Linear radio frequency amplifier structure
By using the transistor substrate negative feedback structure and voltage divider resistor network in the RF amplifier, the transconductance of transistors is independently optimized, and the contradiction between low power consumption, low noise and high linearity in the prior art is solved, and the lowest noise and highest linearity of the RF amplifier are achieved.
Patent Information
- Application Number
- CN202411833942.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-05-02
AI Technical Summary
In the design, existing RF amplifiers need to compromise between low power consumption and high linearity, low noise and high linearity, and it is difficult to achieve the goals of low power consumption, low noise and high linearity at the same time.
The transistor substrate negative feedback structure is adopted, and the transconductance between transistor MT and AT is independently optimized through voltage-dividing resistors R0, R1, R2, and R3 to achieve the lowest noise and highest linearity of the amplifier.
While maintaining the basic amplification function, the circuit complexity and cost are reduced, and the highest linearity and lowest noise of the amplifier are achieved, which is suitable for the needs of small size, low cost and low power consumption.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electronic systems, and in particular to a linear radio frequency amplifier structure. Background Art
[0002] Whether it is communication, radar, navigation, electronic countermeasure system, or other electronic transceiver system, low-cost, miniaturized, low-power, low-noise, and high-linearity amplifiers are required. Among them, low cost, miniaturization, and low power consumption are the eternal themes of the development of electronic systems. Low noise is conducive to improving the receiving sensitivity of the system and expanding the effective receiving range. High linearity is conducive to improving the system's anti-interference ability and survivability in complex electromagnetic environments. Especially in some special application scenarios, such as civilian wearable devices, military satellite navigation, electronic countermeasures, etc., the electromagnetic environment is very harsh, and higher requirements are placed on electronic systems.
[0003] With the rapid development of the Internet of Things market, the number and market share of wearable electronic devices have also grown rapidly. The rise of consumer applications such as smart watches, smart bracelets, and wireless headphones has driven the popularity of the wearable market. Due to the small size of the module of wearable devices, the distance between the antenna and the human body is relatively close, and the human body is a conductor with a large volume compared to the size of the antenna. Therefore, wearable devices will be seriously affected by the human body, and at the same time, they will also be interfered by the surrounding electromagnetic environment, such as mobile phone signals. For the military satellite navigation and electronic countermeasure fields, this problem is even more prominent. Because in the electronic warfare environment, the enemy will emit strong interference signals to interfere with our electronic equipment. Therefore, our electronic system needs to have a high anti-interference ability while maintaining high receiving sensitivity. At the same time, for most electronic systems, power consumption is also a prominent problem, especially for wearable devices. In summary, the technical bottleneck to meet the above application requirements is the need for a small size, low cost, low power consumption, low noise, and high linearity RF amplifier.
[0004] Under current technical conditions, there are two sets of contradictory design indicators for RF amplifiers, which need to be compromised in the design: 1) Low power consumption and high linearity: Generally, when high linearity is required, high linearity is achieved by sacrificing power consumption; when power consumption constraints are stronger, linearity can only be sacrificed. 2) Low noise and high linearity: Generally, the linearity and noise factor of low-noise amplifiers cannot be optimized at the same time. These two sets of contradictions have become technical bottlenecks in the design and application of RF amplifiers.
[0005] Therefore, there is an urgent need for a linear RF amplifier structure with low power consumption, low noise and high linearity. Summary of the invention
[0006] The purpose of the present invention is to provide a linear radio frequency amplifier structure, which can solve the deficiencies in the prior art and improve the linearity of the amplifier without deteriorating power consumption and noise, while reducing the chip size and reducing the chip cost.
[0007] To achieve the above object, the present invention adopts the following technical solutions:
[0008] A linear radio frequency amplifier structure includes a transistor MT, a transistor AT, a resistor R0, a resistor R1, a resistor R2 and a resistor R3.
[0009] The gate of the transistor MT is connected to the gate of the transistor AT, the drain of the transistor MT is connected to the drain of the transistor AT, and the source of the transistor MT is connected to the source of the transistor AT.
