RU2630845C1 - Compact high-speed radio-transmitting spacecraft complex - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to radio channels for transmitting digital information, specifically to space high-speed radio lines (HRL) for transmitting surveillance data from spacecrafts (SC) of Earth remote sensing (ERS). The radio-transmitting spacecraft complex comprises a quadrature modulator and an encoder placed in housings, a polarizer structurally connected to a horn antenna, a radio frequency unit in the housing of which a highly-stable master carrier-frequency generator is installed, a boost converter-adder, a bandpass filter, a solid-state power amplifier. The housings of the quadrature modulator and the encoder are fixed on the edges of the side surface of the radio-frequency unit housing. The polarizer structurally combined with the horn antenna and with a matched load. The polarizer is mounted on the radio-frequency unit housing between the quadrature modulator and the encoder. The polarizer is connected to the output of the boost-amplifying circuit of the radio-frequency unit by means of a waveguide. The horn antenna is made with a lens corrector. The polarizer is made with two inputs for the formation of left-hand and right-hand circular polarization, wherein a matched load is installed on one of the inputs, representing the waveguide portion.

EFFECT: reducing overall dimensions and weight of the product while maintaining high speed and energy indicators of information transmission.

8 cl, 9 dwg, 1 tbl

Description

FIELD OF THE INVENTION

The invention relates to radio channels for transmitting digital information, specifically to space high-speed radio links (VRL) for transmitting surveillance data from spacecraft (SC) remote sensing of the Earth (ERS).

State of the art

The radio data channel of Earth remote sensing spacecraft (ERS) is a complex compromise technical solution to ensure the highest channel capacity (hundreds of megabits per second) with relatively small mass dimensions of the antenna and equipment and low power consumption. The solution is especially difficult for remote sensing microsatellites (weighing less than 100 kg), where for conventional modern satellite transmitters and antennas there is simply not enough space and energy. So, for the Auriga microsatellite, a data channel transmitter with a speed of at least 80 Mbit / s, having a volume of less than 1000 cm ³ (a transmitter with an antenna), power consumption of not more than 15 W and a mass of not more than 1 kg is needed.

Typically, Earth remote sensing devices use data channel radio transmitters at X-band frequencies (8-12 GHz, wavelength 37-25 mm). They provide a data transfer rate of up to 320 (sometimes up to 500) Mbit / s, but have a typical mass of 3-10 kg, the volume of equipment is 1000-5000 cm ³ (without antenna), the diameter of the antenna is at least 400 mm, the power consumption is tens of watts [http: //www.irz.ru/uploads/files/cataloq_11.pdf; http://www.spacemicro.com/assets/datasheets/rf-and-microwave/uXTx-200.pdf; http://www.gd-ais.com/Documents/Space%20Electronics/SDST%20-%20DS5-813-12.pdf; http://www.syrlinks.com/en/products/x-band-transmitter-microsatellites.html; http://mmw.picocell.com/produkciya/kosmicheskaya/picostar2007/ (compact but slow)]

At the same time, the antenna size cannot be reduced without a significant loss of gain and directivity - for a typical radiation pattern width of 10 °, the antenna diameter should be 8-15 times the wavelength.

Small antennas like [http://www.sputnix.ru/en/products/microsatellites-systems/onboard-antennas-ru/item/373-rupornaya-antenna-na-osnove-patchevogo-izluchatelya-kh-diapazona], have an unacceptably low gain.

It seems promising to use higher-frequency ranges of radio waves, in particular the Ka-band (26.5-40 GHz, wavelength 11-7.5 mm).

Equipment in this range (especially antennas) can be more compact, although much more difficult to manufacture.

Known satellite transmitters of this range [http://www.cinele.com/images/space_datasheets/t-730_ka_band.pdf; http://www.spacemicro.com/assets/datasheets/rf-and-microwave/uKATx-300.pdf and antennas http://www2.I-3com.com/csw/ProductsAndServices/DataSheets/Compact_Lens_Antenna_Sales-Sheet_WEB.pdf (one of the prototypes); http://www.rymsaespacio.com/images/catalogorymsa20013.pdf pp. 25, 45] also have the size of equipment and antennas that are excessively large for microsatellites.

