Quantum frequency standard

 

The invention relates to techniques for frequency stabilization and can be used to generate a timeline. Technical result achieved - receiving signal with less noise frequency instability. Quantum frequency standard contains connected in ring adjustable crystal oscillator, frequency multiplier, frequency Converter, quantum discriminator and the driver control voltage, and the frequency synthesizer, the frequency divider. 1 Il.

The invention relates to techniques for frequency stabilization and can be used in the quantum frequency standards passive type, for example, for formation of the timeline.

The principle of operation of the quantum frequency standard passive type based on the frequency stability of the crystal oscillator according to the frequency of the spectral line absorption of the working transition of quantum discriminator [1]. The latter is ensured by the inclusion adjust the crystal oscillator in the ring of automatic frequency control), where reference is used, the frequency of the working transition of quantum discriminator. This principle quantum frequency standard allows soo what ignalum quantum frequency standard, for the time intervals of measurement, large 1 sec. When this noise is caused by the elements of the ring frequency, converts a frequency signal of the crystal oscillator to the frequency of the working transition of quantum discriminator, contribute to the instability frequency of the output signal of the quantum frequency standard ("noise" instability), thereby limiting the potential capacities of quantum frequency standard.

Among quantum frequency standards of this type are known, for example, the quantum frequency standard gas cell [2], containing serially connected in a closed loop control adjustable crystal oscillator, a phase modulator, a frequency Converter, quantum discriminator and the driver control voltage to adjust the crystal oscillator, the second input of the shaper control voltage is connected to the second output of the phase modulator. The output of the quantum frequency standard [2] is the output of the selective amplifier connected to the output of the adjustable oscillator. For the output signal of the quantum frequency standard [2] taken from the specified output of the selective amplifier, a characteristic not the walls quantum frequency standard [3], containing serially connected in a closed loop control adjustable crystal oscillator, frequency Converter, quantum discriminator and the control unit adjust a quartz oscillator and a low-frequency generator, the output of which is connected to the second inputs of the specified frequency Converter and a control unit. In the part of the specified control unit includes a processing unit of the error signal and the integrator. The output signal of the quantum frequency standard [3] is removed from the output of the adjustable oscillator. For the output signal characteristic of the frequency fluctuations due to the influence of noise of the frequency Converter and the low-frequency generator.

The technical nature closest to the claimed invention is a quantum frequency standard gas cell [4], which is taken as a prototype. Quantum frequency standard, adopted as a prototype, contains serially connected in a closed loop control adjustable crystal oscillator, frequency multiplier, frequency Converter, quantum discriminator and the driver control voltage, tuning crystal oscillator frequency, and syncstate and the second input of the shaper control voltage, and the input is connected to the output of the adjustable oscillator, with the output of the adjustable oscillator is the output of the quantum frequency standard.

Work quantum frequency standard, adopted as a prototype, as follows. The output signal of the adjustable oscillator to the input of the frequency synthesizer. On the basis of this signal in the frequency synthesizer is formed by the low-frequency signal whose frequency is equal to the width of the contour line quantum discriminator (of the order of hundreds of Hertz). This low frequency signal is removed from the second output of the frequency synthesizer. In addition, the frequency synthesizer is formed of a high-frequency signal, phase modulated or frequency specified by the low-frequency signal. This frequency modulated signal is taken from the first output of the frequency synthesizer. The output signal of the adjustable oscillator is supplied also to the input of the frequency multiplier, which generates at its output a signal with the frequency increased to an integer number of times. From the output of the frequency multiplier signal is supplied to the first input of the frequency Converter, to the second input of which receives the high frequency of modelirovanie the education of their input signals in the frequency Converter are formed modulated harmonic of the carrier frequency, equal to the sum and difference frequencies of the input signals. One of the harmonics with carrier frequency equal to, for example, the amount of frequency coinciding with the frequency of the working transition of quantum discriminator, filtered and used as the output signal of the frequency Converter. The output signal of the frequency Converter is input to the quantum discriminator, the output of which is the result of interaction with the working substance you receive an error signal containing harmonics, multiples of the frequency of low-frequency modulation of the output signal of the frequency synthesizer. The error signal is fed to the first (signal) input shaper control voltage, where the first harmonic error signal is amplified, synchronously detected relative phase of the reference signal from the second output of the frequency synthesizer at the second (reference) input shaper control voltage, and then filtered, for example, by using a lowpass filter with separation constant component.

