CN103312325A - Frequency synthesizer - Google Patents
Frequency synthesizer Download PDFInfo
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- CN103312325A CN103312325A CN2013102597101A CN201310259710A CN103312325A CN 103312325 A CN103312325 A CN 103312325A CN 2013102597101 A CN2013102597101 A CN 2013102597101A CN 201310259710 A CN201310259710 A CN 201310259710A CN 103312325 A CN103312325 A CN 103312325A
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Abstract
The invention discloses a frequency synthesizer. The frequency synthesized comprises a first counter, a second counter, a controllable oscillator and a controller. The controller obtains a first time when the first counter completes N counts, calculates a target count value of the second counter in the first time according to a target frequency when outputs frequency signals, determines a target count interval of the second counter in the first time according to the target count value and then compares an actual count value completed by the second counter in the first time with the target count interval; according to the comparative result, the controller adjusts the output frequency of the controllable oscillator towards a direction close to the target frequency until the output frequency signals of the controllable oscillator reaches a target frequency meeting the precision requirements. The frequency synthesizer can reduce the requirements on loop stability and bandwidth and the design difficulties of internal modules and achieve the configurability of the precision of the output frequency signals.
Description
Technical field
The present invention relates to the frequency synthesis technique field, relate in particular to a kind of frequency synthesizer.
Background technology
Frequency synthesizer is to utilize one or more standard signals, produces the equipment of a large amount of discrete frequency signals by various technological approaches.At present extensive use be phase-locked loop synthesis method of the frequency (PLLFS, Phase-Locked Loop Frequency Synthesis).
The phase-locked loop frequency synthesis is a kind of indirect frequency combining method, and it utilizes Phase Lock Technique to produce to have in a large number high stability, highly purified frequency source, its basic structure such as Fig. 1.Reference frequency signal f
RefUsually by input frequency signal f
InProduce through frequency divider, wherein, f
In=Mf
Ref, phase discriminator (PD) is to reference frequency signal f
RefAnd the frequency signal f of voltage controlled oscillator (VCO) output
OutThe feedback frequency signal f that frequency division obtains
FbCarry out the phase bit comparison, as long as f
RefAnd f
FbNot that phase discriminator just has signal V with the frequency homophase
dOutput, V
dFiltering obtains later on the mean value V of direct current through loop filter
c, the output frequency f of control VCO
Out, wherein, f
Out=Nf
FbV
cMeeting is so that f
FbFrequency and phase place towards closer to f
RefFrequency and the direction of phase place change, so iterative cycles finally causes f
FbWith f
RefWith frequency homophase, V
cSettle out the frequency signal f of VCO stable output
Out, reach locking, at this moment,
But, existing phase-locked loop frequency synthesizer is all wanted high requirement to loop stability and bandwidth, each module of loop can affect the spectral purity of the frequency signal of output in addition, this just causes the designing requirement of loop modules higher, and the precision of the frequency signal of phase-locked loop frequency synthesizer output fixes, and can not configure according to demand.
Summary of the invention
In view of this, the object of the present invention is to provide a kind of frequency synthesizer, can reduce the requirement to loop stability and bandwidth, can reduce the module of the spectral purity that affects output frequency signal, reduce the difficulty of internal module design, and can realize the configurable of output frequency signal precision.
For achieving the above object, the invention provides following technical scheme:
The invention discloses a kind of frequency synthesizer, comprise the first counter, the second counter, controlled oscillator and controller;
Described controlled oscillator produces output frequency signal under the control of described controller;
Described the first counter is counted input frequency signal;
Described the second counter is counted the output frequency signal of described controlled oscillator;
Described controller obtains the very first time that described the first counter is finished N counting, according to formula c=Nf
Out'/f
InCalculate the objective count value c of described the second counter within the described very first time, determine the object count of described the second counter within the described very first time interval [c-e, c+e], wherein f
Out' be the target frequency of described output frequency signal, f
InFrequency for described input frequency signal, e is the permission counting error of described the second counter, obtain the actual count value that described the second counter is finished within the described very first time, more described actual count value and described object count are interval, when described actual count value is positioned at described object count interval, the output frequency of keeping described controlled oscillator is constant, in the time of outside described actual count value is positioned at described object count interval, adjust the output frequency of described controlled oscillator to the direction of close described target frequency according to comparative result, described the first counter and the second counter reset, return and carry out the step obtain the actual count value that described the second counter finishes within the described very first time, perhaps return to carry out and obtain the step that described the first counter is finished N the very first time of counting.
Preferably, in the said frequencies synthesizer, the permission counting error e=c*p of described the second counter, wherein, p is that described output frequency signal is with respect to the precision of described input frequency signal.
