JP2001036344A - Crystal oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce worsening of phase noise characteristics due to mechanical vibrations. SOLUTION: A 1st crystal vibrator 1a and a 2nd crystal vibrator 2 having a same characteristics are mounted closely in the same direction, an amplifier 3 and an inverter 4 inversely amplify the output of the 2nd crystal vibrator 2 and its output signal controls a VCXO (voltage-controlled crystal vibrator) 1 consisting of the 1st crystal vibrator 1a. Thus, an inverted voltage in response to vibration generated from the 2nd crystal vibrator 2 through a piezoelectric effect by mechanical vibrations exerted to the 2nd crystal vibrator 2 is used to control the oscillating frequency of the VCXO consisting of the 1st crystal vibrator 1a. Thus, the fluctuations in the oscillating frequency resulting from the mechanical vibration exerted to the 1st crystal vibrator 1a is cancelled and a stable oscillating frequency is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator, and more particularly, to a crystal oscillator having improved oscillation frequency fluctuation due to mechanical vibration.

[0002]

2. Description of the Related Art As is well known, a crystal oscillator using a crystal oscillator has been widely used because of its extremely high frequency stability against temperature and aging and excellent phase noise in the vicinity. ing. However, the quartz oscillator has a problem that its oscillation frequency fluctuates when it receives mechanical vibration from the outside. FIG. 4 shows a frequency spectrum due to mechanical vibration. As shown in the figure, assuming that the oscillation frequency is f0 and the frequency of the external vibration is f1, Δf = f1 (frequency of the external vibration) around the oscillation frequency f0
F0 ± f1, f0 ± 2f1,..., F
An infinite sideband of 0 ± nf1 (n = 1, 2,...) Is generated, and it is in a state in which it is just subjected to FM weighting. As a result, the phase noise characteristic of the oscillation output is degraded, causing a deterioration in the performance of the entire system using the crystal oscillator.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a crystal oscillator in which deterioration of phase noise due to mechanical vibration is reduced.

[0004]

According to the present invention, a first crystal unit and a second crystal unit having the same characteristics are provided.
Are mounted in close proximity in the same direction, the output of the second crystal resonator is inverted and amplified, and the output signal is used to output a VCXO (Voltage C) composed of the first crystal resonator.
By controlling an ontrolled crystal oscillator, a variation in oscillation frequency due to mechanical vibration applied to the first crystal resonator is canceled.

[0005] The present invention provides a crystal oscillator in which the first crystal unit and the second crystal unit are mounted in parallel on one side of a substrate.

[0006] The crystal oscillator comprises a first crystal unit and a second crystal unit attached to the front and back of a substrate.

[0007] A crystal oscillator is provided in which the first crystal unit and the second crystal unit are housed in the same case.

[0008]

As described above, in a crystal oscillator according to the present invention, a first crystal unit and a second crystal unit having the same characteristics are mounted close to each other in the same direction. The output of the crystal unit is inverted and amplified, and the output signal is used to output a VCXO (Voltage) constituted by the first crystal unit.
Controlled Crystal Oscillator) is controlled, so that a VCXO composed of the first crystal oscillator is formed by inverting the voltage corresponding to the vibration generated by the piezoelectric effect due to the mechanical vibration applied to the second crystal oscillator. Can be controlled, and fluctuation of the oscillation frequency due to mechanical vibration applied to the first crystal resonator can be canceled.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a crystal oscillator according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic block diagram showing one embodiment of a crystal oscillator according to the present invention. In the figure, 1
a is a first crystal unit constituting the VCXO1, 2 is a second crystal unit for detecting mechanical vibration, 3 is a vibration signal generated by a piezoelectric effect due to mechanical vibration from the second crystal unit. Is an amplifier that amplifies the vibration signal to a predetermined level, and an inverter 4 inverts the amplified vibration signal. In the present embodiment, the amplifier 3 and the inverter 4 are divided, but it is a well-known technique that it can be integrated as an inverting amplifier. Whether the level of the amplifier 3 is adjustable or fixed is a matter of design.

Next, the operation of the above configuration will be described. FIG. 2 shows an example of a vibration signal having a frequency f1 generated by the piezoelectric effect of the second crystal resonator due to mechanical vibration. In this example, the vibration signal is a sine wave for simplicity. The vibration signal of the frequency f1 shown in FIG. Since the frequency f0 of the VCXO1 formed by the element 1a is controlled, the fluctuation of the frequency f0 due to the mechanical vibration of the frequency f1 applied to the first crystal resonator 1 (the FM modulation wave shown in FIG. = Sidebands generated at intervals of f1), and a stable oscillation frequency (f0) can be obtained.

FIG. 3 is a view showing an embodiment of a method for mounting two crystal units constituting a crystal oscillator according to the present invention. In the embodiment shown in FIG. 3A, the substrate is mounted close to the same surface of the substrate in the same direction so that external vibrations are transmitted in the same manner. In the embodiment of FIG. 3- (B), it is attached to the front and back of the substrate in the same direction,
Vibration from the outside is transmitted in the same manner, and the size is reduced. In the embodiment shown in FIG. 3C, the two crystal units are housed in the same case so that external vibrations are transmitted in the same manner.

[0012]

As described above, according to the crystal oscillator of the present invention, the first and second crystal units having the same characteristics are mounted close to each other in the same direction.
The output of the crystal unit is inverted and amplified, and the output signal is used to output a VCXO (Volta) composed of the first crystal unit.
(Ge Controlled Crystal Oscillator) is controlled, so that a voltage corresponding to vibration generated by a piezoelectric effect due to mechanical vibration applied to the second crystal resonator is inverted to constitute the first crystal resonator. The oscillation frequency of the VCXO can be controlled, and the fluctuation of the oscillation frequency due to the mechanical vibration applied to the first crystal resonator can be canceled.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a crystal oscillator according to the present invention.

FIG. 2 is a diagram for explaining a crystal oscillator according to the present invention, and is a waveform diagram showing an example of a vibration signal having a frequency f1 generated by a piezoelectric effect of a second crystal resonator due to mechanical vibration.

FIG. 3 is a layout view of a crystal oscillator showing another embodiment of the crystal oscillator according to the present invention.

FIG. 4 is a frequency spectrum diagram for explaining a problem of the conventional crystal oscillator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 VCXO 1a 1st crystal oscillator 2 2nd crystal oscillator 3 Amplifier 4 Inverter

Claims (4)

[Claims] 1. A first crystal unit and a second crystal unit having the same characteristics are mounted close to each other in the same direction, and the output of the second crystal unit is inverted and amplified and output. VCXO (Voltage) composed of the first crystal unit according to the output signal
A crystal oscillator characterized in that fluctuations in oscillation frequency due to mechanical vibration applied to the first crystal resonator are canceled by controlling a controlled crystal oscillator (Controlled Crystal Oscillator). 2. The crystal oscillator according to claim 1, wherein said first crystal oscillator and said second crystal oscillator are mounted in parallel on one side of a substrate. 3. The crystal oscillator according to claim 1, wherein said first crystal unit and said second crystal unit are mounted on the front and back of a substrate. 4. The crystal oscillator according to claim 1, wherein said first crystal unit and said second crystal unit are housed in the same case.