JP2000244253A - Feed forward amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized feed forward amplifier with reduced power consumption. SOLUTION: An input signal from a port (a) is distributed into two by a power distributor 2, is power-amplified in a main amplifier 4 from a port (b) via a vector adjusting unit 3 and is delayed in a delay filter 6 from a port (c). Both signals are adjusted so that the distortion component of a target signal becomes equal in amplitude and opposite in phase in a distortion detection power synthesizer 5 and the signal of only the distortion component is outputted from the port (g) of the distortion detection power synthesizer 5. A signal component inputted from a port (e) is outputted from a port (f). The signal of only the distortion component, which is outputted from a port (g), is adjusted so that the phase becomes opposite to the distortion component of the input of a port (h) and amplitude becomes equal to it in an auxiliary amplifier 10. The distortion component is removed and only the target signal component is obtained from the port (j) of a distortion removal power synthesizer 8. A band pass filter 11 selects only the target signal component and it is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedforward amplifier used for a base station device of mobile communication equipment.

[0002]

2. Description of the Related Art In recent years, a transmitter for a base station of a mobile communication device requires an efficient and highly linear power amplifier to amplify a large number of signal channels at once. This is realized by performing distortion compensation by the forward method.

[0003] For a feed-forward amplifier, see, for example, John LB Walker, "High-Power GaAs FET Amp.
3 shows an example of the configuration of a conventional feedforward amplifier, which is also described in Artech House, 1993, pp. 332 to 333. In the figure, an input terminal 101 is connected to a port a of a power divider 102. , From the port b of the power distributor 102, via a vector adjuster 103, is connected to a main amplifier 104 for power amplifying an input signal.
The output of 04 is connected to the port d of the distortion detection power combiner 105. The port c of the power divider 102 is connected to the port e of the distortion detecting power combiner 105 via the delay circuit 106.

A port f of the distortion detecting power combiner 105 is connected to a port h of the distortion removing power combiner 108 via a delay circuit 107 and a port g of the distortion detecting power combiner 105.
Is connected to the port i of the distortion removing power combiner 108 through a series circuit of a vector adjuster 109 and an auxiliary amplifier 110. The output terminal 111 is connected from the port j of the distortion removal power combiner 108.

[0005] The operation of the feedforward amplifier thus configured will be described below. First, an input signal including a multi-channel component input from the input terminal 101 is split into two by a power splitter 102. One of the two divided output signals is adjusted in phase and amplitude by the vector adjuster 103 from port b, amplified by the main amplifier 104, and input to the port d of the distortion detection power combiner 105. At this time, due to the non-linearity of the main amplifier 104, a signal including a distortion component due to intermodulation between multi-channel signals in addition to the input signal component is input. The other signal divided into two is port c
, And is input to the port e of the distortion detection power combiner 105.

Here, the input signal components of the signals input to the ports d and e are set to have the same amplitude and opposite phases, respectively.
Vector adjuster 103 including variable attenuator and variable phase shifter
And adjusting the delay circuit 106, the port g
Outputs a signal of only the distortion component in which the input signal component is canceled, and the port f outputs the signal component input from the port e.

Next, the signal including the input signal component and the distortion component output from the port f is delayed by the delay circuit 107 and input to the port h of the distortion removal power combiner 108. The signal of the distortion component output from the port g is amplified by the auxiliary amplifier 110 via the vector adjuster 109, and is input to the port i of the distortion removal power combiner 108. Here, by adjusting the vector adjuster 109 and the delay circuit 107 so that the distortion components of the signals input to the port h and the port i have the same amplitude and opposite phases,
A signal consisting of only the input signal component from which the distortion component has been canceled is output from the port j to the output terminal 111.

FIGS. 4 (a) to 4 (d) show ports a,
4 shows the frequency spectrum of the signal at d, g and j.

