JP2673365B2 - Resonant frequency control device for cavity resonator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resonance frequency control device for a cavity resonator, which controls a resonance frequency of a cavity resonator forming a part of an oscillator, and more particularly to a resonance frequency control device. The present invention relates to a resonance frequency control device for a cavity resonator using a method called a frequency sensing method.

The resonant frequency control device for a cavity resonator according to the present invention is used in an oscillator such as a hydrogen maser (MASER) atomic frequency standard. The oscillation frequency of the hydrogen maser atomic frequency standard (hereinafter referred to as the hydrogen maser oscillator) is slightly drawn into the resonance frequency of the cavity resonator forming a part of the oscillator. Therefore, in order to obtain high frequency stability over a long period of time, the resonance frequency of the cavity resonator must always match the resonance frequency of the hydrogen atom. Therefore, a resonance frequency control device for the cavity resonator is required.

[Conventional technology]

The first example of the use of a method of controlling the resonance frequency of a cavity resonator called a resonance frequency sensing method is the hydrogen maser oscillator described above. Therefore, the description of the present invention will be given taking the hydrogen maser oscillator as an example.

Regarding the principle of oscillation of the hydrogen maser oscillator, the importance of frequency stability of the cavity resonator thereof, the features of the hydrogen maser oscillator and its use, etc., the invention of the same applicant, "Resonator for hydrogen maser (Japanese Patent Application No. 60-183782) "and" Cavity resonator for hydrogen maser (Japanese Patent Application No. 62-223667) "and the like.

In addition, hydrogen pressure quenching method and resonance frequency sensing method are generally known as methods for controlling the resonance frequency of the cavity resonator in the hydrogen maser oscillator, and the principles and features of each method are the same as those of the same applicant. Related invention "Automatic tuning system of hydrogen maser (Japanese Patent Application No. 59-38683)"
And "Switched frequency synthesizer for use in cavity resonator frequency control device (filed on February 4, 1989)" and the like.

Either control method detects the shift amount (Δfc) of the resonance frequency, and the temperature of the cavity resonator or the variable capacitance element (varactor diode) coupled to the cavity resonator is detected by an error signal proportional to the detected shift amount. The resonance frequency (fc) is controlled by adjusting the bias voltage.

In the hydrogen pressure quenching method, a method of increasing / decreasing the amount of hydrogen beam is adopted as a method of detecting the shift amount (Δfc) of the resonance frequency, so that the frequency stability is deteriorated due to the change of the hydrogen maser oscillation power. In addition, it requires a highly stable oscillator as a reference frequency signal, and has a drawback in that the control system is open loop and thus lacks operational stability.

On the other hand, the resonance frequency sensing method uses two sensing frequency signals for sensing (a signal having a frequency fo + Δf and a signal having a frequency fo−Δf, or a signal obtained by frequency-modulating a signal having a frequency fo + Δf with a predetermined amplitude and a frequency fo− A signal obtained by frequency-modulating a signal of Δf with a predetermined amplitude) is alternately input to the cavity resonator by the frequency control coupling element, and is picked up by the pickup element from the cavity resonator. The shift amount (Δfc) of the resonance frequency is detected by the difference in the amplitude of the.

FIG. 2 is a diagram for explaining the sensing according to the embodiment of the present invention, and the conventional sensing will be described in some detail with reference to this diagram.

Conventionally, first, a signal having a frequency substantially the same as the resonance frequency of the hydrogen atom (center frequency fo) is created, and then a signal having a frequency substantially the same as the resonance frequency of the hydrogen atom is usually given a Q curve (resonance characteristic curve). The signal with a frequency of about 1/2 of the half-value width is added and subtracted to obtain two signals (frequency fo + Δf signal and frequency
fo-Δf signal) and use the two signals as two sensing frequency signals, or two signals (frequency fo
After making a signal of + Δf and a signal of frequency fo−Δf),
The two sensing frequency signals are produced by subjecting both signals to frequency modulation of the same predetermined amplitude.

Then, by using the two sensing frequency signals created in this way, by controlling the resonant frequency fc of the cavity resonator so that the amplitude difference between the two signals picked up becomes zero, The center frequency fo, that is, the resonance frequency peculiar to the hydrogen atom, was made to coincide with almost the same frequency.

