CN101764571A - Crystal oscillator with temperature compensation - Google Patents
Crystal oscillator with temperature compensation Download PDFInfo
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- CN101764571A CN101764571A CN200910253251A CN200910253251A CN101764571A CN 101764571 A CN101764571 A CN 101764571A CN 200910253251 A CN200910253251 A CN 200910253251A CN 200910253251 A CN200910253251 A CN 200910253251A CN 101764571 A CN101764571 A CN 101764571A
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Abstract
The invention provides a crystal oscillator with temperature compensation, comprising a crystal, a negative temperature coefficient (NTC) capacitor is adopted in at least one of a plurality of capacitors with load capacitance, which form the crystal in the crystal oscillator. An expensive thermosensitive resistance network is replaced by a cheap NTC capacitor, thereby reducing the cost, greatly improving the temperature stability of the crystal oscillator and greatly increasing the application scope of the crystal oscillator.
Description
Technical field
The present invention relates to possess the crystal oscillator of temperature-compensating, particularly, relate to a kind of by using negative temperature coefficient (NTC) capacitor to realize the VCXO (VCXO) of temperature-compensating.
Background technology
International Electrotechnical Commission (IEC) is divided into 4 classes with quartz oscillator: common crystal oscillator (SPXO), VCXO (VCXO), temp. compensation type crystal oscillator (TCXO), thermostatic control formula crystal oscillator (OCXO).The present developing digit compensated crystal oscillator (DCXO) etc. that also has.Be followed successively by according to frequency accuracy order from low to high: common crystal oscillator, VCXO, temp. compensation type crystal oscillator, thermostatic control formula crystal oscillator.Common crystal oscillator is because frequency accuracy is less demanding, thus generally do not adopt any temperature frequency indemnifying measure, cheap, usually as the clock devices of microprocessor.VCXO is generally used for phase-locked loop circuit, does not generally have to adopt the temperature frequency indemnifying measure that adds.The temp. compensation type crystal oscillator adopts the temperature sensor that adds to carry out the temperature frequency compensation, and frequency accuracy reaches 10
-7～10
-6Magnitude is generally used for cell-phone, cell phone, two-way wireless communication device etc.Thermostatic control formula crystal oscillator places insulating box with crystal and oscillating circuit, to eliminate the influence of variation of ambient temperature to frequency.Be mainly used in some specific occasions.
VCXO in these four kinds of crystal oscillators is generally used for that frequency accuracy is had certain requirement but not high occasion, such as low side CDMA/GSM terminal, module etc.VCXO mainly comprises usually: as transistor, CMOS pipe or the inverter of exciting unit; Quartz crystal; As the capacitor of quartz crystal load, variable capacitance diode etc.
According to the syndeton of these element of VCXO, VCXO can comprise examines BZ (Colpitts) structure or Pierre Si (Pierce) structure.VCXO generally is not with temperature-compensation circuit, and its temperature drift depends primarily on the temperature of quartz crystal and floats characteristic.The temperature drift of VCXO depends on that also the temperature of additional peripheral device (as the capacitor as the quartz crystal load) floats characteristic in addition.VCXO often can only accomplish in-30 ℃ to+85 ℃ scopes+/-15ppm to+/-frequency accuracy of 20ppm.
The typical frequencies temperature drift characteristic of traditional VCXO as shown in Figure 1, among Fig. 1, every curve is represented the frequency temperature drift characteristic of the VCXO of a test.As can be seen from Figure 1, the frequency of VCXO is bigger with the drift of temperature.Therefore, usually not floating with the temperature of the VCXO of temperature-compensating can be relatively more severe.
Because the temperature drift of VCXO is not only depended on the temperature of quartz crystal and is floated characteristic, the temperature that also depends on additional peripheral device (as the capacitor as the quartz crystal load) is floated characteristic, therefore, at present typical VCXO is selected the capacitor of the relatively cheap NPO of price (NegativePositive Zero) capacitor as the quartz crystal load usually for use.The NPO capacitor is a kind of the most frequently used monolithic ceramic capacitor with temperature compensation characteristic, and its capacitance and dielectric loss are highly stable.The temperature coefficient scope of NPO capacitor is positive and negative symmetry (+/-30ppm/K within), and its filled media is made up of rubidium, samarium and some other rare oxides.The drift of NPO capacitor or hysteresis are less than ± 0.05%.But be to use NPO capacitor as the quartz crystal load, still can not fundamentally overcome the temperature drift problem of VCXO with temperature compensation characteristic.
