CN207732750U - A kind of modulator reducing the influence of fractional frequency division frequency synthesizer high-frequency noises - Google Patents
A kind of modulator reducing the influence of fractional frequency division frequency synthesizer high-frequency noises Download PDFInfo
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- CN207732750U CN207732750U CN201721473154.8U CN201721473154U CN207732750U CN 207732750 U CN207732750 U CN 207732750U CN 201721473154 U CN201721473154 U CN 201721473154U CN 207732750 U CN207732750 U CN 207732750U
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- frequency
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- fractional
- notch filter
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Abstract
The modulator of Delta_sigma high frequency noise effects and the modulator circuit in fractional frequency division frequency synthesizer are reduced the utility model discloses a kind of, 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 so that 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 modulator of Delta_sigma high frequency noise effects and the modulator circuit in fractional frequency division frequency synthesizer are reduced the utility model proposes a kind of, the configurable notch filter structure of the modulator and its circuit, the frequency that output high level occurs can be reduced, in addition there is additional filter effect to high-frequency noise.
Description
Technical field
The utility model is related to radio frequency, field of analog integrated circuit, more specifically, it, which is related to one kind, can reduce decimal point
The modulator of Delta_sigma high frequency noise effects and the modulator circuit in frequency frequency synthesizer.
Background technology
Currently, fractional frequency division frequency synthesizer all employs dual-mode frequency divider, this inevitably introduce quantizing noise and
Fractional stray.In order to solve this problem, it is routinely to introduce Delta-Sigma modulators (DSM) to solve the problems, such as this.The mould
Quantization error in system can be effectively converted into random noise by block, and is transferred in higher frequency, these high frequencies
Noise can because loop low-frequency filter characteristics and be suppressed.But it is carried out using the Delta-Sigma modulators of traditional structure
Noise shaping can not completely eliminate quantizing noise, and the quantizing noise amplitude exported is larger, on the one hand when loop bandwidth compared with
When big, high-frequency noise cannot be suppressed by loop filter, it will cause out-of-band noise penalty, on the other hand, Delta-
The output level variation range too conference of Sigma modulators causes more in phase frequency detector (PFD) and charge pump (CP) circuit
Add significant nonlinear effect, and increases the in-band noise of frequency synthesizer.
Invention content
The utility model overcomes the deficiencies in the prior art, proposes a kind of new configurable notch filter structure, can be with
The frequency that output high level occurs is reduced, in addition there is additional filter effect to high-frequency noise.
The technical solution of the utility model is as follows：
It is a kind of to reduce the modulator of Delta_sigma high frequency noise effects and the modulation in fractional frequency division frequency synthesizer
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；The notch filter module enters multi-stage cascade modulation in input fractional value
Portion intercepts are first carried out before module, then so that numerical value is reverted to by notch filter circuit after the processing of multi-stage cascade modulation module
Original desired value simultaneously reduces high frequency treatment noise spectral density.
Further, the phase frequency detector is connected with the reference frequency of reference clock signal.
Further, which further includes phase frequency detector, charge pump, loop filter, voltage controlled oscillator, divides
Frequency device, the modulator and dual-mode frequency divider for reducing high frequency noise effect；
It is 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 capacitance and the second capacitance, and the first resistor and the first capacitance are connected, the first capacitance
One end is grounded, second capacitance one end ground connection；One end of the voltage controlled oscillator and frequency divider, dual-mode frequency divider one end connect
It connects, 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 interface of modulator the setting integer frequency ratio and fractional frequency division ratio for reducing high frequency noise effect.
Advantage is the utility model compared with prior art：New configurable notch filter structure, it is possible to reduce output
The frequency that middle high level occurs, in addition has high-frequency noise additional filter effect, Delta-Sigma modulators is made to reach more excellent
Noise inhibiting ability.The probability of high level (- 3, -2,3,4) appearance can be greatly reduced；Simultaneously to (fs/ near specific frequency
2N, fs/2N-1 etc., wherein fs be DSM working frequency) noise have certain filter effect.
