CN109600118B - Harmonic injection theory suitable for class F high-efficiency power amplifier - Google Patents

Abstract

The invention discloses a harmonic injection theory suitable for an F-class high-efficiency power amplifier, which comprises the steps of calculating parameters related to power levels for describing nonlinear characteristics of transistors and input grid voltage, calculating drain efficiency during secondary harmonic injection according to the parameters, calculating output power during secondary harmonic injection according to the ratio of the power during secondary harmonic injection to the power during non-harmonic injection, and establishing the relationship between the calculated drain efficiency output power during secondary harmonic injection and the obtained grid voltage waveform of an input end, the drain voltage waveform of an output end and the current waveform; and controlling the voltage waveform of the grid electrode at the input end of the transistor according to the relation so as to realize the control of the drain electrode efficiency and the output power of the transistor. The invention can realize fast calculation of the optimal injection waveform.

Description

Harmonic Injection Theory for Class F High Efficiency Power Amplifiers

technical field

The invention relates to the technical field of wireless communication power amplifiers, in particular to a harmonic injection theory suitable for Class F high-efficiency power amplifiers.

Background technique

With the rapid development of the new generation of mobile communication system (5G), the radio frequency transceiver as the core of the system is also facing a new round of changes and updates. The indicators of high efficiency, high power, high gain, and high linearity have increasingly become the focus of people's attention. In the entire RF transceiver system, the RF power amplifier is the module that consumes the most energy. Therefore, the efficiency of the power amplifier directly determines the energy consumption level of the entire transmitting terminal. If the working efficiency of the RF power amplifier is improved, the power consumption of the entire system can be reduced, thereby meeting the performance requirements of the new generation communication system. There are two main types of high-efficiency power amplifiers at present: switching power amplifiers (class E power amplifiers are the most typical) and harmonic tuning power amplifiers (class F power amplifiers are the most typical).

The characteristics of switching power amplifiers are: high efficiency, simple structure, and easy implementation. However, it has disadvantages such as low carrier frequency and high drain peak voltage. The harmonic tuning power amplifier does not have the above problems, so it has become one of the hot areas of power amplifier research. The characteristic of the traditional harmonic tuning power amplifier is that the drain voltage and drain current of the output terminal of the transistor are harmonically controlled, so that the waveforms in the time domain are staggered from each other, thereby achieving the purpose of high efficiency. In recent years, new harmonic tuning power amplifiers have been researched on harmonic control from the input end of transistors, so as to achieve the purpose of improving the efficiency of harmonic tuning power amplifiers. In 2017, Amirreza et al. conducted the first research on the harmonic injection theory of Class J power amplifiers based on theory and simulation, and concluded that half-sine waveform injection can greatly improve the power and efficiency of Class J power amplifiers.

Contents of the invention

The purpose of the present invention is to aim at the technical defects existing in the prior art, and provide a kind of harmonic injection theory suitable for F-class high-efficiency power amplifiers, can calculate the optimal injection waveform of F-class high-efficiency power amplifiers, and then achieve from the input terminal The purpose of harmonic injection to improve the power and efficiency of Class F high-efficiency power amplifiers.

The technical scheme adopted for realizing the purpose of the present invention is:

A kind of harmonic injection theory applicable to class F high-efficiency power amplifiers, comprising steps:

Calculate the two parameters m ₁ , m2 related to the power series a ₀ -a ₅ describing the nonlinear characteristics of the transistor and the input gate voltage, and calculate the drain when the second harmonic is injected according to the parameters m ₁ , m ₂ Efficiency η _F ,

According to the ratio of the power _P'out when the second harmonic is injected to the power P _out when the harmonic is not injected, that is, the injection power ratio _Pnor , the output power _P'out when the second harmonic is injected is calculated,

表示栅极输入电压二次谐波相对于基波的初相位，V_dc表示晶体管的供电电压和V_k表示晶体管的膝点电压，V_gs2，V_gs1分别表示栅极输入电压的二次谐波注入幅值与栅极输入电压的基波幅值；