[0010] The drain of the transistor MT is connected to the first end of the resistor R1, the second end of the resistor R1 is connected to the first end of the resistor R0, and the second end of the resistor R0 is connected to the source of the transistor MT; the drain of the transistor AT is connected to the first end of the resistor R2, the second end of the resistor R2 is connected to the first end of the resistor R3, and the second end of the resistor R3 is connected to the source of the transistor AT.
[0011] A common node between the resistor R0 and the resistor R1 is connected to the substrate potential of the transistor MT; a common node between the resistor R2 and the resistor R3 is connected to the substrate potential of the transistor AT.
[0012] As a further improvement of the above technical solution, the resistor R0, the resistor R1, the resistor R2 and the resistor R3 are all voltage-dividing resistors.
[0013] As a further improvement of the above technical solution, the substrate voltage of the transistor MT is generated by the voltage divider resistor R1 and the resistor R0 between the drain of the transistor MT and the source of the transistor MT; the substrate voltage of the transistor MT needs to be smaller than its turn-on voltage.
[0014] As a further improvement of the above technical solution, the substrate voltage of the transistor AT is generated by the voltage divider resistor R2 and the resistor R3 between the drain of the transistor AT and the source of the transistor AT; the substrate voltage of the transistor AT needs to be smaller than its turn-on voltage.
[0015] As a further improvement of the above technical solution, the transistor MT and the transistor AT can be NMOS transistors or P-MOS transistors at the same time.
[0016] As a further improvement of the above technical solution, the linear RF amplifier structure also includes an inductor Ls; the first end of the inductor Ls is respectively connected to the second end of the resistor R0 and the second end of the resistor R3; when the transistor MT and the transistor AT are both NMOS tubes, the second end of the inductor Ls is grounded; when the transistor MT and the transistor AT are both PMOS tubes, the second end of the inductor Ls is connected to the power supply.
[0017] Compared with the prior art, the advantages of the present invention are:
[0018] The present invention adopts the input transistor substrate negative feedback structure, which can eliminate the requirements of multi-path bias and multiple DC blocking capacitors in the traditional multi-gate transconductance compensation amplifier while maintaining the basic amplification function, and only requires one DC blocking capacitor, which greatly reduces the circuit complexity, so that the advanced MOS process can be used to achieve low cost. At the same time, by adjusting the resistance values of resistors R0, R1, R2 and R3, the transconductance of transistors MT and AT can be independently optimized, thereby achieving the optimal goal of the lowest noise and the highest linearity of the amplifier. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 It is a schematic diagram of the circuit structure of a traditional multi-gate transconductance compensation amplifier;
[0020] Figure 2 is the schematic diagram of a basic amplifier;
[0021] Figure 3 It is the schematic diagram of an amplifier with negative feedback;
[0022] Figure 4 When the input is DX d Schematic diagram of an amplifier with negative feedback when ;
[0023] Figure 5 This is the schematic diagram of the traditional resistor negative feedback circuit;
[0024] Figure 6 It is a circuit schematic diagram of the linear radio frequency amplifier in the present invention.
[0025] Figure 7 is another circuit schematic diagram of the linear radio frequency amplifier in the present invention;
[0026] Figure 8 It is a noise coefficient and linearity index curve diagram of the linear radio frequency amplifier in the present invention. DETAILED DESCRIPTION
[0027] The present invention will be further described below in conjunction with the accompanying drawings:
[0028] The traditional multi-gate transconductance compensation amplifier circuit structure is as follows Figure 1As shown in the figure, MT / AT is the amplifier transistor, C1 / C2 is the input DC blocking capacitor. In the operating frequency range of MHz to GHz, the capacitance of this capacitor is relatively large, occupying the main chip area and cost. To improve the linearity of the amplifier, MT and AT use different bias voltages V GS and V GS -V shift To provide different transconductance values, these transconductance values compensate each other, thereby greatly improving the linearity of the amplifier. In the traditional multi-gate transconductance compensation low noise amplifier structure, in order to provide different transconductance values, transistors MT and AT require different bias voltages V GS and V GS -V shift At the same time, different DC blocking capacitors C1 and C2 are required to ensure that different transistors MT and AT can have independent bias voltages. If better linearity is required, more transistors with different bias voltages are needed to compensate together, which means more bias operating points and DC blocking capacitors are needed, greatly increasing the circuit complexity and cost. In addition, traditional resistive negative feedback requires connecting a resistor from the output end to the input end. Due to the existence of transistors with different bias voltages, multiple feedback resistors are required to improve linearity, increasing the complexity of the circuit.
