What type of crystal oscillators can be used in the three applications LEO, MEO and GEO?

  • 30 May, 2024
  • by Roland Teoh

For satellite applications in LEO (Low Earth Orbit), MEO (Medium Earth Orbit), and GEO (Geostationary Earth Orbit), the selection of crystal oscillators is crucial due to the harsh space environment and the specific requirements of each orbit. The type of crystal oscillators and their main specifications will vary based on factors like required stability, phase noise, power consumption, and resistance to radiation and extreme temperatures. Here’s a breakdown:

Common Types of Crystal Oscillators for Satellite Applications:

1. Temperature-Compensated Crystal Oscillator (TCXO): Offers improved temperature stability over a wide range of temperatures, which is crucial for the varying conditions of space.

2. Voltage-Controlled Crystal Oscillator (VCXO): Provides frequency tuning capability which can be essential for precise frequency adjustment and control in satellite communication systems.

3. Oven-Controlled Crystal Oscillator (OCXO): Offers the highest stability against temperature variations by maintaining the crystal at a constant temperature, beneficial for all orbits, especially in the variable conditions of LEO and MEO.

4. Rubidium Oscillators: While not crystal-based, Rubidium oscillators provide extremely high accuracy and stability, suitable for the precise timing required in navigation and communication satellites across LEO, MEO, and GEO.

Main Specifications:

• Frequency Stability: This is critical due to the temperature extremes and other environmental factors in space. Oscillators with high frequency stability ensure reliable communication and operation.

• Phase Noise: Low phase noise is essential for communication satellites to maintain signal clarity and integrity, especially in LEO and MEO where the density of satellites can cause more signal interference.

• Size and Power Consumption: Especially important for LEO satellites, where size and weight are more constrained due to the larger number of satellites in the constellation. Lower power consumption is also crucial to conserve energy.

• Temperature Range: The oscillator should function across a broad temperature range, given the extreme temperature variations in space.

• Radiation Hardness: Components must withstand the intense radiation found in space, especially in MEO and GEO, where the Earth’s magnetic field provides less protection against charged particles.

• Aging: The oscillator should have minimal frequency change over time, ensuring long-term reliability and reducing the need for recalibration.

Choosing the right oscillator involves balancing these specifications with the mission requirements. For instance, OCXOs might be favored in GEO applications for their superior temperature stability, while LEO satellites might prioritize TCXOs or VCXOs for their lower power consumption and compact size, considering the vast number of satellites needed for global coverage. Rubidium oscillators, despite their higher cost and power requirements, might be chosen for critical navigation or communication missions requiring exceptional frequency stability and accuracy.

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