When using signals of frequency fo ± Δf, the cavity resonator acts like a bandpass filter with a high Q, and the amplitude of the picked up signal depends on the resonance characteristics of the cavity resonator at the frequency of each signal. Becomes This will be described with reference to FIG.

The maser oscillation frequency fm of the hydrogen maser oscillator is controlled so as to match the resonance frequency specific to the hydrogen atom. here,
Assuming that the maser oscillation frequency fm matches the resonance frequency peculiar to the hydrogen atom, the center frequency fo in FIG. 2 and the maser oscillation frequency fm of the hydrogen maser oscillator substantially match. The frequencies of the two sensing frequency signals are approximately Δf from the maser oscillation frequency fm shown in FIG.
The frequencies are separated from each other. Since the Q curve is almost symmetrical about the axis of the resonance frequency fc, the resonance frequency is
If fc matches the maser oscillation frequency fm of the hydrogen maser oscillator, the Q curve amplitude (resonance characteristic value) is the same at frequencies separated from the maser oscillation frequency fm by frequency Δf. The two sensing frequency signals are input to the cavity resonator, and the extracted signal has an amplitude corresponding to the Q curve amplitude at the frequency of the sensing frequency signal. Then, if the Q curve amplitudes for the two sensing frequency signals are the same, the amplitudes of the signals extracted from the cavity resonator will be the same. Therefore, the resonance frequency fc of the cavity resonator is adjusted so that this difference in amplitude becomes zero.
By controlling, the resonance frequency fc matches the center frequency fo (≈resonance frequency peculiar to hydrogen atom).

In addition, when a signal obtained by frequency-modulating a signal of frequency fo ± Δf is used, so-called slope detection is performed, and the amplitude of the picked-up signal depends on the Q curve of the cavity resonator at each signal frequency. It becomes a thing. This will be described with reference to FIG.

As described above, if the maser oscillation frequency fm matches the resonance frequency peculiar to the hydrogen atom, and the frequencies of the two sensing frequency signals become frequencies Δf apart from the maser oscillation frequency fm of FIG. 2, respectively. To do. Q
Since the curve is almost symmetrical about the axis of the resonance frequency fc,
As shown in Fig. 2, if the resonance frequency fc matches the maser oscillation frequency fm of the hydrogen maser oscillator, the maser oscillation frequency fm
The slopes of the Q curve in the vicinity of the frequencies separated from each other by the frequency Δf are symmetrical. The two sensing frequency signals are input to the cavity resonator, and the extracted signal has an amplitude Q in the vicinity of the frequency of the sensing frequency signal.
It corresponds to the slope of the curve. Then, if the slopes of the Q curves corresponding to the two sensing frequency signals are symmetrical, the amplitudes of the signals extracted from the cavity resonator will be the same. Therefore, if the resonance frequency fc of the cavity resonator is controlled so that the difference between the amplitudes becomes zero, the resonance frequency fc matches the center frequency fo (≈resonant frequency unique to hydrogen atom).

To generate the two sensing frequency signals in the conventional resonance frequency control device for a cavity resonator using the resonance frequency sensing method, for example, a switched synthesizer as shown in FIG. 3 is used. Details of the principle are disclosed in "Switched Frequency Synthesizer Used for Cavity Resonator Frequency Control Device" by the same applicant filed on February 4, 1989.

[Problems to be solved by the invention]

However, in the conventional resonance frequency control device for the cavity resonator, taking the resonance frequency control device for the cavity resonator of the hydrogen maser oscillator as an example, two sensing frequency signals (frequency
When generating a signal of fo ± Δf or a signal obtained by frequency-modulating a signal of frequency fo ± Δf), a signal having a frequency (frequency fo) equal to the resonance frequency specific to the hydrogen atom is used. The sensing frequency signal (frequency fo ± Δf signal or frequency
There is a phenomenon called center frequency carrier leak which is driven into the cavity resonator together with the signal of fo ± Δf (frequency-modulated signal). Since the frequency fo of the signal leaked into the cavity resonator is extremely close to the maser oscillation frequency fm of the hydrogen maser oscillator, the signal of the frequency fo and the signal of the frequency fm are coupled, and the phase shifts to cause weak oscillation. There is a problem that it causes a level change in the signal of the frequency fm. This level fluctuation is one of the major factors that impair the short-to-medium-term stability, which is most important in hydrogen maser oscillators.

