CN108923751B - Crystal oscillator mode suppression circuit - Google Patents
Crystal oscillator mode suppression circuit Download PDFInfo
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- CN108923751B CN108923751B CN201810947828.6A CN201810947828A CN108923751B CN 108923751 B CN108923751 B CN 108923751B CN 201810947828 A CN201810947828 A CN 201810947828A CN 108923751 B CN108923751 B CN 108923751B
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- 239000013078 crystal Substances 0.000 title claims abstract description 63
- 230000001629 suppression Effects 0.000 title claims abstract description 57
- 239000003990 capacitor Substances 0.000 claims abstract description 58
- 230000010355 oscillation Effects 0.000 claims abstract description 55
- 230000005669 field effect Effects 0.000 claims description 9
- 238000000034 method Methods 0.000 abstract description 5
- 230000008878 coupling Effects 0.000 abstract description 4
- 238000010168 coupling process Methods 0.000 abstract description 4
- 238000005859 coupling reaction Methods 0.000 abstract description 4
- 230000000694 effects Effects 0.000 abstract description 4
- 230000000452 restraining effect Effects 0.000 abstract description 3
- 230000008859 change Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
- H03B5/02—Details
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
- H03B5/30—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator
- H03B5/32—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator
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- Oscillators With Electromechanical Resonators (AREA)
Abstract
The invention discloses a crystal oscillator mode suppression circuit, comprising: power supply terminal, first node, second node, crystal, first oscillation capacitor, and second oscillation capacitorA capacitor, a suppression circuit and an amplifying element. The present invention provides a crystal oscillator mode suppression circuit by adjusting only the inductance L1And a capacitor C1The resonance is at or near the C-mode frequency of the harmonic overtone times required by the SC-cut crystal, so that the effect of restraining the B-mode and other harmonic overtone frequencies can be achieved, and the debugging is simple. Mode suppression is performed only by using amplitude conditions, the influence on oscillation phase conditions is small, debugging is convenient, parameter coupling is small, and an oscillation capacitor C in an oscillation tuning loop2And C3The method can be independently adjusted according to the oscillation starting condition, the requirements of increasing the on-load Q value of the crystal and the like, can effectively improve the stability of the oscillation frequency and the quality of the oscillation signal, and has strong circuit environment adaptability and high reliability.
Description
Technical Field
The invention relates to the technical field of crystal oscillators. And more particularly to a crystal oscillator mode suppression circuit.
Background
The crystal oscillator is a high-stability time and frequency reference, and can be widely used in various communication, navigation and measurement equipment. The crystal is a key device in the crystal oscillator, and the performance of the oscillator is different by using different types of crystals. Among them, the crystal oscillator using the SC-cut crystal can obtain more excellent phase noise performance because the Q value of the SC-cut crystal is higher. The SC-cut crystal comprises a plurality of vibration modes of an A mode, a B mode and a C mode, and a plurality of overtone modes of fundamental frequency, third overtone, fifth overtone and the like. The C-mode has the characteristics of stress compensation effect, good vibration resistance, small thermal transient and the like, and the C-mode of the SC cut crystal is generally used in a crystal oscillator. In order to utilize the C-mode and higher harmonic of the crystal, it is necessary to suppress the B-mode and lower harmonic in the oscillation circuit by appropriate circuit forms and parameters. Fig. 1 is a pierce oscillator circuit typically using an SC-cut crystal, which mainly uses oscillation phase conditions for mode suppression. Wherein the inductance LfCapacitor CfAnd an inductance LeForming a B-mode and overtone suppression circuit. SC cut crystal N-th harmonic digital C-mode frequency f0Is the oscillation frequency of the oscillating circuit. The frequency of the B-mode of N harmonics of the crystal is fB. Crystal (N-2) harmonic B mode frequency fN-2. Inductor LfAnd a capacitor CfSeries resonance frequency f1. Inductor LfCapacitor CfAnd an inductance LeParallel resonance frequency of f2At a frequency f0Is equivalent to a capacitance C ". In order to make the oscillating circuit normally work at the frequency f0An inductance LfCapacitor CfAnd an inductance LeThe parameter value of (c) is required to satisfy the equation fB>f1>f0>f2>fN-2. C "should be smaller than the starting capacitance of the oscillating circuit. Therefore, in order to determine and solve to obtain appropriate parameter values, the calculation is complex, and the direct solution is difficult. The parameter heuristic method is adopted for solving, repeated heuristic is usually needed to obtain parameter solutions which meet requirements and are easy to realize, the solving efficiency is low, and the calculation amount is large. Moreover, the frequencies of the B mode and the C mode of the SC cut crystal are similar; as the number of overtones increases, the overtone interval also decreases. Therefore, the inductor L in FIG. 1fCapacitor CfAnd an inductance LeThe adjustable range of the parameters is small, and the small change of the parameters can bring obvious change of equivalent values, so that the oscillation condition is obviously influenced, namely the oscillation circuit can inhibit the inductance L of a circuit elementfCapacitor CfAnd an inductance LeIs sensitive. Particularly, as the oscillation frequency rises, the oscillation circuit is more sensitive to the parameters of the suppression circuit, the requirement on the parameter precision of components is high, and the debugging is inconvenient. When factors such as environment temperature change and the like cause circuit parameters to drift, the phenomenon that B mode and other overtone modes cannot be inhibited easily occurs, and the use reliability of the product is influenced.
