CN107769776A - A kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises - Google Patents
A kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises Download PDFInfo
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- CN107769776A CN107769776A CN201711084846.8A CN201711084846A CN107769776A CN 107769776 A CN107769776 A CN 107769776A CN 201711084846 A CN201711084846 A CN 201711084846A CN 107769776 A CN107769776 A CN 107769776A
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- notch filter
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- 230000000694 effects Effects 0.000 claims abstract description 20
- 230000003595 spectral effect Effects 0.000 claims abstract description 4
- 238000004088 simulation Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 230000005611 electricity Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009022 nonlinear effect Effects 0.000 description 2
- 238000013139 quantization Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000007493 shaping process Methods 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 230000001629 suppression Effects 0.000 description 2
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Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/16—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
- H03L7/18—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
- H03L7/087—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal using at least two phase detectors or a frequency and phase detector in the loop
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M3/00—Conversion of analogue values to or from differential modulation
- H03M3/30—Delta-sigma modulation
Abstract
The invention discloses a kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises, including gear selection module, multi-stage cascade modulation module and notch filter module, the gear selection module selection decimal interception digit and corresponding notch filter circuit；The notch filter module first carries out portion intercepts before input fractional value enters multi-stage cascade modulation module, then numerical value is reverted to original desired value by notch filter circuit after the processing of multi-stage cascade modulation module and reduces high frequency treatment noise spectral density；The present invention proposes a kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises, the configurable notch filter structure of the modulator and its circuit, the frequency that output high level occurs can be reduced, there is extra filter effect to high-frequency noise in addition.
Description
Technical field
The present invention relates to radio frequency, field of analog integrated circuit, and in particular, it, which is related to one kind, can reduce fractional frequency division frequency
The modulator and the modulator circuit that rate synthesizer high-frequency noises influence.
Background technology
At present, fractional frequency division frequency synthesizer all employ dual-mode frequency divider, this inevitably introduce quantizing noise and
Fractional stray.It is routinely to introduce Delta-Sigma modulators (DSM) to solve this problem to solve this problem.The mould
Quantization error in system can be effectively converted into random noise by block, and be transferred in higher frequency, these high frequencies
Noise can because loop low-frequency filter characteristicses and be suppressed.But carried out using the Delta-Sigma modulators of traditional structure
Noise shaping can not be completely eliminated quantizing noise, and the quantizing noise amplitude exported is larger, on the one hand when loop bandwidth compared with
When big, high-frequency noise can not be suppressed by loop filter, it will cause out-of-band noise penalty, on the other hand, Delta-
The output level excursion too conference of Sigma modulators causes more in phase frequency detector (PFD) and charge pump (CP) circuit
Add significant nonlinear effect, and increase the in-band noise of frequency synthesizer.
The content of the invention
Instant invention overcomes the deficiencies in the prior art, propose a kind of new configurable notch filter structure, it is possible to reduce
The frequency that high level occurs is exported, there is extra filter effect to high-frequency noise in addition.
Technical scheme is as follows：
A kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises, including
Gear selection module, multi-stage cascade modulation module and notch filter module, the gear selection module selection decimal interception digit
And corresponding notch filter circuit；The notch filter module is advanced before input fractional value enters multi-stage cascade modulation module
Row portion intercepts, then numerical value is set to revert to original expectation by notch filter circuit after the processing of multi-stage cascade modulation module
It is worth and reduces high frequency treatment noise spectral density.
Further, the phase frequency detector is connected with the reference frequency of reference clock signal.
Further, the modulator circuit also include phase frequency detector, charge pump, loop filter, voltage controlled oscillator, point
Frequency device, the modulator and dual-mode frequency divider for reducing high frequency noise effect；
Connected at the phase frequency detector and the switch of charge pump, the charge pump is connected with loop filter, the ring
Path filter includes first resistor, the first electric capacity and the second electric capacity, the first resistor and the series connection of the first electric capacity, the first electric capacity
One end is grounded, the second electric capacity one end ground connection；One end of the voltage controlled oscillator and frequency divider, one end of dual-mode frequency divider connect
Connect, one end connection of the dual-mode frequency divider and phase frequency detector, the modulator for reducing high frequency noise effect is connected to double
On mould frequency divider, the modulator for reducing high frequency noise effect sets the interface of integer frequency ratio and fractional frequency division ratio.
Advantage is the present invention compared with prior art：New configurable notch filter structure, it is possible to reduce high in output
It is worth the frequency occurred, has extra filter effect to high-frequency noise in addition, Delta-Sigma modulators is reached more excellent noise
Rejection ability.The probability of high level (- 3, -2,3,4) appearance can be greatly reduced；Simultaneously to (fs/2N, fs/ near specific frequency
2N-1 etc., wherein fs be DSM working frequency) noise have certain filter effect.
