The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 24, 1978
Filed:
Nov. 14, 1977
Fred Lexes Walls, Boulder, CO (US);
The United States of America as represented by the Secretary of Commerce, Washington, DC (US);
Abstract
A system and method is disclosed for achieving frequency stabilization. A tunable element, such as a cavity structure, is stabilized through the use of multiple modulation to stabilize both the resonant frequency of the cavity structure and the probe signal coupled to an atomic, molecular or other reference resonance line. Said reference resonance line can be internal or external to the cavity structure. A local oscillator provides a carrier signal, which typically can be at a frequency of 5 MHz, with the carrier signal being phase or frequency modulated by multiple modulating signals, such as, for example, by modulating signals with frequencies of 12.2 KHz and 0.4 Hz, and the multiple modulated carrier signal then processed and the resulting probe signal coupled to the cavity structure substantially at a preselected frequency, which frequency can be approximately 1420 MHz for a hydrogen frequency standard useful for atomic clocks. The output signal coupled from the cavity structure is amplitude modulated with the modulation at the fundamental and odd harmonics of the first modulation frequency having a level proportional to any frequency offset between the probe signal and the atomic, molecular or other reference resonance line, and the modulation at the fundamental and odd harmonics of the second modulation frequency having a level proportional to any frequency offset between the cavity frequency and the frequency of the probe signal. The output signal from the cavity is processed and ultimately rectified so that various amplitude modulations on the output signal can be recovered. The error signal resulting from synchronous detection of the amplitude modulation signal of the second frequency, 12.2 KHz in this example, or odd harmonics thereof, is coupled to the tuning element of the cavity tuning control circuitry to precisely tune the resonant frequency of the cavity to the frequency of the probe signal and the error signal resulting from synchronous detection of the amplitude modulation signal of first frequency, 0.4 Hz in this example, or odd harmonics thereof, is coupled to the local oscillator to adjust the frequency so that the probe signal is maintained at the center of the resonance of the atomic, molecular or other reference resonance and to thereby stabilize the resonant frequency of the cavity and the output frequency of the device over a long term.