Preferably, in the said frequencies synthesizer, described controller according to comparative result to the output frequency of adjusting described controlled oscillator near the direction of described target frequency is:
When described comparative result showed that described actual count value is interval greater than described object count, described controller was controlled described controlled oscillator and is reduced output frequency;
When described comparative result showed that described actual count value is interval less than described object count, described controller was controlled described controlled oscillator and is improved output frequency.
Preferably, in the said frequencies synthesizer, described tunable oscillator is voltage controlled oscillator, described controller improves the magnitude of voltage of output voltage with default increment, improve output frequency to control described voltage controlled oscillator, described controller reduces the magnitude of voltage of output voltage with default decrement, reduce output frequency to control described voltage controlled oscillator.
Preferably, in the said frequencies synthesizer, described tunable oscillator is voltage controlled oscillator, described controller improves the magnitude of voltage of output voltage with default increment, reduce output frequency to control described voltage controlled oscillator, described controller reduces the magnitude of voltage of output voltage with default decrement, improve output frequency to control described voltage controlled oscillator.
This shows, beneficial effect of the present invention is: frequency synthesizer disclosed by the invention, reponse system has enough resetting times, and it changes output frequency, therefore can be so that loop can't satisfy the condition of vibration all the time, loop is stable always, thereby reduces the requirement to loop stability; The spectral purity of the output frequency of frequency synthesizer only is subject to the impact of controlled oscillator, so this loop can be only according to the suitable bandwidth value of the bandwidth selection of controlled oscillator, reduced the difficulty of bandwidth selection, simultaneously, owing to having reduced the module of the spectral purity that affects output frequency signal, thereby having reduced the design difficulty of internal module; In addition, a foundation of the interval output frequency as adjusting controlled oscillator of the object count of the second counter within the very first time, just can adjust this object count by the permission counting error of adjusting the second counter interval, thereby realize the configurable of frequency synthesizer output frequency signal precision.
Description of drawings
In order to be illustrated more clearly in the embodiment of the invention, the below will do simple introduction to the accompanying drawing of required use among the embodiment, apparently, accompanying drawing in the following describes only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain according to these accompanying drawings other accompanying drawing.
Fig. 1 is the structural representation of existing phase-locked loop frequency synthesizer;
Fig. 2 is the structural representation of a kind of frequency synthesizer disclosed by the invention;
Fig. 3 is the flow chart that frequency synthesizer middle controller control controlled oscillator shown in Figure 2 is adjusted output frequency.
Embodiment
Existing phase-locked loop frequency synthesizer has higher requirement to the stability of loop.Reason is: phase-locked loop frequency synthesizer itself is a degeneration factor, and loop will produce vibration when it can satisfy the degeneration factor oscillating condition, and is no longer stable, therefore should guarantee its stability when carrying out the phase-locked loop design.
Phase-locked loop frequency synthesizer also has higher requirement to the bandwidth of loop.Reason is: phase-locked loop frequency synthesizer has low-pass characteristic to the input noise of voltage controlled oscillator, and the noise of voltage controlled oscillator itself is had high pass characteristic, and this is conflict.Because suppress input noise, loop bandwidth is more narrow better, suppress the noise of voltage controlled oscillator itself, and loop bandwidth is more wide better.Therefore simultaneously, loop bandwidth also has influence on the locking time of its loop, and when doing the loop bandwidth design, the balance of must compromising considers the factor of each side, this shows, the design of phase-locked loop frequency synthesizer has higher requirement to bandwidth.
In addition, the frequency purity of the frequency signal of phase-locked loop frequency synthesizer output is subject to the impact of all modules in the loop, causes the designing requirement of modules in the loop higher.
The present invention discloses a kind of frequency synthesizer, can reduce requirement to loop stability and bandwidth with respect to existing phase-locked loop frequency synthesizer, can reduce the module of the spectral purity that affects output frequency signal, reduce the difficulty of internal module design, and can realize the configurable of output frequency signal precision.
Below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills are not making under the creative work prerequisite, and the every other embodiment that obtains belongs to protection range of the present invention.
Referring to Fig. 2, Fig. 2 is the structural representation of a kind of frequency synthesizer disclosed by the invention.This frequency synthesizer comprises the first counter 100, the second counter 200, controlled oscillator 300 and controller 400.
Wherein:
Controlled oscillator 300 produces output frequency signal under the control of controller 400, this output frequency signal is the output frequency signal of whole frequency synthesizer.This controlled oscillator 300 can adopt voltage controlled oscillator, current control oscillator and change the RC oscillator of output frequency or LC oscillator etc. by the register configuration value, perhaps is subjected to the oscillator of other controlled quentity controlled variables controls.
