JP4896609B2 - Feed forward amplifier - Google Patents

Description

  The present invention relates to a feedforward amplifier, and more particularly to shortening the group delay time of a main amplifier and an error amplifier.

  With the rapid development of communication in recent years, the effective use of frequencies has been demanded, and OFDM and CDMA modulation capable of increasing the amount of information transmission per unit frequency have been actively used. In these modulated waves, the instantaneous power with respect to the average power of the signal is very large, and the amplifier is required to satisfy both low distortion characteristics and high efficiency characteristics over a wide power range.

  There is a distortion compensation technique as a method for realizing low distortion characteristics while satisfying high efficiency characteristics. The distortion compensation technique is a technique for reducing generated distortion by an external circuit, and one of them is a feedforward method.

  The feed-forward method is a method of reducing distortion by extracting distortion components of an amplifier and synthesizing them with an antiphase on the output side. Since a large distortion compensation amount can be obtained, it is applied to an amplifier for a base station that requires extremely low distortion characteristics. However, a delay line having a large loss is required on the output side of the amplifier, and the power efficiency is not high. Therefore, the efficiency of the feedforward amplifier has been improved by the following method.

  As Conventional Example 1, a low distortion amplifier is placed on the delay line side of the distortion extraction loop to lower the gain required for the auxiliary amplifier, and the group delay amount of the auxiliary cap and the delay line is reduced. There is one that can reduce the passage loss of the line and reduce the power consumption of the main amplifier (see, for example, Patent Document 1).

  Further, as conventional example 2, by moving an isolator for stabilizing the operation of the main amplifier after the directional coupler, the delay in the delay line can be set to be smaller than that of the conventional one, and low for harmonic removal and the like. By moving the band-pass filter before the directional coupler, the delay can be further shortened, and as a result, the delay loss of the delay line can be reduced and the power consumption of the main amplifier can be reduced (for example, patents). Reference 2).

  In addition, as a conventional example 3, the amplifier is operated with high efficiency by connecting a series resonant circuit or a parallel resonant circuit to the output side of the amplifier, and shorted at 2, 4, 6 times the operating frequency, and opened at 3, 5 times. There is one that improves the efficiency of the feedforward amplifier by applying impedance to the main amplifier and error amplifier of the feedforward amplifier (see, for example, Non-Patent Document 1).

  In addition, as a conventional example 4, the signal line has a structure in which a line acting as an inductor and a capacitor are connected in cascade, and the inductor is connected in parallel to the signal line, and is applied to a delay line of a feedforward amplifier. In some cases, a large group delay time is generated and the loss of the delay line is reduced to improve the efficiency of the feedforward amplifier (see, for example, Non-Patent Document 2).

  Further, as a conventional example 5, two parallel resonant circuits composed of a capacitor and an inductor are connected to the signal line in cascade with respect to the signal line, and are made to resonate in the vicinity of a desired frequency, so that the main amplifier of the feedforward amplifier By applying this to a bias circuit or the like, the leakage of the fundamental wave to the bias circuit or the like is suppressed, and the efficiency of the main amplifier is increased, thereby improving the efficiency of the feedforward amplifier (for example, Non-Patent Document 3).

JP-A-11-112241 JP 2000-252759 A Aikawa, Honjo, “Proposal of fully lumped constant class F amplifier circuit”, 2004 IEICE General Conference C-2-37 Okubo, Takai, Yamane, Tsutsumi, “A Study on Left-Handed Transmission Lines”, 2004 IEICE General Conference C-2-97 Kazuhiko Honjo, “Introduction to Ultra-High Frequency Electronics”, Nikkan Kogyo Shimbun

  By the way, in the above-described conventional example 1, a low distortion amplifier is provided on the delay line side of the distortion extraction loop to reduce the gain required for the auxiliary amplifier. Thereby, the group delay time of the auxiliary amplifier is reduced, and the group delay amount of the delay line is reduced.

  However, since the input signal of the auxiliary amplifier is a distortion component of the main amplifier extracted by the distortion extraction loop, in order to increase the input power of the auxiliary amplifier, the power of the signal distributed from the main amplifier must also be increased. Increasing the distributed power is equivalent to increasing the loss on the output side of the main amplifier. As a result, there is a trade-off relationship between the gain of the auxiliary amplifier and the distribution amount from the main amplifier, and there is a limit in reducing the group delay amount of the delay line.

