Phase-locked loop automatic pre-set system and pre-setting method thereof
Technical field
The present invention relates to microwave signal analysis field, especially phase-locked loop automatic pre-set system and pre-setting method thereof.
Background technology
In modern microwave signal analyzer, conventionally adopt superheterodyne signal receiving mode, the tunable local oscillation signal of analyzer is determining the many key technical index of analyzer.In high-grade signal analyzer, the scheme of tunable local oscillator generally adopts multiring structure, is generally sampling ring, little ring of numbers and YO ring.Wherein sampling ring is ultralow voltage controlled oscillator of making an uproar mutually (being called for short VCO) phase-locked loop, is a kind ofly to produce that frequency is controlled, low phase noise, the phase-locked loop of discrete point-frequency signal.
The phase noise of the local oscillator of signal analyzer and frequency resolution are determining the phase noise level of signal analyzer complete machine and the technical indicator of frequency discrimination, and these two indexs are to embody the important indicator that analyzer is analyzed small-signal ability.How improving the phase noise index of signal analyzer local oscillator, is constantly to pursue in signal analyzer research and development.In order to improve phase noise index, the high-grade signal analyzer local oscillator technical schemes that adopt a plurality of phase-locked loops more, sampling ring is exactly one of them loop, and its effect is to provide that Frequency point is variable, discrete, the point-frequency signal of low phase noise.Sampling ring is one and take the phase-locked loop that voltage controlled oscillator (VCO) be oscillation source, and the output frequency of sampling ring is by being added in the preset voltage of the tuning end of voltage controlled oscillator (VCO) and the decision of the error voltage after phase demodulation integration.
As accompanying drawing 1, in traditional phase-locked loop, voltage controlled oscillator output, through after integer or fractional frequency division, is carried out phase demodulation with reference signal, and phase demodulation output is added to the tuning end of voltage controlled oscillator afterwards through integration, thereby controls the frequency of oscillation of oscillator.In this kind of phase-locked loop structures, generally do not need preset voltage or only need a rough preset voltage just, the output frequency of phase-locked loop is that frequency dividing ratio and the phase demodulation reference frequency in loop determines jointly.So traditional voltage controlled oscillator (VCO) is phase-locked do not need preset accurately.But due to the frequency division link existing oscillator signal, be the bottleneck that phase-locked loop phase noise further reduces in traditional loop structure.
Summary of the invention
While changing in order to solve the tuning voltage of voltage controlled oscillator and the functional relation of output frequency, how automatically the problem of preset oscillator quick and precisely, the present invention proposes a kind of method that new phase-locked loop automatics and automatic pre-set are adjusted.Even if the functional relation of the tuning voltage of oscillator and output frequency has changed, also can according to current functional relation, adjust preset voltage fast.
The present invention adopts following technical scheme:
Phase-locked loop automatic pre-set system, comprises voltage controlled oscillator, integrator, phase discriminator and programmable chip, also comprises varactor doubler, tri-frequency divider, frequency mixer, directional coupler and sampler;
Described varactor doubler comprises the first varactor doubler and the second varactor doubler;
The output of described voltage controlled oscillator connects the input of the first varactor doubler, the input of the output termination directional coupler of the first varactor doubler, the straight-through output of directional coupler connects the input of the second varactor doubler, the rf inputs of the output termination frequency mixer of the second varactor doubler, the local oscillator end of frequency mixer is connected with local oscillation signal F2, the medium frequency output end of frequency mixer connects the rf inputs of sampler, the local oscillator end of sampler is connected with local oscillation signal F1, local oscillation signal F1 connects the input of tri-frequency divider, the output of tri-frequency divider connects the reference edge of phase discriminator, the rf inputs of phase discriminator connects the medium frequency output end of sampler, the output of phase discriminator connects integrator, integrator connects the tuning end of voltage controlled oscillator through analog switch, error voltage is delivered to the tuning end of voltage controlled oscillator,
The coupling output of described directional coupler connects the rf inputs of phase demodulation integrator, the reference edge of phase demodulation integrator connects the output of tri-frequency divider, the control end of phase demodulation integrator connects programmable chip, the output of phase demodulation integrator connects the first input end of voltage comparator, the second input of voltage comparator connects comparative voltage V1, the output of voltage comparator connects programmable chip, the digital input end of the output linking number weighted-voltage D/A converter of programmable chip, digital to analog converter becomes analog voltage signal by digital signal conversion, the analog output of digital to analog converter connects the tuning end of voltage controlled oscillator, preset voltage is delivered to the tuning end of voltage controlled oscillator,
Phase-locked loop output frequency in the situation that of locking is F, F=F2+N*F1+Fref, and wherein Fref is phase demodulation reference signal, and N is integer, and the value of N is determined by preset voltage.
