JP2001284978A - Distortion corrector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct higher harmonic distortions. SOLUTION: Concerning the distortion corrector using a directional branch transformer composed of a transformer and a matched resistor, a non-linear resistor means R2 is connected to a terminating resistor terminal T of a directional branch transformer 20 and a control resistor R1 is connected to a branch terminal BR. At such a time, one part of input signal is impressed to the non- linear resistor means. Thus, second or third harmonic distortion is generated and outputted from an output terminal OUT. Corresponding to the phase relation of distortion occurrence in an amplifier, the phase of a signal voltage to be impressed to the non-linear resistor means and the phase of a distortion signal to generate are controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distortion which is inserted into a high-frequency transmission line and is used to correct secondary and tertiary distortions generated from the second and third terms in the input / output characteristics of an amplifier. The present invention relates to a correction device. In particular, the present invention can be applied to a distortion correction device that is used for a CATV transmission end and a repeater and that corrects CSO (composite second-order distortion) and CTB (composite third-order distortion) of an amplifier without reducing a fundamental wave.

[0002]

2. Description of the Related Art Conventionally, it is known that an amplifier using a transistor has nonlinearity in input / output characteristics and causes distortion in an output waveform. For example, with respect to the input wave shown in FIG. 16A, there is an output waveform in which the positive period is compressed and the negative period is expanded (FIG. 16B), or an output waveform having the opposite shape (FIG. c)). This is because, as shown in FIG. 17, the characteristics of the output current with respect to the input voltage of the transistor have a characteristic that the slope is gentle in both the region higher and the region lower than the center voltage. Note that FIG. 17 is exaggerated for explaining the non-linearity of the normally used non-saturation region, and the distortion waveform of FIG. 16 is also exaggerated. Generally, when an input voltage having an amplitude of ΔV is applied around the bias voltage VB1, the output I based on the output current corresponding to the bias voltage is described up to the third order term of the Taylor expansion at the bias point of the VI characteristic. Then, the following equation is obtained.

[0003]

I = A ₁ ΔV ± A ₂ (ΔV) ² −A ₃ (ΔV) ³ (1) However, A ₁ , A ₂ and A ₃ are positive.

[0004] A second-order distortion is generated from a squared term related to ΔV, and a third-order distortion is generated from a third-ordered term related to ΔV.
Therefore, when attention is paid to a signal having an arbitrary single angular frequency ω, its output is obtained by substituting a periodic function represented by ΔV = cosωt in the above equation. The output voltage V corresponding to the output current I is represented by the following equation. Here, the output V is a potential based on an output voltage corresponding to the bias voltage.

[0005]

V = a ₀ + a ₁ cos ωt ± a ₂ cos 2ωt−a ₃ cos 3ωt (2) where a ₁ , a ₂ and a ₃ are positive. Of these harmonics, the second and third harmonics, in particular, have a large coefficient and affect the first fundamental. This is the main cause of waveform distortion, and also causes distortion to be applied to other channels.

Here, from the symmetry of the VI characteristic, the coefficient of the second order term is divided into positive and negative depending on the bias point. FIG.
As shown in the figure, the bias point B2 is higher than the center point VB1.
In the case of (1), the plus side of the output signal amplitude is compressed and the minus side is expanded. This is because -a ₂ cos 2ωt
Means that a harmonic represented by That is,
This means that a harmonic having the opposite phase to the fundamental wave is generated. When the bias point is B1 lower than the center point VB1, the plus side of the output signal amplitude is expanded and the minus side is compressed. In this case, it means that a harmonic of + a ₂ cos 2ωt has been generated. That is, it means that a harmonic having the same phase as the fundamental wave is generated.

In the nonlinearity of the VI characteristic of the amplifier, there is a point symmetric component with respect to the center voltage. this is,
Third-order distortion means that the fundamental wave always generates a third-order harmonic having a coefficient opposite to the sign of the fundamental wave. Therefore, the fundamental wave and the third harmonic of the output from the amplifier always have an opposite phase relationship. Here, in the phase relationship between the fundamental wave and the third harmonic, when the fundamental wave has a positive maximum value, the case where the third harmonic has a positive maximum value is called in-phase. When the third harmonic has a negative maximum value when has a positive maximum value, it is called antiphase. In other words, if the coefficient of the first-order term and the coefficient of the third-order term have the same sign, the third harmonic has an in-phase relationship with the fundamental wave, and if it has a different sign, it has an anti-phase relationship. . When the transistor is used as an inverting amplifier, −1 is multiplied by the coefficients of the first and third order terms in equation (2).

In the above equation (2), an arbitrary single frequency is expressed. However, if signals of many frequencies are used as input signals, the terms of the second and third powers of the equation (1) are used. Second-order distortion and third-order distortion occur, respectively, and in a narrow sense, 2nd-order distortion occurs.
In addition to the second harmonic (2ω) and the third harmonic (3ω), the second-order intermodulation (such as ω ₁ ± ω ₂ ) and the third-order intermodulation (2ω ₁ ± ω ₂ ,
ω ₁ ± 2ω ₂ ) and cross modulation (ω _1, ω ₂ ). However, since these intermodulations are components generated at a constant ratio from the second and third power terms, the second harmonic (2ω) and the third harmonic ( 3
If they are canceled as represented by ω), all secondary distortion components and all tertiary distortion components will be canceled. Therefore, when an arbitrary single frequency is used as an input signal, the second harmonic (2ω) and the third harmonic (3ω)
ω) is corrected so that the second-order distortion and the third-order distortion are corrected. A circuit has been devised that corrects the second-order and third-order distortions and corrects the distortion of the amplifier.

The principle is to apply a distortion to an input signal before inputting the signal to an amplifier and cancel the distortion by the amplifier, or to cancel the distortion generated by the amplifier by the distortion generated in a subsequent circuit. That is, a circuit for generating a distortion component having a phase opposite to that of the distortion component generated by the amplifier is added to the front stage, the rear stage, or the intermediate portion of the amplifier to remove the distortion of the output stage.

As one example, there is a distortion correction device disclosed in Japanese Patent Application Laid-Open No. 9-102718. This is because the transmission line is separated into a main line and a double line, and a circuit in which a forward diode and a reverse diode are connected in parallel is directly inserted into the main line, or a forward diode is connected to each of the main and sub transmission lines of the push-pull circuit. Are inserted in these circuits to generate harmonics in phase with respect to the fundamental wave, and to superimpose the harmonics on the amplifier to compensate for the distortion.

Another example is disclosed in Japanese Patent Application Laid-Open No. HEI 3-179980.
There is a non-linear compensator for a high-frequency amplifier described in Japanese Patent Application Laid-Open No. 7-107. As described above, the transmission line is branched into a main line and a sub line, and an amplifier, a distortion generator, an amplitude adjuster, a frequency adjuster, and a phase adjuster are provided on the sub line side, and the two lines are recoupled. In this way, various harmonics are added to the fundamental wave propagating through the main line to compensate for various distortions caused by the amplifier.

[0012]

Problems to be Solved by the Invention Japanese Patent Application Laid-Open No. 9-102718
In the device disclosed in Japanese Patent Application Laid-Open No. HEI 3-179807 and the device disclosed in Japanese Patent Application Laid-Open No. HEI 3-179807, the transmission line is divided into a main line and a branch line. Distortion is added. Then, the fundamental wave propagating through the main line is inverted to superimpose the above-mentioned third-order distortion of minus sign, and both of them are set to minus sign to generate third-order distortion of the same phase. This is because the amplifier generates third-order distortion in the opposite phase to the fundamental wave due to its input / output characteristics. The distortion is corrected by canceling the input third-order harmonic of the same phase and the third-order harmonic of the opposite phase generated by the amplifier. However, the above operation has a drawback that the fundamental wave on the main line and the fundamental wave on the branch line have different signs, and as a result, the fundamental wave is attenuated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to connect an adjusting resistor to a branch terminal of a directional coupler, and to make a terminating resistor a non-linear resistor,
This generates harmonics between the terminals of the nonlinear resistor,
By outputting this harmonic to the output terminal of the directional coupler, the second and third-order distortions are accurately corrected.

