Improved cascode low-noise amplifier based on in-phase amplification

Abstract

The invention discloses an improved cascode low-noise amplifier based on in-phase amplification, which comprises a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a first transformer, a first inductor, a second inductor, a third inductor, a first resistor, a second resistor, a first transistor, a second transistor and a third transistor, wherein the first capacitor and the first transformer form an input matching network based on the transformer; the first transistor and the third transistor form a cascode low-noise amplifier; the first inductor is used as a source negative feedback inductor of the cascode low-noise amplifier; the first transistor, the second transistor and the third transistor form a current mirror structure; and the second inductor, the fourth capacitor, the third inductor and the fifth capacitor form an output matching network. According to the invention, the gain, the noise flatness, the application bandwidth and the input matching degree can be improved, and meanwhile, the chip area is reduced. The invention can be widely applied to the field of radio frequency integrated circuits.

Description

Technical Field

[0001] The invention relates to the field of radio frequency integrated circuits, and in particular to an improved common-source and common-gate low-noise amplifier based on in-phase amplification. Background Art

[0002] The millimeter wave band has shown broad application prospects in many fields such as communications and radar due to its high frequency, broadband and high-speed transmission characteristics. In recent years, the rapid development of wireless communication technology has put forward higher requirements on the performance of millimeter wave devices.

[0003] With the advancement of science and technology, especially in the field of wireless communication and radio frequency applications, signal reception and processing have become particularly important. Since the signal is often interfered by various external environments during transmission, the strength and quality of the signal are reduced. In order to overcome this problem, low noise amplifiers came into being. By adopting special design and circuit technology, it effectively reduces the introduction of noise and provides high gain and low distortion signal amplification.

[0004] At present, most of the traditional matching network structures used in low-noise amplifiers use a single-section LC for input impedance matching, but a single-section LC cannot meet the requirements of broadband matching; some solutions use multiple sections of LC for broadband matching. Although multiple sections of LC can meet the basic requirements of broadband input matching, it will cause a higher area occupancy rate and is prone to resonance, causing the circuit to self-excite. Summary of the invention

[0005] In view of this, in order to solve the technical problem that the existing low-noise amplifier cannot simultaneously meet the broadband matching and chip area requirements required by the scene, the present invention proposes an improved common-source common-gate low-noise amplifier based on in-phase amplification, which is composed of five parts: an input matching network, an output matching network, a DC bias current mirror structure, a voltage divider bias structure and a common-source common-gate amplifier, and specifically includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a first transformer, a first inductor, a second inductor, a third inductor, a first resistor, a second resistor, a first transistor, a second transistor and a third transistor, wherein:

[0006] The first capacitor and the first transformer constitute the key matching network of the present invention - a transformer-based input matching network, and the first capacitor is also used to isolate direct current;

[0007] The first transistor and the third transistor together form a common-source common-gate low-noise amplifier;

[0008] The bias circuit adopts an active bias circuit structure;

[0009] The first transistor, the second transistor and the third transistor together form a current mirror structure, which can generate a stable bias current, and the generated bias current can be controlled by the width and length of two transistors among the first transistor, the second transistor and the third transistor;

[0010] The first inductor is the source negative feedback inductor of the input stage common source and common gate amplifier;

[0011] The first capacitor is a DC blocking capacitor of the input stage to prevent the bias current from being shunted to the RF input port;

[0012] The second resistor is a voltage-dividing resistor, and the gate voltage of the third transistor can be adjusted by adjusting the resistance value thereof;

[0013] The first resistor can achieve temperature compensation, so that the bias current provided by the bias circuit is more stable;

[0014] The second capacitor and the third capacitor are used for filtering to prevent the inflow of radio frequency signals;

[0015] The second inductor is a choke inductor, which is used to prevent the RF signal from flowing to the power supply voltage VDD. Its value is generally 1.1V, and the second inductor also participates in the inter-stage matching;

[0016] The second inductor, the fourth capacitor, the third inductor and the fifth capacitor form a two-section LC output matching network, wherein the fifth capacitor is also used as a DC isolation capacitor of the output stage to isolate the influence of the DC component on the circuit.

[0017] Based on the above scheme, the present invention provides an improved common-source and common-gate low-noise amplifier based on in-phase amplification, which uses a transformer matching network to design the input stage matching of the entire low-noise amplifier, achieves higher return loss, lower noise flatness, and reduces signal loss caused by the input signal flowing to the bias path. Furthermore, by inverting the same-name ends of the coils in the transformer, in-phase amplification is achieved, thereby achieving gain superposition and improving gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a circuit structure diagram of an improved common-source common-gate low-noise amplifier based on in-phase amplification of the present invention;

[0019] Figure 2 This is a schematic diagram comparing the noise figure (NF) of a conventional low noise amplifier and an improved low noise amplifier;

[0020] Figure 3 This is a comparison diagram of the input return loss (S11) of the traditional low noise amplifier and the improved low noise amplifier;

[0021] Figure 4 This is a schematic diagram comparing the gain of a traditional low noise amplifier and an improved low noise amplifier;

[0022] Figure 5 It is a positive feedback schematic diagram based on a transformer;

[0023] Figure 6 This is a comparison diagram of the Kf of the traditional low noise amplifier and the improved low noise amplifier.

