CN203243290U - Tracking filter circuit - Google Patents

Abstract

The utility model discloses a tracking filter circuit comprising three operational amplifiers. The non-inverting input ends of the three operational amplifiers are connected with the earth at the same time. A capacitor is connected in parallel between the inverting input ends and the output ends of the first and the second operational amplifiers. A sixth resistor is connected in parallel between the inverting input end and the output end of the third operational amplifier. A second analog electronic switch and a second resistor are connected in series between the output end of the first operational amplifier and the inverting input end of the second operational amplifier. A fifth resistor is connected in series between the output end of the second operational amplifier and the inverting input end of the third operational amplifier. The inverting input end of the first operational amplifier is connected with a first analog electronic switch, a third analog electronic switch and a fourth resistor, and the third analog electronic switch and the fourth resistor are connected in series with each other. The other end of the first analog electronic switch is connected with a first resistor and a third resistor. The other end of the first resistor is connected with the output end of the first operational amplifier. The other end of the third resistor is connected with the output end of the third operational amplifier.

Description

A kind of tracking filter circuit

Technical field

The utility model relates to a kind of tracking filter circuit.

Background technology

The tracking filter circuit is used very extensive in practice, in many telemetry circuits, and the centre frequency f of measured signal ₀In very wide frequency band, change, require the tracking filter circuit at very narrow f ₀± Δ f _TExtract measuring-signal in the frequency band.In this case, adopt common tracking filter circuit can't obtain required measuring-signal, and utilize the automatic adjustable tracking filter circuit of centre frequency effectively to address this problem.

The method of realization tracking filter circuit has multiple, such as voltage-controlled tracking filter circuit, frequency conversion tracking filter circuit etc.In voltage-controlled tracking filter circuit, voltage-controlled voltage and centre frequency f ₀Between linear relationship generally undesirable, generally need to the centre frequency of tracking filter circuit be locked in signal center frequency by closed-loop system, thereby realize tracking filter; Frequency conversion tracking filter circuit structure is complicated, often will realize by crystal filter the inhibition of noise.

In practice, can pass through electronic devices and components designed, designed tracking filter circuit, also can directly in market, buy the integrated chip with tracking filter function and realize corresponding tracking filter function., mode of operation higher owing to the integrated chip price with tracking filter function is fixing etc., has limited the application of integrated chip.

The utility model content

The purpose of this utility model is in order to overcome the deficiencies in the prior art, a kind of tracking filter circuit to be provided, and it is simple in structure, and cost is low, has the logical tracking filter function of band, and the multiplication factor A at the logical centre frequency place of band and quality factor Q be not with input signal U _i(s) angular frequency changes, and is fixed value.

A kind of technical scheme that realizes above-mentioned purpose is: a kind of tracking filter circuit comprises the first operational amplifier, the second operational amplifier and the 3rd operational amplifier;

Described the first operational amplifier, its in-phase input end ground connection is parallel with the first electric capacity between its inverting input and its output;

Described the second operational amplifier, its in-phase input end ground connection is parallel with the second electric capacity between its inverting input and its output;

Described the 3rd operational amplifier, its in-phase input end ground connection is parallel with the 6th resistance between its inverting input and its output, is connected by the 5th resistance between the output of its inverting input and described the second operational amplifier; It is characterized in that:

This tracking filter circuit also comprises: the first resistance, the second resistance, the 3rd resistance and the 4th resistance, the first simulant electronic switch, the second simulant electronic switch and the 3rd simulant electronic switch;

One end of described the first simulant electronic switch connects the inverting input of described the first operational amplifier, an other end connects described the first resistance and described the 3rd resistance simultaneously, the other end of described the first resistance connects the output of described the first operational amplifier, and the other end of described the 3rd resistance connects the output of described the 3rd operational amplifier;

Described the 4th resistance and described the 3rd simulant electronic switch are connected in series with each other the inverting input at described the first operational amplifier, make the inverting input of described the first operational amplifier receive external input signal;

Described the second resistance and described the second simulant electronic switch are connected in series with each other between the inverting input of the output of described the first operational amplifier and described the second operational amplifier;

Described the first simulant electronic switch, described the second simulant electronic switch and described the 3rd simulant electronic switch receive the pulse-width signal of same control end output simultaneously.