Indicates the initial phase of the second harmonic of the gate input voltage relative to the fundamental wave, V _dc indicates the supply voltage of the transistor and V _k indicates the knee point voltage of the transistor, V _gs2 and V _gs1 respectively indicate the second harmonic of the gate input voltage Injection amplitude and fundamental amplitude of gate input voltage;

Establish the relationship between the drain efficiency η _F calculated during the second harmonic injection, the output power P' _out , and the obtained gate voltage waveform at the input terminal, the drain voltage waveform at the output terminal, and the current waveform;

The gate voltage waveform at the input terminal of the transistor is controlled according to the above relationship, so as to control the drain efficiency and output power of the transistor.

The parameters m ₁ and m ₂ are shown as follows:

where V _gs0 represents the DC term of the gate input voltage.

The harmonic injection theory applicable to Class F high-efficiency power amplifiers of the present invention can quickly calculate the optimal injection waveform, which shows that the improvement of power and efficiency of Class F power amplifiers can be realized through harmonic injection at the input end, and its optimal The injected waveform also lays a good foundation for cascading multi-stage Class F power amplifiers.

Description of drawings

Figure 1 is a schematic diagram of a Class F high-efficiency power amplifier based on a field effect tube model;

和V_gs2/V_gs1变化的等高线图；Fig. 2a When the parameter m ₁ =-06, m ₂ =1.4 when the second harmonic is injected, the injection power ratio P _nor varies with

and contour plots of V _gs2 /V _gs1 changes;

和V_gs2/V_gs1变化的等高线图；Fig. 2b When the parameter m ₁ =-06, m ₂ =1.5 when the second harmonic is injected, the injected power ratio P _nor varies with

and contour plots of V _gs2 /V _gs1 changes;

和V_gs2/V_gs1变化的等高线图；Fig. 2c When the parameter m ₁ =-06, m ₂ =1.6 when the second harmonic is injected, the injected power ratio P _nor varies with

and contour plots of V _gs2 /V _gs1 changes;

和V_gs2/V_gs1变化的等高线图；Fig. 2d When the parameters m ₁ =-06, m ₂ =1.4 when the second harmonic is injected, the drain efficiency η _F varies with

and contour plots of V _gs2 /V _gs1 changes;

和V_gs2/V_gs1变化的等高线图；Fig. 2e When the parameters m ₁ =-06, m ₂ =1.5 when the second harmonic is injected, the drain efficiency η _F varies with

and contour plots of V _gs2 /V _gs1 changes;

Figure 3a is a schematic diagram of the ADS simulation of the Class F high-efficiency power amplifier when the sine wave is injected;

Figure 3b is a schematic diagram of the ADS simulation of the class F high-efficiency power amplifier when the second harmonic is injected;

Figure 4a is the gate voltage waveform of a class F high-efficiency power amplifier when a sine wave is injected;

Figure 4b is the gate voltage waveform of the Class F high-efficiency power amplifier when the second harmonic is injected;

Figure 5a is the drain voltage waveform and current waveform of the Class F high-efficiency power amplifier when the sine wave is injected;

Figure 5b is the drain voltage waveform and current waveform of the Class F high-efficiency power amplifier when the second harmonic is injected.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The harmonic injection theory applicable to class-F high-efficiency power amplifiers is realized through the following steps:

In a traditional Class F high-efficiency power amplifier (assuming that the transistor used is a FET tube), when the gate voltage at the input terminal of the transistor is injected with a sine wave, the expression of its input voltage V _gs (θ) is:

V _gs (θ) = V _gs0 + V _gs1 sin(θ) (1)

Among them, V _gs0 represents the DC term of the gate input voltage, and V _gs1 represents the fundamental amplitude of the gate input voltage.

Due to the nonlinear effect of the transistor, the relationship between its input voltage and output current can be expressed as a power series, namely:

Among them, a ₀ -a ₅ represents the coefficient of the power series, and i _F (θ) represents the output current of the drain.