[0024] Figure symbols: C1, first capacitor; C2, second capacitor; C3, third capacitor; C4, fourth capacitor; C5, fifth capacitor; M1, first transistor; M2, second transistor; M3, third transistor; R1, first resistor; R2, second resistor; L1, first inductor; L2, second inductor; L3, third inductor; T1, first transformer. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] It should be noted that, for the convenience of description, only the parts related to the relevant invention are shown in the drawings. In the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0027] It should be understood that the "system", "device", "unit" and / or "module" used in this application is a method for distinguishing different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the word can be replaced by other expressions.

[0028] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "a kind" and / or "the" do not refer to the singular, but also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of clearly identified steps and elements, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements. The elements defined by the sentence "includes a..." do not exclude the existence of other identical elements in the process, method, commodity or device that includes the elements.

[0029] In the description of the embodiments of the present application, "plurality" means two or more than two. The following terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0030] In addition, flow charts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed accurately in order. On the contrary, the various steps may be processed in reverse order or simultaneously. At the same time, other operations may also be added to these processes, or a certain step or several steps of operations may be removed from these processes.

[0031] Reference Figure 1 , is a flow chart of an optional example of an improved common-source common-gate low-noise amplifier based on in-phase amplification proposed by the present invention. The method can be applied to computer equipment. The low-noise amplifier proposed in this embodiment may include but is not limited to the following structure:

[0032] The invention comprises a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a first transformer T1, a first inductor L1, a second inductor L2, a third inductor L3, a first resistor R1, a second resistor R2, a first transistor M1, a second transistor M2 and a third transistor M3, wherein:

[0033] The first end of the first capacitor C1, the opposite end of the main coil in the first transformer T1 and the gate of the first transistor M1 are connected;

[0034] The second end of the first capacitor C1 serves as the input end of the improved common-source and common-gate low-noise amplifier based on in-phase amplification;

[0035] The source of the first transistor M1 is connected to the first end of the first inductor L1;

[0036] The second end of the first inductor L1 is grounded;

[0037] The same-name end of the main coil in the first transformer T1, the first end of the second capacitor C2, the gate of the second transistor M2, the drain of the second transistor M2 and the first end of the first resistor R1 are connected;

[0038] The source of the second transistor M2 is grounded;

[0039] The second end of the first resistor R1, the second end of the second resistor R2 and the first end of the second inductor L2 are connected;

[0040] The first end of the second inductor L2 is also connected to the Vdd power supply terminal;

[0041] The drain of the first transistor M1 is connected to the same-name end of the secondary coil of the first transformer T1;

[0042] The opposite-sign end of the secondary coil in the first transformer T1 is connected to the source of the third transistor M3;

[0043] The gate of the third transistor M3, the first end of the third capacitor C3 and the first end of the second resistor R2 are connected;

[0044] The second end of the third capacitor C3 is grounded;

[0045] The drain of the third transistor T3, the second end of the second inductor L2 and the first end of the fourth capacitor C4 are connected;

[0046] The second end of the fourth capacitor C4, the first end of the third inductor L3 and the first end of the fifth capacitor C5 are connected;

[0047] The second end of the fifth capacitor C5 serves as the output end of the improved common-source common-gate low-noise amplifier based on in-phase amplification.

[0048] A second end of the third inductor L3 is grounded.

[0049] Based on the above scheme, the structure of the present invention and the traditional structure are simulated respectively to compare their performances.

[0050] Figure 2 The noise figure (NF) of the traditional LNA and the improved LNA is compared. From the comparison of various indicators of the two, it can be seen intuitively that due to the addition of the transformer, the noise and gain of the input stage are amplified, and the noise will flow from the feedback structure formed by the transformer into the drain of the common source transistor again, causing part of the noise to be amplified. Therefore, the noise figure is increased in some frequency bands compared with the traditional type, but the overall noise figure of the improved LNA is smaller than that of the traditional LNA, and from Figure 2 It can be seen that the overall noise flatness of the improved low noise amplifier is better than that of the traditional low noise amplifier. In addition, due to the effect of the transformer, the improved low noise amplifier can achieve a wider bandwidth S11, such as Figure 3 .