Further, described the 3rd simulant electronic switch is connected to the inverting input of described the first operational amplifier.

Further, described the 4th resistance is connected to the inverting input of described the first operational amplifier.

Further, described the second resistance is connected to the output of described the first operational amplifier, and described the second simulant electronic switch is connected to the inverting input of described the second operational amplifier.

Further, described the second simulant electronic switch is connected to the output of described the first operational amplifier, and described the second resistance is connected to the inverting input of described the second operational amplifier.

Further, the resistance value of described the 5th resistance and described the 6th resistance equates.

Further, the capacitance of described the first electric capacity and described the second electric capacity equates.

Adopted the technical scheme of a kind of tracking filter circuit of the present utility model, that is, the 3rd simulant electronic switch and the 4th resistance are connected in series the inverting input of the first operational amplifier, make the inverting input of the first operational amplifier receive external input signal; The first simulant electronic switch is connected to the inverting input of the first operational amplifier, and be connected with the 3rd resistance with first, realize inverting input and the output of the first operational amplifier, being communicated with between the inverting input of the first operational amplifier and the 3rd operational amplifier output terminal, the first simulant electronic switch and the 3rd simulant electronic switch receive the technical scheme of the pulse-width signal of same control end output simultaneously.Its technique effect is: a kind of tracking filter circuit of the present utility model has the logical tracking filter function of band, only needs operational amplifier, resistance and electric capacity to get final product the completing circuit design; The span of the level of the input signal of a kind of tracking filter circuit of the present utility model only is decided by the operating voltage of operational amplifier, and the utility model is simple in structure, design is convenient.

Description of drawings

Fig. 1 is the structural representation of the first embodiment of a kind of tracking filter circuit of the present utility model.

Fig. 2 is the structural representation of the second embodiment of a kind of tracking filter circuit of the present utility model.

Embodiment

See also Fig. 1 and Fig. 2, inventor of the present utility model be in order to understand the technical solution of the utility model better, below by embodiment particularly, and is described in detail by reference to the accompanying drawings:

The first embodiment

See also Fig. 1, a kind of tracking filter circuit comprises the first operational amplifier M1, the second operational amplifier M2 and the 3rd operational amplifier M3; The first simulant electronic switch S1, the second simulant electronic switch S2 and the 3rd simulant electronic switch S3; The first resistance R ₁, the second resistance R ₂, the 3rd resistance R ₃, the 4th resistance R ₄, the 5th resistance R ₅With the 6th resistance R ₆, the first capacitor C ₁With the second capacitor C ₂

The in-phase input end of the first operational amplifier M1, the second operational amplifier M2 and the 3rd operational amplifier M3 is ground connection simultaneously.

The first capacitor C ₁Be connected in parallel between the inverting input and output of the first operational amplifier M1.

The second capacitor C ₂Be connected in parallel between the inverting input and output of the second operational amplifier M2.

The 6th resistance R ₆Be connected in parallel between the inverting input and output of the 3rd operational amplifier M3.

Pass through the 5th resistance R between the inverting input of the output of the second operational amplifier M2 and the 3rd operational amplifier M3 ₅Connect.

The end of the first simulant electronic switch S1 connects the inverting input of the first operational amplifier M1, the other end and the first resistance R ₁, the 3rd resistance R ₃Connect simultaneously, wherein the first resistance R ₁The other end connect the output of the first operational amplifier M1, the 3rd resistance R ₃The other end connect the output of the 3rd operational amplifier M3.

