Precision Timing at the Heart of Defense Open Architecture Systems

|by |

Timing plays a central role in ensuring that electronic systems operate reliably and harmoniously. This is never more critical than in the battlefield. Electronic systems such as unmanned vehicles, ground sensors, command centers and tactical communications must work in coordination. When multiple platforms are deployed in joint operations-for functions such as real-time drone video, jamming enemy signals or data communication -they must be synchronized. This ensures data transmission is cohesive for reliable and timely decision making and action.

If various subsystems are provided by different manufacturers and introduced at different times are not synchronized, it complicates defense operations. As the industry moves toward open architecture implementations, timing misalignments can lead to latency issues, degraded performance or, in the worst cases, system failure. This article discusses how precision timing helps ensure interoperability with precisely synchronized data transmission.

The Open-System Future of Defense

Open architectures, such as those outlined in Modular Open Systems Approach (MOSA), Sensor Open Systems Architecture (SOSA), C4ISR/EW Modular Open Suite of Standards (CMOSS) and OpenVPX, are revolutionizing the design, integration and maintenance of defense systems. These standards emphasize modularity, flexibility and scalability, allowing military platforms to quickly integrate new technologies and achieve cost-effective updates.

Reduces logistics tails by enabling common sparing. Eliminates the need for end-of-life buys for 30+ years sustainment by enabling hardware modernization every 5-10 years. (Source: UA Army DEVCOM C5ISR Center)

For systems built on modular open standards, the system requirements for communications, command and control, electronic warfare, intelligence gathering and others, dictate the timing device requirements. Key considerations include:

• Size, weight, power and cost (SWaP-C) reduction:
  Military platforms, particularly mobile and airborne systems, require compact, lightweight and energy-efficient components. Design engineers also prefer readily available, off-the-shelf components with reasonable lead time and continuity of supply.
  
• Shock, vibration and temperature resilience:
  Reliable and stable frequency is essential to maintain optimal performance. Even minor variations can severely degrade system accuracy and functionality. Military systems must withstand harsh environments. These include changing and extreme temperatures, high vibration levels and severe shock conditions. Timing components must be robust and reliable.
  
• Holdover performance:
  GPS is the source of reference timing in over 700 DoD weapon systems. Unfortunately, GPS is vulnerable to attacks. Maintaining accurate timing even when a GPS signal is unavailable or untrustworthy is critical for successful military operations.

Precision timing devices are distributed throughout electronic systems and must perform in a wide variety of contexts to ensure that all subsystems remain synchronized. The ability to maintain functional and accurate time in complex and high-stakes defense environments can make the difference between mission success and failure.

Why MEMS Timing Is the Right Choice for Defense Applications

Micro-electro-mechanical systems (MEMS) silicon timing technology is a means for solving some critical defense challenges. Ruggedized Precision MEMS-base oscillators such as temperature-compensated oscillators (TCXOs) and oven-controlled oscillators (OCXOs) provide significant advantages over quartz-based products. These improvements include:

• SWaP reduction:
  COTS Ruggedized MEMS oscillators are proven low SWaP solutions. For instance, the SiT5543 in a 7 mm x 5 mm package consumes only 135 mW, making it an ideal choice for platforms where SWaP constraints are a significant concern. This device can replace a quartz OCXO that would consume almost 4X the energy at 500 mW in a footprint 10X to 20X larger.
  
• Frequency stability over temperature:
  MEMS timing technology is advancing, continuing to provide a range of options to replace quartz TCXOs and OCXOs. SiT5348 MEMS Super-TCXO is rated at +50 ppb over a wider temperature range of up to -40 to 105°C with repeatable and predictable frequency with no frequency dip or activity jump. New SiT5543 TCXO rated at +5 ppb over -40 to 95°C is the only TCXO that achieves this temperature stability with lower power, smaller size and higher reliability than a quartz OCXO. The new SiT7111 oven-controlled MEMS oscillator delivers + 1 ppb over -40 to 95°C, a wider temperature range than most quartz OCXOs.
  
• Shock and vibration resilience:
  Ruggedized 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 reliably: this level of shock survivability is a big challenge even for customized, purpose-built quartz oscillators. This makes MEMS ruggedized 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 offer greater reliability, with a meantime between failure (MTBF) of over 2 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 defense applications, including:

• GPS disciplined oscillators (GPSDO):
  Ruggedized MEMS TCXOs with superior repeatable frequency stability without frequency jumps enables 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 synchronization is lost, over time and under changing environmental conditions. New ultra-stable SiT7111 MEMS oscillator 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 synchronization of these critical system functions.

Timing distribution in open architecture.

Advanced Technology and Stringent Demands Require Best-in-Class MEMS Precision Timing

Ruggedized 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 defense systems.

Tags

• Aerospace-Defense