[0014]

According to a first aspect of the present invention, there is provided a distortion correcting apparatus using a directional coupler including a transformer and a terminating resistor. The adjustment resistance is connected to the branch terminal of the directional coupler, the terminating resistance of the directional coupler is used as the non-linear resistance means, and a harmonic is generated by applying a part of the signal to the non-linear resistance means,
The harmonic is output from an output terminal, and the input / output characteristic of the directional coupler is set to be a constant multiple of a substantially inverse function of the input / output characteristic of the amplifier.

FIG. 14 shows the configuration of the present invention. The distortion correction device 1 has a directional coupler 11. FIG. 15 shows a detailed configuration of the directional coupler 11. The directional coupler 11 has a distortion generator 11a is a non-linear resistance means in place of the terminating resistor, adjusting resistance to the branch terminal BR R ₁
Is connected. When the adjustment resistor R ₁ is not equal to the characteristic impedance R (resistance) of the line, the directional coupler 1
A part of the fundamental wave input from one input terminal is input to the distortion generator 11a. Thereby, a harmonic of the fundamental wave is generated in the distortion generator 11a. The distortion generator 11a serves as a signal source of the harmonic. The directional coupler 11 shown in FIG. 14 has an input terminal for a signal on a transmission path,
The output terminal is defined, and in a normal use where the terminating resistor and the adjustment resistor are equal to the characteristic impedance, the branch terminal is forward-coupled to the input terminal (coupling relationship for transmitting a signal). In this connection relationship, a harmonic (distortion signal) using the distortion generator 11a as a termination resistor as a signal source.
Is output to the output terminal side in the above-described normal use state, and is not output to the input terminal side in a reverse coupling relationship.
However, in the present invention, intentionally not adjusted resistor R ₁ equal to the characteristic impedance R. Therefore, a distortion signal using the distortion generator 11a as a signal source is, as described later,
The signal is output to both the output terminal and the input terminal.

The input of the distortion correction apparatus 1 is x and the output is y
And its input / output characteristic is set to y = f (x). Also,
The input and output characteristics of the amplifier 2 connected to the subsequent stage of the distortion correction device 1 are represented by y and z, and the input / output characteristics thereof are represented by z = g (y). The relationship between the input x and the output z of one system including the distortion correction device 1 and the amplifier 2 is expressed by the following equation.

## EQU3 ## z = g (y) = g (f (x)) (3) In order to prevent distortion from occurring in the above system, it is sufficient that this system is linear. Therefore, if the following equation is satisfied, the output z is a constant multiple of the input x and does not include distortion.

G (f (x)) = γx (4) where γ is a constant.

This is because the function f of the input / output characteristic of the distortion correction apparatus 1 is converted into a constant γ of an inverse function of the function g of the input / output characteristic of the amplifier 2.
It means to set to double. In FIG. 14, the distortion correction device 1 is arranged before the amplifier 2.
The same relationship is established even if it is arranged at the subsequent stage. As described above, by setting the input / output characteristic f of the distortion correction device to be a constant multiple of the inverse function of the input / output characteristic g of the amplifier, it is possible to completely correct the distortion generated in the amplifier.

The approximate inverse function can be obtained as follows. By performing Taylor expansion of up to the third-order terms with respect to functions f and g, the following expressions can be obtained.

F (x) = C ₁ x + C ₂ x ² + C ₃ x ³ (5)

G (y) = D ₁ y + D ₂ y ² + D ₃ y ³ (6)

If the cubic expression of z is linearly approximated with respect to coefficients under the condition of C ₁ , D ₁ ≫C ₂ , D ₂ , C ₃ , D ₃ , the following expression is obtained.

Equation 7] _{z = C 1 D 1 x +} (C 2 D 1 + C 1 2 D 2) x 2 + (C 3 D 1 + C 1 3 D 3) x 3 (7)

Therefore, the condition that the second-order distortion and the third-order distortion are not included in the output z is as follows.

Equation 8] ^{_{C 2 D 1 + C 1 2}} D 2 = 0 (8)

Equation 9 is a ^{_{C 3 D 1 + C 1 3}} D 3 = 0 (9).

[0021]

Equation 10] ^{_{C 2 = -C 1 2 D 2}} / D 1 (10)

Equation 11] ^{_{C 3 = -C 1 3 D 3}} / D 1 (11)

## EQU1 ## If the input / output characteristics f of the distortion correction device are determined by the coefficients C ₂ and C ₃ , it is possible to approximately set a constant multiple γ = C ₁ D ₁ of the inverse function of the input / output characteristics g of the amplifier.

Further, in order to obtain a more approximated inverse function, the functions f and g are approximated by a polynomial and z = g (f (x))
Is determined, and the coefficient may be determined so that the square integration of the error between z and γx is minimized in the range of the variable x.

The coefficient is set as described above. Specifically, when distortion is generated by using the nonlinearity of a diode, the bias voltage may be adjusted. Since the VI characteristic of the diode is an exponential function, the value of each coefficient in the polynomial approximation of the characteristic can be changed by adjusting the bias voltage.

Then, only the harmonic component generated by the distortion generator 11a is propagated and superimposed on the fundamental wave on the transmission line, and the coefficients of the second and third terms of the above equation (7) become zero. Is done. As a result, a distortion correction device with higher correction efficiency than the conventional one can be obtained.

According to a second aspect of the present invention, there is provided a distortion correcting apparatus using a directional coupler comprising a transformer and a terminating resistor, wherein an adjusting resistor is connected to a branch terminal of the directional coupler, and a termination of the directional coupler is provided. Using the resistance as nonlinear resistance means, applying a part of the signal to the nonlinear resistance means to generate harmonics,
This harmonic is output from the output terminal, and is superimposed on the output terminal of the directional coupler in a phase relationship opposite to the phase of the harmonic by the amplifier so that the harmonic is canceled by the harmonic generated by the amplifier. It is characterized by doing.

For example, it is assumed that the directional coupler is a reverse-phase directional coupler. Note that an in-phase directional coupler refers to a coupler in which the phase relationship between an input signal or an output signal and a branch signal is in phase, and an anti-phase directional coupler refers to an input signal or an output signal. A type of coupler in which the phase relationship between a signal and a branch signal is opposite.

The directional coupler according to the second aspect of the present invention is the directional coupler according to the first aspect.
This is the same as the directional coupler.
The reason why distortion is output to the output terminal side
I do. The same applies to the invention of claim 1. Directional connection
The combiner 11 is used instead of the terminating resistor in the case of normal use.
Equipped with non-linear resistance means, adjust the branch terminal for normal use.
A rectifying resistor is connected. The resistance value of this adjustment resistor
R₁, The characteristic impedance (pure resistance) of the line is R,
The resistance of the mold resistance means is R_Two, Current transformer, voltage transformer
Is 1: n. In the following, the symbol R of the adjustment resistor will be described.
₁And its resistance R₁Is the same symbol as the non-linear resistance
Symbol R_TwoAnd its resistance R_TwoAre denoted by the same symbols. Current
The primary winding of the lance and voltage transformer is composed of an input terminal and an output terminal.
The winding connected to the main line connecting the
The winding that is electromagnetically coupled to the primary winding is defined as the secondary winding.
You. Let the signal voltage at the input terminal be v and the current be i. Current
A current of i / n flows through the secondary winding by the lance. Also,
Since the terminal voltage of the primary winding of the voltage transformer is v,
The terminal voltage of the winding is v / n. Adjustment resistance R₁And non-linear
Resistance means R_Two, The current source i / n and the voltage source v / n
It is equivalent to being applied. Therefore, the branch terminal BR
Voltage of V₁, Non-linear resistance means R_TwoTerminal voltage to V _Two,
Adjustment resistance R₁, Voltage transformer secondary winding, non-linear resistance element
Child R_TwoThe current flowing through the closed circuit of I₀Then
Stand up.