The second resistance R ₂An end connect the output of the first operational amplifier M1, the other end is connected with the second simulant electronic switch S2, the second simulant electronic switch S2 is connected with the inverting input of the second operational amplifier M2.

The end of the 3rd simulant electronic switch S3 connects the inverting input of the first operational amplifier M1, and the other end connects the 4th resistance R ₄When the 3rd simulant electronic switch S3 was closed, the inverting input of the first operational amplifier M1 was by the 4th resistance R ₄Receive external input signal U _i(s), and to input signal U _i(s) carry out integration, from output signal U of output output of the first operational amplifier M1 ₀(s).

The first simulant electronic switch S1, the second simulant electronic switch S2 and the external same control end of the 3rd simulant electronic switch S3, pulse-width signal C of this control end output.The cycle of this pulse-width signal C is T, and in the cycle T of each described pulse-width signal, the time that first to the 3rd simulant electronic switch S1～S3 is in closure state is T _T

The second embodiment

See also Fig. 2, the second embodiment has made two places than embodiment 1 and has changed.

The first place changes and to be: the end of the second simulant electronic switch S2 connects the output of the first operational amplifier M1, the other end be connected the second resistance R ₂, the second resistance R ₂Be connected with the inverting input of the second operational amplifier M2.

The change of the second place is: the 4th resistance R ₄An end connect the inverting input of the first operational amplifier M1, the other end connects the 3rd simulant electronic switch S3.

The operation principle that regards to down a kind of tracking filter circuit of the present utility model is specifically described:

The utility model is by the pulse-width signal C in the control end input, and the break-make of control first to the 3rd simulant electronic switch S1～S3 changes first to fourth resistance R ₁～R ₄Equivalent mean value R _1e～R _4eThereby, the input-output characteristic of change tracking filter circuit.As shown in Figure 1, the pulse-width signal C that the described control end input cycle is T, in the cycle T of a pulse-width signal C, the first to the 3rd simulant electronic switch S1～S3 is closed, and namely pulse-width signal C is that the time of high level is T _T, T _TBe called again the conducting width, be fixed value, then the first resistance R in one-period T ₁Equivalent mean value R _1eFor:

$R_{1e}=\frac{T}{T_T}{R}_1---\left(1\right)$

In the T that makes a pulse-width signal C, the first resistance R ₁Equivalent mean value R _1eBe constant, the frequency of desirable pulse-width signal C is input signal U _iThe n of frequency f (s) doubly generally gets n 〉=100.Then have:

$R_{1e}=\frac{T}{{\mathrm{<figure-callout\; id="1"\; label="T\; T\; R"\; filenames="HDA00003060444600011.png,HDA00003060444600012.png"\; state="\{\{state\}\}">T</figure-callout>}}_T}{R}_{}{}_1=\frac{n/T_T}{n/\mathrm{<figure-callout\; id="1"\; label="T\; R"\; filenames="HDA00003060444600011.png,HDA00003060444600012.png"\; state="\{\{state\}\}">T</figure-callout>}}{R}_{}{}_1=\frac{f_{\mathrm{<figure-callout\; id="1"\; label="T\; f\; R"\; filenames="HDA00003060444600011.png,HDA00003060444600012.png"\; state="\{\{state\}\}">T</figure-callout>}}}{f}{R}_{}{}_1=\frac{{\mathrm{\&omega;}}_T}{\mathrm{\&omega;}}{R}_1---\left(2\right)$

In the formula, ω is input signal U _i(s) angular frequency, ω _TBe full angle of flow frequency.f _TBe full turn-on frequency.Full turn-on frequency f _TWith full angle of flow frequencies omega _TIt all is definite value.The frequency f of full conducting _TWith full angle of flow frequencies omega _T, determined the workable frequency range of a kind of tracking filter circuit of the present utility model.