[0051] Figure 3The input return loss (S11) of the traditional low noise amplifier and the improved low noise amplifier is compared. From the comparison of various indicators of the two, it can be seen intuitively that the improved low noise amplifier has a better S11, which makes the input matching degree higher and is more conducive to the signal input circuit. It can avoid signal reflection caused by factors such as impedance mismatch to a greater extent. Moreover, compared with two LC sections, the improved low noise amplifier not only achieves a wider bandwidth S11, but also saves the area of ​​one LC section, which can save the chip area to a greater extent.

[0052] Figure 4 The gain (Gain) of the traditional low noise amplifier and the improved low noise amplifier is compared. By comparing the various indicators of the two, it can be intuitively seen that due to the addition of the transformer to amplify the signal in phase, the gain of the improved low noise amplifier using the transformer as the input stage matching network is higher than the gain of the traditional low noise amplifier using two LC matching networks at the input stage, and the application bandwidth of the gain is also increased. This is due to the principle of in-phase amplification. The signal lost from the bias path will flow into the amplification link again through the transformer, forming a positive feedback structure (such as Figure 5 ), the gain of the LNA structure can be improved in the full frequency band, which is impossible for traditional LNAs. This is also one of the advantages of adding a transformer for input matching.

[0053] In the structure of the present invention, after the two inductors are staggered and overlapped to form an electromagnetic coupling effect, not only will the signal be amplified in phase, but a negative feedback circuit structure will also be formed. After the signal passes through the gate of the first transistor and the drain, due to the electromagnetic coupling effect, part of the signal will pass through the drain and then return to the gate of the first transistor again due to the transformer negative feedback structure. The stability coefficient of the circuit is simulated and verified. Figure 6 , the stability coefficients of both the traditional and improved structures are greater than 1, and both are absolutely stable circuits. The improved circuit structure has improved the stability coefficient of the circuit because of the negative feedback of the transformer, which can better stabilize and protect the circuit. This phenomenon can also explain why the noise coefficient stability of the transformer feedback structure, that is, the noise flatness, is better than the traditional structure - that is, the structure without feedback, because the noise is also fed back to the drain. The noise will be transmitted back to the gate in a small range, forming a noise closed loop. Therefore, it will show a relatively flat nature in terms of noise.

[0054] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. An improved common-source common-gate low-noise amplifier based on in-phase amplification, characterized in that: The invention comprises a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a first transformer, a first inductor, a second inductor, a third inductor, a first resistor, a second resistor, a first transistor, a second transistor and a third transistor, wherein: The first capacitor and the first transformer form a transformer-based input matching network; The first transistor and the third transistor constitute a common-source common-gate low-noise amplifier; The first inductor is used as a source negative feedback inductor of the common-source and common-gate low-noise amplifier; The first transistor, the second transistor and the third transistor form a current mirror structure; The second inductor, the fourth capacitor, the third inductor and the fifth capacitor form an output matching network.

2. According to claim 1, an improved common-source common-gate low-noise amplifier based on in-phase amplification is characterized in that: The same-name end of the primary coil in the first transformer is connected to the opposite-name end of the secondary coil.

3. The improved common-source common-gate low-noise amplifier based on in-phase amplification according to claim 1, characterized in that: The first end of the first capacitor, the opposite end of the main coil in the first transformer and the gate of the first transistor are connected; The source of the first transistor is connected to the first end of the first inductor; The same-name end of the main coil in the first transformer, the first end of the second capacitor, the gate of the second transistor, the drain of the second transistor and the first end of the first resistor are connected; The second end of the first resistor, the second end of the second resistor, and the first end of the second inductor are connected; The drain of the first transistor is connected to the same-name end of the secondary coil in the first transformer; The opposite-name end of the secondary coil in the first transformer is connected to the source of the third transistor; The gate of the third transistor, the first end of the third capacitor and the first end of the second resistor are connected; The drain of the third transistor, the second end of the second inductor and the first end of the fourth capacitor are connected; The second end of the fourth capacitor, the first end of the third inductor and the first end of the fifth capacitor are connected.

4. The improved common-source common-gate low-noise amplifier based on in-phase amplification according to claim 3, characterized in that: By controlling the gate length and gate width of the transistor in the current mirror structure, the current flowing through the cascode amplifier is changed, thereby affecting the bias of the improved cascode low noise amplifier.

5. The improved common-source common-gate low-noise amplifier based on in-phase amplification according to claim 4, characterized in that: The second resistor is a voltage-dividing resistor, and the gate voltage of the third transistor is adjusted by changing the resistance value of the second resistor.

6. The improved common-source common-gate low-noise amplifier based on in-phase amplification according to claim 5, characterized in that: The first capacitor and the fifth capacitor are both DC blocking capacitors; The second capacitor and the third capacitor are used for filtering; The second inductor is a choke inductor.

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