JPH10271001A - Oscillation controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillation controller in which C/N of a voltage controlled oscillator means is improved to correct a characteristic change due to manufacture tolerance and temperature, thereby attaining an oscillation operation suitable for the operating environment of a phase locked loop including the voltage controlled oscillator means. SOLUTION: A control section 106 gives a control signal CS to a selector 107 so as to' allow the selector 107 to give a control voltage Vc to a voltage controlled oscillator(VCO) 103 in the case of monitoring an oscillated frequency from the VCO 103 and a measurement section 105 measures the oscillated frequency of the VCO 103 at that time. Then the control section 106 recognizes the operating environment (opraating temperature) of the VCO 103 and manufacture tolerance of the VCO 103 itself based on the result FMR of the measurement by the measurement section 105 and a desired oscillating frequency and selects an optimum oscillating frequency band among pluralities of the oscillating frequency bands of the VCO 103 and gives a control signal CB to the VCO 103 so as to set the selected oscillating frequency band to the VCO 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillation control device provided with a voltage controlled oscillator, and more particularly, to an improvement in the C / N ratio of the voltage controlled oscillator, and a variation in the characteristics of the voltage controlled oscillator due to manufacturing variations and temperature. The present invention relates to an oscillation control device that enables oscillation operation suitable for a use environment by correcting the above.

[0002]

2. Description of the Related Art In recent years, with the increasing complexity and versatility of electronic equipment, the phase used in frequency synthesizers, servo system speed control, detection / demodulation, etc. in electronic equipment used in various fields. Synchronous loop (hereinafter, PLL;
A phase-locked loop (circuit) is also required to be usable in an oscillation frequency band over a wide range.

For example, at present, the CD-ROM market is proceeding to higher-speed reproduction, and a signal processing LSI for CD-ROM is being used.
In this case, there is a demand for a device capable of handling an ultra-high speed n-times speed for realizing higher-speed reproduction, for example, a 16-times speed or the like. In a signal processing LSI for CD-ROM, a PLL circuit is internally provided as a means for obtaining a required oscillation frequency. However, in order to realize high-speed reproduction, a voltage-controlled oscillator (hereinafter, referred to as a high-frequency oscillator having a high maximum oscillation frequency). , VCO; Voltage
Controlled Oscillator).

In this case, the oscillation frequency f required at the time of n times speed is
n can be obtained by the following equation.

Fn = 4.3218 × 6 × n [MHz] (1) That is, in 1 × speed reproduction for the purpose of audio reproduction, P
The oscillation frequency required for the VCO inside the LL circuit is about 25
[MHz], and an oscillation frequency required for signal processing for a 16-times CD-ROM is about 415 [MHz]. In other words, in order to operate at 1 × to 16 × speed, when the control voltage of the VCO is changed between the power supply potential Vss and Vdd, a signal for changing the oscillation frequency from 25 [MHz] to 415 [MHz] is output. Must be configured to

FIG. 4 shows a control voltage Vc of a VCO in a PLL circuit in an oscillation control device having a PLL circuit.
The characteristics of the oscillation frequency f [MHz] with respect to [V] are shown.
As shown in the figure, when the power supply potential Vdd = 5 [V], the oscillation frequency F1 required at 1 × speed is 25 [MH].
z], the gradient Δfa / ΔVc in the characteristic of the oscillation frequency fa with respect to the control voltage Vc is equal to the slope of the oscillation frequency fb with respect to the control voltage Vc when outputting the oscillation frequency F16 = 415 [MHz] required at 16 × speed. As compared with the gradient Δfb / ΔVc in the characteristic,

[0006]

## EQU2 ## There is a relationship of Δfa / ΔVc <Δfb / ΔVc (2), and as the oscillation frequency required for the VCO becomes wider, the gradient Δf / ΔVc in the characteristic of the oscillation frequency f with respect to the control voltage Vc becomes steeper, The frequency change amount Δf with respect to the minute control voltage change ΔVc increases.
As a result, minute substrate noise cannot be ignored, and even if the designer reduces the noise, the playability of the electronic device will not be improved.

