LU501100B1 - Dual-mode Efficiency Enhanced Linear Power Amplifier - Google Patents

Abstract

The invention discloses dual-mode efficiency enhanced linear power amplifier, which comprises a two-stage power amplification circuit and an output circuit with a LIPA structure. The two-stage power amplification circuit of LIPA structure consists of a 45-degree phase-shifted two-stage amplification branch circuit and a negative 45-degree phase-shifted two-stage amplification branch circuit, and is characterized in that the output circuit comprises a branch circuit A and a branch circuit B, wherein the branch circuit A comprises an inductor L8, a capacitor C6, an inductor L10 and a capacitor C5; and the branch circuit B comprises an inductor L9, a capacitor C7 and a capacitor C3; the other pole of the capacitor C3 in the branch circuit B and the output end of the inductor L10 in the branch circuit a are both connected with the power output end RFOUT.

Description

DESCRIPTION HUS0TTO0 Dual-mode Efficiency Enhanced Linear Power Amplifier

TECHNICAL FIELD The invention relates to a power amplifier, in particular to a linear power amplifier with dual-mode efficiency.

BACKGROUND The LIPA (Load Insensitive Power Amplifier) allows a good PAE (Power-Added Efficiency) even at a low output power level. However, the PAE of this high-efficiency LIPA can't perform well under various powers. In order to improve the PAE of LIPA, a dual-mode efficiency-enhanced linear power amplifier design is proposed. This method is to make the high-efficiency LIPA have better PAE at both high and low power output levels. At present, mobile phone suppliers need cheaper, smaller and better performance mobile phones. For WCDMA/CDMA power amplifiers, it is a very competitive demand to improve PAE at both high and low output power levels.

In 2005, Skyworks Company invented a novel and efficient LIPA, as shown in Figure 1, which includes a two-stage power amplifier circuit and an output circuit with LIPA structure, wherein the two-stage power amplification circuit with LIPA structure consists of a 45-degree phase-shifted two-stage amplification branch circuit and a negative 45-degree phase-shifted two-stage amplification branch circuit. This amplifier allows for good PAE at low output power levels without sacrificing its performance and linearity at other output power levels. This switch type LIPA has been working very well. Its output circuit is composed of upper and lower channel output phase shifters, and Wilkinson power combiner, which synthesizes the outputs of these two channels. This design works well and provides a good load insensitive structure. Switchable LIPA proposed by Skyworks has the advantages of good work, high stability, strong durability and insensitive load. However, the PAE of this high-efficiency LIPA is no longer the competitor of WCDMA power amplifier with high PAE. This design has the following limitations:

1. Firstly, the switching LIPA tends to have lower PAE at the highest power level HUS0TTO0 than at single-ended operation, because Wilkinson power combiner itself is lossy. This inherent loss is partly due to the discrete resistors connected in parallel between the two channels. At present, PAE is so important that even the relatively moderate loss of

0.2-0.3dB caused by discrete resistors can't be tolerated, let alone reduce PAE by 2-3%. This is the most important deficiency.

2. The switched LIPA mode uses the first part of the output matching network as both an impedance converter and a phase shifter. This single structure provides multiple functions, so it is difficult to achieve optimal impedance and precise phase balance at the same time.

3. Because the upper channel and the lower channel are not really independent of each other, Wilkinson power combiner introduces some tuning difficulties, and this is because the upper channel and the lower channel are connected together by Wilkinson power combiner; wherein the change of the impedance of one channel will greatly affect the impedance of the other channel, so any adjustment of the impedance of one channel will affect the impedance of the other channel. Therefore, the switch LIPA was not allowed to flexibly adjust the upper channel and the lower channel respectively; for example, it is impossible for one channel to achieve the optimal impedance in high power mode and the other channel to achieve the optimal impedance in low power mode.

4. Wilkinson Power Synthesizer is also a kind of bulky structure, which occupies some valuable real estate.

SUMMARY In order to solve the shortcomings of the prior art, an object of the present invention is to provide a dual-mode efficiency enhanced linear power amplifier. In this patent, removing some components and reducing the number of components will make the whole design cheaper, reduce the complexity of the system and improve the reliability of the system.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