Overcome the another kind of method that the temperature of VCXO floats and be to use the negative temperature coefficient resister network to come temperature is compensated, do like this, cost also can be than higher.
Therefore for the occasion of the employing VCXO of ask for something certain frequency precision, expect a kind of VCXO that possesses the uniform temperature compensation of cheapness.
Summary of the invention
At above-mentioned shortcoming and defect, the present invention proposes a kind of crystal oscillator that possesses temperature-compensating, particularly, relate to a kind of by using negative temperature coefficient (NTC) capacitor to realize the VCXO of temperature-compensating.
The key point of the basic circuit structure of the crystal oscillator that possesses temperature-compensating of the present invention is to substitute with negative temperature coefficient (NTC) capacitor the capacitor or the NPO capacitor of Chang Zuowei quartz crystal load.In order to increase the proportion of NTC capacitor in whole equivalent load capacitance, also can increase a NTC capacitor in parallel at the two ends of quartz crystal with it, this point is also very crucial, because the temperature coefficient of present commercial NTC capacitor is on the low side, only use negative temperature coefficient (NTC) capacitor to substitute the capacitor of Chang Zuowei quartz crystal load or the temperature drift amount that the NPO capacitor might not offset quartz crystal.
Particularly, according to one aspect of the invention, a kind of crystal oscillator that possesses temperature-compensating is provided, described crystal oscillator comprises crystal, in described crystal oscillator, a plurality of capacitors that form the load capacitance of described crystal adopt one of at least the NTC capacitor to realize.
Wherein said crystal oscillator also comprises: a NTC capacitor in parallel is connected in parallel on the two ends of crystal.
Wherein said crystal oscillator is one of common crystal oscillator, VCXO, temp. compensation type crystal oscillator, thermostatic control formula crystal oscillator.
Wherein when described crystal oscillator was VCXO, the exciting unit of pressuring controling crystal oscillating circuit was realized with transistor, metal-oxide-semiconductor or inverter thrin.
Wherein pressuring controling crystal oscillating circuit is to examine BZ structure or Pierre's Si structure.
Wherein the material of NTC capacitor is U2J, temperature coefficient be 750ppm+/-120ppm/ ℃.
According to another aspect of the present invention, provide a kind of VCXO that possesses temperature-compensating, described VCXO comprises: first circuit and second circuit.Described first circuit comprises: first capacitor, an end ground connection of described first capacitor; Second capacitor is connected with an end of described first capacitor and described crystal; The 3rd capacitor is connected with the other end of described crystal, the other end ground connection of described the 3rd capacitor, and wherein said first capacitor, described second capacitor and described the 3rd capacitor are as the load of described crystal; Variable capacitance diode, an end are connected on the connected node of described first capacitor and described second capacitor, other end ground connection, and wherein automatic frequency control signal is input to the connected node of described first capacitor and described second capacitor.Second circuit is used to be provided with the offset operation condition of VCXO, forms the feedback loop of described first circuit, excitation and amplify oscillator signal, and the output signal of output VCXO.
In described VCXO, form and one of at least adopt the NTC capacitor to realize in second capacitor of load capacitance of described crystal and the 3rd capacitor.
According to technique scheme of the present invention, utilize the negative temperature coefficient feature of NTC capacitor, when temperature raises, the load capacitance of the quartz crystal that is made of the NTC capacitor diminishes, this uprises crystal oscillation frequency, has just in time remedied crystal oscillator itself and has raise and the shortcoming of frequencies go lower with temperature; When temperature reduced, it is big that the load capacitance of the quartz crystal that is made of the NTC capacitor becomes, and this makes the crystal oscillation frequency step-down, just in time remedied crystal oscillator itself with the temperature reduction shortcoming of frequency gets higher.Like this, the range of linearity of crystal frequency temperature drift just can obtain good compensation.For the nonlinear area of crystal frequency temperature drift, though utilize the crystal oscillator of NTC capacitor can overcompensation, in certain temperature range, such as at-20 ℃ to+80 ℃, the basic acceptable of the error that this overcompensation brings.
