JP2013141172A - Dual rate crystal oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dual rate crystal oscillator in which the cost can be reduced by decreasing the number of components, and floor noise can be improved.SOLUTION: Any one of coils L1, L2 for LC oscillation in an oscillation section 2 is selected by SW(1)5, a first filter (parallel connection circuit of a crystal resonator X1 and a variable coil L3) or a second filter (parallel connection circuit of a crystal resonator X2 and a variable coil L4) in a filter 3 is selected by SW(2)6, and used as a crystal filter for outputting an oscillation frequency in dual mode. A capacitor C1, C2 common to the coil L1 or L2 thus selected is used for oscillation, and a dual rate crystal oscillator which can be used as a high Q filter is obtained by the crystal resonator of first or second filter thus selected.

Description

  The present invention relates to a dual-rate crystal oscillator that oscillates two different frequencies, and more particularly to a dual-rate crystal oscillator that can reduce the number of components, reduce the cost, and improve the noise floor.

[Conventional technology]
The dual rate crystal oscillator includes a dual rate VCXO (Voltage Controlled Crystal Oscillator).
Further, the conventional dual rate VCXO is of a type that multiplies.

[Conventional Dual Rate VCXO: FIG. 8]
A conventional dual rate VCXO will be described with reference to FIG. FIG. 8 is a configuration block diagram of a conventional dual rate VCXO.
As shown in FIG. 8, the conventional dual-rate VCXO oscillates and multiplies at two frequencies, amplifies it, switches it with a switch, and outputs either frequency.

  Specifically, in the conventional dual rate VCXO, a control voltage (Vcont) is inputted from an input terminal and branched into two systems, and one side is inserted a frequency variable circuit of a resistor R21 and a diode D21, and a coil L21 is inserted. Is connected to one terminal of the crystal unit X21, the other terminal of the crystal unit X21 is connected to the input terminal of the oscillation stage / multiplication unit 11, and the output terminal of the oscillation stage / multiplication unit 11 is connected to the amplifier stage 13. The output terminal of the amplifier stage 13 is connected to the input terminal of the switch (SW) 15.

  The other of the control voltage branches is inserted with a variable frequency circuit of a resistor R22 and a diode D22, connected to one terminal of the crystal resonator X22 via the coil L22, and connected to the other terminal of the crystal resonator X22. Connected to the input terminal of the oscillation stage / multiplier 12, connected the output terminal of the oscillation stage / multiplier 12 to the input terminal of the amplifier stage 14, and connected the output terminal of the amplifier stage 14 to the input terminal of the switch (SW) 15. doing.

The output signal of the SW 15 is waveform-shaped by a waveform shaping IC (Integrated Circuit) 16 and an output signal (Out) is output.
A power supply voltage (Vcc) is applied to the oscillation stage / multiplication units 11 and 12, amplifier stages 13 and 14, SW15, and waveform shaping IC 16, and a control signal (Cont) for switching the switch is input to SW15. .
The frequency variable circuit has a configuration in which a resistor R is connected in series, a cathode of a diode D is connected to an output side of the resistor R, and an anode is grounded.

The conventional dual rate VCXO oscillates and multiplies each of the two systems, amplifies the two frequencies, and selects one of the oscillation signals by SW15 to perform waveform shaping.
Thus, since it comprises using the circuit for two frequencies, the number of parts increases and it becomes disadvantageous in terms of cost. Further, since the multiplication is performed, a loss occurs in the output, and the floor of the phase noise is not lowered.

[Related technologies]
As related prior art, Japanese Patent Laid-Open No. 10-242760, “Voltage Control Type High Frequency Oscillator” (Kyocera Corporation) [Patent Document 1], Japanese Patent Laid-Open No. 2002-217686, “Synchronous Signal Generator” (Nippon Radio) Kogyo Co., Ltd.) [Patent Document 2] and JP 2006-157077 A “Oscillator” (Nippon Denpa Kogyo Co., Ltd.) [Patent Document 3].

  In Patent Document 1, in an oscillation device, an oscillation circuit unit that outputs a primary oscillation signal, a frequency multiplication circuit that multiplies the frequency of an output signal of the oscillation circuit unit, and a filter circuit that extracts a predetermined frequency component that has been multiplied It is shown that the primary oscillation signal and the multiplied frequency component are switched and output by a switch.

