Transformer coupled broadband low noise amplifier and radio frequency chip

Abstract

The application provides a transformer coupling type wideband low-noise amplifier, which comprises an input matching circuit, an amplification circuit, an output wideband circuit, an input negative feedback circuit and an output protection circuit. The amplifier realizes the effects of expanding bandwidth, optimizing linearity and stability through the input negative feedback circuit, realizes input bandwidth expansion without additional noise through input matching, controls and improves the gain bandwidth of the output pole of the radio frequency signal through the inductance in the output wideband circuit, and realizes feedback optimization gain by combining the inductive coupling of the gate and the drain level of the amplifier transistor. On the basis of reducing the circuit area, the performance optimization of the low-noise amplifier is realized.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a transformer-coupled broadband low-noise amplifier and radio frequency chip. Background Technology

[0002] Low-noise amplifiers (LNAs) are core components in microwave radio frequency technology and wireless communication. Their primary function is to amplify weak signals received by an antenna with minimal additional noise, thus directly determining the sensitivity and signal processing quality of the receiving system. As modern wireless communication technology evolves towards multi-band and ultra-wideband technologies, broadband low-noise amplifiers have become a crucial technology supporting the implementation of related systems. They need to process wider signal bandwidths with lower power consumption to meet the communication needs of various scenarios.

[0003] Currently, there are five mainstream technical solutions for broadband low-noise amplifiers. Each solution has different structural characteristics, but all have significant drawbacks:

[0004] The common-source structure achieves broadband input matching through resistor, inductor negative feedback and filter termination. It has good noise performance potential and high gain, but it is difficult to balance gain, noise and matching. Negative feedback will degrade noise performance.

[0005] The input impedance of the common-gate structure is approximately 1 / g m While it is naturally easy to achieve impedance matching and has good stability, it suffers from high intrinsic noise, low gain, and high power consumption.

[0006] Noise cancellation technology combines common gate (main path) and common source (auxiliary path) to cancel the noise of common gate transistors by using the signal phase relationship. It can break through the noise limit of common gate structure and achieve a better noise and power trade-off. However, the circuit is complex, sensitive to process deviations, and may limit bandwidth.

[0007] Multi-stage matching or multi-resonant point matching uses multi-stage circuits to tune different center frequency combinations to form a broadband response. It can flexibly shape gain and bandwidth curves and has high performance potential, but it is difficult to design and requires a large number of inductors, which leads to a surge in cost and area.

[0008] Active or hybrid matching networks use active devices to form the matching network to replace passive inductors, which can save chip area and provide some gain, but will introduce additional noise and nonlinearity, sacrificing overall performance.

[0009] In summary, existing broadband low-noise amplifiers face multiple contradictions in terms of noise, bandwidth, linearity, and power consumption, which cannot fully meet the high-performance requirements of modern ultra-wideband wireless communication systems. Therefore, developing a broadband low-noise amplifier technology that can balance various performance indicators has become an urgent technical problem to be solved in this field. Summary of the Invention

[0010] This invention provides a transformer-coupled broadband low-noise amplifier and RF chip, aiming to solve the problem that existing broadband low-noise amplifiers are difficult to balance noise, bandwidth, linearity and power consumption.

[0011] To solve the above-mentioned technical problems, in a first aspect, the present invention provides a transformer-coupled broadband low-noise amplifier, comprising an input matching circuit, an amplification circuit, an output broadband circuit, an input negative feedback circuit, and an output protection circuit, wherein:

[0012] The input matching circuit is used to receive radio frequency signals and provide input impedance matching for the amplifier circuit.

[0013] The amplifier circuit is used to receive the radio frequency signal output by the input matching circuit through its input terminal, and after amplifying the radio frequency signal with low noise, output the radio frequency amplified signal through the output terminal of the amplifier circuit; the amplifier circuit includes a first transistor and a second transistor, the gate of the first transistor serves as the input terminal of the amplifier circuit, the drain of the second transistor serves as the output terminal of the amplifier circuit, and the drain of the first transistor is connected to the source of the second transistor.

