High-frequency choking coil multiplexing inter-stage matching circuit suitable for power amplifier chip and design method of high-frequency choking coil multiplexing inter-stage matching circuit

Abstract

The invention discloses a high-frequency choking coil multiplexing interstage matching circuit suitable for a power amplifier chip and a design method of the high-frequency choking coil multiplexing interstage matching circuit, which are applied to the field of wireless communication and aim at the technical defects of large insertion loss, large size or poor matching effect of the existing design scheme of the high-power, high-gain and high-integration power amplifier chip interstage matching circuit. The invention provides an inter-stage matching method for constructing an L-shaped high-pass filter aiming at small-difference port impedance and a segmented multiplexing radio frequency choking coil, and the defects of two traditional design methods are effectively avoided while the problem of small-difference port impedance matching is solved.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication, and particularly relates to a matching circuit and its design technology. Background Art

[0002] With the progress and development of science and technology, wireless communication technology has played a huge role in various production activities of people. Among them, the radio frequency microwave power amplifier chip, as one of the core components of the radio frequency front end of modern wireless communication systems, is also a key component restricting the system performance and technical level. In the field of wireless communication technology, it is necessary to use a power amplifier chip to transmit the modulated signal in a large power form, and this emission specification requirement is determined by various independent wireless communication protocol standards, including emission frequency, bandwidth, load, emission power, efficiency, linearity, etc. These specification requirements are the performance requirements for the radio frequency microwave power amplifier chip.

[0003] Among them, due to the increasingly urgent requirements for the power characteristics of the radio frequency front end in modern cutting-edge wireless communication systems such as 5G mobile communication, etc., the matching characteristics of the power amplifier chip have been the persistent pursuit of designers. Common design methods such as multi-stage LC matching and microstrip line matching have their own advantages, but their high insertion loss and large size characteristics make them inadequate in the field of power amplifier chip design. Especially in the field of high-power, high-gain, multi-stage cascaded power amplifier chip design, they have a common feature, that is, multiple triodes need to be connected in parallel at the output stage and the drive stage to achieve high power, which will result in a small difference between the output and input impedances of the two-stage amplifier circuit, causing their positions on the Smith chart to be very close, as Figure 1 shown. This poses a challenge to the design of conventional L-type matching circuits. For example, when using a high-pass filter structure, small inductors and large capacitors are required, and the presence of an indispensable radio frequency choke coil makes the design and layout difficulty of this inter-stage matching circuit double, especially in the limited design space on the power amplifier chip. Therefore, there is an urgent need for a brand-new low-insertion-loss, high-integration inter-stage matching network circuit design architecture and method, which also has the characteristics of simplicity, generality, and applicability to power amplifier chip design, and has considerable scientific research and commercial application value.

[0004] Existing designs generally use two methods to solve this problem, that is, to use a complex band-pass filter structure matching circuit design or a non-matching circuit design, as Figure 2 shown.

[0005] The disadvantages of the existing technology are: the matching effect of the complex band-pass filter structure is good, but it occupies a large MMIC DIE area of the chip, bringing a greater impact on the layout of other circuit modules including the later production cost; although the latter effectively saves the chip area, the matching effect is relatively poor, and it is difficult to guarantee the overall performance of the power amplifier. Summary of the Invention

[0006] To solve the above technical problems, the present invention proposes a high-frequency choke coil multiplexing inter-stage matching circuit applicable to a power amplifier chip and a design method thereof. By adopting an inter-stage matching method of segmentally multiplexing a radio frequency choke coil to construct an L-type high-pass filter for small-difference port impedances, the problem of small-difference port impedance matching is solved.

[0007] One of the technical solutions adopted by the present invention is: a high-frequency choke coil multiplexing inter-stage matching circuit applicable to a power amplifier chip, including a driving stage, an output stage, and a capacitor connected in series between the driving stage and the output stage. The radio frequency choke coil for powering the driving stage is divided into two parts, and a bypass capacitor grounded is connected between these two parts of the radio frequency choke coil. One part of the radio frequency choke coil directly connected to the driving stage is used as a small inductor of the matching circuit to participate in the matching, and the other part of the radio frequency choke coil is used to provide DC power supply for the driving stage.

[0008] Another technical solution adopted by the present invention is: a design method of a high-frequency choke coil multiplexing inter-stage matching circuit applicable to a power amplifier chip, including:

[0009] S1. Simulate and obtain the output impedance of the pre-stage power amplifier circuit;

[0010] S2. Simulate and obtain the input impedance of the post-stage power amplifier circuit;

[0011] S3. Based on ADS, design and build a basic LC high-pass filter structure;

[0012] S4. Combine the on-chip microstrip line part of the power amplifier MMIC DIE to calculate the length of the high-frequency choke coil that needs to be multiplexed;

[0013] S5. Simulate and obtain the self-resonant frequency of the stub circuit composed of the microstrip line and the chip capacitor;

[0014] S6. Determine the chip capacitor model, and then perform co-simulation to observe the matching effect. If the matching effect is achieved, end; otherwise, optimize the initial device values and re-perform co-simulation.

