CN101699767B - Feed circuit of radio frequency power amplifier - Google Patents

Abstract

The embodiment of the present invention discloses a radio frequency power amplifier feed circuit, including: a DC power supply, a first microstrip line, a second microstrip line, a third microstrip line, a first capacitor, a second capacitor and a third capacitor; The electrical length of the first microstrip line is λ/8 of N times; the electrical length of the third microstrip line is λ/4 of M times; λ is the fundamental wavelength, N is an odd number, and M is an odd number; the first microstrip The first end of the line is connected to the drain or gate of the RF power amplifier, the second end of the first microstrip line is connected to the first end of the second microstrip line, and the second end of the second microstrip line is connected to the DC power supply ; The second end of the first microstrip line is connected to the first end of the third microstrip line, and the third capacitor is connected between the second end of the third microstrip line and the ground; the first capacitor and the second capacitor are connected in parallel connected between the second end of the second microstrip line and the ground. The embodiment of the present invention presents an open circuit for the second harmonic without affecting the matching of the fundamental wave, which helps to realize the matching of the second harmonic and improve the efficiency of the power amplifier.

Description

A radio frequency power amplifier feed circuit

technical field

The invention relates to the field of electronic technology, in particular to a radio frequency power amplifier feed circuit.

Background technique

In the wireless communication system, the RF power amplifier is a key component to realize the wireless transmission of RF signals. Its function is to convert the DC power provided by the DC power supply into RF power and transmit it. Power amplifier efficiency is one of the important indicators to measure the performance of RF power amplifiers, which is defined as the ratio of the output power P _out of the RF power amplifier to the DC power P _dc supplied by the DC power supply. High-efficiency power amplifiers have the advantages of reducing energy consumption during operation, lowering the operating temperature of the power amplifier, improving reliability, and reducing requirements for cooling systems.

There are many ways to achieve high-efficiency power amplifiers, such as ClassD, ClassE, and ClassF. The principle is to improve the efficiency of the power amplifier by reducing the overlapping of the power tube drain voltage waveform and current waveform. The second harmonic reflection angle control is also a high-efficiency power amplifier design technology. It adjusts the connection position of the resonator on the transmission line and changes the second harmonic reflection angle in the nonlinear product of the power amplifier output, thereby reducing the voltage waveform and current Waveform overlap improves power amplifier efficiency.

As shown in FIG. 1 , an existing radio frequency power amplifier circuit includes a power transistor 101 , a matching circuit 102 , a feed circuit 103 , a DC blocking capacitor 104 , a transmission line 105 and a resonator 106 . Among them, the feed circuit 102 includes a common microstrip line with an electrical length of λ/4 (λ is the wavelength of the fundamental wave). One end of the λ/4 microstrip line is connected to the direct current power supply DC, and the other end is connected to the power supply through the matching circuit 102. The drain of the tube 101 is connected as a feed point; the source of the power tube 101 is used as the input terminal of the radio frequency power amplifier to receive the radio frequency signal; the radio frequency signal is output from the transmission line 105 after being amplified; the λ/4 micro Capacitors C1 and C2 are respectively connected in parallel between one end of the strip line and the ground. Wherein, the resonator 106 is also a λ/4 microstrip line, one end of which is connected to the transmission line 105, and the other end is connected to the ground. For the second harmonic, the electrical length of the λ/4 microstrip line of the resonator 106 is 180 degrees, so the impedance of the resonator 106 is equal to 0, thus forming a short circuit point of the second harmonic on the transmission line 105, for The second harmonic total reflection in the non-linear product of the power amplifier output; by changing the position of the short-circuit point (such as changing the length of the transmission line 105), the second harmonic reflection angle can be adjusted, and then find the condition that the voltage waveform and the current waveform overlap the least, Improve power amplifier efficiency.

For the RF power amplifier, the feed circuit 103 is required to transmit the direct current of the DC power supply DC to the drain of the power tube 101, but the RF signal energy cannot flow away from the feed circuit 103, because the RF power will be lost in this way, The efficiency of the power amplifier is reduced; on the other hand, the high peak voltage of the radio frequency signal will damage the components of the feed circuit 103 . Therefore, the feed circuit 103 should have the following characteristics when seen from the output end of the power amplifier: low resistance for the DC power supply DC, open circuit or parallel reactance for the fundamental wave.

At present, a common feeding method is to use a λ/4 microstrip line, such as the λ/4 microstrip line shown in the feeding circuit 103 in FIG. 1 . For the fundamental wave, the electrical length of the λ/4 microstrip line is 90 degrees, so the impedance of the feed circuit 103 is infinite. Seen from the drain of the power amplifier, the feed circuit 103 appears as an open circuit, which does not affect the fundamental wave matching. However, the λ/4 microstrip line of the feed circuit 103 presents a short-circuit characteristic at the second harmonic frequency, so that the second harmonic is at the feed point (that is, the connection between the λ/4 microstrip line and the matching network 102 ) will appear total reflection, resulting in that the position of the resonator 106 will not be able to adjust the second harmonic reflection.