A dual-mode efficiency enhanced linear power amplifier comprises a two-stage HUS0TTO0 power amplifying circuit and an output circuit in a LIPA structure. The two-stage power amplification circuit with LIPA structure consists of a 45-degree phase-shifted two-stage amplification branch circuit and a negative 45-degree phase-shifted two-stage amplification branch circuit; output circuit comprise a branch circuit A and a branch circuit B, wherein the branch circuit A comprises an inductor L8, a capacitor C6, an inductor L10 and a capacitor C5; output end of inductor L8 is connected in series with input end of inductor L10 through capacitor C6, one pole of capacitor C5 is connected with output end of inductor L8, and the other pole of capacitor CS is grounded. And branch circuit B comprise an inductor L9, a capacitor C7 and a capacitor C3, the negative 45-degree phase-shifting two-stage amplification branch circuit is electrically connected with the input end of the inductor L9, and the output end of the inductor L9 is connected with one pole of the capacitor C3; one pole of the capacitor C7 is connected with the output end of the inductor L8, and the other pole of the capacitor C7 is grounded. And the other pole of the capacitor C3 in the branch circuit B and the output end of the inductor L10 in the branch circuit A are both connected with the power output end RFOUT.

According to the working method of the dual-mode efficiency enhanced linear power amplifier, when working in low power mode, in order to save energy, the negative 45-degree phase-shifted two-stage amplification branch circuit is closed, and all power flows through the 45-degree phase-shifted two-stage amplification branch circuit; when working in high power mode, the balanced structure of 45-degree phase-shifted two-stage amplification branch circuit and negative 45-degree phase-shifted two-stage amplification branch circuit is used; after the input signal comes in, it is separated into a 45-degree phase-shifted two-stage amplification branch circuit and a negative 45-degree phase-shifted two-stage amplification branch circuit; after being amplified by the two branch circuits, the separated signals are phase shifted back, so that the separated signals can be mixed in phase in the output circuit.

The invention has the advantages that the patent is an improvement of the LIPA HUS0TTO0 power amplifier, other circuit structures are reserved in the LIPA power amplifier, only the output circuit is improved, and the invention has the following advantages: (1) Higher PAE than LIPA: a. for UMTS frequency band modulated by WCDMA: in 28dBm high power mode, the highest PAE is 44%, while the highest PAE of standard LIPA is only 41%; in 16dBm low power mode, the highest PAE is 21%, while the highest PAE of standard LIPA is only 18%.

b. for CELL band modulated by WCDMA: in the high power mode of 28.5dBm, the highest PAE is 44%, while the highest PAE of standard LIPA is only 41%; in 16dBm low power mode, the highest PAE is 21%, while the highest PAE of standard LIPA is only 18%.

(2) In the high power mode, keep the load insensitivity. The impedance in the 45-degree phase-shifted two-stage amplification branch circuit is different from that in the negative 45-degree phase-shifted two-stage amplification branch circuit, so the impedance transformation is separated from the phase balance, and even under the different impedance transformation in the two branch circuits, the phase balance can be ensured.

(3) In the high-power mode, the 45-degree phase-shifted two-stage amplification branch circuit works in the gain compression state, while the negative 45-degree phase-shifted two-stage amplification branch circuit works in the gain expansion state, at which time it works near the power peak area.

(4) Removing Wilkinson power combiner makes the loss of output matching circuit lower.

(5) In the power synthesis channel (output circuit), only one spiral inductor is used and two components are eliminated, so the overall size of the output network becomes smaller. With fewer SMT (Surface Mount Technology) components and a printed spiral inductor, the PA model can be realized in an area of 3 mmx3 mm; while the standard LIPA structure is difficult to compress to an area of 3 mmx3 mm. Removing some components in the output circuit and reducing the number of components will make the whole design cheaper, reduce the complexity of the system HUS0TTO0 and improve the reliability of the system.

(6) The 45-degree phase-shifted two-stage amplification branch circuit is optimized for the low-power mode alone, so the PAE is improved in the low-power mode.

BRIEF DESCRIPTION OF THE FIGURES The following is a further detailed description of the present invention with reference to the drawings and specific embodiments: Fig. 11s a circuit diagram of an existing LIPA structure power amplifier; Fig. 2 is a circuit diagram of the present invention.

DESCRIPTION OF THE INVENTION As shown in fig. 2, a dual-mode efficiency enhanced linear power amplifier comprises a two-stage power amplification circuit and an output circuit in LIPA structure, wherein the two-stage power amplification circuit with LIPA structure consists of a 45-degree phase-shifted two-stage amplification branch circuit and a negative 45-degree phase-shifted two-stage amplification branch circuit; output circuit comprise a branch circuit A and a branch circuit B, the branch circuit A comprises an inductor L8, a capacitor C6, an inductor L10 and a capacitor C5; output end of inductor L8 is connected in series with input end of inductor L10 through capacitor C6, one pole of capacitor CS is connected with output end of inductor L8, and the other pole of capacitor CS is grounded; branch circuit B comprise an inductor L9, a capacitor C7 and a capacitor C3, and the negative 45-degree phase-shifted two-stage amplification branch circuit is electrically connected with the input end of the inductor L9; output end of inductor L9 is connected with one pole of capacitor C3, one pole of capacitor C7 is connected with output end of inductor L8, and the other pole of capacitor C7 is grounded; and the other pole of the capacitor C3 in the branch circuit B and the output end of the inductor L10 in the branch circuit A are both connected with the power output end RFOUT.

