilot frequency forwarding, and the problem of antenna isolation is solved.
(3) The design of ground frequency conversion forwarding solves the problem that the communication system is difficult to change
Through the development of many years, according to the actual situation, the communication systems in various regions and various fields are basically solidified, and the existing communication equipment is difficult to be updated on a large scale in a short time. The patent is to the design of ground frequency conversion repeater for the user need not to carry out extensive replacement to existing equipment, need not to change communication equipment's use habit, only needs to increase a small and exquisite, portable ground equipment, just can support the beyond visual range communication of many ultrashort wave communication equipment, has solved the difficult problem that communication system is difficult to change effectively.
Drawings
Fig. 1 is a system framework diagram of a frequency conversion forwarding device based on a technical detection technology in a space-based relay communication enhancement system of the present invention;
fig. 2 is a functional block diagram of a frequency conversion forwarding device based on a technical detection technology in the air-based relay communication enhancement system of the present invention;
fig. 3 is a frame of an air signal frequency conversion repeater design of a frequency conversion repeater based on a technical detection technology in the air-based relay communication enhancement system of the present invention;
fig. 4 is a development block diagram of an air signal frequency conversion repeater of a frequency conversion repeater device based on a technical detection technology in the air-based relay communication enhancement system of the present invention;
fig. 5 is a signal processing flow chart of an air signal frequency conversion repeater of a frequency conversion repeater device based on a technical detection technology in the air-based relay communication enhancement system of the present invention;
fig. 6 is a frame of a ground signal frequency-converting repeater design of a frequency-converting repeater based on a technical detection technique in the air-based relay communication enhancement system of the present invention;
fig. 7 is a development block diagram of a ground signal frequency conversion repeater of a frequency conversion repeater device based on a technical detection technology in the air-based relay communication enhancement system of the present invention;
fig. 8 is a signal processing flow chart of a ground signal frequency conversion repeater of a frequency conversion repeater device based on a technical detection technology in the air-based relay communication enhancement system of the present invention.
Detailed Description
The invention is further described below with reference to the figures and examples.
The scheme adopts a mode of detecting and receiving and transmitting signals by an aerial platform, and realizes intercommunication and interconnection among communication equipment in post-disaster areas, sea surfaces far away from lands, unmanned areas in wartime, and other special terrains with more mountains, jungles and the like, which lack communication relay facilities such as base stations.
After the communication guarantee begins, the unmanned aerial vehicle takes off from the rear and goes to a designated area to detect, receive and forward signals in a VHF frequency band (30M-88 MHz). The patent design adopts the flight height to reach 20 KM's long endurance unmanned aerial vehicle, and this flight height belongs to the stratosphere, and weather conditions is good, almost windless, is fit for unmanned aerial vehicle to stop for a long time, does not shelter from basically between ground radio station and the unmanned aerial vehicle simultaneously, and the antenna angle of elevation is big, but the radio wave transmission path loss is relatively big, so can only ensure the ultrashort wave equipment initial emission demand of ground big transmitting power (50W). Considering the isolation influence of the receiving and transmitting antenna, the aerial repeater is designed into a pilot frequency forwarding working mode based on a technical detection thought, the aerial load antenna can detect and receive radio station signals of various types in the same frequency band, and then the received VHF frequency band signals are converted to another L frequency band (1.35G-1.8GHz) by using the frequency conversion forwarding equipment. The design mode ensures that the aerial relay load can complete the receiving and sending of signals through one antenna, and ensures that no mutual interference exists between the received and sent signals. Because the frequency of the downlink signal is not matched with ground equipment, a frequency conversion repeater is added near the ground ultrashort wave radio station to convert the frequency of the L waveband into the VHF working frequency band and then transmit the frequency to one or a group of ultrashort wave radio stations of the accessory. Because the ground signal frequency conversion repeater is close to the ultra-short wave radio station, the transmitting power and the size of a transmitting and receiving antenna of the device can be designed to be small, and the device becomes a signal enhancer accompanying the ultra-short wave radio station. Based on the above design concept, the interconnection and intercommunication of the ultrashort wave communication equipment in a certain area and under the condition of beyond visual range can be realized without changing the communication system, and the working principle of the interconnection and intercommunication is shown in fig. 2.
