Abstract: One embodiment of the invention includes an alkali beam cell system that comprises a reversible alkali beam cell. The reversible alkali beam cell includes a first chamber configured as a reservoir chamber that is configured to evaporate an alkali metal during a first time period and as a detection chamber that is configured to collect the evaporated alkali metal during a second time period. The reversible alkali beam cell also includes a second chamber configured as the detection chamber during the first time period and as the reservoir chamber during the second time period. The reversible alkali beam cell further includes an aperture interconnecting the first and second chambers and through which the alkali metal is allowed to diffuse.

Abstract: Provided is a chip-scale atomic clock having a folded optic configuration or physics package. In particular, the physics package includes a vapor cell for containing gaseous alkali atoms and a VCSEL for generating a laser light One or more heating elements are positioned to simultaneously heat both the vapor cell and VCSEL to the required operating temperature. A micro-lens element, positioned between the VCSEL and a reflector, is used to first expand the beam of light, and then to subsequently collimate the light after it is once reflected. Collimated, reflected light passes through the vapor cell wherein the alkali atoms are excited and a percentage of the reflected light is absorbed. A detector, located opposite the reflector and micro-lens array, detects light passing through the cell. An error signal is generated and the output voltage of a local voltage oscillator is successively stabilized.

Abstract: This invention concerns the realization of a Coherent-Population-Trapping (CPT) atomic frequency standard using a laser which has feedback from an external cavity. The mode spacing of the external cavity is adjusted to equal the hyperfine transition frequency of the atomic vapor or a sub-harmonic of it. The external cavity enhances the modulation response at the required atomic transition and improves the stability of the frequency standard.

Abstract: An atomic clock at optical frequency based on atomic beam and a method for generating the atomic clock comprises: The atomic beam (8) is ejected from a pile mouth after heating an atomic pile (1) in a vacuum chamber (2); A laser (4) corresponding to frequency of a clock transition transfers the atomic beam (8) from a ground state of the clock transition to an excited state of the clock transition in a adiabatic passing mode; After interaction with the laser corresponding to the frequency of a clock transition, the atomic beam (8) passes a signal detection region with a detection laser (5), and after the interaction with the detection laser (5), each of the atoms gives off a photon of spontaneous emission; An emitted fluorescence photon signal from atoms which is excited by the detection laser (5) is explored; A clock laser (4) for exploring transition frequency of an atomic clock is modulated.

Abstract: A chip scale atomic clock is disclosed that provides a low power atomic time/frequency reference that employs direct RF-interrogation on an end-state transition.

Abstract: Method for modulating an atomic clock signal and a corresponding atomic clock. The laser beams (L1, L2) are pulse-modulated in amplitude to illuminate (A) an interactive medium. A detection (B) of the current pulse (Sr) and of the pulses (Sr?1 to Sr?p) preceding said current impulsion is performed. The pulses are superimposed (C) by linear combination to generate a compensated atomic clock signal (SHC) whereof the spectral width is minimized. The invention is applicable to atomic clocks with pulsed interrogation whereof the interactive medium consists of thermal or laser-cooled atoms.

Abstract: A chip scale atomic clock is disclosed that provides a low power atomic time/frequency reference that employs direct RF-interrogation on an end-state transition.

Abstract: The present invention relates to a method and system in which multi-coherent resonances of a microwave in which the alkali-metal atoms in the ground state are driven simultaneously by a microwave hyperfine frequency ?H and a Zeeman frequency ?Z. The driving influences on the atom can include magnetic fields or by optically pumping light modulated by a Zeeman frequency ?Z or a microwave hyperfine frequency ?H or by combinations of their harmonics or subharmonics. Multi-coherent resonances permit simultaneous measurement or control of the ambient magnetic field and measurement or control of a hyperfine resonance frequency of alkali-metal atoms. In one embodiment, the hyperfine frequency for a controlled magnetic field can serve as an atomic clock frequency.

