CN201515347U - Temperature frequency correcting device - Google Patents
Temperature frequency correcting device Download PDFInfo
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- CN201515347U CN201515347U CN2008200608267U CN200820060826U CN201515347U CN 201515347 U CN201515347 U CN 201515347U CN 2008200608267 U CN2008200608267 U CN 2008200608267U CN 200820060826 U CN200820060826 U CN 200820060826U CN 201515347 U CN201515347 U CN 201515347U
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Abstract
The utility model provides a temperature frequency correcting device comprising a data storage unit, a temperature frequency correcting character acquisition unit and a temperature frequency correcting unit, wherein the data storage unit is used for storing initial temperature frequency correcting character corresponding to an initial temperature; the temperature frequency correcting character acquisition unit is used for calculating an temperature frequency correcting character corresponding to a calculation temperature which continuously approximates the current temperature at a preset temperature interval beginning from the initial temperature, and obtaining the temperature frequency correcting character corresponding to the current temperature according to the temperature frequency correcting character corresponding to the calculation temperature when the calculation temperature enters the preset locking range of the current temperature; and the temperature frequency correcting unit carries out temperature frequency correction by utilizing the current temperature. Therefore, the temperature frequency correcting device can reduce the temperature frequency correcting value needed to store to the greatest extent, and simultaneously also improve the accuracy of temperature frequency compensation.
Description
Technical field
The utility model relates to electronic circuit design field, particularly the compensation technique of temperature frequency drift and the technology of obtaining of temperature correction word.
Background technology
Can both be normally or synchronous working in order to ensure all electronic devices, it is very important that accurate clock signal is provided in design of electronic circuits.Usually, described clock signal is generally can be produced by crystal oscillator (crystal oscillator), and wherein said crystal oscillator is to utilize the mechanical resonant of the oscillating crystal of piezoelectric to produce the electronic circuit of the certain frequency signal of telecommunication.This frequency can be used for timing (such as quartz watch) usually, also can be used to digital integrated circuit that clock signal is provided, and can also be used for stablizing the frequency of wireless launcher/receiver.A reason that causes clock signal to be different from design is temperature, and it may influence the running of piezoelectric and crystal oscillator.Along with variation of temperature, the frequency of crystal oscillator output can also can change thereupon.In fact, electronic equipment may be used to such as portable computer, mobile phone and electronic instrument therefore guarantee that these electronic equipments can both normally errorless work be very important under all temps environment in the environment of all temps variation.
Many modern communications equipments need the frequency of high accuracy, high stable to increase the sensitivity of radio transceiver in it such as GPS and gsm system and reduce collection/tracking time.Yet the output of crystal oscillator again and again can be drifted about along with life-span and variation of temperature, and common crystal oscillator can not provide yet and suppresses the mechanism that crystal frequency changes with environment temperature.Because harsh demand, it is impossible using low-cost independent crystal oscillator in the cellular system from the frequency tuning support of base station not.
The frequency source of wireless telecommunications system or mobile phone includes digitally controlled crystal oscillator (digitallycontrolled crystal oscillator) or temperature compensating crystal oscillator (temperature-compensated crystal oscillator).Yet the digitally controlled crystal oscillator circuit need be introduced capacitor array and carry out frequency correction in crystal oscillator.Like this, use digitally controlled crystal oscillator just to become very expensive, especially for the digitally controlled crystal oscillator of deep-submicron COMS technology.In addition, cause frequency hopping effect (frequency beating effects) possibly, thereby be difficult to satisfy the requirement of output frequency stability by the output frequency of the switching of a large amount of electric capacity in the digitally controlled crystal oscillator being adjusted crystal oscillator.
In addition, described digitally controlled crystal oscillator circuit also needs the numerical control input signal to compensate the frequency drift that is changed and caused by temperature.Generally all adopt the frequency compensation of some discrete temperature spot correspondences of storage to be worth method, i.e. look-up table (Look-up table) method in the prior art.When needs carry out temperature frequency compensation, only the frequency compensation value of Current Temperatures correspondence directly need be taken out use just passable.Yet,, may have influence on the compensation effect of whole system if obvious saltus step takes place frequency between some temperature spots.For the problems referred to above, a kind of solution is can utilize to adopt the mode of interpolation to overcome between the temperature interval, but this more complicated and compensation precision that hardware designs is become may be poor.Another kind of solution is to reduce the frequency compensation value of temperature interval with the more temperature spot correspondences of acquisition, but this will increase the capacity of the memory that is used for the storing frequencies offset, also can increase the test point quantity of temperature frequency simultaneously.
In existing temperature compensating crystal oscillator (temperature-compensated crystaloscillator), self-operated thermostatic controller generates correction voltage to guarantee that oscillator frequency is constant.Such voltage controlled temperature compensated crystal oscillator has a temperature sensor according to the proportional generation linear voltage of temperature, 3 rank linear function voltage generator and VCXOs.The output of three rank linear function voltage generators and temperature sensor is offered VCXO, described VCXO and then can carry out temperature-compensating according to the temperature frequency characteristic of use crystal.
Yet such voltage controlled temperature compensated crystal oscillator at first needs a high-quality crystal to satisfy described three rank linear compensation needs, and so high-quality crystal is very expensive, especially undersized crystal.Secondly, owing to limited the maximum output frequency of crystal oscillator, therefore also be difficult to guarantee high frequency stability and accuracy.In addition, owing to be difficult to accurately generate microvolt level aanalogvoltage, the change of the very difficult control of described voltage controlled temperature compensated crystal oscillator small frequency (such as, less than 1.0 hertz).
Therefore, demand proposing that a kind of memory capacity is low, compensation precise dose frequency-drift compensation technology and temperature correction word obtain technology urgently.
The utility model content
In view of this, the technical problem of solution of the present utility model is to provide a kind of temperature frequency correcting apparatus, and it can compensate fast, accurately to the temperature frequency drift.