  Further, in Conventional Example 2, the delay in the delay line is reduced by moving the isolator after the directional coupler and moving the low-pass filter before the directional coupler. However, there is a problem that the total group delay amount including the low-pass filter and the isolator does not change, and the substantial group delay time cannot be shortened.

  Further, in Conventional Example 3, a parallel resonant circuit or a series resonant circuit is placed after the amplifier to reflect harmonics such as the second harmonic and the third harmonic generated by the amplifier, and the fundamental waveform is changed to a rectangular wave. High efficiency operation is achieved by moving closer. In order to reflect harmonics, the resonance frequency of these resonance circuits is set to other than the fundamental wave. In addition, these circuits are connected to the output side of the amplifier, and in order to prevent loss and decrease in efficiency, the circuit is composed only of reactance elements.

  Further, in the conventional example 4, a line that acts as an inductor and a capacitor are cascade-connected to the signal line, and a series resonance circuit is configured. For this reason, the generated group delay time is positive.

  Furthermore, in Conventional Example 5, a parallel resonant circuit composed of a capacitor and an inductor is cascaded to the signal line. Further, by resonating in the vicinity of a desired frequency, the impedance is increased and a loss is given to the signal passing through the parallel resonance circuit.

  The present invention has been made in view of the above-described points, and an object thereof is to obtain a feedforward amplifier capable of realizing a reduction in group delay time of a main amplifier and an error amplifier.

In the feedforward amplifier according to the present invention, a circuit or an element having a negative group delay time is placed in front of or behind at least one of a main amplifier constituting a distortion extraction unit and an error amplifier constituting a distortion cancellation unit, As a circuit having a group delay time, a circuit having a negative group delay time in which a parallel resonant circuit using a capacitor, an inductor and a resistor is cascaded to a signal line and resonates in the vicinity of a desired frequency , and a capacitor A series resonant circuit using an inductor and a resistor is connected in parallel to the signal line, and a circuit having a negative group delay time that resonates in the vicinity of a desired frequency is used. Two are connected in a T shape, and the resistance Rs at the resonance frequency of the series resonance circuit and the resonance frequency of the parallel resonance circuit are When the resistance Rp is the characteristic impedance Zo, the relationship of Rp × Rp + 2 × Rs × Rp = Zo × Zo is generally satisfied, and a plurality of circuits having a negative group delay time are connected in cascade to reduce the negative group delay time. A negative group in which a plurality of circuits are connected in cascade, with amplifiers that compensate for the loss of the circuit set in the circuit having a negative group delay time, the resonance frequencies of the circuits having different frequency settings, respectively In a circuit having a delay time, the negative group delay time generated in circuits other than both ends of the frequency band is made closer to 0 nsec than the negative group delay time generated in circuits at both ends of the frequency band .
Also, the feedforward amplifier according to the present invention includes a circuit or element having a negative group delay time before or after at least one of the main amplifier constituting the distortion extraction unit and the error amplifier constituting the distortion cancellation unit. As a circuit having a negative group delay time, a circuit having a negative group delay time in which a parallel resonant circuit using a capacitor, an inductor and a resistor is connected in cascade to a signal line and resonates in the vicinity of a desired frequency, In addition, a series resonant circuit using a capacitor, an inductor, and a resistor is connected in parallel to the signal line, and a circuit having a negative group delay time that resonates near a desired frequency is used to resonate in parallel with two of the series resonant circuits. One of the circuits is connected in a π-shape, and the resistance Rs at the resonance frequency of the series resonance circuit and the resonance frequency of the parallel resonance circuit When the resistance component Rp is the characteristic impedance Zo, the relation of 2 × Zo × Zo × Rs + Zo × Zo × Rp = Rp × Rs × Rs is generally satisfied, and a plurality of circuits having negative group delay times are connected in cascade. The resonance frequency of the circuit having the negative group delay time is set to a different frequency, and in the circuit having the negative group delay time, an amplifier that compensates for the loss of the circuit is arranged before or after or between the stages. In a circuit having a negative group delay time in cascade connection, the negative group delay time generated in circuits other than both ends of the frequency band is closer to 0 nsec than the negative group delay time generated in the circuits at both ends of the frequency band. It is characterized by.

