A method of designing a multi-stage amplifier based on couplers

Abstract

This invention discloses a multi-stage amplifier design method based on couplers. Specifically, a capacitor unit is connected after the output signal of each stage of the multi-stage amplifier. The amplitude and phase of the coupled signal output by the capacitor unit change with the power input to the multi-stage amplifier. Based on the amplitude and phase of the coupled signal output by the capacitor unit, the amplitude distortion and phase distortion of the corresponding amplifier circuit are obtained, thereby adjusting the components of the corresponding amplifier circuit to improve the amplitude compression and phase shift, and ultimately improving the overall amplitude and phase distortion of the multi-stage amplifier. This invention can significantly improve the efficiency of the overall circuit design.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit technology. Background Technology

[0002] GaAs HBT devices outperform FETs in power density, linearity, and current drive capability, making them ideal for designing high-power, high-efficiency, and high-linearity RF amplifiers. Furthermore, GaAs HBTs offer advantages in high power density, high gain, high linearity, and low phase noise. Their single-supply operation simplifies circuit design and implementation, making them highly suitable for high-linearity power amplifiers and similar circuits. Currently, GaAs HBT devices are the preferred choice for power amplifiers in mobile communication terminals.

[0003] When an amplifier is operating, as the RF input signal changes from a low-power signal to a high-power signal, the output signal experiences voltage or current saturation or cutoff. The amplifier's nonlinearity becomes increasingly pronounced, resulting in gain compression and phase shift. AM-AM (Amplitude Modulation-Amplitude Modulation) distortion describes the nonlinear relationship between the output signal power and the input signal power. As the RF input signal increases, the output power no longer increases linearly with the input power, resulting in gain compression, i.e., gain amplitude distortion. AM-PM (Amplitude Modulation-Phase Modulation) distortion describes the nonlinear relationship between the output signal phase and the input signal power. Under small signal input conditions, the output signal phase remains constant. However, as the input signal strength increases to a certain level, the output signal phase changes, i.e., gain phase distortion.

[0004] In power amplifier design, considering factors such as gain and output power, multi-stage circuits are typically employed. Given the differences in transistor area, bias conditions, and matching states across different stages, each stage will experience varying degrees of gain compression and phase distortion. Linearity determines the usable output power of the power amplifier chip. Improving AM-AM and AM-PM stages is the most direct and effective way to enhance linearity. Adjusting the bias point and interstage impedance can improve AM-AM and AM-PM stages to some extent, thereby increasing the overall circuit linearity and output power.

[0005] Traditional amplifier circuit design can only reflect the AM-AM and AM-PM characteristics of a circuit through the amplitude and phase of the overall circuit output power, failing to reflect the amplitude and phase distortion of each stage. Circuit design requires optimization of the overall circuit's bias and matching circuits, making the process somewhat haphazard and time-consuming. Summary of the Invention

[0006] Purpose of the invention: In order to solve the problems existing in the prior art, the present invention provides a multi-stage amplifier design method based on couplers.

[0007] Technical Solution: This invention provides a design method for a multi-stage amplifier based on a coupler. Specifically, a capacitor unit is connected after the output signal of each stage of the multi-stage amplifier. The amplitude and phase of the coupled signal output by the capacitor unit change with the power input to the multi-stage amplifier. The amplitude distortion and phase distortion of the corresponding amplifier circuit are obtained based on the amplitude and phase of the coupled signal output by the capacitor unit, thereby adjusting the components of the corresponding amplifier circuit to improve the amplitude compression and phase shift of the corresponding amplifier circuit, and thus improving the overall amplitude distortion and phase distortion of the multi-stage amplifier.

[0008] Furthermore, the capacitor unit comprises four capacitors connected in series.

[0009] Furthermore, the capacitor is a GaAs substrate MIM capacitor.

[0010] Beneficial effects:

[0011] 1. This invention observes the gain compression and phase distortion of each circuit stage by coupling circuit units, dynamically capturing the AM-AM and AM-PM trends of each stage. During the circuit optimization design process, based on the amplitude and phase distortion characteristics of each stage, the components of each stage are specifically adjusted to improve the amplitude and phase distortion of each stage, thereby improving the overall amplitude and phase distortion of the circuit. This can significantly improve the efficiency of the overall circuit design.

[0012] 2. All circuit units of the present invention are designed based on GaAs HBT process. This multi-stage amplifier design based on coupler can achieve monolithic integration, which promotes the simplification and miniaturization of monolithic microwave integrated circuit system applications. Attached Figure Description

[0013] Figure 1 This is a circuit diagram of a traditional GaAs HBT multi-stage amplifier circuit.

[0014] Figure 2 This is a schematic diagram illustrating the design process of an embodiment of the present invention. Detailed Implementation

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] This invention couples a small amount of energy out of the amplifier by connecting a series of small capacitors after each stage's output. Because the capacitance of the series capacitors is very small, the resulting equivalent capacitance is also very small. This coupling circuit unit presents a large impedance to the RF path, resulting in a very small RF signal output through the coupler that does not affect energy transfer in the RF path. The amplitude and phase characteristics of the signal output from the coupler reflect the amplitude and phase distortion of that stage of the circuit. During circuit design, based on the amplitude and phase distortion of each stage, circuit components are optimized specifically to more quickly improve the amplitude and phase distortion of each stage, thereby improving the overall amplitude and phase distortion characteristics of the circuit and significantly increasing the efficiency of the overall circuit design.