[0029] For Figure 2 As for the basic amplifier shown in the figure, due to its certain nonlinearity, when the input is X d When X O =AX d +X D , where X D It is the harmonic distortion signal generated by nonlinearity. Nonlinear distortion is manifested as waveform distortion in the time domain and as harmonic generation in the frequency domain, that is, it will generate new harmonic components that are not present in the input signal. d ), the same output (AX d ) under the condition that the generated X D The smaller it is, the better the linearity of the amplifier.
[0030] Resistor negative feedback is usually used in low noise amplifier structures to improve the linearity of the amplifier. The basic principle of an amplifier with negative feedback is as follows: Figure 3 As shown. Figure 3 In the equation, A is the open-loop gain of the amplifier, and F is the feedback factor. Then the closed-loop gain is:
[0031] A F =A / (1+AF)=A / D
[0032] In the above formula, D=1+AF.
[0033] When the input is DX dWhen the negative feedback amplifier is Figure 4 As shown by Figure 4 The following formula can be obtained:
[0034]
[0035] Depend on Figure 4 From the above formula, we can see that when amplifier A has the same input and the same distortion, the total output distortion is reduced by D times after adding feedback. It can be seen that negative feedback has a significant effect on improving linearity.
[0036] Traditional resistor negative feedback circuit such as Figure 5 As shown. Figure 5 In the figure, T is the amplifier transistor, R c is the output load, R b1 and R b2 is the feedback resistor. This circuit improves linearity through resistor negative feedback.
[0037] From the above content, it can be seen that the traditional multi-gate transconductance compensation amplifier uses multi-stage resistor negative feedback to achieve high gain and high linearity of the amplifier. The disadvantages of this type of amplifier are complex circuits and high costs.
[0038] like Figure 6 and Figure 7 The schematic diagram of the linear RF amplifier structure of the present invention is shown, and the linear RF amplifier includes a transistor MT, a transistor AT, a resistor R0, a resistor R1, a resistor R2 and a resistor R3; the gate of the transistor MT is connected to the gate of the transistor AT, the drain of the transistor MT is connected to the drain of the transistor AT, and the source of the transistor MT is connected to the source of the transistor AT.
[0039] The drain of the transistor MT is connected to the first end of the resistor R1, the second end of the resistor R1 is connected to the first end of the resistor R0, the second end of the resistor R0 is connected to the source of the transistor MT, and the common node of the resistor R0 and the resistor R1 is connected to the substrate of the transistor MT; the drain of the transistor AT is connected to the first end of the resistor R2, the second end of the resistor R2 is connected to the first end of the resistor R3, the second end of the resistor R3 is connected to the source of the transistor AT, and the common node of the resistor R2 and the resistor R3 is connected to the substrate of the transistor AT.
[0040] The resistor R1 and the resistor R0 are connected to the drain and source of the transistor MT respectively, and the common node of the resistor R1 and the resistor R0 is connected to the substrate of the transistor MT, thereby forming a negative feedback loop of the transistor MT. From the drain of the transistor MT to the source of the transistor MT, an appropriate feedback substrate voltage is generated for the transistor MT through the voltage divider network R0 and R1.
[0041] The resistor R2 and the resistor R3 are connected to the drain and source of the transistor AT respectively, and the common node of the resistor R2 and the resistor R3 is connected to the substrate of the transistor AT, thereby forming a negative feedback loop of the transistor AT. From the drain of the transistor AT to the source of the transistor AT, an appropriate feedback substrate voltage is generated for the transistor AT through the voltage divider network R2 and R3.
