CN109067364B - Doherty power amplifier with broadband and efficient output - Google Patents

Abstract

The invention discloses a wide-band high-efficiency output Doherty power amplifier, comprising a power divider, a phase shifter, a main power amplifier, an auxiliary power amplifier, a compensation network and a load modulation network; the output end of the power divider is connected to the phase shifter The input terminal of the phase shifter is connected to the input terminal of the main power amplifier and the auxiliary power amplifier respectively, and the output terminals of the main power amplifier and the auxiliary power amplifier are connected to the input terminal of the load modulation network through the compensation network. end. Compared with the traditional technology, the present invention is simple in structure and convenient in implementation, so that the Doherty power amplifier can still maintain high-efficiency output characteristics in a wide frequency range.

Description

A Doherty Power Amplifier with Broadband and High Efficiency Output

technical field

The present invention relates to the field of wireless communication, and more particularly, to a Doherty power amplifier with wide-band and high-efficiency output.

Background technique

The RF power amplifier is an important component of the wireless system. With the continuous development of wireless communication technology, the data transmission rate and channel capacity of the communication system are continuously improved, which puts forward new requirements for the design of the power amplifier. Efficiency and bandwidth are the two core indicators of power amplifiers. Expanding the bandwidth can enable communication equipment to support more bandwidth formats and transmission protocols, and improving efficiency can reduce energy loss.

When transmitting a high-to-average ratio modulated signal, in order to reduce the nonlinear distortion of the signal, a power back-off technique is often used to keep the signal away from the saturation region of the power amplifier. The efficiency of the traditional power amplifier will drop sharply with the backoff of the output power. Since the Doherty power amplifier can maintain high efficiency within the backoff power range, it is widely used in communication systems. In traditional Doherty power amplifiers, compensation lines are generally used to adjust the phase characteristics before the two power amplifiers. Since the phase of the compensation lines changes sharply with the frequency, the phase difference between the two power amplifiers will change with the frequency. drastic changes, resulting in a sharp drop in the output efficiency of the two-way power amplifiers combined, and it is impossible to maintain high-efficiency output characteristics in a wide frequency range.

SUMMARY OF THE INVENTION

In order to solve the above problems, the purpose of the present invention is to provide a Doherty power amplifier with a wide frequency and high efficiency output, which can still keep the high efficiency output of the Doherty power amplifier in a wide frequency range.

In order to make up for the deficiencies in the prior art, the technical scheme adopted in the present invention is:

A broadband high-efficiency output Doherty power amplifier, comprising a power divider, a phase shifter, a main power amplifier, an auxiliary power amplifier, a compensation network and a load modulation network; the output end of the power divider is connected to the input end of the phase shifter , the output terminals of the phase shifter are respectively connected to the input terminals of the main power amplifier and the auxiliary power amplifier, and the output terminals of the main power amplifier and the auxiliary power amplifier are both connected to the input terminal of the load modulation network through the compensation network.

Further, the phase shifter includes a phase shift line and a reference line; the input end of the phase shift line is connected to the first output end of the power divider, and the output end is connected to the input end of the main power amplifier; the reference line The input end is connected to the second output end of the power divider, and the output end is connected to the input end of the auxiliary power amplifier.

Further, the compensation network includes a compensation line TL1, a compensation line TL2 and an impedance transformation line TL3, and both ends of the impedance transformation line TL3 are respectively connected to the output ends of the compensation line TL1 and the compensation line TL2; the output end of the main power amplifier Through the compensation line TL1 and the impedance transformation line TL3, the output end of the auxiliary power amplifier is connected to the input end of the load modulation network through the compensation line TL2.

Further, the phase shifting line adopts a T-shaped structure, including a transmission line TL8, an open branch TL9 and a transmission line TL10, the transmission line TL8, the open branch TL9 and the transmission line TL10 are connected in pairs, and one end of the transmission line TL8 is connected to the power divider. The first output end, one end of the open-circuit branch TL9 is connected to the input end of the main power amplifier.

Further, the load modulation network includes a transmission line TL4, a transmission line TL5, a transmission line TL6, a transmission line TL7 and a load resistor RL connected in series in sequence, the transmission line TL4 is respectively connected to the compensation line TL2 and the impedance transformation line TL3, and the load resistance RL is connected to to the reference location.

Preferably, the characteristic impedances of the compensation line TL1 and the compensation line TL2 are both 50 ohms.

Preferably, the characteristic impedance and electrical length of the transmission line TL8 and the transmission line TL10 are the same.

Preferably, the load modulation network is a Chebyshev impedance transformation network.

Preferably, the power divider is an unequal Wilkinson power divider.

Preferably, the main power amplifier and the auxiliary power amplifier are both inverse class F power amplifiers.

The beneficial effect of the present invention is that the phase shifter structure is used to replace the compensation line structure arranged before the main power amplifier and the auxiliary power amplifier in the traditional technology, so that the change degree of the phase difference of the two branches with the frequency change can be reduced, In this way, the Doherty power amplifier can always maintain high-efficiency output; the compensation network can make the output of the two power amplifiers form a combined circuit, and then output to the outside through the load modulation network to realize communication. Therefore, the present invention has a simple structure and is convenient to implement, so that the Doherty power amplifier can still maintain high-efficiency output characteristics in a wide frequency range.