1. The main objective of the aerial signal forwarding subsystem is to convert the VHF radio wave signals transmitted by the user station into L-band radio wave signals through frequency conversion, and to transmit the L-band radio wave signals through an antenna after amplification, and the subsystem needs to be carried on the unmanned aerial vehicle.
(1) Air signal frequency conversion repeater design
The air signal forwarding subsystem is mainly divided into an antenna and a communication processing part: the antenna mainly performs transparent forwarding after detecting and receiving and frequency conversion processing on a communication signal sent by ground equipment; the frequency conversion repeater mainly completes frequency conversion, amplification and forwarding of signals and is divided into a plurality of subunits of frequency selection amplification, frequency conversion, a local oscillator network, power amplification and the like; the telemetering remote control module is mainly a flight control module facing the unmanned aerial vehicle. The frequency-selecting amplifying unit mainly filters and amplifies the detected electric wave, and then supplies the electric wave to the frequency conversion unit. The frequency conversion unit is responsible for up-converting the radio waves after frequency selection to an L frequency band, the local oscillator network is responsible for generating local oscillator frequency signals, and the power amplification unit is responsible for amplifying the signals after frequency conversion and then transmitting the signals downwards through an antenna. As an important feature of this patent, in the process of processing the detected radio wave signals, the frequency conversion repeater does not need to master the information protocol followed by the propagation signals, which means that the module omits the process of analyzing the protocol before signal conversion in the process of processing the radio waves, thereby greatly enhancing the communication relaying and ensuring capabilities of this system to various systems in the future, and the design framework of the frequency conversion repeater of this sub-system is shown in fig. 3.
(2) Air signal frequency conversion repeater interface
The main interfaces of the air signal frequency conversion repeater are shown in table 1:
table 1 table for main interface of frequency conversion repeater for aerial signal
| Serial number | Name (R) | Function and description | Type (B) |
| 1 | Power supply interface | Built-in battery supporting external power supply and battery charging | Not less than +28V/3A |
| 2 | Communication interface | Supporting local parameter configuration | Support USB or RS-232 |
| 3 | Radio frequency interface | Input antenna and output antenna interface | SMA 50ohm |
| 4 | 1pps interface | For internal clock synchronization, external provision | SMA 50ohm |
(3) Frequency conversion repeater development scheme
According to the functional requirements of the subsystems, the patent designs the development scheme of the subsystems in detail, selects specific electronic devices in each functional unit, and the development block diagram is shown in fig. 4.
After the system starts to work, the air signal forwarding subsystem firstly detects and receives signals transmitted by user equipment by using an uplink signal receiving antenna. Then, the frequency selection amplifying module performs frequency selection and low noise amplification on the received signals: firstly, the amplitude limiter is used for carrying out attenuation self-control on received electric waves, signals which are located in a frequency range of 30M-88MHz and have relatively stable power are obtained, and a Low Noise Amplifier (LNA) is used for carrying out first amplification. And then, a 5-order LC filter is adopted for frequency selection, and out-of-band interference signals are suppressed. The filtered signal and the useful signal secondarily extracted by the detector are processed by an Automatic Level Control (ALC) device to obtain a more stable level. And finally, secondarily amplifying the signals by an amplifier and transmitting the signals to a frequency conversion module.
In the frequency conversion module, the up-conversion of the radio wave after frequency selection and amplification is completed: a Serial Peripheral Interface (SPI) device and a clock device are first utilized to ensure continuous transmission of information from the controller. In order to better filter out unnecessary stray components caused by frequency mixing, the frequency converter converts the processed signals into signals of a higher frequency band, and pure carrier signals are obtained. The processed electric wave is filtered and frequency-selected by a cavity filter, amplified by an amplifier and finally passed through an LC low-pass filter to obtain the required carrier.
In the power amplifier module, a carrier signal is amplified through a power amplifier: firstly, clutter generated in the transmission process is filtered by a notch filter, and then the level is stabilized by an ALC device and is transmitted to a power amplifier. Since the signal transmitted by the current general communication equipment is relatively wide in bandwidth and the loss of a spatial link during signal propagation is different, the equalizer is used for compensating the signals with different frequencies. And finally, filtering and frequency-selecting the processed signal and the useful signal extracted by the detector through a cavity filter, and radiating the processed signal and the useful signal through an antenna. The signal processing flow of the air signal forwarding subsystem is shown in fig. 5.