  According to the present invention, a circuit or an element having a negative group delay time is placed before or after at least one of the main amplifier constituting the distortion extracting unit or the error amplifier constituting the distortion canceling unit, thereby providing the main amplifier. In addition, the group delay time of the error amplifier can be shortened.

Embodiment 1 FIG.
1 is a configuration diagram of a feedforward amplifier according to Embodiment 1 of the present invention.
The feedforward amplifier shown in FIG. 1 is an amplifier to which a distortion compensation method for reducing distortion by extracting distortion components generated in the main amplifier 4 and synthesizing them in the opposite phase on the output side. This feed-forward amplifier is composed of a distortion extraction loop and a distortion elimination loop. The distortion extraction loop is composed of a main amplifier 4 and a first delay line 5, and the distortion elimination loop is a second delay line 3 and a negative group. A circuit 1 having a delay time and an error amplifier 2 are included. In addition, 6 is an input terminal and 7 is an output terminal.

Next, the operation in the first embodiment will be described.
A signal input from the input terminal 6 is distributed to the main line and the sub line. The signal on the main line is amplified by the main amplifier 4 and divided again into the main line and the sub line. On the other hand, the sub-line signal input from the input terminal 6 and distributed is given a group delay characteristic by the first delay line 5, and then has an opposite phase to the sub-line signal distributed on the output side of the main amplifier 4. And the distortion component of the main amplifier 4 is extracted. The extracted distortion component is given a negative group delay time by the circuit 1 having negative group delay characteristics, and then amplified by the error amplifier 2 so as to have the same amplitude as the distortion component of the main line. In the distortion elimination loop, this signal is synthesized with an antiphase on the output side of the main amplifier 4 and guided to the output terminal 7.

  In the feedforward amplifier, in order to secure a necessary band, the group delay times of the main amplifier 4 and the first delay line 5 are matched, and the group delay times of the error amplifier 2 and the second delay line 3 are matched. There is a need. That is, it is necessary to use a delay line having a larger group delay time as the group delay time of the main amplifier 4 and the error amplifier 2 is larger. In order to obtain a large group delay time, the line length of the delay line must be increased, and there is a problem that the loss increases. In particular, since the second delay line 3 is connected to the output side of the main amplifier 4, the reduction of the loss is a very important issue for improving the efficiency of the feedforward amplifier. Therefore, it is necessary to reduce the group delay time of the error amplifier 2 and the main amplifier 4.

  Therefore, in the first embodiment, a circuit or an element having a negative group delay time is placed before or after at least one of the main amplifier 4 or the error amplifier 2 so that the main amplifier 4 and the error amplifier 2 are equivalently provided. The group delay time is reduced.

  Here, in order to generate a negative group delay time, it is necessary to generate a characteristic that the passing phase advances with an increase in frequency. However, in conventional components such as lines, filters, and amplifiers, the frequency generally increases. On the other hand, the passing phase has a characteristic of being delayed, and the group delay time is a positive value. In the present invention, by using the circuit shown in the second embodiment, the phase advance characteristic is realized, and a negative group delay time is generated. Thereby, the group delay time of the delay line can be shortened, and the efficiency of the feedforward amplifier can be increased.

Embodiment 2. FIG.
FIG. 2 is a diagram showing a configuration of a circuit having a negative group delay time in the second embodiment of the present invention.
As a circuit having a negative group delay time, at least one series resonant circuit 8 shown in FIG. 2A or parallel resonant circuit 9 shown in FIG. 2B is used.
That is, the series resonance circuit shown in FIG. 2A is composed of a capacitor Cs, an inductor Ls, and a resistor Rs, and is a circuit that is connected in parallel to the signal line and resonates in the vicinity of a desired frequency. The parallel resonant circuit shown in FIG. 2B is composed of a capacitor Cp, an inductor Lp, and a resistor Rp, and is a circuit that is cascade-connected to a signal line and resonates in the vicinity of a desired frequency.