At this moment, the cycle of pulse-width signal C ON time wherein, namely the conducting width is $T_T=\frac{1}{n{f}_T}.$

When the cycle T of pulse-width signal C equals conducting width T _TThe time, R _1eBe R ₁

Similarly, the second to the 4th resistance R ₂～R ₄Equivalent mean value R _2e～R _4eBe followed successively by:

$R_{2e}=\frac{{\mathrm{\&omega;}}_T}{\mathrm{\&omega;}}{R}_2,R_{3e}=\frac{{\mathrm{\&omega;}}_T}{\mathrm{\&omega;}}{R}_3,R_{4e}=\frac{{\mathrm{\&omega;}}_T}{\mathrm{\&omega;}}{R}_4---\left(3\right)$

The input-output characteristic of a kind of tracking filter circuit of the present utility model is:

$H\left(s\right)=\frac{U_i\left(s\right)}{U_0\left(s\right)}=-\frac{\frac{1}{R_{4e}{C}_1}s}{s^2+\frac{1}{R_{1e}{C}_1}s+\frac{1}{R_{2e}{R}_{3e}{C}_1{C}_2}}=-\frac{D{\mathrm{\&omega;}}_{0}s}{s^2+\frac{{\mathrm{\&omega;}}_0}{Q}s+{\mathrm{\&omega;}}_0^2}---\left(4\right)$

Wherein output characteristic H (s), input signal U _i(s) and output signal U ₀(s) all be that D is called proportionality coefficient about the periodic function of time s.

By formula (4) as can be known, a kind of tracking filter circuit of the present utility model has bandpass characteristics, its center angular frequency ₀For:

${\mathrm{\&omega;}}_0=\sqrt{\frac{1}{R_{2e}{R}_{3e}{C}_1{C}_2}}=\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_T}\sqrt{\frac{1}{R_2{R}_3{C}_1{C}_2}}---\left(5\right)$

Q is quality factor in the formula (4), that is:

$Q=\sqrt{\frac{R_{1e}^2{C}_1}{R_{2e}{R}_{3e}{C}_2}}=\sqrt{\frac{R_1^2{C}_1}{R_2{R}_3{C}_2}}---\left(6\right)$

Suppose C ₁=C ₂, the central angle frequencies omega ₀The multiplication factor A at place:

$A=\mathrm{DQ}=\sqrt{\frac{R_{2e}{R}_{3e}{C}_2}{R_{4e}^2{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA00003060444600011.png,HDA00003060444600012.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}}\&times;\sqrt{\frac{R_{1e}^2{C}_1}{R_{2e}{R}_{3e}{C}_2}}=\frac{R_1}{R_4}---\left(7\right)$

If get full angle of flow frequency

The central angle frequencies omega is then arranged ₀, quality factor q, central angle frequencies omega ₀The multiplication factor A at place is respectively:

${\mathrm{\&omega;}}_0=\mathrm{\&omega;},Q=\sqrt{\frac{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HDA00003060444600011.png,HDA00003060444600012.png"\; state="\{\{state\}\}">R</figure-callout>}}_1^2{C}_1}{R_2{R}_3{C}_2}},A=\frac{R_1}{R_4}---\left(8\right)$

Therefore, a kind of tracking filter circuit of the present utility model is in the central angle frequencies omega ₀The multiplication factor A at place and quality factor Q be not with input signal U _i(s) angular frequency changes, and is fixed value, and therefore a kind of tracking filter circuit of the present utility model has the function of the logical tracking filter of band.

Design example:

If require a kind of tracking filter circuit of the present utility model below 1kHz, to work, and require in the central angle frequencies omega ₀, with input signal U _i(s) frequency f changes, and quality factor q is 10, the central angle frequencies omega ₀The multiplication factor A at place is 1.

Get f _T=1kHz, n=100, then

ω _T=2 π f _T=6.28 * 10 ³Rad/s, the conducting width T of pulse-width signal C _TBe 10 μ s, be fixed value.