The polarity of the thus obtained control voltage carries information about the sign of the error of the carrier frequency inverter output frequency relative to the frequency of the working transition of quaia is sent to a control input of the adjustable oscillator, changing the frequency of its output signal so that the carrier frequency inverter output frequency equal to the frequency of the working transition of quantum discriminator. Thus, due to the ring frequency stability frequency adjustable oscillator and it generates the output signal of the quantum frequency standard is determined by the frequency stability of the working transition of quantum discriminator. The ring control provides primarily compensation of the frequency deviation of the crystal oscillator, caused by aging, thereby improving "srednekraevoy" (measurement time from 1 to 1000) and "long-term" (time dimension greater than 1000 (C) the frequency instability. However, the frequency fluctuation due to noise elements ring control, full persists.

A distinctive feature of quantum frequency standard, adopted as a prototype, is the convenience of using it to build a timeline. This is due to the presence in its composition of a frequency synthesizer that generates the frequency conversion signal, the carrier frequency which is not located in an integer ratio with the frequency of the crystal oscillator. This allows the use of kVA is dostatkom this quantum frequency standard is a significant contribution of the noise components in the frequency instability of the output signal of the quantum frequency standard, remove from the output of the crystal oscillator.

The task, which is aimed by the invention, is the formation of the output signal of the quantum frequency standard, characterized by less "noise" frequency instability. The technical result is obtained in case of realization of the invention, which consists in receiving the quantum frequency standard signal with less "noise" frequency instability, allows more efficient use of this signal in order to form a timeline.

The essence of the invention lies in the fact that in quantum frequency standard, containing serially connected in a closed loop control adjustable crystal oscillator, frequency multiplier, frequency Converter, quantum discriminator and the driver control voltage, the output of which is connected to the control input of the adjustable oscillator, and the frequency synthesizer, the first and second outputs of which are connected respectively to the second input of the frequency Converter and the second input of the shaper control voltage, and the input is connected to the output of the adjustable oscillator, the additional is the notes constitutes the output of the quantum frequency standard.

The peculiarity of the proposed technical solution is a new construction output part of the quantum frequency standard is based on the properties of fluctuation processes in the ring control that allows you to create an output signal with less "noise" frequency instability.

The essence of the invention, its feasibility and industrial applicability is illustrated the block diagram, shown in the drawing.

Declare quantum frequency standard contains serially connected in a closed loop control adjustable crystal oscillator 1, a frequency multiplier 2, the frequency Converter 3, the quantum discriminator 4 and the driver 5 control voltage, the output of which is connected with the control input of the adjustable oscillator 1. The composition of the quantum frequency standard also includes a frequency synthesizer 6, the first output of which is connected with the second input of the frequency Converter 3, a second output connected to the second input of the shaper 5 control voltage, and the input is connected to the output of the adjustable oscillator 1. In addition, the quantum frequency standard contains further introduced the frequency divider 7, the inlet of which is connected the antova frequency standard, with the exception of the frequency divider 7 are known from prototype elements that perform the same as the prototype of the function. Additionally, the frequency divider 7 may be performed, for example, on the basis of industrial manufactured microwave frequency dividers FI4-DF-010-060, FI4-DF-050-080, FI4-DF-080-120, prescaler IE and digital frequency dividers in chip design with additional filtering of the main harmonic if necessary.

Declare quantum frequency standard is as follows.

