JP3923263B2 - Composite crystal oscillator and overtone crystal oscillator using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composite crystal resonator and an overtone crystal oscillator using the composite crystal resonator (referred to as an overtone oscillator) in the industrial technical field, and in particular, an SC including an oscillator and a resonator forming an oscillation circuit and a filter. The present invention relates to a cut composite crystal resonator.
[0002]
[Prior art]
BACKGROUND OF THE INVENTION A crystal resonator is well known as a frequency and time reference element, and is incorporated in, for example, a Colpitts-type crystal oscillator and incorporated in various electronic devices including communication devices. In recent years, the frequency has been increased by digital communication and the like, and for example, an overtone oscillator using overtone vibration with respect to fundamental wave vibration of a crystal resonator is employed.
[0003]
FIG. 3 is a circuit diagram of an overtone oscillator for explaining a conventional example.
The overtone oscillator includes an oscillator 1 made of a crystal resonator used as an inductor component, a split capacitor 3 (ab) that forms a Colpitts-type resonance circuit 2 and an amplifier such as a transistor 4, for example. The crystal resonator is formed with excitation electrodes 6 (ab) and extraction electrodes 7 (ab) facing both main surfaces of the crystal piece 5 and held in a sealed container having terminals (not shown).
[0004]
However, the crystal resonator as the oscillator 1 operates with an odd-order overtone vibration with respect to the fundamental vibration (referred to as an overtone oscillator 1). The vibration frequency (resonance frequency) due to overtone vibration is a frequency that is approximately an integral multiple of the fundamental vibration (referred to as overtone frequency).
[0005]
Normally, overtone vibration is inferior in vibration strength to fundamental wave vibration, and crystal impedance (CI) is small. For this reason, for example, an inductor (not shown) is connected in parallel to the capacitor 3b on the ground side of the dividing capacitor 3 (ab), and an overtone frequency of, for example, a fifth harmonic with respect to the fundamental vibration frequency is selected. Further, without using the inductor, the shape of the crystal piece 5 and the electrode structure for exciting the crystal piece 5 increase the intensity of overtone vibration with respect to the fundamental vibration, thereby reducing CI. Alternatively, the overtone frequency is selected according to the frequency characteristic of the negative resistance on the circuit side as viewed from the crystal resonator.
[0006]
In this example, a crystal resonator as the resonator 8 is connected between the midpoint (connection point) of the split capacitor 3 (ab) of the Colpitts type and the emitter of the transistor 4. Similar to the overtone resonator 1, the resonator 8 operates with overtone vibration relative to the fundamental vibration (referred to as an overtone resonator 8). In this case, the overtone resonator 8 is inserted into an oscillation closed loop composed of the resonance circuit 2 and the oscillation amplifier. The crystal resonator as the overtone resonator 8 has a configuration in which the excitation electrode 6 (ab) and the extraction electrode 7 (ab) are provided on the crystal piece 5 and sealed in a sealed container as described above.
[0007]
Here, each of the quartz vibrators as the overtone oscillator 1 and the resonator 8 is composed of an SC-cut crystal piece 5. In the figure, reference numeral 9 (abc) is a bias resistor, 10 is an oscillation frequency adjusting capacitor, Vc is a power source provided on the collector side, and Vo is an output derived from the emitter side.
[0008]
In such a case, the oscillation frequency of the crystal oscillator substantially matches the overtone frequency of the overtone oscillator 1. However, strictly speaking, it depends on a series equivalent capacity (so-called load capacity) on the circuit side as viewed from the overtone oscillator 1. In this example, since the overtone resonator 8 as a crystal resonator is connected to the oscillation closed loop including the resonance circuit 2 and the oscillation amplifier, the oscillation frequency band is further narrowed. However, the resonance frequency of the overtone resonator 8 is set to an oscillation frequency depending on the overtone resonator 1.
[0009]
In short, the overtone resonator 8 functions as a filter that allows passage of only an overtone frequency that is approximately five times that of the crystal resonator serving as the oscillation frequency. Therefore, the B mode (thickness sliding vibration mode, displacement in the Z′-axis direction) generated close to the C mode (thickness-slip vibration mode, displacement in the X-axis direction), which is a vibration mode peculiar to SC cut, is cut off. This prevents spurious oscillation.
