CN101364787A - Noise filter - Google Patents
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- CN101364787A CN101364787A CNA2007101399803A CN200710139980A CN101364787A CN 101364787 A CN101364787 A CN 101364787A CN A2007101399803 A CNA2007101399803 A CN A2007101399803A CN 200710139980 A CN200710139980 A CN 200710139980A CN 101364787 A CN101364787 A CN 101364787A
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Abstract
The invention relates to a noise filter, which comprises a segment of transmission line. The noise filter can produce high impedance to secondary harmonic wave of an LC oscillator by the length adjustment and the characteristics of the transmission line so as to eliminate the noise of the LC oscillator. The noise filter can control the switching of a plurality of switches according to the oscillation frequency of the LC oscillator, so that an AC ground point is provided to adjust the length of the transmission line. Accordingly, the noise filter can provides a transmission line with a proper length for each oscillation frequency, so as to eliminate the noise of the LC oscillator by using the characteristics of the transmission line.
Description
Technical field
The present invention relates to a kind of noise filter, particularly come the noise filter of oscillation-damped device noise relevant for a kind of characteristic of utilizing transmission line.
Background technology
Oscillator belongs to the some of receiver in the communication system (Receiver), is playing the part of the function with the signal lifting frequency in communication system.In all specifications of oscillator, most important project is a phase noise.The quality of phase noise directly influences the signal noise ratio (Signal tonoise ratio) of receiver, adjacent interference frequently, characteristics such as the frequency range of reflector.Now the trend of communication system be high-frequency, multiband to reach the requirement of high transfer rate, therefore be applicable to high frequency, and have the low phase noise oscillator that multiple frequency band switches and in system, play the part of critical role.In the integrated circuit, oscillator often realizes that in inductance capacitance resonance (the Cross-couple LC tank) mode of mutual back coupling be called differential type LC oscillator, the oscillator of this kind mode has lower phase noise than ring oscillator (Ringoscillator).In requiring harsh day by day communication system, for satisfying low-power consumption and high signal noise ratio simultaneously, low phase noise is more important, also therefore produces the circuit framework of differential type LC oscillator phase being done inhibition, general term noise filter (Noise filter).
Having delivered at present the noise filter that is used for differential type LC oscillator all forms band with single inductance capacitance and refuses the resonant cavity mode and realize that fixing inductance and capacitance limit it and be applicable to single frequency band, can't satisfy the operation of multiband simultaneously.The number that noise filter suppresses phase noise is limit by two factors: the frequency accuracy that inductance quality factor (Q factor:Quality factor) and band are refused resonant cavity.Along with the increase of frequency of operation, the parasitic antenna effect in the integrated circuit is obvious further, has reduced the quality factor and the suitable frequency range of inductance, and is with the resonance frequency of refusing resonant cavity also to drift about with this ghost effect.Therefore the system of noise filter of realizing in this way and inapplicable high frequency, multiband.
See also Figure 1A, for differential type LC oscillator is not had a circuit framework figure of current source, and Figure 1B, be output voltage and the load impedance oscillogram of Figure 1A.When vibration takes place, the two ends of differential output have the voltage output of the high amplitude of oscillation (high swing), make the gate-to-drain voltage difference (VGD) of transistor Q2 wherein much larger than critical voltage (Vt, threshold voltage), and enter three polar regions (triode region); The gate-to-drain voltage difference of another transistor Q1 is much smaller than-Vt, the approximate state of turning off (off).When differential output voltage is bigger, the channel impedance (rds) of transistor Q2 that operates in three polar regions is littler, forms a resonant cavity (resonator) alternating current path over the ground, causes the energy loss of resonant cavity.In complete cycle of oscillation, two transistor Q1, Q2 of differential centering hand over and operate in three polar regions mutually, this kind mechanism makes the channel impedance of transistor Q1, Q2 become resonant cavity load over the ground in the mode of twice frequency of oscillation, reduced the average earth impedance in the cycle of oscillation, be the quality factor that has reduced resonant cavity, that is improve the phase noise of oscillator.