Abstract: A cell suitable for use with an atomic clock and a method for making the same, the cell including: a silicon wafer having a recess formed therein; at least one amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon sealing the recess; and, an alkali metal containing component and buffer gas contained in the recess. The method includes: providing a silicon wafer; forming a cavity through the silicon wafer; introducing an alkali metal containing component and buffer gas into the cavity; and, anodically bonding at least one amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon to the wafer to close the cavity.

Abstract: A cell suitable for use with an atomic clock and a method for making the same, the cell including: a silicon wafer having a recess formed therein; at least one amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon sealing the recess; and, an alkali metal containing component and buffer gas contained in the recess. The method includes: providing a silicon wafer; forming a cavity through the silicon wafer; introducing an alkali metal containing component and buffer gas into the cavity; and, anodically bonding at least one amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon to the wafer to close the cavity.

Abstract: A spin oscillator device generates a microwave output in response to an applied DC current. The device includes a spin momentum transfer (SMT) stack including a top electrode, a free layer, a nonmagnetic layer, a pinned magnetic structure, and a bottom electrode. A local magnetic field source adjacent the SMT stack applies a local magnetic field to the free layer to cause the magnetization direction of the free layer to be oriented at a tilt angle with respect to plane of the free layer. The local magnetic field source can include coils or an electromagnet structure, or permanent magnets in close proximity to the SMT stack.

Abstract: An optically-excited atomic frequency standard that subjects alkali metal atoms (111) to circularly-polarized optical radiation. The atomic frequency standard is improved by the use of a circular polarizer (202) to control the intensity of the circularly-polarized optical radiation. The circular polarizer includes a linear polarizer (203) and a quarter-wave retarder (205), with the light to be circularly polarized passing first through the linear polarizer (203) and then through the quarter-wave retarder (205). In the atomic frequency standard, the optical radiation (105) to which the circular polarizer (202) is applied is itself linearly polarized, and the intensity of the circularly polarized light produced by the circular polarizer (202) is controlled by rotating (303) the circular polarizer. The degree of rotation determines how much of the linearly-polarized optical radiation passes through the linear polarizer, and thus how much circularly-polarized light is produced.

Abstract: An apparatus and method for measuring CPT is disclosed. The apparatus includes a quantum absorber that is irradiated by radiation from an electromagnetic radiation source. The quantum absorber includes a material that exhibits CPT. The electromagnetic radiation source generates electromagnetic radiation having first and second CPT-generating frequency components. The first CPT-generating frequency component has a frequency ?L??, and a first CPT component amplitude. The second CPT generating frequency component has a frequency ?L+? and a second CPT component amplitude. The apparatus also includes a detector for generating a detector signal related to the power of electromagnetic radiation that leaves the quantum absorber. The detector signal exhibits an asymmetry as a function of frequency ? in a frequency range about a frequency ?0. The apparatus includes an asymmetry servo loop that alters one of ?L, the first CPT component amplitude, and the second CPT component amplitude to reduce the asymmetry.

Abstract: The present invention provides a method and apparatus for making atomic clocks or atomic magnetometers as self-modulated laser systems based on the physics of push-pull optical pumping. An atomic vapor cell is required to be in the laser cavity. With proper conditions, spontaneous push-pull optical pumping can occur inside the laser cavity. This causes the laser beam to be modulated at hyperfine-resonance frequency. With a fast photodetector, the modulated laser signal can be converted into the electrical signal, which serves as the atomic clock ticking signal or magnetometer signal. The self-modulated laser system does not use any local oscillator and the microwave circuit to lock the oscillator frequency to the hyperfine-resonance frequency, and therefore can consume less power and become more compact than conventional systems. This invention will benefit applications of time measurements and magnetic-field measurements.

Abstract: An apparatus in one example comprises a die structure that comprises a middle layer, a first outside layer, and a second outside layer. The middle layer comprises a cavity that holds an alkali metal, and one of the first outside layer and the second outside layer comprises a channel that leads to the cavity. The middle layer, the first outside layer, and the second outside layer comprise dies from one or more wafer substrates.