Selected first to the 3rd operational amplifier M1～M3 is AD711 type operational amplifier, gets C ₁=C ₂=0.01 μ F, by

Desirable R ₂=R ₃=15.92k Ω gets 1% precision resistance nominal value 15.8k Ω.By Q=10, R ₁=159.2k Ω gets 1% precision resistance nominal value 158k Ω.By A=1, get R ₄Be 1% precision resistance nominal value 158k Ω.In addition, get R ₅And R ₆Be 10k Ω.

The cycle of pulse-width signal C

If will carry out filtering to the sine wave of 50Hz, then the cycle of pulse-width signal C is 200 μ s.

A kind of tracking filter circuit engineering effect of the present utility model is: have the logical following function of band, and only need common operational amplifier, resistance and electric capacity to design by completing circuit; Its input signal U _iThe span of level (s) only is decided by the operating voltage of operational amplifier, such as the operating voltage of operational amplifier is ± 15V, then input signal U _i(s) span approaches ± 15V.The utility model is simple in structure, design is convenient.

Those of ordinary skill in the art will be appreciated that, above embodiment illustrates the utility model, and be not to be used as restriction of the present utility model, as long as in connotation scope of the present utility model, all will drop in claims scope of the present utility model variation, the modification of the above embodiment.

Claims (7)

1. a tracking filter circuit comprises the first operational amplifier, the second operational amplifier and the 3rd operational amplifier;

Described the first operational amplifier, its in-phase input end ground connection is parallel with the first electric capacity between its inverting input and its output;

Described the second operational amplifier, its in-phase input end ground connection is parallel with the second electric capacity between its inverting input and its output;

Described the 3rd operational amplifier, its in-phase input end ground connection is parallel with the 6th resistance between its inverting input and its output, is connected by the 5th resistance between the output of its inverting input and described the second operational amplifier; It is characterized in that:

This tracking filter circuit also comprises: the first resistance, the second resistance, the 3rd resistance and the 4th resistance, the first simulant electronic switch, the second simulant electronic switch and the 3rd simulant electronic switch;

One end of described the first simulant electronic switch connects the inverting input of described the first operational amplifier, an other end connects described the first resistance and described the 3rd resistance simultaneously, the other end of described the first resistance connects the output of described the first operational amplifier, and the other end of described the 3rd resistance connects the output of described the 3rd operational amplifier;

Described the 4th resistance and described the 3rd simulant electronic switch are connected in series with each other the inverting input at described the first operational amplifier, make the inverting input of described the first operational amplifier receive external input signal;

Described the second resistance and described the second simulant electronic switch are connected in series with each other between the inverting input of the output of described the first operational amplifier and described the second operational amplifier;

Described the first simulant electronic switch, described the second simulant electronic switch and described the 3rd simulant electronic switch receive the pulse-width signal of same control end output simultaneously.

2. a kind of tracking filter circuit according to claim 1, it is characterized in that: described the 3rd simulant electronic switch is connected to the inverting input of described the first operational amplifier.

3. a kind of tracking filter circuit according to claim 1, it is characterized in that: described the 4th resistance is connected to the inverting input of described the first operational amplifier.

4. a kind of tracking filter circuit according to claim 1, it is characterized in that: described the second resistance is connected to the output of described the first operational amplifier, and described the second simulant electronic switch is connected to the inverting input of described the second operational amplifier.

5. a kind of tracking filter circuit according to claim 1, it is characterized in that: described the second simulant electronic switch is connected to the output of described the first operational amplifier, and described the second resistance is connected to the inverting input of described the second operational amplifier.

6. the described a kind of tracking filter circuit of any one in 5 according to claim 1, it is characterized in that: the resistance value of described the 5th resistance and described the 6th resistance equates.

7. the described a kind of tracking filter circuit of any one in 5 according to claim 1, it is characterized in that: the capacitance of described the first electric capacity and described the second electric capacity equates.

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