Description of the drawings
Fig. 1 is the structural schematic diagram of the utility model；
Fig. 2 is the structure chart of the modulator circuit of the utility model；
Fig. 3 is the effect contrast figure of the modulator and conventional modulated device of the reduction high frequency noise effect of the utility model；
Fig. 4 is the utility model and comparison diagram of the conventional modulated device in output power spectrum density；
Fig. 5 is the comparison diagram of the system phase noise Simulation result of the utility model and traditional frequency synthesizer.
Specific implementation mode
The utility model is further illustrated with reference to the accompanying drawings and detailed description.
As shown in Figure 1, a kind of modulation reducing Delta_sigma high frequency noise effects in fractional frequency division frequency synthesizer
Device and the modulator circuit, including gear selection module, multi-stage cascade modulation module and notch filter module, the gear selection
Module selects decimal interception digit and corresponding notch filter circuit, and integer frequency ratio is made to be directly entered multi-stage cascade modulation
In module.The notch filter module first carries out portion intercepts before input fractional value enters multi-stage cascade modulation module, then
So that 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 phase frequency detector is connected with the reference frequency of reference clock signal.The reduction high frequency noise effect
Modulator noise transfer formula NTF (z) be following formula (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 summing symbol
Amount.
As shown in Fig. 2, the modulator circuit further includes phase frequency detector, charge pump, loop filter (LPF), voltage-controlled shakes
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
It is 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 capacitance, the first resistor and the series connection of the first capacitance, one end ground connection of the first capacitance, second capacitance one terminate
Ground；One end connection of one end of the voltage controlled oscillator and frequency divider, dual-mode frequency divider, the dual-mode frequency divider and frequency and phase discrimination
One end of device connects, and the modulator for reducing high frequency noise effect is connected on dual-mode frequency divider, the reduction high-frequency noise
The interface of modulator the setting integer frequency ratio and fractional frequency division ratio of influence.
Traditional Delta-Sigma modulators generally realize that the modulator can using three rank multi-stage cascade modulator structures
It the quantization error in system to be effectively converted into random noise, and is transferred in higher frequency, these high frequencies are made an uproar
Sound can be suppressed because of the low-frequency filter characteristics of loop.But carry out noise using the Delta-Sigma modulators of traditional structure
Shaping can not completely eliminate quantizing noise, and the quantizing noise amplitude exported is larger, on the one hand when loop bandwidth is larger,
High-frequency noise cannot be suppressed by loop filter, it will cause out-of-band noise penalty, on the other hand, Delta-Sigma tune
The output level variation range 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 novel gear selection module based on the modulator for reducing high frequency noise effect can increase according to actual demand
Add, is not limited to four gears as shown in Figure 2.And according to noise shift formula NTF (z) with four gears citing when N be 0,1,
2,3 when, noise shift formula difference it is as follows：
NTF(z)N=0=(1-z-1)3
By taking the pattern of N=3 as an example, newly-increased notch filter module is equivalent to enters multi-stage cascade modulation in input fractional value
Before module first carry out except 8 operation, then multi-stage cascade modulation module processing after finally output before by noise shift formula (from
It is equivalent to from the point of view of time domain and signal is carried out to multiply 8 operations), so that numerical value is restored desired value.So as to be greatly reduced high level (- 3 ,-
2,3, the 4) probability occurred；Simultaneously to (fs/2N, fs/2N-1 etc., wherein fs are the working frequency of DSM) 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 ranging from -3~4 of Delta-Sigma modulator traditional structures, it is new to be added this practicality
After the improved structure of type, the probability that high level (- 3, -2,3,4) occurs greatly reduces, and -3 and 4 probability of occurrence is even almost
0。
As shown in figure 4, the output power spectrum density of the traditional structure of Delta-Sigma modulators is as shown in the left diagram, it is added
After the improved structure of the utility model, filter effect is had at specific frequency point, high-frequency noise can obtain a degree of
Inhibit.It is as shown in the figure for N=3's as a result, in this mode, to there is the nearly filter effect of 30dB at fs/8 frequencies, to fs/4
Also there is certain filter effect with fs/2.
