RU194575U1 - On-board high-speed radio transmitter for low-orbit small spacecraft CubeSat format - Google Patents

Abstract

The utility model relates to on-board high-speed space radio transmitters of the X-band, designed to transmit a large amount of data with speeds above 1 Mb / s and can be used as part of small spacecraft of the CubeSat format for various purposes. The onboard high-speed radio transmitter for low-orbit small spacecraft in the CubeSat format consists of structurally separated digital and analog modules. The modules are mechanically connected to the radiator body, which mechanically interfaces with the design of a small spacecraft in the CubeSat format. The radiator case contains a base and a cover for the analog module. Electrical interfacing with the on-board equipment is implemented on the basis of the OrbiCraft-Pro platform with the UniCAN information bus by electrical connection of the digital and analog modules through the connector, while the digital module incorporates a chip system and DACs that control the operation of the analog module. The proposed design extends the functionality of a radio transmitter designed for low-orbit small spacecraft of the CubeSat format, in particular, it is possible to change the frequency range of the transmission and change the parameters of the output signal. 5 ill.

Description

The utility model relates to space technology, namely to onboard space high-speed radio transmitters, and can be used as part of small spacecraft of the CubeSat format for various purposes. More specifically, the utility model relates to on-board high-speed space radio transmitters of the X-band, designed to transmit a large amount of data with speeds of more than 1 Mb / s.

Cubesat is the dimensional standard for micro and nanosatellites of the Earth, proposed in 1999 in the USA. A feature of Cubesat is its fixed dimensions, which change multiple times, i.e. Cubesat 1U (unit) is a 10x10 x 10 cm cube, 2U is two cubes in a single satellite 10x10 x 20 cm in size, 3U is 10 x 10 x 30 cm. So far, the reached limit is 6U or 10 x 20 x 30 cm.

In the present description, the concepts of "satellite" and "spacecraft" are used as synonyms.

The use of such small spacecraft around the world is growing every year with the growth of the range of tasks they solve. Under Cubesat standards, many structural elements, batteries, boards, sensors, communication systems have been developed.

Obviously, the use of the transmitter on a Cubesat nanosatellite has a number of features that do not allow the use of well-known solutions, namely:

- restrictions on weight and size characteristics;

- energy restrictions;

- restrictions on ensuring the thermal regime.

Another problem when choosing a transceiver is the limited frequency spectrum. The entire spectrum of frequencies is clearly divided between different services and in order to use a certain frequency band special permission is required from state bodies controlling this area.

It is known from the prior art that the STX microsatellites use an S-band transmitter designed for CubeSat missions, which was part of the UKube-1 mission, the first spacecraft of the British National Space Agency.

Known S-band transmitter ISIS TXS compatible with the CubeSat standard, operating at S-band frequencies. The transmitter supports BPSK or GMSK modulation schemes and provides data rates of up to 100 kbit / s with low power consumption.

Known transmitter NanoCom AX100, characterized by a modular design and allows you to configure incoming and outgoing frequencies. A miniature form factor allows the use of a transceiver for various space missions.

The considered transceivers operate in different frequency ranges, but you can see that they have common characteristics that allow them to perform various missions as part of the on-board radio complex of small spacecraft. This is necessarily a small form factor, low power consumption and sufficient output power of the order of 30 dBm, for communication with a low Earth orbit.

A significant drawback of such transmitters is the impossibility of widespread use of the frequency range. For such changes, it is necessary to completely modify the hardware. Use other components, which of course is impossible, in outer space.

In this regard, the implementation of a radio transmitter based on SDR technologies opens up new opportunities. SDR (Software-defined radio) - software-defined (also called: “software-defined”) is a transceiver in which some or all of the functions of the physical layer are software-defined. Developments related to SDR allow you to adapt one hardware base to several types of data transfer at once, which can be added directly during operation, which allows you to exclude many auxiliary components from the process, such as filters, amplifiers, etc. At the same time, the user receives a multifunctional hardware solution with a large set of operating modes, as well as frequency ranges, and you can switch between them in automatic and dynamic mode, as well as through remote access.

