Microwave sources are used for many applications with widely differing requirements on their noise and stability.
Many of them are low-cost microwave generators where a quartz crystal provides the frequency for voltage-controlled oscillators (VCO). But the crystal is quite susceptible to environmental fluctuations, so environmental parameters have to be carefully controlled. However, for high-accuracy applications, such as highly sensitive radar, stable, low-noise microwave sources are required and their requirements often cannot be met with such standard VCOs. For these applications, other approaches are necessary to provide a more stable frequency signal. Some cutting-edge research setups utilize optical frequency combs as ultra-stable microwave sources. But while such systems fulfill the accuracy requirements for high-end applications, they are very complex and expensive and primarily not suitable for industrial applications.
Cycle uses an innovative approach to overcome these drawbacks: Like the frequency comb approach, an optical system is used as an internal clock to drive the RF signal.
However, in contrast to a frequency comb, Cycle’s approach is based on a low-noise mode-locked laser as the core of the optical oscillator. A Balanced Optical Cross-Correlator (BOC) is used for referencing the laser signal to a delayed version of the same signal. By comparing the signal to itself, the noise of the optical oscillator can be corrected for providing a stabilized optical clock for low noise microwave generation.
Since the BOC offers down to 10 fs RMS timing jitter and timing drift, the resulting microwave sources offer high accuracy suitable for industrial applications such as radar systems.