[0029]

I ₀ = v / [n (R ₁ + R ₂ )] (12) The current i ₂ flowing through the non-linear resistance means R ₂ by the current source i / n is obtained by the following equation.

Equation 13] i ₂ = iR ₁ / [(R ₁ + R ₂₎ n] (13) Therefore, the terminal voltage V ₂ of the non-linear resistance means R ₂ is obtained by the following equation.

V ₂ = (I ₀ −i ₂ ) R ₂ (13) Substituting equations (12) and (13) into equation (14), if n is sufficiently large, then v = iR. The following equation is obtained.

V ₂ = (R−R ₁ ) R ₂ i / [(R ₁ + R ₂ ) n] (15)

[0030] Therefore, in the case of R ₁ <R is the non-linear resistance means R _2, the voltage signal V ₂ of the input and output signals in phase are applied, in the case of R <R _1, the input signal and the voltage signal of the output signal and the opposite phase V ₂ is applied. Therefore, the resistance value R ₂ of the nonlinear resistance means R ₂ is equal to the characteristic impedance R
If not, in the nonlinear resistance means R ₂ ,
Harmonics (for example, second harmonic, third harmonic) are generated. This is equivalent to a case where a harmonic is oscillated from a place where a normal termination resistor is arranged. Therefore, regarding the harmonic (distortion signal), the non-linear resistance means becomes a signal source. For this signal source, the anti-phase directional coupler branches this harmonic to the output terminal side in phase. The signal is output to the input terminal side at the same ratio as the ratio branched to the nonlinear resistance means, but this signal propagates upstream and is consumed by the original signal source. As described above, the branch output of the harmonic generated at the output terminal of the directional coupler is multiplexed with the fundamental wave transmitted through the transmission path.

The phase relationship between the harmonics generated by the non-linear resistance means and the fundamental wave is arbitrarily determined depending on the direction of a diode, for example. For example, a second harmonic in phase or opposite to the applied fundamental wave, or a third harmonic in opposite phase can be generated. In the case of the third harmonic, it is necessary to combine at the output terminal of the directional coupler in the same phase relation as the fundamental wave at the output terminal. Accordingly, if the fundamental wave signal V ₂ applied to the non-linear resistance element R ₂ has an opposite phase to the fundamental wave signal v of the input signal, the third harmonic having the same phase as the fundamental wave signal v can be generated. It is possible to output the third harmonic in the same phase as the fundamental wave at the output terminal. For this purpose, the adjustment resistor R ₁ may be made larger than the characteristic impedance R.

On the other hand, in the case of a directional coupler of the in-phase type, in order to output the third harmonic in the same phase as the fundamental wave at the output terminal, the following method may be used. In a directional coupler of the in-phase type, a distortion signal generated by a non-linear resistance means as a terminating resistor is inverted in phase and output to an output terminal. Therefore, it is sufficient to generate a third harmonic in a phase opposite to the fundamental wave at the input terminal and the output terminal. As described above, the non-linear resistance means R
₂ generates a third harmonic having a phase opposite to that of the applied voltage V ₂ , so that the applied voltage V ₂ may be set to the in-phase voltage with respect to the fundamental wave of the input terminal and the output terminal. The terminal voltage V ₂ of the non-linear resistance means of the in-phase type is different from that of the anti-phase type in the direction of the current source and the voltage source. Becomes

[0033]

V ₂ = − (R−R ₁ ) R ₂ i / [(R ₁ + R ₂ ) n] (16) Therefore, if the resistance value R ₁ of the adjustment resistor R ₁ is made larger than the characteristic impedance R, , it is possible to apply a voltage of the fundamental wave and the phase at the input and output terminals to the non-linear resistance means R _2. Therefore, it is possible to generate a third harmonic having a phase opposite to that of the fundamental wave, invert the phase, and output a third harmonic having the same phase as the fundamental wave at the output terminal.

In the case of the second-order distortion, by changing the bias voltage of the diode and selecting the direction of the diode, the second-order distortion of the same phase and the opposite phase with respect to the applied voltage can be generated. There is no need to increase the adjustment resistor R ₁ with respect to the characteristic impedance R. If the adjustment resistor R ₁ is set to a value different from the characteristic impedance R, a second-order distortion is generated so as to compensate for the second-order distortion generated in the amplifier. It is possible to

The third harmonic of the signal input to the amplifier is
As described above, it is in phase with the fundamental wave. This makes it possible to cancel the third-order harmonic of the opposite phase generated by the amplifier. As a result, harmonic distortion by the amplifier is corrected. In particular, by adjusting the branching ratio and adjusting the resistance R ₁ by the directional coupler can be a 0 distortion components at the output of the amplifier. That is, as described above,
If the conditions that can be set are set, the second order term of the input / output characteristics, 3
All secondary distortion components and tertiary distortion components generated from the following terms can be set to zero.

In claim 2, the fundamental wave is a signal of one frequency of interest among the wideband signals. When attention is paid to a signal of a single frequency ω, harmonics of 2ω are generated from the second term of the nonlinear characteristic and 3ω are generated from the third term. When a broadband signal is input to a nonlinear element, second-order and third-order intermodulation components are generated. The harmonic with respect to the fundamental wave of claim 2 is used in the sense of a representative value of a spectrum resulting from a higher-order term of the nonlinear characteristic, and the harmonic component is compensated for a single frequency component ω. If the form of distortion generation by the distortion generator is adjusted as described above, all spectra resulting from higher-order terms can be compensated. Therefore, the adjustment of the distortion generator with respect to the harmonic according to claim 2 means that the distortion is adjusted as in claim 2 in an all-pass state. Alternatively, for example, if a filter is present in the amplifier and the pass band is finite, it means that the adjustment is performed by paying attention to harmonics in the band.

The relationship between the nonlinearity and the frequency spectrum will be described. Let v (t) be a wideband signal and F (ω) be its frequency spectrum distribution (Fourier transform). Then, the frequency spectrum distribution (Fourier transform) W ₂ (ω) of the square signal v (t) ² of v (t) is obtained by the following equation.

W ₂ (ω) = ∫F (ω−γ) F (γ) dγ (17) Similarly, the frequency spectrum distribution (Fourier transform) W ₃ (ω) of v (t) ³ is expressed by the following equation. Is obtained.

W ₃ (ω) = ∫W ₂ (ω−γ) F (γ) dγ (18)

That is, the frequency spectrum distribution of the squared signal v (t) ^{2 is one} of the frequency spectrum distributions of the signal v (t).
Times convolution (autocorrelation function), and the frequency spectrum distribution of v (t) ³ is obtained by two convolutions of the frequency spectrum distribution of the signal v (t) or the squared signal v (t)
It is expressed by the convolution integral (cross-correlation function) of the frequency spectrum distribution of ( ² ) and the frequency spectrum distribution of the signal v (t).