2. The ground signal forwarding subsystem mainly aims to convert a downlink signal forwarded by an air platform into a VHF frequency band, output the frequency-selected downlink signal to a forwarding antenna after frequency selection processing, and provide the frequency-selected downlink signal for communication equipment within a range of 10m away from the subsystem device. The device needs to be miniaturized, low in power consumption, and convenient to carry, configure and use flexibly.
(1) Ground signal frequency conversion repeater design
The ground signal forwarding subsystem is mainly divided into an antenna and a frequency conversion repeater: the antenna mainly receives and retransmits the frequency-converted signal of the lift-off platform after frequency recovery; the frequency-conversion repeater mainly completes frequency-selection amplification and frequency-conversion retransmission of signals, is similar to an aerial signal retransmission sub-system, and is divided into a plurality of sub-units such as frequency-selection amplification, frequency conversion, a local oscillator network and ALC amplification, wherein the frequency-selection amplification and frequency conversion unit mainly completes filtering and frequency conversion of detected and received electric waves, and the ALC amplification unit is mainly used for ensuring that a power amplifier is basically stable when input signals are greatly changed. The sub-system realizes the transparent forwarding of signals without mastering information protocols in the process of frequency conversion forwarding. In addition, the ground signal forwarding subsystem device is also provided with a display screen and a key, a ground user can acquire the operation information of the current whole system through equipment and can perform dynamic configuration such as frequency point switching on the ground subsystem according to requirements. The design framework of the frequency conversion repeater of the present sub-system is shown in fig. 6.
(2) Interface of ground signal frequency conversion repeater
The main interfaces of the ground signal frequency conversion repeater are shown in table 2:
table 2 main interface table of frequency conversion repeater for ground signal
| Serial number | Name (R) | Function and description | Type (B) |
| 1 | Power supply interface | External power supply and internal battery charging | Not less than 7.4V/2A |
| 2 | Communication interface | Supporting remote configuration | Support USB or RS-232 |
| 3 | Radio frequency interface | Input antenna and output antenna interface | SMA 50ohm |
| 4 | 1pps interface | For internal clock synchronization, external provision | SMA 50ohm |
(3) Subsystem development scheme
According to the functional requirements of the subsystems, the patent carries out detailed design on development schemes of the subsystems, selects specific electronic devices, and develops a block diagram as shown in fig. 7.
After the system starts to work, the ground signal forwarding subsystem firstly receives signals forwarded by the lift-off platform by using a downlink signal receiving antenna, filters out-of-band signals through a cavity filter, and then performs frequency selection and low-noise amplification on the received signals by using a frequency selection amplification module: firstly, the signal is subjected to low noise amplification for the first time through a Low Noise Amplifier (LNA), then the level of the amplified signal is automatically controlled by an ALC device, and finally the amplified signal is secondarily amplified by an amplifier and transmitted to a frequency conversion module.
The frequency conversion module mainly carries out frequency conversion processing on control signals transmitted by the frequency selection amplification module and the main control module: the controller signal realizes the continuous transmission of the control information through the SPI device and the clock device, and is transmitted to the frequency converter together with the signal processed by the frequency selection amplification module. The frequency converter carries out down-conversion on the transmitted signals to obtain clean carrier waves with VHF frequency, the carrier waves are amplified by the amplifier, and finally filtering processing is carried out through the LC low-pass filter.
The power amplification module performs power amplification on the frequency-converted signal: the signal is automatically level-controlled by an ALC device and is amplified by an amplifier at one time. And then, carrying out power compensation on signals with different frequencies by an equalizer and then carrying out secondary amplification, considering that the intermediate frequency of the frequency conversion repeater is much higher than the local oscillation frequency, finally adopting a 5-order LC filter to inhibit interference components caused by frequency mixing, and sending the signals by using an antenna. The signal processing flow of the terrestrial signal forwarding subsystem is shown in fig. 8.
