RU2224373C2 - Technical control station for signals arriving from satellite communication lines - Google Patents

Abstract

FIELD: radio and digital engineering; processing signals of satellite communication line. SUBSTANCE: proposed station for controlling signals coming from satellite communication lines of "one-channel-per-carrier" type that affords detection of coverage areas has series-connected antenna with guiding system, polarizer, and two reception and demodulation channels, each incorporating series-connected low- noise amplifiers, frequency changers, radio receiver, optimal filtering unit, and coherent demodulator. Frame synchronizer incorporating burst separator is inserted in second channel for processing time-division multiple access signals. Then digital signals received are processed by hardware or software means. EFFECT: enhanced reliability of signal processing and coverage area detection. 1 cl, 2 dwg

Description

 The invention relates to the field of radio engineering and digital technology and can be used to control signals of satellite communication lines of the type "one channel per carrier" (OKN). In recent years, such communication systems have become widespread (VSAT, Spade communication systems), etc. due to the simplicity of the organization of communication and the maximum satisfaction of consumer needs.

 Communication system channels can be assigned to individual consumers, work according to a schedule or distribution, depending on the priorities of subscribers, their importance and priority.

 At the same time, such communication systems have a number of features.

 In particular, to ensure the maximum amount of information transmitted in the allotted frequency band, signals with left and right polarization are used, and vocoder transmissions are widely used to provide information compression and, accordingly, reduce the frequency band.

 Most channels operate in multiple access mode based on frequency division multiplexing (FDMA), individual channels can operate in multiple access mode based on time division (TDMA). At the same time, superframe (frame) clock signals can be transmitted both in the barrel of the own repeater and in the barrel of the repeater of another communication system. Those. processing of individual channels with TDMA is possible only when receiving and processing the corresponding trunk of this or another communication system in which control and synchronization signals are transmitted for the channel with TDMA [1, p. 68].

 Currently, there are several thousand channels OKN. Therefore, the issue of monitoring the signals of such communication lines is relevant.

 In [2], a description is given of a satellite communications signal technical control station adopted as a prototype, which contains a series-connected antenna with a guidance system, a low-noise amplifier (LNA), a frequency converter, a radio receiver (RPU), an optimal filtering unit, a splitter, a coherent switch a phase demodulator of signals with FDMA, a second switch, a storage buffer, a personal computer (PC) and a software unit, as well as a coherent phase demodulator of a signal connected in series fishing with mdvr and frame synchronizer with an arbitrary packet selector. At the same time, the input of the signal demodulator from TDMA is connected to the second output of the splitter, and the output of the frame synchronizer with an arbitrary packet isolator is connected to the second input of the second switch. The station also contains a code division signal converter (CDMA) to FDMA, while the input of a multiple access converter based on code division multiplexing (CDMA) into FDMA is connected to the second output of the splitter, and the output to the second input of the first switch.

 The disadvantage of the prototype is the lack of a polarizer in it, which ensures the separation of signals with right and left polarization, the inability to process signals with left and right polarization, the inability to process signals with TDMA when control signals and superframe (frame) synchronization are transmitted in another trunk, the inability to access information OKN signals when using vocoder transmissions, as well as the lack of quality control of channel information by hardware.

 The aim of the invention is the creation of a station for technical control of signals from the OKN taking into account the peculiarities of the formation of signals and the interaction of such communication systems to ensure quality control of received information and areas of reliable access to the signals of the OKN.

 To achieve this goal, a technical monitoring station is proposed that contains an antenna with a guidance and tracking system, a serial LNA and a frequency converter, a series-connected RPU, an optimal filtering unit, a coherent phase demodulator of signals with TDMA and FDM, a frame synchronizer with the selection of an arbitrary packet, a switch, storage buffer, PC and software unit, as well as a second switch.

 According to the invention, a polarizer, a second LNA and a frequency converter, the output of which through a second switch is connected to the input of the RPU, are introduced into the station in series. In this case, the antenna output is connected to the LNA input through the polarizer. A noise-immunity decoder with a de-interleaver, a descrambler and a differential decoder, the output of which through the first switch is connected to a series-connected demultiplexer and channel separating device for decoding vocoder transmissions, and to the input of the storage buffer are also introduced into the station. The second output of the polarizer is connected to the first LNA. To ensure control of communication systems in which synchronization and control signals are transmitted in another trunk, the station includes a second channel similar to the first one, which includes a series-connected antenna with a guidance and tracking system, a polarizer, two LNAs, two frequency converters, as well as in series connected RPUs, filtering unit, coherent phase demodulator of signals with TDMA and FDMA, synchronizer with the allocation of an arbitrary packet, noise-resistant decoder with deinterleaver, descrambler and different A potential decoder whose output through the first switch is connected to the input of the demultiplexer and to the input of the storage buffer. In this case, the second outputs of the synchronizers of the first and second paths are connected to the second inputs of the synchronizers of the second and first path, respectively, and the outputs of the converters through the second switch are connected to the RPU of the first and second paths.