The operation in the second embodiment will be described.
In order to show the operation of the second embodiment, the calculation results obtained by calculating the group delay characteristics (GD: Group Delay) and the reflection characteristics (S11, S22) of the circuits of FIGS. 2A and 2B are shown in FIG. Shown in (A) and (B), respectively. 3A shows the results of Cs = 1 pF, Ls = 101.3 nH, Rs = 37.5Ω, and FIG. 3B shows Cp = 100 pF, Lp = 1.01 nH, Rp = 25Ω. This is the result. As shown in FIGS. 3A and 3B, it can be seen that a negative group delay time is obtained in the vicinity of the resonance frequency of 500 MHz.

  In order to confirm that a negative group delay time actually occurs, a circuit in which the circuits of FIGS. 2A and 2B described in Embodiment 2 are combined was prototyped. A prototype circuit is shown in FIG. In FIG. 4, Ls = Lp = 8.9 nH is used as the inductor, Cp = Cs = 10 pF is used as the capacitor, and the parasitic resistance of the inductor and the capacitor is used as the resistor. FIG. 5 shows the measured group delay time. As shown in FIG. 5, it can be confirmed that a negative group delay time of −2.2 nsec occurs at a frequency of 550 MHz.

  Thereby, the delay line can be shortened and the efficiency of the feedforward amplifier can be increased. In FIGS. 2A and 2B, a resistor is used, but the loss of the capacitor and the inductor may be substituted for the resistor.

  In addition to the circuit having the negative group delay time shown in FIGS. 2A and 2B, an element such as ferrite can be used as an element having characteristics equivalent to those of these circuits.

Embodiment 3 FIG.
FIG. 6 is a diagram showing a configuration of a circuit having a negative group delay time according to the third embodiment of the present invention.
The circuit having the negative group delay time shown in FIG. 6 is configured by connecting one series resonance circuit shown in FIG. 2A and two parallel resonance circuits shown in FIG. 2B in a T shape. At this time, the resistance component Rs at the resonance frequency of the series resonance circuit and the resistance component Rp at the resonance frequency of the parallel resonance circuit generally satisfy the relationship of Rp × Rp + 2 × Rs × Rp = Zo × Zo. Here, Zo is a characteristic impedance.

The operation in the third embodiment will be described.
In order to show the operation in the third embodiment, FIG. 7 shows calculation results obtained by calculating the group delay characteristic and the reflection characteristic of the circuit of FIG. FIG. 7 shows the results when Cp = 100 pF, Lp = 1.01 nH, Rp = 25Ω, Cs = 1 pF, Ls = 101.3 nH, and Rs = 37.5Ω. As shown in FIG. 7, it can be seen that a negative group delay time is obtained in the vicinity of the resonance frequency of 500 MHz, and that the reflection characteristics are improved as compared with the case of the second embodiment.

  As a result, it is possible to improve the efficiency of the feedforward amplifier while suppressing the influence on other components constituting the feedforward amplifier due to multiple reflection.

  A circuit was prototyped to confirm that a negative group delay time actually occurred by the circuit of FIG. 6 shown in the third embodiment. A prototype circuit is shown in FIG. In the prototyped circuit shown in FIG. 8, circuits having a negative group delay time are connected in cascade, and the resonance frequencies of the circuits are set to different values to broaden the frequency at which the negative group delay time can be obtained. An amplifier 11 that compensates for the circuit loss is arranged between the stages.

  The calculation results obtained by calculating the group delay characteristics and reflection characteristics of the circuit shown in FIG. 8 are shown in FIGS. In the group delay characteristic shown in FIG. 9, it can be confirmed that a negative group delay time of −7.4 nsec occurs at a frequency of 495 MHz. Moreover, in the reflection characteristic shown in FIG. 10, it can confirm that the favorable reflection characteristic below reflection-15 dB is obtained in the frequency vicinity of 495 MHz.

  In order to confirm that the delay line of the feedforward amplifier is shortened by using this circuit, the prototype circuit was placed in front of the error amplifier of the feedforward amplifier. FIG. 11 shows a measurement result of distortion characteristics of a feedforward amplifier to which an OFDM modulated wave is input. Regardless of the presence or absence of a circuit having a negative group delay time, almost the same distortion characteristics are obtained, and it can be confirmed that the feedforward amplifier operates normally in any state.

  At this time, the group delay time of the delay line of the feedforward amplifier is 22 nsec when there is no circuit having a negative group delay time, but the group delay time is shortened to 17.5 nsec by using this circuit. It was possible to reduce the length of the delay line by 1.4 m. By shortening the delay line, the delay line loss can be reduced from 1.7 dB to 1.3 dB, and the efficiency of the feedforward amplifier can be improved from 5% to 5.5%. In addition, by shortening the delay line, it was possible to improve equipment (line routing) and downsize the device.

