Figure 1 SSB noise versus frequency offset for 8 GHz SLCO.
Saetta Labs is shipping their new SL1 series sapphire loaded cavity oscillators (SLCO), the next generation ultra-low phase noise microwave oscillator technology. These sapphire oscillators outperform all other microwave oscillators in terms of phase noise. Models are available at 7.00 GHz, 8.00 GHz, 10.00 GHz and 10.24 GHz. The SL1-8.00 GHz oscillator exhibits a phase noise of -154 dBc/Hz at 10 kHz and -170 dBc/Hz at 100 kHz. Figure 1 shows the phase noise performance of the SL1-8.00 oscillator.
INTEGRATED TECHNOLOGY
Saetta Labs’ sapphire oscillators are a single, fundamental mode, pure microwave oscillator that replaces three or four traditional oscillators and their integrated hardware while achieving an order of magnitude higher performance. Prior to the sapphire oscillator, the best microwave reference was created by multiplying a high frequency quartz OCXO, cleaning up with a SAW filter or oscillator then phase locking a dielectric resonator oscillator (DRO). This combined performance is the limit of what is achievable with traditional technology. Saetta’s sapphire oscillator replaces all three oscillators while significantly outperforming them.
The SL1 series oscillators have all the internal circuitry necessary to phase lock (discipline) to a 10 MHz reference. Without a 10 MHz reference, the SLCO is frequency stabilized to an internal reference, is voltage tunable and can be externally phase locked. Electronic tuning is ±1 ppm for a 0 to 1 V tune voltage and output power is 12 dBm.
SAPPHIRE OSCILLATOR TECHNOLOGY
Sapphire oscillators are a completely different breed of microwave oscillator, relying on a whispering gallery mode instead of an electromechanical (quartz/SAW) or TE/TM mode (DRO) approach. The whispering gallery in sapphire is a dielectric resonant mode more common in optical systems. The resonance is maintained within the sapphire by near-perfect internal reflection between the dielectric boundary between the sapphire and a vacuum. The metal walls do not contain the fields, eliminating the loss of the metal wall boundary in traditional TE or TM mode resonators. Saetta’s sapphire resonator technology has loaded Qs in excess of 100,000, which enables the lowest phase noise oscillators available and operate fundamentally at X-Band.
Saetta’s technology extends into the amplifier and bias. Biasing their amplifiers through their proprietary ultra-low-noise architecture reduces the 1/f noise that contributes to the phase noise of the oscillator. All low noise circuitry is double- or triple-regulated.
Thermal stabilization is where Saetta has made the sapphire oscillator commercially possible. Using a proprietary ultra-high-resolution thermoelectric temperature control, they have stabilized the sapphire oscillator for room and extended temperature use (0°C to +40°C), holding to within ±100 ppb, typical, without the need for an external reference. When using an external reference, the oscillator stability matches that of the reference through phase locking.
ADVANCED RADAR SYSTEMS
The phase noise of the oscillator in any radar system sets the fundamental limits achievable in terms of range and resolution, regardless of how good the hardware is after the oscillator. Recent releases of digital-to-analog converters (DACs) and analog-to-digital converters can now drive array elements directly and achieve a 10logN reduction in noise with a converter on each N-element. The latest converter technology is achieving extremely low phase noise floors and 1/f, pushing the limits of achievable phase noise and significantly outperforming traditional oscillator technology.
Take a 10 GHz X-Band radar as an example. Flight targets may range from approximately subsonic to hypersonic or, for simplicity’s sake, 1x to 5x the speed of sound. At sea level, this is a Doppler shift of 20 to 100 kHz. A multiplied crystal has a flat phase noise response in this range at approximately -135 dBc/Hz for a top-tier system. Compare that to the SL1-10.00 GHz sapphire oscillator with a phase noise of -150 dBc/Hz at 10 kHz and -170 dBc/Hz at 100 kHz. For the past two decades, quartz-based oscillators have only improved the phase noise by 5 to 10 dB. Sapphire oscillators from Saetta Labs improve upon the current state-of-the-art by 15 to 35 dB while eliminating reference design time with multiple loops.
QUANTUM COMPUTING
Figure 2 Saetta Labs X-Band SLCO.
Synthesizer design for quantum computing has evolved from using traditional synthesizers to modulating each qubit directly with a microwave DAC to manipulate phase, frequency and amplitude. The new DACs have lower phase noise than even the best traditional quartz/SAW-based systems. The sapphire oscillator has significantly lower noise and can improve the phase noise of the qubit DAC drivers.
THE NEXT GENERATION
Saetta Labs was founded to bring the next generation phase noise levels of sapphire oscillators to real-world applications in a compact module. Their oscillators vary in size based on frequency. A 10 GHz oscillator is 102 (W) × 147 (L) × 76 mm (H). With a broad array of uses, from laboratory standards to deployable radar systems, our sapphire oscillators are available to extend the state-of-the-art in low phase noise systems. All Saetta Labs SLCOs are manufactured and tested in Boulder, Colo., using U.S. suppliers. Figure 2 shows an example of the highly integrated SLCO X-Band oscillator.
Saetta Labs
Boulder, Colo.
saettalabs.com