3. System index
3.1 user characteristic index
And analyzing and calculating according to the obtained user parameter information, wherein the maximum transmitting power of the ground terminal is 50W (47dBm), the height of the unmanned aerial vehicle is 20Km, the ground coverage radius is 50Km, the working frequency band of the terminal is 30-88M, and the frequency band after up-conversion is selected from the L wave band (1.35G-1.8G). In order to perform simulation verification on a technical product, link calculation is performed by using system index budget: respectively taking a lower limit (30MHz) and an upper limit (88MHz) of a VHF communication frequency band and an upper limit (1.8GHz) of an L communication frequency band, respectively calculating the link loss of electric waves of the extreme frequencies at the farthest (53.85KM) distance and the nearest (20KM) distance, combining gains of two repeaters for the electric waves of different frequency bands, further obtaining the entrance level, the output power and the carrier-to-noise ratio (C/N) of a link reaching an air signal forwarding subsystem (V-L repeater) and a ground signal forwarding subsystem (L-V repeater) (wherein the noise coefficient (NF) of the V-L repeater is set to be 5dB, the NF of the L-V repeater is set to be 3dB, and the carrier bandwidth is set to be 25KHz), and respectively obtaining the user characteristics of each repeater: :
through data calculation and sorting, user characteristics of the signal frequency conversion repeater in the air at the closest distance and the farthest distance respectively can be obtained, as shown in table 3.
TABLE 3 subscriber profiles for frequency translating repeaters
Similarly, the user characteristic table of the terrestrial signal frequency conversion repeater is shown in table 4.
TABLE 4 subscriber profiles of frequency-converting repeaters for ground signals
Budgeting is carried out through the given user transmitting power and the link loss of an application scene, and it is firstly demonstrated that the link design meets the requirement of the user minimum receiving level, and the input C/N value of the worst condition of the whole link signal is 10.69 dB. The user terminal NF is assumed to be 3dB, and the demodulation threshold required by the FM radio station can also be met (simulation: 12.5K bandwidth corresponds to 4dB of the demodulation threshold, and 25K bandwidth corresponds to 7dB of the demodulation threshold). According to the operation on the application scene and the link loss, the basic index requirements of the two repeaters such as gain, power, NF and the like can be obtained, and a basis is provided for the index design of the system.
3.2. Performance index
3.2.1 aerial Signal Forwarding subsystem
(1) Basic index
According to the application scenario and the index budget, the basic index requirements of the air signal frequency conversion repeater are as shown in table 5:
table 5 basic index table of air signal frequency conversion repeater
| Item | Value of | Unit of |
| Repeater ALC level | 25 | dBm |
| Repeater gain (88MHz) | 75 | dB |
| Transponder gain (30MHz) | 66 | dB |
| Output power of repeater | 16～25 | dBm |
| Equalizer compensation | 9 | dB |
| Noise figure | 5 | dB |
| Receiving frequency range | 30～88 | MHz |
| Range of retransmission frequencies | 1.35～1.80 | GHz |
| Repeating frequency stepping | 1 | MHz |
| Frequency accuracy | 0.01 | ppm |
| Transponder height requirement | 20 | Km |
| Power consumption | 50 | W |
| Size of | 300*200*50 | mm |
| Weight (without antenna) | 8 | Kg |
(2) Power index of power amplifier
The frequency conversion repeater in the air signal forwarding subsystem mainly completes the detection and frequency conversion of the VHF frequency band electric wave and the forwarding of the VHF frequency band electric wave. Compared with the downlink forwarding link, the uplink link has smaller loss, and the index of the receiver is easier to realize. Therefore, the number of supportable users of the repeater after frequency conversion is mainly considered, and the more the number of the supported concurrent users is, the larger the power amplification power of the repeater is. The air signal frequency conversion repeater needs to be loaded on the unmanned aerial vehicle, and due to the fact that the endurance of the unmanned aerial vehicle is limited, the selection of the power amplification power of the frequency conversion repeater is calculated.