Abstract: An apparatus for generating a stabilized frequency signal is disclosed. The apparatus includes a quantum absorber having first, second, and third energy states. The quantum absorber is irradiated by a first radiation source that generates electromagnetic radiation having a frequency, ?L, that induces transitions between the first and third energy states. The quantum absorber is also irradiated by a second radiation source that generates electromagnetic radiation having a frequency, ?M, that induces transitions between the first and second energy states. A detector that generates a detector signal indicative of the level of radiation leaving the quantum absorber in a frequency range including ?L is used by a number of servo loops. One of the servo loops determines the value of ?L that minimizes or maximizes the detector signal and a second servo loop determines an offset signal that reduces the dependence of ?M on the intensity of the first radiation source.

Abstract: The present invention relates to a static magnetic field applying structure for use in an atomic oscillator in which plural sets of magnetic field generating means are provided with spacing interposed among them, and a resonance cell is disposed in a space between the magnetic field generating means. The object of the present invention is to realize the static magnetic field applying structure which can be small-sized and produced at a low cost.

Abstract: The invention relates to a device (1) for producing a reference frequency signal (Se) from the response of an atomic resonator (R) to a pumping signal (Fat) transmitted thereto, comprising: a first oscillator for production of a first signal (S1) of frequency (F0) as a function of the response signal (E1) from the resonator (R); a second oscillator (13) for production of a second signal (S2) at a frequency (NF0) which is equal to a whole multiple of that of the first signal (S1). According to the invention, the second oscillator is selected to produce a second signal (S2) close in frequency to the frequency of resonance for the resonator (R).

Abstract: A method and apparatus that can generate two frequencies separated by the atomic hyperfine frequency separation needed to excite resonance in a Cs atom. In the present invention a coherent light source is frequency modulated with a modulation frequency having a sine wave to generate a lightwave. The lightwave comprises the two coherent optical fields having the frequency separation needed to excite resonance in the Cs atom. The modulation frequency can then be adjusted in order to fine-tune the frequency separation of the two coherent optical fields. The present invention also provides a method for localizing about 50% of the power in the lightwave at the two coherent optical fields by frequency modulating the light source with a square wave.

Abstract: The present invention relates generally to frequency standards. More specifically, the present invention relates to a method and apparatus for solid-state atomic frequency standard based on the hyperfine spectrum of paramagnetic dopants in solids.

Abstract: A CPT detector and a method for detecting CPT are disclosed. The CPT detector includes a quantum absorber, a polarization analyzer, and a detector. The quantum absorber includes a material having first and second low energy states coupled to a common high energy state. Transitions between the first low energy state and the common high energy state and between the second low energy state and the common high energy state are induced by electromagnetic radiation having a predetermined polarization state. The polarization analyzer blocks electromagnetic radiation of the predetermined polarization while passing electromagnetic radiation having a polarization state that is orthogonal to the predetermined polarization. The polarization analyzer is irradiated with a portion of the generated electromagnetic radiation that has passed through the quantum absorber. The detector generates a signal related to the intensity of electromagnetic radiation that leaves the polarization analyzer.

Abstract: A compact atomic oscillator with improved frequency stability. A voltage-controlled oscillator generates an oscillation signal based on a given control voltage, and a modulator modulates it with a low-frequency signal. A phase-locked loop (PLL) upconverts the modulated oscillation signal directly to a first frequency in atomic resonance frequency band. The first frequency is an integer multiple of the oscillation signal. A frequency synthesizer produces a second frequency specified by a frequency setting unit, and a mixer combines the first and second frequencies to produce an RF signal for driving an atomic resonator. The amount of discharge lamp light passing through the atomic resonator depends on the difference between RF signal frequency and atomic resonance frequency. This quantity is measured as a resonance detection signal, and a frequency controller applies it to synchronous detection to produce a control voltage for the voltage-control oscillator.

Abstract: A rubidium frequency standard control circuit which utilizes an initial sweep hand-off frequency locking process followed by a negative feedback loop for optimization of the stability of the voltage control oscillator employing the rubidium frequency standard.