See also Fig. 2 A, be the circuit framework figure of differential type LC vibration utensil current source, and Fig. 2 B, be output voltage and the load impedance oscillogram of Fig. 2 B.When vibration takes place, even transistor Q1 of one of them or Q2 enter three polar regions, because the input impedance of ideal current source I is infinitely great, so for alternating current, and none is to the circulation path on ground.The low channel impedance that also therefore is operated in three polar region transistors (as the Q2 of Fig. 2 A) can't become the load of resonant cavity, and meaning is that therefore its quality factor can't reduce.The function that current source I has in differential type LC oscillator except Dc bias is provided, and provide differential to ground high impedance value.In balancing circuitry, the signal of odd number harmonic wave (odd harmonic) flows along differential path (differentialpath), and the signal of even harmonic (even harmonic) flows along common-mode path (common-modepath).
Yet in the described circuit framework of Figure 1A, the mechanism that the resonant cavity quality factor reduces can be considered differential for common source (source) common-mode point dual numbers order harmonics for due to the low impedance value, therefore the current source I of Figure 1A only needs provide a high impedance to get final product to the even harmonic of frequency of oscillation, and in the even-order harmonic wave with second harmonic 2 ω
oBe principal component, so, the resonant cavity quality factor is reduced, to reach the purpose that reduces phase noise generally all only at second harmonic design high impedance circuit.
Then see also Fig. 3, refuse the circuit framework figure of the LC oscillator of resonant cavity noise filter for the tool band.As shown in Figure 3, for in differential type LC oscillator, realizing the common practice of noise filter at present, current source M in parallel one big capacitor C 1 is arrived ground, form the filtering path of the noise of current source M own, simultaneously add inductance L differential between to source electrode common-mode point CM and current source M, the parasitic capacitance C2 that itself and common-mode point CM place are had forms a frequency and is
Band refuse resonant cavity, the meaning promptly form at common-mode point CM right
High impedance value, and band is refused the resonance frequency accuracy of resonant cavity and the quality factor of inductance value influences its filtering usefulness.Under the application of extremely high frequency, inductance value may be less than 1nH, is difficult for realizing that with general helical structure (spiral) the sense value is little again accurately and the inductance of high quality factor.This kind design must accurately be grasped the characteristic and the parasitic capacitance at common-mode point place of inductance, otherwise the noise filtering characteristic have limited.
Summary of the invention
The objective of the invention is to overcome the deficiencies in the prior art and defective, proposition is applicable to the noise filter framework of differential type LC oscillator, it is different from existing mode of refusing resonant cavity with inductance, electric capacity anamorphic zone, comprises the noise filter framework that transmission line (Transmission line) is constituted for a kind of.The present invention utilizes the principle of transmission line impedance conversion, in differential the common-mode point place is produced the high resistance point of a frequency of oscillation second harmonic, reaches the function of noise filter.Its noise filtering usefulness is relevant with the transmission line length, can make things convenient for and calculates its due length exactly according to different frequency application, and mode that more can the multistage combination reaches the application purpose of multiband.
In order to reach above-mentioned purpose, the invention provides a kind of noise filter, connect a LC oscillator, this noise filter comprises: a transmission line connects this LC oscillator; One direct current bias circuit connects this transmission line, and a bias current is provided; And an electric capacity, an end of this electric capacity is connected between this transmission line and this direct-flow biasing circuit, and another of this electric capacity section ground connection provides this transmission line to exchange the path of ground connection; Wherein the length of this transmission line is 1/4 wavelength of the second harmonic of this LC oscillator, and this transmission line forms high impedance to the second harmonic of this LC oscillator thus.
In order to reach above-mentioned purpose, the present invention provides a kind of noise filter again, connects a LC oscillator, and this noise filter comprises: several sections transmission lines, those transmission lines are one another in series and connect this LC oscillator; One direct current bias circuit with those transmission line polyphones, provides a bias current, and wherein those transmission lines are arranged between this direct-flow biasing circuit and this inductive current oscillator; And several switches, an end correspondence of those switches is connected in those transmission lines, and the other end of those switches provides those transmission lines to exchange the path of ground connection individually by a capacity earth; Wherein pass through the switching of those switches, make this LC oscillator to 1/4 wavelength of the length that exchanges those transmission lines between earth point for two times of frequencies of oscillation of this LC oscillator, the second harmonic to the frequency of oscillation that this LC oscillator produced forms high impedance thus.