Therefore, putting (1) into (2) can get the expression of the drain current in the case of sinusoidal voltage waveform injection, namely:

i _F (θ)＝I _dc +i ₁ (θ)+i ₂ (θ)+i ₃ (θ)+i ₄ (θ)+i ₅ (θ) (3)

It can be seen from the above formula that in the case of sinusoidal voltage waveform injection, the drain current produces a DC term, a fundamental term and a higher harmonic term. For class F high-efficiency power amplifiers, the impedance condition of odd harmonics is an open circuit, so the third harmonic item i ₃ (θ) of the drain current should be zero at the impedance end. The resulting third harmonic drain current i ₃ (θ) will leak from the transistor to ground, as shown in Figure 1.

If the leaked drain third harmonic current is i ₃ (θ), its expression is:

i ₃ (θ)=r ₃ cos(3θ)+q ₃ sin(3θ) (4)

where r3 and _q3 are the real and imaginary coefficients _of its Fourier expansion.

Then the drain current i' _F (θ) at the impedance end face should be:

i' _F (θ) = i _F (θ)-i ₃ (θ) (5)

The drain current i' _F (θ) at this time does not contain the third harmonic current, so there is no cubic term in its Fourier expansion, namely:

_The values of r3 and _q3 can be obtained from the above formula:

r ₃ =0 (8)

Similarly, the real and imaginary coefficients of the 5th harmonic i ₅ (θ) can also be obtained:

r ₅ =0 (10)

At the same time, the standard form of the drain current of Class F is:

Where _Imax represents the maximum current at the drain of the transistor, and θ represents the phase angle.

When harmonic injection is not performed, the drain current i' _F (θ) obtained by the power series should be equal to the drain current of the Class F standard, thereby satisfying the condition of Class F, namely:

When the gate voltage at the input terminal of the transistor has a second harmonic injection, the expression of its input voltage V _gs (θ) is:

表示栅极输入电压二次谐波相对于基波的初相位。Among them, V _gs0 and V _gs1 still represent the DC term and fundamental wave amplitude of the gate input voltage. V _gs2 represents the second harmonic amplitude of the gate input voltage.

Indicates the initial phase of the second harmonic of the gate input voltage relative to the fundamental wave.

即：At this point, substituting Equation (17) into Equation (2) can obtain the expression of the drain current when the second harmonic is injected

which is:

It can be seen that higher order harmonics are generated at the output due to the injection of the second harmonic at the input.

The standard form of the Class F drain voltage is:

V _ds (θ)＝V _dc +(V _dc -V _k )(1.2071 sin(θ)+0.2804 sin(3θ)+0.0733 sin(5θ)) (19)

Among them, V _dc represents the supply voltage of the drain, and V _k represents the knee point voltage of the transistor.

According to the drain current identity (13)-(16) when harmonics are not injected, the drain current expression (18) after the second harmonic injection and the drain voltage expression (19) of class F, it can be calculated The output power _P'out when the second harmonic is injected, and then calculate the ratio of the power _{P'out when the second harmonic is injected to the power P out when} the harmonic is not injected, that is, the injection power ratio _Pnor :

Among them, m ₁ and m ₂ represent two parameters related to the power series a ₀ -a ₅ describing the nonlinear characteristics of the transistor and the input gate voltage, and their expressions are shown in (21) and (22).

