CN102647154A - Switched capacitor all-digital frequency mixer and anti-aliasing filter - Google Patents
Switched capacitor all-digital frequency mixer and anti-aliasing filter Download PDFInfo
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- CN102647154A CN102647154A CN2012101416053A CN201210141605A CN102647154A CN 102647154 A CN102647154 A CN 102647154A CN 2012101416053 A CN2012101416053 A CN 2012101416053A CN 201210141605 A CN201210141605 A CN 201210141605A CN 102647154 A CN102647154 A CN 102647154A
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Abstract
The invention discloses a switched capacitor all-digital frequency mixer and an anti-aliasing filter circuit. Current/voltage is sampled by use of a switched capacitor, the function of a digital filter is realized by virtue of charge sharing, filter parameters are dynamically regulated by multiple-digit high and low electrical levels, the phase-frequency characteristic of the digital filter based on the principle is optimized, voltage loss caused by using the switched capacitor filter can be lowered, and the gain of the whole circuit is improved.
Description
Technical field
The present invention relates to digital frequency mixer of a kind of improved switching capacity and frequency overlapped-resistable filter, relate in particular to a kind of method that can dynamically adjust the method for place in circuit capacitor's capacity and improve the filter phase-frequency characteristic.
Background technology
Some communication systems have certain requirement for the phase characteristic of signal, and also undistorted transmission has great significance for signal to optimize phase characteristic, yet existing digital filter is not paid close attention to phase-frequency characteristic too much.The present invention has improved the digital filter implementation, makes it be easier to optimize phase-frequency characteristic, and has proposed to optimize the method for phase-frequency characteristic.
For the linearity of the phase-frequency response that improves the switching capacity digital filter and as much as possible optimize amplitude-frequency characteristic, need to improve the ratio of historical electric capacity and rotation capacitance ratio in this filter and buffer memory electric capacity and rotation electric capacity.Yet because the restriction of technological factor, the excursion of ratio is very limited and meticulous inadequately, is unfavorable for improving frequency response characteristic.
Summary of the invention
For overcome the important parameter that under the existing processes condition, is difficult in integrated circuit to realize digital switching capacity filter on a large scale and accurate adjustment, the invention provides digital frequency mixer of a kind of switching capacity and frequency overlapped-resistable filter.The present invention can realize the wider of ratio between capacitor's capacity and the electric capacity and the more adjustment of pinpoint accuracy, realizes filter parameter adjustment more flexibly and makes the frequency response characteristic of filter, and especially phase-frequency characteristic is optimized better.
The technical scheme that the present invention adopted is: the circuit of digital frequency mixer of a kind of switching capacity and frequency overlapped-resistable filter, and entire circuit is made up of with the pseudo-differential mode identical two mixing and anti-aliasing filter circuit; Wherein, each mixing and anti-aliasing filter circuit comprise: m historical capacitor C h
1-Ch
m, 2nk rotation capacitor C r
1-Cr
2nk, an i buffer memory capacitor C b
1-Cb
iWith 4n+3+m+2nk+i metal-oxide-semiconductor Mh
1-Mh
mThe source electrode of all metal-oxide-semiconductors all links to each other with its substrate; Each electric capacity is metal-oxide-semiconductor of parallel connection all, and the input current source links to each other with the drain electrode of metal-oxide-semiconductor M1, the source electrode of metal-oxide-semiconductor M1 and historical capacitor C h
1One end, metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4, metal-oxide-semiconductor M
6..., metal-oxide-semiconductor M
4nDrain electrode link to each other m historical electric capacity back ground connection of connecting successively; Metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4, metal-oxide-semiconductor M
6..., metal-oxide-semiconductor M
4nSource electrode connect successively respectively k the rotation electric capacity after ground connection, metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4, metal-oxide-semiconductor M
6..., metal-oxide-semiconductor M
4nSource electrode respectively with metal-oxide-semiconductor M
3, metal-oxide-semiconductor M
5, metal-oxide-semiconductor M
7..., metal-oxide-semiconductor M
4n+1Source electrode link to each other; Metal-oxide-semiconductor M
3, metal-oxide-semiconductor M
5, metal-oxide-semiconductor M
7..., metal-oxide-semiconductor M
4n+1Drain electrode link to each other successively after respectively with metal-oxide-semiconductor M
4n+2With metal-oxide-semiconductor M
4n+3Drain electrode link to each other metal-oxide-semiconductor M
4n+2Source ground, metal-oxide-semiconductor M
4n+3The source electrode ground connection behind i the buffer memory electric capacity of connecting successively.