Replace relatively more expensive thermistor network with cheap NTC capacitor, reduced cost, and improved the temperature stability of VCXO greatly, experimental data shows, adopt mode of the present invention, as long as increase 6-7 branch RMB just can float the temperature of VCXO be reduced to+/-5ppm about, thereby the scope of application of VCXO is improved greatly.
Description of drawings
By below in conjunction with the detailed description of accompanying drawing, will understand the present invention better to example embodiment.It should be clearly understood that described example embodiment only is as an illustration and example, and the invention is not restricted to this.The spirit and scope of the present invention are only limited by the particular content of appended claims.Brief description of drawings is described below, and wherein similar Reference numeral refers to same or analogous element in the accompanying drawing:
Fig. 1 is the typical frequency temperature drift characteristic of traditional VCXO.
Fig. 2 is the circuit diagram of the VCXO of traditional employing Pierre Si structure.
Fig. 3 is the ac equivalent circuit schematic diagram of the core of the VCXO circuit 100 among Fig. 2.
Fig. 4 is the circuit diagram according to the VCXO of the employing Pierre Si structure of first embodiment of the invention.
Fig. 5 is the ac equivalent circuit schematic diagram of the core of the VCXO circuit 300 among Fig. 4
Fig. 6 is the circuit diagram according to the VCXO of the employing Pierre Si structure of second embodiment of the invention.
Fig. 7 is the ac equivalent circuit schematic diagram of the core of the VCXO circuit 300 among Fig. 6.
Fig. 8 is that the electric capacity of NTC capacitor of different materials is with the performance plot of temperature.
Fig. 9 is the frequency temperature drift characteristic according to the VCXO of second embodiment of the invention.
Embodiment
To introduce example embodiment of the present invention in detail now, its example is shown in the drawings.
With reference to the accompanying drawings, be example with the VCXO, by with VCXO of the prior art with according to the concrete comparison of VCXO of the present invention, make projects of the present invention and effect more obvious.
Fig. 2 is the circuit diagram of the VCXO of traditional employing Pierre Si structure.
With reference to Fig. 2, the typical at present VCXO circuit 100 of Pierre's Si structure that adopts comprises voltage-controlled end input isolation resistor 101, accumulator 1001, biasing, feedback, excitation and output circuit 1002, decoupling filter circuit 1003, output coupling capacitor 115.
Automatic frequency control signal AFC is input to accumulator 1001 via voltage-controlled end input isolation resistor 101.
Biasing, feedback, excitation and output circuit 1002 are used to be provided with the offset operation condition of VCXO, form the feedback loop of accumulator, excitation and amplify oscillator signal, and the output signal of VCXO cushioned and isolate.Biasing, feedback, excitation and output circuit 1002 comprise: driver transistor 123 and output transistor 113; Be connected in series in the resistor 109,110,111 between power supply VCC and the ground; Be connected the resistor 122 between the collector electrode of power supply VCC and output transistor 113; And the emitter and the resistor between the ground 114 that are connected driver transistor 123.The emitter of output transistor 113 is connected to the output of accumulator 1001 via resistor 112.The collector electrode of driver transistor 123 is connected to the output and resistor 112 connected nodes of accumulator 1001.The base stage of output transistor 113 is connected to the connected node between the resistor 109,110.The base stage of driver transistor 123 is connected to the connected node between the resistor 110,111.The collector electrode output signal of output transistor 113 is as the output signal of biasing, feedback, excitation and output circuit 1002, the output signal of biasing, feedback, excitation and output circuit 1002 via after the output coupling capacitor 115 as the output of VCXO circuit 100.
The core of VCXO circuit 100 is: accumulator 1001 and output transistor 113 and bias resistor 109,110,111,114, Pierre's Si pressuring controling crystal oscillating circuit that decoupling capacitor 116 constitutes.
Fig. 3 is the ac equivalent circuit schematic diagram of the core of the VCXO circuit 100 among Fig. 2.