There is also a problem that the frequency signal generation method of the switched synthesizer used for generating the sensing frequency signal becomes complicated.

An object of the present invention is not to change the oscillation level of the oscillator, the circuit for generating the sensing frequency signal is simple,
It is to realize a resonance frequency control device for a cavity resonator.

[Means and actions for solving the problem]

In order to solve the above-mentioned problems, a resonance frequency control device for a cavity resonator according to the present invention is designed to detect a shift amount of a resonance frequency of a cavity resonator forming a part of an oscillator, and to detect different predetermined frequencies. A sensing frequency generator that alternately generates two sensing frequency signals having a frequency, two inputs and a variable capacitance element, and one of the two inputs receives the two sensing frequency signals. A frequency control coupling element for coupling the input signal to the cavity resonator, a pickup element for extracting two sensing frequency signals coupled to the cavity resonator, and a pickup element via the pickup element. A detector for detecting the two sensing frequency signals extracted by the detector, and an error signal corresponding to the difference in amplitude between the two sensing frequency signals detected by the detector. In the resonance frequency control device of the cavity resonator, which is provided with an error signal generation unit that generates the error signal and sends the error signal to the other input of the two inputs of the frequency control coupling element, the signal output from the oscillator is A clock signal generator for generating a phase-locked clock signal and outputting a reference frequency signal and a switching period signal based on the clock signal is provided, and the sensing frequency generator has two types of frequency division ratios. A variable frequency divider whose frequency division ratio is switched by the switching period signal, a phase comparator for comparing the phases of the output signal of the variable frequency divider and the reference frequency signal, and a phase comparison output signal of the phase comparator. In response, the two frequency signals corresponding to the two types of frequency division ratios are alternately generated and output to the variable frequency divider, and the two frequency signals are alternately output. It has a PLL circuit.

In the case of the hydrogen maser oscillator, which does not use the signal of the same resonant frequency as the hydrogen atom in generating the two sensing frequency signals, the above-mentioned configuration is not used, so that the sensing frequency signal has a frequency close to the oscillation frequency of the oscillator. Since no component is included, the phenomenon like the center frequency carrier leak does not occur. Also, the circuit for generating the sensing frequency signal is simplified.

〔Example〕

FIG. 1 is a block diagram of an embodiment of a resonance frequency control device for a cavity resonator according to the present invention, and FIG. 2 describes sensing of an embodiment of a resonance frequency control device for a cavity resonator according to the present invention. FIG.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

The cavity resonator of this embodiment will be described as a cavity resonator of a hydrogen maser oscillator.

In the present invention, first, the reference frequency signal fa and the switching period signal f
A clock signal generator 1 for making b is prepared. This clock signal generator 1 is a highly stable voltage controlled crystal oscillator (VCXO) (not shown) that is phase-locked to the maser oscillation frequency fm of the oscillation signal picked up by the pickup element from the cavity resonator of the hydrogen maser oscillator. A clock signal is generated by dividing or multiplying the output signal, and various signals such as the reference frequency signal fa and the switching period signal fb are generated based on this clock signal. Since the signal output from the clock signal generator 1 is based on the maser oscillation frequency of the hydrogen maser oscillator as described above, it has extremely high stability. The signal picked up by the pickup element includes a sensing frequency signal, which will be described later, in addition to the oscillation signal. The oscillation signal extracted from the picked-up signal by a circuit (not shown) conventionally used is used for phase synchronization of the clock signal generator 1, and also by a circuit (not shown) conventionally used. Output signal.

Next, the reference frequency signal from the clock signal generator 1
fa is received by a PLL circuit B (variable frequency synthesizer) including a phase comparator 2 including a low-pass filter, a voltage controlled oscillator 3, and a variable frequency divider 4.

The reference frequency signal fa (for example, frequency 10 kHz) is phase-compared with the output signal (10 kHz) obtained by dividing the output of the voltage controlled oscillator 3 by the variable frequency divider 4, and the comparison output is the voltage controlled oscillator. 3 is input to form a PLL.

