JPH09312526A - Feed-forward amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feed-forward amplifier providing a small amplifier part which has a wide-band and also low noise characteristic. SOLUTION: Variable phase equipments 10 and 14, preceding stage amplifiers 11 and 15, variable attenuators 12 and 16 and succeeding stage amplifiers 13 and 17 are connected in order so as to constitute the main amplifying part 20 and the auxiliary amplifying part 21 of the feed-forward amplifier and so that the increase of an output noise level is prevented. Inter stage matching in the preceding stage amplifiers and the succeeding stage amplifiers of the respective amplifying parts which are multi-stage-constituted in this way is adopted as low impedance matching using a distribution constant circuit so that wide band conversion is realized. A λ/4 transmitting line is used in the output side matching circuits of the succeeding stage amplifiers 13 and 17 and a transmission path which is electromagnetically connected to it is arranged in parallel so that power distributors 5 and 7 are integratedly formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a linear amplifier for simultaneously amplifying multi-frequency signals in a high frequency band,
The present invention relates to a feedforward amplifier that detects and removes non-linear distortion generated in a main amplification unit.

[0002]

2. Description of the Related Art This type of feedforward amplifier is
It is used as a power amplifier in a base station device for wireless communication. In most cases, a base station device for wireless communication simultaneously receives, amplifies and transmits multi-frequency signals. There is also a system for individually amplifying multi-frequency signals, but this system is disadvantageous in that it requires an amplifier, a distributor, a combiner, etc. for amplifying each signal, resulting in high cost and large scale of the device. . Then, what was devised as an amplifier which amplifies a multifrequency signal simultaneously is a feedforward amplifier.

FIG. 3 shows a circuit block diagram of a conventional feedforward amplifier. In FIG. 3, 101 is an input terminal, 102 is an output terminal, 103 and 104 are power distributors, 105 and 106 are power combiners, 107 and 1
10 is a variable phase shifter, 108 and 111 are variable attenuators,
109 is a main amplifier, 112 is an auxiliary amplifier, and 113 and 114 are delay circuits. A distortion detection loop is configured by the power divider 103, the variable phase shifter 107, the variable attenuator 108, the main amplifier 109, the power divider 104, the delay circuit 113, and the power combiner 106, which occupy the left side of FIG. The power divider 104, the power combiner 106, the variable phase shifter 110, the variable attenuator 111, the auxiliary amplifier 112, the delay circuit 114, and the power combiner 10 which also occupy the right side.
A distortion removing loop is constituted by 5.

First, the operation principle of the distortion detection loop will be described. The multi-frequency signal input from the input terminal 101 is distributed by the power distributor 103 in the distortion detection loop 120. One of the distributed signals is phase-adjusted by the variable phase shifter 107 and amplitude-adjusted by the variable attenuator 108, and then the main amplifier 1
It is amplified at 09. Non-linear distortion occurs during this amplification. The amplified multi-frequency signal is input to the power distributor 104, and one of the signals distributed here is input to the power combiner 106.

The other signal distributed by the power distributor 103 is passed through the delay circuit 113 and input to the power combiner 106. The power combiner 106 combines the two input signals and detects a distortion component. At this time, a part of the multi-frequency signal amplified by the main amplifier and taken out from the power distributor 104 and the multi-frequency signal passed through the delay circuit 113 are controlled to have the same amplitude and opposite phase.

Next, the operation principle of the distortion removal loop 121 will be described. The other signal amplified by the main amplifier 109 and distributed by the power distributor 104 is input to the power combiner 105 through the delay circuit 114. The distortion component detected by the distortion detection loop is phase-adjusted by the variable phase shifter 110, amplitude-adjusted by the variable attenuator 111, amplified by the auxiliary amplifier 112, and input to the power combiner 105. . A distortion component included in the multi-frequency signal input from the main amplifier 109 to the power combiner 105 via the delay circuit 114;
The distortion signal detected by the distortion detection loop and input to the power combiner 105 via the auxiliary amplifier 112 is controlled to have the same amplitude and opposite phase.

By the operations of the distortion detection loop and the distortion removal loop as described above, the distortion components included in the multi-frequency signal input to the power combiner 105 are canceled by the distortion signals having the same amplitude and the opposite phase, and the power combining is performed. The multi-frequency signal output from the device 105 has the non-linear distortion removed.

[0008]

However, the above-mentioned conventional feedforward amplifier has the following drawbacks. First, as the output power increases, the input / output impedance of the device used for the amplifier decreases, and the frequency characteristics of amplitude and phase become narrow band. Also,
As the gain of each amplifier increases, the output level of noise also increases. Furthermore, the number of parts is large.