In equation (17), ω₀Single-spectrum field of
In other words, F (ω) is changed to δ (−ω ₀), Δ (ω₀)When
Then, W_Two(Ω) is δ (−2ω)₀), Δ (0), δ
(2ω₀) Are obtained. This is
Wave number ω₀From the squared term for the fundamental wave of 2ω₀Harmonic of
That's why you get waves. Similarly, the expression (18)
And ω₀Given a single spectrum of
_Three(Ω) is δ (−3ω)₀), Δ (-ω₀), Δ
(Ω₀), Δ (3ω₀) Are obtained.
You. This is the frequency ω₀For the fundamental wave of
3 ω₀Harmonics and ω₀The fundamental wave of
You.

Assuming that the spectral components of the above-mentioned squared signal and cubic signal are generated by the amplifier, these squared signals,
Next, the necessary and sufficient conditions in which the spectral components of the cubic signal are canceled by the spectral components of the squaring signal and the cubic signal output from other nonlinear elements will be considered. When the spectral components of the square signal are eliminated, all spectra resulting from the square are eliminated at the same time. Therefore, the necessary and sufficient condition is that all spectra of the squared signal are simultaneously eliminated for an arbitrary F (ω). Any F
(Ω) holds for a single frequency, ie, F
This means that (ω) holds for any number of δ functions.
Since an arbitrary F (ω) can be considered as a set of δ functions, a necessary and sufficient condition for eliminating the spectral component of the square signal is that the second harmonic 2ω ₀ is eliminated for a single frequency ω ₀ . That is.

Similarly, a necessary and sufficient condition for eliminating the spectral component of the cubic signal is that the third harmonic 3ω ₀ is eliminated for a single frequency ω ₀ . That is, the spectrum distribution W ₂ (ω) of the square signal is represented by the second harmonic, and the spectrum distribution W ₃ (ω) of the cube signal is represented by the third harmonic.
Can be represented. Claim 2 describes this, and if adjusted as in claim 2, the spectral component of the squared signal, the spectral distribution of the cubed signal, or
Spectral components of other high-order power signals can be entirely eliminated.

Further, the distortion correcting device according to the third aspect generates a second-order distortion in the directional coupler as the nonlinear resistance means.
A secondary distortion generating circuit is provided. In the secondary distortion generating circuit which is a feature of the present invention, for example, the direction of the diode is set to the earth direction or the opposite direction, one end of which is connected to the terminating resistor terminal of the directional coupler and the other end is connected to the earth via, for example, a resistor. It is connected. As a result, in-phase or out-of-phase secondary distortion can be generated with respect to the voltage applied to the non-linear resistance means. With respect to this second-order distortion, the directional coupler having the opposite phase can output the second-order distortion signal of the same phase to the output terminal, and the directional coupler having the same phase outputs the second-order distortion signal of the opposite phase to the output terminal. Can be done. Eventually, second harmonics in phase and opposite to the fundamental wave are added depending on the direction of the diode. In other words, the direction of the diode is selected according to the distortion characteristics of the amplifier connected to the transmission line, and the direction of the diode is selected accordingly.
Second harmonics can be added.

The second harmonic is input to an amplifier comprising a transistor. The input second harmonic is superimposed and canceled by a newly generated second harmonic of a different sign by the transistor. Thereby, the second harmonic generated by the amplifier is corrected.

[0044] Further, it is adjusted the ratio of distortion generated in the shunt ratio, etc. to the bias voltage and the diode of the diode of the branching ratio and adjusting the resistance R ₁ and second-order distortion generating circuit according to the directional coupler, the second-order amplifier The distortion component can be set to zero. As described above, under the condition that the second harmonic is 0 with respect to the fundamental wave, when a wideband signal is input, all the second-order distortion components generated from the square term of the input / output characteristics may be set to 0. it can. This enables high-quality transmission without secondary distortion.

Further, the distortion correcting device according to claim 4 generates a third-order distortion in the directional coupler as the nonlinear resistance means.
A secondary distortion generating circuit is provided. The operation of the directional coupler is the same as in claims 1 to 3. The third-order distortion generating circuit used in the present invention is configured such that, for example, two diodes are configured in parallel so that their directions are different from each other, one end of which is connected to the terminating resistor terminal side and the other end is connected to the ground via, for example, a resistor. I have. The signal input to the terminating resistor terminal of the directional coupler has a signal current flowing according to the non-linear characteristic of the diode of the third-order distortion generating circuit and is consumed. That is, the potential of the terminating resistor terminal decreases and the signal amplitude is compressed. In other words, in the third-order distortion generating circuit, the fundamental wave applied to the terminating resistor terminal always has the opposite phase (having a different sign) 3
A second harmonic is generated.

This third harmonic is output to the output terminal of the directional coupler, and is superimposed on the fundamental wave. The waveform is a waveform that is extended vertically with respect to the basic waveform. The fundamental wave and the third harmonic having the same sign as the fundamental wave are input to an amplifier including, for example, a transistor. The input third harmonic is superimposed and canceled by the transistor with a newly generated third harmonic of a different sign. Thereby, the third-order distortion due to the amplifier is corrected. Again, splitting ratio by the directional coupler, the magnitude of the resistance value R ₁ of the adjusting resistor R _1, by adjusting the flow ratio of the third order distortion generator circuit of a diode, the third-order distortion component of the amplifier to 0 be able to. In the above description, the third harmonic is set to 0. In this state, in the case of a wideband signal, all the third-order distortions generated from the third-order term of the input / output characteristics are set to 0. And high quality transmission becomes possible.

Further, the distortion correcting apparatus according to the fifth aspect is characterized in that the directional coupler is provided with a harmonic distortion generating circuit for simultaneously generating the second-order distortion and the third-order distortion as the nonlinear resistance means. This harmonic distortion generating circuit includes, for example, a secondary distortion generating circuit that generates a second harmonic and a third harmonic that adds a third harmonic.
A secondary distortion generating circuit is connected in series or in parallel. The operation of the directional coupler is the same as that of claims 1 to 6. In the present invention, the fundamental wave input from the input terminal is applied to the terminating resistor terminal of the directional coupler, and is applied to the secondary distortion generating circuit and the tertiary distortion generating circuit. Thus, at the output terminal of the directional coupler, the second harmonic having the same sign (in-phase) or the opposite sign (out-of-phase) and the third harmonic having the same sign (in-phase) are added to the fundamental wave.

These signals are input to an amplifier composed of, for example, a transistor, and are generated by the amplifier.
The higher harmonics and the second harmonics of the same sign or different signs are canceled. In this state, all the second-order distortion components and all the third-order distortion components by the amplifier can be simultaneously corrected.

This correction is effective for all the second-order distortion components and all the third-order distortion components generated for the wideband signal by the amplifier. Therefore, it becomes an extremely efficient distortion correction device. When the secondary distortion generator is constituted by a diode, its input / output characteristics are exponential functions.
The coefficient of the third power is also relatively large. For this reason, 2
A third-order distortion is generated at the same time as a third-order distortion is generated. For this reason, in the third-order distortion generator, 3
The third-order distortion is generated so as to compensate for the third-order distortion and the third-order distortion generated by the second-order distortion generator.

Further, the distortion correcting apparatus according to claim 6 has an adjusting means for adjusting the amount of nonlinear distortion generated in the nonlinear resistance means. The nonlinear resistance means is, for example, a diode circuit, and the amount of distortion caused by the non-linear resistance means can be controlled by the amount of current flowing. Therefore, for example, if the bias voltage applied to the diode circuit is adjusted by the adjusting means to control the flowing current, the amount of distortion can be adjusted. Thus, the distortion of the amplifier can be accurately corrected by adjusting the amount of distortion to be added in accordance with the amount of distortion of the connected amplifier. Further, the adjusting means may be, for example, an attenuator or a linear amplifier, and these may be provided between the terminating resistance terminal and the non-linear resistance means. The amount of distortion can also be adjusted by such an adjusting means.

