DETECTION AND LOCKING TO THE ABSORPTION SPECTRA OF GASSES IN THE MILLIMETER-WAVE REGION

• US 20140368377A1
• Filed: 06/12/2013
• Published: 12/18/2014
• Est. Priority Date: 06/12/2013
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: NADEAU, Phillip Michel, HAROUN, Baher S., TROMBLEY, Django, RAMASWAMY, Srinath Mathur
• Granted Patent: US 9,325,334 B2
• Time in Patent Office: Days
• US Class Current: 342/192
• CPC Class Codes: H03L 7/26 using energy levels of molecules, atoms, or subatomic particles as a frequency reference

Abstract

A frequency reference device that includes a frequency reference generation unit to generate a frequency reference signal based on an absorption line of a gas.

Claims

1. A frequency reference device, comprising:

a frequency reference generation unit to generate a frequency reference signal based on an absorption line of a gas.

2. The device of claim 1, wherein the frequency reference generation unit comprises a vacuum sealed gas absorption cell containing the gas.

3. The device of claim 2, wherein the frequency reference generation unit comprises a radio frequency (RF) transmitter to transmit a RF signal into the gas absorption cell and a RF receiver to receive the RF signal after the RF signal exits the gas absorption cell.

4. The device of claim 3, wherein the frequency reference generation unit comprises an integrated circuit (IC) chip that contains both a RF transmitter antenna and a RF receiver antenna.

5. The device of claim 3, wherein the frequency reference generation unit comprises a signal generation and detection unit coupled to the RF transmitter and the RF receiver to generate the RF signal and to analyze the received RF signal.

6. The device of claim 5, wherein the frequency reference generation unit comprises an IC chip that contains the RF transmitter, the RF receiver and the signal generation and detection unit.

7. The device of claim 5, wherein the frequency reference generation unit comprises an IC chip that contains the RF transmitter antenna, the RF receiver antenna, the RF transmitter, the RF receiver, and the signal generation and detection unit.

8. The device of claim 1, wherein the reference frequency signal corresponds to the center frequency of the absorption line.

9. The device of claim 1, wherein the absorption line is a 183.31 GHz absorption line of water vapor.

10. A method of generating a reference frequency, comprising:

receiving a radio frequency (RF) signal transmitted through a gas absorption cell containing a gas;

detecting an absorption line of the gas with the RF signal; and

generating a reference frequency based on the frequency of the absorption line.

11. The method of claim 10, further comprising measuring a spectrum of the gas.

12. The method of claim 11, further comprising removing a background spectrum from the spectrum of the gas.

13. The method of claim 10, further comprising tracking the absorption line.

14. The method of claim 10, further comprising generating an error signal used to track the absorption line.

15. A system for generating a reference frequency signal, comprising:

a gas absorption cell containing a gas; and

a signal generation and detection unit to;

generate a radio frequency (RF) signal;

detect an absorption line of the gas;

lock-in on the absorption line; and

output a reference frequency signal based on the absorption line.

16. The system of claim 15, wherein the signal generation and detection unit uses a frequency-shift keying modulation scheme to detect and lock-in on the absorption line.

17. The system of claim 15, further comprising an error signal generator to adjust the frequency of the RF signal.

18. The system of claim 15, further comprising a RF transmitter coupled to the signal generation and detection unit to transmit the RF signal into the gas absorption cell.

19. The system of claim 15, further comprising a RF receiver coupled to the signal generation and detection unit to receive the RF signal after passing through the gas absorption cell.

20. The system of claim 15, wherein the absorption line is a water vapor absorption line at 183.31 GHz.

21. The system of claim 15, wherein the gas in the gas absorption cell is at a pressure of less than 1 mbar.

22. The system of claim 15, wherein the gas absorption cell is vacuum sealed and includes RF access windows.

23. The system of claim 15, further comprising a calibration unit to remove a background spectrum from the measured absorption line of the gas.

24. The system of claim 15, wherein the gas absorption cell comprises a metal.

25. The system of claim 15, wherein the gas absorption cell comprises a high dielectric constant waveguide material.

26. The system of claim 15, wherein the signal generation and detection unit is fabricated on an integrated circuit (IC) chip and the IC chip is operably coupled to the gas absorption cell.