[0010]
The SC-cut crystal piece 5 (quartz crystal resonator) vibrates in a thickness-slip vibration state, for example, in the same manner as an AT-cut crystal resonator that is generally used frequently, and these are inversely proportional to the thickness of the crystal piece 5. The smaller the thickness, the higher the vibration frequency (resonance frequency). And since it is excellent in a thermal shock characteristic compared with AT cut, it is employ | adopted for the crystal oscillator for high stability using a thermostat, for example.
[0011]
[Problems to be solved by the invention]
(Problem of the prior art) However, in the overtone oscillator configured as described above, for example, in order to prevent spurious oscillation due to the B mode, an element having a large shape and an expensive crystal resonator is used as a filter. Therefore, there is a problem that the miniaturization of the crystal oscillator is hindered and the economy is poor.
[0012]
The overtone oscillator 1 and the resonator 8 operate with overtone vibration with respect to fundamental wave vibration. In this case, the bandwidth of the vibration frequency (resonance frequency) due to overtone vibration is narrower than that of the fundamental wave vibration. That is, the overtone vibration having the fifth harmonic is further suppressed in the harmonic component f5s (f52 to f5n) with respect to the main vibration component f51 as compared with the frequency spectrum in the fundamental vibration (frequency in FIG. 5). Spectrum diagram), bandwidth is narrowed.
[0013]
In short, both the overtone oscillator 1 and the resonator 8 have an oscillation and resonance frequency having a narrower bandwidth with the main vibration component f51 being stronger than the harmonic component f5s (f52 to f5n). Therefore, there is a problem that it is difficult to make the resonance frequency of the overtone resonator 8 coincide with the oscillation frequency depending on the overtone resonator 1 and the productivity is lowered. It should be noted that no oscillation occurs when the oscillation frequency of the overtone oscillator 1 and the resonator 8 and the resonance frequency greatly deviate.
[0014]
(Object of the Invention) The present invention provides a composite crystal resonator including an oscillator and a resonator which are excellent in economic efficiency by promoting downsizing, and an overtone oscillator in which frequency adjustment is facilitated using the same. With the goal.
[0015]
[Solution]
According to the present invention, a second vibration region having a thickness smaller than that of the first vibration region is integrally provided on the crystal piece, and one of the first vibration region and the second vibration region is used as an oscillator that forms an oscillation circuit. It is assumed that the resonator forming the filter is a basic solution means that the first vibration region having a large thickness is operated by overtone vibration relative to the fundamental wave vibration, and the second vibration region having a small thickness is operated by fundamental wave vibration. .
[0016]
[Action]
In the present invention, since one of the first vibration region and the second vibration region having different thicknesses is an oscillator or a resonator and the other is a resonator or an oscillator, for example, a single sealed container can be used to enclose it. . In addition, since the electrodes can be integrally formed on the quartz piece by, for example, vapor deposition using the same mask, the manufacturing process is shortened compared to separate cases. Since the first vibration region having a large thickness is used as overtone vibration and the second vibration region having a small thickness is used as fundamental wave vibration, the bandwidths of vibration frequencies of the first vibration region and the second vibration region are made different. An embodiment of the present invention will be described below.
[0017]
【Example】
FIG. 1 is a diagram of a crystal resonator illustrating one embodiment of the present invention. In addition, the same number is attached | subjected to the same part as a prior art example figure, and the description is abbreviate | omitted or abbreviate | omitted.
As described above, the composite crystal unit is composed of the SC-cut crystal piece 5. In this example, the crystal piece 5 has, for example, a rectangular shape that is long in one direction. Then, one end side from the central portion is formed into a flat plate shape as the first vibration region 11, and a concave portion is formed on the other end side from one main surface side to form a second vibration region 12. The second vibration region 12 is approximately 1 / n (n> 3) with respect to the thickness of the first vibration region 11, and is 1/5 here. That is, the second vibration region 12 is set to have a small thickness corresponding to a vibration frequency (approximately an oscillation frequency) five times the fundamental frequency of the first vibration region 11.
[0018]
The first and second vibration regions 11 and 12 are formed with excitation electrodes 6 (ab) facing each other between the main surfaces and extraction electrodes 7 (ab) extending to both ends including the end surfaces in the width direction. The In the figure, 7b is not shown. The basic electrodes are integrally formed by, for example, vapor deposition using the same mask. Thereafter, the frequency is individually adjusted according to the oscillation frequency and the resonance frequency. The crystal piece 5 is held by a holding mechanism such as a supporter (not shown) or fixed to the bottom surface of the surface mounting container, and is electrically connected to each excitation electrode 6 (ab) in the first and second vibration regions 11 and 12. It is enclosed in a sealed container having connected terminals.