The present invention has been made in order to solve the above-mentioned problems of the conventional feedforward amplifier, and it is an object of the present invention to provide a feedforward amplifier including an amplification unit having a small size, a wide band and a low noise characteristic. To aim.

[0010]

In a feedforward amplifier according to the present invention for achieving the above object, a main amplifying section and an auxiliary amplifying section are provided with a variable phase shifter for phase adjustment, a pre-stage amplifier, and a variable amplifier for amplitude adjustment, respectively. It is characterized in that the attenuator and the post-amplifier are sequentially connected in series. By providing the pre-stage amplifier in front of the variable attenuator, wide band and low noise characteristics can be obtained. Preferably, a distributed constant circuit is used for the interstage matching of the main amplifying unit and the auxiliary amplifying unit having a multi-stage configuration, and low impedance matching of 25Ω or less is performed to further realize a wider band.

Further, an impedance conversion circuit using a λ / 4 transmission line is used for the output side matching circuit of the post-amplifier constituting the main amplification unit and the auxiliary amplification unit, and another transmission line is connected in parallel with this λ / 4 transmission line. It is preferable that the power distributor is configured by arranging and electromagnetically coupling both transmission lines. In this way, by integrating the output matching circuits of the post-amplifiers of the main amplifying unit and the auxiliary amplifying unit and the power distributor, the miniaturization of the entire circuit is realized.

[0012]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. 1 is a circuit block diagram of a feedforward amplifier according to an embodiment of the present invention.
, 1 is an input terminal, 2 is an output terminal, 3, 5, 7,
8 is the first, second, third, and fourth power distributors, 4
Is a pilot signal injection circuit, 6 and 9 are first and second power combiners, 10 and 14 are first and second variable phase shifters, and 12 and 16 are first and second variable attenuators, respectively. , 11 and 15 are first and second pre-amplifiers 1 and 1, respectively.
3, 17 are first and second post-amplifiers 18, 18 respectively.
Reference numerals 9 are first and second delay circuits, respectively.

The first variable phase shifter 10, the first front-stage amplifier 11, the first variable attenuator 12, and the first rear-stage amplifier 13 constitute a main amplification section 20. Similarly, in the second variable phase shifter 14, the second front stage amplifier 15, the second variable attenuator 16, and the second rear stage amplifier 17, the auxiliary amplification unit 2 is used.
1 is configured.

The multi-frequency signal input from the input terminal 1 is
It is distributed by the first power distributor 3. After the pilot signal is injected by the pilot injection circuit 4, one of the distributed multi-frequency signals is subjected to phase adjustment, amplitude adjustment, and amplification in the main amplification section 20. The amplified multi-frequency signal contains non-linear distortion and is further distributed by the second power distributor 5.

The other multi-frequency signal distributed by the first power distributor 3 passes through the first delay circuit 18 and is input to the first power combiner. One of the multi-frequency signals distributed by the second power distributor 5 is also input to the first power combiner. These two input signals are combined by the first power combiner 6. At this time, the two input signals (multifrequency signals) are
It is controlled to have the same amplitude and opposite phase. As a result, a signal mainly including a distortion component is output from the power combiner 6.

The signal output from the power amplifier 6 is input to the auxiliary amplifying section 21 where phase adjustment, amplitude adjustment and amplification are performed. The amplified signal is supplied to the third power distributor 7
Is divided into a distortion removal signal and a power monitor signal, and the distortion removal signal is input to the second power combiner 9.

The other multi-frequency signal distributed by the second power distributor 5 is input to the second power combiner 9 through the second delay circuit 19 and distributed by the third power distributor 7. It is combined with the generated distortion removal signal. At this time, the two pilot signal components input to the second power combiner 9 are controlled so as to have the same amplitude and opposite phases. Therefore, in the signal output from the second power combiner 9, the distortion component generated in the main amplification unit 20 is canceled by the distortion removal signal.

The signal output from the second power combiner 9 is further input to the fourth power distributor 8 and distributed to the feedforward amplifier output signal and the pilot signal detection signal. The power monitor signal distributed by the third power distributor 7 and the pilot signal detection signal distributed by the fourth power distributor 8 are used as signals for controlling the amplitude or phase, respectively.

In the feedforward amplifier of this embodiment, the interstage matching between the pre-stage amplifier 11 and the post-stage amplifier 13 of the main amplifying section 20 and the pre-stage amplifier 15 of the auxiliary amplifying section 21 are performed.
With regard to the interstage matching of the post-stage amplifier 17, low impedance matching of 25Ω or less is realized by using a distributed constant circuit. As a result, it is possible to realize a wide band of the main amplifying unit 20 and the auxiliary amplifying unit 21 which are configured in multiple stages. Also,
The first variable attenuator 12 of the main amplifying section 20 is arranged between the first front-stage amplifier 11 and the first rear-stage amplifier 13, and similarly, the second variable attenuator 16 of the auxiliary amplifying section 21 is connected to the second variable attenuator 16. It is arranged between the second front-stage amplifier 15 and the second rear-stage amplifier 17. As a result, it is possible to prevent the noise figure of the main amplification section 20 and the auxiliary amplification section 21 from deteriorating and to realize a feedforward amplifier having a low noise characteristic.