[0015] Advantages of the present invention: In view of the technical defects of large insertion loss, large volume or poor matching effect existing in the conventional inter-stage matching circuit design for high-power, high-gain and high-integration power amplifier chips, the present invention proposes an inter-stage matching method for constructing an L-shaped high-pass filter by segmentally multiplexing radio frequency chokes for small-difference port impedance, which solves the problem of small-difference port impedance matching and effectively avoids the disadvantages of two conventional design methods. Specifically, the matching method of constructing an L-shaped high-pass filter by segmentally multiplexing radio frequency chokes proposed by the present invention effectively saves the addition of inevitable inductors in the band-pass filter, effectively reduces the space occupied by the inter-stage matching circuit, and saves the chip design area and cost. Moreover, the matching method of constructing an L-shaped high-pass filter by segmentally multiplexing radio frequency chokes proposed by the present invention can effectively improve the inter-stage matching effect of the circuit, enabling the radio frequency signal to be transmitted to the subsequent stage circuit with less reflection, and improving the overall gain, efficiency and linearity characteristics of the power amplifier. At the same time, the present invention is also suitable for the design and application of power amplifier modules, with the characteristics of simplicity and generality, and has considerable scientific research and commercial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the distribution of common small-difference inter-stage impedance on the Smith chart and the conventional L-shaped matching circuit;

[0017] Figure 2 is the design of the conventional complex band-pass filter structure matching circuit or the non-matching circuit;

[0018] Figure 3 is the schematic diagram of the principle of the radio frequency choke segmental multiplexing inter-stage matching technology;

[0019] Figure 4 is the simulation diagram of the radio frequency choke segmental multiplexing inter-stage matching circuit;

[0020] Figure 5 is the design method flow of the radio frequency choke segmental multiplexing inter-stage matching circuit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] To facilitate the understanding of the technical content of the present invention by those skilled in the art, the content of the present invention will be further explained below with reference to the drawings.

[0022] In view of the technical defects of large insertion loss, large volume or poor matching effect existing in the conventional inter-stage matching circuit design for high-power, high-gain and high-integration power amplifier chips, the present invention proposes an inter-stage matching method for constructing an L-shaped high-pass filter by segmentally multiplexing radio frequency chokes for small-difference port impedance, which solves the problem of small-difference port impedance matching and effectively avoids the disadvantages of two conventional design methods.

[0023] The schematic diagram of the inter-stage matching circuit is as Figure 3As shown. Generally, the most ideal non - output matching circuit for a power amplifier is a high - pass filter structure. This is mainly because the series capacitor can serve as the input DC - blocking capacitor for the next - stage amplifier circuit. However, since the input - port impedance of the output stage of this chip is close to the output - port impedance of the driver stage, if a high - pass filter is used, it requires a large capacitor in combination with a small inductor, as Figure 1 shown; Therefore, the present invention proposes to use a part of the radio - frequency choke coil for power - supplying the driver stage as the small inductor in the matching circuit to participate in the matching, and the remaining part serves as the radio - frequency choke coil for providing DC power supply for the driver stage. The two parts of the microstrip line are isolated by a bypass - capacitor branch. This bypass - capacitor branch is constructed as a series - resonance circuit for the fundamental wave, and the port impedance at its connection with the microstrip line is approximately 0, which is equivalent to constructing a grounding effect for the fundamental wave, thereby forming the grounded part of the small inductor in this high - pass filter. The equivalent circuit diagram is as Figure 3 shown.

[0024] Using the small - signal simulation control S - PARAMETERS in ADS to verify as Figure 4 shown, the matching circuit using the segmented - multiplexing design of the radio - frequency choke coil and the matching circuit of the equivalent high - pass filter structure achieve 100% coincidence of the S - parameter performance curves. It can be seen that the performance achieved by the matching circuit using the segmented - multiplexing design of the radio - frequency choke coil and the matching circuit of the equivalent high - pass filter structure is exactly the same, which proves that the segmented - multiplexing technology of the radio - frequency choke coil proposed by the present invention can theoretically replace the conventional high - pass filter - structure matching circuit for the design of the inter - stage matching circuit of the power amplifier.

[0025] Figure 4 where freq represents frequency and GHz is the unit of frequency.

[0026] The present invention also proposes the design method of this high - frequency choke - coil multiplexing inter - stage matching circuit, as Figure 5 shown.