Embodiment 4 FIG.
FIG. 12 is a diagram showing a configuration of a circuit having a negative group delay time in the fourth embodiment of the present invention.
The circuit having a negative group delay time shown in FIG. 12 is configured by connecting two series resonant circuits shown in FIG. 2A and one parallel resonant circuit shown in FIG. 2B in a π-shape. At this time, the resistance component Rs at the resonance frequency of the series resonance circuit and the resistance component Rp at the resonance frequency of the parallel resonance circuit generally satisfy the relationship of 2 × Zo × Zo × Rs + Zo × Zo × Rp = Rp × Rs × Rs. Yes. Here, Zo is a characteristic impedance.

The operation in the fourth embodiment will be described.
FIG. 13 shows the calculation results of calculating the group delay characteristics and reflection characteristics of the circuit shown in FIG. 12 in order to show the operation of the fourth embodiment. FIG. 13 shows the results when Cp = 100 pF, Lp = 1.0 nH, Rp = 37.5Ω, Cs = 1 pF, Ls = 101.3 nH, and Rs = 150Ω. As shown in FIG. 13, it can be seen that a negative group delay time is obtained in the vicinity of the resonance frequency of 500 MHz, and that the reflection characteristics are improved as compared with the case of the second embodiment.

  As a result, it is possible to improve the efficiency of the feedforward amplifier while suppressing the influence on other components constituting the feedforward amplifier due to multiple reflection.

Embodiment 5 FIG.
FIG. 14 shows a configuration of a circuit having a negative group delay time according to the fifth embodiment of the present invention.
The basic configuration and operation of the circuit having the negative group delay time in the fifth embodiment shown in FIG. 14 are the same as those in the third embodiment shown in FIG. The difference is that a circuit in which a capacitor Csp is connected in series is used. A larger negative group delay time can be obtained by connecting the capacitor Csp in series with the inductor Lp.

  In order to confirm this, FIG. 15 shows the calculation result of calculating the group delay characteristic with respect to the presence or absence of the capacitor Csp. FIG. 15 shows the results when Cp = 100 pF, Lp = 2.02 nH, Rp = 25Ω, Csp = 100 pF, Cs = 1 pF, Ls = 101.3 nH, Rs = 37.5Ω when there is a capacitor. When there is no capacitor, the result is Cp = 100 pF, Lp = 1.01 nH, Rp = 25Ω, Cs = 1 pF, Ls = 101.3 nH, Rs = 37.5Ω. As shown in FIG. 15, it can be seen that a larger negative group delay time can be obtained by connecting the capacitor Csp in series with the inductor Lp (in the figure, if present). Thereby, the delay line can be further shortened, and the efficiency of the feedforward amplifier can be improved.

  In the second and fourth embodiments, a capacitor may be connected in series to the inductor, as in the case of the fifth embodiment. In FIG. 14, the capacitor is connected in series only to the inductor of the parallel resonance circuit, but the capacitor may be connected to the inductor of the series resonance circuit.

Embodiment 6 FIG.
FIG. 16 is a diagram showing a configuration of a circuit having a negative group delay time according to the sixth embodiment of the present invention.
The basic configuration and operation of the circuit having the negative group delay time in the sixth embodiment shown in FIG. 16 are the same as those in the third embodiment shown in FIG. 6, but the series resonant circuit and the parallel resonant circuit are configured. The difference is that a line such as a microstrip line or a coaxial line is used for the inductor. By using the line, the inductor can be finely adjusted, and the setting accuracy of the resonance frequency can be increased. Thereby, loss flatness and group delay time deviation of a circuit having a negative group delay time in the band can be suppressed, and the distortion compensation amount of the feedforward amplifier can be increased.

  Even in the case of the second and fourth embodiments, a line such as a microstrip line or a coaxial line may be used as in the case of the sixth embodiment.