According to the drain current identity (13)-(16) when no harmonics are injected, the drain current expression (18) after the second harmonic injection, the drain voltage expression (19) and m ₁ of class F, The expression (21), (22) of m ₂ can also calculate the expression of the drain efficiency η _F when the second harmonic is injected, namely:

和V_gs2/V_gs1有关的注入功率比P_nor、漏极效率η_F的表达式，进而求得其最佳的二次谐波注入幅值V_gs2以及初相位

For a specific FET transistor, if the power series a ₀ -a ₅ , the supply voltage V _dc and the knee voltage V _k can be fitted to describe the nonlinear characteristics of the transistor, the second harmonic at the input terminal can be obtained After wave injection only with

Expressions of injection power ratio P _nor and drain efficiency η _F related to V _gs2 /V _gs1 , and then obtain the best second harmonic injection amplitude V _gs2 and initial phase

和V_gs2/V_gs1变化的等高线图。从图中可以得到以下结论：As shown in Figures 2a-2e, according to formulas (20) and (23), the injection power ratio P _nor and the drain efficiency η _F can be obtained under the conditions of parameters m ₁ =-06, m ₂ =1.4, 1.5, 1.6 , whose value varies with

and contour plots of V _gs2 /V _gs1 changes. The following conclusions can be drawn from the figure:

和V_gs2/V_gs1的解集中得到。最大的输出功率可以比未注入时高出1.2dB(P_nor＝1.33)。此外，最大漏极效率可以达到91.0％，显著高于未注入时的理论效率(82.77％)。因此，当输入端有最优二次谐波注入时，其性能会有大幅度的提高。For different parameters m ₁ , m ₂ , the maximum output power and drain efficiency can be obtained from

and the solutions of V _gs2 /V _gs1 are obtained. The maximum output power can be 1.2dB higher than that without injection (P _nor =1.33). In addition, the maximum drain efficiency can reach 91.0%, significantly higher than the theoretical efficiency (82.77%) without implantation. Therefore, when there is optimal second harmonic injection at the input, its performance will be greatly improved.

却是相同的。也就是说

是个固定值(3π/2)，其值不随晶体管的变化而变化。这是一个非常有用的结论，对于选择更高输出功率和效率的F类功放的二次谐波相位有很大帮。For different parameters m ₁ , m ₂ , the optimal V _gs2 /V _gs1 is different. Therefore, its value depends on the characteristics of the transistor. However, the optimal phase

But it is the same. That is to say

It is a fixed value (3π/2), and its value does not change with the change of the transistor. This is a very useful conclusion, which is very helpful for selecting the second harmonic phase of a class F power amplifier with higher output power and efficiency.

The advantage of the harmonic injection theory of the present invention is that it can calculate the optimal injection waveform of the Class F high-efficiency power amplifier. This optimal injection waveform is not only beneficial to improving the efficiency and output power of the Class F high-efficiency power amplifier, but also expands the It also lays a theoretical foundation for the mutual cascading of multi-stage F class high-efficiency power amplifiers.

处。Next, according to the actual test of the above-mentioned technology, the optimal injection waveform of the Class F high-efficiency power amplifier is calculated by actually applying the harmonic injection theory. The transistor used is GaN HEMT CGH60010D from Wolfspeed Company. The reason for choosing this kind of transistor is that its nonlinearity is very strong, and it can provide the harmonics required by the F-class power amplifier. At the same time, the influence of package parasitics is small, and it can reflect the performance of the transistor itself to the greatest extent. The specific values of the relevant parameters of the transistor provided by the manufacturer are as follows: the standard drain voltage is 28V, the knee point voltage is 2.4V, and the maximum drain current of the transistor is 1.74A. Therefore, the drain bias voltage is selected to be 28V in the specific implementation , the gate bias voltage V _gs0 is -3.0V, and the sinusoidal voltage amplitude V _gs1 input to the gate is 5.4V. Calculated by (23): the maximum value of drain efficiency η _F is at V _gs2 /V _gs1 = 0.2511, the initial phase

place.

Figure 3a is a schematic diagram of building an ADS simulation platform for a Class F high-efficiency power amplifier without harmonic injection. The harmonics at the output end are controlled at the 3rd order to meet the impedance requirements of the F-class power amplifier. Figure 3b is a schematic diagram of building an ADS simulation platform for a Class F high-efficiency power amplifier under the condition of second harmonic injection. Figure 4a is the gate voltage waveform at the input without harmonic injection. Figure 4b is the gate voltage waveform at the input in the case of second harmonic injection. Figure 5a shows the drain voltage and current waveforms at the output without harmonic injection. Figure 5b is the drain voltage waveform and current waveform at the output in the case of second harmonic injection, from which it can be seen that the drain waveforms of the injection and non-injection are in line with the time domain waveform diagram of the F class power amplifier.