[0051]

Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following examples. (First Embodiment) The amplifier used in the description of the present embodiment is a positive-phase amplifier for simplifying the explanation of the phase relationship, and is inputted with a bias higher than the middle point. It is assumed that the amplifier has a characteristic in which the positive period of the fundamental wave is compressed and the negative period is extended, that is, an amplifier to which a second harmonic having a reverse phase relationship is added to the fundamental wave (corresponding to FIG. 17B). The distortion correction device of the present invention is effective for an amplifier having such distortion characteristics.

FIG. 1 is a block diagram showing the configuration of the distortion correction apparatus according to the present invention. Distortion correction apparatus of the present invention, a directional branch transformer 20 is a directional coupler to the transmission path 60, in that connected to the branch terminals BR the adjustment resistor R ₁ and a non-linear resistor means connected to the termination resistor terminal And a certain second-order distortion generator 200. The resistance value R ₁ of the adjusting resistor R ₁ is set to a value greater than the characteristic impedance R of the line. At this time, a fundamental wave having a phase opposite to that of the fundamental wave at the output terminal OUT is applied to the second-order distortion generator (nonlinear resistance means) 200 according to the equation (15).

FIG. 2 shows the configuration of each of the directional branch transformers 20. The directional branch transformer 20 has a current transformer 21 and a voltage transformer 22. The adjustment resistor R ₁ and the terminating resistor terminal T connected to the branch terminals BR
Is connected to the second-order distortion generator 200 connected to. Incidentally, the resistance value of the second order distortion generator and R _2.

A description will be given in accordance with the signal flow with reference to FIG. Hereinafter, the high-frequency signal (CA
TV signal), for example, V = V ₀ co
Focusing on s ωt, it is assumed that the signal is input to the input terminal IN of the directional branch transformer 20 via the signal source resistance Rs. The signal is output by the directional branch transformer 20 to the transmission line 60 in the same phase and the opposite phase to the branch terminal BR and the terminating resistor terminal T. When a directional coupler is used as in the present invention, the branching ratio r does not become 1 / n ^{2 because} the voltage at the terminating resistor terminal T is used so as not to become 0. n
Is the winding ratio. Therefore, defined as the ratio of the power loss sum of the adjustment resistor R ₁ and a non-linear resistance means R ₂ for signal power at the input terminal of the branching ratio r here. That is, the branching ratio r is defined by the following equation.

[0055]

R = (R ² + R ₁ R ₂ ) / [R (R ₁ + R ₂ )] (19) With this definition, the signal transmitted to the transmission line 60 is
(1−r) ^1/2 V ₀ cos ωt. Also, the non-linear resistance means R
₂ of the terminal voltage V ₂ is the use of the equation (15) and V ₀ = iR relation, the following equation.

[0056]

V ₂ = (R−R ₁ ) R ₂ V ₀ / [(R ₁ + R ₂ ) Rn] cos ωt (20) Here, V ₂ is expressed by the following equation.

[Number 21] ^{_{V 2 = -r 2 1/2 V 0}} cos ωt (21)

R ₂ = {(R−R ₁ ) R ₂ / [(R ₁ + R ₂ ) Rn]} ² (22)

That is, r ₂ is the power branching ratio to the non-linear resistance means R ₂ . Thus, the power distribution ratio to the adjustment resistor R ₁ connected to the branch terminal BR is the r-r _2.

In the following, V₀cos ωt is expressed by E
In some cases. Also, the non-linear resistance means R_TwoDistortion caused by
The signal is (rr_Two)^1/2Output to the output terminal.
And r _Two ^1/2It is multiplied and output to the input terminal. Hereafter, corner
The signal of frequency ω is a fundamental wave, 2ω is a second harmonic, 3ω is 3
Described as the second harmonic.

As described above, the secondary distortion generating circuit 200
The fundamental wave of -r ₂ ^1/2 E is applied. At this time, 2
This is equivalent to adding a pseudo signal source for generating a second harmonic in the second distortion generation circuit 200.

The secondary distortion generating circuit 200 in this embodiment
3 is shown in FIG. The secondary distortion generating circuit 200 mainly includes a Schottky diode 210, a bias circuit 220 for applying a DC bias voltage thereto, and a bypass circuit 240 for passing a high-frequency signal. When the forward bias voltage is applied in the direction in which the high-frequency signal is applied, the direction of the diode 210 is the forward direction. When the forward bias voltage is applied in the direction opposite to the direction in which the high-frequency signal is applied, the diode 210 is in the forward direction. The direction is called the opposite direction. In the circuit diagram of FIG. 3, the direction of the diode 210 is opposite. FIG. 4 shows a current-voltage characteristic VI of the diode. FIG. 4A shows the VI characteristics in the forward direction, and FIG. 4B shows the VI characteristics in the reverse direction. As shown in FIG.
If the bias of the diode 210 is set to
The distortion as shown in the figure occurs due to the nonlinearity.

The fundamental wave −r ₂ ^1/2 V ₀ cos ωt input to the second-order distortion generating circuit 200 depends on the signal voltage.
DC blocking capacitor C1, Schottky diode 2
10 or the bypass circuit 240 and the DC cutoff capacitor C2 (FIG. 3). That is, the operation is centered on the bias voltage B1 shown in FIG. The signal voltage at that time is expressed as ΔV = −kr ₂ ^1/2 V ₀ cos ωt. Here, k is a proportionality constant determined by a shunt ratio with the bypass circuit 240.

As shown in FIG. 4 (b), the positive period of the input signal is compressed, and the negative period is a waveform B with expanded waveform distortion (FIG. 4 (b)). However, since the current and the terminal voltage have an opposite phase relationship, the voltage waveform is an inverted waveform. This means that the second harmonic having the same phase is added to the fundamental wave of the input signal of the Schottky diode 210. If the second harmonic having a positive coefficient is described by the equation (2), + A ₂ cos (2ωt) is added.

The distortion characteristic of the in-phase amplifier to be compensated is
If the characteristic is such that a second harmonic having a reverse phase relationship to the fundamental wave of the output signal is generated, the Schottky diode 2
10 is used in the forward connection for the input signal (FIG. 5).
In this case, when the above signal is input, the output current waveform becomes the waveform A in FIG. 4 which is expanded in the positive period side and compressed in the negative period side. This means that a second harmonic having a phase opposite to that of the fundamental wave of the input signal of the Schottky diode 210 is generated, and in equation (2), -a ₂ cos (2ωt) is added. means.

In this embodiment, the Schottky diode 2
10 is reverse-connected to the input signal,
入 力 V = -r_Two ^1/2kV₀cos ωt
And the output is V = −r according to equation (2)._Two ^1/2V₀cos ω
t + α (r_Two ^1/2kV₀)^TwoIt is approximated by cos2ωt. This
Here, α is the second-order distortion due to the Schottky diode 210
It is a coefficient corresponding to only This α (r_Two ^1/2kV₀)^Twoco
s 2ωt is a representative value of the secondary distortion component. And reversed phase
Type directional coupler has a terminal resistance terminal T as a signal source
And the branching ratio (r−r) for this signal source._Two), Out in phase
A signal is output to the output terminal and the branching ratio r_Two, Input terminal in phase
The signal is output to the branching ratio (1-r) and the adjustment resistor is in phase.
R₁Is output to Therefore, the second harmonic α (r_Two
^1/2kV₀)^Twocos 2ωt to branching ratio (rr_Two)^1/2Is raised
Is calculated as α (rr_Two)^1/2r_Two(KV ₀)^Twocos2ωt
Then, the signal is propagated to the output terminal OUT.