In order to reach above-mentioned purpose, the present invention provides a kind of noise filter again, connects a LC oscillator, and this noise filter comprises: several sections transmission lines, those transmission lines are one another in series and connect this LC oscillator; And several switches, an end of those switches is by a capacity earth, and another of those switches section corresponding those transmission lines that connect supply those transmission lines to exchange the path of ground connection; Wherein pass through the switching of those switches, make this LC oscillator to 1/4 wavelength of the length that exchanges those transmission lines between earth point for two times of frequencies of oscillation of this LC oscillator, the second harmonic to the frequency of oscillation that this LC oscillator produced forms high impedance thus.
In order to reach above-mentioned purpose, the present invention provides a kind of noise filtering method again, comprises the concussion frequency that at first obtains a LC oscillator; The transmission line of one segment length then is provided according to this frequency of oscillation, forms high impedance with the second harmonic to this frequency of oscillation, wherein the length of this section transmission line is 1/4 wavelength of twice frequency of oscillation.
Reach technology, means and the effect that predetermined purpose is taked in order further to understand the present invention, see also following about detailed description of the present invention and accompanying drawing, believe purpose of the present invention, feature and characteristics, go deep into and concrete understanding when getting one thus, yet appended graphic reference and the explanation usefulness of only providing not is to be used for the present invention is limited.
Description of drawings
Figure 1A is that differential type LC oscillator is not had a circuit framework figure of current source;
Figure 1B is output voltage and the load impedance oscillogram of Figure 1A;
Fig. 2 A is the circuit framework figure of differential type LC vibration utensil current source;
Fig. 2 B is output voltage and the load impedance oscillogram of Fig. 2 A;
Fig. 3 refuses the circuit framework figure of the LC oscillator of resonant cavity noise filter for the tool band;
Fig. 4 is a schematic diagram of transmission lines;
Fig. 5 is the pass figure of voltage on the transmission line of an end ground connection, electric current and impedance;
Fig. 6 A is the circuit diagram of the LC oscillator of tool single frequency band line noise filter of the present invention;
Fig. 6 B is the circuit diagram of the LC oscillator of another tool single frequency band line noise filter of the present invention;
Fig. 7 is the circuit diagram of the LC oscillator of tool multiband line noise filter of the present invention;
Fig. 8 A is the circuit diagram of the mutual LC oscillator of feedbacking of P-MOS of tool multiband line noise filter of the present invention;
Fig. 8 B is the circuit diagram of the mutual LC oscillator of feedbacking of P-MOS of another tool multiband line noise filter of the present invention;
Fig. 9 is the circuit diagram of LC oscillator of the complementary mutual back coupling of tool multiband line noise filter.
Symbol description among the figure
Q1, Q2, M1, M2, V1, V2 transistor
I, M, M3 current source
C1, C2, C3 ..., Cn electric capacity
L, L1, L2 inductance
SW1, SW2 ..., the SWn switch
TL, TL1, TL2 ..., the TLn transmission line
Vc, VDD, Vt power supply
CM, CM1, CM2 are differential to the source electrode common-mode point
61, the mutual LC oscillator of feedbacking of 71 N-MOS
62A, 62B single frequency band line noise filter
72,82A, 82B multiband line noise filter
721,821 filter circuits
63, the mutual LC oscillator of feedbacking of 81P-MOS
822 direct-flow biasing circuits
The LC oscillator of 91 complementary mutual back couplings
92 first multiband line noise filters
93 second multiband line noise filters
Embodiment
At first see also shown in Figure 4ly, be schematic diagram of transmission lines, be used to illustrate the transmission line circuit impedance operator, transmission line input impedance Z
InGenerally be expressed as:
Z
0Be line characteristic impedance, z
LBe terminal impedance, 1 is length of transmission line.When transmission line one end ground connection, that is terminal impedance Z
LBe 0 o'clock, input impedance is reduced to Z
In=jZ
0Tan β l.Transmission line input impedance Z when length of transmission line 1 is 1/4 wavelength (λ/4)
In=∞, the state of formation high input impedance.
