JPS63187918A - Atomic oscillator - Google Patents

Abstract

PURPOSE:To obstruct an imperfect lock at the time of turning on a power source which follows up low grading of a voltage control crystal oscillator, by starting an integral operation of an integrator in accordance with a double wave component signal of an atomic resonance signal when the power source is turned on. CONSTITUTION:After a power source is turned on or after the power source is released, until each part reaches an operation stable area, there is no output in a lock detector 6, and an integrator 5 stops an integration operation, and outputs a set reference voltage. In accordance with its set voltage, a voltage control crystal oscillator (VCXO) 2 generates a frequency output which becomes an atomic resonance frequency. In this state, when each part reaches the operation stable area, and a double wave component output (2fL) of an atomic resonator 1 is detected by the lock detector 6, the integrator 5 starts its integral operation, therefore, even if the VCXO 2 of a low grade, whose frequency variable width is wide is used, the automatic lock can be surely executed, and it has an effect for a miniaturization and a low cost of an atomic oscillator.

Description

[Detailed Description of the Invention] [Summary] The present invention mainly provides voltage control by starting the integrating operation of an integrator in response to the second harmonic component signal level of an atomic resonance signal when the power is turned on. This invention discloses an atomic oscillator that is designed to prevent incomplete locking when power is turned on, which is caused by lower grade crystal oscillators.

[Industrial Field of Application] The present invention relates to an atomic oscillator, and particularly to its lock acquisition method.

The atomic oscillator, which controls the oscillation frequency of a voltage-controlled crystal oscillator based on the resonance frequency of atoms and molecules, has excellent long-term stability and is used as a high-precision reference signal source in communications, broadcasting, radio navigation, etc. It is widely used in fields such as measurement.

It is desired that such an atomic oscillator be made smaller and lower in cost.

[Prior Art] FIG. 4 shows the configuration of a conventional general atomic oscillator.

In the figure, 1 is an atomic resonator, 2 is a voltage controlled crystal oscillator (hereinafter referred to as VCXO), 3 is a phase modulator 7, a multiplier 8, a combiner 9, a mixer 10, and a low frequency (100 to 200
1 (square wave of z) oscillator 11;
is a preamplifier 12, a selection amplifier 13, and a synchronous detector 14.
5 is an integrator, and 6 is a lock detector consisting of a selection amplifier 15 and a resonance detector 16.

The operation of this atomic oscillator will be described below.

The output of vCXO2 is phase-modulated by a phase modulator 7 using a low-frequency signal (frequency fL) from a low-frequency oscillator 11, and further modulated to the atomic resonance frequency of the atomic resonator 1 by a multiplier 8, a synthesizer 9, and a mixer 12. μ (micro) that matches
The wave frequencies are multiplied and synthesized and input to the atomic resonator 1.

On the other hand, as shown in FIG. 5, the input μ-wave frequency of the DC output of the atomic resonator 1 is the atomic resonance frequency f. It has a characteristic curve 17 that has a minimum value when it matches. This input microwave frequency is phase modulated at frequency rL, so if the input frequency is slightly lower than the resonant frequency fo (100 to 200 tlz) as shown in waveform A, the frequency rL shown in waveform B If the μ wave is slightly higher than the resonant frequency fo as shown by waveform C, a resonant signal having a frequency f and an inverted phase with respect to waveform B is output. Also, when the input μ wave matches the resonant frequency ro as shown in waveform E, as shown in waveform F,
A resonance signal of 2fL, which is twice the modulation frequency fL, is output.

These B, D, or F are preamplifiers 12 in FIG.
are amplified together. Of these, signals B and D at frequency f are interpretively amplified by a selective amplifier 13. Next, the synchronous detector 14 synchronously detects the signal B or D using the low frequency rL from the low frequency oscillator and generates cx as shown in FIG.
o Send the control voltage to the integrator 5. The integrator 5 is provided to increase the loop gain and smooth the output of the synchronous detector, and matches the frequency of vCXO2 to the atomic resonance frequency according to the smoothed output voltage. In other words, a suppressing tita pressure is output such that the output of the synchronous detector 14 becomes zero.

On the other hand, the signal F at frequency 2 is selectively amplified by the selection amplifier 15, and the resonant state of the atomic resonator 1 is monitored by the resonance detector 16 to detect the second harmonic component signal, indicating that atomic resonance is occurring. , that is, it indicates that the oscillator is operating normally.

[Problems that the invention sought to solve] In such conventional atomic oscillators, a highly stable crystal oscillator is used as the vCXO2, and the frequency variable width by the control voltage is always within the range of the atomic resonance characteristics (Figure 5). It was designed to fit within the range.

Therefore, after the stabilization time of each part after the power is turned on, the μ-wave frequency synthesized from the frequency of the vCXO2 is always within the resonance characteristic range, so the atomic resonance signal is detected and the integrator 5 operates effectively. , the frequency of vCXO2 is automatically locked to the resonance frequency 10.

However, when trying to make an atomic oscillator smaller and lower in price, this vCXO2 must also be considered, but generally speaking, when trying to make the atomic oscillator smaller and cheaper, it has the disadvantage that its frequency stability decreases.

In order to use such a low-grade vCXO for atomic oscillators and to operate normally for a long period of time, vcx
It is necessary to have a frequency variable width due to the control voltage that is larger than the total amount of variation including the aging of o.

On the other hand, since the integrator 5 starts integrating immediately after the power is turned on, its output voltage becomes the power supply voltage or ground potential in a relatively short time and remains constant. When applied to vcx
Since the frequency variable range of o is wide, μ synthesized from vcxo
A problem arises in that the wave frequency greatly deviates from the detection range of the atomic resonance signal, and the atomic oscillator remains unlocked indefinitely.