The first counter 100 is used for input frequency signal is counted.
The second counter 200 is used for the output frequency signal of controlled oscillator 300 is counted.
Step S1: controller obtains the very first time t that the first counter 100 is finished N counting.
Because the frequency f of input frequency signal
InBe certain, therefore, the first counter 100 is finished the time t=N/f of N counting
InN is positive integer, can select according to the frequency of input frequency signal and the target frequency of output frequency signal.
Step S2: controller is determined the second objective count value c of counter 200 in very first time t.
Controller is according to the target frequency f of the output frequency signal of very first time t and oscillator 300
Out' determine the second objective count value c of counter 200 in very first time t, c=t/ (1/f
Out')=N*f
Out'/f
In
Step S3: determine that the object count of the second counter 200 in very first time t is interval.
The object count interval of the second counter 200 in very first time t is [c-e, c+e], and wherein e is the permission counting error of the second counter 200, by different permission counting errors is set, can realize that the precision of output frequency signal is regulated.Certainly, this allows counting error also can be 0, and the precision that frequency synthesizer namely is set is 100%, need to prove, the precision of frequency synthesizer is 100% only to be ideal value, and it is to be based upon input frequency signal and not have on the basis of error.
Step S4: obtain the actual count value M that the second counter 200 is finished in very first time t.
Step S5: relatively actual count value M and object count are interval.
Step S6: when actual count value M was positioned at the object count interval, the output frequency of keeping controlled oscillator 300 was constant.
Step S7: when actual count value M was positioned at outside the object count interval, to the output frequency of adjusting controlled oscillator 300 near the direction of target frequency, reset the first counter 100 and the second counter 200 returned execution in step S4 according to comparative result.
After execution in step S5, when actual count value M is positioned at outside the object count interval, adjust the output frequency of controlled oscillator 300 to the direction of close target frequency according to comparative result, reset after the first counter 100 and the second counter 200, also can return step S1, namely again obtain the very first time t that the first counter 100 is finished N counting.When again obtaining the first counter 100 and finish the very first time t of N counting, this N value can with acquisition process last time in the N value be same numerical value, also can be different numerical value.
Frequency synthesizer disclosed by the invention, reponse system have enough resetting times, and its change output frequency, therefore can be so that loop can't satisfy the condition of vibration all the time, and loop is stable always, thereby reduces the requirement to loop stability; The spectral purity of the output frequency of frequency synthesizer only is subject to the impact of controlled oscillator, so this loop can be only according to the suitable bandwidth value of the bandwidth selection of controlled oscillator, reduced the difficulty of bandwidth selection, simultaneously, owing to having reduced the module of the spectral purity that affects output frequency signal, thereby having reduced the design difficulty of internal module; In addition, a foundation of the interval output frequency as adjusting controlled oscillator of the object count of the second counter within the very first time, just can adjust this object count by the permission counting error of adjusting the second counter interval, thereby realize the configurable of frequency synthesizer output frequency signal precision.
In the above-mentioned disclosed frequency synthesizer of the present invention, controller 400 is determined in the process in the object count interval of the second counter 200 in very first time t, the permission counting error of the second counter 200 can manually be inputted, and also can be calculated according to the required precision of frequency synthesizer by controller 400.Concrete, controller obtains output frequency signal with respect to the precision p of input frequency signal, determines the permission counting error e of the second counter 200 according to formula e=c*p.
When the actual count value M that controller 400 is finished within the very first time at definite the second counter 200 is positioned at outside the object count interval, according to comparative result to the output frequency of adjusting controlled oscillator 300 near the direction of target frequency be: when comparative result shows that actual count value M is interval greater than object count, controller 400 control controlled oscillators 300 reduce output frequency, when comparative result showed that actual count value M is interval less than object count, controller 400 control controlled oscillators 300 improved output frequency.
If the output frequency of voltage controlled oscillator is directly proportional with the magnitude of voltage of control voltage, when determining to need to improve the output frequency of voltage controlled oscillator, controller 400 improves the magnitude of voltage of the voltage signal of output with default increment, thereby the control voltage controlled oscillator improves output frequency.When determining to need to reduce the output frequency of voltage controlled oscillator, controller 400 reduces the magnitude of voltage of the voltage signal of output with default decrement, thereby the control voltage controlled oscillator reduces output frequency.
If the output frequency of voltage controlled oscillator is inversely proportional to the magnitude of voltage of control voltage, when determining to need to improve the output frequency of voltage controlled oscillator, controller 400 reduces the magnitude of voltage of the voltage signal of output with default decrement, thereby the control voltage controlled oscillator improves output frequency.When determining to need to reduce the output frequency of voltage controlled oscillator, controller 400 improves the magnitude of voltage of the voltage signal of output with default increment, thereby the control voltage controlled oscillator reduces output frequency.