If the control of the second harmonic is considered, the λ/4 microstrip line cannot be used in the feed circuit 103 shown in Fig. Subharmonics appear as reactance, not short circuits. An existing method for improving the feed circuit of a radio frequency power amplifier is to replace the λ/4 microstrip line of the feed circuit 103 in Fig. 1 with a λ/8 microstrip line. For the second harmonic, the λ/8 microstrip line The electrical length of the strip line is 90 degrees, so the impedance of the feed circuit is equal to infinity, and the feed circuit is open to the second harmonic, which does not affect the second harmonic matching.

However, the disadvantage of this is that the fundamental wave of the feeder appears as a reactance element and participates in the fundamental wave matching. In order to achieve the best fundamental wave matching, the reactance value often needs to be changed, and the change of this reactance value will affect the fundamental wave and the fundamental wave at the same time. The second harmonic matching brings difficulties to the design of high-efficiency power amplifiers.

Contents of the invention

The embodiment of the present invention provides a radio frequency power amplifier feed circuit, which can appear as an open circuit to the second harmonic, and has no effect on the fundamental wave matching, which is conducive to the realization of the second harmonic matching, and achieves the purpose of improving the efficiency of the power amplifier .

In order to solve the above technical problems, embodiments of the present invention provide the following technical solutions:

An embodiment of the present invention provides a radio frequency power amplifier feed circuit, including:

DC power supply, first microstrip line, second microstrip line, third microstrip line, first capacitor, second capacitor and third capacitor; the electrical length of the first microstrip line is N times λ/8 ; The electrical length of the third microstrip line is λ/4 of M times; the λ is the fundamental wavelength, the N is an odd number, and the M is an odd number;

Wherein, the first end of the first microstrip line is connected to the drain or gate of the radio frequency power amplifier, the second end of the first microstrip line is connected to the first end of the second microstrip line, and the The second end of the second microstrip line is connected to the DC power supply;

The second end of the first microstrip line is connected to the first end of the third microstrip line, and the third capacitor is connected between the second end of the third microstrip line and ground;

The first capacitor and the second capacitor are connected in parallel between the second end of the second microstrip line and ground.

It can be seen from the above technical solutions that the embodiments of the present invention have the following advantages:

In the embodiment of the present invention, the electrical length of the third microstrip line is an odd multiple of λ/4. For the fundamental wave, the third microstrip line presents high resistance, which can be regarded as an open circuit and will not affect the basic matching; For the second harmonic, the third microstrip line will present a short circuit, so that the second end of the first microstrip line is equivalent to grounding, so that for the second harmonic, the electrical length is an odd multiple of λ/8 The first microstrip line will appear as an open circuit, which will not affect the matching of the second harmonic. Therefore, the embodiment of the present invention presents an open circuit for the fundamental wave and the second harmonic, so that the feeding network does not affect the matching of the fundamental wave and the matching of the second harmonic, and is suitable for the second harmonic reflection angle control circuit design. To improve power amplifier efficiency.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the structural diagram of existing radio frequency power amplifier circuit;

FIG. 2 is a structural diagram of a feed circuit for a radio frequency power amplifier provided in an embodiment of the present invention;

Fig. 3 is a structural diagram of another RF power amplifier feeding circuit provided in an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Please refer to FIG. 2 . FIG. 2 is a structural diagram of a radio frequency power amplifier feeding circuit provided in an embodiment of the present invention. As shown in Figure 2, the feed circuit may include:

DC power supply DC, first microstrip line L1, second microstrip line L2, third microstrip line L3, first capacitor C1, second capacitor C2, and third capacitor C3;

Wherein, the electrical length of the above-mentioned first microstrip line L1 is N times λ/8; the electrical length of the third microstrip line L3 is M times λ/4; λ is the fundamental wavelength, and N and M are both odd numbers , such as 1, 3, 5, 7, ..., and so on.

Preferably, the electrical length of the second microstrip line L2 can also be λ/8, or the electrical length of the second microstrip line L2 can also be other values smaller than λ/8, or the electrical length of the second microstrip line L2 It may also be other values greater than λ/8, which are not limited in this embodiment of the present invention.

When the electrical length of the second microstrip line L2 is other values less than λ/8, the microstrip line formed by connecting the second microstrip line L2 to the first microstrip line L1 will exhibit inductance characteristics; when the second microstrip line When the electrical length of L2 is other values greater than λ/8, the microstrip line formed by connecting the second microstrip line L2 to the first microstrip line L1 will exhibit capacitance characteristics.

Preferably, the values of the above-mentioned N and M can be 1 at the same time, so that the electrical lengths of the first microstrip line L1 and the third microstrip line L3 are as short as possible, so that the RF power amplifier feed circuit can be improved as much as possible. performance.

