A circuit structure for improving linearity of a doherty amplifier

Abstract

The utility model relates to a kind of circuit structure for improving the linearity of Doherty amplifier, it is characterized in that, the Doherty amplifier includes main amplifier and at least one peak amplifier;Resistance structure is connected in series in the input end of the peak amplifier.The utility model reduces the gain expansion of peak amplifier by connecting resistance in series in the input end of peak amplifier, resistance-driven peak amplifier.The input power transmitted to peak amplifier is reduced by resistance-driven, and control mechanism of amplifier overall gain expansion is generated.By appropriately selecting the series resistance / resistance network of peak amplifier input end, the gain shape of entire power amplifier can be controlled and smoothed, so as to improve the linear operation of Doherty amplifier.

Description

TECHNICAL FIELD

[0001] The utility model relates to electronic circuit field, concretely relates to a circuit structure of improving Doherty amplifier linearity. BACKGROUND

[0002] Doherty amplifier can be used to improve the efficiency of radio frequency (RF, Radio Frequency) power amplifier, so that the radio frequency power amplifier can realize high efficiency work, especially suitable for the signal with high peak to average power ratio (PAPR, Peak to Average Power Ratio) signal modulation mode. Doherty amplifier system combines the output of two or more radio frequency power amplifiers through an impedance inversion network synthesized by 1 / 4 wavelength transmission line (QWTL, Quarter-wave transmission line), so as to realize active load modulation. Compared with the traditional power amplifier, load modulation changes the load of the main amplifier (mian amplifier), so that the whole power amplifier reaches two (or more) efficiency peaks. The increased additional efficiency peak improves the efficiency at the back off power level, and the average value of RF waveform will be at this level most of the time. Because the statistics of high peak to average power ratio signal keeps most of the RF signal power at the back off power level, load modulation improves the overall efficiency of the power amplifier. In the Doherty amplifier, the main amplifier is biased in AB class, and the peak amplifier is biased in C class. This biasing scheme is necessary for proper Doherty amplifier operation and efficiency increase. However, C class biasing can bring significant gain expansion to the peak amplifier, thereby reducing linearity.

[0003] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present disclosure, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0004] In view of the deficiencies of the prior art, the utility model discloses a kind of circuit structures of improving Doherty amplifier linearity.

[0005] The technical scheme adopted by the utility model embodiment is as follows:

[0006] A kind of circuit structure of improving Doherty amplifier linearity, the Doherty amplifier includes main amplifier and at least one peak amplifier;Resistance structure is connected in series at the input end of the peak amplifier.

[0007] A further technical solution is that the resistance structure is a resistance element or a resistance network.

[0008] A further technical solution is that the Doherty amplifier is a two-way amplifier, the main amplifier and the peak amplifier are connected in parallel; a load modulation line is connected in series at the input end of the main amplifier; a load modulation line is connected in series at the output end of the peak amplifier, and a load modulation line is connected in series at the output end of the Doherty amplifier; the resistance structure is connected in series at the input end of the peak amplifier.

[0009] A further technical solution is that the Doherty amplifier is a three-way amplifier, including a main amplifier, a first peak amplifier and a second peak amplifier connected in parallel; a load modulation line is connected in series at the input end and the output end of the main amplifier; a load modulation line is connected in series at the output end of the first peak amplifier; a load modulation line is connected in series at the input end of the second peak amplifier; the resistance structure is connected in series at the input end of the first peak amplifier and the second peak amplifier; and a load modulation line is connected in series at the output end of the Doherty amplifier.

[0010] The beneficial effects of the embodiments of the present application are as follows:

[0011] The present application reduces the gain expansion of the peak amplifier by connecting a resistance in series at the input end of the peak amplifier and resistively driving the peak amplifier. The resistive driving reduces the input power transmitted to the peak amplifier, and generates a control mechanism for the overall gain expansion of the amplifier. By appropriately selecting the series resistance at the input end of the peak amplifier, the gain shape of the entire power amplifier can be controlled and smoothed, thereby improving the linear operation of the Doherty amplifier. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 It is a two-way Doherty amplifier in the prior art.

[0013] Figure 2 It is a three-way Doherty amplifier in the prior art.