Here, the variable frequency divider 4 outputs the output of the voltage controlled oscillator 3 to the switching period signal fb from the clock signal generator 1 (for example,
A clock signal with a slow cycle such as 10 Hz) is used to switch between two types of division ratios, while N ₁ (= 2042),
Divide by N ₂ (= 2039). Therefore, the output of the voltage controlled oscillator 3, that is, the output of the PLL circuit B is the upper side wave f _U (20.42 Mhz) and the lower side wave f _L (2
0.39MHz). The two primary sensing frequency signals are input to the level corrector 5.

In the level corrector 5, the amplitude difference between the two sensing frequency signals extracted from the cavity resonator is set to zero when the resonance frequency fc of the cavity resonator matches the resonance frequency of the hydrogen atom. , The level (amplitude) of the two input primary sensing frequency signals is corrected. Level correction is performed for each of the two primary sensing frequency signals in synchronization with the switching period signal fb (including the case where the amplitude of one signal is multiplied by 1), and the correction amount is two primary sensing frequencies. Each of the frequency signals is set based on the Q curve amplitude at the frequency when the frequency signal is input to the cavity resonator through the processing described later (that is, the frequency f _mU , f _mL of the third-order sensing frequency signal described later). It The base Q curve amplitude is when the resonance frequency fc matches the resonance frequency peculiar to the hydrogen atom, and is obtained in advance.

That is, if two sensing frequency signals of the same level (amplitude) are input to the cavity resonator, even if the two sensing frequency signals are extracted from the cavity resonator, even if the resonance frequency fc of the cavity resonator is Even if the resonance frequency is the resonance frequency peculiar to the hydrogen atom, there is a difference in amplitude corresponding to ΔL shown in FIG. In order to make the control based on the difference between the amplitudes other than zero as the reference based on zero, which is easier to control, in this embodiment, two sensings are performed by the level corrector 5 before the input to the cavity resonator. Level correction with a difference in the amplitude of the frequency signal (if read from FIG. 2, for example, the frequency f _m ′ becomes the third sensing frequency signal, the second sensing frequency signal f _U ′ becomes the frequency f
correction of amplifying the secondary sensing frequency signal f _L ′, which is the tertiary sensing frequency signal of _mL , by 2.3 times,
When the resonance frequency fc of the cavity resonator matches the resonance frequency peculiar to hydrogen atoms, the amplitude difference between the two sensing frequency signals extracted from the cavity resonator is set to zero.

In the section of conventional technology, the case of using a signal of frequency fo ± Δf as two sensing frequency signals and the case of frequency fo
The case where a signal obtained by frequency-modulating a signal of ± Δf is used has been described, but the level correction described above is a case where a signal that is not subjected to frequency modulation is used as two sensing frequency signals.

For reference, a case where the slope detection of the Q curve is performed using the frequency-modulated signal will be described.

In this case, the level corrector 5 frequency-modulates each of the two primary sensing frequency signals with a predetermined amplitude in synchronization with the switching period signal fb. At this time, the difference in amplitude between the two sensing frequency signals extracted from the cavity resonator is input so that it becomes zero when the resonance frequency fc of the cavity resonator matches the resonance frequency specific to the hydrogen atom. The levels of the two primary sensing frequency signals (amplitude of frequency modulation) are corrected. The level correction is performed by appropriately selecting the amplitude of frequency modulation when frequency-modulating each of the two primary sensing frequency signals, and the correction amount is determined by the process described below for each of the two primary sensing frequency signals. After that, it is set based on the slope of the Q curve in the vicinity of the frequency when input to the cavity resonator (that is, the frequencies f _mU and f _mL of the third-order sensing frequency signal described later). The underlying Q curve is obtained when the resonance frequency fc matches the resonance frequency peculiar to the hydrogen atom, and is obtained in advance.

Explaining in Fig. 2, the slopes of the Q curves near the frequencies f _mU and f _{mL of} the two sensing frequency signals are not symmetrical, and the slope near the frequency f _mU is more inclined than the slope near the frequency f _mL. Is steep. Therefore, two sensing frequency signals f of the same level (amplitude of frequency modulation)
_{Since mU} and f _mL are input to the cavity resonator, when the two sensing frequency signals are extracted from the cavity resonator, even if the resonance frequency fc of the cavity resonator is equal to the resonance frequency peculiar to the hydrogen atom. Even if it does, the amplitude of the sensing frequency signal of frequency f _mU becomes larger. Therefore,
Before inputting to the cavity resonator, the level compensator 5 performs level compensation to give a difference in the amplitude of frequency modulation to the two sensing frequency signals, and the resonance frequency fc of the cavity resonator is the resonance peculiar to hydrogen atom. When they match the frequency, the amplitude difference between the two sensing frequency signals extracted from the cavity resonator is set to zero.

