CPT Cesium-Cell Atomic Clock Operation With a 12-mW Frequency Synthesizer ASIC

Abstract

Abstract-In this paper, we present the design, fabrication, and electrical characterization of a low-power microwave source for interrogation of cesium atomic hyperfine transition frequency using the coherent population trapping (CPT) technique. The 4.6-GHz frequency generation and signal buffering is performed by a single-chip frequency synthesizer ASIC with a frequency tuning resolution of 1 × 10 −13 and a programmable RF output power from −10 to 0 dBm. The circuit was used to modulate the current of a vertical-cavity surface-emitting laser through a dedicated impedance matching network and low thermal conductivity transmission line. Strong modulation sidebands with >60% of carrier amplitude were obtained with an ASIC power consumption of 12 mW. The system was used as optical source for atomic interrogation in an experimental cesium CPT clock. The measured clock stability of 5 × 10 −11 at τ = 1 s, going down to 4.5 × 10 −12 at τ = 200 s, is limited by the signal-to-noise ratio of the detected CPT signal.

Chip-scale atomic devices

“…When locked to an atomic physics package, this oscillator supported a short-term frequency stability of 4 Â 10 À10 =ͱs. An even lower power of 12 mW was achieved in another ASIC, 188 which also incorporated high-resolution frequency tuning of 10…”

A high-overtone bulk acoustic wave resonator-oscillator-based 4.596 GHz frequency source: Application to a coherent population trapping Cs vapor cell atomic clock

“…The phase noise of the 4.596 GHz signal is measured at the level of −105 dBrad 2 /Hz for an offset frequency f = 1 kHz. Compared to the 4.596 GHz synthesizer ASIC developed in 11 , phase noise performances of the present HBARbased source are 26 dB and 67 dB better for f = 1 kHz and f = 100 kHz respectively. Compared to the 100-MHz OCXO-based synthesizer, phase noise performances of the HBAR-based source are found to be 25 dB worse for f = 1 kHz and 5 dB better for f = 1 MHz respectively.…”

“…Figure 7 shows the absolute phase noise of the HBAR-based oscillator 2.298 GHz signal and the output 4.596 GHz signal respectively. For comparison, these phase noise performances are compared to those of a lowpower consumption (12 mW) 4.596 GHz frequency synthesizer ASIC developed in 11 for MAC applications, and to those of a low power 4.596 GHz frequency synthesizer developed in 5 . Also, phase noise performances of a state-of-the-art 100 MHz oven-controlled quartz-crystal oscillator (Pascall OCXOF-E-100) ideally reported to 4.596 GHz are given 24 .…”

“…In Ref. 11 , a 12-mW single-chip 4.596 GHz frequency synthesizer ASIC implemented in a 130-nm RF CMOS process was developed for a Cs MAC, demonstrating a clock stability of 5 × 10 −11 at 1 s, limited by the signal-to-noise ratio of the detected CPT signal. However, in such systems, the frequency multiplication degrades the phase noise and can consume up to 50 % of the MAC total power budget 5 .…”

Underwater Acoustic Modem With High Precision Ranging Capability Based on Second-Level Cesium Atomic Clock

“…Therefore, the modems mentioned in (Domrese et al 2014) exhibit poor performance to the poor environment. The atomic clock is a high-precision and stable timing device, using the electrons inside the atom to control the movement of the clock (Zhao et al 2015). More and more underwater platforms are equipped with atomic clocks for high precision timing.…”