Disclosure of Invention
In order to solve at least one of the above problems, the present invention provides a crystal oscillator mode suppression circuit, comprising:
the circuit comprises a power supply end, a first node, a second node, a crystal, a first oscillation capacitor, a second oscillation capacitor, a suppression loop and an amplifying element;
one end of the crystal, the output end of the amplifying element and the second oscillating capacitor are connected with a power supply end through a first node;
the first oscillating capacitor is connected with the other end of the crystal and the second node;
the input end of the amplifying element is connected with the other end of the crystal
The suppression loop is connected with the common end of the amplifying element and the second node;
the second oscillating capacitor and the second node are grounded, so that the crystal, the first oscillating capacitor and the second oscillating capacitor jointly form an oscillating loop.
Preferably, the suppression circuit comprises:
a first suppression inductor connected to a common terminal of the amplifying element, and a suppression capacitor connected to the inductor;
wherein the suppression capacitor is connected to the second node.
Preferably, the circuit further comprises:
a second suppressing inductance or resistance connected between the power supply terminal and the first node.
Preferably, the suppression circuit further comprises:
and the resistor is connected with the first suppression inductor and the suppression capacitor in parallel.
Preferably, the amplifying element is a transistor.
Preferably, the transistor is a bipolar transistor or a field effect transistor.
Preferably, the transistor is a field effect transistor, and the field effect transistor comprises a PMOS transistor and an NMOS transistor.
Preferably, the transistor is a bipolar transistor, and the bipolar transistor includes a PNP transistor and an NPN transistor.
Preferably, the crystal is an SC-cut crystal.
The invention has the following beneficial effects:
the present invention provides a crystal oscillator mode suppression circuit by adjusting only the inductance L1And a capacitor C1The resonance of the crystal is at or near the C-mode frequency of the SC-cut crystal, so that the effect of restraining the B-mode and other overtone frequencies can be achieved, and the debugging is simple. Inductor L1And a capacitor C1The B-mode and overtone suppression circuit and the oscillation tuning circuit are separated, an alternating current short circuit function is achieved at the oscillation frequency of the C-mode, the parameters of the oscillation tuning circuit are not affected basically, namely, mode suppression is performed only by using the amplitude condition, the influence on the oscillation phase condition is small, debugging is convenient, and parameter coupling is small. Oscillating capacitor C in an oscillation tuning circuit2And C3Can be adjusted according to the starting vibration condition and the crystal is enlargedThe Q value and other requirements are independently adjusted, and the stability of the oscillation frequency and the quality of the oscillation signal can be effectively improved. Inductor L1And a capacitor C1The resonance network has a certain bandwidth and is coupled to an inductor L1And a capacitor C1The requirement on the precision of the parameters is not high, when the parameters drift caused by the change of the working environment of the crystal oscillator, the oscillation condition is basically not influenced, the adaptability of the circuit environment is strong, and the reliability is high.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
Fig. 1 shows a schematic diagram of a pierce oscillator circuit in the prior art.
Fig. 2 is a schematic diagram of a mode suppression circuit of a crystal oscillator according to an embodiment of the present invention.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below with reference to preferred embodiments and the accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
Referring to fig. 2, the present invention provides a crystal oscillator mode suppression circuit, including: power source terminal Vcc, first node P1A second node P2Crystal G1A first oscillation capacitor C2A second oscillating capacitor C3Suppression circuit and amplifying element V1(ii) a The crystal G1One terminal, amplifying element V1And a second oscillating capacitor C3Through the first node P1Connected with a power supply terminal Vcc; the first oscillating capacitor C2And the crystal G1The other end and the second node P2Connecting; the amplifying element V1And the crystal G1The other end is connected; the suppression circuit and the amplifying element V1And said second node P2Connecting; the second oscillating capacitor C3And said second node P2Grounded to make the crystal G1A first oscillation capacitor C2A second oscillating capacitor C3Together forming an oscillating circuit.