Table 1

Table 1 shows the theoretical calculation and simulated output power and drain efficiency without harmonic injection and second harmonic injection. Through the comparison of the above simulation results and theoretical calculation results, the following conclusions can be found:

1. Compared with the performance of uninjected class F power amplifier, the output power and drain efficiency increased by 20.6% and 6.6% respectively under the condition of theoretical optimal waveform injection. Therefore, it can be proved that the method of second harmonic injection does improve the overall performance of Class F power amplifiers, and further expands the application scenarios and application prospects of Class F high-efficiency power amplifiers.

2. The relative error between the simulation results of output power and drain efficiency and the theoretical calculation results is very small. For example, when the optimal waveform is injected, the relative errors between the simulation results and theoretical calculation results of output power and drain efficiency are only 1.3% and 2.4%, respectively. Therefore, the correctness of the said harmonic injection theory applicable to the class F power amplifier can be verified.

为3π/2。这与半正弦波的理论二次谐波展开项的相位一致。同时最优波形二次谐波幅值与基波幅值的比V_gs2/V_gs1是0.25，这与半正弦的理论值(0.42)相接近。因此，F类的最优注入波形可以近似理解为准半正弦波，如图4b所示。而这个结论也将对双级高效F类功率放大器的相互级联奠定基础，即如果前一级的输出端可以提供一个半正弦的电压波形，两级级联起来的性能一定是最佳的。3. The second harmonic phase of the theoretically optimal waveform

is 3π/2. This agrees with the phase of the theoretical second harmonic expansion term of the half sine wave. At the same time, the ratio V _gs2 /V _gs1 of the second harmonic amplitude of the optimal waveform to the fundamental amplitude is 0.25, which is close to the theoretical value (0.42) of half sine. Therefore, the optimal injection waveform of class F can be approximately understood as a quasi-half sine wave, as shown in Figure 4b. And this conclusion will also lay the foundation for the mutual cascading of two-stage high-efficiency Class F power amplifiers, that is, if the output terminal of the previous stage can provide a half-sine voltage waveform, the performance of the cascaded two stages must be the best.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, these improvements and Retouching should also be regarded as the protection scope of the present invention.

Claims (2)

1. The harmonic injection method applicable to Class F high-efficiency power amplifiers is characterized in that, comprising steps: Calculate the two parameters m ₁ , m ₂ related to the power series a ₀ -a ₅ describing the nonlinear characteristics of the transistor and the input gate voltage, and calculate the leakage when the second harmonic is injected according to the parameters m ₁ , m ₂ Pole efficiency η _F ,

Calculate the output power P' when the second harmonic is injected according to the ratio of the output power _P'out when the second harmonic is injected to the output power P _out when the harmonic is not injected, that is, the injection power ratio P _nor relationship _out ,

Indicates the initial phase of the second harmonic of the gate input voltage relative to the fundamental wave, V _dc indicates the supply voltage of the transistor and V _k indicates the knee point voltage of the transistor, V _gs2 and V _gs1 respectively indicate the second harmonic of the gate input voltage Injection amplitude and fundamental amplitude of gate input voltage; Establish the relationship between the drain efficiency η _F calculated during the second harmonic injection, the output power _P'out, and the obtained gate voltage waveform at the input terminal, the drain voltage waveform at the output terminal, and the current waveform; The gate voltage waveform at the input terminal of the transistor is controlled according to the above relationship, so as to control the drain efficiency and output power of the transistor. 2. as claimed in claim 1, be applicable to the harmonic injection method of class F high-efficiency power amplifier, it is characterized in that, described parameter m ₁ , m ₂ represent as follows:

where V _gs0 represents the DC term of the gate input voltage.

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