A kind of crystal oscillator automatic temperature compensation systemTechnical field
The invention belongs to crystal oscillator technologies fields, more specifically, are related to a kind of crystal oscillator automatic temperature-adjustingCompensation system.
Background technology
Crystal oscillator (Temperature Compensate Xtal (crystal) Oscillator, TCXO) is answered extensivelyFor the industry of electronic information field, play a part of in electronic system " heart ".Communication, electronic instrument, aviation in recent yearsThe development of the technologies such as space flight, defence and military proposes increasingly higher demands to the accuracy of crystal oscillator and stability.
General crystal oscillator is with the variation of environment temperature, and output frequency will appear drift, with temperature-frequency spyProperty indicate, can be approximated to be a cubic curve, as：
F (T)=a3(T-T0)3+a1(T-T0)+a0 (1)
Wherein, a3It is coefficient entry three times, a1It is coefficient of first order item, a0It is T0When frequency of oscillation, T0It is reference temperature.
For common voltage controlled oscillator (Voltage Controlled Xtal (crystal) Oscillator, VCXO)Linear gain characteristics can approximation be expressed as follows：
F (VC)=- G (VC-VC0)+f0 (2)
Wherein, G is the gain of VCXO, and VC is the control voltage of VCXO, VC0It is the input voltage at the voltage-controlled end of VCXO, f0It isInput is VC0When frequency of oscillation.
So, the equation as the voltage VC (T) of compensation crystal oscillator temperature characterisitic can be expressed as：
VC (T)=A3(T-T0)3+A1(T-T0)+A0 (3)
At this point, A3=a3/ G, A1=a1/ G, A0Be temperature be T0When offset voltage.Usually definition is painted according to this variationThe curve of system is frequency-temperature characteristic curve.Fig. 1 is frequency-temperature characteristic curve exemplary plot.
In order to improve the frequency temperature drift characteristic of crystal oscillator, people use many methods.Existing frequently-used doesMethod is almost all based on the open loop compensation circuit built using temperature sensor, by the crystal oscillator under different temperature spotsTemperature frequency variation, be converted to corresponding voltage, be loaded on the load varactor of oscillator, in order to by oscillatorOutput frequency stablize in fixed value, usually the on-load voltage of name at this time is offset voltage.Fig. 2 is the crystalline substance based on open loop approachOscillation body device temperature compensation system structure chart.As shown in Fig. 2, in the crystal oscillator temperature compensation system based on open loop approach,Environment temperature is acquired by temperature sensor, then calculates required offset voltage, obtains the corresponding data of temperature-compensation voltage,It finally is fitted to a temperature compensation curve for carrying high-order component using algorithm, achievees the purpose that temperature-compensating.
This open-loop compensation mode during the output of frequency there are apparent temperature hysteresis phenomenon, and compensated curveSampled point be limited, the curve that offset voltage varies with temperature is filled by the interpolation of function, it may appear that actualOffset voltage and the not quite identical situation of required offset voltage, this will result in the unstable of output frequency curve and by a small marginShaking.And in calculating process, the offset voltage of existing system can pass through the improvement offset voltage of interpolating function；CertainlyThe modes such as Fourier function may be used, improve the exponent number of compensated curve polynomial function, make matched curve closer to practical songLine.But since calculating process is more complicated, inevitably there is delay so that the real-time of offset voltage is affected,To influence the compensation precision of temperature compensating crystal oscillator.
Invention content
It is an object of the invention to overcome the deficiencies of the prior art and provide a kind of crystal oscillator auto thermal compensation systemsSystem, solves the problems, such as temperature hysteresis, to improve the real-time and accuracy of crystal oscillator auto thermal compensation.