In the current process, the power supply potential Vd
Although d = 3.3 [V] is becoming mainstream, in this case, similarly, as shown in FIG. 4, the control voltage for outputting the oscillation frequency F1 = 25 [MHz] required for 1 × speed is also used. Gradient Δfc in characteristics of oscillation frequency fc with respect to Vc
/ ΔVc is the oscillation frequency F16 =
Compared with the gradient Δfd / ΔVc in the characteristic of the oscillation frequency fd with respect to the control voltage Vc when outputting 415 [MHz],

[0008]

## EQU3 ## There is a relationship of Δfc / ΔVc <Δfd / ΔVc (3), and the gradient is steeper than when the power supply potential Vdd = 5 [V]. in this way,
The situation where small substrate noise cannot be ignored and the playability of electronic devices does not improve even if the noise is reduced will become more remarkable because the power supply potential decreases as the manufacturing process progresses in the future. it is conceivable that.

The VCO has a characteristic change due to a temperature change, and the lower limit and the upper limit of the recommended operating temperature of the signal processing LSI greatly fluctuate with respect to the oscillation frequency at normal temperature (25 ° C.). In addition to the characteristic deterioration due to temperature as described above, when considering the manufacturing variation of the VCO, in order to obtain the oscillation frequency under the most critical conditions, aim for a higher oscillation frequency band for the VCO alone. Need to design. Therefore, the gradient of the control voltage vs. oscillation frequency characteristic of the VCO becomes steeper,
C / N deteriorates.

[0010]

As described above, in the conventional oscillation control device, the VC is required to meet the recent needs of using the oscillation frequency in a wide frequency band.
When the oscillation frequency of O is wide, the gradient in the control voltage vs. oscillation frequency characteristic is steep, and the amount of frequency change with respect to a minute change in the control voltage becomes large. As a result, minute substrate noise cannot be ignored, and the playability of the electronic device is not improved even if the designer reduces the noise.

In addition, the above situation is considered to become more remarkable because the power supply potential becomes lower as the manufacturing process progresses in the future, and furthermore, it is necessary to consider the characteristic deterioration and the manufacturing variation due to the temperature of the VCO. In such a case, it is necessary to design for a higher oscillation frequency band, so that the gradient of the control voltage vs. oscillation frequency characteristic of the VCO becomes steeper, and the C / N deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and in an oscillation control device provided with a voltage-controlled oscillation means, the C / N of the voltage-controlled oscillation means is improved, and the production control and the temperature are controlled. An oscillation control device that corrects a characteristic change, enables an oscillation operation suitable for a use environment of a phase locked loop including a voltage controlled oscillator, and further improves the playability of an electronic device to which the phase locked loop is applied. It is intended to provide.

[0013]

In order to solve the above-mentioned problems, an oscillation control apparatus according to the present invention is characterized in that an oscillation frequency is controlled by a control voltage and includes a plurality of oscillation frequency bands having a partially overlapping oscillation frequency band. Means, measuring means for measuring the oscillation frequency of the voltage-controlled oscillating means, and control means for selecting and setting the oscillation frequency band of the voltage-controlled oscillating means based on the measurement result and the desired oscillation frequency by the measuring means. It is provided with.

Further, the oscillation control device of the present invention includes a frequency dividing means for dividing an output signal of the voltage controlled oscillation means at a set frequency dividing ratio, wherein the control means operates the measurement result by the measuring means. And an oscillation frequency band of the voltage controlled oscillator is selected and set based on a desired oscillation frequency, and a frequency division ratio of the frequency divider is set.

Further, the oscillation control device of the present invention includes a selection means for selecting a loop signal of a phase locked loop including the voltage controlled oscillation means and a predetermined potential, and setting the selected signal as a control voltage to the voltage controlled oscillation means. The control means obtains a measurement result by the measurement means when a control voltage of a predetermined potential is supplied from the selection means to the voltage controlled oscillation means.

The oscillation control device according to the present invention further comprises a frequency dividing means for dividing an output signal of the voltage controlled oscillating means at a set division ratio, and a loop signal of a phase locked loop including the voltage controlled oscillating means. And selecting means for selecting a predetermined potential and setting the control voltage to the voltage-controlled oscillating means, wherein the control means, when changing the desired oscillation frequency,
The selection control of the selection unit is performed, the control voltage of the predetermined potential is supplied to the voltage control oscillation unit, a measurement result by the measurement unit is obtained, and the voltage control is performed based on the measurement result and the desired oscillation frequency. The oscillation frequency band of the oscillation means is selected and set, and the frequency division ratio of the frequency division means is set.