[0014] The output broadband circuit is used to receive the radio frequency amplified signal through its input terminal, perform bandwidth gain on the radio frequency amplified signal, and realize the output through the output terminal of the output broadband circuit.

[0015] The input negative feedback circuit is connected to the input terminal of the amplifier circuit and the output broadband circuit, and is used to extend the bandwidth of the input matching impedance.

[0016] The output protection circuit is connected to the output terminal of the output broadband circuit and is used to provide electrostatic protection for the transformer-coupled broadband low-noise amplifier.

[0017] Furthermore, the input matching circuit includes a first inductor, a second inductor, a first capacitor, a second capacitor, a first diode, a second diode, a third diode, and a fourth diode, wherein:

[0018] The first end of the first inductor serves as the input end of the input matching circuit, and the second end of the first inductor is connected to the first end of the first capacitor.

[0019] The second terminal of the first capacitor is connected to the gate of the first transistor;

[0020] The first terminal of the second capacitor is connected to the second terminal of the first capacitor, and the second terminal of the second capacitor is connected to the source of the first transistor.

[0021] The first terminal of the second inductor is connected to the source of the first transistor, and the second terminal of the second inductor is grounded.

[0022] The anode of the first diode and the cathode of the second diode are respectively connected to the second terminal of the first capacitor, and the cathode of the first diode and the anode of the second diode are connected together and grounded;

[0023] The anode of the third diode and the cathode of the fourth diode are respectively connected to the second terminal of the first capacitor. The cathode of the third diode and the anode of the fourth diode are connected together and connected to the source of the first transistor.

[0024] Furthermore, the output broadband circuit includes a third inductor, a fourth inductor, a fifth inductor, and a third capacitor, wherein:

[0025] The first end of the third inductor is connected to the gate of the second transistor, and the second end of the third inductor is connected to an external power supply voltage.

[0026] The first end of the fourth inductor is connected to the first end of the fifth inductor, and the second end of the fourth inductor is connected to the second end of the third inductor; and the fourth inductor and the third inductor are coupled to each other.

[0027] The second terminal of the fifth inductor serves as the input terminal of the output broadband circuit;

[0028] The first terminal of the third capacitor is connected to the first terminal of the fifth inductor, and the second terminal of the third capacitor serves as the output terminal of the output broadband circuit.

[0029] Furthermore, the output broadband circuit also includes a first resistor and a fourth capacitor; the first end of the first resistor is connected to the first end of the third capacitor, and the second end of the first resistor is connected to the second end of the fourth inductor; the first end of the fourth capacitor is connected to the second end of the first resistor, and the second end of the fourth capacitor is connected to the second end of the third capacitor.

[0030] Furthermore, the input negative feedback circuit includes a second resistor, a third resistor, and a fifth capacitor, wherein:

[0031] The first end of the second resistor is connected to the input terminal of the amplifier circuit, and the second end of the second resistor is connected to the first end of the fifth capacitor.

[0032] The first end of the third resistor is connected to the input terminal of the amplifier circuit, and the second end of the third resistor is used to connect to the bias current source.

[0033] Furthermore, the output protection circuit includes a fifth diode and a sixth diode. The anode of the fifth diode is connected to the cathode of the sixth diode, the cathode of the fifth diode is connected to the anode of the sixth diode, and the cathode of the fifth diode is connected to the output terminal of the output broadband circuit. The anode of the fifth diode is grounded.

[0034] Furthermore, the transformer-coupled broadband low-noise amplifier also includes a sixth capacitor, the first terminal of which is connected to the second terminal of the third inductor, and the second terminal of the sixth capacitor is grounded.

[0035] Secondly, the present invention also provides a radio frequency chip, the radio frequency chip including the transformer-coupled broadband low-noise amplifier as described above.