[0009]

However, one of the problems with the above-mentioned conventional configuration is that the power consumption of the main amplifier 104 is large. In order to reduce the occurrence of distortion, the main amplifier 104 usually uses a class A amplifier, which has low distortion but low power efficiency and large loss. If a class AB amplifier is used to increase the efficiency, distortion increases, and intermodulation between the fundamental wave and distortion also occurs, causing distortion over a wide frequency range, and the feedforward method alone cannot sufficiently cancel. Happens.

As a second problem, the delay circuits 106, 1
The delay element used in 07 is, for example, a coaxial cable spirally wound, requires a cable length of about 3 m, requires a large space, and has a large passing power loss in the case of large power. There was a point.

The present invention solves such a conventional problem,
An object of the present invention is to provide a feedforward amplifier that requires less power consumption, requires less space for a delay element, and has less loss therein.

[0012]

According to a first aspect of the present invention, there is provided a feedforward amplifier comprising: a power divider for dividing an input signal into two parts; and a power divider for dividing the input signal into two parts. A first vector adjuster for adjusting the amplitude and phase of one of the output signals, a main amplifier for inputting the output of the first vector adjuster and amplifying the power, and the other output of the power splitter divided into two A first delay circuit for delaying a signal phase, a distortion detection power combiner for combining the output of the main amplifier and the output of the first delay circuit in opposite phases, and a distortion detection power combiner. A second delay circuit for delaying one of the outputs obtained by dividing the combined signal into two, and a second vector adjuster for adjusting the amplitude and phase of the other output signal obtained by dividing the combined signal of the distortion detection power combiner into two; And the second vector adjustment An auxiliary amplifier for amplifying the output of the second delay circuit; and a distortion removing power combiner for combining the output of the second delay circuit and the output of the auxiliary amplifier in opposite phases. The first vector adjuster and the first delay circuit are adjusted so that the target signal component of the input signal to the second vector adjuster is canceled out and becomes only a distortion component. Adjusting the second vector adjuster and the second delay circuit so that the distortion components of the two input signals of the synthesizer are canceled and only the intended signal component is output, and at least the second Or the first and second delay circuits are constituted by filters having phase delay characteristics.

With this configuration, the volume of the delay circuit element can be significantly reduced. In particular, in the case of the second delay filter, a high-power signal amplified by the main amplifier passes, but the delay is longer than that of the conventional coaxial delay circuit. The use of the filter not only reduces the volume but also functions to reduce the loss to the passing signal.

A second configuration of the feedforward amplifier according to the present invention is characterized in that the output terminal has a band-pass filter that allows only a target signal frequency in the first configuration. Thus, the distortion that cannot be completely removed by the feedforward circuit is removed.

A third configuration of the feedforward amplifier according to the present invention is characterized in that, in the second configuration, the main amplifier is a class AB power amplifier, and this configuration increases the power efficiency of the amplifier. Power saving,
The increase in the intermodulation distortion due to the class AB power amplification acts to be suppressed by the bandpass filter.

Further, in a fourth configuration of the feedforward amplifier according to the present invention, a distributor for distributing an input signal to a plurality of outputs, and a plurality of distributed outputs of the distributor are input and amplified. 3. A plurality of feedforward amplifiers according to any one of (3), a combiner that combines outputs of the plurality of feedforward amplifiers, and a band-pass filter that passes only a target signal frequency at an output end of the combiner. It is characterized by having.

With this configuration, a high output that cannot be obtained with a single feedforward amplifier can be obtained, and by providing redundancy, even if a failure occurs in one of the single feedforward amplifiers during operation, the output only decreases. , And acts to enhance the reliability of the system, and a small and power-saving feedforward amplifier can be realized comprehensively.

