REVIEW OF SCIENTIFIC INSTRUMENTS 86, 096108 (2015)

 Directly measuring the direct digital synthesizer frequency chirp-rate
for an atom interferometer

Juan-Juan Tao, Min-Kang Zhou,a) Qiao-Zhen Zhang, Jia-Feng Cui, Xiao-Chun Duan,
Cheng-Gang Shao, and Zhong-Kun Hua)

MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong
University of Science and Technology, 1037 Luo Yu Road, Wuhan 430074, People’s Republic of China
(Received 14 May 2015; accepted 28 August 2015; published online 23 September 2015)

During gravity measurements with Raman type atom interferometry, the frequency of the laser used
to drive Raman transition is scanned by chirping the frequency of a direct digital synthesizer (DDS),
and the local gravity is determined by precisely measuring the chip rate α of DDS. We present an
effective method that can directly evaluate the frequency chirp rate stability of our DDS. By mixing
a pair of synchronous linear sweeping signals, the chirp rate fluctuation is precisely measured with a
frequency counter. The measurement result shows that the relative α instability can reach 5.7 × 10−11
in 1 s, which is neglectable in a 10−9 g level atom interferometry gravimeter. C 2015 AIP Publishing
LLC. [http://dx.doi.org/10.1063/1.4930562]