In addition, this default increment and default decrement can be definite value, also can be according to the difference adjustment between actual count value M and the object count interval.When the difference between actual count value M and the object count interval during greater than a certain threshold value, it is the first numerical value that default increment and default decrement are set, when the difference between actual count value M and the object count interval during less than a certain threshold value, it is second value that default increment and default decrement are set, the first numerical value is greater than second value, can guarantee that like this voltage controlled oscillator adjusts output frequency as early as possible to the target frequency that satisfies required precision.
In addition, when the controlled quentity controlled variable of controlled oscillator was the Configuration Values of register, loop can adopt the alternate manner such as binary search to find the optimum Configuration Values that satisfies condition, so that loop is met the output frequency of requirement with speed faster.
Each embodiment adopts the mode of going forward one by one to describe in this specification, and what each embodiment stressed is and the difference of other embodiment that identical similar part is mutually referring to getting final product between each embodiment.For the disclosed device of embodiment, because it is corresponding with the disclosed method of embodiment, so description is fairly simple, relevant part partly illustrates referring to method and gets final product.
It will be understood by those skilled in the art that and to represent information, message and signal with many different techniques and in the technology any one.For example, the message of mentioning in the above-mentioned explanation, information can be expressed as voltage, electric current, electromagnetic wave, magnetic field or magnetic particle, light field or above combination in any.
Claims (5)
1. a frequency synthesizer is characterized in that, comprises the first counter, the second counter, controlled oscillator and controller;
Described controlled oscillator produces output frequency signal under the control of described controller;
Described the first counter is counted input frequency signal;
Described the second counter is counted the output frequency signal of described controlled oscillator;
Described controller obtains the very first time that described the first counter is finished N counting, according to formula c=Nf
Out'/f
InCalculate the objective count value c of described the second counter within the described very first time, determine the object count of described the second counter within the described very first time interval [c-e, c+e], wherein f
Out' be the target frequency of described output frequency signal, f
InFrequency for described input frequency signal, e is the permission counting error of described the second counter, obtain the actual count value that described the second counter is finished within the described very first time, more described actual count value and described object count are interval, when described actual count value is positioned at described object count interval, the output frequency of keeping described controlled oscillator is constant, in the time of outside described actual count value is positioned at described object count interval, adjust the output frequency of described controlled oscillator to the direction of close described target frequency according to comparative result, described the first counter and the second counter afterwards reset, return and carry out the step obtain the actual count value that described the second counter finishes within the described very first time, perhaps return to carry out and obtain the step that described the first counter is finished N the very first time of counting.
2. frequency synthesizer according to claim 1 is characterized in that, the permission counting error e=c*p of described the second counter, and wherein, p is that described output frequency signal is with respect to the precision of described input frequency signal.
3. frequency synthesizer according to claim 1 and 2 is characterized in that, described controller according to comparative result to the output frequency of adjusting described controlled oscillator near the direction of described target frequency is:
When described comparative result showed that described actual count value is interval greater than described object count, described controller was controlled described controlled oscillator and is reduced output frequency;
When described comparative result showed that described actual count value is interval less than described object count, described controller was controlled described controlled oscillator and is improved output frequency.
4. frequency synthesizer according to claim 3, it is characterized in that, described tunable oscillator is voltage controlled oscillator, described controller improves the magnitude of voltage of output voltage with default increment, improve output frequency to control described voltage controlled oscillator, described controller reduces the magnitude of voltage of output voltage with default decrement, reduce output frequency to control described voltage controlled oscillator.
5. frequency synthesizer according to claim 3, it is characterized in that, described tunable oscillator is voltage controlled oscillator, described controller improves the magnitude of voltage of output voltage with default increment, reduce output frequency to control described voltage controlled oscillator, described controller reduces the magnitude of voltage of output voltage with default decrement, improve output frequency to control described voltage controlled oscillator.
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| CN103888138B (en) * | 2014-03-23 | 2017-04-12 | 上海正耘电子科技有限公司 | Method for outputting high-precision and high-frequency clock signals and oscillating circuit |
| CN112255553A (en) * | 2020-09-18 | 2021-01-22 | 北京汽车股份有限公司 | Chip for detecting cell molecular decay, cell activity protection system and method |
| CN113391273A (en) * | 2021-06-11 | 2021-09-14 | 广州极飞科技股份有限公司 | Signal generation method and device, signal transmitting equipment and readable storage medium |
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