The level corrector 5 outputs two level-corrected secondary sensing frequency signals f _U ′ and f _L ′. These two secondary sensing frequency signals f _U ′ and f _L ′ are output to the frequency converter 1
The frequency is converted by 1 and the secondary sensing frequency signal f
_U 'is tertiary sensing frequency signal f of the frequency 1420.42MHz
_mU , secondary sensing frequency signal f _L ′ is frequency 1420.39M
It becomes the 3rd sensing frequency signal f _{mL of} Hz. The third sensing frequency signal (f _mU , f _mL ) is input into the cavity resonator 10 through the frequency control coupling element 9 including a variable capacitance element such as a varactor diode, and the oscillation frequency f _m of the hydrogen maser oscillator is f _m = Sensing both sides of 1420.405751MHz. At this time, the cavity resonator 10 functions as a frequency discriminator.

The two third-order sensing frequency signals input to the cavity resonator 10 are detected via the pickup element 6. The detected two third-order sensing frequency signals are input to the amplitude detector 7 as a detector, and the output signal of the amplitude detector 7 is a signal including the amplitude information of the two third-order sensing frequency signals. Become. The signal is noise-suppressed by the error signal generating means 8 including a synchronous detector synchronized with the switching period signal fb and an integrating amplifier, and becomes an error signal corresponding to a difference in amplitude between the two third-order sensing frequency signals. In addition to the variable capacitance element incorporated in the control coupling element 9. The error signal controls the resonance frequency of the cavity resonator so that the difference between the amplitudes of the two third-order sensing frequency signals extracted from the cavity resonator becomes zero.

By controlling in this way, the resonance frequency fc of the cavity resonator 10 matches or becomes very close to the resonance frequency peculiar to the hydrogen atom.

Incidentally, if the level corrector 5 is further described, in the present embodiment, the relationship between the Q curve and the frequencies of the two sensing frequency signals input to the cavity resonator is as shown in FIG. That is, the frequencies of the two sensing frequency signals are set at two points with the same Q curve amplitude. Then, after the two sensing frequency signals are picked up from the cavity resonator, the two sensing frequency signals should be controlled so that the amplitude difference between the two sensing frequency signals becomes zero. Before inputting into the signal, the level corrector 5 performs the level correction in which the difference between the amplitudes of the two sensing frequency signals is awaited. But,
In the following case, since the two sensing frequency signals may have the same amplitude, the level corrector 5 may be omitted.

When setting the frequencies of two sensing frequency signals to two points where the Q curve amplitudes are equal. For example, the frequency division ratio of the variable frequency divider 4 is set to N ₁ = 20,420,751 and N ₂ = 20,390,751 to generate two primary sensing frequency signals. Alternatively, in the present embodiment, the frequency converter 11 adds +1400 MHz to each of the two sensing frequency signals, but this is + (1400M
Hz + 751Hz).

Even when the frequencies of the two sensing frequency signals are set at two points where the Q curve amplitudes are not equal, after the two sensing frequency signals are extracted from the cavity resonator and the difference in their amplitudes is detected by the amplitude detector 7. Then, when the resonance frequency of the cavity resonator matches the resonance frequency peculiar to the hydrogen atom, the control is performed by assuming that the difference in amplitude is zero. For example, if the resonance frequency of the cavity resonator matches the resonance frequency of the hydrogen atom, and the amplitude difference is detected as 0.5V by the amplitude detector 7, the error signal is generated as -0.5V. Input to the means 8. Alternatively, when the error signal generating means 8 has a predetermined difference in the amplitude, the resonance frequency fc
An error signal (a signal that the shift amount of the resonance frequency is zero) that does not change is output.

Further, the frequency converter 11 becomes unnecessary if the frequency division ratio of the variable frequency divider 4 is N ₁ = 142,042 and N ₂ = 142,039 in this embodiment. Of course, the division ratio is N ₁ = 1,420,420,751 and N ₂ ＝
Even if it is 1,420,390,751, the frequency converter 11 becomes unnecessary,
In this case, the level corrector 5 is also unnecessary. However, if the frequency division ratio is too large, the response of the control of the resonance frequency becomes slower. Therefore, in this embodiment, the frequency conversion unit 11 is inserted with the frequency division ratio reduced.