The invention has the beneficial effects as follows; The present invention obtains the more electric capacity of low-capacitance through attainable electric capacity on the integrated circuit under some definite process conditions is connected; And each electric capacity is parallelly connected with a switch MOS pipe, come in the control capacitance place in circuit or through digit order number control break-make by short circuit.Can realize the wider variation of ratio between capacitor's capacity and the electric capacity and control more accurately thus, comparing the fixing implementation of existing capacitor's capacity has had large increase.In addition, after realizing this goal, improve historical electric capacity and all can improve frequency response characteristic with rotation capacitance ratio and raising buffer memory electric capacity with the rotation capacitance ratio, especially the linearity of phase-frequency characteristic can be improved.
Description of drawings
Fig. 1 is the circuit theory diagrams of digital frequency mixer of switching capacity of the present invention and frequency overlapped-resistable filter
Fig. 2 is that the phase linearity principle that parameter a or b leveled off to 1 o'clock is explained sketch map;
Fig. 3 is the phase-frequency characteristic sketch map that parameter a or b leveled off to 1 o'clock;
Fig. 4 is that the phase linearity principle that parameter a or b leveled off to 0 o'clock is explained sketch map;
Fig. 5 is the phase-frequency characteristic sketch map that parameter a or b leveled off to 0 o'clock;
Fig. 6 is that parameter a or b value are 0.5 o'clock phase-frequency characteristic sketch map.
Embodiment
Principle of the present invention is: attainable electric capacity on the integrated circuit under some definite process conditions is connected obtains the more electric capacity of low-capacitance; And each electric capacity is parallelly connected with a switch MOS pipe, come in the control capacitance place in circuit or through digit order number control break-make by short circuit.Can realize the wider variation of ratio between capacitor's capacity and the electric capacity and control more accurately thus.
Below in conjunction with accompanying drawing and embodiment the inventive method is further specified.
Fig. 1 shows the circuit of digital frequency mixer of switching capacity and frequency overlapped-resistable filter, and among the figure, m is historical electric capacity number, and n is every group of rotation capacitances in series electric capacity number together for rotation capacitance group number, k, and i is a buffer memory electric capacity number.Entire circuit is made up of with the pseudo-differential mode identical two mixing and anti-aliasing filter circuit.Wherein, each mixing and anti-aliasing filter circuit comprise: m historical capacitor C h
1-Ch
m, 2nk rotation capacitor C r
1-Cr
2nk, an i buffer memory capacitor C b
1-Cb
iWith 4n+3+m+2nk+i metal-oxide-semiconductor Mh
1-Mh
mThe source electrode of all metal-oxide-semiconductors all links to each other with its substrate.Each electric capacity is metal-oxide-semiconductor of parallel connection all, and the input current source links to each other with the drain electrode of metal-oxide-semiconductor M1, the source electrode of metal-oxide-semiconductor M1 and historical capacitor C h1 one end, metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4, metal-oxide-semiconductor M
6..., metal-oxide-semiconductor M
4nDrain electrode link to each other m historical electric capacity back ground connection of connecting successively; Metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4, metal-oxide-semiconductor M
6..., metal-oxide-semiconductor M
4nSource electrode connect successively respectively k the rotation electric capacity after ground connection, metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4, metal-oxide-semiconductor M
6..., metal-oxide-semiconductor M
4nSource electrode respectively with metal-oxide-semiconductor M
3, metal-oxide-semiconductor M
5, metal-oxide-semiconductor M
7..., metal-oxide-semiconductor M
4n+1Source electrode link to each other; Metal-oxide-semiconductor M
3, metal-oxide-semiconductor M
5, metal-oxide-semiconductor M
7..., metal-oxide-semiconductor M
4n+1Drain electrode link to each other successively after respectively with metal-oxide-semiconductor M
4n+2With metal-oxide-semiconductor M
4n+3Drain electrode link to each other metal-oxide-semiconductor M
4n+2Source ground, metal-oxide-semiconductor M
4n+3The source electrode ground connection behind i the buffer memory electric capacity of connecting successively.M, n, k, i are natural number.