For achieving the above object, crystal oscillator temperature compensation system of the present invention includes high-low temperature test chamber, frequencyMeter, D.C. regulated power supply, programmable DC regulated power supply and host computer, wherein：
Place Voltage Controlled Crystal Oscillator to be compensated inside high/low temperature experimental box, high/low temperature experimental box according to host computer temperatureRegulating command adjusts its temperature；
Frequency meter measures the output frequency of Voltage Controlled Crystal Oscillator to be compensated, is sent to host computer；
D.C. regulated power supply provides supply voltage V to Voltage Controlled Crystal Oscillator to be compensatedCC；
Programmable DC regulated power supply is used to provide control voltage to Voltage Controlled Crystal Oscillator to be compensated, and programmable DC is steadyFor voltage source in the reset signal for receiving host computer, control voltage is nominal control voltage V0；Receiving host computerWhen controlling voltage regulating command, control voltage is adjusted；After receiving the inquiry instruction of host computer, uploaded to host computerCurrent control voltage V (T)；
Host computer is according to Voltage Controlled Crystal Oscillator operating ambient temperature range [T to be compensatedmin,Tmax] to high/low temperature experimental boxTemperature adjustment instructions are sent, successively from minimum temperature TminIt is adjusted to maximum temperature Tmax；Host computer is sending temperature adjusting every timeInstruction sends reset instruction simultaneously, to programmable DC regulated power supply, and control voltage is made to restore to V0；Host computer receives frequency meterThe output frequency of upload calculates the target frequency f with Voltage Controlled Crystal Oscillator to be compensated0Frequency deviation f (T)=f (T)-f0And record, it is then sent to programmable DC regulated power supply and controls voltage regulating command, the output frequency that monitoring frequency meter is sent,When the output frequency that frequency meter uploads is equal to target frequency f0When, send inquiry instruction, record to programmable DC regulated power supplyThe control voltage V (T) that programmable DC regulated power supply is replied is calculated and is recorded current corresponding offset voltage Δ V (T)=V(T)-V0, V0Indicate nominal control voltage；Host computer is by temperature range [Tmin,Tmax] in all frequency deviation f (T) and mendIt repays voltage Δ V (T) integration and obtains frequency departure-offset voltage tables of data, and stored to Voltage Controlled Crystal Oscillator to be compensatedOffset voltage generating means.
Crystal oscillator temperature compensation system of the present invention, including high-low temperature test chamber, frequency meter, D.C. regulated power supply, canD.C. regulated power supply, host computer are programmed, places Voltage Controlled Crystal Oscillator to be compensated inside high/low temperature experimental box, frequency meter measurement waits forThe output frequency of Voltage Controlled Crystal Oscillator is compensated, D.C. regulated power supply provides supply voltage to Voltage Controlled Crystal Oscillator to be compensated,PC control high/low temperature experimental box is adjusted into trip temperature, and programmable DC voltage of voltage regulation is controlled under Current Temperatures to be compensatedVoltage Controlled Crystal Oscillator, which provides appropriate voltage, makes the output frequency of offset voltage Voltage Controlled Crystal Oscillator to be compensated be equal to target frequencyRate obtains frequency departure-offset voltage tables of data and incites somebody to action to obtain corresponding frequency departure and offset voltage under different temperaturesIt is stored to the offset voltage generating means of Voltage Controlled Crystal Oscillator, to realize that the automatic temperature-adjusting to Voltage Controlled Crystal Oscillator is mendedRepay control.
The present invention has following technology excellent compared with the existing crystal oscillator temperature compensation system based on open loop approachPoint：
1) temperature in use sensor is not needed, sluggishness during generating offset voltage change output frequency is effectively improvedPhenomenon, it is easier to realize that real-time high-precision compensates,；
2) framework mode is compensated using closed loop feedback, frequency departure-offset voltage tables of data is that direct acquisition comes out, the error of offset voltage is reduced from principle, makes output frequency within the scope of wider temperature, it is more stable more accurate.
Description of the drawings
Fig. 1 is frequency-temperature characteristic curve exemplary plot；
Fig. 2 is the crystal oscillator temperature compensation system structure chart based on open loop approach；
Fig. 3 is the structure chart of crystal oscillator temperature compensation system of the present invention；
Fig. 4 is offset voltage generating means structure chart in the present embodiment.
Specific implementation mode
The specific implementation mode of the present invention is described below in conjunction with the accompanying drawings, preferably so as to those skilled in the artUnderstand the present invention.Requiring particular attention is that in the following description, when known function and the detailed description of design perhapsWhen can desalinate the main contents of the present invention, these descriptions will be ignored herein.
Embodiment
Fig. 3 is the structure chart of crystal oscillator temperature compensation system of the present invention.As shown in figure 3, crystal oscillator of the present inventionTemperature compensation system includes high-low temperature test chamber 1, frequency meter 2, D.C. regulated power supply 3, programmable DC regulated power supply 4, upperMachine 5.
Voltage Controlled Crystal Oscillator to be compensated is placed in 1 inside of high/low temperature experimental box, and high/low temperature experimental box 1 is according to host computer 5Temperature adjustment instructions adjust its temperature.