Therefore, an object of the present invention is to provide an atomic oscillator with vcx
The object of the present invention is to realize a lock acquisition method to improve the above-mentioned drawbacks associated with the lower grade of o.

[Means for Solving the Problems] FIG. 1 is a diagram conceptually showing an atomic oscillator according to the present invention for achieving the above object, where 1 is an atomic resonator, and 2 is a voltage-controlled crystal oscillator. (VCX○), 3 is a frequency synthesizer that converts the output frequency of VCXO2 to the atomic resonance frequency region, 4 is a VCXO corresponding to the output signal of atomic resonator 1
2 is a frequency servo circuit that controls the servo circuit 4; 5 is an integrator that smooths the output of the servo circuit 4 and outputs the uI control voltage of the VCXO 2; 6 is a lock detector that detects the second harmonic component signal of the atomic resonance signal; In particular, in the present invention, the integration operation of the integrator 5 is controlled in response to the second harmonic component signal level of the resonance signal output from the lock detector 6.

[For production]

In the atomic oscillator shown in Figure 1, after the power is turned on or after the power is restored, until each part reaches its stable operating region,
There is no output from the lock detector 6, and at this time, the integration operation of the integrator 5 is stopped, and the integrator 5 outputs the set reference voltage.

Depending on the set voltage, the VCXO2 generates a frequency output that corresponds to the atomic resonance frequency. It is not until each part reaches a stable operation region and the second harmonic component output of the atomic resonator 1 is detected by the lock detector 6 that the integral operation of the integrator 5 is started.

[Embodiment] A third embodiment of the atomic oscillator of the present invention is shown in FIG. 2 below. Note that the same reference numerals shown in FIG. 2 as in FIG. 4 indicate the same parts 3.

The major differences between this embodiment and the conventional example shown in FIG. 4 are as follows:
Second harmonic component obtained from atomic resonator 1 (frequency 2fL)
The oscillator ('P) of the integrator 5 is thereby controlled, and the atomic oscillator shown in FIG. 2 utilizes the output of the resonance detector 16 as a signal with a frequency of 2rL.

As shown in FIG. 3, the integrator 5 shown in FIG. 18 in parallel with the capacitor 18
Open or short-circuit both ends. Note that the reference voltage Vref of the operational amplifier 17 is set to the center value of the control voltage of vcxo2.

Note that the switch SW is structured to be closed when the power is turned off.

In the atomic oscillator configured in this way, when the power is turned on, the atomic resonator 1 and VCXO 2 require a predetermined stabilization time, so during that time the conditions for detecting the atomic resonance signal are not established, and the signal at frequency 2fj is I can't get it. At this time, the switch SW remains closed and the capacitor 18 is short-circuited. In this case, the integrator 5 cannot perform an integration operation, and only the control center voltage of the reference voltage Vre' is applied to the VCXO2.

Therefore, at this voltage Vref, μ near the resonant frequency fo
If the output frequency of the VCXO 2 is adjusted in advance so as to obtain the wave frequency, the atomic resonator 1 will definitely cause atomic resonance after a predetermined stable time has elapsed, and the halo 5 signal 2 "L" will be obtained. When this resonance signal 2fL is generated (above a certain level), the switch SW is opened, and at this time, the integrator 5 starts the integrator 1, and the frequency of the VCXO2 can be locked to the atomic resonance frequency. Become.

Although the case where both ends of the integrating capacitor are controlled is shown here, it goes without saying that the object of the present invention can be achieved using any sub-leg means as long as it stops the integrating function.

[Effects of the Invention] As described in item 2, according to the atomic oscillator of the present invention, the integration operation of the integrator is controlled in response to the second harmonic component signal level of the atomic resonance signal, so the atomic oscillator At the time of startup, the input μ-wave frequency generated from the VCXO does not deviate from the range in which the atomic resonance signal is detected, and automatic locking is possible even when using a low-grade ■CX○ with a wide frequency variable range. This has a great effect on reducing the size and cost of atomic oscillators.

[Brief explanation of the drawing]

FIG. 1 is a principle configuration diagram showing an atomic oscillator according to the present invention, FIG. 2 is a block diagram showing an embodiment of the atomic oscillator according to the present invention, and FIG. 3 is a concrete diagram of an integrator used in the atomic oscillator according to the present invention. Circuit diagram, Figure 4 is a block diagram of a conventional atomic oscillator, Figure 5 is a graph showing the relationship between the output of the atomic resonator and the input μ-wave frequency, and Figure 6 is the synchronous detection output and input μ-wave It is a graph diagram showing the relationship with frequency. In Figure 1, 1 is an atomic resonator, 2 is a voltage controlled crystal oscillator (VCX○), 3 is a frequency synthesizer, 4 is a servo circuit, 5 is an integrator, 6 is a lock detector, 18 is a capacitor, and SW is switch, shown. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) The output of the voltage controlled crystal oscillator (2) is converted into an atomic resonance frequency by the frequency synthesizer (3), and the atomic resonance signal is supplied to the integrator (5) via the frequency servo circuit (4). In an atomic oscillator that detects a second harmonic component signal of an atomic resonance signal with a lock detector (6) and controls the voltage controlled crystal oscillator (2) with the output of the integrator (5), the lock detector (6) 2.) An atomic oscillator characterized in that the integrating operation of the integrator (5) is controlled in response to the second harmonic component signal level output from the integrator (5). (2) Integration is performed by connecting a switch that closes when the second harmonic component signal is not detected in parallel with the integrating capacitor of the integrator (5), and opening the switch in accordance with the second harmonic component signal. The atomic oscillator according to claim 1, wherein the atomic oscillator starts operation.