[0018]

(Embodiment 1) A feedforward amplifier according to Embodiment 1 of the present invention will be described below with reference to the drawings. In FIG. 1 showing a block diagram of a feedforward amplifier of the present embodiment, an input terminal 1 is connected to a port a of a power divider 2 and a vector adjuster 3 for adjusting a phase and an amplitude from a port b of the power divider 2. Is connected to the main amplifier 4 for power-amplifying the input signal via
The output of the main amplifier 4 is connected to the port d of the distortion detection power combiner 5. The port c of the power divider 2 is connected to the port e of the distortion detecting power combiner 5 via the delay filter 6. The delay filter 6 delays a signal passing therethrough, for example, by connecting two parallel resonant circuits that are capacitively coupled to each other as illustrated. This parallel resonance circuit can be realized by a strip line.

The port f of the distortion detecting power combiner 5 is connected to the port h of the distortion removing power combiner 8 through a second delay filter 7 having the same configuration as the delay filter 6, and the distortion detecting power combiner 5 A port g of the power combiner 5 is connected to a port i of the power combiner 8 for distortion removal via a series circuit of a vector adjuster 9 for adjusting phase and amplitude and an auxiliary amplifier 10. A band-pass filter 11 that passes a frequency band of a target signal from a port j of the power combiner 8 for removing distortion.
Is connected to the output terminal 12.

Although the delay filters 6 and 7 are a kind of bandpass filter, they are designed with emphasis on delay characteristics rather than bandpass characteristics, and the bandpass filter 11 focuses on bandpass characteristics rather than delay. It was designed.

The feedforward unit 20 surrounded by a broken line is a unit when a plurality of feedforward amplifiers described in the second embodiment are operated in parallel.

The operation of the feedforward amplifier thus configured will be described below. First, an input signal including a multi-channel component input from the input terminal 1 is split into two by a power splitter 2. One of the two divided output signals is adjusted in phase and amplitude by a vector adjuster 3 from a port b, is power-amplified by a main amplifier 4, and is input to a port d of a distortion detection power combiner 5. At this time, a signal containing a distortion component due to intermodulation in addition to the input signal component due to the non-linearity of the main amplifier 4 is input. The other of the two signals is delayed by the delay filter 6 from the port c and input to the port e of the distortion detection power combiner 5. The delay in the delay filter 6 is set so as to obtain the same delay as the delay in the main amplifier 4.

Here, the input signal components of the signals input to the ports d and e are set to have the same amplitude and opposite phases, respectively.
By adjusting the vector adjuster 3 and the delay filter 6, a signal of only the distortion component in which the input signal component is canceled is output from the port g, and the signal component input from the port e is output from the port f. To make the phase opposite, the delay in the vector adjuster 3 is increased so that the input signal from the port d is out of phase with the input signal from the port e, or the vector adjuster 3 finely adjusts the phase. , The signal from port d and the signal from port e are in phase,
In the distortion detection power combiner 5, the phase of the signal from the port d and the phase of the signal from the port e may be reversed and added.

Next, the signal including the input signal component and the distortion component output from the port f is delayed by the delay filter 7 and input to the port h of the distortion removal power combiner 8.
The signal of the distortion component output from the port g is adjusted in amplitude and phase by the vector adjuster 9, amplified by the auxiliary amplifier 10, and input to the port i of the power combiner 8 for distortion removal. Here, the vector adjuster 9, the auxiliary amplifier 10, and the delay filter 7 are adjusted so that the distortion components of the signals input to the ports h and i are equal in amplitude and opposite in phase, and the ports h and i are adjusted. Are made to have the same amplitude and opposite phase, a signal of only the input signal component from which the distortion component has been canceled is output from the port j. Also in this case, the delay in the delay filter 7 is set so as to obtain the same delay as the delay in the auxiliary amplifier 10, the delay in the vector adjuster 9 is increased, and the distortion component of the input signal to the port h and the port i Or the phase of the input distortion component from the port h and the port i in the distortion canceling power combiner 8 is adjusted only by fine adjustment of the phase in the vector adjuster 9. Inversely, the distortion component is removed by addition, and output from the port j.