Wherein, the first end of the first microstrip line L1 is connected to the drain or gate of the radio frequency power amplifier, the second end of the first microstrip line L1 is connected to the first end of the second microstrip line L2, and the second end of the first microstrip line L2 is connected to the first end of the second microstrip line L2. The second end of the second microstrip line L2 is connected to the above-mentioned direct current power supply DC;

Wherein, the second end of the above-mentioned first microstrip line L1 is connected to the first end of the third microstrip line L3, and the above-mentioned third capacitor C3 is connected between the second end of the third microstrip line L1 and the ground; The above-mentioned first capacitor C1 and the second capacitor C2 are respectively connected in parallel between the second end of the two microstrip lines L2 and the ground.

For example, a third capacitor C3 may also be connected between the second end of the above-mentioned first microstrip line L1 and the first end of the third microstrip line L3, and the second end of the third microstrip line L1 is connected to the ground , as shown in Figure 3, can also achieve the purpose of the present invention.

Wherein, the first end of the first microstrip line L1 and the drain or gate of the radio frequency power amplifier can be connected through a matching circuit, which can better optimize the drain of the first microstrip line L1 and the radio frequency power amplifier. Impedance matching between poles or gates.

For example, the above-mentioned second end of the first microstrip line L1 and the first end of the second microstrip line L2 are connected by soldering or circuit printing.

For example, the above-mentioned second end of the first microstrip line L1 is connected to the first end of the third microstrip line L3 by soldering or circuit printing.

Those skilled in the art can understand that the above-mentioned connection between the first microstrip line L1 and the second microstrip line L2 can actually be a microstrip line with an electrical length of λ/4, and the above-mentioned third microstrip line L3 The first end of the λ/4 microstrip line can be connected to the middle point, which will not affect the realization of the present invention.

In the RF power amplifier feeding circuit provided by the embodiment of the present invention, the electrical length of the third microstrip line L3 is an odd multiple of λ/4. For the fundamental wave, the third microstrip line L3 presents high resistance, which can be regarded as An open circuit will not affect the basic matching; for the second harmonic, the third microstrip line L3 will present a short circuit, so that the second end of the first microstrip line L1 is equivalent to grounding, so that for the second harmonic In other words, the first microstrip line L1 whose electrical length is an odd multiple of λ/8 will appear as an open circuit, which will not affect the matching of the second harmonic. Therefore, the embodiment of the present invention presents an open circuit for the fundamental wave and the second harmonic, so that the feeding network does not affect the matching of the fundamental wave and the matching of the second harmonic, and is suitable for the second harmonic reflection angle control circuit design. To improve power amplifier efficiency.

The above is a detailed introduction to a radio frequency power amplifier feed circuit provided by the embodiment of the present invention. In this paper, specific examples are used to illustrate the principle and implementation of the present invention. The description of the above embodiment is only used to help understand the present invention. The method of the invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and scope of application. In summary, the content of this specification should not be understood To limit the present invention.

Claims (5)

1. a feed circuit of radio frequency power amplifier is characterized in that, comprising:

DC power supply, first microstrip line, second microstrip line, the 3rd microstrip line, first electric capacity, second electric capacity and the 3rd electric capacity; The electrical length of described first microstrip line is N λ/8 doubly; The electrical length of described the 3rd microstrip line is M λ/4 doubly; Described λ is a fundamental wavelength, and described N is an odd number, and described M is an odd number;

Wherein, first end of described first microstrip line is connected with the drain electrode or the grid of radio-frequency power amplifier, and second end of described first microstrip line is connected with first end of second microstrip line, and second end of described second microstrip line is connected with described DC power supply;

Second end of described first microstrip line is connected with first end of the 3rd microstrip line, is connected described the 3rd electric capacity between second end of described the 3rd microstrip line and the ground; Perhaps, second end of described first microstrip line with connect described the 3rd electric capacity between first end of the 3rd microstrip line is connected, second end of described the 3rd microstrip line is connected with ground;

Described first electric capacity and second electric capacity are connected between second end and ground of described second microstrip line in parallel.

2. feed circuit of radio frequency power amplifier as claimed in claim 1 is characterized in that, the electrical length of described second microstrip line is λ/8.

3. feed circuit of radio frequency power amplifier as claimed in claim 1 or 2 is characterized in that, described N value is 1, and described M value is 1.

4. feed circuit of radio frequency power amplifier as claimed in claim 1 or 2 is characterized in that, is connected with welding manner or circuit mode of printing between second end of described first microstrip line and first end of second microstrip line.

5. feed circuit of radio frequency power amplifier as claimed in claim 1 or 2, it is characterized in that, when second end of described first microstrip line was connected with first end of the 3rd microstrip line, second end of described first microstrip line was connected with welding manner or circuit mode of printing with first end of the 3rd microstrip line.

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