[0042] The present invention adopts a transistor substrate negative feedback structure, which only requires one DC blocking capacitor, greatly reduces the circuit complexity, and can adopt advanced MOS technology to achieve low cost; by adjusting the values of R0, R1, R2, and R3, the transconductance of transistors MT and AT can be independently optimized to achieve the optimal goal of the lowest noise and the highest linearity of the amplifier. Specifically, by adjusting the nominal values of the resistors R1 and R0, the transconductance of transistor MT can be independently adjusted; by adjusting the nominal values of the resistors R2 and R3, the transconductance of transistor AT can be independently adjusted; because the transconductance of each transistor can be adjusted independently, it is convenient to compensate for the equivalent input transconductance of the amplifier and improve the linearity of the amplifier.
[0043] The substrate voltage of the transistor MT and the transistor AT should not exceed their turn-on voltage, so as to avoid causing unnecessary current to flow into the substrate and affect the normal operation of the transistor in the amplification state. In addition, the design reduces circuit complexity and cost by eliminating the need for multiple bias and DC blocking capacitors.
[0044] Specifically, the negative feedback introduced in this way can effectively reduce the nonlinear distortion of the amplifier. When the output signal VOUT changes, it will affect the substrate voltage of the two transistors through the voltage divider network composed of resistors R0 and R1, and resistors R2 and R3.
[0045] for Figure 6 For the circuit shown, the substrate voltage of transistor MT is:
[0046]
[0047] The substrate voltage of transistor AT is:
[0048]
[0049] From the above two formulas, we can see that as the output voltage changes, the substrate voltage of the transistor will also change accordingly, thereby changing the operating points of transistor MT and transistor AT. This change can compensate for the change in transistor transconductance caused by the input signal, thereby reducing nonlinear distortion. In addition, such a negative feedback structure also improves the overall stability of the amplifier. Because negative feedback reduces the gain, the system is more stable and less prone to oscillation. At the same time, it also increases the circuit's ability to resist parameter drift, such as the effects of temperature changes or other external interference. In practical applications, this helps ensure that the amplifier maintains good performance characteristics throughout the entire operating range. This negative feedback not only improves linearity, but also simplifies circuit design.
[0050] Traditional multi-gate transconductance compensation amplifiers usually require complex bias networks and multiple DC blocking capacitors to achieve similar effects, but the linear RF amplifier described in the present invention achieves the same goal through simple resistor voltage division and negative feedback, reducing circuit complexity and cost. In short, by connecting the output end to the transistor substrate to form a negative feedback loop, the RF amplifier can significantly improve its linearity while ensuring the basic amplification function, and has lower cost and a simpler structure. This is very beneficial for applications that seek high-efficiency, low-cost solutions.
[0051] As a further improvement of the above technical solution, the linear RF amplifier structure also includes an inductor Ls; the first end of the inductor Ls is respectively connected to the second end of the resistor R0 and the second end of the resistor R3; when the transistor MT and the transistor AT are both NMOS, the second end of the inductor Ls is grounded; when the transistor MT and the transistor AT are both PMOS, the second end of the inductor Ls is connected to the power supply; the inductor Ls helps to stabilize the circuit and optimize its frequency response and impedance matching.
[0052] As a further improvement of the above technical solution, the transistor MT and the transistor AT can both be NMOS or P-MOS tubes, which simplifies the complex bias network and DC blocking capacitors required in the traditional multi-gate transconductance compensation amplifier. This design allows the use of advanced MOS processes to achieve the optimal goals of low cost, lowest noise and highest linearity.
[0053] The working principle of the linear RF amplifier structure described in the present invention is:
[0054] Figure 6 and Figure 7 The substrate voltage of the transistor MT is generated by the voltage dividing resistor R1 and the voltage dividing resistor R0 from the drain of the transistor MT to the source of the transistor MT, and the substrate voltage of the transistor AT is generated by the voltage dividing resistor R2 and the voltage dividing resistor R3 from the drain of the transistor AT to the source of the transistor AT.