[0036] The beneficial effects achieved by this invention are as follows: it proposes a transformer-coupled broadband low-noise amplifier. This amplifier achieves the effects of expanding bandwidth, optimizing linearity and stability through an input negative feedback circuit, expanding input bandwidth without additional noise through input matching, improving gain bandwidth by regulating the output pole of the RF signal through the inductor in the output broadband circuit, and achieving feedback optimization gain by combining the inductive coupling of the gate and drain stages of the amplifier transistor. This achieves performance optimization of the low-noise amplifier while reducing the circuit area. Attached Figure Description

[0037] The present invention will now be described in detail with reference to the accompanying drawings. The above and other aspects of the present invention will become clearer and more readily understood through the detailed description following the accompanying drawings. In the drawings:

[0038] Figure 1 This is a circuit diagram of a transformer-coupled broadband low-noise amplifier provided in an embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] Example 1

[0041] Please refer to Figure 1 , Figure 1 This is a circuit diagram of a transformer-coupled broadband low-noise amplifier 100 provided in an embodiment of the present invention. The transformer-coupled broadband low-noise amplifier 100 includes an input matching circuit 101, an amplification circuit 102, an output broadband circuit 103, an input negative feedback circuit 104, and an output protection circuit 105, wherein:

[0042] The input matching circuit 101 is used to receive the radio frequency signal RFin and to provide input impedance matching for the amplifier circuit 102.

[0043] The amplifier circuit 102 is used to receive the radio frequency signal output by the input matching circuit 101 through its input terminal, and after amplifying the radio frequency signal with low noise, output the amplified radio frequency signal through the output terminal of the amplifier circuit 102; the amplifier circuit 102 includes a first transistor M1 and a second transistor M2, the gate of the first transistor M1 serves as the input terminal of the amplifier circuit 102, the drain of the second transistor M2 serves as the output terminal of the amplifier circuit 102, and the drain of the first transistor M1 is connected to the source of the second transistor M2;

[0044] The output broadband circuit 103 is used to receive the radio frequency amplified signal through its input terminal, perform bandwidth gain on the radio frequency amplified signal, and realize the output of the radio frequency signal RFout through the output terminal of the output broadband circuit 103.

[0045] The input negative feedback circuit 104 is connected to the input terminal of the amplifier circuit 102 and the output broadband circuit 103. The input negative feedback circuit 104 is used to extend the bandwidth of the input matching impedance.

[0046] The output protection circuit 105 is connected to the output terminal of the output broadband circuit 103 and is used to provide electrostatic protection for the transformer-coupled broadband low-noise amplifier 100.

[0047] Specifically, in this embodiment of the invention, the input matching circuit 101 includes a first inductor L1, a second inductor L2, a first capacitor C1, a second capacitor C2, a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4, wherein:

[0048] The first end of the first inductor L1 serves as the input end of the input matching circuit 101, and the second end of the first inductor L1 is connected to the first end of the first capacitor C1.

[0049] The second terminal of the first capacitor C1 is connected to the gate of the first transistor M1;

[0050] The first terminal of the second capacitor C2 is connected to the second terminal of the first capacitor C1, and the second terminal of the second capacitor C2 is connected to the source of the first transistor M1.

[0051] The first terminal of the second inductor L2 is connected to the source of the first transistor M1, and the second terminal of the second inductor L2 is grounded.

[0052] The positive terminal of the first diode D1 and the negative terminal of the second diode D2 are respectively connected to the second terminal of the first capacitor C1, and the negative terminal of the first diode D1 and the positive terminal of the second diode D2 are connected to and grounded.

[0053] The positive terminal of the third diode D3 and the negative terminal of the fourth diode D4 are respectively connected to the second terminal of the first capacitor C1. The negative terminal of the third diode D3 and the positive terminal of the fourth diode D4 are connected to the source of the first transistor.

[0054] Based on the structure of the input matching circuit 101 as described above, this embodiment of the invention adds capacitors to the gate and source of the first transistor M1 to compensate for the input impedance, reduce the input series matching inductance value, and achieve the effect of reducing noise.