Selecting a 50W power amplifier, according to a free space electric wave transmission path loss formula, taking 50KM as a horizontal distance, calculating the farthest distance path loss of 105.96dB by taking the height of an unmanned aerial vehicle as 20KM, and estimating the transmitting power of a subscriber station according to 47dBm (50W): the minimum value of the output power of the power amplifier is 16.4dBm, and the C/N of the whole forwarding link is 10.69dB at the moment; the IM3 is determined by the fact that the energy of the interference falling to the ground at the farthest distance is smaller than or equal to the background noise, the near interference is large, the far interference is small, in order to reduce the intermodulation interference caused by a nonlinear device, the ground user station obtains a better voice effect, and the IM3> -31dBc is obtained by combining the theory and engineering experience of IP 3. According to the IM3 limiting conditions and the determined number of concurrent users, the maximum power output is 40.37dBm, the drain power consumption is 54.56W, and the user quantity estimation result of 50W power amplifier power is shown in Table 6.
User quantity estimation of table 650W power amplifier power
The factors such as the cruising ability and the intermodulation interference of the unmanned aerial vehicle during long-endurance are comprehensively considered, 50W of power amplification power serving as an air signal forwarding subsystem is selected, and 250 users can be simultaneously supported for concurrent communication when the ground platform transmitting power is 50W.
3.2.2 ground Signal Forwarding subsystem
(1) Basic index
According to the application scenario and the index budget, the basic index requirements of the terrestrial signal frequency conversion repeater are as shown in table 7:
table 7 basic index table of ground signal frequency conversion repeater
| Item | Value of | Unit of |
| Repeater ALC level | 10 | dBm |
| Equalizer | 9 | dB |
| Transponder gain (1.8GHz) | 61 | dB |
| Transponder gain (1.35GHz) | 71 | dB |
| Distance of transponder from user | <10 | m |
| Receiving frequency range | 1.35～1.80 | GHz |
| Receive frequency adjustment step | 1 | MHz |
| Frequency accuracy | 0.01 | ppm |
| Range of retransmission frequencies | 30～88 | MHz |
| Power consumption | 5 | W |
| Size of | 150*100*40 | mm |
| Weight (without antenna) | 1 | Kg |
(2) Power index of power amplifier
The frequency conversion repeater in the ground signal forwarding subsystem needs to complete two main tasks: receiving and frequency conversion of L-frequency range electric wave, and forwarding of VHF frequency range electric wave. Because the ground signal forwarding subsystem is small in size and is close to the ultra-short wave communication equipment (less than 10m), the power of frequency conversion forwarding can be designed to be small and is easy to realize. The transponder is focused on the receiving sensitivity of the transponder to the L-band radio wave, and the signal strength of the aerial signal transponder under the worst condition and the radio wave propagation path loss of the frequency band (1.8GHz, 53.85KM) are considered to be 132.7dB, and are calculated by a link: the sensitivity of the ground frequency converter receiver needs to reach-116.3 dBm; as the receiving sensitivity of the subscriber station is-113 dBm, the propagation distance is less than 10m, and the power amplification frequency is 5W, the receiving and transmitting requirements can be met.
The invention solves the problem of cross-regional user concurrent communication based on the technical detection frequency conversion forwarding design. By providing a frequency conversion forwarding design based on technical detection, the detection and the reception of various equipment signals in the same frequency band in an area and the concurrent communication of multiple users are realized. In the conventional airborne platform relay, equipment with the same communication system is used as a load to be lifted into the air, and limited ground user signals are received and forwarded by using an antenna, so that point-to-point and small-quantity multipoint relay can be realized. This patent has designed the relay load that the frequency conversion that is located on the 20Km flight altitude unmanned aerial vehicle was forwardded, at first reconnoiters and receives and frequency conversion processing all signals to same frequency channel, then utilizes repeater and antenna to carry out transparent retransmission. The communication system and the communication protocol of the ground terminal do not need to be mastered, the system can realize the concurrent use of various devices, the radius of the coverage range of 50KM and more than 250 users, and the relay communication capacity is improved.
The invention solves the problem of antenna isolation based on the design of air pilot frequency forwarding. The relay load is carried on the aerial platform to relay and forward signals transmitted by the ground station, the carrying capacity of the lift-off platform is limited, the direct forwarding of VHF signals by the load has serious same-frequency interference, and the isolation problem of the transmitting and receiving antenna is difficult to solve. The patent provides a design scheme of pilot frequency forwarding, and the problem of antenna isolation is solved.