In order to solve the problems of the technologies described above, according to one side of the present utility model, the utility model discloses a kind of successive approximation temperature and frequency correcting device, it comprises: data storage cell, temperature and frequency correcting word acquiring unit, frequency correction unit and frequency locking synthesis unit.Described data storage cell is used for the temperature and frequency correcting word of storing initial temperature correspondence.Described temperature and frequency correcting word acquiring unit is used to continue to obtain the temperature and frequency correcting word of accounting temperature correspondence, described accounting temperature is to begin to be spaced apart the temperature value that step-length is constantly approached to Current Temperatures one by one with predetermined temperature from initial temperature, the temperature that described Current Temperatures provides for the outside, and when described accounting temperature enters the predetermined lock-in range of described Current Temperatures, obtain the temperature and frequency correcting word of described Current Temperatures correspondence according to the temperature and frequency correcting word of described accounting temperature correspondence.Described frequency correction unit is used to utilize the temperature and frequency correcting word of described Current Temperatures that frequency control word is compensated to obtain the emending frequency control word.It is that the basis generates the desired output frequency according to the emending frequency control word that described frequency locking synthesis unit is used for the reference frequency.
Further, described frequency correction unit generates emending frequency control word FCW_new according to following formula:
FCW_new=FCW+TCW。
Wherein FCW represents frequency control word, and TCW represents the temperature and frequency correcting word.
Further, described temperature and frequency correcting word acquiring unit comprises temperature comparing unit, temperature approaches unit and temperature and frequency correcting letter lock order unit, and it is that current accounting temperature point and the Current Temperatures of initial temperature compares that wherein said temperature comparing unit is used for initial value; At comparative result is that current accounting temperature point is not when being in the lock-in range of Current Temperatures, described temperature and frequency correcting letter lock order unit utilizes the corresponding temperature and frequency correcting word of current accounting temperature point to calculate from current accounting temperature point and steps the temperature and frequency correcting word of a nearly predetermined temperature next accounting temperature point correspondence at interval towards described Current Temperatures, and described temperature approaches unit is exported to the temperature comparing unit with described next accounting temperature point as the new current accounting temperature point of lower whorl and proceeded comparison; At comparative result is current accounting temperature point when being in the predetermined lock-in range of Current Temperatures, and described temperature and frequency correcting letter lock order unit obtains the temperature and frequency correcting word of Current Temperatures correspondence according to the corresponding temperature and frequency correcting word of current accounting temperature point.
Further again, described data storage cell also stores fixed step size and fixed step size symbol table, and described fixed step size symbol table stores some sign bits of fixed step size; Wherein saidly utilize the corresponding temperature and frequency correcting word of current accounting temperature point to obtain towards the temperature and frequency correcting word that described Current Temperatures steps a nearly predetermined temperature next accounting temperature point correspondence at interval to be: from the fixed step size symbol table, obtain current accounting temperature point and approach the sign bit that described next accounting temperature is put needed fixed step size from current accounting temperature point; Giving fixed step size with the sign bit that obtains approaches described next accounting temperature and puts needed actual step size to obtain current accounting temperature point; Utilize corresponding temperature and frequency correcting word of current accounting temperature point and actual step size to obtain the corresponding temperature and frequency correcting word of described next accounting temperature point.
Further again, described fixed step size is represented the absolute difference of the temperature and frequency correcting word of adjacent temperature spot correspondence, and being separated by of described adjacent temperature spot also is described predetermined temperature interval; Described actual step size is the difference between the corresponding temperature and frequency correcting word of the current accounting temperature point temperature and frequency correcting word corresponding with next accounting temperature point of convergence target temperature.
According on the other hand of the present utility model, the invention also discloses another kind of a kind of temperature frequency correcting apparatus, it comprises: data storage cell, be used to store the ideal temperature frequency characteristics is carried out sampling analysis at interval with predetermined temperature and the primary data that obtains, described data comprise temperature and frequency correcting word, the fixed step size of initial temperature correspondence and store the fixed step size symbol table of some sign bits of fixed step size; Temperature and frequency correcting word acquiring unit, be used for obtaining the temperature and frequency correcting word of accounting temperature correspondence according to described primary data, described accounting temperature is to begin to be spaced apart the temperature value that step-length is constantly approached to Current Temperatures one by one with described predetermined temperature from initial temperature, to such an extent as to described accounting temperature can begin to approach described Current Temperatures one by one along described ideal temperature frequency characteristics with the corresponding formed matched curve of temperature and frequency correcting word from initial temperature, and exports the temperature and frequency correcting word of described accounting temperature correspondence when described accounting temperature enters the predetermined lock-in range of described Current Temperatures; With the temperature and frequency correcting unit, utilize the temperature and frequency correcting word of temperature and frequency correcting word acquiring unit output to carry out temperature and frequency correcting.
Further, the described predetermined temperature difference with the difference of temperature coverage at interval.
Further, described calculating one by one from initial temperature according to described primary data begins constantly to comprise to the temperature and frequency correcting word of the accounting temperature correspondence that Current Temperatures approaches at interval with described predetermined temperature: obtain current accounting temperature point and approach the sign bit that next accounting temperature is put needed fixed step size from the fixed step size symbol table, described next temperature spot is to step nearly predetermined temperature temperature spot at interval from current accounting temperature point towards described Current Temperatures, and the initial value of described Current Temperatures point is an initial temperature; Giving fixed step size with the sign bit that obtains approaches described next accounting temperature and puts needed actual step size to obtain current accounting temperature point; Utilize corresponding temperature and frequency correcting word of current accounting temperature point and actual step size to obtain the corresponding temperature and frequency correcting word of described next accounting temperature point; With new current accounting temperature point and the repetition aforesaid operations of described next accounting temperature point as lower whorl.
So compared with prior art, in the technical scheme that the utility model proposes, by the desired temperature and frequency correcting value of the frequency drift that adopts a kind of digital successive approximation approach to automatically lock different temperature spots, thereby reduce the temperature and frequency correcting value of required storage to greatest extent, also improved the precision of temperature frequency compensation simultaneously.
Description of drawings
Fig. 1 is the functional-block diagram of the temperature frequency compensation/means for correcting in the utility model;
Fig. 2 is the functional-block diagram of an embodiment of the temperature and frequency correcting letter lock order unit in the utility model;
Fig. 3 is the flow chart of an embodiment of the temperature and frequency correcting word acquisition methods in the utility model;
Fig. 4 is the temperature frequency performance diagram of reference frequency fR, wherein shows the temperature frequency characteristic curve after uncompensated temperature frequency characteristic curve, temperature frequency compensated curve and the compensation;
Fig. 5 is the schematic flow sheet of another embodiment of the temperature and frequency correcting word acquisition methods in the utility model;
Fig. 6 is reference frequency f
RThe temperature frequency temperature frequency performance diagram of undergoing mutation;
Fig. 7 is the mensuration flow chart of an embodiment of difference, the fixed step size of initial temperature frequency correction word, initial temperature frequency correction word in the utility model;
Fig. 8 is the calculation flow chart of an embodiment of the fixed step size symbol table in the utility model.