The coherent phase demodulator of signals with TDMA and FDMA is made according to the Kostas scheme and contains in-phase and quadrature demodulation channels, each of which includes a phase detector, a low-pass filter (LPF), an analog-to-digital converter (ADC) and a digital filter, outputs which are connected to the first and second inputs of the carrier frequency recovery, clock recovery, automatic gain control (AGC) detector and serially connected synchronizer, deinterleaver with mehoustoychivym decoder systematic and non-systematic convolutional codes, and the differential decoder descrambler, and the entry of the input amplifier, whose output is connected to inputs of the phase detector, phase shifter 90 ^o, synthesizers recovered carrier and clock frequencies. The output of the AGC detector is connected to the second input of the input amplifier, the output of the carrier frequency recovery circuit is connected to the input of the restored carrier frequency synthesizer, the output of which is connected to the 90 ^o phase shifter input and the common mode phase detector. The output of the clock recovery circuit is connected to a clock synthesizer, and its output is connected to the inputs of the ADC and digital filters.

The proposed construction of the station provides:
- overview of the panorama of the controlled frequency range with an indication on the PC monitor;
- tuning to any channel due to the restructuring of demodulating devices;
- signal processing with left and right polarization;
- accumulation of information and determination of the type of signal;
- processing and information access to signals with FDMA and TDMA, including for channels with TDMA, in which frame synchronization signals are transmitted in the trunk with FDMA;
- vocoder gear processing;
- quality control of signals from the windows and zones of reliable access to them using both a PC and hardware.

 The combination of distinctive features and properties of the proposed station from the literature are not known, therefore, it meets the criteria of novelty and inventive step.

 In FIG. 1 shows a functional diagram of the proposed station technical control signals of satellite communication lines type OKN, figure 2 shows a more detailed functional diagram of a demodulating device.

 The station contains (figure 1) two similar paths, combined into a single unit by switches.

Each path includes a receiving antenna connected in series 1 (2) respectively with a guidance system 3 ₁ (3 ₂ ), a polarizer 4 ₁ (4 ₂ ), LNA 5 ₁ , 5 ₂ (5 ₃ , 5 ₄ ), converters 6 ₁ , 6 ₂ , (6 ₃ , 6 ₄ ), the outputs of which through the switch 7 are connected to series-connected: RPU 8 ₁ (8 ₂ ), filtering unit 9 ₁ (9 ₂ ), signal demodulation unit with FDMA and TDMA 10 ₁ (10 ₂ ), synchronizer 11 ₁ (11 ₂ ), noise-resistant decoder with de-interleaver 12 ₁ (12 ₂ ), descrambler 13 ₁ (13 ₂ ), differential decoder 14 ₁ (14 ₂ ).

The second outputs of the synchronizers 11 ₁ (11 ₂ ), and the outputs of the differential decoders 14 ₁ (14 ₂ ) through the switch 15 are connected to the inputs of the series-connected storage buffer 16, PC 17 and the software unit (software) 18, as well as to the input of the series-connected demultiplexer 19, channels of separating devices (HLC) 20. In this case, the third outputs of the synchronizers 11 ₁ (11 ₂ ) are connected to the second inputs of the synchronizers 11 ₂ (11 ₁ ).

The station has three operating modes:
a) the control mode of the signals of one communication system, when information, control signals and clock signals are transmitted in one trunk;
b) the control mode of the signals of two communication systems, when information, control and synchronization signals are transmitted in their trunks for each communication system;
c) the control mode of two communication systems, when the control and synchronization signals of the first communication system are transmitted in another trunk of the same or another communication system.

 The station in mode a) operates as follows.

Antenna 1 using the guidance system 3 ₁ is aimed at the object of interest. The signal received by antenna 1 through the polarizer 4 ₁ enters two channels of signal reception: with left and right polarization.

In the first channel, the signal (suppose with left polarization) through LNA 5 ₁ , converter 6 ₁ , switch 7, RPU 8 ₁ , filtering unit 9 ₁ , is fed to the signal demodulator with TDMA 10 ₁ .

The demodulator 10 ₁ can operate in the panorama overview and demodulation of one of the selected signals, both with FDMA, and with mdvr. In the panorama overview mode, the demodulator 10 _{1 is} tuned in the range of controlled frequencies and its responses through the switch 15 and the accumulation buffer 16 are received in the PC 17 ₁ , which processes the responses of the demodulator 10 ₁ and indicates the loading of the frequency range on the monitor included in the PC.