The course of work of existing switching capacity digital filter is: as sampling capacitance the electric current of input is collected jointly through some groups of rotation capacitor C r and historical capacitor C h, i.e. metal-oxide-semiconductor M
1Grid add the square-wave voltage of a certain frequency change, metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4..., metal-oxide-semiconductor M
2nGrid is the square-wave voltage of the frequency behind the Fractional-N frequency in addition then; These rotation electric capacity are alternately parallelly connected with historical electric capacity, share electric charge with the rotation electric capacity of historical electric capacity parallel connection, and not parallelly connected with historical electric capacity then is used for to next stage output, i.e. metal-oxide-semiconductor M
3, metal-oxide-semiconductor M
5..., metal-oxide-semiconductor M
2n+1Phase place and metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4..., metal-oxide-semiconductor M
2nPhase place opposite.The accumulation of electric charge and conversion have constituted a Finite Impulse Response filter and an iir digital filter in this process.In like manner, r is alternately parallelly connected with buffer memory capacitor C b for the rotation capacitor C, shares electric charge with its parallelly connected rotation electric capacity with buffer memory electric capacity.Entire circuit is worked with the pseudo-differential mode, so the square-wave voltage that all crystals tube grid voltage of the latter half except metal-oxide-semiconductor Mh, metal-oxide-semiconductor Mr, metal-oxide-semiconductor Ml is identical with the first half grid voltage frequency in addition, phase place is opposite.Voltage on the buffer memory electric capacity is as output the most at last.
Operation principle of the present invention also is that so main improvement has been to improve the performance of filter.Capacitor's capacity is fixed in the existing filter, is not easy to dynamically-adjusting parameter, also is unfavorable for optimizing phase-frequency characteristic.Among the present invention, again that each electric capacity is parallelly connected with the switch MOS pipe through capacitances in series with some selected appearance values, control its place in circuit or, come to adjust more neatly the parameter of filter by short circuit.Metal-oxide-semiconductor Mh
1-Mh
m, metal-oxide-semiconductor Mr
1-Mr
2nk, metal-oxide-semiconductor Mb
1-Mb
iGrid metal-oxide-semiconductor conducting when adding high level, will with the capacitance short-circuit of own parallel connection, add low level and be and turn-off and the electric capacity place in circuit of own parallel connection, thus the control capacitance size.
The transfer function of digital filter of the present invention is:
?
?；
In the formula, N, M are time sequence parameter.
All on the complex plane unit circle, meet linear phase characteristic fully the zero point of this filter.Except with a, the limit outside the relevant limit of b also all on the complex plane unit circle, meets linear phase characteristic fully.Two other then can be adjusted through changing the electric capacity ratio.As a (or b) when being tending towards 1, limit is tending towards on the complex plane unit circle, and it is linear that phase-frequency characteristic is tending towards, like Fig. 2, shown in Figure 3.
As a (or b) when being tending towards 0, limit is tending towards initial point (0,0), and it is linear that phase-frequency characteristic is tending towards, like Fig. 4, shown in Figure 5.
When limit during in other positions, then can cause the linearity variation of phase-frequency characteristic, as shown in Figure 6.
Abscissa is a normalized frequency among Fig. 3, Fig. 5, Fig. 6, and ordinate is a phase place.
In addition, under the existing process conditions, single electric capacity and single capacitor's capacity ratio maximum can only reach about 10, and adopt the method for a plurality of electric capacity parallel connections to improve a, and the value of b then can cause cost to increase because of electric capacity in the integrated circuit is with high costs.Adopt the circuit structure after the improvement that proposes among the present invention in theory can with a, the value of b improves exponentially with relatively low cost (can improve parameter a, the value of b because of using some attainable minimum capacities series connection).Need to reduce a, during the b value in like manner.And through this implementation method, when after voltage signal amplifies through mutual conductance, electric current being imported as filter, less Ch helps improving voltage gain, and this can realize through the implementation of describing among the present invention.