Description of drawings

The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings to illustrate the embodiments of the present invention in detail.

Fig. 1 is the structural principle diagram of the present invention;

Fig. 2 is to compare the present invention with the traditional Doherty power amplifier, the contrast curve diagram of the phase difference of two-way power amplifiers;

FIG. 3 is a graph comparing the maximum drain efficiency at a saturated output power state comparing the present invention with a conventional Doherty power amplifier.

Detailed ways

Referring to FIG. 1 , a broadband and high-efficiency output Doherty power amplifier of the present invention includes a power divider PD, a phase shifter 1, a main power amplifier PA1, an auxiliary power amplifier PA2, a compensation network 2 and a load modulation network 3; the power The output end of the distributor PD is connected to the input end of the phase shifter 1, and the output end of the phase shifter 1 is respectively connected to the input end of the main power amplifier PA1 and the auxiliary power amplifier PA2, the main power amplifier PA1 and the auxiliary power The output terminals of the amplifier PA2 are all connected to the input terminals of the load modulation network 3 through the compensation network 2 .

Preferably, the load modulation network 3 is a Chebyshev impedance transformation network.

Preferably, the power divider PD is an unequal Wilkinson power divider.

Preferably, the main power amplifier PA1 and the auxiliary power amplifier PA2 are both inverse class F power amplifiers, and their output matching network not only satisfies the optimal matching conditions of the fundamental wave, but also presents an infinitesimal impedance to odd harmonics, and even harmonics The wave presents an impedance close to infinity, so that the current in the internal plane of the transistor presents a square wave, the voltage presents a half-sine wave, and there is a certain angular relationship between the two, so that the time domain overlap between the voltage and the current is reduced. It can reduce the DC energy consumption and improve the efficiency; the main power amplifier PA1 can be turned on under any input power condition, and the auxiliary power amplifier PA2 is turned on when the output power of the Doherty power amplifier falls back to 6dB.

Specifically, the working principle of the traditional Doherty power amplifier is well known, in which the phase relationship between the main power amplifier PA1 and the auxiliary power amplifier PA2 is mainly determined by the compensation line, while the phase characteristic of the traditional compensation line is linear with the change of frequency, At the center frequency, the optimal phase can be obtained by adjusting the length of the compensation line, so that the main power amplifier PA1 and the auxiliary power amplifier PA2 are in the best combined state, but when the operating frequency deviates from the center frequency, it is generally reflected in the operating range At both ends, that is, in the wide frequency range, the phase difference between the two branches will change drastically with the change of frequency, which will greatly affect the combining efficiency;

Using the phase shifter 1 to replace the compensation line structure arranged before the main power amplifier PA1 and the auxiliary power amplifier PA2 in the traditional technology can reduce the change degree of the phase difference of the two branches with the frequency change, thereby making the Doherty power amplifier Always maintain high-efficiency output; the compensation network 2 can make the output of the two power amplifiers form a combination, and then output to the outside through the load modulation network 3 to achieve communication. Therefore, the present invention has a simple structure and is convenient to implement, so that the Doherty power amplifier can still maintain high-efficiency output characteristics in a wide frequency range;

According to the experiment, referring to FIG. 3 , in the saturated output power state, in the frequency range of 2.45GHz to 2.65GHz, that is, in the center frequency range, the maximum drain efficiency of the present invention is higher than that of the conventional Doherty power amplifier. The efficiency is slightly lower, but in the frequency range of 1.9GHz to 2.45GHz and the frequency range of 2.65GHz to 3.0GHz, that is, in the wide frequency range, the maximum drain efficiency of the present invention is greater than that of the conventional Doherty power amplifier. improved and the maximum drain efficiency remained above 70% in the 2.2GHz to 2.7GHz frequency range.

Further, referring to FIG. 1 , the phase shifter 1 includes a phase shift line 11 and a reference line Q; the input end of the phase shift line 11 is connected to the first output end of the power divider PD, and the output end is connected to the main power The input end of the amplifier PA1; the input end of the reference line Q is connected to the second output end of the power divider PD, and the output end is connected to the input end of the auxiliary power amplifier PA2.

Preferably, the reference line Q can be an ordinary transmission line; the design center frequency of the phase shifter 1 is 2.5GHz, and the phase difference required by the original compensation line is 80 degrees. The phase difference is also 80 degrees. It can be seen from Figure 2 that the phase of the original compensation line changes linearly with the frequency. When the input signal frequency deviates from the center frequency, the phase difference changes greatly. After using phase shifter 1, you can It can be seen that the change degree of the phase difference of the two branches is obviously slowed down, so that the combining efficiency of the Doherty power amplifier in the frequency band is improved.