[0055] for Figure 6 , assuming that the output signal is VOUT, the substrate voltage of transistor MT is VOUT×R0 / (R1+R0), and the substrate voltage of transistor AT is VOUT×R3 / (R2+R3). By adjusting the values of resistors R0, R1, R2 and R3, the substrate voltages of transistor MT and transistor AT are also different, thereby forming different substrate transconductances, so that the equivalent input transconductance is effectively compensated. In addition, the resistive negative feedback structure output to the substrate can also effectively improve the linearity of the overall amplifier, so the linearity of the amplifier is much higher than that of the traditional structure. What needs to be noted in this circuit is: Since the excessively high substrate voltage of the transistor will cause additional current to flow into the substrate, it is necessary to note that the substrate voltage of the transistor must not be higher than the turn-on voltage of the transistor, and the transistor can still work in a normal amplification state at this time.
[0056] In order to improve linearity, traditional amplifiers often use the more expensive germanium-silicon process or gallium arsenide process, but this structure can use the relatively cheap standard CMOS process to achieve high linearity. The cost of the standard CMOS process is about 60% of the cost of the germanium-silicon process and 20% of the gallium arsenide process.
[0057] like Figure 8 As shown, taking the application of GPS low noise amplifier as an example, in the 1.575G frequency band, the noise figure and linearity indicators (blue in the figure) of the amplifier using this structure are better than the same indicators of the traditional structure amplifier, among which the noise figure is about 0.1dB lower and the linearity indicator is improved by 0.5dB.
[0058] In summary, the present invention adopts the input transistor substrate negative feedback structure, which can eliminate the requirements of multi-path bias and multiple DC blocking capacitors in the traditional multi-gate transconductance compensation amplifier while maintaining the basic amplification function, greatly reducing the circuit complexity and cost, so that advanced MOS technology can be used to achieve low cost. At the same time, by adjusting the values of resistors R1, R0, R2, and R3, the transconductance of transistors AT and MT can be independently optimized, thereby achieving the optimal goal of the lowest noise and highest linearity of the amplifier.
[0059] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope of the claims of the present invention.
Claims
1. A linear radio frequency amplifier structure, characterized in that: The linear radio frequency amplifier structure includes: a transistor MT, a transistor AT, a resistor R0, a resistor R1, a resistor R2 and a resistor R3; The gate of the transistor MT is connected to the gate of the transistor AT, the drain of the transistor MT is connected to the drain of the transistor AT, and the source of the transistor MT is connected to the source of the transistor AT; The drain of the transistor MT is connected to the first end of the resistor R1, the second end of the resistor R1 is connected to the first end of the resistor R0, and the second end of the resistor R0 is connected to the source of the transistor MT; the drain of the transistor AT is connected to the first end of the resistor R2, the second end of the resistor R2 is connected to the first end of the resistor R3, and the second end of the resistor R3 is connected to the source of the transistor AT; A common node between the resistor R0 and the resistor R1 is connected to the substrate potential of the transistor MT; a common node between the resistor R2 and the resistor R3 is connected to the substrate potential of the transistor AT.
2. The linear RF amplifier structure according to claim 1, characterized in that: The resistor R0 , the resistor R1 , the resistor R2 , and the resistor R3 are all voltage-dividing resistors.
3. The linear RF amplifier structure according to claim 1 or 2, characterized in that: The substrate voltage of the transistor MT is generated by the voltage-dividing resistor R1 and the resistor R0 between the drain of the transistor MT and the source of the transistor MT; the substrate voltage of the transistor MT is less than its turn-on voltage.
4. The linear RF amplifier structure according to claim 1 or 2, characterized in that: The substrate voltage of the transistor AT is generated by the voltage-dividing resistor R2 and the resistor R3 between the drain of the transistor AT and the source of the transistor AT; the substrate voltage of the transistor AT is less than its turn-on voltage.
5. The linear RF amplifier structure according to claim 1, characterized in that: The transistor MT and the transistor AT are both NMOS transistors or P-MOS transistors.
6. The linear RF amplifier structure according to claim 1, characterized in that: The linear RF amplifier structure also includes an inductor Ls; The first end of the inductor Ls is connected to the second end of the resistor R0 and the second end of the resistor R3 respectively; when the transistor MT and the transistor AT are both NMOS tubes, the second end of the inductor Ls is grounded; when the transistor MT and the transistor AT are both PMOS tubes, the second end of the inductor Ls is connected to the power supply.