[0014] Figure 3 It is a two-way Doherty amplifier in the embodiments of the present application.

[0015] Figure 4 It is a three-way Doherty amplifier in the embodiments of the present application.

[0016] Figure 5 It is a gain variation diagram of different Doherty amplifiers in the present application. DETAILED DESCRIPTION

[0017] The specific embodiments of the present application will be described below with reference to the accompanying drawings.

[0018] In order to make the purpose, technical scheme and advantages of the present application more clear, the device of the present application is further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present application will be more clear according to the following description. It should be noted that the drawings are very simplified and all use non-precise proportions, only for the purpose of facilitating and clarifying the description of the embodiments of the present application. In order to make the purpose, features and advantages of the present application more obvious and easy to understand, please refer to the accompanying drawings. It should be noted that the structure, proportion, size and the like shown in the drawings attached to the present application are only used to cooperate with the content disclosed in the description, so that those skilled in the art can understand and read, and are not used to limit the conditions of the implementation of the present application, so they do not have the technical essence, any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effect and purpose of the present application, should still fall within the scope of the technical content disclosed by the present application.

[0019] Figure 1 The two-way Doherty amplifier in the prior art. Figure 2 The three-way Doherty amplifier in the prior art. In Figure 1 The Doherty amplifier includes a main amplifier PA1 and a peak amplifier PA2. The main amplifier PA1 and the peak amplifier PA2 are connected in parallel with each other. The load modulation network includes a load modulation line QWTL. In an embodiment, the load modulation line QWTL is a 1 / 4 wavelength transmission line. Figure 2 The Doherty amplifier includes a main amplifier PA1, a first peak amplifier PA2 and a second peak amplifier PA3. In the prior art Doherty amplifier, the main amplifier is biased in AB class, and the peak amplifier is biased in C class. The C class biasing will bring significant gain expansion to the peak amplifier, thereby reducing the linearity

[0020] The present application improves the linearity of the Doherty amplifier by connecting a resistance structure in series at the input end of the peak amplifier. The resistance structure can be a single resistance element, or a resistance network formed by connecting multiple resistance elements in series or in parallel.

[0021] Specifically, the resistance or resistance network used can be calculated according to the required attenuation degree based on the conventional T-shaped or H-shaped attenuator network with 50Ω (or given impedance Z).

[0022] Figure 3 The two-way Doherty amplifier in the embodiment of the present application. As Figure 3As shown in the figure, in the embodiment, the Doherty amplifier is a two-way amplifier, and the main amplifier PA1 and the peak amplifier PA2 are connected in parallel. The load modulation line QWTL is connected in series at the input end of the main amplifier PA1. The load modulation line QWTL is connected in series at the output end of the peak amplifier PA2, and the load modulation line QWTL is connected in series at the output end of the Doherty amplifier. The resistance structure R is connected in series at the input end of the peak amplifier PA2.

[0023] Figure 4 As shown in the figure, in the embodiment, the Doherty amplifier is a three-way amplifier, and the main amplifier, the first peak amplifier and the second peak amplifier are connected in parallel. The load modulation line QWTL is connected in series at the input end and the output end of the main amplifier PA1. The load modulation line QWTL is connected in series at the output end of the first peak amplifier PA2. The load modulation line QWTL is connected in series at the input end of the second peak amplifier PA3. The resistance structure R is connected in series at the input end of the first peak amplifier PA2 and the input end of the second peak amplifier PA3. The load modulation line QWTL is connected in series at the output end of the Doherty amplifier. Figure 4

[0024] In the embodiment, the attenuator network at the input end is amplitude control for the input signal amplitude, and the loss occurs between stages, and does not fundamentally affect the output power and the efficiency; the linearity of the Doherty structure depends on the phase amplitude compensation of the main power amplifier and the auxiliary power amplifier in the concerned power range, and the circuit structure in the embodiment provides a fine adjustable means, and the linear performance in the concerned power range is optimized by controlling the compensation mode of the two-end power amplifier. Figure 3 Figure 4 In the embodiment, the attenuator network at the input end is amplitude control for the input signal amplitude, and the loss occurs between stages, and does not fundamentally affect the output power and the efficiency; the linearity of the Doherty structure depends on the phase amplitude compensation of the main power amplifier and the auxiliary power amplifier in the concerned power range, and the circuit structure in the embodiment provides a fine adjustable means, and the linear performance in the concerned power range is optimized by controlling the compensation mode of the two-end power amplifier.

