CN201515347U - Temperature frequency correcting device - Google Patents

Embodiment

Below in conjunction with Figure of description embodiment of the present utility model is described.

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.

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

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.

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.

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.

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).

Step 321 reads digital temperature value T.

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 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 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.

Step 523 reads digital temperature value T.

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))。

NTCWd(Tx)=NTCWd(Tx-S)-TCWds。

NTCWd(Tx)=NTCWd(Tx-S)+TCWds。

Carry out above-mentioned steps 801-825, just can calculate the value of each data in the described fixed step size symbol table.

TCW(Tx+S)=TCW(Tx)+TCWd(Tx)

TCWd(Tx+S)=TCWd(Tx)+TCWdd(Tx)

TCWdd(Tx+S)=TCWdd(Tx)+SB(Tx)＊TCWdds，

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.

TCW(Tx+S)=TCW(Tx)+SB(Tx)＊TCWs

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.