CN106603068A - Temperature compensating system of temperature compensated crystal oscillator - Google Patents
Temperature compensating system of temperature compensated crystal oscillator Download PDFInfo
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- CN106603068A CN106603068A CN201611129554.7A CN201611129554A CN106603068A CN 106603068 A CN106603068 A CN 106603068A CN 201611129554 A CN201611129554 A CN 201611129554A CN 106603068 A CN106603068 A CN 106603068A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L1/00—Stabilisation of generator output against variations of physical values, e.g. power supply
- H03L1/02—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only
- H03L1/022—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature
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Abstract
The invention discloses a temperature compensating system of a temperature compensated crystal oscillator. The system adopts the sum of sine functions to conduct fitting on the temperature compensating voltages. Compared with polynomial, with the same number of parameters, the sum of sine functions has abundant high-order term information. Compared with the Fourier function, though the 2 fitting methods contain high-order polynomial information, the sum of sine functions has inconsistent polynomial distribution (when n is not equal to infinite), which is to say when the number of parameters is limited, the fitted curve is inconsistent, and the sum of sine functions has higher temperature compensating precision. Also, experiments show that the sum of sine functions is more applicable to AT-cut quartz crystal.
Description
Technical field
The invention belongs to crystal oscillator technologies field, more specifically, is related to a kind of crystal oscillator
The temperature compensation system of (Temperature Compensate Crystal Oscillator, hereinafter referred to as TCXO), for changing
Kind temperature-compensating, improves the temperature stability of crystal oscillator output frequency.
Background technology
Crystal oscillator is widely used in electronics and information industry, and accurate crystal oscillator is to communication, electronic machine, aviation
The technology development in the fields such as space flight, defence and military plays an important role.
With the change of ambient temperature, crystal oscillator output frequency can occur drift.This output frequency becomes with temperature
The situation of change is as shown in figure 1, generally define this figure for frequency-temperature characteristics.
In order to improve the frequency-temperature characteristic of agitator, people employ many compensatory approaches, wherein, computer compensation crystal
Agitator (Microcomputer Compensated Crystal Oscillator, abbreviation MCXO) is exactly one of them.Its
Thinking is, in different temperature spots, the different voltages of loading on the load varactor of crystal oscillator, in order to by crystal
Oscillator output frequencies are withdrawn into fixed value, and generally name on-load voltage now is offset voltage.Offset voltage is with temperature
The curve of change, as shown in Figure 2.Compensating curve is imported into MCXO, during work, MCXO with compensating curve as foundation, according to temperature
The temperature information that sensor is obtained exports corresponding offset voltage, so as to reach the purpose of amendment crystal oscillator output frequency.
But the sampled point of compensating curve is limited, and in such as Fig. 2, the sampling of acquisition is exactly tested in position shown in square frame
Point.For the position between sampled point, (MQ Li, XH Huang, " A novel can be filled using the method for straightway interpolation
microcomputer temperature-compensating method for an overtone crystal
oscillator”,IEEE transaction on ferroelectrics and frequency control,vol.52,
No.11,pp.1919-1922,2005).The method of other fittings may also be employed to fill up between sampled point and sampled point
Space, to improve precision.MAS6279, MAS6270 that for example Micro Analog Systems companies produce is intended using multinomial
The space for closing interpolation to fill up between sampled point and sampled point.Be fitted i.e. using polynomial function base, and be 5 order polynomials or
3 order polynomial of person.
The form of 3 order polynomials is：
F (x)=a0+a1x+a2x2+a3x3 (1)
The form of 5 order polynomials is：
F (x)=a0+a1x+a2x2+a3x3+a4x4+a5x5 (2)
Wherein, ambient temperatures of the x for crystal oscillator, f (x) are the offset voltage of output.Polynomial number of times it is higher its
Parameter (coefficient a0～am) also more.Meanwhile, adopt higher number of times, it is clear that its precision is higher.Because if high-order term is
If number is 0, high-order moment just deteriorates to the form of polynomial of lower degree.For example in 5 order polynomials, if a4、a5For 0, just move back
Turn to the form of 3 order polynomials.In fact, 5 order polynomials are that, comprising 3 order polynomials, so number of times is higher, precision is higher.