In addition to such a configuration, the main amplifier 4 includes
By using a class AB power amplifier instead of a conventional class A power amplifier, the power efficiency of the power amplifier can be increased. In the class AB power amplification, the intermodulation distortion is further increased as compared with the case of the class A amplifier, but the bandpass filter 1 is connected between the port j of the distortion canceling power combiner 10 and the output terminal 12.
By inserting 1, it is possible to pass only the intended signal, remove the distortion component caused by the intermodulation, and reduce it to a level that does not cause any problem. The band-pass filter 11 does not need to have the main amplifier 4 that is a class A amplifier.

As described above, in this embodiment, the volume of the element can be significantly reduced by using the delay filter instead of the delay circuit, and the power efficiency of the amplifier can be increased by using the class AB power amplifier as the main amplifier. Power can be saved, and at this time, an increase in intermodulation distortion is suppressed by a bandpass filter, so that a small-sized and power-saving feedforward amplifier can be realized. Particularly, in the case of the delay filter 7, the signal power-amplified by the main amplifier 4 passes. However, the use of the delay filter 7 not only reduces the volume but also reduces the loss to the passing signal as compared with the conventional coaxial delay circuit. Is obtained. Therefore, if one of them is replaced with a conventional delay circuit, the delay filter 7 should be given priority over the delay filter 6.

(Embodiment 2) A feedforward amplifier according to Embodiment 2 will be described with reference to FIG. In this embodiment, 2 is used to provide redundancy.
The system is configured such that the feedforward unit of the system can be used to continue the operation by another system even if one system fails.

The input terminal 21 is a Wilkinson distributor 2
2, the Wilkinson-type distributor 22 corresponds to a quarter wavelength with respect to the wavelength of the frequency to be amplified.
One ends of the one-wavelength lines 23 and 24 are connected, and the other ends are connected to both ends of the absorption resistor 25. Both ends of the absorption resistor 25 are connected to the inputs of the independent feedforward units 20a and 20b, respectively. Feed forward unit 20
a and 20b are the same as the feedforward unit 20 of FIG. 1, respectively.

The output terminal of each feedforward unit is connected to a Wilkinson-type combiner 26. Quarter-wavelength lines 28 and 29 are connected to both ends of an absorption resistor 27 in the Wilkinson-type combiner 26, respectively. . The other ends of the quarter-wavelength lines 28 and 29 are connected to one end of a band-pass filter 30,
Is connected to the output terminal 31. The band-pass filter 30 exists, and the band-pass filter 11 of FIG. 1 may be added redundantly.

In this embodiment, two feed forward units are shown. However, in order to increase output power, a Wilkinson type divider, a quarter wavelength line of a combiner,
Three or more feedforward units may be combined by adding an absorption resistor. For details of the Wilkinson-type distributor and the synthesizer, see, for example, Yoshihiro Konishi, “Construction Method of High-Frequency / Microwave Circuit,” published by Sogo Denshi Shuppan, Ltd.
Published June 20, 993, pp. 134-135.

The operation will be described with reference to FIG. Input terminal 2
1 is split into two by a Wilkinson splitter 22, and the feedforward units 20a, 20a
0b and the distortion is reduced, the power is combined by the Wilkinson combiner 26, and the bandpass filter 30
Then, the distortion component outside the signal band is removed and output to the output terminal 31. At this time, if any one of the feedforward units 20a and 20b, for example, 20b fails, the effect of the input terminal of the feedforward unit 20b that has failed on the input side due to the absorption resistor 25 can be almost neglected. The effect of the output terminal of the feedforward unit 20b which failed when viewed from the output terminal of the unit 20a is due to the absorption resistor 2
7, the output can be reduced but the integrated system can be continuously operated.

As described above, according to the present embodiment, the input signal is divided into a plurality of signals by the Wilkinson distributor, amplified by using a plurality of sets of the feedforward unit of the first embodiment, and the respective outputs are combined by Wilkinson type. A small, high-efficiency feed that combines power with a filter and removes the generated distortion with a band-pass filter to achieve high output with low power consumption and can operate continuously even when a single feed-forward unit fails. A forward amplifier can be provided.

