CN103178795B - A kind of difference frequency device based on logafier - Google Patents

Abstract

The invention discloses a kind of difference frequency device based on logafier, comprise: the first resistance and the second resistance, the input first signal source, one end of the first resistance, the other end of the first resistance connects respectively the anode of the first diode and the negative electrode of the second diode, the negative electrode of described the first diode and described the second diode anode connect the output of operational amplifier simultaneously, output difference frequency signal voltage; The first diodes in parallel electric capacity; The input secondary signal source, one end of the second resistance, the other end of the second resistance connects respectively anode, the negative electrode of the second diode and the negative polarity input of operational amplifier of the first diode; The positive polarity input end grounding of operational amplifier. This difference frequency device processing ease, simple in structure, can get easily the difference frequency signal stable, precision is high, easily integrated, and reduced circuit cost, meet the multiple needs in practical application.

Description

A kind of difference frequency device based on logafier

Technical field

The present invention relates to electronic technology field, particularly a kind of difference frequency device based on logafier.

Background technology

Difference frequency device is nonlinear device, and output signal frequency equals the poor of two frequency input signals. Of the prior art poorFrequently device is generally diode difference frequency device, balance difference frequency device and transistor difference frequency device etc., is all made up of inductance and transformer etc.

Inventor is realizing in process of the present invention, finds at least to exist in prior art following shortcoming and defect:

1) between each loop of above-mentioned difference frequency device, influence each other more serious, combination frequency disturb also larger, cause gettingDifference frequency signal unstable;

2) discreteness that is subject to component parameter of above-mentioned difference frequency device affects greatly, and dynamic range that can processing signals is little;

3) difference frequency signal getting is deamplification, and sensitivity is low, is difficult to meet the multiple needs in practical application.

Summary of the invention

The invention provides a kind of difference frequency device based on logafier, this difference frequency device has been avoided the interference of combination frequency,Get the difference frequency signal that stability is higher, described below:

A difference frequency device based on logafier, comprising: the first resistance and the second resistance,

The input first signal source, one end of described the first resistance, the other end of the first resistance connects respectively the sun of the first diodeThe negative electrode of the utmost point and the second diode, the negative electrode of described the first diode and described the second diode anode connect operational amplifier simultaneouslyOutput, output difference frequency signal voltage; Described the first diodes in parallel electric capacity;

The input secondary signal source, one end of described the second resistance, the other end of described the second resistance connects respectively the described the 1The negative polarity input of the anode of utmost point pipe, the negative electrode of described the second diode and described operational amplifier; Described operational amplifierPositive polarity input end grounding.

The beneficial effect of technical scheme provided by the invention is: by antiparallel diode, operational amplifier and resistanceFormed the difference frequency device based on logafier, this difference frequency device processing ease, simple in structure, can get easily stable,The difference frequency signal that precision is high, easily integrated, and reduced circuit cost, expand the dynamic range of signal; By revisingThe resistance of one resistance and the second resistance can be easy to change the gain of difference frequency device, by can to the selection of operational amplifier modelDifference frequency signal is amplified to processing, the multiple needs in practical application are met.

Brief description of the drawings

Fig. 1 is the circuit theory diagrams of a kind of difference frequency device based on logafier provided by the invention.

In accompanying drawing, the list of parts of each label representative is as follows:

R₁: the first resistance; R₂: the second resistance;

A: operational amplifier; D₁: the first diode;

D₂: the second diode; V_o: difference frequency signal voltage;

V₁: first signal source; V₂: secondary signal source;

C: electric capacity.

Detailed description of the invention

For making the object, technical solutions and advantages of the present invention clearer, hereby exemplify following examples, and coordinate accompanying drawing detailedCarefully be described as follows:

For fear of the interference of combination frequency, get the difference frequency signal that stability is higher, the embodiment of the present invention has proposedA difference frequency device based on logafier, referring to Fig. 1, comprising: the first resistance R₁With the second resistance R₂，

The first resistance R₁One end input first signal source V₁, the first resistance R₁The other end meet respectively the first diode D₁Anode and the second diode D₂Negative electrode, the first diode D₁Negative electrode and the second diode D₂Anode connects operation amplifier simultaneouslyThe output of device A, output difference frequency signal voltage V_o; The first diode D₁Shunt capacitance C;

The second resistance R₂One end input secondary signal source V₂, the second resistance R₂The other end meet respectively the first diode D₁Anode, the second diode D₂Negative electrode and the negative polarity input of operational amplifier A; The positive polarity input of operational amplifier AEnd ground connection.

, the first diode D₁With the second diode D₂Between form inverse parallel circuit.

Describe the operation principle of this difference frequency device in detail below in conjunction with Fig. 1, described below:

Because the C-V characteristic of diode is

$I_D=I_S(e^{\frac{V_D}{V_S}}-1)---\left(1\right)$

Wherein: I_SFor the reverse saturation current of PN junction; V_SFor temperature voltage equivalent, be 27 ° of 300K(Celsius temperatures in temperatureC) time, be about 26mV; V_DFor conducting voltage.