  Patent Document 2 shows that in a synchronous signal generator, the output of a sine wave from a crystal oscillator is passed through the same filter as the center frequency of the oscillation frequency and converted into a pulse by a pulse converter.

  In Patent Document 3, in an oscillator, a varicap diode is interposed between a crystal resonator and a capacitor, a control voltage VC is applied to the cathode side from the outside, and an anode is grounded via a return resistor to control the oscillator. It is shown that the oscillation frequency is changed according to the voltage.

Japanese Patent Laid-Open No. 10-242760 JP 2002-217686 A JP 2006-157077 A

  However, in the conventional dual rate voltage controlled crystal oscillator, the number of parts increases, the cost increases, and the output is lost due to multiplication, so the phase noise floor (noise floor) does not decrease (is not improved). There was a problem.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dual rate crystal oscillator that can reduce the number of parts, reduce the cost, and improve the floor noise.

  The present invention for solving the problems of the conventional example is a dual rate crystal oscillator that selectively oscillates two different frequencies, and includes a first coil for oscillating the first frequency, A first coil for oscillating the first frequency, a capacitor used for oscillation in combination with the first coil or the second coil, and an oscillation unit including a transistor for oscillation, and for the first frequency A first filter having a parallel circuit of the first crystal oscillator and the first variable coil, and a second filter having a parallel circuit of the second crystal oscillator and the second variable coil for the second frequency. A first switch for selecting the first coil or the second coil in the oscillation unit according to a signal for selecting and instructing the oscillation of the first frequency or the second frequency, Frequency Or according to the second signal for selecting instructing oscillation frequency, and having a second switch for selecting the first filter or the second filter in the filter unit.

  According to the present invention, in the dual-rate crystal oscillator, a frequency variable circuit that varies the frequency of the control voltage and outputs it to the oscillation unit and the filter unit, and an amplifier stage that amplifies the oscillation frequency from the oscillation unit are provided. Features.

  The present invention is characterized in that, in the dual rate crystal oscillator described above, the capacitance of the crystal unit is canceled by adjusting the variable coil in the filter unit.

  According to the present invention, in the dual-rate crystal oscillator, in the filter unit, the first crystal oscillator is an oscillator that vibrates with a fundamental wave, and the second crystal oscillator is an oscillator that vibrates with an overtone. And

  According to the present invention, in the dual-rate crystal oscillator, in the filter unit, the electrode of the first crystal resonator and the electrode of the second crystal resonator are formed in one blank, and at a lower frequency of the two oscillation frequencies. It is characterized in that the blank part of the vibrating quartz crystal unit is thinned and the blank part of the quartz crystal unit vibrating at a high frequency is formed thick.

  According to the present invention, the oscillating unit includes a first coil for oscillating the first frequency, a second coil for oscillating the second frequency, and the first coil or the second coil. A first filter including a capacitor used for oscillation in combination and an oscillation transistor, and a filter unit including a parallel circuit of a first crystal resonator and a first variable coil for a first frequency And a second filter having a second crystal unit for the second frequency and a second filter having a parallel circuit of the second variable coil, wherein the first switch has the first frequency or the second frequency. The first coil or the second coil in the oscillating unit is selected in accordance with a signal for instructing to select oscillation, and the second switch selects the first frequency or the second frequency in accordance with the signal for instructing to select oscillation of the filter unit. At the first filter Since has a dual-rate crystal oscillator for selecting the second filter, it is possible to reduce the cost by reducing the number of parts, there is often possible effect floor noise.

It is a block diagram of the dual rate oscillator according to the embodiment of the present invention. It is a circuit diagram of this VCXO. It is a circuit diagram showing a filter with an equivalent circuit. It is a circuit diagram of a specific VCXO according to the present embodiment. It is a circuit diagram at the time of replacing a variable coil with a chip component. FIG. 6 is a cross-sectional explanatory diagram of a dual vibrator. It is a figure which shows the electrode pattern of a Dual vibrator. It is a block diagram of a conventional dual rate VCXO.

Embodiments of the present invention will be described with reference to the drawings.
[Outline of the embodiment]
In the dual rate crystal oscillator according to the embodiment of the present invention, the control voltage frequency-variable by the frequency variable circuit is input to the oscillating unit and the filter, and the first coil is used to oscillate the first frequency by the oscillating unit. Select the crystal oscillator and variable coil for the first frequency with the filter, select the second coil to oscillate the second frequency with the oscillation unit, and select the second frequency with the filter The crystal oscillator and the variable coil are selected and the oscillation frequency is output in the dual mode. The oscillation frequency is output by a capacitor common to the selected first coil or the second coil. It can be used as a high-Q filter, can reduce the cost by reducing the number of parts, and can improve floor noise because multiplication is not required.