Abstract: In an apparatus using optically excited atomic media, such as an atomic frequency standard, a source providing a controlled emission of light for exciting the D1 and/or D2 resonance lines of an alkali gas, such as rubidium or cesium, is controlled by an output generated by digital electronics from the light intensity signal of a light sensor for light transmitted by the alkali gas, an output for representing ambient temperature, and a light intensity-ambient temperature algorithm to substantially eliminate changes in light intensity due to light source aging for the purpose of reducing changes in temperature sensitivity of the apparatus as a function of time and the light-shift contribution to the frequency aging of the standard.

Abstract: The present invention relates to a method and system for using end resonances of highly spin-polarized alkali metal vapors for an atomic clock, magnetometer or other system. A left end resonance involves a transition from the quantum state of minimum spin angular momentum along the direction of the magnetic field. A right end resonance involves a transition from the quantum state of maximum spin angular momentum along the direction of the magnetic field. For each quantum state of extreme spin there are two end resonances, a microwave resonance and a Zeeman resonance. The microwave resonance is especially useful for atomic clocks, but it can also be used in magnetometers. The low frequency Zeeman resonance is useful for magnetometers.

Abstract: The present invention provides a method and system to simultaneously use the microwave and Zeeman end resonances associated with the same sublevel of maximum (or minimum) azimuthal quantum number m to lock both the atomic clock frequency and the magnetic field to definite values. This eliminates the concern about the field dependence of the end-resonance frequency. In an embodiment of the system of the present invention, alkali metal vapor is pumped with circularly-polarized D1 laser light that is intensity-modulated at appropriate resonance frequencies, thereby providing coherent population trapping (CPT) resonances. In another embodiment, pumping with constant-intensity circularly-polarized D1 laser light enhances magnetic resonances that are excited by alternating magnetic fields oscillating at appropriate resonance frequencies.

Abstract: A method is provided for optimizing the performance of laser-pumped atomic frequency references with respect to the laser detuning and other operating parameters. This method is based on the new understanding that the frequency references short-term instability is minimized when (a) the laser frequency is tuned nominally a few tens of MHz away from the center of the atomic absorption line, and (b) the external oscillator lock modulation frequency is set either far below or far above the inverse of the optical pumping time of the atoms.

Abstract: In an atomic oscillator of an optical pumping system, a slot line resonator, as a microwave resonator, is arranged in a portion where atoms are excited. The slot line resonator forms a microstrip line inputting microwaves so as to be orthogonal to a slot line with a dielectric substrate being sandwiched therebetween. A container in which the atoms are enclosed is mounted on the slot line resonator, and the slot line resonator and the container are covered with a metallic case having a pumping light passage hole and a photo element.

Abstract: A microwave frequency standard is provided which allows for miniaturization down to length scales of order one micron, comprising a modulated light field originating from a laser that illuminates a collection of quantum absorbers contained in a micro-machined cell. The frequency standard of the present invention can be based on all-optical excitation techniques such as coherent population trapping (CPT) and stimulated Raman scattering or on conventional microwave-excited designs. In a CPT-based embodiment, a photodetector detects a change in transmitted power through the cell and that is used to stabilize an external oscillator to correspond to the absorber's transition frequency by locking the laser modulation frequency to the transition frequency. In a stimulated Raman scattering (SRS) embodiment, a high-speed photodetector detects a laser field transmitted through the cell beating with a second field originating in the cell.

Abstract: An oscillator controller which optimizes key circuit parameters of an excitation circuit according to the operating condition of a discharge lamp. An excitation circuit energizes a discharge lamp to produce a light beam for pumping atoms, as part of a mechanism of atomic resonance detection. The operation of the excitation circuit is monitored by a start-up voltage monitor, which asserts a voltage monitoring signal when the excitation circuit's start-up voltage is reached. A light amount monitor receives a resonance detection signal from a light sensing device to check the amount of light before and after the discharge lamp lights up. The resultant light amount monitoring signal indicates this information. Based on the two monitoring signals, a bias voltage selector selects an appropriate bias voltage that varies circuit parameters of the excitation circuit.