Embodiment
Below in conjunction with Figure of description embodiment of the present utility model is described.
An embodiment of the temperature frequency correcting apparatus that provides 100 in the utility model is provided Fig. 1.Described temperature frequency correcting apparatus 100 comprises frequency locking synthesis unit 110, frequency correction unit 130 and temperature and frequency correcting word generation unit 150.Described temperature and frequency correcting word generation unit 150 is used to generate corresponding temperature and frequency correcting word (the tempereture frequency correction word of Current Temperatures T (also can be described as assigned temperature or target temperature) of input, be called for short TCW), this temperature and frequency correcting word TCW can be to the reference frequency f under the Current Temperatures T
RTemperature frequency drift compensate/proofread and correct.Described frequency correction unit 130 is used to utilize the temperature and frequency correcting word TCW of acquisition to frequency control word (frequency control word, be called for short FCW) proofread and correct/compensate to obtain emending frequency control word (corrected frequency control word is called for short FCW_new).Described frequency locking synthesis unit 110 is used for reference frequency f
RFor the basis generates the desired output frequency f according to emending frequency control word FCW_new
OUT
Wherein, the frequency control word FCW that imports among Fig. 1 can be the frequency control signal from the outside, described reference frequency f
RCan be the simulated clock simulation clock signal, it can the occurrence frequency drift with variation of temperature.Described Current Temperatures T can be a digital temperature value that is obtained by digital temperature sensor (not shown) induction Current Temperatures, the Current Temperatures T that certain digital temperature sensor provides can not need strictness to equal actual current temperature value, described Current Temperatures T also can be by a temperature of digital temperature sensor or miscellaneous equipment appointment or a target temperature of setting, therefore also can be referred to as relative temperature, target temperature or assigned temperature.It should be noted that in addition, described Current Temperatures T, temperature and frequency correcting word TCW, frequency control word FCW and emending frequency control word FCW_new are digital signals, (such as 32,16 or 8 the binary sequence) that they are normally represented by binary sequence.
In one embodiment, described frequency locking synthesis unit 110 generates the desired output frequency f according to following formula
OUT:
f
OUT=K*FCW_new*f
R
Wherein K represents proportionality coefficient, the output frequency signal f that can obtain expecting according to proportionality coefficient K and emending frequency control signal FCW_new
OUT
In one embodiment, described frequency correction unit 130 generates emending frequency control word FCW_new according to following formula:
FCW_new=FCW+TCW。
In one embodiment, such as the frequency signal of needs generation 890MHz, described frequency control word FCW can be the binary sequence of the described frequency values of expression, and described temperature and frequency correcting word TCW can be the described reference frequency f of expression
RThe binary sequence of the frequency drift corrected value under Current Temperatures, the frequency signal of the 890MHz that obtains by emending frequency control word FCW_new just can not produce bigger frequency drift with variation of temperature like this, that is to say that the output frequency of 890MHz has obtained temperature-compensating.In another embodiment, described frequency control word FCW can change within the specific limits, and frequency control word FCW also can be used as frequency modulated signal to generate modulation output frequency f like this
OUTSuch as, needs generate frequency modulation(FM) (Frequency Modulated) signal of 890MHz～910MHz frequency range, and described frequency control word FCW can be the binary sequence of the described frequency range of expression.
Fig. 4 shows reference frequency f
RUncompensated temperature frequency characteristic curve, temperature frequency compensated curve and the temperature frequency characteristic curve after the compensation, wherein said uncompensated reference frequency has in-50 ℃ to 125 ℃ temperature ranges approximately ± frequency drift of 10ppm, and the frequency drift that the frequency drift of the output after the compensation does not more compensate output reduces greatly.As shown in Figure 4, drift compensates to temperature frequency if arbitrary temperature value (or temperature spot), just can utilize this frequency correction value all to the correspondent frequency corrected value should be arranged.Here the frequency correction value of mentioning is exactly described temperature and frequency correcting word TCW.
Please consult shown in Figure 1ly once more, described temperature and frequency correcting word generation unit 150 (also can be referred to as temperature and frequency correcting word deriving means) also includes temperature comparing unit 152, temperature approaches unit 158, temperature and frequency correcting letter lock order unit 154 and primary data memory cell 156 (also can it not being listed in the temperature and frequency correcting word generation unit sometimes).
Described data storage cell 156 stores the initial temperature frequency correction word TCW (TO) of initial temperature point TO correspondence, described temperature comparing unit 152 comparison object temperature T and current accounting temperature point Tx; At comparative result is that current accounting temperature point Tx is not when being in the lock-in range of target temperature T, described temperature and frequency correcting letter lock order unit 154 utilize the temperature and frequency correcting word TCW (Tx) of current accounting temperature point Tx correspondence calculate convergence target temperature T next accounting temperature point (such as: if T Tx, then next accounting temperature point is Tx+S; If T＜Tx, then next accounting temperature point is Tx-S, described S is the predetermined temperature interval) corresponding temperature and frequency correcting word, described temperature approaches unit 158 is exported to temperature comparing unit 152 with next accounting temperature point of convergence target temperature as current accounting temperature point Tx and is proceeded comparison; At comparative result is current accounting temperature point Tx when being in the lock-in range of target temperature T, and described temperature and frequency correcting letter lock order unit 154 obtains the temperature and frequency correcting word TCW (T) of target temperature T correspondence according to the temperature and frequency correcting word TCW (Tx) of current accounting temperature point Tx correspondence.The initial value of described current accounting temperature point Tx is initial temperature TO, and the first duration of the temperature and frequency correcting word of current accounting temperature point Tx correspondence is initial temperature frequency correction word TCW (TO).
Like this, in the utility model, do not need all to store corresponding temperature and frequency correcting word for each temperature spot, the temperature and frequency correcting word that only needs storing initial adopts the successive approximation computing just can calculate the temperature and frequency correcting word TCW (T) of target temperature T correspondence afterwards.
