Transconductance enhancement low-noise amplifier and input matching bandwidth expansion method thereof

Abstract

The invention provides a transconductance-enhanced low-noise amplifier and an input matching bandwidth expansion method thereof, and the method comprises the steps: adding a series inductor L1 at the output end of an auxiliary amplifier A1, expanding the bandwidth of the auxiliary amplifier A1 under high frequency, and optimizing the input matching of the low-noise amplifier under high frequency band; the inductor L1 and the inductor Lb form a transformer with a coupling coefficient of k, and the equivalent Miller capacitance of the input end of the low-noise amplifier is reduced and the input matching of the low-noise amplifier at a high frequency band is optimized by introducing a feed-forward path. According to the low-noise amplifier, a common-gate amplifier structure adopting an active transconductance enhancement technology in an existing CMOS process is improved, and the input matching bandwidth of the low-noise amplifier is expanded to a great extent while the chip area is not increased.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a transconductance enhanced low noise amplifier and an input matching bandwidth expansion method thereof. Background Art

[0002] In the field of communications, the wider the frequency band, the more advantages it has in terms of data transmission efficiency, signal quality, system capacity, and adaptability to different application scenarios. Therefore, with the advancement of communication technology and the development of market demand, increasing the width of the communication frequency band has become an important development direction.

[0003] In addition, as the first active module of the RF receiver, the gain and noise figure of the low noise amplifier dominate the overall noise figure of the RF receiver. Therefore, in order to ensure the communication quality of the RF receiver, a low noise amplifier with high gain and low noise figure is required.

[0004] See also Figure 1 In CMOS technology, broadband low noise amplifiers often use a common gate amplifier structure with active transconductance enhancement technology. Among them, M1 is a common gate amplifier tube, A1 is an auxiliary amplifier with a voltage gain of a, and R L is the load resistance, C0 is the parasitic capacitance between the input node and the output node of the auxiliary amplifier A1, and the inductor L b While providing a DC path to the ground for the common-gate amplifier M1, it also prevents the AC signal from flowing to the ground. With the help of the auxiliary amplifier A1, the channel noise contribution of the common-gate amplifier M1 is suppressed by 1+a times. The input admittance of the above broadband low-noise amplifier is expressed by the following formula:

[0005]

[0006] In the formula, g m is the transconductance of the common gate amplifier tube M1, C0 is also amplified by 1+a times by the Miller effect, and the inductor L b When the value is large, its influence can be ignored. Assume that the Miller capacitance in equation (1) is C M :

[0007] C M =(1+a)C0 (2)

[0008] The problems and disadvantages of the above scheme are:

[0009] 1. In actual design, the bandwidth of the auxiliary amplifier A1 is limited. As the frequency increases, the voltage gain a of the auxiliary amplifier A1 further decreases, which will lead to the deterioration of the input matching of the broadband low noise amplifier.

[0010] 2. The parasitic capacitance C0 between the input node and the output node of the auxiliary amplifier A1 is amplified by 1+a times by the Miller effect, which will also cause the input matching to further deteriorate with the increase of frequency. Summary of the invention

[0011] The present invention aims to provide a transconductance enhanced low noise amplifier and an input matching bandwidth expansion method thereof, so as to solve the problems of limited gain and input matching bandwidth existing in the common gate amplifier with active transconductance enhancement technology in the existing CMOS process.

[0012] The present invention provides a method for extending the input matching bandwidth of a transconductance enhanced low noise amplifier, comprising:

[0013] Add a series inductor L1 at the output end of the auxiliary amplifier A1 to expand the bandwidth of the auxiliary amplifier A1 at high frequencies and optimize the input matching of the low noise amplifier at high frequencies;

[0014] Inductor L1 and inductor L b A transformer with a coupling coefficient of k is formed, and by introducing a feed-forward path, the equivalent Miller capacitance at the input end of the low-noise amplifier is reduced, thereby optimizing the input matching of the low-noise amplifier in the high frequency band.

[0015] The present invention provides a transconductance enhanced low noise amplifier, comprising a common gate amplifier tube M1, an auxiliary amplifier A1, a load resistor R L , parasitic capacitance C0, inductance L b and inductor L1; the source of the common gate amplifier tube M1 and the amplifier input terminal, inductor L b One end of the inductor is connected to the input of the auxiliary amplifier A1. b The other end is connected to the common terminal Gnd; the gate of the common gate amplifier tube M1 is connected to the output end of the auxiliary amplifier A1 through the inductor L1; the drain of the common gate amplifier tube M1 is connected to the amplifier output end and the load resistor R L One end of the load resistor R L The other end is connected to the power supply Vdd; the parasitic capacitor C0 is connected in parallel between the input node and the output node of the auxiliary amplifier A1; the inductor L b Together with inductor L1, a transformer is formed. b is the primary inductance, inductance L1 is the secondary inductance, the coupling coefficient is k, and the inductance L b There is a feed-forward path to inductor L1.