Further, referring to FIG. 1 , the compensation network 2 includes a compensation line TL1, a compensation line TL2 and an impedance transformation line TL3, and both ends of the impedance transformation line TL3 are respectively connected to the output ends of the compensation line TL1 and the compensation line TL2, thereby forming a combined The output end of the main power amplifier PA1 is connected to the input end of the load modulation network 3 through the compensation line TL1 and the impedance transformation line TL3, and the output end of the auxiliary power amplifier PA2 is connected to the input end of the load modulation network 3 through the compensation line TL2, that is, the combined end is connected in series to the load On the modulation network 3, preferably, the characteristic impedance of the compensation line TL1 and the compensation line TL2 are both 50 ohms, and the characteristic impedance of the impedance transformation line TL3 can also be 50 ohms.

Further, referring to FIG. 1 , the phase-shifting line 11 adopts a T-shaped structure, including a transmission line TL8, an open branch TL9 and a transmission line TL10, the transmission line TL8, the open branch TL9 and the transmission line TL10 are connected in pairs, and one end of the transmission line TL8 is connected To the first output end of the power divider PD, one end of the open branch TL9 is connected to the input end of the main power amplifier PA1; preferably, the characteristic impedance and electrical length of the transmission line TL8 and the transmission line TL10 are the same.

Further, referring to FIG. 1 , the load modulation network 3 includes a transmission line TL4, a transmission line TL5, a transmission line TL6, a transmission line TL7 and a load resistance RL serially connected in series, and the transmission line TL4 is respectively connected to the compensation line TL2 and the impedance transformation line TL3, so The load resistance RL is connected to the reference ground, which can convert the combined characteristic impedance to half of the original, and the output end of the load modulation network 3 can be directly used as the output end of the Doherty power amplifier, of course, it can also be used in the load modulation network 3. The rear end of the device is provided with relevant adjustment circuits or modules, and then the output is implemented.

The above content has discussed the preferred embodiments and basic principles of the present invention in detail, but the present invention is not limited to the above-mentioned embodiments. Those skilled in the art should understand that there will be various Equivalent modifications and substitutions fall within the scope of the claimed invention.

Claims (8)

1. A broadband Doherty power amplifier with high-efficiency output is characterized in that: the power amplifier circuit comprises a Power Divider (PD), a phase shifter (1), a main power amplifier (PA1), an auxiliary power amplifier (PA2), a compensation network (2) and a load modulation network (3); the output end of the Power Divider (PD) is connected to the input end of a phase shifter (1), the output end of the phase shifter (1) is respectively connected to the input ends of a main power amplifier (PA1) and an auxiliary power amplifier (PA2), and the output ends of the main power amplifier (PA1) and the auxiliary power amplifier (PA2) are connected to the input end of a load modulation network (3) through a compensation network (2);

the phase shifter (1) comprises a phase shifting line (11) and a reference line (Q); the input end of the phasing line (11) is connected to a first output end of the Power Divider (PD), and the output end is connected to the input end of a main power amplifier (PA 1); an input of the reference line (Q) is connected to a second output of the Power Divider (PD) and an output is connected to an input of an auxiliary power amplifier (PA 2);

the phase-shifting line (11) adopts a T-shaped structure and comprises a transmission line TL8, an open-circuit branch TL9 and a transmission line TL10, wherein the transmission line TL8, the open-circuit branch TL9 and the transmission line TL10 are connected in a pairwise manner, one end of the transmission line TL8 is connected to a first output end of a Power Divider (PD), and one end of the open-circuit branch TL9 is connected to an input end of a main power amplifier (PA 1).

2. The wide-band high-efficiency Doherty power amplifier of claim 1, wherein: the compensation network (2) comprises a compensation line TL1, a compensation line TL2 and an impedance transformation line TL3, wherein two ends of the impedance transformation line TL3 are respectively connected to output ends of the compensation line TL1 and the compensation line TL 2; the output end of the main power amplifier (PA1) is connected to the input end of the load modulation network (3) through a compensation line TL1 and an impedance transformation line TL3, and the output end of the auxiliary power amplifier (PA2) is connected to the input end of the load modulation network (3) through a compensation line TL 2.

3. The wide-band high-efficiency Doherty power amplifier of claim 2, wherein: the load modulation network (3) comprises a transmission line TL4, a transmission line TL5, a transmission line TL6, a transmission line TL7 and a load resistor RL which are sequentially connected in series, wherein the transmission line TL4 is respectively connected to a compensation line TL2 and an impedance transformation line TL3, and the load resistor RL is connected to a reference ground.

4. The wide-band high-efficiency Doherty power amplifier of claim 2, wherein: the characteristic impedance of both the compensation line TL1 and the compensation line TL2 is 50 ohms.

5. The wide-band high-efficiency Doherty power amplifier of claim 1, wherein: the transmission line TL8 and the transmission line TL10 have the same characteristic impedance and electrical length.

6. The wide-band high-efficiency Doherty power amplifier of claim 1, wherein: the load modulation network (3) is a Chebyshev impedance transformation network.

7. The wide-band high-efficiency Doherty power amplifier according to any one of claims 1-6, wherein: the Power Divider (PD) is an unequal Wilkinson power divider.

8. The broadband high-efficiency Doherty power amplifier of claim 7, wherein: the main power amplifier (PA1) and the auxiliary power amplifier (PA2) are both inverse class F power amplifiers.

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