JP2014176001A - High frequency amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen a frequency band of gain while maintaining high efficiency of Doherty amplifiers.SOLUTION: An input divider distributes an input signal to a plurality of systems. A plurality of Doherty amplifiers are disposed for the plurality of systems, respectively, to serve different peak frequency bands to each other. A divider distributes the input signal to two systems. A main amplifier amplifies one of the distributed signals. A peak amplifier amplifies a peak of the other of the distributed signals. A signal combiner combines respective output signals of the main amplifier and the peak amplifier. The signal combiner includes matching means for matching respective output impedances of the main amplifier and the peak amplifier to the wavelength of the input signal, and wavelengths of such respective matching means of the plurality of Doherty amplifiers are selected to the peak frequency bands. A Doherty amplifier output combiner combines outputs of the plurality of Doherty amplifiers.

Description

  Embodiments described herein relate generally to a high-frequency amplifier that amplifies a high-frequency signal using a Doherty amplifier.

  In recent years, high-efficiency amplifiers such as Doherty amplifiers are widely used in high-frequency amplifiers used for communication infrastructures such as base stations in order to achieve downsizing and low power consumption.

  This Doherty amplifier is composed of two amplifiers, a main amplifier and a peak amplifier. When the output level is low, only the main amplifier operates. When the output level is high, the main amplifier and the peak amplifier operate simultaneously. . That is, when a modulated wave is input to the Doherty amplifier, the peak amplifier operates only when the peak is high, so that the average value of power consumption is smaller than when a normal amplifier is used. As a result, the Doherty amplifier can realize a highly efficient amplifier operation.

  However, in the conventional Doherty amplifier, there is a part depending on the frequency (wavelength) in the circuit, and a wide frequency band cannot be secured in the gain. For this reason, it is difficult for a conventional Doherty amplifier to amplify a carrier wave having a wide frequency band used in mobile communication systems such as 3G (Third Generation) and LTE (Long Term Evolution) with good frequency characteristics.

  In addition, even if the carrier frequency is close to a normal frequency, a conventional Doherty amplifier with a narrow frequency band must prepare a different Doherty amplifier for each frequency, which increases costs. There's a problem.

JP 2012-29239 A

  As described above, since the conventional Doherty amplifier cannot secure a wide frequency band in gain, it is difficult to amplify a carrier wave having a wide frequency band with good frequency characteristics. Further, the conventional Doherty amplifier has a problem that the cost increases because the frequency band of the gain is narrow and a different Doherty amplifier must be prepared for each frequency.

  An object of the present invention is to provide a high-frequency amplifier capable of widening the gain frequency band while maintaining the high efficiency of the Doherty amplifier.

  According to this embodiment, the high-frequency amplifier includes an input distributor, a plurality of Doherty amplifiers, and a Doherty amplifier output combiner. The input distributor distributes input signals to a plurality of systems. A plurality of Doherty amplifiers are provided in each of the plurality of systems and are responsible for different peak frequency bands. Each of the plurality of Doherty amplifiers includes a distributor, a main amplifier, a peak amplifier, and a combiner. The distributor distributes the input signal into two systems. The main amplifier amplifies the one of the distributed signals. The peak amplifier amplifies the peak of the other distributed signal. The signal synthesizer synthesizes output signals of the main amplifier and the peak amplifier. The signal synthesizer includes a matching unit that matches the output impedance of each of the main amplifier and the peak amplifier according to the wavelength of the input signal, and matches the wavelength of the matching unit of each of the plurality of Doherty amplifiers to the peak frequency band. Select. The Doherty amplifier output synthesizer synthesizes the outputs of the plurality of Doherty amplifiers.

The block diagram which shows the structure of the high frequency amplifier which concerns on this embodiment. The figure which shows the frequency band of the gain which becomes a peak output by the Doherty amplifier shown in FIG. 1 is a block diagram showing a configuration in which Doherty amplifiers are connected in parallel in multiple stages as a high-frequency amplifier according to the present embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of the high-frequency amplifier according to this embodiment.