Known onboard high-speed radio transmitter Tethers unlimited SWIFT-XTS, which is a unit of on-board equipment, made in a single package, having peripheral interfaces RS-422 and LVDS, operating frequencies in the range of 7000-8500 MHz and designed for operation in space flight conditions. The well-known high-speed radio transmitter Tethers unlimited SWIFT-XTS is characterized by a modular structure and the use of SDR technologies, however, it incorporates an S-band receiver, which increases energy consumption. The Tethers unlimited SWIFT-XTS onboard high-speed radio transmitter does not have an external CAN interface and does not comply with the PC / 104 standard, which does not allow for electrical interfacing with on-board equipment based on the OrbiCraft-Pro platform with the UniCAN information bus.

As the closest analogue, the Clyde space CPUT X-Band Transmitter, an onboard equipment made in the form of a printed circuit board with a housing element for the high-frequency part, having operating frequencies in the range of 8025-8450 MHz and intended for operation in space conditions, was adopted flight. The well-known high-speed radio transmitter Clyde space CPUT X-Band Transmitter is characterized by a monoblock structure and the use of SDR technologies.

The Clyde space CPUT X-Band Transmitter has no external CAN interface. CAN (Controller Area Network) is an industrial network standard, focused primarily on combining various actuators and sensors into a single network. The absence of an external CAN interface does not allow:

- provide electrical interfacing with on-board equipment based on the OrbiCraft-Pro platform with the UniCAN information bus;

- provide modular replacement of the high-frequency part to change the frequency range of data transmission.

 The objective of this utility model is to create an on-board high-speed X-band radio transmitter compatible with on-board equipment based on the OrbiCraft-Pro platform with UniCAN information bus.

The OrbiCraft-Pro satellite kit is a design kit of electronic and mechanical parts for manual assembly

small satellite in CubeSat format. The device assembled by means of OrbiCraft-Pro can function both as a laboratory prototype for educational purposes, and in space in Earth orbits as a CubeSat satellite for scientific purposes.

The solution of this problem ensured the achievement of a technical result consisting in the possibility of changing the frequency range of the transmission by replacing the high-frequency module due to the implementation of the modular principle, the ability to change the parameters of the output signal through the use of software-defined radio technology and compatibility with the OrbiCraft-Pro platform, which greatly expands the functionality of the radio transmitter intended for low-orbit small spacecraft of the CubeSat format.

To achieve the specified technical result in the implementation of the block diagram of the device, the direct conversion approach (or the formation at zero intermediate frequency) was used. This method is more modern, more demanding on components, but gives the output circuit with fewer nodes, with less power consumption and more compact. The narrow-band filter in it is replaced by a band-pass filter, the requirements for which are much lower.

The achievement of the technical result ensured that in the onboard high-speed radio transmitter for low-orbit small spacecraft of the CubeSat format, consisting of structurally separated digital and analog modules mechanically connected by a radiator body, which is mechanically coupled to the design of a small spacecraft of the CubeSat format and containing a base and a cover for analog module, new is electrical interfacing with on-board equipment based on the OrbiCraft-Pro platform with information the UniCAN bus through the electrical connection of the digital and analog modules through the connector, while the digital module incorporates a chip system and DACs that control the operation of the analog module.

The utility model is illustrated by the following illustrative materials:

in FIG. 1 shows a General view of the claimed onboard high-speed radio transmitter for low-orbit small spacecraft format CubeSat;

in FIG. 2 shows an exploded view of a transmitter without a cover;

in FIG. 3 is a schematic illustration of a radio transmitter;

in FIG. 4 shows schematically the structure of the device;

in FIG. 5 is a block diagram of a transmitter.

The onboard high-speed radio transmitter for low-orbit small spacecraft in the CubeSat format is two separate modules: 1 - digital and 2 - analog. Digital 1 and analog 2 modules are mechanically connected by a radiator body, which is mechanically coupled to the design of a small spacecraft in the CubeSat format. The housing includes a common base 3 and cover 4 for analog module 2.