Embodiment 7 FIG.
FIG. 17 is a diagram showing a configuration of a circuit having a negative group delay time according to the seventh embodiment of the present invention. FIG. 17 shows an RF equivalent circuit.
The basic configuration and operation of the seventh embodiment shown in FIG. 17 are the same as those of the third embodiment shown in FIG. 6, but a reverse-biased variable as a capacitor constituting the series resonant circuit and the parallel resonant circuit. The difference is that a capacitive diode is used. By using the variable capacitance diode, the resonance frequency can be finely adjusted, and loss flatness and group delay time deviation within a band of a circuit having a negative group delay time can be suppressed. Thereby, the amount of distortion compensation of the feedforward amplifier can be increased.

  In the second and fourth embodiments, a variable capacitance diode may be used as in the case of the seventh embodiment.

Embodiment 8 FIG.
FIG. 18 shows a structure of a circuit having a negative group delay time according to the eighth embodiment of the present invention. In the figure, reference numeral 10 denotes a circuit having a negative group delay time according to the third embodiment.

  The basic configuration and operation of the eighth embodiment shown in FIG. 18 are the same as those of the third embodiment shown in FIG. 6, except that a plurality of stages of the circuits of the third embodiment are connected in cascade. Different. By using multiple stages, a large negative group delay time can be obtained.

  In order to confirm this, FIG. 19 shows the calculation result obtained by calculating the group delay characteristics of the two-stage circuit. As shown in FIG. 19, it can be seen that a larger group delay time than in the case of one stage can be obtained by making the number of stages (two stages). Thereby, the delay line can be further shortened, and the efficiency of the feedforward amplifier can be improved.

  In addition, the adjacent series resonance circuit and parallel resonance circuit of FIG. 18 may be integrated, and may be comprised by one resonance circuit as shown in FIG.20 and FIG.21. Thereby, the circuit can be miniaturized.

  Even in the second and fourth embodiments, the number of stages may be increased as in the case of the seventh embodiment.

Embodiment 9 FIG.
The basic configuration and operation of the ninth embodiment are the same as those of the eighth embodiment shown in FIG. 18, but the resonance frequencies of the circuits having negative group delay times connected in cascade are set to different frequencies. The point is different. By setting the resonance frequencies to different frequencies, it is possible to suppress loss flatness and group delay time deviation within a band of a circuit having a negative group delay time.

  In order to confirm this, FIG. 22 shows a calculation result of calculating the group delay characteristics of a circuit in which circuits having different resonance frequencies of 13% (resonance frequencies are 500 MHz and 470 MHz) are connected in cascade. As shown in FIG. 22, the negative group delay time is obtained over a wide frequency range by setting the resonance frequencies of the cascade-connected circuits having the negative group delay time to different frequencies. Recognize. As a result, the bandwidth of the feedforward amplifier can be increased.

  Even when the circuits of the second and fourth embodiments are multistaged, the resonance frequencies of the circuits may be set to different frequencies as in the case of the ninth embodiment.

Embodiment 10 FIG.
FIG. 23 shows a structure of a circuit having a negative group delay time in the tenth embodiment of the invention. In the figure, 11 is an amplifier.

  The basic configuration and operation of the tenth embodiment shown in FIG. 23 are the same as those of the eighth embodiment shown in FIG. 18, except that an amplifier 11 that compensates for the circuit loss is provided in front or behind. . By using the amplifier 11, the loss generated in the negative group delay circuit can be compensated. Thereby, the level change of the feedforward amplifier with respect to the presence or absence of the negative group delay circuit can be prevented.

  Even in the case of the second and fourth embodiments, the amplifier 11 that compensates for the circuit loss may be provided before or after, as in the case of the tenth embodiment.

Embodiment 11 FIG.
The basic configuration and operation of the eleventh embodiment are the same as those of the ninth embodiment, but the negative group delay time generated in circuits other than both ends of the frequency band is generated in the circuits at both ends of the frequency band. The difference is that it is closer to 0 nsec than the group delay time. By changing the negative group delay time generated in the band, the group delay time deviation in the band of the circuit having the negative group delay time can be suppressed.