Work as V_D>>V_STime,Therefore (1) formula can be rewritten as

$I_D=I_S{e}^{\frac{V_D}{V_S}}---\left(2\right)$

Put aside the effect of capacitor C, due to

$I_I=\frac{V_1}{R_1}+\frac{V_2}{R_2}=I_D---\left(3\right)$

? $\frac{V_1}{R_1}+\frac{V_2}{R_2}=I_S{e}^{\frac{V_D}{V_S}}---\left(4\right)$

Due to D1 and D2 reverse parallel connection, only consider the absolute value of circuit output,

$V_O=V_D=V_S\ln \frac{1}{I_S}(\frac{V_1}{R_1}+\frac{V_2}{R_2})---\left(5\right)$

Get R₁＝R₂=R, has

$V_O=V_S\ln \frac{1}{I_{S}R}+V_S\ln (V_1+V_2)---\left(6\right)$

From (6) formula, circuit is logafier. Logarithm lnx can expand into progression:

$\ln x={\ln x}_0+\frac{1}{x_0}\frac{(x-x_0)}{1!}-\frac{1}{x_0^2}\frac{{(x-x_0)}^2}{2!}+\·\·\·{\left(\ln x_0\right)}^{\left(n\right)}\frac{{(x-x_0)}^n}{n!}+\·\·\·---\left(7\right)$

By (6) and (7) formula, and only consider its quadratic term, and all quadratic term coefficients be designated as to K:

V’_O=K（V₁+V₂）²（8）

At V₁=V_1msinω₁T and V₂=V_2msinω₂When t, (8) formula can be rewritten into:

V’_O=K（V_1msinω₁t+V_2msinω₂t）²（9）

(9) formula is launched, and is only considered its cross term:

V”_O=2KV_lmsinω₁t·V_2msinω₂t（10）

Utilize product to sum formula (10) formula can be rewritten as

V”_O=2KV_1mV_2m（sin（ω₁+ω₂）t+sin（ω₁-ω₂）t）（11）

Work as ω₁And ω₂For close high-frequency signal, be also (ω₁-ω₂）<<（ω₁+ω₂), by reasonably arranging firstThe numerical value of resistance R 1, the second resistance R 2 and capacitor C, can filtering and frequency (ω₁+ω₂) signal and retain difference frequency (ω₁-ω₂) letterNumber, have:

V″′_O=2KV_1mV_2msin（ω₁-ω₂）t）（12）

Can get difference frequency signal by (11) formula, this low frequency signal can be used in ultrasonic device or radio,The multiple needs in practical application are met. As can be seen here, this difference frequency device has been realized difference frequency function.

When practical application, can be by amendment the first resistance R₁With the second resistance R₂Resistance change whole difference frequency deviceGain, by can amplify processing to difference frequency signal to the selection of operational amplifier A model, has met in practical applicationMultiple needs.

Wherein, the difference frequency device that the embodiment of the present invention provides is with R₁＝R₂=10k Ω, the first diode D₁With the second diodeD₂Model be 1N4148, capacitor C=0.01 μ F, the model of operational amplifier A is that OP07 is that example describes. When specific implementation,The embodiment of the present invention does not limit the model of above-mentioned components and parts, all can as long as can complete the components and parts of above-mentioned functions.

Can find out by above-mentioned example the difference frequency device processing ease that the embodiment of the present invention provides, simple in structure, Ke YifangJust get difference frequency signal, met the multiple needs in practical application, and owing to only adopting diode, resistance and computing to putThe components and parts such as large device, have avoided the interference of the combination frequency between components and parts, and the precision of the difference frequency signal therefore getting is higher,There is stability in essence.

It will be appreciated by those skilled in the art that accompanying drawing is the schematic diagram of a preferred embodiment, the invention described above embodimentSequence number, just to describing, does not represent the quality of embodiment.

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all in spirit of the present invention andWithin principle, any amendment of doing, be equal to replacement, improvement etc., within protection scope of the present invention all should be included in.

Claims (1)

1. the difference frequency device based on logafier, comprising: the first resistance (R₁) and the second resistance (R₂), it is characterized in that,

Described the first resistance (R₁) one end input first signal source (V₁), the first resistance (R₁) the other end connect respectively the one or twoUtmost point pipe (D₁) anode and the second diode (D₂) negative electrode, described the first diode (D₁) negative electrode and described the second diode(D₂) anode connects the output of operational amplifier (A) simultaneously, output difference frequency signal voltage (V_o); Described the first diode (D₁) alsoConnection electric capacity (C);

Described the second resistance (R₂) one end input secondary signal source (V₂), described the second resistance (R₂) the other end meet respectively instituteState the first diode (D₁) anode, described the second diode (D₂) negative electrode and the negative polarity input of described operational amplifier (A)End; The positive polarity input end grounding of described operational amplifier (A);

The first diode (D₁) and the second diode (D₂) between form inverse parallel circuit;

Difference frequency signal voltage (V_o) utilize product to sum formula, and filtering and frequency ω₁+ω₂Signal and retain difference frequency ω₁-ω₂LetterNumber, be finally rewritten as V_o’’’＝2KV_1mV_2msin(ω₁-ω₂)t)；

Wherein, ω₁And ω₂For frequency; V_1m、V_2mFor amplitude; K is all coefficients of quadratic term; T is the time; Quadratic term is (V₁+V₂)²。