Among Fig. 3, the equivalent capacity of the capacitor 104 in capacitor 201 corresponding diagram 2, capacitor 202 corresponding capacitors 102, variable capacitor 203 corresponding variable capacitance diodes 103, transistor 204 corresponding driver transistors 123, capacitor 205 corresponding capacitors 106.
The load capacitance of crystal 2 06 equals capacitor 202 and the variable capacitor 203 back resulting electric capacity afterwards of connecting with capacitor 205 again of connecting with capacitor 201 in parallel, except variable capacitor 203, other capacitors all adopt the almost capacitor of the NPO of zero temp shift (C0G) material usually, total load capacitance of crystal 2 06 can not change along with variations in temperature substantially like this, and the temperature characterisitic of oscillating circuit depends primarily on the performance of crystal 2 06.The similar frequency-temperature characteristic shown in Figure 1 of the temperature characterisitic of oscillating circuit.
Fig. 4 is the circuit diagram according to the VCXO of the employing Pierre Si structure of first embodiment of the invention.VCXO circuit 300 comprises voltage-controlled end input isolation resistor 301, accumulator (first circuit) 3001, biasing, feedback, excitation and output circuit (second circuit) 3002, decoupling filter circuit 3003, output coupling capacitor 315.
The difference of the VCXO circuit 100 of this VCXO circuit 300 and Fig. 2 is that the capacitor 304,306 in the accumulator 3001 has adopted the capacitor of NTC material.The invention is not restricted to this, as long as, all can realize technological thought of the present invention with capacitor 304,306 capacitor that adopts one of at least the NTC material in the two.
The core of VCXO circuit 300 is: accumulator 3001 and driver transistor 322 and bias resistor 309,310,311,314, Pierre's Si pressuring controling crystal oscillating circuit that decoupling capacitor 316 constitutes.
Fig. 5 is the ac equivalent circuit schematic diagram of the core of the VCXO circuit 300 among Fig. 4.
The equivalent electric circuit of Fig. 5 and the equivalent electric circuit of Fig. 3 are basic identical.
Among Fig. 5, the equivalent capacity of the capacitor 304 in capacitor 501 corresponding diagram 4, capacitor 502 corresponding capacitors 302, variable capacitor 503 corresponding variable capacitance diodes 303, transistor 504 corresponding driver transistors 322, capacitor 505 corresponding capacitors 306.Different is the capacitor that capacitor 501,505 is selected the NTC material for use.
The load capacitance of crystal 5 06 equals capacitor 502 and the variable capacitor 503 back resulting electric capacity afterwards of connecting with capacitor 505 again of connecting with capacitor 501 in parallel, except variable capacitor 503, capacitor 501,505 select the capacitor of NTC material for use, the appearance value of the capacitor of NTC material can and reduce along with the temperature rising, along with temperature descends and raises, capacitor 502 adopts the almost capacitor of the NPO of zero temp shift (C0G) material, total load capacitance of crystal 5 06 raises along with temperature and reduces like this, the reduction of load capacitance will cause the frequency of oscillation of VCXO to raise, the characteristic that this just in time can compensated crystal descends with temperature rising frequency; Total load capacitance of opposite crystal 5 06 descends along with temperature and raises, and the rising of load capacitance will cause the frequency of oscillation of VCXO to descend, and this just in time can compensated crystal descend and the characteristic of frequency rising with temperature.If the NTC capacitor 501,505 by selecting suitable material and appearance value for use, the range of linearity that just basic energy compensated crystal temperature is floated, thereby the temperature frequency characteristic of raising VCXO circuit.
Fig. 6 is the circuit diagram according to the VCXO of the employing Pierre Si structure of second embodiment of the invention.
This VCXO circuit 300 and the difference of the VCXO circuit 300 of Fig. 4 be the two ends of the crystal 3 05 in the accumulator 3001 in parallel a NTC capacitor 323.
Fig. 7 is the ac equivalent circuit schematic diagram of the core of the VCXO circuit 300 among Fig. 6.