Known modern options for compact horn Ka-band antennas with a lens corrector, used in low-power ground equipment [http://media.wix.com/ugd/cf385b_7a8b20a4b1874d8ea3aa2725d7700488.pdf].

However, antennas of this type are not suitable for use in satellite equipment - they widely use elements made of plastic that are not suitable for use in a vacuum, their design has insufficient strength to withstand starting accelerations. Nevertheless, this type of antenna is accepted by us as a prototype.

Separate problems are the heat sink from the components of the radio transmitting complex (in the absence of convective heat transfer in vacuum) and the protection of semiconductor components from cosmic radiation. Known solutions to these problems are based on the use of sufficiently massive metal cases for each subsystem of the radio transmitting complex (wall thickness is 2-8 mm of aluminum). However, this significantly increases the mass and dimensions of the equipment.

SUMMARY OF THE INVENTION

The problem solved by the claimed invention is high-speed data transmission from the low-orbit microsatellite to the Earth in the Ka-band.

The technical result of the claimed invention is to reduce the dimensions (up to 113 × 102 × 88 mm) and weight (up to 1 kg) of the product while maintaining high speed (up to 80 Mbit / s) and energy (EIRP up to 20 dBW) indicators of information transfer.

The technical result of the claimed invention is achieved due to the fact that the compact high-speed radio transmitting complex of the spacecraft, containing a quadrature modulator and encoder located in the hulls, a polarizer structurally connected to the horn antenna, an RF unit, in the casing of which is installed a highly stable reference carrier generator of purity, increasing the converter -adder, bandpass filter, solid-state power amplifier, and the cases of the quadrature modulator and encoder are fixed to the edges the side surface of the body of the RF block, a polarizer structurally combined with a horn antenna and with a matched load is mounted on the body of the RF block between the quadrature modulator and the encoder and connected to the output of the boost-amplifying circuit of the RF block by means of a waveguide, while the horn antenna is made with a lens corrector, and the polarizer is made with two inputs for the formation of left-side and right-side circular polarization, while one of the inputs is set according to bath load, which is a section of the waveguide.

In the particular case of the implementation of the claimed invention, the power amplifier is made in the form of a semiconductor integrated circuit of the microwave range based on pseudomorphic transistors with high electron mobility.

In the particular case of the implementation of the claimed invention, the lens corrector is made on the basis of a full-aperture dielectric lens, which provides the formation of a narrow radiation pattern.

In the particular case of the implementation of the claimed invention, the horn antenna is made open to the outer surface of the spacecraft.

In the particular case of the implementation of the claimed invention, the horn antenna is made highly directional.

In the particular case of the implementation of the claimed invention, the complex is configured to use the digital broadcast standard DVB-S2.

In the particular case of the implementation of the claimed invention, the encoder is based on a programmable logic integrated circuit.

In the particular case of the implementation of the claimed invention, the complex is configured to work in the centimeter Ka-band.

The use of the centimeter range (Ka-range) with a wavelength of about 1.1 cm provides miniaturization of the high-frequency elements of the invention, such as waveguides, horn antennas, ensuring their low weight and dimensions.

The combination of such elements of the high-frequency path as: a highly stable master carrier frequency generator, step-up converter-adder, band-pass filter, solid-state power amplifier, into a single radio-frequency unit can significantly reduce the overall dimensions and weight of the unit and, as a result, the entire invention.

Placing the horn antenna and the polarizer directly at the output of the boost-amplifying circuit of the RF block allows miniaturizing the size of the entire invention, as well as reducing path loss.

The use of a miniature digital quadrature modulator, as well as an FPGA-based encoder with low weight and dimensions.

The use of miniature Micro-D connectors, which are light in weight and small in size.

The low consumption of the transmitter is ensured primarily through the use of an amplifier based on transistors, as well as the low output power of the radio frequency unit.

High performance EIRP of the product with a low level of output power of the RF block is achieved through the use of a highly directional horn antenna with a lens corrector that has a high gain.

High speed indicators of the invention are achieved through the use of the digital broadcasting standard DVB-S2 with the implementation of effective code rates and quadrature modulation.