The invention solves the problem that the communication system is difficult to change based on the design of ground frequency conversion forwarding. Through the development of many years, according to the actual situation, the communication systems in various regions and various fields are basically solidified, and the existing communication equipment is difficult to be updated on a large scale in a short time. The patent is to the design of ground frequency conversion repeater for the user need not to carry out extensive replacement to existing equipment, need not to change communication equipment's use habit, only needs to increase a small and exquisite, portable ground equipment, just can support the beyond visual range communication of many ultrashort wave communication equipment, has solved the difficult problem that communication system is difficult to change effectively.
The method of carrying out the present invention has been described in detail with reference to the examples, but the present invention is not limited to the examples described above, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art. The prior art can be adopted for the content which is not described in detail in the specification of the invention.
Claims (5)
1. A frequency conversion forwarding device based on technology detection technology in a space-based relay communication enhancement system is characterized in that: the system comprises an air signal forwarding subsystem and a ground signal forwarding subsystem; the system comprises an aerial signal forwarding subsystem, a frequency conversion repeater, an uplink signal receiving antenna, a frequency conversion repeater, a frequency conversion antenna and a frequency conversion repeater, wherein the frequency conversion repeater in the aerial signal forwarding subsystem is positioned on an unmanned aerial vehicle, the uplink signal is quickly searched and received through the uplink signal receiving antenna of the frequency conversion repeater in the aerial signal forwarding subsystem, then the detected VHF signal is up-converted into a signal of an L frequency band, and the signal is; the frequency conversion repeater in the ground signal forwarding subsystem receives downlink signals forwarded in the air through a downlink signal receiving antenna, converts the downlink signals into original waveband signals through down conversion, outputs the original waveband signals to an equipment signal forwarding antenna of the ground signal frequency conversion repeater after frequency selection processing, and forwards the original waveband signals to be used by adjacent ultrashort wave communication equipment;
the frequency conversion repeater in the air signal forwarding subsystem is divided into an antenna and a frequency conversion forwarding unit: detecting and receiving a communication signal sent by a ground communication terminal by an uplink signal receiving antenna of a frequency conversion repeater in the air signal forwarding subsystem; the frequency conversion forwarding unit is responsible for communication processing, completes frequency conversion, amplification and forwarding of signals, and is divided into a frequency selection amplification module, a frequency conversion module, a local oscillation network, a power amplification module and a remote measurement and control module; the remote measurement and control module is a flight control module of the ground-to-unmanned aerial vehicle; the frequency selection amplifying module filters and amplifies the detected electric wave, and then provides the electric wave to the frequency conversion module; the frequency conversion module is responsible for up-converting the radio waves after frequency selection to an L frequency band, the local oscillator network module is responsible for generating local oscillator frequency signals, and the power amplification module is responsible for amplifying the signals after frequency conversion and then down-converting the amplified signals through a down signal forwarding antenna of a frequency conversion repeater in the air signal forwarding subsystem;
the frequency conversion repeater in the air signal forwarding subsystem firstly detects and receives communication signals sent by ground equipment by using an uplink signal receiving antenna; then, the received signals sequentially pass through a frequency selection amplifying module, a frequency conversion module and a power amplification module; the frequency selection amplification module performs frequency selection and low-noise amplification on the received signals: firstly, carrying out attenuation self-control on received electric waves by using an amplitude limiter in a frequency-selecting amplification module to obtain signals which are positioned in a frequency range of 30M-88MHz and have stable power, and carrying out primary amplification by using a low-noise amplifier; then, a 5-order LC filter is adopted for frequency selection, and out-of-band interference signals are suppressed; the filtered signal and the useful signal secondarily extracted by the detector pass through an automatic level control device to obtain a stable level; finally, the signal is secondarily amplified by an amplifier in the frequency selection amplifying module and is transmitted to the frequency conversion module;
in the frequency conversion module, the frequency-selective amplified electric wave is up-converted: firstly, a serial peripheral equipment interface device and a clock device are utilized to ensure the continuous transmission of information from a controller; in order to better filter out unnecessary stray components caused by frequency mixing, a frequency converter in the frequency conversion module converts the processed signals into signals of a higher frequency band to obtain pure carrier signals of L frequency; the processed electric wave is filtered and frequency-selected by a cavity filter in the frequency conversion module, amplified by an amplifier and finally passed through an LC low-pass filter to obtain a required carrier; in the power amplifier module, a carrier signal is amplified through a power amplifier: firstly, filtering clutter generated in the transmission process by a notch filter, and then stabilizing the level by using an ALC (adaptive logic controller) device and transmitting the level to a power amplifier; finally, the processed signals and useful signals extracted by a detector in the power amplification module are filtered and frequency-selected by a cavity filter in the power amplification module and then radiated out through a downlink signal forwarding antenna of an air signal frequency conversion repeater;
ALC refers to automatic level control.