Brief description of the drawings
Fig. 1 is the structural representation of the present invention；
Fig. 2 is the structure chart of the modulator circuit of the present invention；
Fig. 3 is the effect contrast figure of the modulator and conventional modulated device of the reduction high frequency noise effect of the present invention；
Fig. 4 is the present invention and comparison diagram of the conventional modulated device in power output spectrum density；
Fig. 5 is the comparison diagram of the present invention and the system phase noise Simulation result of traditional frequency synthesizer.
Embodiment
The present invention is further described with reference to the accompanying drawings and detailed description.
As shown in figure 1, a kind of modulator for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises and the modulation
Device circuit, including gear selection module, multi-stage cascade modulation module and notch filter module, the gear selection module selection are small
Number interception digit and corresponding notch filter circuit, and integer frequency ratio is directly entered in multi-stage cascade modulation module.Institute
State notch filter module and first carry out portion intercepts before input fractional value enters multi-stage cascade modulation module, then in multi-stage cascade
Numerical value is reverted to original desired value by notch filter circuit after modulation module processing and reduce high frequency treatment noise spectral density.
The phase frequency detector is connected with the reference frequency of reference clock signal.The modulator for reducing high frequency noise effect is made an uproar
Sound transfer formula NTF (z) is equation below (1)：
Wherein N is the gear of gear selection module, and z is the input complex variable of transform formula, and k is the change in summation symbol
Amount.
As shown in Fig. 2 the modulator circuit also includes phase frequency detector, charge pump, loop filter (LPF), voltage-controlled shaken
Swing device (VCO), frequency divider (DIV), the modulator and dual-mode frequency divider for reducing high frequency noise effect.The phase frequency detector and electricity
Connected at the switch of lotus pump, the charge pump is connected with loop filter, and the loop filter includes first resistor, the first electricity
Hold and the second electric capacity, the first resistor and the series connection of the first electric capacity, one end ground connection of the first electric capacity, second electric capacity one terminate
Ground；One end of the voltage controlled oscillator and frequency divider, one end connection of dual-mode frequency divider, the dual-mode frequency divider and frequency and phase discrimination
One end connection of device, the modulator for reducing high frequency noise effect are connected on dual-mode frequency divider, the reduction high-frequency noise
The modulator of influence sets the interface of integer frequency ratio and fractional frequency division ratio.
Traditional Delta-Sigma modulators typically realize that the modulator can using three rank multi-stage cascade modulator structures
So that the quantization error in system to be effectively converted into random noise, and it is transferred in higher frequency, these high frequencies are made an uproar
Sound can be suppressed because of the low-frequency filter characteristicses of loop.But carry out noise using the Delta-Sigma modulators of traditional structure
Quantizing noise can not be completely eliminated in shaping, and the quantizing noise amplitude exported is larger, on the one hand when loop bandwidth is larger,
High-frequency noise can not be suppressed by loop filter, it will cause out-of-band noise penalty, on the other hand, Delta-Sigma is adjusted
The output level excursion too conference of device processed causes more significant nonlinear effect in PFD and CP circuits, and increases frequency
The in-band noise of rate synthesizer.
And the new gear selection module based on the modulator for reducing high frequency noise effect can increase according to the actual requirements
Add, be not limited to four gears as shown in Figure 2.And according to noise shift formula NTF (z) using the citing of four gears when N as 0,1,
2nd, 3 when, noise transfer formula difference it is as follows：
NTF(z)N=0=(1-z-1)3
By taking N=3 pattern as an example, newly-increased notch filter module is modulated equivalent in input fractional value into multi-stage cascade
First carried out before module except 8 operations, then after the processing of multi-stage cascade modulation module before last output by noise shift formula (from
Equivalent to carrying out multiplying 8 operations to signal from the point of view of time domain), numerical value is recovered desired value.So as to be greatly reduced high level (- 3 ,-
2nd, 3, the probability 4) occurred；Simultaneously to (fs/2N, fs/2N-1 etc., wherein fs are DSM working frequency) near specific frequency
Noise has certain filter effect.Its simulation result is as shown in Figures 3 to 5：
As shown in figure 3, the output numerical value scope of Delta-Sigma modulator traditional structures is -3~4, add the present invention's
After improved structure, the probability that high level (- 3, -2,3,4) occurs greatly reduces, -3 and 4 probability of occurrence even almost 0.
As shown in figure 4, the power output spectrum density of the traditional structure of Delta-Sigma modulators is as shown in the left diagram, add
After the improved structure of the present invention, filter effect is had at specific frequency, high-frequency noise can obtain a certain degree of suppression.
It is N=3 result shown in figure, in this mode, to there is nearly 30dB filter effect at fs/8 frequencies, to fs/4 and fs/
2 also have certain filter effect.
As shown in figure 5, the figure left side is the system phase using the frequency synthesizer of Delta-Sigma modulator traditional structures
Noise Simulation result, the right are the system phase noise Simulation simulation result using the frequency synthesizer of structure of the present invention.At it
In the case that his module and loop parameter are constant, introducing the structure of the present invention, can to obtain DSM high frequency phase noise very big
The suppression of degree.