Also, in the oscillation control device according to the present invention, the control means may select an oscillation frequency band of the voltage controlled oscillation means by selecting a frequency margin higher than a frequency of the measurement result in the oscillation frequency band or the measurement margin. This is performed in consideration of a frequency margin lower than the resultant frequency.

In the oscillation control apparatus according to the present invention, the predetermined potential supplied to the selection means is a first reference potential for obtaining a maximum oscillation frequency at which the voltage controlled oscillation means can oscillate.

Further, in the oscillation control device according to the present invention, the predetermined potential supplied to the selection means is a second reference potential for obtaining a minimum oscillation frequency at which the voltage controlled oscillation means can oscillate.

In the oscillation control apparatus of the present invention, the voltage controlled oscillation means has a plurality of partially overlapped oscillation frequency bands, so that the oscillation frequency of the voltage controlled oscillation means can be used in a wide frequency band. In addition, the slope of the control voltage versus oscillation frequency characteristic in each oscillation frequency band can be reduced, and the amount of frequency change with respect to minute control voltage change can be suppressed, so that minute substrate noise can be ignored. It is possible to improve the playability of the electronic device to which the voltage-controlled oscillation means or the phase-locked loop including the voltage-controlled oscillation means is applied.

Further, the oscillation control device of the present invention recognizes the use environment and the manufacturing variation of the voltage controlled oscillator based on the measurement result of the oscillation frequency of the voltage controlled oscillator by the measuring unit and the desired oscillation frequency. Since the oscillation frequency band of the oscillating means and the dividing ratio of the dividing means are selectively set,
By correcting the manufacturing variation of the voltage controlled oscillating means and the characteristic change due to the temperature, the oscillation operation suitable for the use environment of the voltage controlled oscillating means or the phase locked loop including the voltage controlled oscillating means is enabled. N can be improved.

Further, in the oscillation control device of the present invention, when changing the desired oscillation frequency, selection control of the selection means is performed to supply a control voltage of a predetermined potential to the voltage control oscillation means,
Obtaining a measurement result by the measuring means at that time, based on the measurement result and a desired oscillation frequency, recognizes a use environment and manufacturing variations of the voltage controlled oscillating means itself, and oscillates an oscillation frequency band and a frequency dividing means of the voltage controlled oscillating means. Since the frequency division ratio is selected and set, it is possible to correct the manufacturing variation of the voltage controlled oscillator and the characteristic change due to the temperature, and to improve the C / N of the voltage controlled oscillator.

Further, in the oscillation control device according to the present invention, the predetermined potential supplied to the selection means is set to the first reference potential for obtaining the maximum oscillation frequency at which the voltage controlled oscillation means can oscillate, or Second to obtain the lowest possible oscillation frequency
The selection of the oscillation frequency band of the voltage-controlled oscillation means by the control means is performed, for example, by selecting a frequency margin higher than the frequency of the measurement result (minimum oscillation frequency) or the frequency of the measurement result (maximum oscillation) in the oscillation frequency band. Since the control is performed in consideration of the frequency margin lower than the frequency, the selection control can be performed with a simple control sequence.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an oscillation control device according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a basic configuration diagram of an oscillation control device according to one embodiment of the present invention. In the figure, the oscillation control device of the present embodiment includes a phase comparator 101, a low-pass filter (hereinafter, LP).
F; a Low Pass Filter) 102, a voltage controlled oscillator (VCO) 103, a frequency divider 104, a measuring unit 105, a control unit 106, and a selector 107.

Phase comparator 101, LPF 102, VCO
103, a frequency divider 104 and a selector 107 form a phase locked loop (PLL circuit), and an input signal V
i, the input signal V
An error voltage corresponding to i and the frequency and phase difference of the internal clock ICK output from the frequency divider 104 is generated. The high-frequency component of the error voltage is removed by the LPF 102 and becomes the control voltage Vc of the VCO 103 via the selector 107. The VCO 103 is controlled so that the frequency difference between the input signal Vi and the internal clock ICK becomes small. After repeating this operation, the frequency of the VCO 103 matches the frequency of the input signal Vi, and a lock state is established.