Brief Description of the Drawings

Details, features, and advantages of the present invention follow from the following description of embodiments of the claimed technical solution using the drawings, which show:

FIG. 1 - Functional structural diagram of a radio transmitting complex.

FIG. 2 - Appearance of a radio transmitting complex.

FIG. 3 - Appearance of the radio frequency unit.

FIG. 4 - Functional diagram of the radio frequency unit.

FIG. 5 - Assembly of the encoder, quadrature modulator and RF block.

FIG. 6 - Assembly of the polarizer, matched load and horn antenna with lens corrector.

FIG. 7 - Installation of a polarizer with a horn antenna on the radio frequency unit.

FIG. 8 - Horn antenna with a lens corrector in section.

FIG. 9 - Signal constellation quadrature phase shift keying (QPSK)

In the Figures, the numbers indicate the following positions:

1 - encoder (modem with advanced error correction FEC), 2 - quadrature modulator board, 3 - highly stable master carrier frequency generator, 4 - boost converter-adder, 5 - microwave bandpass filter, 6 - microwave power amplifier, 7 - polarizer for creating circular polarization of the output signal; 8 - horn antenna (with lens corrector); 9 - microwave connecting waveguide; 10 - a subsystem of secondary power supply; 11 - coordinated load; 12 - RF cable

Disclosure of invention

The proposed design of the radio transmitting complex is shown in FIG. 2 and consists of the following subsystems:

• FPGA-based encoder (1); quadrature modulator board (2); radio frequency unit, including:

высокостабильный задающий генератор несущей частоты;

highly stable carrier frequency oscillator;

повышающий конвертер-сумматор;

step-up converter-adder;

полосового фильтра СВЧ;

microwave bandpass filter;

усилителя мощности СВЧ;

microwave power amplifier;

блок вторичного электропитания.

secondary power supply unit.

• circular polarizer;

• horn antenna with lens corrector;

• connecting waveguide;

• RF cable;

• agreed load.

The novelty of the proposed solution lies in the constructive integration of a number of subsystems, which allows to fundamentally reduce the size and weight, while maintaining a modular design.

1. A highly stable master carrier frequency generator (3), a step-up converter-adder (4), a band-pass filter (5) and a solid-state power amplifier (6) are structurally combined into a single radio-frequency unit, due to which this unit is compact. The overall dimension of the RF block is 96 × 87 × 29 cm.

The 1 GHz modulated signal received at the input of the RF block via the SMA connector is fed to the input of the boost converter, where it is added to the 25.8 GHz signal generated in the reference frequency generator. The reference frequency generator is based on a temperature compensated crystal oscillator (TLCO) and ensures the stability of the output frequency of the signal within ± 5 ppm.

The summed signal with a frequency of 26.8 GHz and a power of 9.7 dBm is fed to the input of a band-pass filter, where spurious frequencies are removed. At the output of the step-up converter of two signals (1 GHz and 25.8 GHz), intermodulation distortions occur that contain combinational components with frequencies that are the sum and difference of the fundamental and harmonic frequencies of the input signals. These products of intermodulation distortion interact with each other, creating an almost infinite series of frequency components. It is these intermodulation products that are cut off with a band-pass filter. The filter passband is 2% of the spectrum. Insertion loss on the filter is not more than 1.8 dB.

After filtering, the signal goes to the power amplifier. The amplifier is a microwave semiconductor integrated circuit (MMIC) based on pseudomorphic transistors with high electron mobility (pHEMT).

Amplifiers of this type have high characteristics of signal amplification and output power, as well as high linearity of the output signal.

The gain value of the power amplifier is 19.5 dB with the position of the one-decibel compression point in terms of the output signal level of 29 dBm.

The amplified signal is fed to the output of an RF unit with an interface for a WR-28 waveguide with a UG559 / U flange.

2. The boards of the quadrature modulator (2) and encoder (1), located in compact cases, are mechanically attached with screws to the body of the RF block, thereby ensuring the compactness of the entire assembly. The assembly of the encoder, quadrature modulator, and RF block is shown in FIG. 5.

