Addressing the need for more data in space missions

Article By : Maurizio Di Paolo Emilio

Satellite systems should be able to interface effectively and quickly with antenna arrays. It is therefore essential to consider different circuit optimization techniques to ensure high performance.

The aerospace market continues to be an advanced technological area. Even simple connectors, SoC, and various ICs are used on a series of mission-critical satellites.

Teledyne is situated in Grenoble; it deals with the manufacturing of components in aerospace and defense mainly. Grenoble is ranked 5th most inventive city in the world, according to Forbes magazine. Teledyne started in 1995 with TS8388 and TS83101, with various improvements thanks to EV12AD550, EV12DD700. The latter is a DAC that works in all bands, L, S, C, X, Ku, and Ka. Target applications are based on space systems: SAR radar imaging, high-throughput satellites, military, precision lab instruments, and microwave telecom systems. Each segment has a different situation in terms of packaging and qualification.

The devices are created with the smallest form factor and offer on-the-fly software reconfiguration of the entire RF system for beamforming; better radar imagery with rich multi-band sensing.

Starting with the world’s first GHz-class data converter 24 years ago, and followed by further world firsts since, Teledyne has grown and keeps working to deliver further historical landmarks in data conversion technology such as:

  • First Ka-band capable data converters, supporting ever-increasing higher signal and RF bandwidths
  • First controlled synchronization of multiple data converters in antenna arrays
  • ESIstream: An open source serial interface protocol, enabling controlled synchronization and other benefits
  • Enabling array antennas with digital interface instead of RF on coaxial cables

Teledyne offers more frequency support with various bands and simultaneous operation in multiple bands. Now, Teledyne is working on more digitalization of the RF domain in the Ka band, enabling simplification and simultaneous operation in multiples bands (Figure 1).

Figure 1 Overview of Teledyne e2v portfolio

The artificial satellite operators have an insatiable thirst for data and are therefore specifying satellite design with ever-higher sensor capacities. This leads to an excess of information that creates a growing need to perform signal processing on board. The Interstellar project will aim to improve ADC/DAC performance for aerospace & defense applications.

Interstellar H2020 project
Interstellar aims to develop new high-speed ADC and DAC solutions, with the guarantee of achieving greater integration with more channels on a single card, lower power consumption, higher bandwidth, and improved dynamic performance. The goal of the Interstellar project is to build the next generation of high-speed data converters to strengthen space competitiveness.

One of the goals of the project is to understand the health conditions of the Earth, using radar to map the terrain and for tsunami alerts. Interstellar H2020 must guarantee the simplification of the RF signal chain and the direct conversion to the Ka-band.

Within the project, two new data converters are developed and matured in a qualified phase (Technology Readiness Level TRL6): ADC EV12AQ600 and DAC EV12DD700. These devices facilitate innovative solutions for Rx to Tx signal chains for satellite telecommunications, Earth observation, navigation, and scientific missions.

EV12AQ600 is highly skilled and customizable, suitable for ultra-wideband microwave backhaul systems, data acquisition systems, and test and measurement applications (Figure 2).

Figure 2 Block diagram of ADC EV12AQ600

EV12AQ600 is the first 12-bit GHz class ADC to have a cross point switch (CPS), which allows the device to operate its four cores simultaneously, independently or in pairs, and to assign the sampling rate of 6.4 Gsps to the desired number of channels. This flexibility allows system designers to develop advanced systems in the field and, for the first time, to design with a quad-channel ADC converter for space applications, using the radiation tolerance version. In addition to the multi-channel CPS functionality, the DAC has the proven chain synchronization function to meet the growing trend of increasing the number of channels in MIMO (for phased-arrays) and multiple-input, and other multiple-output systems.

EV12AQ600 is used in a Fraunhofer multi-ADC synchronization evaluation board. This board has implemented this ADC, allowing test of the advanced synchronization capability. The board uses an FPGA module from Trenz Electronic (TE0809-04) based on Xilinx Zynq UltraScale (Figure 3).

Figure 3 Fraunhofer multi-ADC synchronization evaluation board

Radiation in space
The charged particles and Gamma rays create ionisation that can alter the parameters of the device. These changes are estimated in terms of total ionising dose parameter (TID). The absorbed ionising dose is commonly measured in rad: the absorbed energy of 100 ergs per gram of material. The duration of satellite missions can last for years so that a large TID value can be accumulated.

The manufacturing process of ICs has undergone changes in the last decade with new components that have increased sensitivity to radiation when exposed to low doses. This effect is called enhanced low-dose-rate sensitivity (ELDRS.) The TID dose rate for the ground test is generally ~ 50 rad/s. This dose entails performing an initial qualification test in an 8-hour shift.

The rad-hard design determines the design requirements of an electronic component from scratch to withstand the effects of radiation. It can be one of the most expensive and time-consuming approaches, but it is sometimes the only solution for electronic components, and it is essential to protect human lives or safeguard important orbital missions in space.

High-speed digital ICs are interesting in this area because the trapped charge can shift the threshold voltage of the MOS transistor, a key parameter that is directly correlated to the consumption and speed of the circuit. As a result, the supply of the current can increase, and the timing margins can be degraded. In the worst case, the functionality may cease due to the high leakage current.

[Continue reading on EDN US: Synchronization chaining]

Maurizio Di Paolo Emilio is a Ph.D. in Physics and a telecommunication engineer.

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