Described above is only the preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art
Member, without departing from the inventive concept of the premise, can also make some improvements and modifications, these improvements and modifications also should be regarded as
In the scope of the present invention.
Claims (3)
1. a kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises, its feature
It is, including gear selection module, multi-stage cascade modulation module and notch filter module, the gear selection module select decimal
Intercept digit and corresponding notch filter circuit；The notch filter module enters multi-stage cascade modulation mould in input fractional value
Portion intercepts are first carried out before block, then numerical value is reverted to original by notch filter circuit after the processing of multi-stage cascade modulation module
The desired value of elder generation simultaneously reduces high frequency treatment noise spectral density.
2. it is according to claim 1 it is a kind of reduce fractional frequency division frequency synthesizer high-frequency noises influence modulator and
The modulator circuit, it is characterised in that the phase frequency detector is connected with the reference frequency of reference clock signal.
3. it is according to claim 2 it is a kind of reduce fractional frequency division frequency synthesizer high-frequency noises influence modulator and
The modulator circuit, it is characterised in that the modulator circuit also includes phase frequency detector, charge pump, loop filter, voltage-controlled shaken
Swing device, frequency divider, the modulator and dual-mode frequency divider for reducing high frequency noise effect；
Connected at the phase frequency detector and the switch of charge pump, the charge pump is connected with loop filter, the loop filter
Ripple device includes first resistor, the first electric capacity and the second electric capacity, the first resistor and the series connection of the first electric capacity, one end of the first electric capacity
Ground connection, the second electric capacity one end ground connection；One end of the voltage controlled oscillator and frequency divider, one end connection of dual-mode frequency divider,
One end connection of the dual-mode frequency divider and phase frequency detector, the modulator for reducing high frequency noise effect are connected to bimodulus point
On frequency device, the modulator for reducing high frequency noise effect sets the interface of integer frequency ratio and fractional frequency division ratio.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711084846.8A CN107769776A (en) | 2017-11-07 | 2017-11-07 | A kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711084846.8A CN107769776A (en) | 2017-11-07 | 2017-11-07 | A kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises |
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| Publication Number | Publication Date |
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| CN107769776A true CN107769776A (en) | 2018-03-06 |
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| CN201711084846.8A Pending CN107769776A (en) | 2017-11-07 | 2017-11-07 | A kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6236703B1 (en) * | 1998-03-31 | 2001-05-22 | Philsar Semiconductor Inc. | Fractional-N divider using a delta-sigma modulator |
| US20110156773A1 (en) * | 2009-12-29 | 2011-06-30 | Stephen Mark Beccue | Low Noise Fractional Divider Using A Multiphase Oscillator |
| CN103163829A (en) * | 2011-12-13 | 2013-06-19 | 东芝机械株式会社 | Servo-controller and adjusting method thereof |
| US20140241467A1 (en) * | 2013-02-27 | 2014-08-28 | Microsemi Semiconductor Ulc | Phase locked loop frequency synthesizer with reduced jitter |
| US9762259B1 (en) * | 2017-01-09 | 2017-09-12 | Texas Instruments Incorporated | Sigma-delta analog-to-digital converter with auto tunable loop filter |
| CN207732750U (en) * | 2017-11-07 | 2018-08-14 | 杭州城芯科技有限公司 | A kind of modulator reducing the influence of fractional frequency division frequency synthesizer high-frequency noises |
-
2017
- 2017-11-07 CN CN201711084846.8A patent/CN107769776A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6236703B1 (en) * | 1998-03-31 | 2001-05-22 | Philsar Semiconductor Inc. | Fractional-N divider using a delta-sigma modulator |
| US20110156773A1 (en) * | 2009-12-29 | 2011-06-30 | Stephen Mark Beccue | Low Noise Fractional Divider Using A Multiphase Oscillator |
| CN103163829A (en) * | 2011-12-13 | 2013-06-19 | 东芝机械株式会社 | Servo-controller and adjusting method thereof |
| US20140241467A1 (en) * | 2013-02-27 | 2014-08-28 | Microsemi Semiconductor Ulc | Phase locked loop frequency synthesizer with reduced jitter |
| US9762259B1 (en) * | 2017-01-09 | 2017-09-12 | Texas Instruments Incorporated | Sigma-delta analog-to-digital converter with auto tunable loop filter |
| CN207732750U (en) * | 2017-11-07 | 2018-08-14 | 杭州城芯科技有限公司 | A kind of modulator reducing the influence of fractional frequency division frequency synthesizer high-frequency noises |
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Inventor after: Li Haoming Inventor after: Li Guoru Inventor after: Wang Tengjia Inventor after: Zhou Suping Inventor after: Wang Xiaofeng Inventor after: Shen Yupeng Inventor after: Chen Xubin Inventor before: Li Haoming Inventor before: Li Guoru Inventor before: Liu Jiarui Inventor before: Wang Tengjia Inventor before: Zhou Suping Inventor before: Wang Xiaofeng Inventor before: Shen Yupeng Inventor before: Chen Xubin |