On the other hand, the fundamental wave propagated through the transmission line 60 is (1−
r) Output to the output terminal OUT at ^1/2 V ₀ cos ωt. Then, as a result of the multiplexing at the output terminal, the output of the directional branch transformer 20 can be expressed by the following equation.

Vout = (1−r) ^1/2 V ₀ cosωt + α (rr ₂ ) ^1/2 r ₂ (kV ₀ ) ² cos 2ωt (23) The second term α (rr ₂ ) ^{1 / 2} r ₂ (kV ₀ ) ² cos2ωt is
Regardless of the sign of the first term, it means that a second harmonic having a + sign is always superimposed. In terms of waveforms, the output period (1−r) ^1/2 V ₀ cos ωt extends on the positive side,
The negative period represents the compressed waveform.

The signal accompanied by the distortion is subsequently supplied to the amplifier 5
0 (FIG. 1). In the present embodiment, as described above, it is assumed that the amplifier has a distortion characteristic of generating an even harmonic of a minus sign with respect to the fundamental wave of the input signal. Therefore, when the signal Vout expressed by the equation (23) accompanied by distortion is input, the fundamental wave (1−r) ^1/2 V ₀ cosωt is applied to the fundamental wave of the output signal by the second order of the sign. Strain-β ((1-r)
^1/2 V ₀ ] ² cos2ωt is output. Here, β corresponds to the coefficient of the square term of the input / output characteristics of the amplifier.

The newly generated second-order distortion −β [(1−r)
^1/2 V ₀ ] ² cos2ωt is the input second-order distortion + α
^{_{(R-r 2) 1/2 r}} 2 (kV 0) 2 cos2ωt and frequency identical, the phase is inverted. Therefore, the coefficient of the secondary component + α
(R−r ₂ ) ^1/2 r ₂ k ² −β (1−r) becomes zero,
If the branch ratios r and r ₂ , the proportional constant k by the bypass circuit 240, and the coefficient α of the square term by the Schottky diode 210 are selected, the distortion can be canceled from the output of the amplifier.

This is because the Schottky diode 210
The component expanded / compressed by the linearity
Conversely, compression / expansion is performed depending on the input / output characteristics (non-linear).
This means that amplifier harmonic distortion is corrected.
You. This allows an output waveform that is faithful to the input waveform to be transmitted.
You. The second harmonic αr appearing at the input terminal_Two ^3/2(kV₀)^Two
cos2ωt returns to the signal source and is consumed by its internal resistance.
It is. Also, the branching ratio (1-r), that is, α (1-r) ^1/2
r_Two(kV₀)^TwoThe signal of cos2ωt is the adjustment resistance R₁By
Consumed.

[0069] Thus, the fundamental wave of any single frequency ω
On the other hand, as described above, at the output of the amplifier,
Bias voltage and circuit of distortion generator so that harmonics are set to 0
If the constant is adjusted, the total
All secondary distortion components can be reduced to zero,
The distortion can be corrected. This allows connection to the transmission line.
The second-order distortion of the connected amplifier is accurately corrected, and the attenuation is low.
A reduced CATV signal can be obtained.

(Second Embodiment) An amplifier used in the description of the present embodiment has an input / output characteristic which is different from that of the center point of the amplitude with respect to the center point of the amplitude, such as a push-pull amplifier in which the secondary distortion component is corrected. It has symmetric nonlinearity. That is, it is an amplifier that generates third-order distortion generated from the third power term of the input / output characteristics. For a single fundamental at an arbitrary frequency,
It has a characteristic that both negative periods are compressed, that is, a characteristic that a third-order harmonic having an antiphase relationship with the fundamental wave is added. The distortion correction device of the present invention is effective for an amplifier having such distortion characteristics.

The configuration of the distortion correction device of the present invention is the same as that of the first embodiment. A different point is that a third-order distortion generating circuit 300 for adding a third-order distortion is employed instead of the second-order distortion generating circuit 200 of the directional splitter 20 (FIG. 6).
The parts having the same functions as in the first embodiment are given the same numbers. As described above, the fundamental wave applied to the third-order distortion generating circuit 300 is −r ₂ ^1/2 V ₀ cosωt. Due to the nonlinearity of the third-order distortion generating circuit 300, 3
The second harmonic is generated. FIG. 7 shows the third-order distortion generating circuit 300. As a result, a third harmonic is added to a fundamental wave of any single frequency. The third-order distortion generation circuit 300
It comprises Schottky diodes 310 and 320 formed in parallel in different directions, a bias circuit 330 for applying a DC bias voltage thereto, and a bypass circuit 340 for passing a part of the fundamental wave. Bias circuit 330
Is composed of an AC cutoff coil L1 and an adjustment resistor R1. Capacitors C1, C2 and C3 are for direct current cutoff, coupling and bypass.

Schottky diode 3 connected in parallel
The integrated input / output characteristics of 10, 320 become a hyperbolic sine function as shown in FIG. The horizontal axis represents the AC voltage at point B, and the vertical axis represents the AC current flowing positively from point B to the ground. The origin is the Schottky diode 310, 320
Of a bias voltage V _B applied to the forward direction, respectively.
When Taylor expansion around the bias point V _B, 1 square of terms and cubed terms from the point symmetry is dominant, each of the coefficients is positive. A distortion is added by the current i. Since the voltage v at the point B generated by the current i and the current i flowing through the diode 320 have a phase difference of 180 degrees,
In the Taylor expansion regarding the voltage at the point B, the coefficient of the third power term is negative. Therefore, the effect of this distortion acts to compress the signal voltage of the fundamental wave both positively and negatively.

This is because the third-order distortion generated in this way is generated.
In the raw circuit 300, the fundamental wave -r_Two ^1/2V₀cos ω
For t, + α (r_Two ^1/2kV
₀)^ThreeThis means that a harmonic of cos3ωt is added.
In other words, the termination resistance terminal T of the directional branch transformer 20
, The third harmonic is generated by the third distortion generating circuit 300.
Is equivalent to the insertion of a signal source that generates This 3
The second harmonic has a branching ratio (r−r_Two)^1/2Is multiplied by + α
(Rr_Two)^{1 / Two}(R_Two ^1/2kV₀)^Threecos3ωt
Output to the output terminal OUT in phase. The third harmonic
The remaining component (1-r)^1/2Double signal is directional branch
Adjustment resistance R of transformer 20₁Consumed by_Two ^1/2No faith
Signal is consumed by the internal resistance of the signal source upstream from the input terminal.
You. Note that the coefficient α is the Schottky diode 31
0, 320 bias voltage V _BCan be adjusted. Ma
Where k is determined by the shunt ratio of the current to the bypass circuit 340.
And can be adjusted by the size of the resistor R3.
(FIG. 7).

Then, at the output terminal OUT of the directional branch transformer 20, the third harmonic α (rr- ₂ ) ^1/2 (r
₂ ^1/2 kV ₀ ) ³ cos3ωt and the fundamental wave propagated through the transmission line
(1−r) ^1/2 V ₀ cos ωt is superimposed. As a result, the output from the directional branch transformer 20 is expressed by the following equation.

[0075]

Vout = (1−r) ^1/2 V ₀ cos ωt + α (r−r ₂ ) ^1/2 (r ₂ ^1/2 kV ₀ ) ³ cos 3ωt (24) Here, the coefficient of the first term (1−r) ^1/2 V ₀ and the second term
The coefficient α (r−r ₂ ) ^1/2 (r ₂ ^1/2 kV ₀ ) ^{3 of the term} is both positive. This means that the third harmonic is added in phase with the fundamental wave. In this case, both the positive period and the negative period of the fundamental wave are extended.