Please consulting shown in Figure 5ly again, is the pass figure of voltage on the transmission line of an end ground connection, electric current and impedance, is zero at the voltage V of z=0 place, and electric current I is a maximum; When 1/4 wavelength odd-multiple position, voltage V is a maximum, and electric current I is zero, that is impedance Z will level off to infinity, is open-circuit condition.This principle is applied in the realization of noise filter, can
1/4 wavelength transmission line and the ground capacity form of reaching high impedance.
Then see also Fig. 6 A, circuit diagram for the LC oscillator of tool single frequency band line noise filter of the present invention, transistor M1 and M2 are mutual feedback differential right in the mutual LC oscillator 61 of feedbacking of N-MOS, capacitor C 1, C2, inductance L 1, L2 and transistor V1, V2 form the oscillator resonant cavity, decision frequency of oscillation ω
oSingle frequency band line noise filter 62A comprises transmission line TL, ground capacity C3 and current source M3, wherein current source M3 (direct-flow biasing circuit) provides oscillator 61 stable bias current, and ground capacity C3 has the filter function of current source M3 self-noise concurrently and provides transmission line TL to exchange the effect of ground connection.Place differentially to the transmission line TL between common-mode point CM and current source M3, its length is oscillator 61 second harmonics for this reason
1/4 wavelength.If ground capacity C3 is enough big, according to aforementioned transmission line principle, the ground capacity C3 of transmission line TL end is AC signal short circuit earth point (AC short toground), and being equivalent to above-mentioned terminal impedance is 0 place, process
The impedance transformation of 1/4 wavelength transmission line TL, make differentially to be to common-mode point CM place
AC signal open circuit point (ACopen), that is reach second harmonic in the purpose that a high impedance is arranged herein, and then make resonant cavity in cycle of oscillation, can not increase because of differential load effect to channel impedance makes the reduction of resonant cavity quality factor, oscillator phase.
From the above, please attached Fig. 6 B that consults, be the circuit diagram of the LC oscillator of another tool single frequency band line noise filter of the present invention, it is that the mutual LC oscillator of feedbacking 63 of a P-MOS connects single frequency band line noise filter 62B.With above-mentioned, single frequency band line noise filter 62B comprises transmission line TL, exchanges ground capacity C3 and current source M3, wherein current source M3 (direct-flow biasing circuit) provides oscillator 63 stable bias current, exchanges ground capacity C3 and has the filter function of current source M3 self-noise concurrently and provide transmission line TL to exchange the effect of ground connection.Place differentially to the transmission line TL between common-mode point CM and current source M3, its length is oscillator 63 second harmonics for this reason
1/4 wavelength.In like manner, process
The impedance transformation of 1/4 wavelength transmission line TL, make differentially to be to common-mode point CM place
AC signal open circuit point (AC open) can be in providing a high impedance to second harmonic herein.
See also Fig. 7, circuit diagram for the LC oscillator of tool multiband line noise filter of the present invention, transistor M1 and M2 are mutual feedback differential right in the mutual LC oscillator 71 of feedbacking of N-MOS, capacitor C 1, C2, inductance L 1, L2 and transistor V1, V2 form the oscillator resonant cavity, decision frequency of oscillation ω
oMultiband line noise filter 72 comprises current source M3 and filter circuit 721, current source M3 (direct-flow biasing circuit) provides oscillator 71 stable bias current, and 721 of filter circuits are by transmission line TL1, TL2..., TLn and capacitor C 1, C2 ..., Cn and switch SW 1, SW2 ..., SWn constitutes.Suppose oscillator 71 need to produce f1, f2..., fn (f1〉f2〉... ..〉fn) multiband frequency, the relation of its length of transmission line and frequency of oscillation is as follows:
Formula (1)
When frequency of oscillation during for high band f1, switch SW 1 is shut, other switch (SW2～SWn) open, transmission line TL1 is connected to ground capacity C1 via SW1, form interchange ground connection at the A1 point, under the situation that satisfies formula (1), transmission line TL1 is 1/4 wavelength of twice frequency of oscillation 2f1, therefore forms the noise filter of f1 frequency range.A1 is for exchanging ground connection, and the transmission line (TL2....., TLn) of level can't form transmission line TL1 and be connected in series and influence its characteristic after the institute.