In a concrete example, the lock-in range of described target temperature T can be in the predetermined temperature range that comprises Current Temperatures T.In addition, the lock-in range that described accounting temperature Tx is not in Current Temperatures T also bag can comprise two kinds of situations, and promptly described accounting temperature Tx is not in the lock-in range of Current Temperatures T and T and is not in the lock-in range of Current Temperatures T and T less than Tx greater than Tx and described accounting temperature Tx.For instance, T〉Tx+S can represent that described accounting temperature Tx is not in lock-in range and T greater than Tx, T＜Tx can represent that described accounting temperature Tx is not in lock-in range and T less than Tx, and Tx ≦ T＜Tx+S can represent that described accounting temperature Tx is in lock-in range.Again for instance, T〉Tx+S can represent that described accounting temperature Tx is not in lock-in range and T greater than Tx, T＜Tx-S can represent that described accounting temperature Tx is not in lock-in range and T less than Tx, and Tx-S＜T＜Tx+S can represent that described accounting temperature Tx is in lock-in range.
In a concrete enforcement, described primary data memory cell 156 also stores fixed step size and fixed step size symbol table, described fixed step size and described fixed step size symbol table can be the digital signals of being represented by binary sequence, store sign bit (the sign bit of the fixed step size of each discrete temperature spot correspondence in the described fixed step size symbol table, be called for short SB), just can represent that such as 10 can represent to bear.Described discrete temperature spot is meant to have the predetermined temperature temperature spot of S at interval, the described predetermined temperature size of S at interval can be chosen as required and can different values be set at different Applicable temperature scopes, such as S can be 0.2 ℃ a temperature range, is 0.1 ℃ in another temperature range.This predetermined temperature interval S has reflected the temperature covering precision of fixed step size symbol table, has just reflected the temperature covering precision in the temperature frequency compensation in the utility model.Give fixed step size with the symbol of each sign bit in the described fixed step size symbol table and just can obtain actual step size: SB (Tx)
*Fixed step size, wherein SB (Tx) can represent the sign bit of the fixed step size symbol table of temperature spot Tx correspondence.Wherein initial temperature frequency correction word TCW (TO), fixed step size and fixed step size symbol table can be interior by the primary data memory cell 156 of data signal line DATA input.
In a concrete example, at comparative result is current accounting temperature point Tx when not being in lock-in range and T greater than Tx, and described temperature and frequency correcting letter lock order unit 154 obtains the sign bit that current accounting temperature point Tx approaches the needed fixed step size of next accounting temperature point Tx+S (such as being sign bit in the fixed step size symbol table of current accounting temperature point Tx correspondence) from the fixed step size symbol table, give fixed step size with the sign bit that obtains and approach the needed actual step size of next accounting temperature point Tx+S to obtain current accounting temperature point Tx, utilize the temperature and frequency correcting word TCW (Tx) of current accounting temperature point Tx correspondence and the temperature and frequency correcting word TCW (Tx+S) that actual step size obtains next accounting temperature point Tx+S correspondence.At comparative result is that accounting temperature Tx is not when being in lock-in range and T less than Tx, described temperature and frequency correcting letter lock order unit 154 obtains the sign bit that current accounting temperature point Tx approaches the needed fixed step size of next accounting temperature point Tx-S (because Tx-S＜Tx can claim that also Tx-S is last accounting temperature point) (such as being sign bit in the fixed step size symbol table of next accounting temperature point Tx-S correspondence) from the fixed step size symbol table, give fixed step size with the sign bit that obtains and approach the needed actual step size of next accounting temperature point Tx-S to obtain current accounting temperature point Tx, utilize the temperature and frequency correcting word TCW (Tx) of current accounting temperature point Tx correspondence and the temperature and frequency correcting word TCW (Tx-S) that actual step size obtains next accounting temperature point Tx-S correspondence.
As can be seen in an example of the present utility model, for a discrete temperature spot, described fixed step size symbol table only need be stored the sign bit of 1 bit binary data as the fixed step size of this temperature spot correspondence, thereby makes the data volume of described fixed step size symbol table become very little.Simultaneously, also can in the fixed step size symbol table, store the sign bit of more temperature spots, promptly can decrement keep predetermined temperature interval S smaller, can improve the precision of temperature frequency compensation like this.In the utility model by adopting a kind of digital desired temperature and frequency correcting value of frequency drift that interpolation method automatically locks different temperature spots of approaching one by one, thereby reduce the temperature and frequency correcting value of required storage to greatest extent, also improved simultaneously the precision of temperature frequency compensation, and determine that by digitized control able to programme reference clock source (as quartz crystal or other oscillator) at different performance or electronic system require the minimal hardware compensation scheme of required employing to frequency stability, have also reduced the cost and the performance requirement in system reference clock source in addition to greatest extent.
Fig. 2 is the functional-block diagram of an embodiment of the temperature and frequency correcting letter lock order unit 154 among Fig. 1.Described temperature and frequency correcting letter lock order unit 154 comprises that forward direction approaches computing unit 202, back to approaching computing unit 204, temperature and frequency correcting element word storage 206 and interpolation calculation unit 208.At comparative result is that accounting temperature Tx is not when being in lock-in range and T greater than Tx, described forward direction approaches computing unit 202 and obtain the sign bit that current accounting temperature point Tx approaches the needed fixed step size of next accounting temperature point Tx+S (such as being sign bit in the fixed step size symbol table of current accounting temperature point Tx correspondence) from the fixed step size symbol table, give fixed step size with the sign bit that obtains and approach the needed actual step size of next accounting temperature point Tx+S to obtain current accounting temperature point Tx, utilize the temperature and frequency correcting word TCW (Tx) of current accounting temperature point Tx correspondence and the temperature and frequency correcting word TCW (Tx+S) that actual step size obtains next accounting temperature point Tx+S correspondence, and described temperature and frequency correcting word TCW (Tx+S) is stored into the temperature and frequency correcting word TCW (Tx) of accounting temperature frequency correction element word storage 206 to calculate as next time.At comparative result is that accounting temperature Tx is not when being in lock-in range and T less than Tx, described back obtains the sign bit that current accounting temperature point Tx approaches the needed fixed step size of a last accounting temperature point Tx-S (such as being sign bit in the fixed step size symbol table of next accounting temperature point Tx-S correspondence) to approaching computing unit 204 from the fixed step size symbol table, give fixed step size with the sign bit that obtains and approach the needed actual step size of next accounting temperature point Tx-S to obtain current accounting temperature point Tx, utilize the temperature and frequency correcting word TCW (Tx) of current accounting temperature point Tx correspondence and the temperature and frequency correcting word TCW (Tx-S) that actual step size obtains next accounting temperature point Tx-S correspondence, and described temperature and frequency correcting word TCW (Tx-S) is stored into the temperature and frequency correcting word TCW (Tx) of accounting temperature frequency correction element word storage 206 to calculate as next time.When comparative result is in lock-in range for accounting temperature Tx, described interpolation calculation unit 208 utilizes temperature and frequency correcting word TCW (Tx) interpolation of storage to go out the pairing temperature and frequency correcting word of Current Temperatures T TCW (T), and exports it to frequency correction unit 130.