[Dual-rate oscillator: Fig. 1]
A dual rate oscillator according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration block diagram of a dual rate oscillator according to an embodiment of the present invention.
As shown in FIG. 1, a dual rate oscillator (present oscillator) according to an embodiment of the present invention includes a frequency variable circuit 1, an oscillation unit 2, a filter 3, an amplifier stage 4, and a first switch (SW). (1)) 5 and a second switch (SW (2)) 6 are basically provided.

[Each oscillator part]
Each part of the oscillator will be specifically described.
The frequency variable circuit 1 is a circuit that varies the frequency of the control voltage signal.
The oscillating unit 2 oscillates at the frequency f1 or the frequency f2 by selecting the SW (1) 5.

The filter 3 is a filter that switches the passband according to the frequency f1 or the frequency f2 output from the oscillation unit 2 by selecting the SW (2) 6. In the claims, the filter portion is used.
The amplifier stage 4 is a circuit that amplifies the output from the filter 3.

The first switch (SW (1)) 5 switches the oscillation unit 2 to oscillate either the frequency f1 or the frequency f2, and receives a selection signal (Cont) from the outside. The
The second switch (SW (2)) 6 performs switching for allowing the filter 3 to pass either the frequency f1 or the frequency f2, and receives a selection signal (Cont) from the outside. .

  Here, SW5 and SW6 are interlocked. When SW5 selects oscillation of frequency f1, SW6 selects passing of frequency f1, and when SW5 selects oscillation of frequency f2, SW6 is The passage of frequency f2 is selected.

[The circuit of this VCXO: FIG. 2]
Next, a circuit when the present oscillator is applied to a dual rate voltage controlled crystal oscillator (present VCXO) will be described with reference to FIG. FIG. 2 is a circuit diagram of the present VCXO. The circuit diagram shown in FIG. 2 is obtained by embodying the block diagram of FIG. 1 as a voltage controlled crystal oscillator.

[Frequency variable circuit]
The frequency variable circuit 1 in FIG. 1 corresponds to a resistor R1 to which a control voltage (Vcont) is applied at one end and a diode D1 having a cathode connected to the other end of the resistor R1 and an anode grounded in FIG. .
Here, the frequency is made variable by making the resistance value of the resistor R1 variable or / and making the diode D1 the variable capacitance diode and making the capacitance variable.

[Amplifier stage, SW]
The amplifier stages 4, SW5 and SW6 in FIG. 1 correspond to the amplifier stages 4, SW5 and SW6 in FIG.
A selection signal (Cont) is input to SW5 and SW6, and a power supply voltage (Vcc) is applied.

[filter]
The filter 3 in FIG. 1 is connected to the SW 6 and the other end of the resistor R1 in FIG. 2, and corresponds to a variable coil L3 connected in parallel with the crystal resonator X1 and a variable coil L4 connected in parallel with the crystal resonator X2. ing.
In the claims, the parallel circuit of the crystal unit X1 and the variable coil L3 is referred to as a “first filter”, and the parallel circuit of the crystal unit X2 and the variable coil L4 is referred to as a “second filter”.

  Here, the crystal resonator X1 and the crystal resonator X2 vibrate at different frequencies. For example, if the crystal resonator X1 is a resonator that vibrates at the fundamental wave (f1), the crystal resonator X2 is 3. The vibrator vibrates with a double overtone (third harmonic: f2). The overtone is not limited to 3 times, and may be n times overtone such as 5 times and 7 times.

Thus, the number of parts can be reduced by using an overtone crystal resonator.
Further, when a high frequency of GHz is required, it can be dealt with by replacing the crystal filter with a SAW (Surface Acoustic Wave) filter.

The variable coils L3 and L4 are provided for canceling the capacitors in the crystal resonators X1 and X2.
When SW6 selects the A2 side, it becomes a filter for the frequency f1, and when SW6 selects the B2 side, it becomes a filter for the frequency f2.