But number of times is higher, its parameter is also more.When by compensation system chip, it is desirable to which parameter is more few better.Example
As MAS6279, MAS6270 that Micro Analog Systems companies produce even have ignored 2 item a2.Namely exist
The contradiction that number of parameters is vied each other with compensation precision, the i.e. more precision of parameter are higher.How as far as possible few parameter is used, obtained more
High precision, is that the temperature compensation system of crystal oscillator needs the problem for solving.
At on 03 25th, 2015, announce, application publication number was announced for the Chinese invention patent application of CN104467816A
A kind of " temperature compensation system of crystal oscillator ", is fitted using fourier function base, obtains the parameter of function base,
Parameter of the ARM controlling unit according to function base, is calculated compensating curve, and when in use, ARM controlling unit passes through temperature sensing
Device obtains Temperature of Warm Case, then with compensating curve as foundation, searches offset voltage, and compensated voltage-drop loading according to Temperature of Warm Case
To on the load varactor of VCXO, crystal oscillator output frequency is corrected." the crystalline substance of the public announcement of a patent application
The temperature compensation system of oscillation body device " improves the precision of temperature-compensating relative to existing fitting of a polynomial.However, same
In the case of parameter, need further to improve temperature-compensating precision.
The content of the invention
It is an object of the invention to overcome the deficiencies in the prior art, there is provided a kind of temperature compensation system of crystal oscillator,
With equivalent parameters number, higher temperature compensation precision is obtained, obtain higher temperature-compensating precision, shake so as to further improve
Swing the temperature stability of device output frequency.
For achieving the above object, the temperature compensation system of crystal oscillator of the present invention, including VCXO,
Temperature sensor, ARM controlling unit；
In use, control incubator to specific temperature spot, PC read the temperature of temperature sensor collection by ARM controlling unit
Case temperature is the ambient temperature of VCXO, while reading output frequency by cymometer；PC passes through ARM controlling unit
Output offset voltage is on the load varactor of VCXO so that output frequency is maintained at setting value；
Change Temperature of Warm Case successively, and export offset voltage and compensate, so obtain one group of temperature-offset voltage number
According to；
Characterized in that, PC is entered with the form of SIN function sum according to described one group of temperature-offset voltage data
Row fitting, obtains the parameter of function base, is then fed into ARM controlling unit；Parameter of the ARM controlling unit according to function base, calculates
It is compensated curve；Described SIN function sum is：
F (x)=a1sin(b1x+c1)+a2sin(b2x+c2)+…+an sin(bnx+cn)
Wherein, x for crystal oscillator ambient temperature, F (x) be output offset voltage, a1、b1、c1, a2、b2、c2, an、
bn、cnThe parameter of function base, item numbers of the n for SIN function；
When in use, ARM controlling unit obtains Temperature of Warm Case by temperature sensor, then with compensating curve as foundation,
Offset voltage is searched according to Temperature of Warm Case, and compensated voltage-drop loading is on the load varactor of VCXO,
Amendment crystal oscillator output frequency.
The object of the present invention is achieved like this.
The present invention carries out the fitting of temperature-compensated voltage in the form of SIN function sum, compared to polynomial form,
The form of SIN function sum, under equivalent parameters number, high-order term information is more rich.Compare with fourier function, although two kinds
Approximating method all includes high-order moment information, but its polynomial distribution (in n ≠ ∞) is inconsistent.I.e. in parameter
In the case that number is limited, matched curve is inconsistent, and SIN function sum has higher temperature-compensating precision.Meanwhile,
Experiment shows that the form of SIN function sum is more applicable for AT and cuts quartz crystal.
Description of the drawings
Fig. 1 is the frequency-temperature characteristics figure of crystal oscillator；
Fig. 2 is the curve synoptic diagram that crystal oscillator offset voltage is varied with temperature；
Fig. 3 is a kind of theory diagram of specific embodiment of crystal oscillator temperature compensation system；
Fig. 4 is the control curve that multinomial is compensated with Fourier in existing crystal oscillator temperature compensation system
Figure；
Fig. 5 is the control curve figure that crystal oscillator temperature compensation system of the present invention is compensated with fitting of a polynomial.
Specific embodiment
Below in conjunction with the accompanying drawings the specific embodiment of the present invention is described, so as to those skilled in the art preferably
Understand the present invention.Requiring particular attention is that, in the following description, when known function and design detailed description perhaps
When can desalinate the main contents of the present invention, these descriptions will be ignored here.