Fig. 3 shows the flow chart of an embodiment of the temperature and frequency correcting word acquisition methods in the utility model, and it has also reflected the course of work of described temperature and frequency correcting word generation unit 150.
Tx represents current accounting temperature point, and its initial value is initial temperature TO; The temperature and frequency correcting word of the current accounting temperature point Tx correspondence of TCW (Tx) expression, its initial value is initial temperature frequency correction word TCW (TO).
The value of described sign bit or be 1, or be 0, represent positive and negative respectively.
Step 315 utilizes the temperature and frequency correcting word TCW (Tx) of current accounting temperature point Tx and the actual step size of a last temperature spot Tx-S correspondence to ask for the corresponding temperature and frequency correcting word TCW (Tx-S) of an accounting temperature point.
Need explain, if the temperature sense precision of described digital temperature sensor (precision of Current Temperatures T) is than the temperature covering precision of described fixed step size symbol table, temperature sense precision such as described digital temperature sensor is 0.1 ℃, and the covering temperature accuracy of described fixed step size symbol table is 0.2 ℃ (being that S equals 0.2 ℃), will occur that accounting temperature Tx is in the lock-in range of Current Temperatures T and the situation that is not equal to Current Temperatures T needs just can obtain TCW (T) through interpolation.Yet, if the temperature sense precision of described digital temperature sensor is smaller or equal to the temperature covering precision of described fixed step size symbol table, accounting temperature Tx is in lock-in range and just is meant Tx=T so, like this after accounting temperature Tx is in lock-in range, described temperature and frequency correcting word TCW (Tx) is exactly the temperature and frequency correcting word TCW of Current Temperatures T correspondence, has therefore carried out interpolation arithmetic with regard to not needing.In addition, when the needs interpolation just can be obtained TCW (T), can adopt various interpolation methods, such as linear interpolation, non-linear interpolation, parabola interpolation etc., interpolation also may need near temperature and frequency correcting word such as TCW (Tx-S), TCW (Tx+S) in general except needs temperature and frequency correcting word TCW (Tx).
Calculate the temperature and frequency correcting word TCW of gained in output after,, enter step 321 afterwards with Tlock=T.
Step 321 reads digital temperature value T.
Step 323 judges whether described digital temperature value T equals described Tlock, if, then return step 321 and continue to read digital temperature value, otherwise return step 305, continue to repeat above-mentioned locking process.
By carrying out above-mentioned steps, the temperature and frequency correcting word that calculates Current Temperatures T correspondence that described temperature and frequency correcting word generation unit 150 utilizes TCW (TO), fixed step size and fixed step size symbol table to approach one by one quickly and accurately.Temperature and frequency correcting word for each temperature spot calculates, and only needs storage 1 bit sign data in the utility model, and this has significantly reduced memory data output.In addition, owing to only need store 1 bit data for each temperature spot, so the data that can store more temperature spots, the precision of frequency-temperature compensation has also increased greatly like this.
In a specific embodiment, in the described primary data memory cell 156 among Fig. 1 except storing initial temperature frequency correction word TCW (TO), fixed step size and fixed step size symbol table, also store the difference TCWd (TO) of initial temperature frequency correction word TCW (TO), the difference TCWd of wherein said temperature and frequency correcting word is meant the difference of the temperature and frequency correcting word of adjacent temperature spot correspondence, fixed step size is then represented the absolute difference of difference of the temperature and frequency correcting word of adjacent temperature spot correspondence, this moment, it can be represented with TCWds, also can be referred to as the difference fixed step size this moment in addition.Described initial temperature point TO can for the minimum of temperature coverage (such as-30 ℃ to 50 ℃) such as-30 ℃.Store the sign bit SB of the fixed step size of each discrete temperature spot correspondence in the described fixed step size symbol table, the figure place of the binary sequence of described fixed step size symbol table depends on its temperature coverage and predetermined temperature S at interval, such as the temperature coverage is from-30 to 50 ℃, S is 0.2 ℃, the binary sequence that then needs (50-(30))/0.2-1=400-1 position is not (because maximum temperature point has next temperature spot for 50 ℃, therefore do not need to store the symbol of the corresponding fixed step size of this maximum temperature point, therefore can lack 1 bit data).It should be noted that TCW (TO), TCWd (TO), TCWds and fixed step size symbol table are interior by the data storage 156 of data wire importing, as for how determining these data will be described in more detail below.
Fig. 5 is the schematic flow sheet according to the temperature and frequency correcting word acquisition methods of above-mentioned specific embodiment.
See also shown in Figure 5ly, the computational methods of temperature and frequency correcting word TCW comprise the steps.
Tx represents current accounting temperature point, the temperature and frequency correcting word of TCW (Tx) expression accounting temperature point Tx correspondence, the difference of the temperature and frequency correcting word of TCWd (Tx) expression accounting temperature point Tx correspondence.Described initialization can be in addition:
Tx=TO；TCW(Tx)=TCW(TO)；TCWd(Tx)=TCWd(TO)。
Step 503 reads digital temperature value T, is exactly that preamble is mentioned Current Temperatures or target temperature.
Step 505 judges that whether described digital temperature T value is more than or equal to Tx+S, if change step 507 over to; Otherwise change step 513 over to.
Step 507 reads the sign bit SB (Tx) in the fixed step size symbol table of current accounting temperature point Tx correspondence, gives the actual step size that TCWds forms Current Temperatures point Tx correspondence with this symbol: SB (Tx) * TCWds.This sign bit or be 1, or be 0, wherein 1 expression just, 0 expression is negative.
Step 509 is asked for the difference TCWd (Tx+S) of the temperature and frequency correcting word of the temperature and frequency correcting word TCW (Tx+S) of next accounting temperature point Tx+S correspondence and next accounting temperature point Tx+S correspondence.