The equivalent electric circuit of Fig. 7 and the equivalent electric circuit of Fig. 5 are basic identical, and difference has been to increase the electric capacity 507 at the two ends that are connected in parallel on crystal 5 06, capacitor 507 corresponding capacitors 323, and capacitor 507 is selected the capacitor of NTC material equally for use
Among Fig. 7, the load capacitance of crystal 5 06 equal capacitor 502 and variable capacitor 503 backs in parallel connect with capacitor 501 connect with capacitor 505 more afterwards resulting electric capacity again with capacitor 507 electric capacity that obtain at last in parallel, except variable capacitor 503, capacitor 501,505,507 select the capacitor of NTC material for use, capacitor 502 adopts the almost capacitor of the NPO of zero temp shift (C0G) material, total load capacitance of crystal 5 06 raises along with temperature and reduces like this, the reduction of load capacitance will cause the frequency of oscillation of VCXO to raise, the characteristic that this just in time can compensated crystal descends with temperature rising frequency; Total load capacitance of opposite crystal 5 06 descends along with temperature and raises, and the rising of load capacitance will cause the frequency of oscillation of VCXO to descend, the characteristic that this just in time can compensated crystal raises with the temperature droping frequency.As long as the capacitor 501,505,507 of the NTC material by selecting suitable material and appearance value for use, the compensated crystal temperature range of linearity of floating substantially preferably just, thus improve the temperature frequency characteristic of VCXO circuit.
Fig. 8 is that the electric capacity of NTC capacitor of different materials is with the performance plot of temperature.
Can learn that from the temperature characteristics figure of the NTC capacitor of Fig. 8 the appearance value of the electric capacity of these materials reduces along with the rising of temperature, raises along with the reduction of temperature, presents the characteristic of negative temperature coefficient.Wherein the temperature coefficient of U2J material be-750ppm+/-120ppm/ ℃, relatively be fit to the temperature-compensating of crystal oscillator.
Therefore, according to the above embodiment of the present invention can select for use temperature coefficient be-750ppm+/-the NTC capacitor of the U2J material of 120ppm/ ℃, the i.e. capacitor of N750 type.
Fig. 9 is the frequency temperature drift characteristic according to the VCXO circuit 300 of second embodiment of the invention, and wherein capacitor 304,306,323 (corresponding to the capacitor 501,505,507 of Fig. 7) is selected the capacitor of the N750 type of U2J material for use.
Comparison diagram 9 and Fig. 1, as can be seen, according to the frequency temperature range of drift of the VCXO circuit 300 of second embodiment of the invention+/-5ppm about, the frequency temperature range of drift+15ppm of VCXO circuit 100 that is far smaller than prior art is to-20ppm.
The example of the VCXO that above reference is concrete describes the present invention in detail, but the invention is not restricted to the concrete circuit form among Fig. 4-7.Key element of the present invention is exactly to realize comprising the temperature-compensating such as the various crystal oscillating circuit types of VCXO circuit with the NTC capacitor.Apparently, the present invention goes for common crystal oscillator, VCXO, temp. compensation type crystal oscillator, the thermostatic control formula crystal oscillator that International Electrotechnical Commission (IEC) is classified, and improves or further improve its temperature frequency characteristic.Apparently, the exciting unit of the VCXO circuit among Fig. 4 can be to realize that with transistor, metal-oxide-semiconductor or inverter type can be to examine BZ, Pierre Si or other types.
Though illustrated and described the example embodiment of being considered of the present invention, but it will be appreciated by those skilled in the art that, along with development of technology, can make various changes and revise and can replace its element and not deviate from true scope of the present invention with equivalent.
Claims (10)
1. crystal oscillator that possesses temperature-compensating, described crystal oscillator comprises crystal, it is characterized in that:
In described crystal oscillator, a plurality of capacitors that form the load capacitance of described crystal adopt one of at least the NTC capacitor to realize.
2. crystal oscillator as claimed in claim 1 is characterized in that also comprising: a NTC capacitor in parallel is connected in parallel on the two ends of described crystal.
3. crystal oscillator as claimed in claim 1 or 2, wherein said crystal oscillator are one of common crystal oscillator, VCXO, temp. compensation type crystal oscillator, thermostatic control formula crystal oscillator.
4. crystal oscillator as claimed in claim 3, wherein when described crystal oscillator is VCXO, the exciting unit of pressuring controling crystal oscillating circuit is to realize with one of following person: transistor, metal-oxide-semiconductor and inverter.