  The high frequency amplifier shown in FIG. 1 includes an input distributor 1, a first Doherty amplifier 21 and a second Doherty amplifier 22, and an output synthesizer 3. The high frequency amplifier distributes an input high frequency signal into two systems by the input distributor 1, inputs one signal to the first Doherty amplifier 21, and inputs the other signal to the second Doherty amplifier 22. After amplification, the signal is synthesized by the output synthesizer 3.

  Here, the first Doherty amplifier 21 will be described.

  The first Doherty amplifier 21 includes a distributor 21-1, a main amplifier 21-21, a peak amplifier 21-22, a combiner 21-3 (including a first quarter wavelength line 21-4), and a second 1 / 4 wavelength line 21-5.

  The distributor 21-1 distributes the high-frequency signal input to the input end to the two systems equally or at a constant ratio.

  The main amplifier 21-21 is, for example, a class A or class AB amplifier, and receives one high-frequency signal distributed by the distributor 21-1, and always amplifies the power. The peak amplifier 21-22 is, for example, a class C amplifier, and receives the other high-frequency signal distributed by the distributor 21-1, and amplifies power as a peak region when the high-frequency signal exceeds a predetermined level.

  The combiner 21-3 includes a first quarter wavelength line 21-4, and peaks the high frequency signal output from the main amplifier 21-21 via the first quarter wavelength line 21-4. After combining with the high frequency signal output from the amplifier 21-22, the combined signal is output to the output combiner 3 through the second quarter wavelength line 21-5.

  That is, the synthesizer 21-3 adjusts the output impedance of the main amplifier 21-21 and the peak amplifier 21-22 by the first quarter wavelength line 21-4, and the main amplifier 21-21 and the peak amplifier 21. The high frequency signal output from -22 is synthesized.

  Here, the first quarter wavelength line 21-4 also plays a role as an impedance converter. When the input signal level is such that only the main amplifier 21-21 operates, the main amplifier 21- The impedance is converted so that the load applied to the output terminal 21 is twice the load applied to the combined output terminal. The first quarter-wave line 21-4 has the main amplifier 21-21 and the peak amplifier 21 when the input signal level is such that the main amplifier 21-21 and the peak amplifier 21-22 operate together. Impedance conversion is performed so that the load applied to each output terminal of −22 is the same as the load applied to the combined output terminal.

  The second quarter wavelength line 21-5 is connected to the subsequent stage of the synthesis point for synthesizing the outputs of the main amplifier 21-21 and the peak amplifier 21-22. The second quarter wavelength line 21-5 is located at the position of the main amplifier 21-21 and the peak amplifier 21-22 due to the first quarter wavelength line 21-4 inserted on the main amplifier 21-21 side. This is a line for compensating for the phase difference. The second quarter wavelength line 21-5 matches the impedance of the synthesis point where the outputs of the main amplifier 21-21 and the peak amplifier 21-22 are combined with the characteristics of the subsequent stage.

  The first Doherty amplifier 21 is circuit impedance matched by a termination circuit 21-6 connected to the distributor 21-1.

  As described above, in the first Doherty amplifier 21, the impedance matching of the circuit is achieved by the first quarter wavelength line 21-4 and the second quarter wavelength line 21-5. Therefore, it is possible to change the frequency of the output high frequency signal by changing the length of the quarter wavelength of each of the quarter wavelength lines 21-4 and 21-5.

  On the other hand, as with the first Doherty amplifier 21, the second Doherty amplifier 22 includes a distributor 22-1, a main amplifier 22-21, a peak amplifier 22-22, a combiner 22-3 (first quarter wavelength line). 22-4) and the second quarter wavelength line 22-5, and functions in the same manner as the first Doherty amplifier 21. Therefore, description of each component is abbreviate | omitted here.

  As described above, in the second Doherty amplifier 22, similarly to the first Doherty amplifier 21, the combiner 22-3 includes the first quarter-wave line 22-4, and this first quarter-wavelength 22. By changing the length of the quarter wavelength of the line 22-4 and the second quarter wavelength line 22-5, the frequency of the output high frequency signal can be changed.