[0019]
In such a case, the composite crystal resonator is incorporated in the oscillation circuit described above. The first vibration region 11 of the composite crystal resonator is the overtone oscillator 1 that operates at the overtone frequency of the fifth harmonic. The second vibration region 12 is a resonator 8A that operates with fundamental vibration with a resonance frequency of an overtone frequency (oscillation frequency) of a fifth harmonic (referred to as a fundamental wave resonator) 8A. Reference numeral 8A is given to the overtone resonator 8 of the conventional example for convenience and is not shown in the figure.
[0020]
These are electrically connected by a wiring path on a circuit board (not shown), and the overtone oscillator 1 forms a Colpitts-type resonance circuit 2, and the resonator 8 ( Here, the above-described oscillation circuit to which the fundamental wave resonator 8A) is connected is configured (see FIG. 3 above).
[0021]
With such a configuration, the overtone oscillator 1 and the fundamental wave resonator 8A are integrally formed on the same crystal piece 5. Therefore, for example, since one sealed container can be formed, miniaturization is promoted. For example, the electrodes can be integrally formed by vapor deposition using the same mask, so that the manufacturing process can be shortened and the economy can be improved.
[0022]
In addition, since the fundamental wave resonator 8A is connected to the resonance circuit 2 including the overtone resonator 1 and the dividing capacitor 3 (ab), the oscillation frequency band having a high frequency is further narrowed as described above. Therefore, in this case, the spurious oscillation is prevented by suppressing the B mode in particular for the SC cut main vibration (C mode).
[0023]
In this embodiment, the oscillation frequency of the overtone oscillator 1 is passed (resonated) by the fundamental wave resonator 8A operating with fundamental wave vibration. In contrast to the overtone resonator 8, the fundamental wave resonator 8A has a higher harmonic component fs than the fundamental frequency component f1 of the resonance frequency (vibration frequency), as shown in FIG. Because it is large, the bandwidth is widened.
[0024]
Therefore, even if the resonance frequency of the fundamental wave resonator 8A with respect to the oscillation frequency is shifted, the oscillation frequency passes through the fundamental wave resonator because the bandwidth of the resonance frequency is wide. However, even in this case, the B mode is cut off. As a result, the frequency adjustment is facilitated as compared with the case of using the conventional overtone resonator 8.
[0025]
[Second embodiment]
In the first embodiment, the first vibration region 11 of the composite crystal resonator is the overtone resonator 1, and the second vibration region 12 is the fundamental wave resonator 8A. In the second embodiment, the first resonator region 11 having a small thickness is used. The second vibration region 12 is a fundamental wave oscillator 1A that operates with a fundamental wave, and the thick first vibration region 11 is an overtone resonator 8 that operates at an overtone frequency. Other than this, the description is omitted because it is the same as the first embodiment.
[0026]
In such a configuration, since the oscillation frequency is based on fundamental wave vibration, the bandwidth is widened as described above. Since the resonance frequency is overtone vibration, the bandwidth is narrowed. Therefore, even if the resonance frequency of the overtone resonator 8 is slightly deviated from the oscillation frequency of the fundamental wave resonator 1A, the oscillation frequency is relatively wide, so that a frequency component that matches the resonance frequency of the overtone resonator 8 passes. . Thus, contrary to the first embodiment, strictly controlling the resonance frequency of the overtone resonator 8 facilitates the frequency adjustment of the fundamental wave resonator 1A.
[0027]
In the first and second embodiments as well, since the oscillator and the resonator are formed from the same crystal piece, the characteristic that the frequency changes with temperature, that is, the so-called frequency temperature characteristic is made substantially the same. Therefore, the stability with respect to the ambient temperature can be increased as compared with the conventional case in which the oscillator and the resonator are separated. In this case, even if the individual crystal resonators as the oscillator and the resonator are housed in a thermostatic bath and used for high stability, the same frequency change occurs due to the fluctuation of the temperature in the bath. Oscillation can be maintained stably.
[0028]
[Other matters]
In the above-described embodiment, the crystal resonator is SC cut. However, the present invention can be similarly applied to, for example, AT cut or BT cut in which the vibration state is the same as the thickness-slip vibration state similar to the SC cut. Even in this case, spurious oscillation caused by, for example, a contoured vibration state close to the oscillation frequency is prevented. The first vibration region 11 has a thickness of the crystal piece 5 itself and the second vibration region 12 has a recess. However, for example, the first vibration region 11 may be a recess from one main surface side or both main surface sides having different depths, or simply A step may be provided to make the thickness of the first vibration region 11 and the second vibration region 12 different. In short, what is necessary is just to make the substantial thickness converted into the vibration (resonance) frequency of the 1st vibration area | region 11 and the 2nd vibration area | region 12 in which the excitation electrode 6 (ab) is formed different.