Further, described directional coupler is printed board microstrip line coupler.
Further, described comparative voltage V1 value is 0, and the frequency of local oscillation signal F1 is 100MHz, and the frequency of local oscillation signal F2 is 4800MHz.
Pre-setting method based on above-mentioned phase-locked loop automatic pre-set system, comprises the steps:
(1) first analog switch is disconnected, make phase-locked loop in open loop situations; By the phase demodulation frequency that phase demodulation integrator is set of programmable chip, according to tuning point frequency and reference frequency, determine the frequency dividing ratio of rf inputs and reference input; The input value of the preset digital to analog converter for the first time by programmable chip;
(2) according to the height state of Programmable Logic Controller detection voltage comparator output, determine the preset value of voltage controlled oscillator tuning point, its step is as follows:
A., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 40; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 40;
After time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output; If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 40; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 40;
If the height state that front and back detect for twice is identical, repeat a step, until the height state that front and back detect for twice is when different, as the input value of preset digital to analog converter for the second time, be transferred to step b;
B., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 20; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 20; As the input value of preset digital to analog converter for the third time;
C., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 10; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 10; Input value as the 4th preset digital to analog converter;
D., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 5; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 5; Input value as the 5th preset digital to analog converter;
E., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 3; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 3; Input value as the 6th preset digital to analog converter;
F., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 2; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 2; Input value as the 7th preset digital to analog converter;
G., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 1; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 1; Until the height state of voltage comparator output be height, then the height state that subtracts 1 output is low, determines that this is worth the preset value of tuning point for this reason;
(3) the retune point of adjacent high 100MHz, the value of preset digital to analog converter is that the value of a upper tuning point digital to analog converter adds 40 for the first time, repeat above-mentioned steps (1) (2), so repeat until institute is a little all tuning complete the preset tuning end of phase-locked loop.
Useful technique effect of the present invention:
It is accurately preset, time saving and energy saving that pre-setting method based on phase-locked loop automatic pre-set system can be realized phase-locked loop automatically fast by software, the efficiency while greatly improving batch production.Even more important is a bit when larger variation appears in ambient temperature, and software monitors preset value and occurs after relatively large deviation, can automatically recalibrate fast preset value, thereby guarantees that instrument can work always normally.
Accompanying drawing explanation
Fig. 1 is conventional phase locked loops system schematic.
Fig. 2 is phase-locked loop automatic pre-set system schematic disclosed by the invention.
Embodiment
2 pairs of the specific embodiment of the present invention are described further by reference to the accompanying drawings:
Phase-locked loop automatic pre-set system, comprises voltage controlled oscillator, integrator, phase discriminator and programmable chip, it is characterized in that, also comprises varactor doubler, tri-frequency divider, frequency mixer, directional coupler and sampler.Described varactor doubler comprises the first varactor doubler and the second varactor doubler.
The output of described voltage controlled oscillator connects the input of the first varactor doubler, the input of the output termination directional coupler of the first varactor doubler, the straight-through output of directional coupler connects the input of the second varactor doubler, the rf inputs of the output termination frequency mixer of the second varactor doubler, the local oscillator end of frequency mixer is connected with local oscillation signal F2, the medium frequency output end of frequency mixer connects the rf inputs of sampler, the local oscillator end of sampler is connected with local oscillation signal F1, local oscillation signal F1 connects the input of tri-frequency divider, the output of tri-frequency divider connects the reference edge of phase discriminator, the rf inputs of phase discriminator connects the medium frequency output end of sampler, the output of phase discriminator connects integrator, integrator connects the tuning end of voltage controlled oscillator through analog switch, error voltage is delivered to the tuning end of voltage controlled oscillator.The coupling output of described directional coupler connects the rf inputs of phase demodulation integrator, the reference edge of phase demodulation integrator connects the output of tri-frequency divider, the control end of phase demodulation integrator connects programmable chip, the output of phase demodulation integrator connects the first input end of voltage comparator, the second input of voltage comparator connects comparative voltage V1, the output of voltage comparator connects programmable chip, the digital input end of the output linking number weighted-voltage D/A converter of programmable chip, digital to analog converter becomes analog voltage signal by digital signal conversion, the analog output of digital to analog converter connects the tuning end of voltage controlled oscillator, preset voltage is delivered to the tuning end of voltage controlled oscillator, form closed-loop system.