In demodulation mode, the demodulator 10 _{1 is} tuned to one of the signals of interest and performs coherent signal demodulation. Next, in block 11, the clock signal is allocated, in block 12 ₁ - signal de-interleaving and noise-resistant decoding of systematic and unsystematic convolutional codes, in block 13 ₁ - descrambling, in block 14 ₁ - differential decoding.

 Next, a digital signal accompanied by a clock frequency through a switch 15 enters the storage buffer 16, from which it is pumped to a personal computer 17, in which the signal quality (probability of character distortion), as well as signal quality programs ( probability of character distortion), as well as software channel information allocation and decoding of vocoder transmissions.

 At the same time, the digital signal through the switch 15 is fed to the demultiplexer 19, in which the hardware allocates the clock signal and the digital stream is divided into service and information bits. Next, the signal enters the HVAC20, in which the channel information is extracted, its decoding, including demodulation of vocoder transmissions.

In mode b), the second signal path works similarly (suppose with the right polarization). The signal from the antenna 2 through blocks 4 ₂ , 5 ₄ , 6 ₄ , 7, 8 ₂ , 9 _{2 is} fed to a coherent signal demodulator with TDMA 10 ₂ , which is converted into a digital stream.

Next, the signal, accompanied by a clock frequency, is fed to the frame synchronizer 11 ₂ , in which the frame sync signal is allocated and any packet is allocated with reference to the clock signal.

Next, the signal through blocks 12 ₂ , 13 ₂ , 14 ₂ enters the switch 15, and from it the signal enters the storage buffer 16, PC 17, in which, according to the software of block 18, the signal information is processed and allocated with an assessment of its quality.

In mode c), when (suppose in the first path) there is no control and synchronization signal in the processed signal, the path works as in modes a) and b), but the synchronization signal in the first path to block 11 ₁ is supplied from block 11 _{2 of the} second path .

According to the synchronization signal, the first path then functions as in mode a). The second path can work similarly when the synchronization signal to block 11 ₂ is supplied from block 11 _{1 of the} first path.

 Blocks 1, 2 ... 9, 11 ... 15, 19, 20 are made according to standard schemes.

A demodulator 10 ₁ , a synchronizer with a packet isolator 11 ₁ , a decoder 12 ₁ , a descrambler 13 ₁ , a decoder 14 ₁ , are made on one board. Similarly, blocks 10 ₂ , 11 ₂ , 12 ₂ , 13 ₂ , 14 _{2 are} also made on one board.

Demodulators 10 ₁ , 10 _{2 are} made according to the Kostas scheme [3, p. 291] (figure 2) and contain in-phase and quadrature demodulation channels, each of which includes a series-connected phase detector (PD) 21, 22, low-pass filter 23, 24, as well as a 90 ^o 25 phase shifter, the output of which is connected to the input of ФД22, an accelerated carrier frequency recovery circuit 26, an input amplifier 27 connected at the input, the output of which is connected to the inputs of ФД21, 22, and to the outputs of the low-pass filter 23, 24 are connected respectively in series connected analog-to-digital converter (ADC) 28, 29 and digital A new filter (DF) 30, 31, the outputs of which are connected to the first and second inputs of the accelerated restoration of the carrier frequency 26, the accelerated recovery of the clock frequency 32 of the AGC detector 33 and the frame synchronizer 34. The output of the detector 33 is connected to the second input of the amplifier 27, the circuit output 26 is connected to the input of the synthesized restored carrier frequency (HV) 35, the output of which is connected to the input of the phase shifter 25 and PD 21 in-phase channel. The output of circuit 32 is connected to a clock synthesizer 36, and its output is connected to the second inputs of the ADC 28, 29 and DF 30, 31. The output of the frame synchronizer 34 is connected to the input of the deinterleaver connected to the decoder of systematic and unsystematic convolutional codes 37, descrambler 38, and differential decoder 39.

 The demodulator works as follows.

 The input signal with a band of 36 MHz (70 ± 18 MHz) through the input amplifier 27 is fed to the PD 21, 22 to the second inputs of which the signals of the restored carrier from the VN 35 synthesizer are fed (directly to the common-mode PD21, to the quadrature channel PD22 through the phase shifter 25). The signals from the outputs of the PD 21, 22 are fed to the low-pass filter 23, 24, from the output of which the signal is fed to the ADC 28, 29, in which the signal is quantized and converted to digital form, and then to the digital filters 30, 31 in which the signal is filtered and corrected amplitude-frequency characteristics (AFC) and group delay time (GW) with a correction depth of ± 3 bits. The clock frequency on the ADC 28, 29 and DF 30, 31 is supplied from the output of the clock synthesizer often 36. The signals from the DF 30, 31 are fed to the first and second inputs of the synchronizer 34, carrier recovery circuit 26, clock recovery circuit 32 and AGC detector 33.