The basic operation of the phase locked loop has been described above. The first feature of the oscillation control device of this embodiment is that
O103 is provided with a plurality of oscillation frequency bands having a partial overlap, one oscillation frequency band can be selectively set by a control signal CB from the control unit 106, and the frequency division ratio of the frequency divider 104 is also Control signal CD from control unit 106
Can be selected and set.

A second feature of the oscillation control apparatus of the present embodiment is that a selector 107 is provided at the input stage of the VCO 103, and the VCO 103
A configuration is such that a loop signal (output of LPF 102) of a phase locked loop or a predetermined potential can be selectively supplied as the control voltage Vc of 103, and for example, a first power supply potential Vss or a second power supply potential Vdd is applied as the predetermined potential This means that the measurement unit 105 can measure the maximum oscillation frequency or the minimum oscillation frequency of the VCO 103, respectively.

Next, FIG. 2 shows a specific configuration diagram of the oscillation control device of this embodiment. The oscillation control device of the present embodiment shown in FIG. 2 is a CD-RO which has been exemplified in the description of the prior art.
This is applied to a signal processing LSI for M. The phase comparator 101, the LPF 102, the VCO 103 in FIG.
The frequency divider 104, the measuring unit 105, and the selector 107 are
-It is realized by being configured inside the signal processing LSI 200 for ROM (however, a part of the LPF 102 is externally provided), and the control unit 106 in FIG.
0.

That is, the signal processing LSI 200 includes the phase comparator 101 as the phase comparator 201 and the VCO 103 as the VCO
203, the frequency divider 104 to the frequency divider 204, the measuring unit 10
5 to the frequency measuring device 205 and the selector 107 to the selector 2
07, and prescaler frequency dividers 221 and 222 are provided before the phase comparator 201.

The LPF 102 is a signal processing LSI 2
The active filter includes an external resistor 212, 213, and 214, a capacitive element 215, and an operational amplifier 211 inside the signal processing LSI 200. That is, the output of the phase comparator 201 is connected to one end of the resistor 212 via an external terminal, the other end of the resistor 212 is connected to one end of the resistor 213, and the other end of the resistor 213 is connected to one end of the capacitor 215. , The other end of the capacitive element 215 and the resistor 2
14 is connected, the other end of the resistor 214 is connected to the second power supply potential Vdd, the connection point of the resistors 212 and 213 is set as an input of the operational amplifier 211 via an external terminal, and the output of the operational amplifier 211 is connected to the external. In this configuration, the terminal is connected to a connection point between the capacitor 215 and the resistor 214 via a terminal.

The CPU 250 sends a signal processing LSI 2
As the control signals supplied to 00, a control signal CS for controlling selection switching of the selector 207, a control signal CB for selectively setting the oscillation frequency band of the VCO 203, and a frequency division ratio 1 / K of the frequency divider 204 are selectively set. Control signals CD, and these control signals are control codes of control commands of the signal processing LSI 200 issued by the CPU 250.
Further, the measurement result FMR of the frequency measuring device 205 is supplied from the signal processing LSI 200 to the CPU 250. In the figure, Vss is a first power supply potential (ground potential GN).
D), Vdd is a second power supply potential.

A signal whose frequency fi is given by the following equation is supplied to the input signal Vi. The frequency division ratio of the prescaler frequency divider 221 is 1/32, and the frequency ratio of the prescaler frequency divider 222 is 1/98. Is set.

[Mathematical formula-see original document] fi = 16.9344 * 2 / n [MHz] (4) (8.4672 [MHz] when n = 1, 135.4752 [MHz] when n = 16) Also, the frequency divider 204 Is given by K = 1, the frequency of the internal clock ICK is 25.9308 [MHz] when n = 1, and 41.49 when n = 16.
4.8928 [MHz].

In the oscillation control device of this embodiment, the VCO 20
3 is a band A having a partial overlap as shown in FIG.
It has four oscillation frequency bands of band B, band C and band D. Here, one of the oscillation frequency bands of the VCO 203 is selected and set by the control signal CB from the CPU 250 as the oscillation frequency bands of the band A, the band B, the band C, and the band D. The characteristic drawn by the solid line in FIG. 3 is the characteristic of the control voltage versus the oscillation frequency at the second power supply potential Vdd = 5 [V], and the characteristic drawn by the dotted line is the second power supply potential Vd.
This is a characteristic of the control voltage versus the oscillation frequency when d = 3.3 [V].