[Oscillator]
The oscillator 2 in FIG. 1 has coils L1, L2 connected to SW5 in FIG. 2, an emitter connected to the input terminal of SW6, a collector connected to the amplifier stage 4 via a capacitor C4, and a capacitor C3. This corresponds to the transistor Q1 whose base is grounded.
The transistor Q1 is grounded at the base and can lower the phase noise floor.

The other end of the coils L1 and L2 is connected to the collector side of the transistor Q1, and one end of the capacitor C1 is connected. The other end of the capacitor C1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected. Grounded. Further, the other end of the capacitor C1 and one end of the capacitor C2 are connected to the other end of the resistor R1.
That is, the control voltage from the frequency conversion circuit is applied between the other end of the capacitor C1 and one end of the capacitor C2, and the coil L1 or coil L2 selected with the capacitors C1 and C2 is used for oscillation.

  Further, one end of a resistor R3 is connected to the base side of the transistor Q1, and the other end of the resistor R3 is grounded. Further, one end of the resistor R2 is connected to the base side of the transistor Q1, and the other end of the resistor R2 is connected to the power supply voltage (Vcc).

[Filter 3: FIG. 3]
Next, the filter 3 shown in FIGS. 1 and 2 will be described in detail. FIG. 3 is a circuit diagram showing the filter by an equivalent circuit.
As shown in the upper diagram of FIG. 3, the filter basically includes a crystal resonator X1 and a variable coil L3 connected in parallel.

The lower diagram of FIG. 3 is an equivalent circuit of the upper diagram, in which the crystal resonator X1 has a coil L11, a resistor R11, and a capacitor C11 connected in series, and the coil C0 is connected in parallel to the series connection.
Since the coil C0 formed in the crystal resonator X1 is an obstacle in the filter characteristics, a variable coil L3 for canceling the coil C0 is provided in parallel. A variable coil is desirable for adjusting the amount of cancellation.
Further, adjustment may be made by providing a capacitor C in parallel with the variable coil L3. The capacitor C may be a trimmer capacitor of a surface mount device.

  Further, the resonance frequency in the oscillating unit is obtained by changing the inductance value of the selected coil L1 or coil L2 and the capacitance values of the capacitors C1 and C2, and moving the resonance frequency with the changed LC circuit to obtain a variable amount. To. The variable amount of the resonance frequency in the oscillating unit is not affected by the vibrator in the filter.

[Specific VCXO Circuit: FIG. 4]
A specific VCXO circuit according to the present embodiment will be described with reference to FIG. FIG. 4 is a specific VCXO circuit diagram according to the present embodiment.
[Frequency variable circuit]
As shown in FIG. 4, the frequency variable circuit 1 in FIG. 1 corresponds to a parallel connection circuit of a resistor R5 and a coil L5, a parallel connection circuit of a capacitor C6 and a diode D2, and a resistor R6 and a resistor R10.

The control voltage (Vcont) is input to the filter via the resistor R10 and is input to a parallel connection circuit of the resistor R5 and the coil L5.
The parallel connection circuit of the resistor R5 and the coil L5 and the parallel connection circuit of the capacitor C6 and the diode D2 are connected in series, and the parallel connection circuit of the capacitor C6 and the diode D2 is connected between the capacitor C1 and the capacitor C2. At the same time, the resistor R6 is connected to one end, and the other end of the resistor R6 is grounded.

[Oscillator]
1 corresponds to the oscillating unit 2 in FIG. 1. The transistor Q1, the resistors R2, R3 and the capacitor C3 connected to the base side of the transistor Q1, the resistor R4 connected to the collector side of the transistor Q1, and the capacitors C1, C2,. C5, coils L1 and L2, and resistor R1 and capacitor Cd connected to the emitter side of transistor Q1.

Here, the resistor R1 and the capacitor Cd are connected in parallel, and the other end thereof is grounded (connected to GND).
One end of the capacitor C1 is connected to the collector side, the other end of the capacitor C1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to GND.
The other end of the resistor R3 and the capacitors C3 and C5 is connected to GND, and the power supply voltage (Vcc) is applied to the other end of the resistors R2 and R4.
The other ends of the coils L1 and L2 are connected to the SW (1) 5.

[filter]
Corresponding to the filter 3 in FIG. 1 are variable coils L3 and L4 connected to the SW (2) 6, crystal oscillators X1 and X2, capacitors C14, C15, C16, and C17.
Here, the crystal resonator X1 and the variable coil L3 are connected in parallel, and a parallel circuit of a capacitor C14 and a capacitor C15 is connected to the input side of the control voltage (Vcont).
Similarly, the crystal resonator X2 and the variable coil L4 are connected in parallel, and a parallel circuit of a capacitor C16 and a capacitor C17 is connected to the input side of the control voltage (Vcont).