Wherein the suppression loop comprises: and an amplifying element V1First suppression inductor L connected to the common terminal1And the inductor L1Connected suppression capacitance C1. Wherein the suppression capacitance C1And the second node P2And (4) connecting.
Of course, the suppression loop further comprises a first suppression inductor L1And a suppression capacitance C1Parallel connected resistors R1. The resistor functions to provide a dc path, i.e., to provide a quiescent operating point for the amplifying element.
The present invention provides a crystal oscillator mode suppression circuit by adjusting only the inductance L1And a capacitor C1The resonance is at or near the C-mode frequency of the harmonic overtone times required by the SC-cut crystal, so that the effect of restraining the B-mode and other harmonic overtone frequencies can be achieved, and the debugging is simple. Inductor L1And a capacitor C1The B-mode and overtone suppression circuit and the oscillation tuning circuit are separated, an alternating current short circuit function is achieved at the oscillation frequency of the C-mode, the parameters of the oscillation tuning circuit are not affected basically, namely, mode suppression is performed only by using the amplitude condition, the influence on the oscillation phase condition is small, debugging is convenient, and parameter coupling is small. Oscillating capacitor C in an oscillation tuning circuit2And C3The method can be independently adjusted according to the oscillation starting condition, the requirements of increasing the crystal loaded Q value and the like, and can effectively improve the stability of the oscillation frequency and the quality of the oscillation signal. Inductor L1And a capacitor C1The resonance network has a certain bandwidth and is coupled to an inductor L1And a capacitor C1The requirement on the precision of the parameters is not high, when the parameters drift caused by the change of the working environment of the crystal oscillator, the oscillation condition is basically not influenced, the adaptability of the circuit environment is strong, and the reliability is high.
Of course, in order to operate the transistor V1 stably and reliably, a proper static operating point needs to be set in the circuit. As is well known to those skilled in the art, in addition to the need to provide transistor V1 with the dc path already shown in fig. 2, it is also necessary to provide the appropriate dc potential to the base of transistor V1. This is typically accomplished by connecting a resistor between the base of transistor V1 and power supply terminal Vcc, or between the base of transistor V1 and power supply terminal Vcc and ground, respectively. Meanwhile, in order to improve the quality of the output signal, a filter capacitor is also required to be added between the power source terminal Vcc and the ground to suppress the ac interference of the power source terminal Vcc.
Further, the circuit further comprises: is connected between the power supply terminal Vcc and the first node P1Second suppression inductance L therebetween2Or a resistor for suppressing the alternating current signal at the power supply terminal and providing a static operating point.
Preferably, the amplifying element is a transistor, and specifically, may be a bipolar transistor or a field effect transistor, and more specifically, when the transistor is a bipolar transistor, the bipolar transistor includes a PNP transistor and an NPN transistor. When the transistor is a field effect transistor, the field effect transistor comprises a P-channel transistor and an N-channel transistor.
As known to those skilled in the art, when the amplifying element is a bipolar transistor, the output terminal of the amplifying element in this embodiment is a collector of a triode, the input terminal of the amplifying element is a base of the triode, and the common terminal of the amplifying element is an emitter of the triode, which is not described in detail herein.
Of course, as mentioned in the prior art of the present invention, the crystal in the present invention can be an SC-cut crystal, and the present invention is not described in detail.
The invention relates to an inductor L in figure 1fCapacitor CfAnd an inductance LeThe formed parallel network is split into inductors L in figure 21And a capacitor C1Series B-mode and overtone suppression network, and oscillation capacitor C3The two parts separate the suppression network and the oscillation circuit, reduce the parameter coupling between the suppression network and the oscillation circuit, have small interference in the debugging process, and are simple and easy to operate. And the suppression network is connected to the oscillation circuit through the emitter of the triode, and the isolation between the suppression network and the oscillation tuning circuit is high. Inductor L1And a capacitor C1Has less influence on the parameters of the oscillation tuning loopThe method does not affect the oscillation phase condition basically, has little influence on the crystal loaded Q value, and the oscillation circuit can obtain better frequency stability. Inductor L1And a capacitor C1The series resonance frequency of (2) is the C-mode frequency at which the SC-cut crystal uses overtone orders. Inductance L when the frequency deviates from the C-mode frequency1And a capacitor C1The equivalent impedance is increased, the gain of the oscillation amplifying circuit is reduced, the oscillation condition is weakened, and the suppression principle is simple and easy to realize. Inductor L1And a capacitor C1The series resonance has a certain bandwidth, and the resonance can be realized only near the frequency of the C mode, so that the requirement on the parameter accuracy of the component is reduced. Moreover, when a voltage control circuit needs to be added or the parameter drift is caused by the change of the working environment of the crystal oscillator, as long as the oscillation frequency is still in the inductance L1And a capacitor C1Within the range of the bandwidth of the series resonance, the oscillating circuit can still work normally, so the circuit has strong environmental adaptability and high reliability.