In the encoder (1), the data is divided into blocks in accordance with the DVB-S2 digital broadcast standard, after which FEC encoding is performed on the data. The encoded data is received from the encoder (1) via the LVDS digital channel to the DAC input of the quadrature modulator board (2). The analogue sinusoidal signals received at the output of the DAC with I and Q components are fed to an input located on the same board (2), the IQ modulator. The analog quadrature components of the I and Q signals phase-modulate the frequency of the built-in reference frequency generator, after which the modulated signal at the 1 GHz reference frequency passes through the RF cable (12) to the input of the RF block.

3. The polarizer (7) is structurally combined with a horn antenna (8) and a matched load (11). The horn antenna and polarizer have a threaded connection and the antenna is directly screwed into the polarizer. Due to this, compactness of this high-frequency unit is achieved. The assembly length of the polarizer and horn antenna is 84 cm. The antenna diameter is 75 cm.

The polarizer has two inputs for the formation of left-side and right-side circular polarization. A matched load is installed on one of the inputs for matching the high-frequency path with four screws, which is a section of the WR-28 waveguide with a UG559 / U flange.

4. A polarizer (7) with a horn antenna (8) is mounted directly on the radio frequency unit using four screws. The signal from the radio frequency block enters the polarizer through a connecting waveguide (9).

The connecting waveguide is attached to the polarizer and the RF block with four screws on each side. The waveguide is WR-28 with flanges UG559 / U on both sides.

5. A correction lens is directly glued into the horn antenna to narrow the antenna pattern and thereby increase the output power flux density. Through the use of a lens corrector, the antenna radiation pattern reaches 12 ° at the level of 3 dB, and the gain is 23 dBi.

The logic of the functioning of the radio transmitting complex is presented below.

The data intended for sending arrives at the FPGA input of the encoder (1) via one of two interfaces: via the high-speed Gigabit Ethernet interface or through the SPI interface. The received data is sequentially stored in the built-in buffer RAM of the encoder with a capacity of 2048 MB.

The data received in the FPGA of the encoder is divided into data blocks (BBFRAME) in accordance with the digital broadcasting standard DVB-S2. Then these blocks arrive at the FEC encoder. FEC coding consists of two phases:

- BCH (Bowza - Chowdhury - Hockingham) coding;

- LDPC (Low Density Parity Check) encoding.

The radio transmission complex contains eleven DVB-S2 encoding modes, as shown in Table 1. The encoding mode can be changed by sending a digital control command via the SPI interface to the radio transmitting complex.

After encoding, data packets (FECFRAME) with a length of 64800 bits are converted to 64800 / ηMOD modulating symbols (ηMOD is the modulation level for QPSK = 2). Each modulating symbol is a complex vector of the format (I, Q) (where I is the phase component, Q is the quadrature component). For QPSK quadrature phase shift keying, 2 bits are used per modulating symbol. In this regard, the FECFRAME bit sequence forms QPSK modulating symbols in such a way that bits 2i and 2i + 1 form the ith QPSK symbol, where i = 0, 1, 2, ..., (N / 2) -1 and N is the size FECFRAME package. The modulation symbol set determines the type of QPSK signal constellation shown in FIG. 9.

The generated sequence of modulation symbols in digital form via the LVDS channel is input to a digital-to-analog converter (DAC) of the modulator board (2). Received at the output of the DAC analog sinusoidal signals with I and Q components are fed to the input of the IQ modulator. The analog quadrature components of I and Q signals received from the DAC modulate in phase the frequency of the built-in reference frequency generator (at a speed of up to 80 Mbit / s), after which the modulated signal is fed to the input of the RF block.

Using the SPI interface as part of the IQ modulator, the frequency of the reference oscillator can be tuned. This allows you to apply a modulated signal with the necessary parameters to the input of the RF block. In the current scheme, the output QPSK signal has a frequency of 1000 MHz and a power of 4 dBm. The signal is fed to the input of the RF block through a high-frequency semi-flexible coaxial cable (12).

The 1 GHz modulated signal received at the block input through the SMA connector goes to the input of the boost converter (4), where it is added to the 25.8 GHz signal generated in the reference frequency generator (3). The reference frequency generator is based on a temperature compensated crystal oscillator (TLCO) and ensures the stability of the output frequency of the signal within ± 5 ppm.