[0055] The output broadband circuit 103 includes a third inductor L3, a fourth inductor L4, a fifth inductor L5, and a third capacitor C3, wherein:

[0056] The first terminal of the third inductor L3 is connected to the gate of the second transistor M2, and the second terminal of the third inductor L3 is connected to the external power supply voltage VDDLNA.

[0057] The first end of the fourth inductor L4 is connected to the first end of the fifth inductor L5, and the second end of the fourth inductor L4 is connected to the second end of the third inductor L3; and the third inductor L3 and the fourth inductor L4 are coupled to each other.

[0058] The second terminal of the fifth inductor L5 serves as the input terminal of the output broadband circuit 103;

[0059] The first terminal of the third capacitor C3 is connected to the first terminal of the fifth inductor L5, and the second terminal of the third capacitor C3 serves as the output terminal of the output broadband circuit 103.

[0060] Based on the structure of the output broadband circuit 103, an inductor L3 is introduced into the gate of the second transistor M2 (common gate transistor) of the amplifier circuit 102. This adds a pair of conjugate poles and a pair of conjugate zeros to the output matching circuit. The introduction of the conjugate pole pair enables the circuit to generate an additional gain peak at high frequencies. Specifically, since poles near the imaginary axis play a dominant role in the frequency response, adjusting the inductance value of L3 to change the position of the conjugate pole pair can control the peak frequency of the new gain peak, making it continuously approach the main gain peak, thereby expanding the gain bandwidth of the circuit.

[0061] During implementation, the broadband gain achieved by adding a third inductor L3 to the gate of the second transistor M2 has significant ripple and poor gain flatness. To address this issue, the third inductor L3 can be appropriately increased to allow the conjugate pole pair to gradually move closer to the imaginary axis. With this setting, as the conjugate pole pair gradually converges with the original dominant pole, the distance between the two peak gains gradually decreases, thereby reducing gain ripple and optimizing gain flatness.

[0062] One end of the external power supply voltage VDDLNA is connected to the fourth inductor L4, and together with the fifth inductor L5, it would occupy a large area on the circuit layout without optimization. Therefore, in this embodiment of the invention, to reduce the circuit area, the third inductor L3 and the fourth inductor L4 are coupled in a transformer-coupled configuration. Transformer feedback technology is used to reduce the peak gain of the poles and improve the gain response frequency of the pole control technology. According to the equivalent small-signal circuit of the transformer coupling, during small-signal analysis, the transformer structure is modeled as three T-shaped inductors (L3, L4, L5). Due to the presence of the three inductors, the transfer function of the output broadband circuit 103 has two pairs of conjugate poles and one dominant pole. By adjusting the coupling coefficient k between the inductance value and the third inductor L3 and the fourth inductor L4, the peak gain frequency corresponding to the third inductor L3 is designed at the intermediate frequency, and the peak gain frequency introduced by the transformer structure is set at the high frequency, which can further expand the gain bandwidth and achieve a flat gain response.

[0063] Furthermore, the output broadband circuit 103 also includes a first resistor R1 and a fourth capacitor C4; the first end of the first resistor R1 is connected to the first end of the third capacitor C3, and the second end of the first resistor R1 is connected to the second end of the fourth inductor L4; the first end of the fourth capacitor C4 is connected to the second end of the first resistor R1, and the second end of the fourth capacitor C4 is connected to the second end of the third capacitor C3.

[0064] In practical applications, some RF systems require good gain flatness and good S22 scattering parameter performance. To further optimize gain flatness, setting the first resistor R1 can also make the S22 scattering parameters more convergent.

[0065] In this embodiment of the invention, the fourth capacitor C4 serves as the output DC blocking capacitor. The fourth capacitor C4 is connected in parallel between the output terminal of the entire transformer-coupled broadband low-noise amplifier 100 and the external power supply voltage VDDLNA. The main function of the fourth capacitor C4 is to optimize the gain flatness, making the S22 scattering parameters more convergent. Simultaneously, it can also optimize the linearity of the transformer-coupled broadband low-noise amplifier 100. Therefore, depending on the requirements of the applied RF system, the first resistor R1 and the fourth capacitor C4 can also be removed from the output broadband circuit 103.