The electrical connection of the digital module 1 and analog module 2 occurs through connector 5. The peripheral devices are connected to the on-board radio transmitter through connector 6 of the PC / 104 standard, taking into account its location and the location of the mounting holes. Electrical interfacing with on-board equipment is implemented on the basis of the OrbiCraft-Pro platform with the UniCAN information bus.

Digital module 1 incorporates a system on a chip (SoC) 7, which provides processing of incoming commands and information and control digital-to-analog converters (DAC) 8, which control the operation of analog module 2.

The digital module 1 also contains memory modules designed to buffer “useful” data until it is transmitted to the ground control center (MCC).

The analog (high-frequency) module 2 is designed to generate a signal at the carrier frequency and amplify the high-frequency output signal to the required level.

Base 3 acts as a power structural element, and also provides the necessary thermal interface to maintain a comfortable temperature regime of the device during operation.

Cover 4 serves to shield the high-frequency radiation of analog module 2.

Using the direct conversion method provides in the claimed utility model:

- a wide range of proposed types of modulations by the main space radio standards for this range (CCSDS, DVB-S, DVB-S2);

- A wide range of proposed coding schemes by these standards;

- the ability to use various options for modulations and coding schemes, and to expand due to this the possibility of the device, minimally changing the hardware, for reasons of economic efficiency and utility for the consumer.

So, the implementation of the radio transmitter in the form of a modular structure allows, if necessary, to replace the high-frequency module 2, for example, with S band.

When using the SDR concept, the device’s block diagram provides a DAC (digital-to-analog converter), the output of which is connected to the analog part of the device, and some digital computing device providing a digital input for the DAC (based on FPGAs, microprocessors, microcontrollers, or digital signal processors). As a result, the device diagram shown in FIG. 5.

The high-speed X-band transmitter for CubeSat-format satellites provides a transmission speed of 0.5 to 10 Mbit / s and the performance of the MCA in the frequency range of 8-12 GHz, provides industry standard coding and modulation methods, which expands its application.

The onboard high-speed radio transmitter for low-orbit small spacecraft of the CubeSat format transmits beacon signals, receives control commands, and transfers telemetric information and data received from the payload. The beacon signal is transmitted by the Morse code in the frequency range 8-12 GHz.

For the device to work, it is necessary to connect the onboard high-speed radio transmitter to the information bus and the power bus of the OrbiCraft Pro platform through the PC / 104 connector (pos. 6, Fig. 3), which will transmit power and control commands, and also connect to the high-frequency connector (pos. 9, Fig. 4) an antenna-feeder device for transmitting a high-frequency signal to a ground station and a source of transmitted data is connected through a PN connector (pos. 10, Fig. 3). The source of the transmitted data can be any peripheral device that supports the Ethernet data interface, for example, a camera.

The onboard high-speed radio transmitter is controlled (change of modes) by UniCAN protocol via the CAN interface via the onboard bus. Control can be carried out either automatically, by an onboard computer or other control unit, or by transmitting commands from the Earth through a command radio link. Receipts for admission are sent to the teams.

In the first phase, information intended for transmission through the Ethernet interface is placed in the internal memory of the device; the analog part of the device (pos. 2, Fig. 3) is inactive in this case in order to reduce power consumption.

In the second phase, when flying over a ground station, the device goes into transmission mode. The frequency synthesizer, modulator, power amplifier are activated. The frequency synthesizer generates the carrier frequency, the modulator modulates it with a useful complex signal generated as a result of the software-defined radio path, the amplifier raises the power to the required. The generated signal through a high-frequency cable enters the antenna, from where it is emitted in the direction of the Earth.

After the end of the transfer, the device turns off; in this phase, the heat accumulated during the heat transfer session is gradually dissipated.

Claims (1)

On-board high-speed radio transmitter for low-orbit small spacecraft of the CubeSat format, consisting of structurally separated digital and analog modules mechanically connected by a radiator body that is mechanically coupled to the design of a small spacecraft of the CubeSat format and containing a base and a cover for the analog module, characterized in that the electric interfacing with the on-board equipment is implemented on the basis of the OrbiCraft-Pro platform with the UniCAN information bus via electrical Connections of digital and analog modules via the connector, the digital module has in its composition and system-on-chip DAC that govern the operation of the analog module.

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