[Amplifier stage]
The amplifier stage 4 in FIG. 1 corresponds to the transistor Q2, resistors R7 and R8 connected to the base side of the transistor Q2, resistor R9 and capacitor C7 connected to the emitter side of the transistor Q2, and the collector side of the transistor Q2 A coil L6 connected to the capacitor and capacitors C8, C9, C12 and C13.

Here, the base side of the transistor Q2 is connected to the oscillating portion via the capacitor C4, the power supply voltage is applied to the other end of the resistor R7, and the other end of the resistor R8 is grounded.
The resistor R9 and the capacitor C7 are connected in parallel and the other end is grounded.
Capacitor C8 and capacitor C9 are connected in series and are provided between the collector of transistor Q2 and the output terminal (OUT).

One end of the coil L6 is connected to the collector side of the transistor Q2, and the power supply voltage is applied to the other end of the coil L6.
One end of the capacitor C12 is connected to a point between the capacitors C8 and C9, and the other end of the capacitor C12 is grounded.
One end of the capacitor C13 is grounded, and a power supply voltage is applied to the other end of the capacitor C13.

[SW (1) 5]
The first switch (SW (1)) 5 in FIG. 1 corresponds to the SW (1) 5 and is connected to the coils L1 and L2 to select one by the selection signal (SEL). SW5 is connected to GND. The selection signal (SEL) in FIG. 4 is the same as the selection signal (Cont) in FIGS.

[SW (2) 6]
The second switch (SW (2)) 6 in FIG. 1 corresponds to the SW (2) 6 and is connected to two filters to select one by a selection signal (SEL). SW (2) 6 is connected to the emitter side of the transistor Q1.

[Operation of Circuit in FIG. 4]
In the circuit of FIG. 4, a selection signal (SEL) is input to SW5 and 6, SW1 selects one of coils L1 and L2, and SW6 selects one of two filters.
The selection by SW 5 and 6 is made in conjunction with each other. For example, when the coil L1 is selected, the parallel circuit side of the crystal unit X1 and the variable coil L3 is selected, and the coil L2 is selected. Is selected, the parallel circuit side of the crystal unit X2 and the variable coil L4 is selected.

  SW5 and 6 are selected, and a control voltage (Vcont) is input to the oscillating unit and the filter via the frequency variable circuit. By the operation of the transistor Q1 in the oscillating unit and the operation of the transistor Q2 in the amplifier stage, The oscillation frequency is output to the output terminal (OUT).

[Replacement of variable coil with chip parts: Fig. 5]
Next, a case where the variable coil L is replaced with a chip component will be described with reference to FIG. FIG. 5 is a circuit diagram when the variable coil is replaced with a chip component.
As shown in FIG. 5, the variable coil can be represented by a parallel circuit of a coil and a variable capacitor.

When the vibration frequency f is represented by a coil inductance L and a capacitance C,
f = 1 / [2π√ (LC)].
Assuming that f is constant, if L is increased, C is adjusted to be decreased, and if L is decreased, C is adjusted to be increased.

[Dual vibrator: FIG. 6]
Next, the case where the filter portion is constituted by a dual vibrator will be described with reference to FIG. FIG. 6 is a cross-sectional explanatory diagram of the dual vibrator.
As shown in FIG. 6, a support portion 22 serving as a pedestal is formed in the container 21, a part of the blank 23 is mounted on the support portion 22, fixed with a conductive adhesive 25, and the upper surface of the container 21 is It is covered with a lid 26.

  Electrodes 24 a to 24 d are formed on the front and back of the blank 23, the electrodes 24 a and 24 b face each other, the electrodes 24 c and 24 d face each other, and two vibrators (Dual vibration) Child).

By making the vibrator dual, the structure can be simplified and the size can be reduced.
In FIG. 6, the blank having a higher frequency is made thinner and the blank having a lower frequency is made thicker. That is, the blank portion (thin blank portion) sandwiched between the electrodes 24c and 24d has a high frequency, and the blank portion (thick blank portion) sandwiched between the electrodes 24a and 24b has a low frequency.