When comparing the circuit for generating the sensing frequency signal with the conventional one, the conventional sensing frequency generator shown in FIG. 3 has a reference signal generating means 19, a first PLL circuit 12, a frequency synthesizer 13, a balanced mixer 14, and a second type. The PLL circuit 15, the offset frequency oscillator 16, the switching signal generator 17, and the hybrid circuit 18 are composed of eight functional blocks, whereas in the present invention, the phase comparator 2, the voltage controlled oscillator 3 are provided.
And the variable frequency divider 4 are only composed of three functional blocks.

In the above description of the embodiments, a hydrogen maser oscillator is taken as an example for the sake of clarity, but the present invention can be applied to any oscillator including a cavity resonator.

〔The invention's effect〕

The resonance frequency control device for a cavity resonator according to the present invention includes a clock signal generator that generates a clock signal that is phase-synchronized with a signal output from an oscillator, and that outputs a reference frequency signal and a switching period signal based on the clock signal. Then 2
A variable frequency divider having various frequency division ratios, the frequency division ratio being switched by a switching period signal, a phase comparator for comparing the phase of an output signal of the variable frequency divider and a reference frequency signal, and a phase comparator of the phase comparator. By configuring a PLL circuit with a voltage controlled oscillator that receives a phase comparison output signal and generates a frequency signal and outputs the frequency signal to the variable frequency divider, two types of frequency division ratios of the variable frequency divider are switched by a switching cycle signal. , The PLL circuit alternately outputs two frequency signals corresponding to the two types of frequency division ratios and uses them as the two sensing frequency signals. Therefore, the sensing frequency signal contains a frequency component close to the oscillation frequency of the oscillator. A resonance frequency control device for a cavity resonator, which is not included, does not change the oscillation level of the oscillator, and has a simple circuit for generating a sensing frequency signal, has been realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a resonance frequency control device for a cavity resonator according to the present invention. FIG. 2 is a diagram for explaining sensing according to an embodiment of the present invention. FIG. 3 shows a block diagram of a sensing frequency generator used in a conventional frequency control device. In the figure, A and A'are sensing frequency generators, and B is
PLL circuit, 1 is a clock signal generator, 2 is a phase comparator,
3 is a voltage controlled oscillator, 4 is a variable frequency divider, 5 is a level corrector, 6 is a pickup element, 7 is an amplitude detector (detector), 8 is an error signal generating means, 9 is a frequency control coupling element, and 10 is The cavity resonator and 11 are frequency converters, respectively.

Claims (1)

(57) [Claims] 1. A cavity resonator (10) forming a part of an oscillator.
A sensing frequency generator (A) for alternately detecting two sensing frequency signals having predetermined frequencies different from each other for detecting the shift amount of the resonance frequency, and two inputs and a variable capacitance element, A frequency control coupling element (9) configured to receive the two sensing frequency signals at one of the two inputs and couple the input signals to the cavity resonator; and the cavity. A pickup element (6) for extracting two sensing frequency signals coupled to the resonator, a detector (7) for detecting the two sensing frequency signals extracted via the pickup element, and a detector for detecting the two sensing frequency signals. Generate an error signal according to the difference in amplitude between the two sensing frequency signals and send the error signal to the other of the two inputs of the frequency control coupling element At the resonant frequency control device of the cavity resonator and a color signal generating means (8), generates a clock signal synchronized in phase with the signal output of the oscillator, the reference frequency signal (f based on the clock signal
a) and a clock signal generator (1) that outputs a switching period signal (fb), and the sensing frequency generator has two types of frequency division ratios, and the frequency division ratios are generated by the switching period signal. Receiving a variable frequency divider (4) for switching the phase, a phase comparator (2) for comparing the phases of the output signal of the variable frequency divider and the reference frequency signal, and a phase comparison output signal of the phase comparator A PLL circuit (B that alternately outputs the two frequency signals, including a voltage controlled oscillator (3) that alternately generates two frequency signals corresponding to the two types of frequency division ratios and outputs the frequency signals to the variable frequency divider (B). And a resonance frequency control device for a cavity resonator.