Frequency meter 2 measures pressure to be compensated for being monitored in real time to the output frequency of Voltage Controlled Crystal Oscillator to be compensatedThe output frequency for controlling crystal oscillator, is sent to host computer 5.
D.C. regulated power supply 3 provides supply voltage V to Voltage Controlled Crystal Oscillator to be compensatedCC。
Programmable DC regulated power supply 4 is used to provide control voltage, programmable DC to Voltage Controlled Crystal Oscillator to be compensatedFor regulated power supply 4 when receiving the reset signal of host computer 5, control voltage is nominal control voltage V0；It is upper receivingWhen the control voltage regulating command of machine 5, control voltage is adjusted；After the inquiry instruction for receiving host computer 5, to upperMachine 5 uploads current control voltage V (T).
Host computer 5 is according to Voltage Controlled Crystal Oscillator operating ambient temperature range [T to be compensatedmin,Tmax] tested to high/low temperatureCase 1 sends temperature adjustment instructions, successively from minimum temperature TminIt is adjusted to maximum temperature Tmax；Host computer 5 is sending temperature every timeRegulating command sends reset instruction simultaneously, to programmable DC regulated power supply 4, and control voltage is made to restore to V0；Host computer 5 receivesThe output frequency that frequency meter 2 uploads calculates the target frequency f with Voltage Controlled Crystal Oscillator to be compensated0Frequency deviation f (T)=f (T)-f0And record, control voltage regulating command then is sent to programmable DC regulated power supply 4, monitoring frequency meter 2 is sentOutput frequency, when frequency meter 2 upload output frequency be equal to target frequency f0When, it is sent to programmable DC regulated power supply 4Inquiry instruction, the control voltage V (T) that record programmable DC regulated power supply 4 is replied are calculated and are recorded current corresponding compensation electricityPress Δ V (T)=V (T)-V0, V0Indicate nominal control voltage；Host computer 5 is by temperature range [Tmin,Tmax] in all frequencies it is inclinedPoor Δ f (T) and offset voltage Δ V (T) integration obtain frequency departure-offset voltage tables of data, store to voltage-controlled crystal (oscillator) to be compensatedThe offset voltage generating means of oscillator.
The workflow of crystal oscillator temperature compensation system of the present invention can be summarized as follows：First to high/low temperature experimental box 1Temperature setting is carried out, is then nominal control voltage V in the control voltage of Voltage Controlled Crystal Oscillator to be compensated0In the case of, it obtainsTo Current Temperatures lower frequency deviation delta f (T), then by controlling 4 adjusting control voltage of programmable DC regulated power supply, make to wait mendingThe output frequency for repaying Voltage Controlled Crystal Oscillator is target frequency f0, i.e. frequency departure is 0, and record controls voltage deviation at this time, i.e.,For offset voltage.To obtain the frequency deviation f (T) for needing to compensate and corresponding offset voltage Δ by closed feedback loopV (T) obtains a mutual corresponding tables of data of frequency departure-offset voltage, in this, as voltage-controlled by constantly changing temperatureCompensation basis in crystal oscillator actual application.
Fig. 4 is offset voltage generating means structure chart in the present embodiment.As shown in figure 4, voltage-controlled crystal (oscillator) shakes in the present embodimentThe offset voltage generating means for swinging device include that frequency departure calculates module, frequency-voltage transformation module and filter.Frequency departureComputing module is for calculating frequency departure.Frequency departure calculates module tool, and there are two working conditions：Monitoring state and compensating coefficient,In a monitoring state, when frequency departure absolute value is more than δ, frequency departure calculates module and is sent to frequency-voltage transformation moduleThen reset signal is converted to compensating coefficient, is not otherwise made any operation.Under compensating coefficient, directly frequency departure is sentTo frequency-voltage transformation module, then convert to monitoring state.Frequency-voltage transformation module is for generating offset voltage, when connecingWhen receiving reset signal, then it is 0 to enable offset voltage, when receiving frequency departure, then in frequency departure-offset voltage tables of dataMiddle lookup obtains corresponding offset voltage, then generates compensation voltage signal.Filter is filtered compensation voltage signal, obtainsTo final compensation voltage signal.
Although the illustrative specific implementation mode of the present invention is described above, in order to the technology of the artPersonnel understand the present invention, it should be apparent that the present invention is not limited to the range of specific implementation mode, to the common skill of the artFor art personnel, if various change the attached claims limit and determine the spirit and scope of the present invention in, theseVariation is it will be apparent that all utilize the innovation and creation of present inventive concept in the row of protection.