[0016] Furthermore, in the small signal model of the transconductance enhanced low noise amplifier, the common gate amplifier tube M1 is replaced by a voltage-controlled current source S1; the inductor L b The coupling relationship with inductor L1 is determined by bThe current-controlled current source S2 connected in parallel and the current-controlled current source S3 connected in parallel with the inductor L1 are equivalently replaced.

[0017] Furthermore, the small signal model of the transconductance enhanced low noise amplifier applies Kirchhoff's law to calculate the input admittance of the transconductance enhanced low noise amplifier:

[0018]

[0019] In the formula, g m is the transconductance of the common gate amplifier tube M1, a is the voltage gain of the auxiliary amplifier A1, and M is the inductance L b The equivalent mutual inductance with inductor L1, equivalent mutual inductance s is a complex variable of the signal in the frequency domain analysis, expressed as s=jω, j is an imaginary unit, ω=2πf, and f is the signal frequency.

[0020] In some preferred embodiments, the auxiliary amplifier A1 includes: a MOS tube M2, a MOS tube M3 and a resistor R b ; The drain of MOS tube M2, the drain of MOS tube M3 and R b One end is connected to the output end of A1; the gate of MOS tube M2, the gate of MOS tube M3 and R b The other end of is connected to the input end of A1; the source of the MOS tube M2 is connected to the common end Gnd, and the source of the MOS tube M3 is connected to the power supply Vdd.

[0021] In some preferred implementations, the common-gate amplifier tube M1 is an NMOS tube.

[0022] In some preferred implementations, the MOS tube M2 is an NMOS tube, and the MOS tube M3 is a PMOS tube.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0024] The present invention improves the common-gate amplifier structure with active transconductance enhancement technology in the existing CMOS process, and greatly expands the input matching bandwidth of the low-noise amplifier without increasing the chip area. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the principle of a transconductance enhanced low noise amplifier in the prior art.

[0026] Figure 2 It is a schematic diagram of the principle of a transconductance enhanced low noise amplifier in an embodiment of the present invention.

[0027] Figure 3 In the embodiment of the present invention Figure 2Schematic diagram of the small signal model of the transconductance enhanced low noise amplifier shown.

[0028] Figure 4 Schematic diagram of an implementation form of the auxiliary amplifier A1 in an embodiment of the present invention.

[0029] Figure 5 The following is a curve diagram of input matching performance simulation of an example in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example

[0033] In view of the problem of limited gain and input matching bandwidth of a common-gate amplifier with active transconductance enhancement technology in the existing CMOS process, this embodiment proposes a method for extending the input matching bandwidth of a transconductance enhanced low-noise amplifier. The basic idea is:

[0034] Add a series inductor L1 at the output end of the auxiliary amplifier A1 to expand the bandwidth of the auxiliary amplifier A1 at high frequencies and optimize the input matching of the low noise amplifier at high frequencies;

[0035] Inductor L1 and inductor L b A transformer with a coupling coefficient of k is formed, and by introducing a feed-forward path, the equivalent Miller capacitance at the input end of the low-noise amplifier is reduced, thereby optimizing the input matching of the low-noise amplifier in the high frequency band.

[0036] See also Figure 2 A transconductance enhanced low noise amplifier, comprising a common gate amplifier tube M1 (implemented as an NMOS tube in this embodiment), an auxiliary amplifier A1 with a voltage gain of a, and a load resistor R L , parasitic capacitance C0, inductance L b and inductor L1; the source of the common gate amplifier tube M1 and the amplifier input terminal, inductor L bOne end of the inductor is connected to the input of the auxiliary amplifier A1. b The other end is connected to the common terminal Gnd; the gate of the common gate amplifier tube M1 is connected to the output end of the auxiliary amplifier A1 through the inductor L1; the drain of the common gate amplifier tube M1 is connected to the amplifier output end and the load resistor R L One end of the load resistor R L The other end is connected to the power supply Vdd; the parasitic capacitor C0 is connected in parallel between the input node and the output node of the auxiliary amplifier A1; the inductor L b Together with inductor L1, a transformer is formed. b is the primary inductance, inductance L1 is the secondary inductance, the coupling coefficient is k, and the inductance L b There is a feed-forward path to inductor L1.