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 is as a result, the right is the system phase noise Simulation simulation result using the frequency synthesizer of the utility model structure.
In the case of other modules and constant loop parameter, the high frequency phase noise of DSM can be made by introducing the structure of the utility model
Significantly inhibited.
The above is only the preferred embodiment of the utility model, it is noted that for the common skill of the art
Art personnel can also make several improvements and modifications without departing from the concept of the premise utility, these improvements and modifications
Also it should be regarded as in scope of protection of the utility model.
Claims (3)
1. a kind of modulator reducing the influence of fractional frequency division frequency synthesizer high-frequency noises, which is characterized in that including gear
Selecting module, multi-stage cascade modulation module and notch filter module, gear selection module selection decimal interception digit and
Corresponding notch filter circuit；The notch filter module first carry out portion before input fractional value enters multi-stage cascade modulation module
Divide interception, then so that numerical value is reverted to original desired value simultaneously by notch filter circuit after the processing of multi-stage cascade modulation module
Reduce high frequency treatment noise spectral density.
2. a kind of modulator reducing the influence of fractional frequency division frequency synthesizer high-frequency noises according to claim 1,
It is characterized in that, the modulator circuit further include phase frequency detector, charge pump, loop filter, voltage controlled oscillator, frequency divider,
Reduce the modulator and dual-mode frequency divider of high frequency noise effect；
It is connected at the phase frequency detector and the switch of charge pump, the charge pump is connected with loop filter, the loop filter
Wave device includes first resistor, the first capacitance and the second capacitance, and the first resistor and the first capacitance are connected, one end of the first capacitance
Ground connection, second capacitance one end ground connection；One end connection of one end of the voltage controlled oscillator and frequency divider, dual-mode frequency divider,
One end of the dual-mode frequency divider and phase frequency detector connects, and the modulator for reducing high frequency noise effect is connected to bimodulus point
On frequency device, the interface of modulator the setting integer frequency ratio and fractional frequency division ratio for reducing high frequency noise effect.
3. a kind of modulator reducing the influence of fractional frequency division frequency synthesizer high-frequency noises according to claim 2,
It is characterized in that, the phase frequency detector is connected with the reference frequency of reference clock signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201721473154.8U CN207732750U (en) | 2017-11-07 | 2017-11-07 | A kind of modulator reducing the influence of fractional frequency division frequency synthesizer high-frequency noises |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201721473154.8U CN207732750U (en) | 2017-11-07 | 2017-11-07 | A kind of modulator reducing the influence of fractional frequency division frequency synthesizer high-frequency noises |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107769776A (en) * | 2017-11-07 | 2018-03-06 | 杭州城芯科技有限公司 | A kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises |
| CN109936361A (en) * | 2019-04-03 | 2019-06-25 | 杭州城芯科技有限公司 | A kind of fractional frequency division frequency synthesizer containing PFD/DAC quantizing noise technology for eliminating |
-
2017
- 2017-11-07 CN CN201721473154.8U patent/CN207732750U/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107769776A (en) * | 2017-11-07 | 2018-03-06 | 杭州城芯科技有限公司 | A kind of modulator and the modulator circuit for reducing the influence of fractional frequency division frequency synthesizer high-frequency noises |
| CN107769776B (en) * | 2017-11-07 | 2024-06-07 | 杭州城芯科技有限公司 | Modulator circuit capable of reducing high-frequency noise influence in fractional frequency synthesizer |
| CN109936361A (en) * | 2019-04-03 | 2019-06-25 | 杭州城芯科技有限公司 | A kind of fractional frequency division frequency synthesizer containing PFD/DAC quantizing noise technology for eliminating |
| CN109936361B (en) * | 2019-04-03 | 2020-08-04 | 杭州城芯科技有限公司 | Decimal frequency division frequency synthesizer containing PFD/DAC quantization noise elimination technology |
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Granted publication date: 20180814 Termination date: 20201107 |