When frequency of oscillation is time high band f2, switch SW 2 is shut, other switch (SW1, SW3～SWn) open, transmission line TL1 serial connection transmission line TL2 is connected to ground capacity C2 via switch SW 2, forms at the A2 point and exchanges ground connection, under the situation that satisfies formula (1), transmission line L1 serial connection transmission line TL2 total length is 1/4 wavelength of twice frequency of oscillation 2f2, therefore forms the noise filter of f2 frequency range.
When frequency of oscillation is peak low band fn, switch SW n shuts, other switch (SW1～SWn-1) open, transmission line TL1 is connected in series to transmission line TLn and is connected to ground capacity Cn via switch SW n, form interchange ground connection at the An point, under the situation that satisfies formula (1), it is 1/4 wavelength of twice frequency of oscillation 2fn that transmission line TL1 is connected in series to transmission line TLn total length, therefore forms the noise filter of fn frequency range.
Hold above-mentioned, capacitor C 1, C2 ..., Cn removes and to exchange earthyly as each section transmission line shut owing to all have a switch, so also be applicable to the usefulness of the noise filtering of current source M3 (direct-flow biasing circuit) itself simultaneously in arbitrary frequency range.For direct current, the operator scheme of arbitrary frequency range no matter, current path all is that TL1 is connected in series to TLn, so direct current can't be different because of the switching of different frequency range.For a different n frequency of oscillation, all can reach the noise filtering function of high frequency, multiband with this kind pattern via suitable design n section length of transmission line.
Yet, the present invention utilizes the circuit framework of the noise filtering that the transmission line form constituted to be not limited to as Fig. 6 and the mutual LC oscillator of feedbacking of the described N-MOS of Fig. 7, then see also Fig. 8 A, be the circuit diagram of the mutual LC oscillator of feedbacking of the P-MOS of tool multiband line noise filter of the present invention.The mutual LC oscillator of feedbacking 81 of P-MOS connects a multiband line noise filter 82A among the figure, wherein multiband line noise filter 82A comprises a filter circuit 821 and a direct current bias circuit 822, and multiband line noise filter 721 frameworks of filter circuit 821 similar Fig. 7, it comprises by transmission line TL1, TL2 ..., TLn and capacitor C 1, C2 ..., Cn and switch SW 1, SW2 ..., SWn forms, and direct-flow biasing circuit 822 can be a current mirroring circuit shown in Fig. 8 A.Because the relation of the power supply structure of the mutual LC oscillator 81 of feedbacking of P-MOS, thus partly correspondence is made associated change at direct-flow biasing circuit, but the operating principle of each transmission line, electric capacity and switch is with the action specification of Fig. 7.
And the present invention considers the power supply structure problem of the mutual LC oscillator 81 of feedbacking of P-MOS, another multiband line noise filter framework is provided again, shown in Fig. 8 B, it is the circuit diagram of the mutual LC oscillator of feedbacking of P-MOS of another tool multiband line noise filter of the present invention, the multiband line noise filter 82A of multiband line noise filter 82B and Fig. 8 A compares, bigger each transmission line TL1 that is not both, TL2 ... TLn is by switch SW 1, SW2 ... a capacitor C 1 is shared in the switching of SWn, and power vd D is connected in 1 of switch and capacitor C.Yet its operation principle is switched particular switch also with aforementioned according to the frequency that oscillator 81 produces, and realizes noise filtering to select suitable length of transmission line (1/4 wavelength of oscillator 81 twice frequencies of oscillation).