TCW (Tx+S)=TCW (Tx)+TCWd (Tx) wherein;
TCWd(Tx+S)=TCWd(Tx)+SB(Tx)＊TCWds；
This process of asking for the correlation of next accounting temperature point can be called as forward direction and proofread and correct.
Step 513 continues to judge that whether described digital temperature T is less than Tx.If then change step 515 over to; Otherwise, change step 521 over to.
Step 515 reads the sign bit SB (Tx-S) in the fixed step size symbol table of an accounting temperature point Tx-S correspondence, gives the actual step size that TCWds forms a last accounting temperature point Tx-S correspondence: SB (Tx-S) * TCWds with this symbol.
TCWd (Tx-S)=TCWd (Tx)-SB (Tx-S) * TCWds wherein
TCW(Tx-S)=TCW(Tx)-TCWd(Tx-S)，
Proofread and correct with respect to foregoing forward direction, the correlation of asking for an accounting temperature point here gets process and can be called as the back to correction.
Calculate the temperature and frequency correcting word TCW of gained in output after,, enter step 523 afterwards with Tlock=T.
Step 523 reads digital temperature value T.
Step 525 judges whether described digital temperature value T equals described Tlock, if, then return step 523 and continue to read digital temperature value, otherwise return step 505, continue to repeat above-mentioned locking process.
For instance, when described initial temperature TO is temperature coverage minimum-30 ℃, when each temperature frequency compensation arrangement 100 shown in Figure 1 comes into operation, described digital temperature sensor can provide Current Temperatures T, such as T is 20 ℃, so flow process can continuous repeating step 503-511 to allow the Tx value approach 20 ℃ from-30 ℃ fast, enter step 513 afterwards until last locking temperature T.During the unexpected change of temperature in use, such as unexpected decline, flow process can reenter the tracking locking process, and promptly repeating step 503,505,513-519 step enter step 521 with locking temperature T afterwards to allow Tx approach new T value fast at once.
As seen characteristics of the acquisition methods of the temperature and frequency correcting word in the utility model, advantage is: utilize initial temperature frequency correction word, the difference of initial temperature frequency correction word starts trace flow, constantly utilize the corresponding temperature and frequency correcting word of current accounting temperature point, the difference of temperature and frequency correcting word, sign bit in the fixed step size symbol table and fixed step size calculate the temperature and frequency correcting word of correspondence of next accounting temperature point of convergence target temperature, be locked to Current Temperatures point T until the accounting temperature point, carry out trying to achieve the temperature and frequency correcting word of Current Temperatures point T correspondence according to interpolation.
As shown in Figure 6, the temperature frequency indicatrix of reference frequency can be undergone mutation under a certain section temperature, and this is a kind of very common phenomena.If it is bigger that the interval of Tc point is provided with, the frequency compensation of the temperature province of undergoing mutation for frequency will inaccuracy, and this also is a very big defective in the existing temperature frequency compensation technique.Utilize the technical scheme of obtaining of aforesaid temperature and frequency correcting word in the utility model, can effectively store abundant temperature spot data (a bit sign bit data), thereby the situation of this frequency discontinuity shown in Figure 6 be realized the temperature frequency compensation of very good effect.
Below, introduce the mensuration process of TCW (TO), TCWd (TO), TCWds and fixed step size symbol table in detail once.Wherein, Fig. 7 shows the TCW (TO) in the utility model, the mensuration process of TCWd (TO), TCWds, and Fig. 8 shows the acquisition process of the fixed step size symbol table in the utility model.
As shown in Figure 7, the assay method of described TCW (TO), TCWd (TO), TCWds comprises the steps.
Step 701 obtains reference frequency f
RThe temperature frequency curve.
The whole bag of tricks acquisition of the prior art can be passed through, but the temperature frequency curve and the actual reference frequency f of its generation must be will guaranteed
RThe temperature frequency curve consistent as far as possible, and keep the level and smooth of curve.In one embodiment, when the temperature frequency sudden change that does not have as shown in Figure 6, can adopt Beckman curve maker (Bechamann curve generator), by using a few temperature frequency test point just can generate more accurate temperature frequency characteristic curve, repeat no more here.
Step 703 is that temperature sampling is sampled to obtain each discrete Tc point frequency value corresponding to described temperature frequency curve at interval with S, and the value of described S will determine the temperature covering precision of described fixed step size symbol table.In an example, described S value can be set different values at different temperature applicable ranges, uses 0.1 ℃ as temperature sampling S at interval such as 0 ℃ in Fig. 6-20 ℃, and other temperature ranges in Fig. 6 are used 0.2 ℃ as temperature sampling S at interval.
Step 705 according to the frequency values of each Tc point and the functional relation between the temperature and frequency correcting word, utilizes each Tc point frequency value corresponding to ask for the theoretical temperatures frequency correction word TCW of each Tc point Tx correspondence
Ideal(Tx), wherein Tx represents to be spaced apart the discrete Tc point from min (Tx) to max (Tx) of S, and min (Tx) is the minimum value of Tx, and max (Tx) is the maximum of Tx.
The theoretical temperatures frequency correction word TCW of each Tc point Tx correspondence
Ideal(Tx) will go on record and be used for determining the value of described each sign bit of fixed step size symbol table.
Step 707 is calculated the theoretical temperatures frequency correction word TCW of each Tc point Tx correspondence
Ideal(Tx) difference TCWd
Ideal(Tx), wherein
TCWd
ideal(Tx)=TCWd
ideal(Tx+S)-TCWd
ideal(Tx)，
Tx belongs to [min (Tx), max (Tx-S)] herein.
Step 711 is calculated the theoretical temperatures frequency correction word TCW of each Tc point Tx correspondence
Ideal(Tx) difference TCWd
Ideal(Tx) difference TCWdd
Ideal(Tx), i.e. theoretical temperatures frequency correction word TCW
Ideal(Tx) second differnce, wherein
TCWdd
ideal(Tx)=TCWd
ideal(Tx+S)-TCWd
ideal(Tx)，
Tx belongs to [min (Tx), max (Tx-2S)] herein.
Step 713 is with the theoretical temperatures frequency correction word TCW of each Tc point Tx correspondence
Ideal(Tx) second differnce TCWdd
Ideal(Tx) the absolute value maximum is recorded as previously described difference fixed step size TCWds in.Why choosing maximum is in order to guarantee that matched curve (curve that promptly utilizes each accounting temperature frequency correction word that the difference fixed step size calculates to form) can catch up with the variation of ideal curve (being the temperature frequency curve that obtains in the step 701) for difference step size TCWds.Certainly in other embodiments, also can choose slightly little second differnce value is the difference fixed step size.
