Microchip Introduces Advanced Low-Noise Chip-Scale Atomic Clock for Defense Systems

Microchip has announced its latest low-noise, chip-scale atomic clock (CSAC) solution. Featuring improvements such as a profile height of less than ½ inch and power consumption of less than 295 mW, the new solution targets aerospace and defense applications like mobile radar, autonomous sensor networks, and unmanned vehicles.

The new CSAC solution is built for low SWaP VPX designs, mobile radar, dismounted radios, dismounted IED jamming systems, autonomous sensor networks, and unmanned vehicles. Image (modified) used courtesy of Microchip

A Rugged Chip-Scale Atomic Clock

Microchip’s new LN-CSAC SA65-LN combines the benefits of a crystal oscillator and an atomic clock into a single package. It integrates the company’s third-generation evacuated miniature crystal oscillator (EMXO) with atomic clock stability to achieve high spectral purity and precision in a compact form factor. 

Microchip designed the LN-CSAC to deliver a 10-MHz sine wave output with a signal amplitude between 6 dBm and 9 dBm into a 50 Ω load. It also supports external synchronization through a 1 PPS input that allows phase and frequency calibration to within 1 nanosecond and 1 femtosecond, respectively. Meanwhile, a programmable 1 PPS output provides a configurable pulse width between 10 µs and 500 ms. The unit also offers digital tuning with a ±1 x 10-6 range and 1 x 10 resolution.

Microchip’s new LN-CSAC. Image used courtesy of Microchip

To ensure performance in harsh environments, the LN-CSAC withstands operating temperatures from -40°C to +80°C (option -002) and non-operating temperatures from -55°C to +105°C. It complies with MIL-STD-810G vibration specifications and MIL-STD-202 shock resistance of 30 g. The device also exhibits minimal sensitivity to environmental variations, with a total frequency deviation of ±3 x 10-10 over its operating temperature range and ±4 x 10-10 due to supply voltage fluctuations. It also maintains long-term accuracy with a monthly frequency drift below 9 x 10-10 and a yearly drift under 1 x 10-8.

With a phase noise of -120 dBc/Hz at 10 Hz and Allan deviation below 3 x 10-11 at 1s, the LN-CSAC provides exceptional signal stability.  

Designing With Atomic Clocks

An atomic clock is an extremely precise timekeeping device that uses the resonant frequency of atoms as a reference to maintain stability and accuracy far beyond traditional quartz oscillators. Unlike mechanical or crystal-based clocks, which rely on macroscopic vibrations, atomic clocks exploit the quantum energy transitions of atoms, typically cesium-133 or rubidium-87, to define time intervals with extreme precision.

Working principles of a cesium atomic clock. Image used courtesy of Britannica

Atomic clocks operate by exposing a cloud of atoms to microwave radiation and adjusting the frequency until it matches the atoms' natural resonance. This resonance corresponds to a fixed energy transition. By locking the microwave oscillator to this transition, the clock achieves unparalleled stability. A feedback loop continuously refines the oscillator frequency to counteract drift. Modern chip-scale atomic clocks (CSACs) miniaturize this process by integrating laser-based optical pumping and evacuated miniature crystal oscillators to maintain a stable frequency in a compact package.

For electrical engineers, atomic clocks offer advantages in applications where precise timing and frequency stability are needed. In RF and communications systems, they synchronize network nodes. In autonomous systems, such as UAVs or sensor networks, they provide a stable time reference when GPS signals are unavailable. High-speed test and measurement systems use atomic clocks to ensure phase-coherent signal generation and accurate time-domain analysis.

Clocked for Military, Defense, and Space

By combining the benefits of an atomic clock with a crystal oscillator, Microchip believes its solution will provide significant value in the military, defense, and space applications. The LN-CSAC SA65 is now available for purchase in production quantities.