Then the present invention discloses a kind of multiband line noise filter framework that is applicable to the LC oscillator of complementary mutual back coupling again, sees also Fig. 9, is the circuit diagram of the LC oscillator of the complementary mutual back coupling of tool multiband line noise filter.The differential of the LC oscillator 91 of complementary mutual back coupling connects one first multiband line noise filter 92 to common-mode point CM1, and differential common-mode point CM2 connected one second multiband line noise filter 93.By finding among Fig. 9 that the first multiband line noise filter 92 is as the described multiband line noise of Fig. 8 A filter 82A (also can be the described multiband line noise of Fig. 8 B filter 82B), and the second multiband line noise filter 93 is a multiband line noise filter 72 as described in Figure 7, so its operating principle also as previously mentioned, so frequency f of being produced according to the LC oscillator 91 of complementary mutual back coupling of the first multiband line noise filter 92 and the second multiband line noise filter 93 as can be known, select suitable length of transmission line by the switching of switch, under the situation that satisfies aforementioned formula (1), the transmission line total length is 1/4 wavelength of twice frequency of oscillation 2f, in differential to common-mode point CM1, CM2 forms the high resistance point of twice frequency of oscillation 2f, thus with the noise of rejection frequency f.
Yet, transmission line in aforementioned each line noise filter can be any form and realizes, comprise strip line (strip line), microstrip line (microstrip line) or co-plane waveguide (coplanarwaveguide) etc., and direct-flow biasing circuit and switch also can be any form realization, comprise MOS, MESFET, BJT, resistance-type diode etc.
In sum as can be known, line noise filter of the present invention is applicable to the LC oscillator of various different shapes, and it utilizes 1/4 wavelength of design length of transmission line for oscillator twice frequency of oscillation, reaches the effect of noise filtering.
The above only is the present invention's preferred embodiment wherein, is not to be used for limiting practical range of the present invention; Be that all equalizations of doing according to claims of the present invention change and modification, be all claim of the present invention and contain.
Claims (17)
1. a noise filter is characterized in that, it connects a LC oscillator, and this noise filter comprises:
One transmission line connects this LC oscillator;
One direct current bias circuit connects this transmission line, and a bias current is provided; And
One electric capacity, an end of this electric capacity are connected between this transmission line and this direct-flow biasing circuit, and another section of this electric capacity exchanges ground connection, provides this transmission line to exchange the path of ground connection;
Wherein the length of this transmission line is the odd-multiple length of second harmonic 1/4 wavelength of this LC oscillator, and this transmission line forms high impedance to the second harmonic of this LC oscillator thus.
2. noise filter as claimed in claim 1 is characterized in that, this transmission line is strip line, microstrip line or co-plane waveguide.
3. noise filter as claimed in claim 1 is characterized in that, this direct-flow biasing circuit is realized with MOS, MESFET, BJT or resistance-type diode.
4. noise filter as claimed in claim 1 is characterized in that, this LC oscillator is the mutual LC oscillator of feedbacking of N-MOS, the mutual LC oscillator of feedbacking of P-MOS or the LC oscillator of complementary mutual back coupling.
5. a noise filter is characterized in that, it connects a LC oscillator, and this noise filter comprises:
One direct current bias circuit is used to provide a bias current;
Several sections transmission lines, those transmission lines are one another in series, and are arranged between this direct-flow biasing circuit and this inductive current oscillator; And
Several switches, an end correspondence of those switches is connected in those transmission lines, and the other end of those switches exchanges ground connection by an electric capacity individually, provides those transmission lines to exchange the path of ground connection;
Wherein pass through the switching of those switches, make this LC oscillator to 1/4 wavelength of the length that exchanges those transmission lines between earth point for two times of frequencies of oscillation of this LC oscillator, the second harmonic to the frequency of oscillation that this LC oscillator produced forms high impedance thus.
6. noise filter as claimed in claim 5 is characterized in that, those transmission lines are strip line, microstrip line or co-plane waveguide.
7. noise filter as claimed in claim 5 is characterized in that, this direct-flow biasing circuit and those switches are realized with MOS, MESFET, BJT or resistance-type diode respectively.
8. noise filter as claimed in claim 5 is characterized in that, this LC oscillator is the mutual LC oscillator of feedbacking of N-MOS, the mutual LC oscillator of feedbacking of P-MOS or the LC oscillator of complementary mutual back coupling.
9. noise filter as claimed in claim 5 is characterized in that, this LC oscillator is the mutual LC oscillator of feedbacking of P-MOS, and this direct-flow biasing circuit is a current mirroring circuit.