According to the working method of the dual-mode efficiency enhanced linear power amplifier when working in low power mode, in order to save energy, the negative 45-degree phase-shifted two-stage amplification branch circuit is closed, and 7501700 all power flows through the 45-degree phase-shifted two-stage amplification branch circuit; when working in high power mode, the balanced structure of 45-degree phase-shifted two-stage amplification branch circuit and negative 45-degree phase-shifted two-stage amplification branch circuit is used; after the input signal comes in, it 1s separated into a 45-degree phase-shifted two-stage amplification branch circuit and a negative 45-degree phase-shifted two-stage amplification branch circuit; after being amplified by the two branch circuits, the separated signals are phase shifted back, so that the separated signals can be mixed in phase in the output circuit.

1. The Wilkinson power combiner is removed from the output network, which reduces the inherent loss of the output matching circuit, thus improving the PAE.

2. The Wilkinson power combiner is eliminated in the power combiner channel, and the spiral inductor is used to reduce the output network size.

3. Cancel Wilkinson power combiner, and directly mix the output of two channels of power amplifier after impedance matching and phase shift matching, thus canceling the third-order intermodulation distortion, and greatly improving its linearity and PAE.

4. Successfully separated the structure of the output circuit from the phase balance network to realize high PAE in both high power and low power modes.

5. In high power mode, because the output circuit structure separates the impedance matching network from the phase balance network, the upper and lower channels can ensure the phase balance under different impedance matching.

6. In the high power mode, the power amplifier of the upper channel works in the gain compression state, while the power amplifier of the lower channel works in the gain expansion state, and at this time it works near the power peak area.

7. Optimize the upper channel in low power mode alone, so as to improve PAE in low power mode.

Generally speaking, the separated impedance matching network and phase-shifting network, as well as the channels in high and low power modes, can greatly improve PAE without sacrificing linearity.

The above is only a preferred embodiment of the present invention, which of HUS0TTO0 course cannot be used to limit the right scope of the present invention.

It should be pointed out that for ordinary technicians in the technical field, any modification or equivalent replacement of the technical scheme of the present invention will not depart from the protection scope of the technical scheme of the present invention.

Claims (2)

1. CLAIMS LU501100 I. A dual-mode efficiency enhanced linear power amplifier comprises a two-stage power amplification circuit and an output circuit in LIPA structure, wherein the two-stage power amplification circuit with LIPA structure consists of a 45-degree phase-shifted two-stage amplification branch circuit and a negative 45-degree phase-shifted two-stage amplification branch circuit, characterized in that output circuit comprise a branch circuit A and a branch circuit B, the branch circuit A comprises an inductor L8, a capacitor C6, an inductor L10 and a capacitor C5; the 45-degree phase shift two-stage amplification branch circuit is electrically connected with the input end of the inductor L8, output end of inductor L8 is connected in series with input end of inductor L10 through capacitor C6, one pole of capacitor CS is connected with output end of inductor L8, and the other pole of capacitor C5 is grounded; branch circuit B comprise an inductor L9, a capacitor C7 and a capacitor C3, and the negative 45-degree phase-shifted two-stage amplification branch circuit is electrically connected with the input end of the inductor L9; output end of inductor L9 is connected with one pole of capacitor C3, one pole of capacitor C7 is connected with output end of inductor L8, and the other pole of capacitor C7 is grounded; and the other pole of the capacitor C3 in the branch circuit B and the output end of the inductor L10 in the branch circuit A are both connected with the power output end RFOUT.
2. 2. A working method of the dual-mode efficiency enhanced linear power amplifier according to claim 1 is characterized in that when working in low power mode, in order to save energy, the negative 45-degree phase-shifted two-stage amplification branch circuit is closed, and all power flows through the 45-degree phase-shifted two-stage amplification branch circuit; when working in high power mode, the balanced structure of 45-degree phase-shifted two-stage amplification branch circuit and negative 45-degree phase-shifted two-stage amplification branch circuit is used; after the input signal comes in, it is separated into a 45-degree phase-shifted two-stage amplification branch circuit and a negative 45-degree phase-shifted two-stage amplification branch circuit; after being amplified by the two a . . LU501100 branch circuits, the separated signals are phase shifted back, so that the separated signals can be mixed in phase in the output circuit.