Molecular clock

Patent metadata

Field	Value
Publication number	US-10739728-B2
Application number	US-201816233982-A
Country	US
Kind code	B2
Filing date	Dec 27, 2018
Priority date	Jan 29, 2018
Publication date	Aug 11, 2020
Grant date	Aug 11, 2020

Abstract

A molecular clock which utilizes a rotational spectrum of gaseous molecules in a sub-THz region for clock stabilization is described. The molecular clock has a fast start-up characteristic and is also robust against mechanical vibration or variation of electromagnetic field. Also described is a chip-scale implementation of a molecular clock. In an embodiment, a molecular clock chipset only consumes a DC power of 66 mW. While providing a highly stable, compact and energy efficient time generator of portable devices.

First claim

What is claimed is:

1. A molecular clock comprising:
a waveguide gas cell having a radio frequency (RF) input port, an RF output port and a gas inlet/outlet, the waveguide gas cell being sealed so as to be capable of holding gaseous molecules having a linear structure, the waveguide gas cell configured to receive the gaseous molecules having a linear structure via the gas inlet/outlet; and
the waveguide gas cell having a rectangular cross-section and a meander profile along a central longitudinal axis thereof.

2. The molecular clock of claim 1 wherein the gaseous molecules having a linear structure are provided as a carbonyl sulfide compound (OCS).

3. The molecular clock of claim 2 wherein the gaseous molecules having a linear structure are provided as the carbonyl sulfide compound (OCS) having a rotational spectrum in the frequency range of about 12 GHz to about 1 THz.

4. The molecular clock of claim 2 wherein the gaseous molecules having a linear structure are provided as the carbonyl sulfide compound (OCS) having a rotational spectrum in the range of about 200 GHz to about 300 GHz.

5. The molecular clock of claim 2 wherein gaseous molecules having a linear structure are provided as 16 O 12 C 32 S.

6. The molecular clock of claim 1 further comprising:
a transmitter having an RF output port coupled to the RF input port of the waveguide gas cell;
a receiver having an RF input port and an RF output port with the RF input port coupled to the RF output port of the waveguide gas cell; and
a feedback circuit having an input coupled to the output port of the receiver and having an output coupled to an input port of the transmitter, the feedback circuit configured to generate a feedback signal in response to a frequency of a signal output by the transmitter and a frequency of rotational-state transitions of the gaseous molecules.

7. The molecular clock of claim 6 wherein the transmitter further comprises:
a voltage-controlled oscillator (VCO) having an input coupled to the output of said feedback circuit and having an output coupled to an input of said transmitter circuit.

8. The molecular clock of claim 7 wherein:
the VCO is provided as a voltage-controlled crystal oscillator (VCXO); and
the feedback circuit provides a feedback signal to the VCXO.

9. The molecular clock of claim 6 wherein the receiver further comprises:
a detector capable of detecting an RF signal provided from the output of the waveguide gas cell and providing a differential output;
a low noise amplifier (LNA) having a differential RF input coupled to the differential output of the detector and having a differential RF output; and
a lock in detector having an input configured to receive a differential RF output from the LNA and having an output coupled to the receiver RF output port and at which an error signal is provided.

10. A molecular clock comprising:
a waveguide gas cell having a radio frequency (RF) input port, an RF output port and a gas inlet/outlet, the waveguide gas cell capable of holding gaseous molecules having a linear structure, the waveguide gas cell having a rectangular cross-section and a meander profile along a central longitudinal axis, the waveguide gas cell configured to be sealed to hold the gaseous molecules;
an integrated circuit comprising:
a substrate;
an RF transmitter circuit disposed on said substrate, the RF transmitter circuit having an input and having an RF output port;
a first chip-to-waveguide transition coupled between the RF output port of the transmitter and the RF input port of the waveguide gas cell;
an RF receiver circuit disposed on the substrate, the RF receiver circuit having an RF input port and an RF output port, the RF output port coupled to the input of a feedback circuit, the RF receiver circuit configured to receive a signal corresponding to rotational-state transitions of the gaseous molecules; and
a second chip-to-waveguide transition coupled between the RF output port of the waveguide gas cell and the RF input port of the receiver, the first and second transitions comprising a quartz probe; and

the feedback circuit having an input coupled to the RF output port of the receiver and having an output coupled to the output of the RF transmitter, the feedback circuit configured to generate a feedback signal in response to a frequency of a signal output by the transmitter and the signal corresponding to rotational-state transitions of the gaseous molecules.

11. The integrated circuit of claim 10 wherein the waveguide gas cell is capable of holding a carbonyl sulfide compound (OCS) having a rotational spectrum of linear polar molecules in one of:
a millimeter frequency range; and
a sub-terahertz (THz) frequency range.

12. The molecular clock of claim 11 wherein the waveguide gas cell is capable of holding 16 O 12 C 32 S having a rotational spectrum in the range of about 12 GHz to about 1 THz.

13. The molecular clock of claim 10 wherein the integrated circuit is provided as a CMOS integrated circuit.

14. The integrated circuit of claim 10 wherein the RF transmitter comprises a voltage-controlled oscillator (VCO) having an input coupled to the output of said feedback circuit and having an output coupled to the input of the waveguide gas cell via the first chip-to-waveguide transition.

15. The integrated circuit of claim 14 wherein:
the VCO is provided as a differential voltage-controlled crystal oscillator (VCXO); and
the feedback circuit provides a differential feedback signal to the differential VCXO.

16. A molecular clock comprising:
a waveguide gas cell having a radio frequency (RF) input port, an RF output port and a gas inlet/outlet, the waveguide gas cell configured to receive gaseous molecules having a linear structure via the gas inlet/outlet;
the waveguide gas cell having a rectangular cross-section and a meander profile along a central longitudinal axis, the waveguide gas cell configured to be sealed to hold the gaseous molecules;
a transmitter coupled to the RF input port of the waveguide gas cell via a probe; and
a receiver coupled to RF output port of the waveguide gas cell via a probe, the receiver configured to receive a signal corresponding to rotational-state transitions of the gaseous molecules.

17. The molecular clock of claim 16 further comprising:
a feedback circuit having an input coupled to the output port of the receiver and having an output coupled to an input port of the transmitter, the feedback circuit configured to generate a feedback signal in response to a frequency of a signal output by the transmitter and the signal corresponding to rotational-state transitions of the gaseous molecules.

18. The molecular clock of claim 17 wherein the waveguide gas cell is capable of holding a carbonyl sulfide compound (OCS) having a rotational spectrum of linear polar molecules in one of:
a millimeter frequency range; and
a sub-terahertz (THz) frequency range.

19. The molecular clock of claim 16 further comprising a vacuum pump coupled to the gas inlet/outlet configured to draw the gaseous molecules into and out of the waveguide gas cell.

Assignees

• Massachusetts Inst Technology

Inventors

• Han Ruonan
• Wang Cheng

Classifications

• H03L7/1976 Primary

  using a phase accumulator for controlling the counter or frequency divider · CPC title

• H03J7/00

  Automatic frequency control; Automatic scanning over a band of frequencies · CPC title

• H04B1/1027

  assessing signal quality or detecting noise/interference for the received signal · CPC title

• G04F5/14

  using atomic clocks · CPC title

• H03L7/0992

  comprising a counter or a frequency divider · CPC title