The signal accompanied by this distortion is similarly supplied to the amplifier 5
Input to 0. The amplifier in this case, as described above,
An amplifier that generates a third harmonic having a different sign with respect to the input fundamental wave. That is, the signal V expressed by the equation (24)
When out is input, a third harmonic -β (1−r) ^3/2 V ₀ ³ cos 3ωt in phase opposite to the fundamental wave (1−r) ^1/2 V ₀ cos ωt is generated. The third harmonic -β (1
−r) ^3/2 V ₀ ³ cos3ωt and the input third harmonic α (r
−r ₂ ) ^1/2 (r ₂ ^1/2 kV ₀ ) ³ cos 3ωt has the same frequency and inverted phase. Therefore, in particular, α, the branching ratio r, r ₂ and the constant k are set so that the two coefficients are equal.
Is selected, the third harmonic can be set to 0 from the output of the amplifier. By setting the third harmonic with respect to the fundamental wave to be 0 as described above, all the 3rd harmonics generated from the third term of the input / output characteristics when a general wideband signal is used as an input signal.
The next-order distortion component can be set to zero.

(Third Embodiment) In the amplifier used in the description of this embodiment, the bias point is set higher than the median value, the positive and negative periods of the fundamental wave of the output signal are compressed, and the output signal is compressed. It is assumed that the amplifier has a characteristic in which the positive period of the fundamental wave is relatively compressed and the negative period is extended, that is, an amplifier to which a third harmonic having a reverse phase and a second harmonic having an antiphase relationship are added to the fundamental wave. . That is, for the input signal V ₀ cosωt, −β ₁ V _o
Third harmonic of the second harmonic of the ² Cos2omegati and -β ₂ V _o ³ cos3ωt is to an amplifier that is generated. The distortion correction device of the present invention is effective for an amplifier having such distortion characteristics.

The configuration of this embodiment is the same as that of the first and second embodiments (FIG. 1). The difference is that, instead of the second-order distortion generating circuit 200 of the first embodiment, the second-order distortion generating circuit 200 (FIG. 3) and the third-order distortion generating circuit 300 (FIG. 7) are connected in parallel. (FIG. 9). A second-order distortion generating circuit 200 and a third-order distortion generating circuit 30 connected in parallel to FIG.
Indicates 0. Here, similarly, the secondary distortion generating circuit 200,
The third-order distortion generating circuit 300 applies +
It is set so that the second harmonic of the sign and the third harmonic of the opposite sign are added. Here, the symbols of R, C, and L are those in which the tenth digit of the two-digit number is one, and
The one related to 0 and the one where the digit of ten is two relates to the third-order distortion generating circuit 300. The numeral of 1 digit corresponds to those in the first embodiment and the second embodiment.

The process of branching the signal in the directional branching transformer 20 and generating the distortion signal is the same as in the first and second embodiments, so that the description thereof will be omitted, and the secondary distortion generation circuits 200 and 3 will be omitted.
The operation of the secondary distortion generating circuit 300 and the process of correcting the amplifier will be mainly described. The signal −r ₂ ^1/2 V ₀ cosωt is applied to the second-order distortion generating circuit 200, so that, as in the first embodiment,
The + second harmonic + α ₁ r ₂ (k ₁ V ₀ ) ² cos 2ωt is added to the fundamental wave −r ₂ ^1/2 V ₀ cos ωt. Similarly, by being applied to the third-order distortion generating circuit 300, the second embodiment similar to the fundamental wave -r ₂ ^1/2 V ₀ cos .omega.t, 3 harmonic different signs + α ₂ (r ₂ ^{1 / 2} k ₂ V ₀ ) ³ cos3ω
t occurs.

The (r−r) of these signals_Two)^1/2Double signal
Is the fundamental wave (1-r) that has propagated through the transmission line. ^1/2V₀cosωt and heavy
Be folded. Therefore, the result of the multiplexing at the output terminal OUT is
It becomes an expression.

[Number 25] ^{Vout = (1-r) 1/2} V 0 cosωt + α 1 (r-r 2) 1/2 (r 2 1/2 k 1 V 0) 2 cos2ω t + α 2 (r-r 2) 1 / ² (r ₂ ^1/2 k ₂ V ₀ ) ³ cos3ωt (25)

Here, the second term means that a second harmonic having a + sign is always superimposed regardless of the sign of the first term. In terms of waveform, input wave (1-r) ^1/2 V ₀ co
With respect to s ωt, the waveform is expanded on the positive side and compressed on the negative side. The coefficient of the first term and the coefficient of the third term are
Since k, α, and r are all positive, they are both positive. This means that the third harmonic is added in phase with the fundamental wave. In terms of waveform, the waveform is a waveform that is extended in both the positive and negative periods of the fundamental wave.

Next, this signal is input to the above-described amplifier. The above-described amplifier has a characteristic of relatively compressing the positive period of the fundamental wave and extending the negative period. Therefore, when the fundamental wave (1−r) ^1/2 V ₀ cosωt of the first term is input, −β ₁ (1
−r) V ₀ ² cos2ωt is added. At the same time, the amplifier has a characteristic that both the positive period and the negative period of the fundamental wave of the output signal are compressed. Therefore, when the fundamental wave (1−r) ^1/2 V ₀ cosωt of the first term is input, −β ₂ (1−r) ^3/2 V ₀ ³ cos 3ωt having the opposite phase to the fundamental wave is added. Will be. Therefore, the output signal of the amplifier is −β ₁ (1−r)
V ₀ ² cos 2ωt−β ₂ (1−r) ^3/2 A harmonic component of V ₀ ³ cos 3ωt is added.

On the other hand, since the harmonic components of the second and third terms input by the equation (25) are also input to the amplifier, the components are also amplified and output. The component α ₀ [α
₁ (r−r ₂ ) ^1/2 (r ₂ ^1/2 k ₁ V ₀ ) ² cos2ωt + α ₂ (r
−r ₂ ) ^1/2 (r ₂ ^1/2 k ₂ V ₀ ) ³ cos3ωt]
The second and third harmonic components newly generated by the amplifier according to the terms have the same frequency and different signs. Here, α ₀ is the coefficient of the first power term of the input / output characteristics of the amplifier. Therefore, the branching ratios r and r ₂ , the constants k _{1 and} k _2, or the coefficients α ₁ and α ₂ corresponding to the squared and cubed coefficients of the input / output characteristics.
If they are adjusted, they can cancel each other out. Therefore, the second and third order distortions of the amplifier are corrected simultaneously.

In the above description, it has been described that the third-order distortion is not generated from the second-order distortion generation circuit 200. However, when nonlinear distortion is generated by exponential function characteristics of a diode or the like, the second-order distortion is generated. Is generated, third-order distortion is also added. Therefore, the third-order distortion generating circuit 300 is a correction circuit including the third-order distortion. Specifically, adjustment may be made so that the third harmonic generated by the second distortion generation circuit 200 with respect to the fundamental wave of an arbitrary frequency is corrected by the third harmonic generated by the third distortion generation circuit 300. Specifically, (2
The third harmonic generated by the second distortion generating circuit may be added to the term of the third harmonic in the equation (4).

A characteristic in which the amplifier is inputted in a state where the bias is lower than the middle point, and the positive period of the fundamental wave of the output signal is extended, the negative period is compressed, and the entire signal is compressed;
That is, in the case of an amplifier to which a second harmonic having an in-phase relationship and a third harmonic having an anti-phase relationship are added to the fundamental wave, the diode 2 shown in FIG.
The same effect can be obtained by connecting and using 10 in the forward direction.

As described above, by disposing the negative-phase directional branching transformer in the forward direction with respect to the flow of the fundamental signal on the transmission line, the second-order distortion and the third-order distortion can be efficiently and simultaneously corrected. be able to. Therefore, a distortion correction device with high correction efficiency can be obtained.