The present invention devises one kind equivalent parameters number, obtains the temperature-compensating of the crystal oscillator of higher compensation precision
System.Using the system, compensation precision can be improved, so as to further improve crystal in the case of using equivalent parameters number
The temperature stability of oscillator output frequencies.
SIN function can expand into following progression form：
Function SIN function sum form is represented by：
F (x)=a1sin(b1x+c1)+a2sin(b2x+c2)+…+an sin(bnx+cn) (4)
(3) are brought into (4) to obtain：
Several with binomial theorem expansion power level, arrangement is obtained
Further abbreviation is
As can be seen here, the form of SIN function sum can be expressed as polynomial form.Thus, the shape of SIN function sum
Formula may also be used for being fitted compensating curve.Compared to polynomial form, the form of SIN function sum, under equivalent parameters number,
High-order term information is more rich.Compare with fourier function, although two kinds of approximating methods all include high-order moment information, but its
Polynomial distribution (in n ≠ ∞) is inconsistent.I.e. in the case where number of parameters is limited, matched curve is inconsistent
's.Experiment shows that the form of SIN function sum is more applicable for AT and cuts quartz crystal.
Fig. 3 is a kind of theory diagram of specific embodiment of crystal oscillator temperature compensation system.
In the present embodiment, as shown in figure 3, VCXO is VCXO, 18B20 is temperature sensor, ARM controls
Unit uses the STM32F103RCT6 of ST Microelectronics.Device within dotted line is ARM controlling unit, voltage-controlled crystalline substance
Oscillation body device and temperature sensor are positioned in incubator, and ARM controlling unit is real with PC (personal computer) by USB transmission line
Now communicate.
When the temperature compensation system of crystal oscillator of the present invention works, temperature can be read by PC control control ARM units
The temperature information of degree sensor 18B20, while the offset voltage of VCXO can also be controlled, to regulate and control output frequency fout, while
Control voltage value is read in real time can at PC ends, the characteristics of so our compensation schemes have real-time.First regulate and control incubator to arrive
Specific temperature spot, in this temperature spot, reads output frequency by cymometer, regulates and controls the voltage-controlled magnitude of voltage of VCXO so that output
Frequency is setting value, and these data are the offset voltage value of corresponding temperature point.Change Temperature of Warm Case, that is, obtain one group of temperature ---
Offset voltage data.
To these data, it is fitted with fourier function base, is calculated the parameter of function base.Finally, parameter is believed
Breath input ARM controlling unit.ARM controlling unit based on parameter, by being calculated compensating curve.During use, by temperature
Degree sensor 18B20 obtains temperature information, and ARM controls list with compensating curve as foundation, according to temperature lookup offset voltage, will mend
Voltage-drop loading is repaid on VCXO VCXO varactors, so as to realize compensating the purpose of output frequency.
Fig. 4 is the control curve that multinomial is compensated with Fourier in existing crystal oscillator temperature compensation system
Figure.
The effect that Fourier compensates is as shown in Figure 4.In Fig. 4, the fitting of fourier function base uses 6 parameters, i.e.,：
F (x)=a0+a1cos(ωx)+b1sin(ωx)+a2cos(2ωx)+b2sin(2ωx) (8)
Wherein, x for VCXO ambient temperature, f (x) be output offset voltage, ω, a0、a1、a2、b1、b2
To need the parameter of fitting.
5 order polynomials that fitting of a polynomial is adopted, and 6 parameters, i.e.,
F (x)=a0+a1x+a2x2+a3x3+a4x4+a5x5 (9)
Wherein, a0、a1、a2、a3、a4、a5To need the parameter of fitting.
Actual experiment result shows：In the case of same 6 parameter, in-30 -+60 DEG C of temperature ranges, using Fourier
Function base fitting frequency temperature side-play amount be ± 0.2799ppm, and adopt 5 order polynomials fitting frequency temperature side-play amount for
±0.5249ppm.Obviously it is fitted using fourier function base, its compensation precision is higher than fitting of a polynomial.