The output signal of the adjustable oscillator 1 with a frequency equal to f1, to the input of the frequency synthesizer 6. On the basis of this signal in the frequency synthesizer 6 is formed (for example, by dividing the frequency of the low-frequency signal with frequency FMtaken from the second output of the frequency synthesizer 6. Frequency FMequal to the width of the contour line absorption quantum discriminator (of the order of hundreds of Hertz). In addition, the frequency synthesizer 6 is formed detachable from the first output of the frequency synthesizer 6 high-frequency signal USCwith carrier frequency fSC=KSCf1where KSC- conversion frequency synthesizer the cash with frequency FM: USC= A1cos[2fSCt+(t)], where(t)=Dsin(2FMt); t is the time.

The output signal of the adjustable oscillator 1 is supplied also to the input of the frequency multiplier 2 with the multiplication factor of frequency N, which multiplies the input frequency to an integer number of times until a frequency equal to fUCH= Nf1. And N>>KSCand fUCH>>fSC>>fF.

From the output of the frequency multiplier 2 signal UUCH=A2cos(2fUCHt) is fed to the input inputs of the frequency divider 7. In the frequency divider 7, the input signal representing the analog harmonic signal is divided in frequency to an integer number of times. The output signal of the frequency divider 7 is an output signal of the quantum frequency standard and depending on the further use can be in the form of pulsed periodic posledovatel the coherence by additional filtering its main harmonic.

From the output of the frequency multiplier 2 signal UUCH=A2cos(2fUCHt) is supplied also to the first input of the frequency Converter 3. To the second input of the frequency Converter 3 from the first output of the frequency synthesizer 6 receives the high-frequency modulated signal USC=A1cos[2fSCt+(t)]. In the result of the transformation (e.g., quadratic) these input signals in the frequency Converter 3 are formed harmonics with frequencies equal to nfUCHmfSCwhere n and m are integers. These harmonics modulated in phase with frequency FM. One of these harmonics, the carrier frequency of which is equal to, for example, the sum of the frequencies fUCH+fSCcoincides with the frequency f0work transition quantum discriminator, filtered and used as the output signal of the frequency Converter 3: UFC=KFCAnd1And2(t)], where KFC- transfer coefficient of the frequency Converter 3.

The output signal of the frequency Converter 3 is input to the quantum discriminator 4, the output of which is the result of interaction with the working substance you receive an error signal containing harmonics, multiples of the frequency FMlow-frequency modulation of the frequency Converter 3. This signal is applied to the first input of the shaper 5 control voltage. In the imaging unit 5, the first harmonic error signal is allocated (or filtered, amplified, synchronously detected relative phase of the reference signal from the second output of the frequency synthesizer 6, then through a low-pass filtering (using a low pass filter or integrator) can be extracted from it a permanent component.

The polarity of the thus obtained control voltage contains information about the sign of the error of the carrier frequency of the output signal of the frequency Converter 3 versus frequency f0work transition quantum discriminator 4, and the voltage value information about the mismatch. The control voltage is supplied to the control input of the adjustable oscillator 1 from the ub>0work transition quantum discriminator 4. When the perturbation frequency, and the phase and amplitude of the output signal to adjust the crystal oscillator 1 is the nonlinear perturbation is converted by the frequency multiplier 2, the frequency Converter 3 and quantum discriminator 4 with the formation of the output quantum discriminator error signal, which after passing through the imaging unit 5 control voltage sweeps the frequency of the adjustable oscillator 1 to the disappearance of the error signal at the output of the quantum discriminator 4.

Thus, due to the ring frequency instability frequency adjustable oscillator 1 is determined by the instability frequency f0work transition quantum discriminator 4. However, as noted above, the ring control improves "long-term" frequency fluctuation compensating the first frequency deviation of the crystal oscillator, caused by aging and instability frequency for "medium" and "long" time interval measurement (>1 sec), due, in particular, the noise of the elements, full ring control persists.

Analytical estimation of the noise contribution of the elements of the ring control signal, which is directly compared with the frequency f0work transition quantum discriminator 4, i.e., the carrier output signal of the frequency Converter 3. Somewhat greater instability frequency is the output signal of the frequency multiplier 2, and the highest value of frequency instability has a signal to adjust the crystal oscillator 1.