In addition, the invention can realize higher frequency stability while ensuring that the B mode and other overtone modes of the SC cut crystal can be simply and conveniently inhibited. The circuit has high reliability, strong environmental adaptability and strong practicability.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (7)
1. A crystal oscillator mode suppression circuit, comprising:
the circuit comprises a power supply end, a first node, a second node, a crystal, a first oscillation capacitor, a second oscillation capacitor, a suppression loop and an amplifying element;
one end of the crystal, the output end of the amplifying element and one end of the second oscillating capacitor are connected with a power supply end through a first node;
one end of the first oscillation capacitor is connected with the other end of the crystal, and the other end of the first oscillation capacitor is connected with the second node;
the input end of the amplifying element is connected with the other end of the crystal;
one end of the suppression loop is connected with the common end of the amplifying element, and the other end of the suppression loop is connected with the second node;
the other end of the second oscillation capacitor and the second node are grounded, so that the crystal, the first oscillation capacitor and the second oscillation capacitor form an oscillation loop together;
the crystal is an SC cut crystal;
the suppression loop includes:
a first suppression inductor connected with the common end of the amplifying element, and one end of a suppression capacitor connected with the first suppression inductor, wherein the resonance of the first suppression inductor and the suppression capacitor is at or near the C-mode frequency of the SC-cut crystal;
wherein the other end of the suppression capacitor is connected to the second node.
2. The circuit of claim 1, wherein the circuit further comprises:
a second suppressing inductance or resistance connected between the power supply terminal and the first node.
3. The circuit of claim 1, wherein the suppression loop further comprises:
and the resistor is connected with the first suppression inductor and the suppression capacitor in parallel.
4. The circuit of claim 1, wherein the amplifying element is a transistor.
5. The circuit of claim 4, wherein the transistor is a bipolar transistor or a field effect transistor.
6. The circuit of claim 5, wherein the transistor is a bipolar transistor, and wherein the bipolar transistor comprises a PNP transistor or an NPN transistor.
7. The circuit of claim 5, wherein the transistor is a field effect transistor, and wherein the field effect transistor comprises a P-channel transistor or an N-channel transistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810947828.6A CN108923751B (en) | 2018-08-20 | 2018-08-20 | Crystal oscillator mode suppression circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810947828.6A CN108923751B (en) | 2018-08-20 | 2018-08-20 | Crystal oscillator mode suppression circuit |
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| Publication Number | Publication Date |
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| CN108923751A CN108923751A (en) | 2018-11-30 |
| CN108923751B true CN108923751B (en) | 2022-07-08 |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS55147808A (en) * | 1979-05-07 | 1980-11-18 | Sony Corp | Overtone oscillator |
| JP2004266583A (en) * | 2003-02-28 | 2004-09-24 | Toyo Commun Equip Co Ltd | Piezoelectric oscillator |
| JP4455979B2 (en) * | 2004-11-16 | 2010-04-21 | 京セラキンセキ株式会社 | Crystal oscillator |
| JP4628878B2 (en) * | 2005-06-07 | 2011-02-09 | 日本電波工業株式会社 | Crystal oscillation circuit |
| US7369005B2 (en) * | 2005-06-07 | 2008-05-06 | Nihon Dempa Kogyo Co., Ltd. | Colpitts oscillator |
| JP2010041346A (en) * | 2008-08-05 | 2010-02-18 | Nippon Dempa Kogyo Co Ltd | Quartz oscillation circuit of suboscillation suppressing type |
| CN201360238Y (en) * | 2009-02-26 | 2009-12-09 | 唐山晶源裕丰电子股份有限公司 | Voltage-controlled triple overtone crystal oscillator |
| WO2014123519A1 (en) * | 2013-02-06 | 2014-08-14 | Empire Technology Development Llc | Devices, systems, and methods for detecting odorants |
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