The effect of compensation, as shown in Figure 5.In Fig. 5, SIN function sum form uses 6 parameters, i.e.,
F (x)=a1sin(b1x+c1)+a2sin(b2x+c2) (10)
5 order polynomials that fitting of a polynomial is adopted, and 6 parameters, i.e.,
F (x)=a0+a1x+a2x2+a3x3+a4x4+a5x5 (11)
Actual experiment result shows：In the case of same 6 parameter, in-30 -+60 DEG C of temperature ranges, using sinusoidal letter
The frequency temperature side-play amount of number sum form fitting is ± 0.1400ppm, and adopts the frequency temperature skew of 5 order polynomials fitting
Measure as ± 0.5249ppm.Obviously it is fitted using SIN function sum form, its compensation precision not only compares fitting of a polynomial
Height, but also be fitted than fourier function base high.
Although being described to illustrative specific embodiment of the invention above, in order to the technology of the art
Personnel understand the present invention, it should be apparent that the invention is not restricted to the scope of specific embodiment, the common skill to the art
For art personnel, as long as various change is in appended claim restriction and the spirit and scope of the present invention for determining, these
Change is it will be apparent that all utilize the innovation and creation of present inventive concept in the row of protection.
Claims (2)
1. the temperature compensation system of crystal oscillator, including VCXO, temperature sensor, ARM controlling unit；
In use, control incubator to specific temperature spot, PC read the incubator temperature of temperature sensor collection by ARM controlling unit
Degree is the ambient temperature of VCXO, while reading output frequency by cymometer；PC is exported by ARM controlling unit
Offset voltage is on the load varactor of VCXO so that output frequency is maintained at setting value；
Change Temperature of Warm Case successively, and export offset voltage and compensate, so obtain one group of temperature-offset voltage data；
Characterized in that, PC is intended with the form of SIN function sum according to described one group of temperature-offset voltage data
Close, obtain the parameter of function base, be then fed into ARM controlling unit；ARM controlling unit is calculated according to the parameter of function base
Compensating curve；Described SIN function sum is：
F (x)=a1 sin(b1x+c1)+a2 sin(b2x+c2)+…+an sin(bnx+cn)；
When in use, ARM controlling unit obtains Temperature of Warm Case by temperature sensor, then with compensating curve as foundation, according to
Temperature of Warm Case searches offset voltage, and compensated voltage-drop loading is on the load varactor of VCXO, amendment
Crystal oscillator output frequency..
2. compensation system according to claim 1, it is characterised in that the form with SIN function sum is intended
Close, use 6 parameters, i.e.,：
F (x)=a1 sin(b1x+c1)+a2 sin(b2x+c2)。
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108732380A (en) * | 2018-05-25 | 2018-11-02 | 电子科技大学 | A kind of trigonometric function temperature-compensation method |
| CN108875142A (en) * | 2018-05-25 | 2018-11-23 | 电子科技大学 | A kind of unlimited order easily realizes temperature compensation system |
| CN112394232A (en) * | 2020-11-18 | 2021-02-23 | 刘�东 | Piezoelectric crystal, inductor equivalent parameter and capacitance value measuring method |
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| CN104467816A (en) * | 2014-12-29 | 2015-03-25 | 电子科技大学 | Temperature compensation system of crystal oscillator |
| CN105426585A (en) * | 2015-11-05 | 2016-03-23 | 浙江大学 | Potato sprouting early warning method based on sine function fitting method |
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| CN102506760A (en) * | 2011-11-18 | 2012-06-20 | 东南大学 | Phase compensating method in object surface outline measurement |
| CN104467816A (en) * | 2014-12-29 | 2015-03-25 | 电子科技大学 | Temperature compensation system of crystal oscillator |
| CN105426585A (en) * | 2015-11-05 | 2016-03-23 | 浙江大学 | Potato sprouting early warning method based on sine function fitting method |
Non-Patent Citations (1)
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| 庞晓波: "《经济预测与决策》", 31 December 1990 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108732380A (en) * | 2018-05-25 | 2018-11-02 | 电子科技大学 | A kind of trigonometric function temperature-compensation method |
| CN108875142A (en) * | 2018-05-25 | 2018-11-23 | 电子科技大学 | A kind of unlimited order easily realizes temperature compensation system |
| CN112394232A (en) * | 2020-11-18 | 2021-02-23 | 刘�东 | Piezoelectric crystal, inductor equivalent parameter and capacitance value measuring method |
| CN112394232B (en) * | 2020-11-18 | 2024-05-10 | 刘�东 | Piezoelectric crystal, inductor equivalent parameter and capacitance measuring method |
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Application publication date: 20170426 |