 The demodulator is tuned to any signal in the 36 MHz band by setting the center frequency of the signal in the synthesizer of the restored carrier 35, and tracking the restored carrier in the phase-locked loop (PLL) through the carrier recovery circuit 26.

 Similarly, the clock frequency in the synthesizer 36 is set, and the tracking of the restored clock frequency in the PLL ring is set via the accelerated clock recovery circuit 32. The input signal level is monitored in the AGC ring through the AGC detector 35. Setting parameters of devices, including digital filters 30, 31 (filter masks) are set from the PC station.

 The digital signal after the digital filters 30, 31 is fed to the frame synchronizer 34, in which a frame signal is selected that determines the beginning of the interleaver. At this signal, a block 37 is triggered, in which group errors in the digital stream are converted into single errors distributed over the frame interval, and then a noiseless decoder corrects single errors. The descrambler 38 provides descrambling of additive and multiplicative scramblers, and the differential decoder 30 eliminates the phase ambiguity of the demodulator.

 The sequence of operations and their nomenclature are set programmatically from the PC 17 of the station.

 The use of the synthesizer in the carrier and clock recovery circuits (instead of voltage-controlled oscillators) and tunable digital filters provide demodulation of phase-shifted (FM) signals in a wide speed range, and the use of an KWALCOM type integrated circuit decoder (Q190C-1S3) provides decoding of a wide class of unsystematic convolutional codes (including trellis codes).

 The proposed construction of the station and demodulating devices was tested on real communication lines and confirmed the possibility of using it to determine and control the parameters of signals of satellite communication lines (SLS) of the OKN type.

 Within the framework of the Tor development project, antennas with a guidance system, a polarizer, an LNA, a converter were developed and tested, and RPs, filtration units, CDMA and TDMA demodulators, a frame synchronizer with a packet isolator were manufactured and tested under RPM Impulse-1, cumulative buffer, PC with vocoder decoding unit, demultiplexer and HLC with vocoder decoder.

As a result of using the proposal, the following technical and economic gain was obtained:
- the station allows you to control the technical parameters of OKN type signals with access codes of FDMA and TDMA, including in the absence of superframe (frame) synchronization signals in the signal from TDMA through the use of hardware and software;
- provides a panorama overview, determining the load of the frequency plan and the ability to tune to any signal due to the possibility of rebuilding the demodulator and the use of computer technology;
- provides signal processing with left and right polarization due to the introduction of a polarizer in the station;
- vocoder transmission processing is provided due to the introduction of decoders into the HVC and PC;
- provides quality control of signals and determination of areas of reliable reception.

Literature
1. V.A. Zhilin. International satellite communication system "INMARSAT". - L .: Shipbuilding, 1988 (p. 68).

 2 Patent 2176130, Station for technical control of satellite communications signals.

 3. J. Spilker. Digital satellite communications. - M.: Communication, 1979, (p. 183).

Claims (1)

A station for technical control of satellite communication signal signals, comprising a first path, which includes an antenna with a guidance and tracking system and series-connected first low-noise amplifier and a frequency converter, as well as a series-connected radio receiver, an optimal filtering unit, a coherent phase signal demodulator with multiple access to based on time and frequency separation, a synchronizer with an arbitrary packet allocator, a first switch, a storage buffer, personal electronic computer and software unit, as well as a second switch, characterized in that a polarizer is connected in series, the input of which is connected to the antenna output, the second low-noise amplifier and frequency converter, as well as a series-connected deinterleaver with a noise-resistant decoder, input which is connected to the first output of the synchronizer, a descrambler, a differential decoder, the output of which through the first switch is connected to the input in series remote demultiplexer and channel separating device, and the output of the polarizer is connected to the input of the first low-noise amplifier, and the outputs of the converters through the second switch are connected to the input of the radio receiving device, and a second path is introduced, similar to the first and including a series-connected antenna with a guidance and tracking system, a polarizer serially connected first low-noise amplifier and frequency converter, serially connected second low-noise amplifier and other frequency converter, the inputs of both low-noise amplifiers connected to the corresponding outputs of the polarizer, and the outputs of both converters through the second switch connected to the input of a series-connected radio receiver, optimal filtering unit, coherent phase demodulator with multi-station access based on frequency and time separation, a synchronizer with an arbitrary isolator package, deinterleaver with noise-resistant decoder, descrambler and differential decoder, output which is connected to the second input of the first switch, while the third output of the synchronizer of the first path is connected to the second input of the synchronizer of the second path, the third output of the synchronizer of the second path is connected to the second input of the synchronizer of the first path, the second outputs of the synchronizers of the first and second paths are connected through the first switch to the input of the storage buffers.

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