Abstract: A rubidium frequency standard is compensated for frequency variations over temperature by allowing the rubidium frequency standard to vary while holding the output frequency constant. A voltage controlled crystal oscillator, locked to a physics package, provides the output signal. A temperature sensor senses temperature and proves a temperature signal to a microcontroller. A frequency synthesizer receives the output signal from the voltage controlled crystal oscillator as a reference and provides an RF signal to the physics package. The microcontroller looks up a frequency error in a memory in accordance with the temperature signal, generates an offset control word for the frequency synthesizer to compensate for the temperature and adjusts the VCXO with an error signal to compensate for temperature.

Abstract: An atomic frequency standard system includes two atomic standard devices, a comparison circuit and a correction circuit. The first device operates continuously, while the second device is operated only periodically. As the second device is only periodically operated, it experiences little frequency drift due to aging effects. When operated, the second device is stabilized, and then frequency compared to the first device by means of the comparison circuit. The correction circuit is then used to recalibrate frequency of the first device with the stabilized frequency of the second device.

Abstract: A rubidium atom oscillator is not influenced by a circumference noise or the like, and is excellent in the short-term stability and the phase noise characteristic. A crystal oscillator oscillates a fixed frequency as an atomic resonance frequency. A direct digital synthesizer inputs an output of the crystal oscillator as a system clock and also inputs tuned data corresponding to an error signal generated according to a resonance frequency so as to carry out a variable control of an output frequency. A frequency synthesizer synthesizes and multiplies an output of the direct digital synthesizer and applies a phase modulation with a low-frequency signal. An atomic resonator inputs an output of the frequency synthesizer and detects an error signal with respect to a resonance frequency of rubidium atoms. A tuned-data generating circuit inputs the error signal from the atomic resonator so as to generate the tuned data corresponding to the error signal.

Abstract: A method is provided for optimizing the performance of laser-pumped atomic frequency references with respect to the laser detuning and other operating parameters. This method is based on the new understanding that the frequency references short-term instability is minimized when (a) the laser frequency is tuned nominally a few tens of MHz away from the center of the atomic absorption line, and (b) the external oscillator lock modulation frequency is set either far below or far above the inverse of the optical pumping time of the atoms.

Abstract: A rubidium atom oscillator is not influenced by a circumference noise or the like, and is excellent in the short-term stability and the phase noise characteristic. A crystal oscillator oscillates a fixed frequency as an atomic resonance frequency. A direct digital synthesizer inputs an output of the crystal oscillator as a system clock and also inputs tuned data corresponding to an error signal generated according to a resonance frequency so as to carry out a variable control of an output frequency. A frequency synthesizer synthesizes and multiplies an output of the direct digital synthesizer and applies a phase modulation with a low-frequency signal. An atomic resonator inputs an output of the frequency synthesizer and detects an error signal with respect to a resonance frequency of rubidium atoms. A tuned-data generating circuit inputs the error signal from the atomic resonator so as to generate the tuned data corresponding to the error signal.

Abstract: An atomic clock of the type having a cell filled with an active vapor through which is projected a light beam. A detector of the projected light provides corresponding detector signals to a microprocessor. An rf frequency synthesizer provides a microwave signal to a microwave cavity adjacent the cell and also provides a clock standard output signal. The rf frequency synthesizer includes a fractional-N frequency synthesizer which compares signals from a voltage controlled crystal reference oscillator and a voltage controlled oscillator. The fractional-N frequency synthesizer is operable to provide an output control signal to precisely lock the voltage controlled oscillator microwave output signal with the voltage controlled crystal reference oscillator signal. The fractional-N frequency synthesizer also periodically causes a predetermined desired dither in the microwave signal.