5. crystal oscillator as claimed in claim 4, wherein said pressuring controling crystal oscillating circuit are one of following array structure persons: examine BZ structure and Pierre's Si structure.
6. crystal oscillator as claimed in claim 1, the temperature coefficient of the material of wherein said NTC capacitor be 750ppm+/-120ppm/ ℃.
7. VCXO that possesses temperature-compensating, described VCXO comprises:
First circuit, described first circuit comprises:
Crystal;
First capacitor, an end ground connection of described first capacitor;
Second capacitor is connected with an end of described first capacitor and described crystal;
The 3rd capacitor is connected with the other end of described crystal, the other end ground connection of described the 3rd capacitor, and wherein said first capacitor, described second capacitor and described the 3rd capacitor are as the load of described crystal; And
Variable capacitance diode, an end are connected on the connected node of described first capacitor and described second capacitor, other end ground connection, and wherein automatic frequency control signal is input to the connected node of described first capacitor and described second capacitor; And
Second circuit is used to be provided with the offset operation condition of described VCXO, forms the feedback loop of described first circuit, excitation and amplify oscillator signal, and export the output signal of described VCXO,
It is characterized in that:
In described VCXO, form and one of at least adopt the NTC capacitor to realize in second capacitor of load capacitance of described crystal and the 3rd capacitor.
8. VCXO as claimed in claim 7 is characterized in that also comprising: a NTC capacitor in parallel is connected in parallel on the two ends of described crystal.
9. VCXO as claimed in claim 7, the exciting unit of wherein said second circuit are to realize with one of following person: transistor, metal-oxide-semiconductor and inverter.
10. VCXO as claimed in claim 7, the temperature coefficient of the material of wherein said NTC capacitor be 750ppm+/-120ppm/ ℃.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN200910253251A CN101764571A (en) | 2009-12-11 | 2009-12-11 | Crystal oscillator with temperature compensation |
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| Application Number | Priority Date | Filing Date | Title |
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| CN200910253251A CN101764571A (en) | 2009-12-11 | 2009-12-11 | Crystal oscillator with temperature compensation |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103716042A (en) * | 2013-12-26 | 2014-04-09 | 北京无线电计量测试研究所 | Temperature compensation method used for simulating temperature compensated crystal oscillator |
| CN107491190A (en) * | 2017-09-07 | 2017-12-19 | 青岛罗博数码科技有限公司 | A kind of electromagnetic touch pen and its application method |
| CN111010088A (en) * | 2019-12-04 | 2020-04-14 | 展讯通信（上海）有限公司 | Data processing apparatus |
| CN113904626A (en) * | 2021-11-24 | 2022-01-07 | 成都世源频控技术股份有限公司 | High-stability crystal oscillator circuit and implementation method |
| CN114545998A (en) * | 2022-04-27 | 2022-05-27 | 成都世源频控技术股份有限公司 | Self-adaptive protection temperature control circuit of constant temperature crystal oscillator and implementation method |
-
2009
- 2009-12-11 CN CN200910253251A patent/CN101764571A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103716042A (en) * | 2013-12-26 | 2014-04-09 | 北京无线电计量测试研究所 | Temperature compensation method used for simulating temperature compensated crystal oscillator |
| CN103716042B (en) * | 2013-12-26 | 2016-09-21 | 北京无线电计量测试研究所 | A kind of temperature compensation for crystal oscillator of analog temperature compensation |
| CN107491190A (en) * | 2017-09-07 | 2017-12-19 | 青岛罗博数码科技有限公司 | A kind of electromagnetic touch pen and its application method |
| CN107491190B (en) * | 2017-09-07 | 2020-04-03 | 青岛罗博数码科技有限公司 | Electromagnetic touch pen and use method thereof |
| CN111010088A (en) * | 2019-12-04 | 2020-04-14 | 展讯通信（上海）有限公司 | Data processing apparatus |
| CN113904626A (en) * | 2021-11-24 | 2022-01-07 | 成都世源频控技术股份有限公司 | High-stability crystal oscillator circuit and implementation method |
| CN114545998A (en) * | 2022-04-27 | 2022-05-27 | 成都世源频控技术股份有限公司 | Self-adaptive protection temperature control circuit of constant temperature crystal oscillator and implementation method |
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Application publication date: 20100630 |