10. a noise filter is characterized in that, it connects a LC oscillator, and this noise filter comprises:
Several sections transmission lines, those transmission lines are one another in series and connect this LC oscillator; And
Several switches, an end of those switches exchanges ground connection by an electric capacity, and another of those switches section corresponding those transmission lines that connect supply those transmission lines to exchange the path of ground connection;
Wherein pass through the switching of those switches, make this LC oscillator to 1/4 wavelength of the length that exchanges those transmission lines between earth point for two times of frequencies of oscillation of this LC oscillator, thus to frequency of oscillation that this LC oscillator produces second harmonic formation high impedance.
11. noise filter as claimed in claim 10 is characterized in that, those transmission lines are strip line, microstrip line or co-plane waveguide.
12. noise filter as claimed in claim 10 is characterized in that, those switches are realized with MOS, MESFET, BJT or resistance-type diode.
13. noise filter as claimed in claim 10 is characterized in that, this LC oscillator is the mutual LC oscillator of feedbacking of P-MOS or the LC oscillator of complementary mutual back coupling.
14. noise filter as claimed in claim 10 is characterized in that, is provided with a voltage source between those switches and this electric capacity.
15. a noise filtering method is characterized in that, comprising:
Obtain the concussion frequency of a LC oscillator; And
Provide the transmission line of a segment length according to this frequency of oscillation, form high impedance with the second harmonic to this frequency of oscillation, wherein the length of this section transmission line is 1/4 wavelength of this frequency of oscillation of twice.
16. noise filtering method as claimed in claim 15 is characterized in that, the length of this section transmission line is utilized and is switched several switches, adjusts so that an interchange earth point to be provided by the indivedual pairing electric capacity of those switches.
17. noise filtering method as claimed in claim 15 is characterized in that, this LC oscillator is the mutual LC oscillator of feedbacking of P-MOS, the mutual LC oscillator of feedbacking of N-MOS or the LC oscillator of complementary mutual back coupling.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2007101399803A CN101364787A (en) | 2007-08-07 | 2007-08-07 | Noise filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2007101399803A CN101364787A (en) | 2007-08-07 | 2007-08-07 | Noise filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN101364787A true CN101364787A (en) | 2009-02-11 |
Family
ID=40390991
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA2007101399803A Pending CN101364787A (en) | 2007-08-07 | 2007-08-07 | Noise filter |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102035571A (en) * | 2009-10-03 | 2011-04-27 | 瑞昱半导体股份有限公司 | Signal transceiving circuit and noise reduction circuit |
| CN104485922A (en) * | 2014-12-17 | 2015-04-01 | 上海斐讯数据通信技术有限公司 | Circuit and method for decreasing circuit power consumption |
| CN111211767A (en) * | 2018-11-21 | 2020-05-29 | 英业达科技有限公司 | Noise suppression circuit device |
| CN112303806A (en) * | 2020-10-19 | 2021-02-02 | 青岛海信日立空调系统有限公司 | Communication circuit and air conditioner |
-
2007
- 2007-08-07 CN CNA2007101399803A patent/CN101364787A/en active Pending
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102035571A (en) * | 2009-10-03 | 2011-04-27 | 瑞昱半导体股份有限公司 | Signal transceiving circuit and noise reduction circuit |
| CN102035571B (en) * | 2009-10-03 | 2014-01-08 | 瑞昱半导体股份有限公司 | Signal transceiving circuit and noise reduction circuit |
| CN104485922A (en) * | 2014-12-17 | 2015-04-01 | 上海斐讯数据通信技术有限公司 | Circuit and method for decreasing circuit power consumption |
| CN104485922B (en) * | 2014-12-17 | 2018-10-12 | 上海斐讯数据通信技术有限公司 | The method for reducing the circuit of circuit power consumption and reducing circuit power consumption |
| CN111211767A (en) * | 2018-11-21 | 2020-05-29 | 英业达科技有限公司 | Noise suppression circuit device |
| CN111211767B (en) * | 2018-11-21 | 2023-10-03 | 英业达科技有限公司 | Noise suppression circuit device |
| CN112303806A (en) * | 2020-10-19 | 2021-02-02 | 青岛海信日立空调系统有限公司 | Communication circuit and air conditioner |
| CN112303806B (en) * | 2020-10-19 | 2023-11-17 | 青岛海信日立空调系统有限公司 | Communication circuit and air conditioner |
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