  In order to confirm this, FIG. 24 shows the group delay characteristics of a circuit in which the negative group delay time generated in the circuits other than both ends of the band is closer to 0 nsec than the negative group delay time generated in the circuits at both ends of the band. In FIG. 24, for example, three circuits are provided as negatively connected circuit groups having negative group delay times, and the group delay characteristics P1 to P3 of these circuits and the total group delay characteristics Pm of these circuits are shown. As shown in FIG. 24, in a circuit other than both ends of the frequency band (a circuit having the group delay characteristic P1) from the negative group delay time generated by the circuits at both ends of the frequency band (the circuits having the group delay characteristics P2 and P3). It can be seen that by bringing the negative group delay time to be generated closer to 0 nsec, the total group delay characteristic Pm is flattened, and the group delay time deviation within the band of the circuit having the negative group delay time can be suppressed. As a result, the bandwidth of the feedforward amplifier can be increased.

  Even when the circuits of the second and fourth embodiments are multistaged, the negative group delay time of the circuit may be set to a different value as in the case of the eleventh embodiment.

Embodiment 12 FIG.
FIG. 25 shows a structure of a circuit having a negative group delay time according to the twelfth embodiment of the present invention. FIG. 25 shows an RF equivalent circuit.
The basic configuration and operation of the twelfth embodiment shown in FIG. 25 are the same as those of the third embodiment shown in FIG. 6, but an open stub formed of a microstrip line as a capacitor constituting the series resonant circuit. Is different.

  By using an open stub composed of a microstrip line as a capacitor constituting the series resonant circuit, it is not necessary to form a ground for grounding, and the circuit can be easily manufactured. This is particularly effective when the substrate thickness is thick or difficult, or when it is desired to reduce the cost of the substrate. Further, the resonant frequency can be finely adjusted by adjusting the length of the open stub, and loss flatness and group delay time deviation within the band of a circuit having a negative group delay time can be suppressed. As a result, the feedforward amplifier can be easily manufactured and the amount of distortion compensation can be increased.

It is a figure which shows the structure of the feedforward amplifier which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the circuit which has the negative group delay time in Embodiment 2 of this invention. It is a figure which shows the calculation result which calculated the group delay characteristic and reflection characteristic of the circuit shown to FIG. 2 (A) and FIG. 2 (B), respectively. FIG. 3 is a diagram showing a configuration of a prototype circuit in which the circuits of FIGS. 2A and 2B shown in the second embodiment are combined in order to confirm that a negative group delay time occurs. FIG. 5 is a diagram illustrating a calculation result obtained by calculating a group delay characteristic of the circuit illustrated in FIG. 4. It is a figure which shows the structure of the circuit which has the negative group delay time in Embodiment 3 of this invention. It is a figure which shows the calculation result which calculated the group delay characteristic and reflection characteristic of the circuit shown in FIG. It is a figure which shows the circuit made as an experiment in order to confirm that the negative group delay time actually generate | occur | produces with the circuit of FIG. It is a figure which shows the calculation result which calculated the group delay characteristic of the circuit shown in FIG. It is a figure which shows the calculation result which calculated the reflection characteristic of the circuit shown in FIG. It is a figure which shows the measurement result of the distortion characteristic of the feedforward amplifier which input the OFDM modulation wave. It is a figure which shows the structure of the circuit which has the negative group delay time in Embodiment 4 of this invention. It is a figure which shows the calculation result which calculated the group delay characteristic and reflection characteristic of the circuit shown in FIG. It is a figure which shows the structure of the circuit which has the negative group delay time in Embodiment 5 of this invention. It is a figure which shows the calculation result which calculated the group delay characteristic and reflection characteristic of the circuit shown in FIG. It is a figure which shows the structure of the circuit which has the negative group delay time in Embodiment 6 of this invention. It is a figure which shows the structure of the circuit which has the negative group delay time in Embodiment 7 of this invention. It is a figure which shows the structure of the circuit which has the negative group delay time in Embodiment 8 of this invention. It is a figure which shows the calculation result which calculated the group delay characteristic of the circuit shown in FIG. It is a figure which shows the structure of one resonance circuit which integrated and comprised the adjacent series resonance circuit and parallel resonance circuit of FIG. It is a figure which shows the structure different from FIG. 20 of one resonance circuit which integrated and comprised the adjacent series resonance circuit and parallel resonance circuit of FIG. It explains a circuit having a negative group delay time in Embodiment 9 of the present invention, and is a diagram showing a calculation result obtained by calculating a group delay characteristic of a circuit in which circuits having different resonance frequencies are connected in cascade. It is a figure which shows the structure of the circuit which has the negative group delay time in Embodiment 10 of this invention. FIG. 25 is a diagram for explaining a circuit having a negative group delay time in Embodiment 11 of the present invention, and showing a group delay characteristic of a circuit that is closer to 0 nsec than a negative group delay time generated by circuits at both ends of a band. It is a figure which shows the structure of the circuit which has the negative group delay time in Embodiment 12 of this invention.

