MILITARY, AEROSPACE & DEFENCE INDUSTRY FOCUS
• Shock and vibration resilience: Ruggedised MEMS oscillators have far lower sensitivity to vibration, typically around 1E-11/g maximum, a level not achieved in commercially available quartz oscillators. These MEMS oscillators can survive shocks of 30,000g and beyond, with simple construction and reliability: this level of shock survivability is a big challenge even for customised, purpose-built quartz oscillators. This makes MEMS ruggedised oscillators well- suited for military systems deployed in extreme conditions. Unlike quartz oscillators, MEMS oscillators are not reliant on the size of the crystal, which allows them to be more compact and more resistant to vibration and shock. MEMS oscillators also offer greater reliability, with a meantime between failure (MTBF) of over two billion hours. This is a significant improvement over quartz oscillators.
• Holdover performance: MEMS oscillators, such as the SiT7111, deliver superior holdover performance with a repeatable typical time error of ±1 microsecond over a 24-hour period, ensuring that systems remain accurate even in GPS-denied environments, and a superior performance compared to quartz OCXO.
• Easier design integration: Low SWaP MEMS oscillators with low sensitivity to board level temperature swings, vibrations and power supply noise, and without the need for external voltage regulators, simplify layout and thermal management. This makes them easier to design into systems that require robust precision timing. MEMS oscillators are designed with I2C or SPI frequency tuning options, allowing for greater flexibility in their application.
MEMS PRECISION TIMING IMPROVES OPEN ARCHITECTURE SYSTEM PERFORMANCE The characteristics of MEMS-based precision timing devices make it ideal for a wide range of defence applications, including: • GPS disciplined oscillators (GPSDO): Ruggedised MEMS TCXOs, with superior repeatable frequency stability without
Backplane configuration
frequency jumps, enable fast, robust and reliable signal decoding, including encrypted signals with long integration time, continuous signal lock under rough conditions, fast signal reacquisition time when signal is lost and improved resistance to jamming and other interferences.
• Assured positioning, navigation, and timing (A-PNT): In environments where GPS signals are denied or degraded, the local oscillator becomes the timing reference and needs to maintain accuracy from minutes to hours to days – a condition referred to as holdover. The device of choice will have to have a limited drift from the time the GPS synchronisation is lost, over time and under changing environmental conditions. New ultra-stable SiT7111 MEMS oscillators can replace expensive and fragile chip-scale atomic clocks
(CSACs) in A-PNT modules in a smaller form factor with extended reliability. • Software-defined radio: For software-defined radios, which require high levels of phase noise and frequency stability, new MEMS Super-TCXOs, such as SiT7201 and SiT7202, offer the necessary performance in a SWaP-C package and simplify quartz TCXO-based circuitry or eliminate the need for an OCXO. In addition, their phase noise is virtually insensitive to vibrations, ensure continuity of performance and signal even through the roughest environments.
• Radial clock and switch cards: Radial clock cards and switch cards are critical in distributing timing signals across various modules to ensure that all parts of a system operate in sync, whether through Precision Time Protocol (PTP) such as IEEE1588 or Synchronous Ethernet (SyncE). The performance of these cards directly affects the reliability and effectiveness of the overall system. The latest MEMS oscillators, with their superior environmental resistance and overall stability, are well-suited to meet the demands in synchronisation of these critical system functions.
BEST-IN-CLASS MEMS PRECISION TIMING
Ruggedised MEMS oscillators are well-suited to meet the stringent demands of modern military systems, providing reliable and precise timing solutions in open architectures like MOSA, SOSA, CMOSS, and OpenVPX. Their superior resistance to environmental stressors, combined with low SWaP and commercial availability, makes them the right choice for a wide range of applications. MEMS technology represents a critical
advancement in ensuring the reliability, scalability and effectiveness of defence systems.
SiTime
www.sitime.com
FEBRUARY 2025 DESIGN SOLUTIONS 51
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