Found the uneven distribution of frequency instability in the ring frequency can be explained as follows. Any perturbation frequency adjustable oscillator 1 can be characterized by the spectral density of noise disturbance. As the signal travels around the ring control from the adjustable oscillator 1 to the quantum discriminator 4 is a nonlinear transformation of the noise perturbation with distortion of the spectral density perturbations. Due to these distortions working off ring control source of disturbance frequency on the output of the adjustable oscillator 1 through the distorted spectral density perturbations at the output of the frequency Converter 3 (input quantum discriminator 4) may no longer be adequate for the crystal oscillator 1, since the ring HRA works perturbations in the input signature at the output of the crystal oscillator 1.

The main changes of the spectral density perturbations adjust the crystal oscillator 1 occur when high-frequency multiplication of the output signal of the crystal oscillator 1 frequency multiplier 2, i.e., in ring frequency with the greatest degree of nonlinearity and the frequency of the frequency conversion. The frequency multiplier 2 increases the phase fluctuations in N times, and the amplitude in M times, where M is the degree of nonlinearity of the frequency multiplier [5] . Thus the spectral density of phase and amplitude fluctuations increase, respectively, in the N2and M2time. Moreover, with the increase of the multiplication factor of frequency N spectrum of initial perturbations is expanding, i.e., there is an additional distortion of the spectral density [5]. In addition, the correlation between the phase (frequency) and amplitude fluctuations (for example, due to temperature changes, adjust the crystal oscillator 1) also leads to a distortion of the spectrum, reflected in the skewness of the spectral density of the noise (disturbances) [6].

In addition to this, the distortion of the spectral density is influenced by intrinsic noise frequency multiplier 2 and the frequency Converter 3. The presence of data noise on the es increase of the spectral density of the noise at the outputs of the frequency multiplier 2 and the frequency Converter 3 in comparison with the spectral density of the original noise adjust the crystal oscillator 1.

Based on the detected fluctuation properties of processes in the ring frequency of the quantum frequency standard, in the inventive quantum frequency standard applied to new build its output side, namely to generate an output signal of the quantum frequency standard used inputs of the frequency divider 7 is connected to the output of the frequency multiplier 2, the output of which is characterized by a lower frequency instability than the signal at the output of the adjustable oscillator 1. In the output signal of the inventive quantum frequency standard characterized by a lower frequency instability, compared with the signal produced in the traditional way directly from the output of the adjustable oscillator.

Thus, the above shows that the claimed invention is technically feasible, industrial realizable and solves the problem by generating the output signal, characterized by less "noise" frequency instability, and therefore, less instability frequency for time interval measurement, large 1 sec, compared to the prototype.

Sources of information 1. A. I. Pitalev, A. A. Hive is dio. 1978.

2. GB 1384809, "Atomic frequency standard". MKI2N 03 3/12, G 01 N 21/24, H 10 P 7/06, publ. 19.02.1975.

3. EN 2034380, "Quantum frequency standard", MKI6H 01 S 1/06, publ. 30.04.1995.

4. F. Emma, G. Busca, P. Rochat. Atomic Clocks for Space Applications. //ION GPS-99 Proceedings, 1999, p.2285-2293 (prototype).

5. S. A. Akhmanov, S. E. D'yakov, And A. S. Chirkin. Introduction to statistical Radiophysics and optics. M.: Nauka, 1981, S. 347-357.

6. F. L. Walls. Correlation Between Upper and Lower Sidebands.//IEEE Trans. Ultr. Ferroel. and Freq. Control, v.47, 2, 2000, p.407-410.

Claims

Quantum frequency standard, containing serially connected in a closed loop automatic frequency adjust quartz oscillator, frequency multiplier, frequency Converter, quantum discriminator and the driver control voltage, the output of which is connected to the control input of the adjustable oscillator, and the frequency synthesizer, the first and second outputs of which are connected respectively to the second input of the frequency Converter and the second input of the shaper control voltage, and the input is connected to the output of the adjustable oscillator, characterized in that it further introduced the frequency divider, the input of which is connected to the output of the frequency multiplier,

 

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