Explanation of symbols

  1 circuit having negative group delay time 2 error amplifier 3 second delay line 4 main amplifier 5 first delay line 6 input terminal 7 output terminal 8 series resonance circuit 9 parallel resonance circuit 10 Circuit with negative group delay time, 11 Amplifier.

Claims (6)

A circuit or element having a negative group delay time is placed before or after at least one of the main amplifier constituting the distortion extraction unit or the error amplifier constituting the distortion cancellation unit,
As a circuit having the negative group delay time,
A circuit having a negative group delay time in which a parallel resonant circuit using a capacitor, an inductor and a resistor is cascaded to a signal line and resonates near a desired frequency , and
A series resonant circuit using a capacitor, an inductor and a resistor is connected in parallel to the signal line, and a circuit having a negative group delay time for resonating near a desired frequency is used.
One of the series resonant circuit and two of the parallel resonant circuits are connected in a T shape, and a resistance component Rs at the resonance frequency of the series resonance circuit and a resistance component Rp at the resonance frequency of the parallel resonance circuit are characteristic impedances. At the time of Zo, the relationship of Rp × Rp + 2 × Rs × Rp = Zo × Zo is generally satisfied,
Cascading a plurality of circuits having the negative group delay time,
The resonant frequency of the circuit having the negative group delay time is set to a different frequency, respectively.
In the circuit having the negative group delay time, an amplifier that compensates for the loss of the circuit is arranged before or after or between the stages,
In a circuit having a negative group delay time connected in cascade, a negative group delay time generated in a circuit other than both ends of the frequency band is made closer to 0 nsec than a negative group delay time generated in a circuit at both ends of the frequency band. A feedforward amplifier characterized by that. A circuit or element having a negative group delay time is placed before or after at least one of the main amplifier constituting the distortion extraction unit or the error amplifier constituting the distortion cancellation unit,
As a circuit having the negative group delay time,
A circuit having a negative group delay time in which a parallel resonant circuit using a capacitor, an inductor and a resistor is cascaded to a signal line and resonates near a desired frequency , and
A series resonant circuit using a capacitor, an inductor and a resistor is connected in parallel to the signal line, and a circuit having a negative group delay time for resonating near a desired frequency is used.
Two series resonance circuits and one of the parallel resonance circuits are connected in a π-shape, and a resistance component Rs at the resonance frequency of the series resonance circuit and a resistance component Rp at the resonance frequency of the parallel resonance circuit are characteristic impedances. At the time of Zo, the relationship of 2 × Zo × Zo × Rs + Zo × Zo × Rp = Rp × Rs × Rs is generally satisfied,
Cascading a plurality of circuits having the negative group delay time,
The resonant frequency of the circuit having the negative group delay time is set to a different frequency, respectively.
In the circuit having the negative group delay time, an amplifier that compensates for the loss of the circuit is arranged before or after or between the stages,
In a circuit having a negative group delay time connected in cascade, a negative group delay time generated in a circuit other than both ends of the frequency band is made closer to 0 nsec than a negative group delay time generated in a circuit at both ends of the frequency band. A feedforward amplifier characterized by that. The feedforward amplifier according to claim 1 or claim 2 ,
A feedforward amplifier characterized by using a circuit in which an inductor and a capacitor are connected in series as an inductor constituting the series resonant circuit or the parallel resonant circuit. The feedforward amplifier according to claim 1 or claim 2 ,
A feedforward amplifier, wherein a microstrip line or a coaxial line is used as an inductor constituting the series resonant circuit or the parallel resonant circuit. The feedforward amplifier according to claim 1 or claim 2 ,
A feedforward amplifier characterized in that a reverse-biased variable capacitance diode is used as a capacitor constituting the series resonant circuit or the parallel resonant circuit. The feedforward amplifier according to claim 1 or claim 2 ,
A feedforward amplifier characterized by comprising an open stub composed of a microstrip line as a capacitor constituting the series resonant circuit.

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