  Therefore, the length of the quarter wavelength is changed so that the first Doherty amplifier 21 and the second Doherty amplifier 22 output high-frequency signals having different frequencies.

  According to the above configuration, the 1/4 wavelength lengths of the 1/4 wavelength lines 21-4 and 21-5 of the first Doherty amplifier 21 and the 1/4 wavelength lines 22-4 and 22-5 of the second Doherty amplifier 22 are obtained. Are changed in accordance with different carrier frequencies. As a result, the first Doherty amplifier 21 and the second Doherty amplifier 22 can output high-frequency signals having different peak gain frequencies.

  As described above, the high-frequency amplifier synthesizes and outputs the high-frequency signals having different peak gain frequencies output from the first Doherty amplifier 21 and the second Doherty amplifier 22. FIG. 2 is a diagram showing the frequency band of the gain that is output by the high-frequency amplifier shown in FIG. FIG. 2 shows, as an example, a frequency band of a gain that becomes a peak when a signal with a frequency of 2.1 GHz and a signal with a frequency of 2.2 GHz are output and combined. As shown in FIG. 2, the high-frequency amplifier of this embodiment synthesizes and outputs high-frequency signals with different peak gain frequencies, so that the peak gain frequency band is widened and the Doherty amplifier configuration is widened. Can be realized.

  Therefore, according to the present embodiment, it is possible to provide a high frequency amplifier capable of widening the gain frequency band while maintaining the high efficiency of the Doherty amplifier.

  Further, the lengths of the quarter wavelengths of the quarter wavelength lines 21-4 and 21-5 of the first Doherty amplifier 21 and the quarter wavelength lines 22-4 and 22-5 of the second Doherty amplifier 22 are changed. Since the same circuit can be used, the design is easy, and it is not necessary to prepare a different device for each frequency, so that the installation cost can be reduced.

  Here, in the above-described embodiment, the configuration in which the signals output from the two Doherty amplifiers 21 and 22 are combined to widen the frequency band of the gain has been described. However, as shown in FIG. A plurality of Doherty amplifiers 21 to 2n (n is a natural number) having different gain frequencies are connected in parallel in multiple stages to synthesize signals output from the plurality of Doherty amplifiers 21 to 2n, thereby further gain frequency bands. It is also possible to increase the bandwidth.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. This embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. This embodiment and its modifications are included in the scope of the present invention and the gist thereof, and are also included in the invention described in the claims and the equivalent scope thereof.

  DESCRIPTION OF SYMBOLS 1 ... Input distributor, 21, 22 ... Doherty amplifier, 21-1, 22-1 ... Distributor, 21-21, 22-21 ... Main amplifier, 21-22, 22-22 ... Peak amplifier, 21-3, 22-3 ... Synthesizer, 21-4, 22-4, 21-5, 22-5 ... 1/4 wavelength line, 21-6, 22-6 ... Termination circuit, 3 ... Output combiner.

Claims (3)

An input distributor that distributes input signals to multiple systems;
A plurality of Doherty amplifiers provided in each of the plurality of systems and responsible for different peak frequency bands,
A Doherty amplifier output synthesizer that synthesizes the outputs of the plurality of Doherty amplifiers;
The plurality of Doherty amplifiers are:
A distributor that distributes an input signal to two systems; a main amplifier that amplifies the one of the distributed signals;
A peak amplifier for amplifying the peak of the other distributed signal;
A signal synthesizer that synthesizes the output signals of the main amplifier and the peak amplifier,
The signal synthesizer
Matching means for matching the output impedance of each of the main amplifier and the peak amplifier according to the wavelength of the input signal,
A high frequency amplifier obtained by selecting a wavelength of the matching means of each of the plurality of Doherty amplifiers according to the peak frequency band.   2. The high-frequency amplifier according to claim 1, wherein the matching unit of the synthesizer includes an impedance converter that is connected to a subsequent stage of the main amplifier and converts an impedance in a previous stage to be combined with the output of the peak amplifier.   The high-frequency amplifier according to claim 2, wherein the impedance converter is a ¼ wavelength line.

Images