The summed signal with a frequency of 26.8 GHz and a power of 9.7 dBm is fed to the input of a band-pass filter (5), where spurious frequencies are removed. At the output of the step-up converter of two signals (1 GHz and 25.8 GHz), intermodulation distortions occur that contain combinational components with frequencies that are the sum and difference of the fundamental and harmonic frequencies of the input signals. These products of intermodulation distortion interact with each other, creating an almost infinite series of frequency components. It is these intermodulation products that are cut off with a band-pass filter. The filter passband is 2% of the spectrum. Insertion loss on the filter is not more than 1.8 dB.

After filtering, the signal enters the power amplifier (6). The amplifier is a microwave semiconductor integrated circuit (MMIC) based on pseudomorphic transistors with high electron mobility (pHEMT). Amplifiers of this type have high characteristics of signal amplification and output power, as well as high linearity of the output signal. The gain value of the power amplifier is 19.5 dB with the position of the one-decibel compression point in terms of the output signal level of 29 dBm.

The signal received at the output of the amplifier enters the waveguide (9) of size WR-28 with an insertion loss value of less than 0.1 dB. Thus, a signal with a frequency of 26.8 GHz and a power of 27 dBm appears at the output of the RF block. The device is powered by a stabilized voltage of 8 V.

From the waveguide connector, the signal enters the circular polarizer (7) of the horn antenna (8). The polarizer converts the input electromagnetic wave with an arbitrary state of polarization into a circularly polarized signal, after which the antenna emits an electromagnetic wave into outer space. A lens corrector based on a full-aperture dielectric lens provides the formation of a narrow radiation pattern and increase the gain, minimizing the dimensions of the antenna. The waveguide matched load (11) is installed on the second unused input of the polarizer (providing circular left-hand polarization) to prevent the occurrence of a reflected signal that can cause interference in the transmission channel. The impedance of the waveguide load is matched to minimize signal reflection in the load. A horn antenna with a lens corrector provides a gain of 23 dBi at a given frequency of 26.8 GHz.

Thus, the radio transmitting complex provides a high level of EIRP equal to 50 dBm or 20 dBW, with a channel data rate of 80 Mbps, limited by the performance of the quadrature modulator.

The tight mechanical combination of all the cases of the subsystems of the radio transmitting complex provides small dimensions (up to 113 × 102 × 88 mm) and a mass (up to 1 kg) of the invention. In this case, the horn antenna (always open to the outer surface of the spacecraft) plays an important role as a radiator for heat removal.

Claims (12)

1. A compact high-speed radio transmitting complex of a spacecraft, comprising: a quadrature modulator and encoder housed in the housings, a polarizer structurally coupled to the horn antenna, a radio frequency unit in the housing of which a highly stable carrier frequency oscillator is installed, which increases the converter-adder, a bandpass filter, and a solid-state power amplifier, the quadrature modulator and encoder cases are fixed at the edges of the side surface of the radio-frequency unit case, a polarizer, structurally combined with a horn antenna and with a coordinated load, is mounted on the housing of the radio frequency block between the quadrature modulator and the encoder and connected to the output of the boost-amplification circuit of the radio frequency block by means of a waveguide, while the horn antenna is made with a lens corrector, and the polarizer is made with two inputs for the formation of left-side and right-side circular polarization, while at one of the inputs a matched load is installed, which is a section of the waveguide 2. The radio transmitting complex according to claim 1, characterized in that the power amplifier is made in the form of a semiconductor integrated circuit of the microwave range based on pseudomorphic transistors with high electron mobility. 3. The radio transmitting complex according to claim 1, characterized in that the lens corrector is made on the basis of a full-aperture dielectric lens, which provides the formation of a narrow radiation pattern. 4. The radio transmitting complex according to claim 1, characterized in that the horn antenna is made open to the outer surface of the spacecraft. 5. The radio transmitting complex according to claim 1, characterized in that the horn antenna is made pointedly. 6. The radio transmission complex according to claim 1, characterized in that it is configured to use the DVB-S2 digital broadcast standard. 7. The radio transmitting complex according to claim 1, characterized in that the encoder is based on a programmable logic integrated circuit. 8. The radio transmitting complex according to claim 1, characterized in that it is configured to work in the centimeter Ka-band.

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