2. The frequency conversion forwarding device based on the technical detection technology in the air-based relay communication enhancement system according to claim 1, characterized in that: the frequency conversion repeater in the air signal forwarding subsystem is provided with a power interface, a communication interface, a radio frequency interface and a 1pps interface; the power interface is internally provided with a battery which supports external power supply and battery charging; the communication interface is used for connecting a data line and supporting local parameter configuration; the radio frequency interface is used for connecting an antenna; the 1pps interface is used for internal clock synchronization.
3. The frequency conversion forwarding device based on the technical detection technology in the air-based relay communication enhancement system according to claim 1, characterized in that: the frequency conversion repeater in the ground signal forwarding subsystem is divided into an antenna and a frequency conversion forwarding unit; a downlink signal receiving antenna of the ground signal frequency conversion repeater receives signals after the frequency conversion of the lift-off platform; the frequency conversion forwarding unit completes frequency selection amplification and frequency conversion forwarding of signals and is divided into a frequency selection amplification module, a frequency conversion module, a local oscillator network and an ALC (automatic level control) amplification module, wherein the frequency selection amplification module and the frequency conversion module complete filtering and frequency conversion of radio waves received by detection, and the ALC amplification module is used for ensuring that a power amplifier is kept basically stable when input signals change.
4. The frequency conversion forwarding device based on the technical detection technology in the air-based relay communication enhancement system according to claim 3, characterized in that: the frequency conversion repeater in the ground signal forwarding subsystem is provided with a power interface, a communication interface, a radio frequency interface and a 1pps interface; the power interface is internally provided with a battery which supports external power supply and battery charging; the communication interface is used for connecting a data line and supporting local parameter configuration; the radio frequency interface is used for connecting an antenna; the 1pps interface is used for internal clock synchronization.
5. The frequency conversion forwarding device based on the technical detection technology in the air-based relay communication enhancement system according to claim 4, characterized in that: the frequency conversion repeater in the ground signal forwarding subsystem firstly receives signals forwarded by the lift-off platform by using a downlink signal receiving antenna, filters out-of-band signals by using a cavity filter, and then sequentially passes the received signals with the out-of-band signals removed through a frequency selection amplification module, a frequency conversion module and a power amplification module; the frequency selection amplifying module is used for performing frequency selection and low-noise amplification on the received signal: firstly, performing first low-noise amplification on a signal by a low-noise amplifier in a frequency-selecting amplification module, then automatically controlling the level of the amplified signal by an ALC (automatic level control) device, and finally performing secondary amplification by the amplifier and transmitting the amplified signal to a frequency conversion module;
the frequency conversion module carries out frequency conversion processing on the control signals transmitted by the frequency selection amplification module and the main control module: the controller signal realizes the continuous transmission of the control information through the SPI device and the clock device, and is transmitted to the frequency converter together with the signal processed by the frequency selection amplification module; the frequency converter carries out down-conversion on the transmitted signal to obtain a clean carrier wave with VHF frequency, the carrier wave is amplified by the amplifier, and finally filtering processing is carried out through the LC low-pass filter;
the power amplification module performs power amplification on the frequency-converted signal: firstly, an ALC device is used for realizing automatic level control on a signal and an amplifier is used for amplifying the signal at one time; then, an equalizer in the power amplification module performs power compensation on signals with different frequencies, then performs secondary amplification, finally adopts a 5-order LC filter to suppress interference components caused by frequency mixing, and sends out the signals by using an equipment signal forwarding antenna of the ground signal frequency conversion repeater;
SPI refers to a serial peripheral interface.
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| CN1476183A (en) * | 2003-07-18 | 2004-02-18 | �����ƶ�ͨ���豸����˾ | Method and device for proceeding bidirectional synchronous translate against radio signal |
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