[0029]
Further, for example, the excitation electrode 6 (ab) opposed between the two principal surfaces is provided in the second vibration region 12 used as the fundamental wave resonator 8A. For example, a pair of input / output electrodes is formed on both the principal surfaces. A so-called MCF (Monolithic crystal filter) may be used. Further, although the fundamental wave resonator 8A is connected to the resonance circuit 2 in the oscillation closed loop, for example, when the overtone frequency (a harmonic component of the oscillation frequency) is selected by providing it at the output side of the crystal oscillator, that is, outside the oscillation closed loop. Applicable. In the present invention, even if a resonator that substantially functions as a filter is provided outside the oscillation closed loop, the overtone oscillator is used.
[0030]
In short, in the present invention, an oscillator and a resonator that operate with different vibrations such as fundamental wave vibration or overtone vibration are formed on a single crystal piece to form an oscillator and a filter that form an oscillation circuit. It is intended to be applied to a crystal oscillator in which a child is used, and those based on such a purpose, including arbitrary modifications as appropriate, belong to the technical scope of the present invention. In the above embodiment, the fundamental wave vibration and the overtone vibration are used. However, as the overtone vibration, for example, the oscillator may be a third order and the resonator may be a fifth order overtone, and the oscillation and resonance frequencies may be matched. In this case, the low-order overtone frequency corresponds to the fundamental frequency.
[0031]
【The invention's effect】
According to the present invention, a second vibration region having a thickness smaller than that of the first vibration region is provided integrally with a crystal piece with respect to the first vibration region, and either the first vibration region or the second vibration region is provided as an oscillation circuit. Since the first vibration region operates at an overtone frequency relative to the fundamental wave and the second vibration region operates at the fundamental wave frequency, the other vibration region is used as a resonator that forms a filter. It is possible to provide a composite crystal resonator excellent in economic efficiency and an overtone oscillator using the same.
[Brief description of the drawings]
FIG. 1 is a diagram of a composite crystal resonator (crystal piece) for explaining an embodiment of the present invention.
FIG. 2 is a frequency spectrum diagram illustrating an embodiment of the present invention.
FIG. 3 is a circuit diagram of a crystal oscillator for explaining a conventional example.
FIG. 4 is a plan view of a crystal piece for explaining a conventional example.
FIG. 5 is a frequency spectrum diagram illustrating a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crystal oscillator (resonator), 2 Resonance circuit, 3 (ab) Divided capacitor, 4 transistor, 5 Crystal piece, 6 Excitation electrode, 7 Extraction electrode, 8 Crystal oscillator (resonator), 9 Bias resistance, 10 Adjustment Capacitor.

Claims (6)

In a quartz crystal resonator comprising a quartz piece having a thickness-slip vibration mode in which the vibration frequency is in inverse proportion to the thickness, the quartz piece has a first vibration region and a second vibration region having different thicknesses (where the thickness of the first vibration region> second vibration). Thickness of the region) is integrally provided, and either the first vibration region or the second vibration region is an oscillator that forms an oscillation circuit, and the other is a resonator that forms a filter, and the first vibration region is A composite crystal resonator that operates with overtone vibration relative to fundamental vibration, and wherein the second vibration region operates with fundamental vibration. 2. The composite crystal resonator according to claim 1, wherein the first vibration region is a resonator that operates by overtone vibration, and the second vibration region is a resonator that operates by fundamental wave vibration. The first vibration area is a resonator operating at overtone vibration, the composite crystal resonator of claim 1, wherein the second vibration area is obtained by a resonator that operates at the fundamental wave vibration. The crystal unit according to claim 1, wherein the crystal piece is SC cut. An overtone crystal oscillator in which a resonator is inserted in an oscillation closed loop having a resonance circuit having an oscillator composed of a crystal resonator as an inductor component and an oscillation amplifier, and the resonator and the resonator are provided. An overtone crystal oscillator characterized by applying the composite crystal resonator of No. 1. 6. The resonance circuit according to claim 5, wherein the resonance circuit includes a crystal resonator as an inductor component and a split capacitor, and the crystal resonator as the resonator is connected between a midpoint of the split capacitor and an amplifier for an oscillator. Overtone crystal oscillator.

Images