Also, the frequency division ratio 1 / K in the frequency divider 204
Can be selected and set as K = 1, 2, 4,... By the control signal CD from the CPU 250.
In addition to the selection of the oscillation frequency band 203, more detailed settings are possible for the PLL circuit.

The selection switching in the selector 207 is controlled by a control signal CS from the CPU 250. By the selection switching, the control signal Vc of the VCO 203 is used as the loop signal (output of the LPF) of the phase locked loop or the first signal. The power supply potential Vss can be selectively supplied. Here, when the control voltage Vc of the VCO 203 is set to the first power supply potential Vss (ground potential GND) by the control signal CS, the frequency measuring device 205 uses the VCO 20
The maximum oscillating frequency at which 3 can oscillate is measured. When the first power supply potential Vss, which is one input of the selector 207, is changed to the second power supply potential Vdd, the minimum oscillation frequency at which the VCO 203 can oscillate is measured by the frequency measurement device 205. The Rukoto.

Next, the selection setting of the oscillation frequency band of the VCO 203 and the selection setting of the frequency division ratio of the frequency divider 204, which are performed in the oscillation control device of the present embodiment, will be described. These selection settings are made by a control command issued by the CPU 250 when the double speed setting of the CD-ROM is switched.

First, the CPU 250 controls the control signal CS to monitor the maximum oscillation frequency of the VCO 203.
Controls the selection of the selector 207 by the VCO 20
The first power supply potential Vss is given as the control voltage Vc of No. 3. At this time, the maximum oscillation frequency of the VCO 103 is measured by the frequency measuring device 207, and the measurement result FMR is CP.
Sent to U250.

Next, the CPU 250 controls the frequency
Based on the measurement result FMR of No. 7, a change in temperature characteristics due to a use environment (use temperature or the like) or a manufacturing variation of the VCO 203 is recognized, and a desired oscillation frequency of an electronic device to which a PLL circuit is applied at that time is covered. One of the optimum oscillation frequency bands for the characteristic change and individual variation due to the use temperature is selected from the oscillation frequency bands of the band A, the band B, the band C, and the band D provided in the VCO 203, and the control signal C
B controls the VCO 203 to the selected oscillation frequency band.

Here, the measurement result FMR of the oscillation frequency is 2
In the case of being covered by one oscillation frequency band, for each oscillation frequency band, a comparison is made between how much a frequency margin lower than the frequency (maximum oscillation frequency) of the measurement result FMR, and the frequency margin is large. Choose one. Note that the VCO is
In the case where the minimum oscillation frequency of 203 is measured, the measurement result F is obtained for each oscillation frequency band.
What is necessary is just to compare the frequency margin higher than the frequency of the MR (minimum oscillation frequency) and select the one with the larger frequency margin.

The frequency division ratio 1 / K of the frequency divider 204 is also controlled by the control signal CD so that the internal clock ICK has a desired oscillation frequency, independently of the selection of the oscillation frequency band of the VCO 203. .. Are selected and set.

As described above, in the oscillation control apparatus of the present embodiment, the VCO 203 has the oscillation frequency bands of the bands A, B, C, and D having a partial overlap. Can be used in a wide frequency band, but band A, band B, band C and band D
Since the gradient of the control voltage vs. oscillation frequency characteristic in each of the oscillation frequency bands is small, the amount of frequency change with respect to a minute change in the control voltage can be suppressed, whereby minute substrate noise can be ignored. Playability of an electronic device to which the circuit is applied can be improved.

Further, in the oscillation control apparatus of the present embodiment, the operating environment (operating temperature, etc.) and the VCO2 based on the oscillation frequency measurement result FMR of the VCO 203 by the frequency measuring device 207.
03 recognizes the manufacturing variation of itself and covers the desired oscillation frequency of the electronic device to which the PLL circuit is applied at that time,
In addition, the optimum oscillation frequency band is selected and set for the characteristic change and individual variation due to the use temperature of the frequency divider 204, and the frequency division ratio of the frequency divider 204 is selected and set. Is corrected to enable an oscillation operation suitable for the usage environment of the PLL circuit.
03 C / N can be improved.