Next, as a second embodiment, a pattern diagram of an integrated circuit of the output matching circuits of the post-stage amplifiers 13 and 17 and the power distributors 5 and 7 in the above embodiment is shown in FIG. In FIG. 2, 30 is an impedance converter using the first or third λ / 4 transmission line, and 31 is a second or fourth transmission line having electromagnetic coupling with the impedance converter 30.

The impedance converter 30 using the first or the third λ / 4 transmission line has the output impedance of the low-impedance matched rear-stage amplifiers 13 and 17 of 50Ω.
It has a role as an output matching circuit for converting to. Second or fourth λ / 4 transmission in which electromagnetic coupling is provided between the impedance converter 30 using the first or third λ / 4 transmission line and the impedance converter 30 arranged in parallel with the impedance converter 30. The line 31 constitutes the power distributors 5 and 7.

In this way, a circuit in which the output matching circuit of the post-stage amplifier 13 and the power distributor 5 or the output matching circuit of the post-stage amplifier 17 and the power distributor 7 are integrated can be constructed. As a result, miniaturization of the entire circuit is realized.
At this time, the characteristic impedance of the first or third λ / 4 transmission line 30 is set to Z = SQRT (post-stage amplifier output impedance × 50). However, "SQRT" represents a square root operation. Further, the characteristic impedance of the second or fourth transmission line 31 and the distance between the first or third λ / 4 transmission line 30 and the second or fourth transmission line 31 are determined based on the desired degree of coupling. To be done. The line length of the second or fourth transmission line is not limited to λ / 4.

[0023]

As described above, according to the feedforward amplifier of the present invention, a wide band frequency characteristic can be obtained in terms of amplitude and phase, and distortion detection and distortion removal can be performed with high accuracy. Moreover, miniaturization is realized by integrating the power converter with the impedance converter using the λ / 4 transmission line as the matching circuit.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a feedforward amplifier according to an embodiment of the present invention.

2 is a circuit pattern diagram in which an output matching circuit of a post-stage amplifier and a power distributor in the feedforward amplifier of FIG. 1 are integrated.

FIG. 3 is a circuit block diagram of a conventional feedforward amplifier.

[Explanation of symbols]

1 signal input terminal 2 signal output terminal 3,5,7,8 power distributor 4 pilot injection circuit 6,9 power combiner 10,14 variable phaser 11,15 pre-stage amplifier 12,16 variable attenuator 13,17 post-stage amplifier 18, 19 Delay Circuit 20 Main Amplifying Unit 21 Auxiliary Amplifying Unit 30 Impedance Converter with First or Third λ / 4 Transmission Line 31 Second or Fourth Transmission Line

Claims (3)

[Claims] 1. A signal input terminal is connected to a first power distributor, one output of this first power distributor is input to a main amplification section via a pilot signal injection circuit, and the other output is the first output. Is input to the first power combiner through the delay circuit, the output of the main amplification unit is input to the second power divider, and one output of the second power divider is input to the first power combiner. , The other output is input to the second power combiner via the second delay circuit, and the output of the first power combiner is input to the third power distributor via the auxiliary amplifier. One output of the third power distributor is a power monitor signal, the other output is input to the second power combiner, and the output of the second power combiner is input to the fourth power distributor. One output of the fourth power distributor is connected to the signal output terminal and the other output is the pilot A feedforward amplifier serving as a signal detection signal, wherein the main amplification section and the auxiliary amplification section are respectively a phase adjuster variable phaser, a pre-stage amplifier, and an amplitude adjuster variable attenuator,
A feed-forward amplifier, which is configured by serially connecting a second stage amplifier and a second stage amplifier. 2. A distributed constant circuit is used as an interstage matching circuit between a pre-stage amplifier and a post-stage amplifier which form the main amplifying unit and the auxiliary amplifying unit, and low impedance matching of 25Ω or less is realized. Feed-forward amplifier. 3. An impedance conversion circuit using a λ / 4 transmission line is used for an output side matching circuit of a post-stage amplifier which constitutes the main amplification unit and the auxiliary amplification unit, and another transmission line is parallel to the λ / 4 transmission line. The feed-forward amplifier according to claim 1 or 2, wherein the power distributor is configured by arranging and electromagnetically coupling both transmission lines.