Abstract: An atomic clock of the type having a cell filled with an active vapor through which is projected a light beam. A detector of the projected light provides corresponding detector signals to a microprocessor. An rf frequency synthesizer provides a microwave signal to a microwave cavity adjacent the cell and also provides a clock standard output signal. The rf frequency synthesizer includes a fractional-N frequency synthesizer which compares signals from a voltage controlled crystal reference oscillator and a voltage controlled oscillator. The fractional-N frequency synthesizer is operable to provide an output control signal to precisely lock the voltage controlled oscillator microwave output signal with the voltage controlled crystal reference oscillator signal. The fractional-N frequency synthesizer also periodically causes a predetermined desired dither in the microwave signal.

Abstract: A method for determining a resonant frequency of a mechanical device having a first mass and at least one second mass mechanically coupled to the first mass comprises the steps of: providing a control signal to a voltage-controlled oscillator (VCO) to control the frequency of an output thereof; translating a phase shifted output of the VCO into an oscillatory force which is applied to one of the first and second masses to cause the mechanical device to respond; measuring the response of the mechanical device and generating a response signal representative thereof in frequency and amplitude; generating an error signal proportional to the phase difference between a signal representative of the output of the VCO and the measured response signal; adjusting the control signal to cause the oscillatory force applied to the one mass to sweep within a calculated frequency range rendering the amplitude of the response signal to approach and exceed a calculated threshold value; and when the calculated threshold is excee

Abstract: A rubidium atom oscillator of a gas cell resonator type includes a cavity resonator having a gas cell in which rubidium gas is enclosed, and a dielectric material member that has thermal conductivity and closely contacts an inner wall of the cavity resonator parallel to an optical axis of an incident light emitted from a pumping source. The gas cell is inserted into the dielectric material member having the thermal conductivity along the optical axis.

Abstract: An improved magneto-optic trap is used to generate a high brightness low velocity continuous source of atoms as a continuous atomic beam. The improved magneto-optic atom trap is using gradient magnetic fields and a single circularly polarized laser beam incident upon a right angle conical mirror with apex aperture through which the continuous cold atom beam and central portion of the incident laser trapping light exit along a dark column. For use in an atomic clock system, a collimating and deflecting pumping laser provides transverse cooling of the atoms beam to bend and separate the cold atom beam from trapping laser light for reducing light shifts of the atomic clock operating frequency. The atomic clock can be a microwave cavity or Raman-type atomic clock.

Abstract: In an atomic oscillator, a high-frequency converting circuit converts the output of a standard oscillator into a high frequency signal such that the frequency of the high frequency signal multiplied by a low natural number equals an atomic resonant frequency signal. The high frequency signal is then multiplied by a low natural number in an active, low-natural-number multiplier circuit to convert the output frequency of the standard oscillator into a resonant frequency to be input to the atomic oscillator. The result is that, without using a passive, high-natural-number multiplier circuit, such as a varactor diode, which is expensive, it is possible to convert the output frequency of the standard oscillator into a resonant frequency signal of a rubidium atom, thus downsizing the circuits of the atomic oscillator and reducing the term and cost of manufacture.

Abstract: An atomic frequency standard is disclosed where optical pumping of the resonance cell is achieved by coherent light and the pumping results in Coherent Population Trapping of the resonant alkali metal atoms. The fabrication of frequency standards of substantially reduced size and weight is permitted by use of solid state laser sources having certain integrated optical modifier elements and a resonance cell of metallic construction.

Abstract: An atomic frequency standard based on coherent microwave emission from an ensemble of hydrogen or alkali metal atoms at their ground state hyperfine frequency. Hydrogen or alkali metal atoms are prepared in a coherent state by means of a radiation field resonant with the atoms at their hyperfine frequency prior to their entering into the emission region. The coherent microwave radiation emission results from the phenomenon of stimulated emission of radiation in a storage bulb placed in a cavity tuned to the hyperfine frequency. Because the atoms enter the cavity already prepared in a coherent state, radiation is emitted without threshold regarding the atomic flux or the cavity quality factor. The atoms emit their energy at their natural frequency perturbed only slightly by secondary effects such as spin exchange collisions, wall collisions and second order cavity pulling.