Phase-locked loop output frequency in the situation that of locking is F, F=F2+N*F1+Fref, and wherein Fref is phase demodulation reference signal, and N is integer, and the value of N is determined by preset voltage.
Directional coupler is printed board microstrip line coupler.Comparative voltage V1 value is 0, and local frequency signal F1 is 100MHz, and sampled signal F2 is 4800MHz.The model of described voltage controlled oscillator is DCMO110250-8, the model of the first varactor doubler is HMC187MS8E, the model of the second varactor doubler is HMC189AMS8, the model of frequency mixer is SIM-153+, the model of sampler is MP7100, the model of tri-frequency divider is 74LVC163, the model of phase discriminator is 74VHC74, integrator is for take the integrating circuit that AD829JR is core, the model of analog switch is DG419DY, the model of phase demodulation integrator is ADF4106BRUZ, and the model of voltage comparator is LM339, and the model of programmable logic chip is EP4CE55F23C8N.The model of digital to analog converter is AD7945BRS, is the digital to analog converter of 12, digital port input range: 0-4095.
Pre-setting method based on realizing phase-locked loop automatic pre-set system, when larger variation appears in ambient temperature, software monitors preset value and occurs after relatively large deviation, carries out following steps:
(1) first analog switch is disconnected, make phase-locked loop in open loop situations; By the phase demodulation frequency that phase demodulation integrator is set of programmable chip, according to tuning point frequency and reference frequency, determine the frequency dividing ratio of rf inputs and reference input.The minimum working frequency points 5000MHz of described sampling ring of take is example, first programmable logic chip is controlled phase demodulation integrator and is made it the frequency that phase demodulation frequency is 1/3rd F1, the setting of divider of rf inputs is that 5000MHz is divided by phase demodulation frequency, the setting of divider of reference input be reference input frequency divided by phase demodulation frequency, the input value of the preset digital to analog converter for the first time by programmable chip is 100;
(2) according to the height state of Programmable Logic Controller detection voltage comparator output, determine the preset value of voltage controlled oscillator tuning point, its step is as follows:
A., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 40; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 40;
After time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output; If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 40; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 40;
If the height state that front and back detect for twice is identical, repeat a step, until the height state that front and back detect for twice is when different, as the input value of preset digital to analog converter for the second time, be transferred to step b;
B., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 20; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 20; As the input value of preset digital to analog converter for the third time;
C., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 10; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 10; Input value as the 4th preset digital to analog converter;
D., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 5; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 5; Input value as the 5th preset digital to analog converter;
E., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 3; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 3; Input value as the 6th preset digital to analog converter;
F., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 2; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 2; Input value as the 7th preset digital to analog converter;
G., after time delay is waited for one millisecond, Programmable Logic Controller detects the height state of voltage comparator output;
If the height state of output is low, on the basis of the input value of preset digital to analog converter, add 1; If the height state of output be height, on the basis of the input value of preset digital to analog converter, subtract 1; Until the height state of voltage comparator output be height, then the height state that subtracts 1 output is low, determines that this is worth the preset value of tuning point for this reason;
(3) the retune point of adjacent high 100MHz, the value of preset digital to analog converter is that the value of a upper tuning point digital to analog converter adds 40 for the first time, repeats above-mentioned steps (1) (2).
In initialization process, add depreciation and be followed successively by 40,20,10,5,3,2,1, until certain is once " height ", subtract " 1 " again and just become afterwards " low ", select current value for the value of the preset digital to analog converter in this tuning point, recording this, to be worth this point tuning complete.The retune point of adjacent high 100MHz, the value of preset digital to analog converter is that the value of a upper tuning point digital to analog converter adds 40 for the first time, later tuning methods is as the same in first point, so repeat until a little all tuning complete.
Certainly; more than explanation is only preferred embodiment of the present invention; the present invention is not limited to enumerate above-described embodiment; should be noted that; any those of ordinary skill in the art are under the guidance of this specification; that makes is allly equal to alternative, obvious variant, within all dropping on the essential scope of this specification, ought to be subject to protection of the present invention.