[0027] The design method of the present invention includes the following steps:

[0028] The first step: It is necessary to simulate and obtain the output impedance of the pre - stage power - amplifier circuit; the pre - stage power - amplifier circuit here corresponds to Figure 3 the driver stage in

[0029] The second step: Sequentially simulate and obtain the input impedance of the post - stage power - amplifier circuit; the post - stage power - amplifier circuit here corresponds to Figure 3 the output stage in

[0030] The third step: It is necessary to design and build a basic LC high - pass filter structure based on ADS; this high - pass filter is designed with a single - stage LC structure. Starting from the input port (i.e., Figure 4 Zsource in Figure 4The Zload in it). The input port impedance is the conjugate value of the output impedance of the pre-stage power amplifier circuit, and the output port impedance is the original value of the input impedance of the post-stage power amplifier circuit. Based on ADS, the exact inductance value and capacitance value of this structure can be simulated.

[0031] Step 4: Combine the on-chip microstrip line part of the power amplifier MMIC DIE to calculate the length of the high-frequency choke coil that needs to be reused, that is, the length of the small inductor part for matching; based on ADS, the inductance value of the microstrip line itself on the MMIC DIE can be simulated. Subtract the inductance value simulated in the third step above from this inductance value to obtain the inductance value that still needs to be provided by the high-frequency choke coil, and then simulate and convert this inductance value into the required choke coil length value.

[0032] Step 5: Based on the length of the high-frequency choke coil that needs to be reused calculated in the fourth step, simulate the self-resonant frequency of the series resonant circuit for the fundamental wave composed of the microstrip line as the small inductor and the chip capacitor as the bypass capacitor;

[0033] Step 6: Determine the type of chip capacitor with the best grounding effect according to the self-resonant frequency, and then perform joint simulation to observe the matching effect and evaluate whether the power amplifier has achieved the expected matching characteristics and power characteristics, such as the S of the power amplifier 21 If the expected gain characteristic is achieved and the output power reaches the expected requirement, the design is completed. Taking the power amplifier of the Beidou satellite communication terminal as an example, the gain of the last two-stage amplification circuits reaches 26 dB and the output power reaches 5 W under the connection of this inter-stage matching circuit; if not, optimize the initial device values. If it has been achieved, the design ends.

[0034] Optimize the initial device values, specifically: use the optimization tool of ADS to continuously traverse the series capacitance, the length of the off-chip microstrip line, and the chip capacitor value, and simulate the overall performance of the power amplifier after optimization. If the expected matching characteristics and power characteristics are achieved, the design is completed.

[0035] Those of ordinary skill in the art will realize that the embodiments described herein are to assist the reader in understanding the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A high-frequency choke coil multiplexing inter-stage matching circuit applicable to a power amplifier chip, characterized in that It includes a driver stage, an output stage, and a capacitor connected in series between the driver stage and the output stage. The RF choke used to supply power to the driver stage is divided into two parts, and a bypass capacitor grounded is connected between these two parts of the RF choke. One part of the RF choke directly connected to the driver stage participates in matching as a small inductor of the matching circuit, and the other part of the RF choke is used to provide DC power supply to the driver stage.

2. The high-frequency choke coil multiplexing inter-stage matching circuit applicable to the power amplifier chip according to claim 1, wherein The port impedance at the connection of the bypass capacitor and the RF choke is 0.

3. A design method for a high-frequency choke coil multiplexing inter-stage matching circuit applicable to a power amplifier chip, characterized in that, It includes: S1. Simulate to obtain the output impedance of the driver stage; S2. Simulate to obtain the input impedance of the output stage; S3. Based on the output impedance of the driver stage obtained in step S1 and the input impedance of the output stage obtained in step S2, design and build a basic LC high-pass filter structure based on ADS; S4. Combine with the on-chip microstrip line part of the power amplifier MMIC DIE to calculate the length of the microstrip line participating in matching as a small inductor of the matching circuit; S5. Simulate to obtain the self-resonant frequency of the stub circuit composed of the microstrip line obtained in step S4 and the chip capacitor used as the bypass capacitor; S6. Determine the model of the chip capacitor described in step S5 according to the self-resonant frequency obtained in step S5.

4. A design method of a high-frequency choke coil multiplexing inter-stage matching circuit applicable to a power amplifier chip according to claim 3, characterized in that, The LC high-pass filter structure built in step S3 includes: taking the output impedance of the driver stage obtained in step S1 as the input port, taking the input impedance of the output stage obtained in step S2 as the output port, and also including an inductor connected in parallel with the input port, a capacitor connected in series with the input port, and this capacitor is also connected to the output port.

5. A design method of a high-frequency choke coil multiplexing inter-stage matching circuit applicable to a power amplifier chip according to claim 4, characterized in that, Step S3 also includes: obtaining the inductor value and capacitor value in the built LC high-pass filter structure through ADS simulation.

6. A design method of a high-frequency choke coil multiplexing inter-stage matching circuit applicable to a power amplifier chip according to claim 5, characterized in that After step S6, it also includes: through co-simulation, observe the matching effect. If it is evaluated that the power amplifier has achieved the expected matching characteristics and power characteristics, the design is completed; otherwise, use the optimization tool of ADS, and continuously traverse the series capacitor, microstrip line length, and chip capacitor value until the expected matching characteristics and power characteristics are achieved.

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