(Modifications) Although one embodiment of the present invention has been described above, various other modifications are possible. For example, in the above embodiment, the phase relationship between the input terminal or output terminal of the directional branch transformer 20 and the branch terminal is reversed, but the present invention is not limited to this. For example, an in-phase type directional branch transformer may be used.

In the case of an in-phase type directional branching transformer, if the terminating resistor terminal is used as a signal source, the phase of the signal is inverted and output from the output terminal. Therefore, if the phase of the voltage applied to the nonlinear resistance means can be inverted with respect to the in-phase type, the third-order distortion generation circuit 300 can be used to output the third-order distortion of the same phase with respect to the fundamental wave at the output terminal. Can be superimposed. This condition is, as described above, that the adjustment resistor R ₁ is larger than the characteristic impedance R.

Regarding the secondary distortion, even if the phase of the voltage applied to the non-linear resistance means is inverted, the phase of the generated secondary distortion is not inverted. Therefore, it is necessary to invert the phase of the generated secondary distortion. Therefore, if the phase relationship of the occurrence of distortion in the amplifier is unchanged in the above description, the direction in which the bias is applied may be reversed, that is, the diode may be used in the opposite direction. That is, when the first embodiment is an in-phase type directional branch transformer, the configuration of the secondary distortion generating circuit 200 may be the configuration shown in FIG.

In the above embodiment, the distortion correction device of the present invention is connected to the input stage of the amplifier. However, the distortion correction device is connected to the output stage to correct harmonic distortion such as second and third order distortion caused by the amplifier. You can also. Further, one diode in the figure may be replaced by a plurality of series-connected or parallel-connected diodes. In short, a plurality of diodes can be connected in series in the same direction and replaced with one diode. The same applies to each resistor.

Further, the second-order distortion generating circuit 200 in the first embodiment is an example, and the circuits shown in FIGS. 11A and 11B can be applied. R1 and R3 are for distortion adjustment.
R3 is one element for determining the constant k described above, and R1 is for adjusting the bias current of the diode. C1, C2
Is a DC blocking capacitor, and L1 is an AC blocking coil. Further, the third-order distortion generating circuit 300 in the second embodiment
This is also an example, and the circuit shown in FIG. L1 is an AC blocking coil, C1, C2, C
Reference numerals 3 and C4 denote DC blocking capacitors, and the amount of distortion is adjusted by R1 and R3.

In the third embodiment, the second and third-order distortion generators are connected in parallel. However, as shown in FIG. 12, the second-order distortion generator 200 and the third-order distortion generator are connected to each other. Even if the circuit 300 is connected in series, the second-order distortion and the third-order distortion can be similarly corrected. 13A and 13B can also be applied to the series-connected circuit. The diodes 310 and 320 are biased by the voltage applied to the Bias1 terminal, and a third harmonic is added. Further, the diode 210 is biased by the voltage applied to the Bias2 terminal, and the second harmonic is similarly added. 13 (a) and 13 (b) are added because the direction of the diode 210 is different.
The sign of the second harmonic is different. In addition, C21, C2
Reference numerals 2, C23 and C24 are DC blocking capacitors. The adjustment of the distortion amount is adjusted by R12, R21, R22, and R23.

Also, by connecting a resistor, a parallel circuit of a resistor and a capacitor, or an impedance circuit composed of a resistor, a capacitor and a coil in series with the distortion generating circuit,
Impedance matching or phase correction can be performed. Further, in the second-order distortion generating circuit 200 or the third-order distortion generating circuit 300 of the above embodiment, the Schottky diodes 310 and 320 having a small forward voltage and a high response speed are used in order to apply to the CATV signal. , Other diodes may be used. Also, a distortion generator was constructed using the nonlinearity of the diode.
If the distortion of the amplifier is canceled, the distortion generator may be constituted by a transistor instead of a diode. Further, a passive network for correcting phase and amplitude characteristics may be provided in the branch line or the transmission line.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a distortion correction device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a directional branch transformer according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a distortion generating circuit according to the first embodiment of the present invention.

FIG. 4 is a current-voltage characteristic diagram of the diode according to the first embodiment of the present invention.

FIG. 5 is a circuit diagram of a distortion generating circuit according to the first embodiment of the present invention.

FIG. 6 is a configuration block diagram of a distortion correction device according to a second embodiment of the present invention.

FIG. 7 is a distortion generation circuit diagram according to a second embodiment of the present invention.

FIG. 8 is a characteristic diagram showing operation characteristics of the distortion generation circuit according to the second embodiment.

FIG. 9 is a configuration block diagram of a distortion correction device according to a third embodiment of the present invention.

FIG. 10 is a circuit diagram of a distortion generating circuit according to a third embodiment of the present invention.

FIG. 11 is a distortion generation circuit diagram showing various modifications of the distortion generation circuit.

FIG. 12 is another distortion generating circuit diagram used in the third embodiment of the present invention.

FIG. 13 is another distortion generating circuit diagram used in the third embodiment of the present invention.

FIG. 14 is an explanatory diagram illustrating a distortion correction method according to the present invention.

FIG. 15 is a configuration diagram of a directional branch transformer according to the present invention.

FIG. 16 is a diagram illustrating an example of waveform distortion caused by an amplifier.

FIG. 17 is a current-voltage characteristic diagram of an amplifier.

[Explanation of symbols]

 11, 20 directional branch transformer 11a distortion generator 50 amplifier 60 transmission line 200 secondary distortion generator 210 Schottky diode 220 bias circuit 240 bypass circuit 300 tertiary distortion generator 310, 320 ... Schottky diode 330 ... Bias circuit 340 ... Bypass circuit

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Akira Kitagawa Inventor 1-20-20 Himegaoka, Kani-shi, Gifu F-term in the Kani factory of Aichi Denki Co., Ltd. CA21 CA27 CA98 FA19 FA20 GN02 GN04 HA19 HA25 HA29 HA33 HA35 KA12 KA68 SA14 TA02 TA06 5K046 AA02 BB03 CC03 KK11

Claims (6)

[Claims] 1. A distortion correction device using a directional coupler comprising a transformer and a terminating resistor, wherein an adjusting resistor is connected to a branch terminal of the directional coupler, and the terminating resistance of the directional coupler is nonlinear. A harmonic is generated by applying a part of a signal to the non-linear resistance means, the harmonic is output from an output terminal, and the input / output characteristic of the directional coupler is changed to the input of the amplifier. A distortion correction device characterized in that the output characteristic is a constant multiple of a substantially inverse function of an output characteristic. 2. A distortion correcting apparatus using a directional coupler comprising a transformer and a terminating resistor, wherein an adjusting resistor is connected to a branch terminal of the directional coupler, and the terminating resistance of the directional coupler is nonlinear. A resistance means, a harmonic is generated by applying a part of the signal to the nonlinear resistance means, and the harmonic is output from an output terminal. At the output terminal of the directional coupler, the harmonic is A distortion correction apparatus characterized in that the distortion correction apparatus superimposes the phase of the harmonic by the amplifier in a phase relationship opposite to that of the harmonic so as to be canceled by the harmonic generated by the amplifier. 3. The distortion correction device according to claim 1, wherein the non-linear resistance means is a secondary distortion generating circuit that generates secondary distortion. 4. The distortion correcting device according to claim 1, wherein said nonlinear resistance means is a third-order distortion generating circuit for generating third-order distortion. 5. The distortion correction device according to claim 1, wherein the nonlinear resistance means is a harmonic distortion generation circuit that generates a second-order distortion and a third-order distortion at the same time. 6. The distortion correcting apparatus according to claim 1, wherein said nonlinear resistance means has an adjusting means for adjusting a distortion amount of the generated nonlinear distortion.