Abstract: An improved optically pumped atomic frequency standard in which excitation light intensity entering the resonance cell is controlled and maintained independently of the optical pump.

Abstract: The invention disclosed herein is a cell construction for use in optically activated atomic frequency standards. The cell includes a stiff non-magnetic metallic chamber body having an integral cold weldable tubulation through which the atomic source material may be charged and the tubulation pinched off to seal the chamber. Optically transparent windows for introducing light radiation into the chamber and receiving light signals generated therein are sealed to the chamber.

Abstract: A quantum medium is excited by laser light from a first electromagnetic source and is also exposed to radiation from a second electromagnetic source such that the radiation field from this second source is non-uniform in a direction transverse to the direction of passage of laser light though the quantum medium. The laser light that has passed through the quantum medium is detected by two photo detectors at two different locations transverse to the passage of laser light, with the light detected by each photo detector having passed through a substantially different region of the quantum medium than the light detected by the other photo detector, and with the radiation field from the second electromagnetic source having different intensities in these two regions. The different radiation field intensities in these two regions produce at each photo detector different intensity levels of the laser light that varies with the frequency of the second source of electromagnetic radiation.

Abstract: A method of controlling the amplitude of the microwave signal applied to an atomic clock comprising an atomic resonator and a device for interlocking an ultra-stable oscillator in follow-up relationship with the atomic resonance, adapted to produce the signal from which the microwave signal is derived, the method consisting in transforming the amplitude of the microwave signal before its application to the atomic jet resonator according to a law such that the shape of the curve of atomic response versus the amplitude of the microwave signal be symmetrical over a wide extent about the vertical line passing through the maximum of the response.

Abstract: An extremely small and inexpensively manufactured physics package for an atomic frequency standard can be provided with a microwave cavity having non-critical dimensions that is driven in a substantially TEM mode by a lumped LC means, the cavity resonant frequency being primarily determined by the lumped LC means. The lumped LC means can be any structure or combination of elements providing, at a selected microwave reference frequency, a resonant inductance and capacitance. Examples of such lumped LC means include, preferably, a rod or wire conductively attached to a wall of the microwave cavity as a lumped inductance and extending into the cavity to form, at its other end, a gap with an opposing cavity wall as a lumped capacitance; or a pair of rods or wires conductively attached to opposing walls and extending therefrom as a lumped inductance to form a gap therebetween as a lumped capacitance.

Abstract: A passive atomic frequency standard such as a Rubidium Frequency Standard or a Cesium Frequency Standard, using a microprocessor or equivalent circuit as part of its Frequency Locked Loop. The microprocessor phase modulates (pm) the RF signal which is introduced into the Atomic Resonator, and demodulates the output signal. The modulation and demodulation are performed by frequency hopping or spread spectrum techniques. Secondly, the microprocessor samples and integrates the error signal from the atomic resonator (Physics Package or Atomic Tube) with a sampled weighted- sum technique and thus better filters the noise, improves the Signal to Noise Ratio, rejects large noise like spikes, etc. Thirdly, the microprocessor saves the last control voltage of the Voltage Controlled Oscillator (VCO) to ease the start-up of the device as well as to keep the VCO at the last frequency in case the atomic resonator fails to function.

Abstract: A frequency standard generator includes a voltage controlled crystal oscillator (VCXO) for generating high stability output signal, a radio wave receiver to receive a radio wave which includes a high accuracy reference time signal, a time interval measuring circuit which measures a phase difference between the reference time signal and the output signal of the VCXO; a frequency control processor which determines control data based on the phase difference data to phase lock the output signal of the VCXO to the reference time signal, a frequency deviation data generator for compiling the phase difference data to obtain frequency deviation trend data of the VCXO, and a compensation data generator for generating compensation data based on the frequency deviation trend data to compensate frequency changes in said VCXO when the reference time signal is unavailable.