[0017] An embodiment of the present invention:

[0018] like Figure 1 The diagram shown is a traditional GaAs HBT multi-stage amplifier circuit; in this invention, a capacitor unit is connected after each stage of the amplifier circuit, as shown below. Figure 2 As shown, signal coupling circuit unit 1 couples the first stage output signal RFout1 of the multi-stage amplifier through a capacitor unit to obtain signal CPLout1; signal coupling circuit unit 2 couples the second stage output signal RFout2 of the multi-stage amplifier through a capacitor unit to obtain signal CPLout2.

[0019] Both signal coupling circuit unit 1 and signal coupling circuit unit 2 are circuit units based on GaAs HBT technology.

[0020] like Figure 2 As shown, signal coupling circuit unit 1 includes a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, and a fifth capacitor C5. The first capacitor C1 is connected to the first-stage RF output RFout1 of the amplifier circuit. The second capacitor C2 is connected to the first capacitor C1, the third capacitor C3 is connected to the second capacitor C2, the fourth capacitor C4 is connected to the third capacitor C3, and the fifth capacitor is connected to the fourth capacitor C4. The RF output coupling signal of the first-stage circuit is output through the fifth capacitor C5.

[0021] like Figure 2 As shown, signal coupling circuit unit 2 includes a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, and a tenth capacitor C10. The sixth capacitor C6 is connected to the second-stage RF output RFout2 of the amplifier circuit. The seventh capacitor C7 is connected to the sixth capacitor C6, the eighth capacitor C8 is connected to the seventh capacitor C7, the ninth capacitor C9 is connected to the eighth capacitor C8, and the tenth capacitor is connected to the ninth capacitor C9. The RF output coupling signal of the second-stage circuit is output through the tenth capacitor C10.

[0022] The first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6, the seventh capacitor C7, the eighth capacitor C8, the ninth capacitor C9, and the tenth capacitor C10 are all MIM capacitors on a GaAs substrate, such as... Figure 2 As shown, for MIM capacitors on GaAs substrates, the capacitance density is relatively small, and the capacitance value per unit area is relatively small.

[0023] The power detection circuit works as follows:

[0024] (1) The first stage RF output of the power amplifier circuit is RFout1, and a coupling circuit unit is connected in parallel at the RFout1 node. This coupling circuit unit is composed of capacitors C1, C2, C3, C4 and C5 connected in series. Due to the limitations of the manufacturing process, the area of ​​a single capacitor cannot be too small, so a series of capacitors are connected in series to obtain a very small capacitor. This coupling circuit unit 1 presents a large impedance to the first stage RF path of the circuit. The RF signal CPLout1 coupled from the pad of capacitor C5 is very small and does not affect the transmission of the RF path signal.

[0025] (2) The first stage RF output of the power amplifier circuit is RFout2, and a coupling circuit unit is connected in parallel at the RFout2 node. This coupling circuit unit is composed of capacitors C6, C7, C8, C9 and C10 connected in series. Due to the limitations of the manufacturing process, the area of ​​a single capacitor cannot be too small, so a series of capacitors are connected in series to obtain a very small capacitor. This coupling circuit unit 2 presents a large impedance to the second stage RF path of the circuit. The RF signal CPLout2 coupled from the pad of capacitor C10 is very small and does not affect the transmission of the RF path signal.

[0026] (3) As the input power RFI increases, observe the changes in amplitude and phase of the coupled RF signals CPLout1 and CPLout2, and dynamically capture the amplitude and phase change curves of the coupled signals CPLout1 and CPLout2 caused by the change in input power. The amplitude and phase changes of the coupled signals CPLout1 and CPLout2 caused by the change in input power can reflect the amplitude distortion and phase distortion of the first and second stages of the amplifier circuit. Optimize the circuit components of the first and second stages of the amplifier circuit to improve the amplitude compression and phase shift of each stage, thereby improving the amplitude distortion and phase distortion of the overall circuit.

[0027] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for designing a multi-stage amplifier based on a coupler, characterized in that: Specifically, a capacitor unit is connected after the output signal of each stage of the multi-stage amplifier circuit; the amplitude and phase of the coupled signal output by the capacitor unit change with the power input to the multi-stage amplifier; the amplitude distortion and phase distortion of the corresponding amplifier circuit are obtained based on the amplitude and phase of the coupled signal output by the capacitor unit, thereby adjusting the components of the corresponding amplifier circuit, improving the amplitude compression and phase shift of the corresponding amplifier circuit, and thus improving the overall amplitude distortion and phase distortion of the multi-stage amplifier. The specific working principle is as follows: The first stage RF output of the amplifier circuit is RFout1. A coupling circuit unit is connected in parallel at the RFout1 node. This coupling circuit unit is composed of capacitors C1, C2, C3, C4 and C5 connected in series. The second stage RF output of the amplifier circuit is RFout2. A coupling circuit unit is connected in parallel at the RFout2 node. This coupling circuit unit is composed of capacitors C6, C7, C8, C9 and C10 connected in series. As the input power RFI increases, the changes in amplitude and phase of the coupled RF signals CPLout1 and CPLout2 are observed. The amplitude and phase change curves of the coupled signals CPLout1 and CPLout2 caused by the change in input power are dynamically captured. The amplitude and phase changes of the coupled signals CPLout1 and CPLout2 caused by the change in input power can reflect the amplitude distortion and phase distortion of the first and second stages of the amplifier circuit. The circuit components of the first and second stages of the amplifier circuit are optimized to improve the amplitude compression and phase shift of each stage circuit, thereby improving the amplitude distortion and phase distortion of the overall circuit.

2. The multi-stage amplifier design method based on couplers according to claim 1, characterized in that: The capacitor unit comprises four capacitors connected in series.

3. The multi-stage amplifier design method based on couplers according to claim 2, characterized in that: The capacitor is a GaAs substrate MIM capacitor.

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