[0033]

As described above, according to the feedforward amplifier of the present invention, the volume of the delay circuit element can be greatly reduced by the structure of the first aspect. In particular, in the case of the second delay filter, the main amplifier amplifies the power. Although a high-power signal passes through, using a delay filter as compared with a conventional coaxial delay circuit has the effect of not only reducing the volume but also reducing the loss to the passing signal.

According to the second aspect of the present invention, there is obtained an effect that distortion that cannot be completely removed by the feedforward circuit can be removed.

According to the third aspect of the present invention, the power efficiency of the amplifier can be increased to save power, and the increase in intermodulation distortion due to class AB power amplification can be reduced by suppressing it with a bandpass filter.

Further, according to the fourth aspect of the present invention, a high output that cannot be obtained with a single feedforward amplifier can be obtained, and by providing redundancy, even if any single feedforward unit fails during operation, the output can be increased. , The operation can be continued only when the power consumption decreases, and the system operates to enhance the reliability of the system. Thus, a small and power-saving feedforward amplifier can be realized.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a feedforward amplifier according to the second embodiment;

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

FIG. 4 is a frequency spectrum diagram of a signal at ports a, d, g, and j in FIG. 3 of the conventional feedforward amplifier.

[Explanation of symbols]

 1, 21 input terminal 2 power divider 3, 9 vector adjuster 4 main amplifier 5 distortion detection power combiner 6, 7 delay filter 8 distortion removal power combiner 10 auxiliary amplifier 11, 30 bandpass filter 12, 31 output Terminal 20, 20a, 20b Feed forward unit 22 Wilkinson distributor 23, 24, 28, 29 Quarter wavelength line 25, 27 Absorption resistor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroaki Kosugi 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Matsushita Communication Industrial Co., Ltd. F term (reference) 5J090 AA04 AA41 CA21 CA92 FA14 FA20 GN02 GN05 GN07 HA25 HA29 HN03 HN16 KA13 KA15 KA44 KA68 MA14 MA20 SA14 TA01 TA03

Claims (4)

[Claims] 1. A power divider for dividing an input signal into two, a first vector adjuster for adjusting an amplitude and a phase of one of two output signals of the power divider, and a first vector adjuster A main amplifier that receives the output of the power amplifier and amplifies the power, a first delay circuit that delays the phase of the other output signal that is divided into two by the power divider, and an output of the main amplifier and the first delay circuit. A distortion detection power combiner that combines an output with an opposite phase, a second delay circuit that delays one of two outputs of a combined signal of the distortion detection power combiner, and the distortion detection power combiner A second vector adjuster that adjusts the amplitude and phase of the other output signal obtained by dividing the synthesized signal into two, an auxiliary amplifier that amplifies an output of the second vector adjuster, and an output of the second delay circuit And the output of the auxiliary amplifier in opposite phase. And a distortion compensating power combiner, wherein the distortion detecting power combiner cancels out the first signal so that a target signal component of an input signal to the second vector adjuster is canceled out and becomes only a distortion component. And the second delay adjuster and the second delay adjuster so that the distortion components of the two input signals of the distortion removal power combiner are canceled and only the intended signal component is output. And the second delay circuit is adjusted, and at least the second delay circuit or the first delay circuit
And a second delay circuit comprising a filter having a phase delay characteristic. 2. The feed-forward amplifier according to claim 1, further comprising a band-pass filter at an output end for passing only a target signal frequency. 3. The feedforward amplifier according to claim 2, wherein the main amplifier is a class AB power amplifier. 4. A plurality of feedforward amplifiers according to claim 1, wherein the distributor distributes an input signal to outputs of a plurality of systems, and a plurality of distributed outputs of the distributor are input and amplified. A combiner that combines outputs of the plurality of feedforward amplifiers; and a band-pass filter that passes only a target signal frequency at an output end of the combiner.