[0066] The input negative feedback circuit 104 includes a second resistor R2, a third resistor R3, and a fifth capacitor C5, wherein:

[0067] The first end of the second resistor R2 is connected to the input terminal of the amplifier circuit 102, and the second end of the second resistor R2 is connected to the first end of the fifth capacitor C5.

[0068] The first end of the third resistor R3 is connected to the input terminal of the amplifier circuit 102, and the second end of the third resistor R3 is used to connect to the bias current source bias_cs;

[0069] The second terminal of the fifth capacitor C5 is connected to the first terminal of the fifth inductor L5.

[0070] In the input negative feedback circuit 104, the second resistor R2 serves as a feedback resistor for wideband input impedance matching, setting the real part of the input impedance to 50Ω, and also stabilizing the circuit gain. The fifth capacitor C5 serves as a feedback capacitor, used to block DC, preventing the DC potential of the second transistor M2 from affecting the gate bias of the first transistor M1, and together with the second resistor R2, forms the frequency response, compensating for gain roll-off, expanding bandwidth, and also optimizing high-frequency noise matching.

[0071] The output protection circuit 105 includes a fifth diode D5 and a sixth diode D6. The positive terminal of the fifth diode D5 is connected to the negative terminal of the sixth diode D6, the negative terminal of the fifth diode D5 is connected to the positive terminal of the sixth diode D6, and the negative terminal of the fifth diode D5 is connected to the output terminal of the output broadband circuit 103. The positive terminal of the fifth diode D5 is grounded.

[0072] like Figure 1 As shown, the transformer-coupled broadband low-noise amplifier 100 also includes a sixth capacitor C6. The first terminal of the sixth capacitor C6 is connected to the second terminal of the third inductor L3, and the second terminal of the sixth capacitor C6 is grounded. The sixth capacitor C6 serves to filter out power supply ripple and high-frequency noise, ensuring the effective operation of the output broadband circuit 103.

[0073] The beneficial effects achieved by this invention are as follows: it proposes a transformer-coupled broadband low-noise amplifier. This amplifier achieves the effects of expanding bandwidth, optimizing linearity and stability through an input negative feedback circuit, expanding input bandwidth without additional noise through input matching, improving gain bandwidth by regulating the output pole of the RF signal through the inductor in the output broadband circuit, and achieving feedback optimization gain by combining the inductive coupling of the gate and drain stages of the amplifier transistor. This achieves performance optimization of the low-noise amplifier while reducing the circuit area.

[0074] Example 2

[0075] The present invention also provides a radio frequency chip, the radio frequency chip comprising the transformer-coupled broadband low-noise amplifier as described above.

[0076] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0077] The embodiments of the present invention have been described above with reference to the accompanying drawings. The disclosed embodiments are merely preferred embodiments of the present invention. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many equivalent changes in form under the guidance of the present invention without departing from the spirit and scope of the claims. All such changes are within the protection scope of the present invention.