Hence one can see that, needing in the described primary data memory cell just can obtain the initial temperature frequency correction word TCW (TO) that preserves, the difference TCWd (TO) and the difference step size TCWds of initial temperature frequency correction word through execution in step 701-713.
Subsequently, can utilize the initial temperature frequency correction word TCW (TO) that has obtained, difference TCWd (TO), difference step size TCWds and the corresponding theoretical temperatures frequency correction word TCW of described each Tc point of initial temperature frequency correction word
Ideal(Tx) value of bits per inch certificate in the described fixed step size symbol table of acquisition.Please referring to shown in Figure 8, the acquisition process of the value of each bit data is as follows in the described fixed step size symbol table.
Tx represents current Tc point, the temperature and frequency correcting word of NTCW (Tx-S) expression Tx-S temperature spot correspondence, the difference of the temperature and frequency correcting word of the temperature and frequency correcting word correspondence of NTCWd (Tx-S) expression Tx-S temperature spot correspondence.It should be noted that, the temperature and frequency correcting word NTCW (Tx-S) of Tx-S temperature spot correspondence is not described theoretical temperatures frequency correction word, but the temperature and frequency correcting word that comes out according to the Difference Calculation of initial temperature frequency correction word and initial temperature frequency correction word.
Suppose that at previously described initial temperature TO be the minimum that practical application covers temperature range, so described initialization is exactly:
Tx=TO+S；NTCW(Tx-S)=TCW(TO)；NTCWd(Tx-S)=TCWd(TO)。
Here because initial temperature TO is the minimum temperature value, the temperature spot Tx that therefore need ask for only need equal the value of the corresponding positions in the fixed step size symbol table that TO+S just can realize asking for each temperature spot correspondence.If initial temperature TO is a peak, then need other Tx=TO-S, other parameter also needs according to the same rule corresponding modify.
NTCW(Tx)=NTCW(Tx-S)+NTCWd(Tx-S)。
Step 805 supposes that the value of sign bit SB (Tx-S) in the fixed step size symbol table of Tx-S temperature spot correspondence is 0, asks for the first accounting temperature frequency correction word NTCWO (Tx+S) of Tx+S temperature spot correspondence, is specially:
NTCWO(Tx+S)=NTCW(Tx)+NTCWd(Tx)
=NTCW(Tx-S)+NTCWd(Tx-S)+NTCWd(Tx-S)+SB(Tx)＊TCWds
=NTCW(Tx-S)+2＊NTCWd(Tx-S)-TCWds。
DNTCWO(Tx+S)=Abs(TCW
ideal(Tx+S)-NTCWO(Tx+S))。
Step 809 supposes that the value of sign bit SB (Tx-S) in the fixed step size symbol table of Tx-S temperature spot correspondence is 1, asks for the second accounting temperature frequency correction word NTCW1 (Tx+S) of Tx+S temperature spot correspondence, is specially:
NTCW1(Tx+S)=NTCW(Tx-S)+2＊NTCWd(Tx-S)+SB(Tx-S)＊TCWds
=NTCW(Tx-S)+2＊NTCWd(Tx-S)+TCWds。
DNTCW1(Tx+S)=Abs(TCW
ideal(Tx+S)-NTCWO(Tx+S))。
DNTCWO (Tx+S)＜DNTCW1 (Tx+S) if then enter step 815, otherwise enters step 817.
NTCWd(Tx)=NTCWd(Tx-S)-TCWds。
NTCWd(Tx)=NTCWd(Tx-S)+TCWds。
Step 825 judges that Tx whether smaller or equal to MAX (Tx)-S, if not, then finishes calculation process, otherwise returns step 803, repeats above-mentioned steps.
Carry out above-mentioned steps 801-825, just can calculate the value of each data in the described fixed step size symbol table.
Difference TCWd (TO), difference step size TCWds and the fixed step size symbol table of the last initial temperature frequency correction word TCW (TO) that just mensuration can be come out, initial temperature frequency correction word import data storage cell 156 by data wire.
In another specific embodiment, in the described data storage cell 156 except storing initial temperature frequency correction word TCW (TO), fixed step size and fixed step size symbol table, also store the difference TCWd (TO) of initial temperature frequency correction word TCW (TO), the second differnce TCWdd (TO) of initial temperature frequency correction word TCW (TO), the difference TCWd of wherein said temperature and frequency correcting word is meant the difference of the temperature and frequency correcting word of adjacent temperature spot correspondence, the second differnce TCWdd of described temperature and frequency correcting word is meant the difference of difference of the temperature and frequency correcting word of adjacent temperature spot correspondence, fixed step size is then represented the difference of second differnce of the temperature and frequency correcting word of adjacent temperature spot correspondence, this moment, it can be represented with TCWdds, and also can be referred to as the second differnce fixed step size this moment.In this embodiment, the computational process of obtaining of temperature and frequency correcting word TCW can mainly be that step 509 and 517 is understood some variation with reference to computational process shown in Figure 5, and wherein step 509 becomes:
TCW(Tx+S)=TCW(Tx)+TCWd(Tx)
TCWd(Tx+S)=TCWd(Tx)+TCWdd(Tx)
TCWdd(Tx+S)=TCWdd(Tx)+SB(Tx)＊TCWdds，
Wherein step 517 becomes:
TCWdd(Tx-S)=TCWdd(Tx)-SB(Tx-S)＊TCWdds
TCWd(Tx-S)=TCWd(Tx)-TCWdd(Tx-S)
TCW(Tx-S)=TCW(Tx)-TCWd(Tx-S)
Similarly, some variations also can take place in the difference TCWd (TO) of initial temperature frequency correction word TCW (TO), initial temperature frequency correction word TCW (TO), second differnce TCWdd (TO), the second differnce fixed step size TCWdds of initial temperature frequency correction word TCW (TO) and the mensuration process of fixed step size symbol table, but principle is identical with previous examples, just repeats no more here.Certainly, other are executed and also may use the above difference in three rank or three rank in the example, and principle is all similar, holds and does not give unnecessary details.