[0043]

As described above, according to the oscillation control apparatus of the present invention, it is possible to improve the C / N of the voltage controlled oscillator, correct the manufacturing variation of the voltage controlled oscillator, and change the characteristic due to temperature. Oscillation operation suitable for the use environment of the voltage-controlled oscillating means or the phase-locked loop including the voltage-controlled oscillating means can be performed, and further, the playability of the applied electronic device can be improved.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of an oscillation control device according to an embodiment of the present invention.

FIG. 2 is a specific configuration diagram of an oscillation control device according to an embodiment.

FIG. 3 is an explanatory diagram illustrating characteristics of a control voltage of a VCO versus an oscillation frequency in the oscillation control device of the embodiment.

FIG. 4 is an explanatory diagram showing characteristics of a control voltage versus an oscillation frequency of a conventional VCO.

[Explanation of symbols]

101: phase comparator, 102: low-pass filter (LP
F; Low Pass Filter; 103 ... Voltage Controlled Oscillator (VCO; Voltage Control)
led Oscillator), 104: frequency divider, 1
05: measuring unit, 106: control unit, 107: selector, 20
0: Signal processing LSI for CD-ROM, 201: Phase comparator, 212, 213, 214: Resistance, 215: Capacitance element, 211: Operational amplifier, 203: VCO, 204: Frequency divider, 205: Frequency measuring instrument , 207 ... selector, 22
1,222: Prescaler frequency divider, 250: CPU (microprocessor), Vi: Input signal, Vc: Control voltage, ICK: Internal clock, CS, CB, CD: Control signal, FMR: Measurement result of frequency measuring device 205 , Vss ...
First power supply potential (ground potential), Vdd... Second power supply potential.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Mamoru Kudo 134 Kobe-cho, Hodogaya-ku, Yokohama, Kanagawa Prefecture Sony LSI Design Inc.

Claims (7)

[Claims] An oscillation frequency is controlled by a control voltage,
Voltage-controlled oscillating means having a plurality of oscillation frequency bands having partial overlap, measuring means for measuring the oscillating frequency of the voltage-controlled oscillating means, and the voltage based on the measurement result and the desired oscillating frequency by the measuring means A control means for selecting and setting an oscillation frequency band of the control oscillation means. 2. A frequency dividing means for dividing an output signal of the voltage controlled oscillating means at a set frequency dividing ratio, wherein the control means is configured to divide the output signal based on a result of measurement by the measuring means and a desired oscillation frequency. 2. The oscillation control device according to claim 1, wherein an oscillation frequency band of said voltage controlled oscillation means is selected and set, and a frequency division ratio of said frequency dividing means is set. 3. A control circuit for selecting a loop signal and a predetermined potential of a phase-locked loop including the voltage-controlled oscillating means and using the selected signal as a control voltage for the voltage-controlled oscillating means. 2. The oscillation control device according to claim 1, wherein a measurement result obtained by said measurement means is obtained when a control voltage of a predetermined potential is supplied from said selection means to said voltage controlled oscillation means. 4. A frequency dividing means for dividing an output signal of said voltage controlled oscillating means at a set frequency dividing ratio, a loop signal of a phase locked loop including said voltage controlled oscillating means and a predetermined potential are selected. Selecting means for setting a control voltage to the voltage-controlled oscillating means, wherein the control means, when changing the desired oscillation frequency, performs selection control of the selecting means to control the predetermined potential control voltage. Is supplied to the voltage-controlled oscillating means, a measurement result by the measuring means is obtained, and based on the measurement result and the desired oscillation frequency, an oscillation frequency band of the voltage-controlled oscillating means is selected and set. 2. The oscillation control device according to claim 1, wherein a frequency dividing ratio of the frequency dividing means is set. 5. The control means selects the oscillation frequency band of the voltage controlled oscillation means by selecting a frequency margin higher than the frequency of the measurement result or a frequency lower than the frequency of the measurement result in the oscillation frequency band. 2. The oscillation control device according to claim 1, wherein the oscillation control is performed in consideration of a margin. 6. The predetermined potential supplied to the selection means,
The oscillation control device according to claim 3, wherein the voltage control oscillation means is a first reference potential for obtaining a maximum oscillation frequency at which oscillation is possible. 7. The predetermined potential supplied to the selection means,
4. The oscillation control device according to claim 3, wherein the voltage control oscillation means is a second reference potential for obtaining a minimum oscillation frequency at which oscillation is possible.