System and method for in-situ optimization of microwave field homogeneity in an atomic clock

Patent metadata

Field	Value
Publication number	US-10218368-B2
Application number	US-201615186152-A
Country	US
Kind code	B2
Filing date	Jun 17, 2016
Priority date	Feb 18, 2016
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

A method of operating a cold atom clock to maintain a highly homogeneous microwave field is provided. The method includes: driving a subset of microwave feed lines to excite a microwave field in a resonator, while a power and a phase of at least one microwave feed line in the subset is held constant, and while the power or the phase of at least one other microwave feed line in the subset is changed; measuring a strength of the atomic transition excited by the microwave field; extracting a relative power and a relative phase between or among the subset of microwave feed lines by processing the strength of the atomic transitions excited by the microwave field measured in at least one auxiliary-measurement sequence; and determining if an adjustment to one or more of the microwave feed lines is needed to improve the homogeneity of the microwave field phase and amplitude.

First claim

What is claimed is:

1. A method of operating a cold atom clock to maintain a highly homogeneous microwave field, the method comprising:
driving a subset of microwave feed lines to excite a microwave field in a resonator, while a power and a phase of at least one microwave feed line in the subset is held constant, and while the power or the phase of at least one other microwave feed line in the subset is changed;
measuring a strength of the atomic transition excited by the microwave field in the resonator while driving the subset of the microwave feed lines;
extracting a relative power and a relative phase between or among the subset of microwave feed lines by processing the strength of the atomic transitions excited by the microwave field measured in at least one auxiliary-measurement cycle; and
determining if an adjustment to one or more of the microwave feed lines in the subset of microwave feed lines is needed to improve the homogeneity of the microwave field phase and amplitude based on the extracting.

2. The method of claim 1 , further comprising:
obtaining N clock measurements responsive to measuring the strength of the atomic transition excited by the microwave field in the resonator while driving the subset of the microwave feed lines, wherein N is a positive integer.

3. The method of claim 1 , further comprising:
adjusting the power and/or phase of the one or more of the microwave feed lines in the subset of the microwave feed lines if an adjustment is determined to be needed.

4. The method of claim 1 , wherein driving the subset of the microwave feed lines while the power and the phase of at least one microwave feed line in the subset is held constant, and while the power or the phase of the at least one other microwave feed line in the subset is changed comprises:
driving the subset of the microwave feed lines to excite the microwave field in the resonator, while the power or the phase of the at least one other microwave feed line in the subset is at a first offset value of an auxiliary-measurement sequence; and
driving the subset of the microwave feed lines to excite the microwave field in the resonator, while the power or the phase of the at least one other microwave feed line in the subset is at a second offset value of the auxiliary-measurement sequence.

5. The method of claim 4 , wherein measuring the strength of the atomic transition excited by the microwave field in the resonator while driving the subset of the microwave feed line comprises:
measuring the strength of the atomic transition excited by the microwave field in the resonator while the power or the phase of the at least one other microwave feed line in the subset is at the first offset value of the auxiliary-measurement sequence to obtain a first measurement of the auxiliary-measurement sequence; and
measuring the strength of the atomic transition excited by the microwave field in the resonator while the power or the phase of the at least one other microwave feed line in the subset is at the second offset value of the auxiliary-measurement sequence to obtain a second measurement of the auxiliary-measurement sequence.

6. The method of claim 5 , further comprising:
obtaining N clock measurements responsive to obtaining the first measurement of the auxiliary-measurement sequence, wherein N is a positive integer; and
obtaining N clock measurements responsive to obtaining the second measurement of the auxiliary-measurement sequence.

7. The method of claim 1 , further comprising:
selecting another subset of the microwave feed lines.

8. The method of claim 1 , wherein driving the subset of the microwave feed lines, while the power and the phase of at least one microwave feed line in the subset is held constant, and while the power or the phase of at least one other microwave feed line in the subset is changed; and measuring the strength of the atomic transition excited by the microwave field in the resonator while driving the subset of the microwave feed lines comprises;
driving a first subset of the microwave feed lines, while the power or the phase of the at least one other microwave feed line in the first subset is at a first offset value of an auxiliary-measurement sequence;
measuring the strength of the atomic transition excited by the microwave field in the resonator while the power or the phase of the at least one other microwave feed line in the first subset is at the first offset value of the auxiliary-measurement sequence to obtain a first measurement of the auxiliary-measurement sequence for the first subset, the method further comprising:
obtaining N clock measurements responsive to obtaining the first measurement of the auxiliary-measurement sequence, wherein N is a positive integer,
wherein the driving the subset of the microwave feed lines, while the power and the phase of at least one microwave feed line in the subset is held constant, and while the power or the phase of at least one other microwave feed line in the subset is changed; and measuring the strength of the atomic transition excited by the microwave field in the resonator while driving the subset of the microwave feed lines further comprises:
driving the first subset of the microwave feed lines, while the power or the phase of the at least one other microwave feed line in the first subset is at a second offset value of the auxiliary-measurement sequence; and
measuring the strength of the atomic transition excited by the microwave field in the resonator while the power or the phase of the at least one other microwave feed line in the first subset is at the second offset value of the auxiliary-measurement sequence to obtain a second measurement of the auxiliary-measurement sequence for the first subset.

9. The method of claim 8 , further comprising:
obtaining N clock measurements responsive to obtaining the second measurement of the auxiliary-measurement sequence for the first subset.

10. The method of claim 9 , further comprising:
determining if all measurements for the auxiliary-measurement sequence for the first subset of the microwave feed lines have been collected, wherein extracting the relative power and the relative phase between or among the subset of microwave feed lines by processing the strength of the atomic transitions excited by the microwave field measured for the auxiliary-measurement sequence comprises:
extracting the relative power and the relative phase between or among the first subset of microwave feed lines by processing the strength of the atomic transitions excited by the microwave field measured for all measurements for the auxiliary-measurement sequence for the first subset responsive to determining all the measurements for the auxiliary-measurement sequence for the first subset of the microwave feed lines have been collected.

11. The method of claim 10 , wherein determining if the adjustment to the one or more of the microwave feed lines in the subset of microwave feed lines is needed to improve the homogeneity of the microwave field phase and amplitude comprises:
determining if an adjustment to the one or more of the microwave feed lines in the first subset of microwave feed lines is needed to improve the homogeneity of the microwave field phase and amplitude, the method further comprising:
adjusting the one or more of the microwave feed lines in the first subset of the microwave feed lines if an adjustment is determined to be needed.

12. A system to operate an accurate cold atom clock, the system comprising:
the cold atom clock comprising:
a plurality of microwave feed lines; and
a respective plurality of phase-and-amplitude-adjust modules associated with the plurality of

Assignees

• Honeywell Int Inc

Inventors

• Fertig Chad
• Salit Kenneth

Classifications

• H03L5/02

  of power · CPC title

• H03L7/26 Primary

  using energy levels of molecules, atoms, or subatomic particles as a frequency reference · CPC title

• G04F5/145 Primary

  using Coherent Population Trapping · CPC title