[Pattern arrangement of electrodes: FIG. 7]
An electrode pattern for the dual vibrator shown in FIG. 6 is shown in FIG. FIG. 7 is a diagram showing an electrode pattern of the dual vibrator.
As shown in FIG. 7, an electrode for external connection is formed on the bottom surface of the container 21 of the dual vibrator shown in FIG.

  As for the electrode pattern, four electrode patterns are formed at the four corners of the back surface of the container 21, the electrode X1 is connected to one vibrator, the electrode X2 is connected to another vibrator, and the electrode X0 is common to the two vibrators. In addition to this, a GND electrode (electrode for making the GND level) is formed.

[Effect of the embodiment]
According to the present oscillator, the control voltage frequency-variable by the frequency variable circuit 1 is input to the oscillating unit 2 and the filter 3, and the first coil is selected to oscillate the first frequency by the oscillating unit 2, and the filter 3, the first frequency oscillator and variable coil are selected, and the second coil is selected to oscillate the second frequency by the oscillating unit 2, and the second frequency is oscillated by the filter 3. Since the child and the variable coil are selected, the cost can be reduced by reducing the number of parts, and there is an effect that the floor noise can be improved because it is not necessary to perform multiplication.

  According to this VCXO, one of the coils L1 and L2 for causing LC oscillation in the oscillation unit 2 is selected by the SW (1) 5, and the first filter (the crystal oscillator X1 and the variable coil L3 are connected in parallel by the filter 3). Connection circuit) or second filter (parallel connection circuit of crystal resonator X2 and variable coil L4) is selected by SW (2) 6, and the oscillation frequency is output in the dual mode. The selected coil L1 Or, it can be oscillated by the capacitors C1 and C2 which are common to L2, and can be used as a high-Q filter by the selected crystal resonator, the number of parts can be reduced, the cost can be reduced, and the floor noise can be improved because no multiplication is required. There is an effect that can be done.

  The present invention is suitable for a dual-rate crystal oscillator that can reduce cost by reducing the number of parts and can improve floor noise.

  DESCRIPTION OF SYMBOLS 1 ... Frequency variable circuit, 2 ... Oscillation part, 3 ... Filter, 4 ... Amplifier stage, 5 ... 1st switch (SW (1)), 6 ... 2nd Switch (SW (2)), 11 ... Oscillation stage / multiplication unit, 12 ... Oscillation stage / multiplication unit, 13 ... Amplifier stage, 14 ... Amplifier stage, 15 ... Switch (SW) 16 ... Wave shaping IC, 21 ... Container, 22 ... Support, 23 ... Blank, 24a-24d ... Electrode, 25 ... Conductive adhesive, 26 ... Lid

Claims (5)

A dual rate crystal oscillator that selectively oscillates two different frequencies,
A first coil for oscillating a first frequency, a second coil for oscillating a second frequency, and a capacitor used for oscillation in combination with the first coil or the second coil And an oscillating unit comprising an oscillation transistor,
A first filter comprising a parallel circuit of a first crystal unit and a first variable coil for the first frequency; a second crystal unit and a second variable for the second frequency; A filter unit comprising a second filter comprising a parallel circuit of coils;
A first switch for selecting the first coil or the second coil in the oscillating unit according to a signal for selecting and instructing oscillation of the first frequency or the second frequency;
And a second switch for selecting the first filter or the second filter in the filter unit in accordance with a signal for selecting and instructing oscillation of the first frequency or the second frequency. Dual rate crystal oscillator. A frequency variable circuit that varies the frequency of the control voltage and outputs the control voltage to the oscillation unit and the filter unit;
2. The dual rate crystal oscillator according to claim 1, further comprising an amplifier stage for amplifying an oscillation frequency from the oscillation unit.   3. The dual rate crystal oscillator according to claim 1, wherein the filter unit cancels the capacitance of the crystal resonator by adjusting a variable coil.   4. The filter unit according to claim 1, wherein the first crystal oscillator is an oscillator that vibrates with a fundamental wave, and the second crystal oscillator is an oscillator that vibrates with an overtone. Dual rate crystal oscillator.   In the filter unit, the electrodes of the first crystal unit and the second crystal unit are formed on one blank, and the blank part of the crystal unit that vibrates at a lower frequency of the two oscillation frequencies is thinned. 5. The dual rate crystal oscillator according to claim 1, wherein a blank portion of a crystal resonator that vibrates at a high frequency is formed thick.

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