[0025] In the embodiment, the attenuator network at the input end is amplitude control for the input signal amplitude, and the loss occurs between stages, and does not fundamentally affect the output power and the efficiency; the linearity of the Doherty structure depends on the phase amplitude compensation of the main power amplifier and the auxiliary power amplifier in the concerned power range, and the circuit structure in the embodiment provides a fine adjustable means, and the linear performance in the concerned power range is optimized by controlling the compensation mode of the two-end power amplifier.

[0026] Figure 5 As shown in the figure, in the embodiment, the Doherty amplifier is a three-way amplifier, and the main amplifier, the first peak amplifier and the second peak amplifier are connected in parallel. The load modulation line QWTL is connected in series at the input end and the output end of the main amplifier PA1. The load modulation line QWTL is connected in series at the output end of the first peak amplifier PA2. The load modulation line QWTL is connected in series at the input end of the second peak amplifier PA3. The resistance structure R is connected in series at the input end of the first peak amplifier PA2 and the input end of the second peak amplifier PA3. The load modulation line QWTL is connected in series at the output end of the Doherty amplifier. Figure 5 As shown in the figure, in the embodiment, the Doherty amplifier is a three-way amplifier, and the main amplifier, the first peak amplifier and the second peak amplifier are connected in parallel. The load modulation line QWTL is connected in series at the input end and the output end of the main amplifier PA1. The load modulation line QWTL is connected in series at the output end of the first peak amplifier PA2. The load modulation line QWTL is connected in series at the input end of the second peak amplifier PA3. The resistance structure R is connected in series at the input end of the first peak amplifier PA2 and the input end of the second peak amplifier PA3. The load modulation line QWTL is connected in series at the output end of the Doherty amplifier. Figure 5 As shown in the figure, in the embodiment, the Doherty amplifier is a three-way amplifier, and the main amplifier, the first peak amplifier and the second peak amplifier are connected in parallel. The load modulation line QWTL is connected in series at the input end and the output end of the main amplifier PA1. The load modulation line QWTL is connected in series at the output end of the first peak amplifier PA2. The load modulation line QWTL is connected in series at the input end of the second peak amplifier PA3. The resistance structure R is connected in series at the input end of the first peak amplifier PA2 and the input end of the second peak amplifier PA3. The load modulation line QWTL is connected in series at the output end of the Doherty amplifier.

[0027] ​​Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, as long as the combination of the technical features does not exist in contradiction, it shall be considered as within the scope of the present disclosure.

[0028] The above-described embodiments only express several implementation manners of the present application, the description is relatively specific and detailed, but it shall not be understood as a limitation on the scope of the present application patent. It should be pointed out that, for ordinary skilled in the art, under the premise of not departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the present application patent shall be subject to the appended claims.

Claims

1. A circuit structure for improving the linearity of a Doherty amplifier, characterized in that, The Doherty amplifier includes a main amplifier and at least one peak amplifier; a resistor structure is connected in series at the input of the peak amplifier; The Doherty amplifier is a three-channel amplifier, comprising a main amplifier, a first peak amplifier, and a second peak amplifier connected in parallel. A load modulation line is connected in series at both the output and input terminals of the main amplifier. A load modulation line is connected in series at the output terminal of the first peak amplifier. A load modulation line is connected in series at the input terminal of the second peak amplifier. The resistor structure is connected in series at the input terminals of both the first and second peak amplifiers. A load modulation line is connected in series at the output terminal of the Doherty amplifier. Alternatively, the Doherty amplifier is a two-channel amplifier, with the main amplifier and the peak amplifier connected in parallel; a load modulation line is connected in series at the input of the main amplifier; a load modulation line is connected in series at the output of the peak amplifier; a load modulation line is connected in series at the output of the Doherty amplifier; and the resistor structure is connected in series at the input of the peak amplifier.

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