Claims

1. A transformer-coupled broadband low-noise amplifier, characterized in that, It includes an input matching circuit, an amplifier circuit, an output broadband circuit, an input negative feedback circuit, and an output protection circuit, wherein: The input matching circuit is used to receive radio frequency signals and provide input impedance matching for the amplifier circuit. The amplifier circuit is used to receive the radio frequency signal output by the input matching circuit through its input terminal, and after amplifying the radio frequency signal with low noise, output the amplified radio frequency signal through the output terminal of the amplifier circuit; the amplifier circuit includes a first transistor and a second transistor, the gate of the first transistor serves as the input terminal of the amplifier circuit, the drain of the second transistor serves as the output terminal of the amplifier circuit, the drain of the first transistor is connected to the source of the second transistor, and the source of the first transistor is connected to the input matching circuit; The output broadband circuit is used to receive the radio frequency amplified signal through its input terminal, perform bandwidth gain on the radio frequency amplified signal, and realize the output through the output terminal of the output broadband circuit. The input negative feedback circuit is connected to the input terminal of the amplifier circuit and the output broadband circuit, and is used to extend the bandwidth of the input matching impedance. The output protection circuit is connected to the output terminal of the output broadband circuit and is used to provide electrostatic protection for the transformer-coupled broadband low-noise amplifier. The output broadband circuit includes a third inductor, a fourth inductor, a fifth inductor, and a third capacitor, wherein: The first end of the third inductor is connected to the gate of the second transistor, and the second end of the third inductor is connected to an external power supply voltage. The first end of the fourth inductor is connected to the first end of the fifth inductor, and the second end of the fourth inductor is connected to the second end of the third inductor; and the fourth inductor and the third inductor are coupled to each other. The second terminal of the fifth inductor serves as the input terminal of the output broadband circuit; The first terminal of the third capacitor is connected to the first terminal of the fifth inductor, and the second terminal of the third capacitor serves as the output terminal of the output broadband circuit. The input negative feedback circuit includes a second resistor, a third resistor, and a fifth capacitor, wherein: The first end of the second resistor is connected to the input terminal of the amplifier circuit, and the second end of the second resistor is connected to the first end of the fifth capacitor. The first end of the third resistor is connected to the input terminal of the amplifier circuit, and the second end of the third resistor is used to connect to the bias current source. The second terminal of the fifth capacitor is connected to the first terminal of the fifth inductor.

2. The transformer-coupled broadband low-noise amplifier according to claim 1, characterized in that, The input matching circuit includes a first inductor, a second inductor, a first capacitor, a second capacitor, a first diode, a second diode, a third diode, and a fourth diode, wherein: The first end of the first inductor serves as the input end of the input matching circuit, and the second end of the first inductor is connected to the first end of the first capacitor. The second terminal of the first capacitor is connected to the gate of the first transistor; The first terminal of the second capacitor is connected to the second terminal of the first capacitor, and the second terminal of the second capacitor is connected to the source of the first transistor. The first terminal of the second inductor is connected to the source of the first transistor, and the second terminal of the second inductor is grounded. The anode of the first diode and the cathode of the second diode are respectively connected to the second terminal of the first capacitor, and the cathode of the first diode and the anode of the second diode are connected together and grounded; The anode of the third diode and the cathode of the fourth diode are respectively connected to the second terminal of the first capacitor. The cathode of the third diode and the anode of the fourth diode are connected together and connected to the source of the first transistor.

3. The transformer-coupled broadband low-noise amplifier according to claim 1, characterized in that, The output broadband circuit further includes a first resistor and a fourth capacitor; the first end of the first resistor is connected to the first end of the third capacitor, and the second end of the first resistor is connected to the second end of the fourth inductor; the first end of the fourth capacitor is connected to the second end of the first resistor, and the second end of the fourth capacitor is connected to the second end of the third capacitor.

4. The transformer-coupled broadband low-noise amplifier according to claim 1, characterized in that, The output protection circuit includes a fifth diode and a sixth diode. The positive terminal of the fifth diode is connected to the negative terminal of the sixth diode, and the negative terminal of the fifth diode is connected to the positive terminal of the sixth diode. The positive terminal of the fifth diode is connected to the output terminal of the output broadband circuit, and the negative terminal of the fifth diode is grounded.

5. The transformer-coupled broadband low-noise amplifier according to claim 1, characterized in that, The transformer-coupled broadband low-noise amplifier further includes a sixth capacitor, the first end of which is connected to the second end of the third inductor, and the second end of the sixth capacitor is grounded.

6. A radio frequency chip, characterized in that, The radio frequency chip includes a transformer-coupled broadband low-noise amplifier as described in any one of claims 1-5.

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