In another specific embodiment, only store initial temperature frequency correction word TCW (TO), fixed step size and fixed step size symbol table in the described data storage cell 152, described fixed step size table is then represented the difference of the temperature and frequency correcting word of adjacent temperature spot correspondence, and this moment, it can be represented with TCWs.In this embodiment, the computational process of temperature and frequency correcting word TCW can mainly be that step 509 and 517 is understood some variation with reference to computational process shown in Figure 5, and wherein step 509 becomes:
TCW(Tx+S)=TCW(Tx)+SB(Tx)＊TCWs
Wherein step 517 becomes:
TCW(Tx-S)=TCW(Tx)-SB(Tx-S)＊TCWs。
Similarly, some variations also can take place in the mensuration process of initial temperature frequency correction word TCW (TO), fixed step size TCWs and fixed step size symbol table, but principle is identical with previous examples, just repeats no more here.
As shown in Figure 6, the temperature frequency characteristic curve of reference frequency can be undergone mutation in a certain specified temp zone frequency, in order to take into account this situation of frequency discontinuity, the utility model need be considered this special circumstances in selected fixed step size, this just may cause when the accounting temperature frequency correction word of normal temperature zone, is not very accurate.In order to address the above problem, in a preferred embodiment, can not only store one group of primary data in the described data storage cell 156, can also store two groups or three groups of primary datas.Every group of primary data can comprise the difference of initial temperature correct word, initial temperature correct word and the value of three parameters of difference fixed step size, the value that also can comprise initial temperature correct word and two parameters of fixed step size can also comprise the difference of initial temperature correct word, initial temperature correct word, the second differnce of initial temperature correct word and the value of four parameters of second differnce fixed step size.Every group of primary data all has corresponding temperature range separately, and only is suitable in the temperature range of being responsible for separately.For instance, can store three groups of initial temperature frequency correction words, the difference of initial temperature frequency correction word, difference fixed step size for the temperature frequency indicatrix among Fig. 6, first group initial temperature point is-30 ℃, second group initial temperature point is 0 ℃, the 3rd group initial temperature point is 20 ℃, first group of primary data is used for the temperature and frequency correcting between-30 ℃-0 ℃, second group of primary data is used for the temperature and frequency correcting between 0 ℃-20 ℃, and the 3rd group of primary data is used for the temperature and frequency correcting between 20 ℃-100 ℃.Certainly, the value of each bit data in the fixed step size symbol table also is to rely on the primary data in the temperature range separately to try to achieve, and therefore also can only be used in the temperature range separately.Like this, can set up the primary data of oneself, make the tracking correction effect in the utility model better accurately at temperature frequency sudden change zone.
In sum, characteristics of the scheme of obtaining of temperature and frequency correcting word of the present utility model, advantage or progressive being: be not the temperature and frequency correcting word (such as 32 bit data) of as of the prior art, storing each temperature spot correspondence, but only store symbol (1 bit data) and one or a few fixed step size and the initial temperature frequency correction word of the fixed step size of each temperature spot correspondence, when needs obtain the temperature and frequency correcting word of Current Temperatures correspondence, sign bit according to the fixed step size of each temperature spot correspondence, the temperature and frequency correcting word of fixed step size and last computation (initial value is an initial temperature frequency correction word) calculates one by one and levels off to the temperature and frequency correcting word of Current Temperatures, is locked in the temperature and frequency correcting word of Current Temperatures until result of calculation.
The above only is preferred embodiment of the present utility model, and is in order to restriction the utility model, not all within spirit of the present utility model and principle, any modification of being done, is equal to replacement etc., all should be included within the protection range of the present utility model.
Claims (3)
1. temperature frequency correcting apparatus is characterized in that it comprises:
Data storage cell is used for the temperature and frequency correcting word of storing initial temperature correspondence;
The temperature and frequency correcting word acquiring unit that is connected with described data storage cell is used to continue to obtain the temperature and frequency correcting word of accounting temperature correspondence;
With the frequency correction unit that described temperature and frequency correcting word acquiring unit is connected, be used to receive the temperature and frequency correcting word that described temperature and frequency correcting word acquiring unit provides and utilize the temperature and frequency correcting word that frequency control word is compensated to obtain the emending frequency control word;
The frequency locking synthesis unit that is connected with described frequency correction unit is used to receive emending frequency control word that described frequency correction unit provides and is that the basis generates the desired output frequency according to described emending frequency control word with the reference frequency.
2. the temperature frequency correcting apparatus shown in claim 1, it is characterized in that: temperature approaches unit that described temperature and frequency correcting word acquiring unit comprises the temperature comparing unit, link to each other with the temperature comparing unit and the temperature and frequency correcting letter lock order unit that links to each other with the temperature approaches unit with the temperature comparing unit, wherein
It is that current accounting temperature point and the Current Temperatures of initial temperature compares that described temperature comparing unit is used for initial value.
3. temperature frequency correcting apparatus is characterized in that it comprises:
Data storage cell is used to store the ideal temperature frequency characteristics is carried out sampling analysis at interval with predetermined temperature and the primary data that obtains;
The temperature and frequency correcting word acquiring unit that is connected with described data storage cell is used to receive primary data that described data storage cell provides and the temperature and frequency correcting word that obtains the accounting temperature correspondence according to described primary data; With
With the temperature and frequency correcting unit that described temperature and frequency correcting word acquiring unit is connected, be used to receive the temperature and frequency correcting word of described temperature and frequency correcting word acquiring unit output and utilize described temperature and frequency correcting word to carry out temperature and frequency correcting.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102571155A (en) * | 2010-12-30 | 2012-07-11 | 芯讯通无线科技（上海）有限公司 | Frequency correcting device, method for correcting frequency as well as SRD (Short Range Devices) communication system and communication method |
| CN104065374A (en) * | 2014-05-19 | 2014-09-24 | 浪潮电子信息产业股份有限公司 | Crystal oscillator accuracy control method based on capacitive load automatic adjusting technology |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102571155A (en) * | 2010-12-30 | 2012-07-11 | 芯讯通无线科技（上海）有限公司 | Frequency correcting device, method for correcting frequency as well as SRD (Short Range Devices) communication system and communication method |
| CN102571155B (en) * | 2010-12-30 | 2016-04-20 | 芯讯通无线科技（上海）有限公司 | The method of frequency correcting apparatus, emending frequency, SRD communication system and bearing calibration |
| CN104065374A (en) * | 2014-05-19 | 2014-09-24 | 浪潮电子信息产业股份有限公司 | Crystal oscillator accuracy control method based on capacitive load automatic adjusting technology |
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