Claims (1)
1. the circuit of digital frequency mixer of switching capacity and frequency overlapped-resistable filter is characterized in that entire circuit is made up of with the pseudo-differential mode identical two mixing and anti-aliasing filter circuit; Wherein, each mixing and anti-aliasing filter circuit comprise: m historical capacitor C h
1-Ch
m, 2nk rotation capacitor C r
1-Cr
2nk, an i buffer memory capacitor C b
1-Cb
iWith 4n+3+m+2nk+i metal-oxide-semiconductor Mh
1-Mh
mThe source electrode of all metal-oxide-semiconductors all links to each other with its substrate; Each electric capacity is metal-oxide-semiconductor of parallel connection all, and the input current source links to each other with the drain electrode of metal-oxide-semiconductor M1, the source electrode of metal-oxide-semiconductor M1 and historical capacitor C h
1One end, metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4, metal-oxide-semiconductor M
6..., metal-oxide-semiconductor M
4nDrain electrode link to each other m historical electric capacity back ground connection of connecting successively; Metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4, metal-oxide-semiconductor M
6..., metal-oxide-semiconductor M
4nSource electrode connect successively respectively k the rotation electric capacity after ground connection, metal-oxide-semiconductor M
2, metal-oxide-semiconductor M
4, metal-oxide-semiconductor M
6..., metal-oxide-semiconductor M
4nSource electrode respectively with metal-oxide-semiconductor M
3, metal-oxide-semiconductor M
5, metal-oxide-semiconductor M
7..., metal-oxide-semiconductor M
4n+1Source electrode link to each other; Metal-oxide-semiconductor M
3, metal-oxide-semiconductor M
5, metal-oxide-semiconductor M
7..., metal-oxide-semiconductor M
4n+1Drain electrode link to each other successively after respectively with metal-oxide-semiconductor M
4n+2With metal-oxide-semiconductor M
4n+3Drain electrode link to each other metal-oxide-semiconductor M
4n+2Source ground, metal-oxide-semiconductor M
4n+3The source electrode ground connection behind i the buffer memory electric capacity of connecting successively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210141605.3A CN102647154B (en) | 2012-05-09 | 2012-05-09 | Switched capacitor all-digital frequency mixer and anti-aliasing filter |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210141605.3A CN102647154B (en) | 2012-05-09 | 2012-05-09 | Switched capacitor all-digital frequency mixer and anti-aliasing filter |
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| CN102647154A true CN102647154A (en) | 2012-08-22 |
| CN102647154B CN102647154B (en) | 2014-12-03 |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040070461A1 (en) * | 2001-02-13 | 2004-04-15 | Jesper Fredriksson | Oscillators with active higher-in-order phase shift filtering |
| CN101741346A (en) * | 2008-11-19 | 2010-06-16 | 中国科学院微电子研究所 | Transconductance-capacitance double second-order unit for realizing zero pole high-order filter |
| CN101483408B (en) * | 2009-01-23 | 2011-08-17 | 北京朗波芯微技术有限公司 | Passive frequency mixer |
-
2012
- 2012-05-09 CN CN201210141605.3A patent/CN102647154B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040070461A1 (en) * | 2001-02-13 | 2004-04-15 | Jesper Fredriksson | Oscillators with active higher-in-order phase shift filtering |
| CN101741346A (en) * | 2008-11-19 | 2010-06-16 | 中国科学院微电子研究所 | Transconductance-capacitance double second-order unit for realizing zero pole high-order filter |
| CN101483408B (en) * | 2009-01-23 | 2011-08-17 | 北京朗波芯微技术有限公司 | Passive frequency mixer |
Non-Patent Citations (1)
| Title |
|---|
| 王津,虞小鹏: "《基于TSMC0.25μm工艺的5GHz31/32双模预分频器的设计》", 《现代机械》 * |
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