[0037] See also Figure 3 . Figure 3 yes Figure 2 The small signal model of the common gate amplifier M1 is replaced by the voltage-controlled current source S1; the inductor L b The coupling relationship with inductor L1 is determined by b The current-controlled current source S2 connected in parallel and the current-controlled current source S3 connected in parallel with the inductor L1 are equivalently replaced. b Current = i Lb , the current flowing through the inductor L1 = i L1 , the small signal current flowing through the current-controlled current source S1 = g m v gs , the small signal current flowing through the current-controlled current source S2 Small signal current flowing through current-controlled current source S3 Where M is the inductance L b The relationship between the equivalent mutual inductance of the inductor L1 and the inductor L2 is expressed by the following formula (3):

[0038]

[0039] The input matching bandwidth expansion mechanism of a transconductance enhanced low noise amplifier is analyzed as follows:

[0040] Figure 2 The middle inductor L1 separates the parasitic capacitance from the output end of the auxiliary amplifier A1 to the common end Gnd and the parasitic capacitance from the gate of the common gate amplifier M1 to the common end Gnd, thereby splitting the original low-frequency pole into two higher frequency poles, expanding the gain bandwidth of the auxiliary amplifier A1.

[0041] right Figure 3 The small signal model shown in the figure is applied with Kirchhoff's law, and the input admittance of the transconductance enhanced low noise amplifier in this embodiment can be calculated to be expressed by the following formula:

[0042]

[0043] In the formula, g m is the transconductance of the common gate amplifier tube M1, and the parasitic capacitance C0 is also amplified by (1+a)(1-M / L1) times by the Miller effect. s is the complex variable of the signal in the frequency domain analysis, expressed as s=jω, j is the imaginary unit, ω=2πf, f is the signal frequency, and the inductance L b When the value is large, its influence can be ignored. Let's assume that the Miller capacitance in equation (4) is C' M :

[0044]

[0045] In the formula, C M It is the equivalent Miller capacitance at the input of the transconductance enhanced low noise amplifier in the prior art. It can be seen that the equivalent Miller capacitance at the input of the transconductance enhanced low noise amplifier in this embodiment is (1-M / L1) times the equivalent Miller capacitance at the input of the broadband low noise amplifier in the prior art, which is significantly reduced; at the same time, the remaining terms in the input admittance expression of the transconductance enhanced low noise amplifier in this embodiment are consistent with the equivalent Miller capacitance at the input of the broadband low noise amplifier in the prior art. Therefore, the high-frequency bandwidth of the input matching of the transconductance enhanced low noise amplifier in this embodiment is expanded.

[0046] See also Figure 4 A realization form of an auxiliary amplifier A1 in a transconductance enhanced low noise amplifier, comprising: an NMOS tube M2, a PMOS tube M3 and a resistor R b ; The drain of NMOS tube M2, the drain of PMOS tube M3 and R b One end is connected to the output end of A1; the gate of NMOS tube M2, the gate of PMOS tube M3 and R b The other end is connected to the input end of A1; the source of the NMOS tube M2 is connected to the common end Gnd, and the source of the PMOS tube M3 is connected to the power supply Vdd.

[0047] See also Figure 5 In one example, the inductor L b The value is 420pH, the inductance L1 is 420pH, the coupling coefficient k is 0.5, and the load resistance R L The value is 490Ω, the width of the common gate amplifier tube M1 is 3.6um, and the length of the common gate amplifier tube M1 is 60nm; the width of the NMOS tube M2 is 42um, and the length of the NMOS tube M2 is 60nm; the width of the PMOS tube M3 is 48um, and the length of the PMOS tube M3 is 60nm, and the resistor R bThe value is 10kΩ. Simulation shows that in the bandwidth of 16.1GHz to 50.9GHz, S11 of the input port is less than -10dB. The low noise amplifier based on CMOS technology of the present invention achieves ultra-wideband input matching performance.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for extending the input matching bandwidth of a transconductance enhanced low noise amplifier, characterized in that: include: Add a series inductor L1 at the output end of the auxiliary amplifier A1 to expand the bandwidth of the auxiliary amplifier A1 at high frequencies and optimize the input matching of the low noise amplifier at high frequencies; Inductor L1 and inductor L b A transformer with a coupling coefficient of k is formed, and by introducing a feed-forward path, the equivalent Miller capacitance at the input end of the low-noise amplifier is reduced, thereby optimizing the input matching of the low-noise amplifier in the high frequency band.

2. A transconductance enhanced low noise amplifier, characterized in that: Including common gate amplifier M1, auxiliary amplifier A1, load resistor R L , parasitic capacitance C0, inductance L b and inductor L1; the source of the common gate amplifier tube M1 and the amplifier input terminal, inductor L b One end of the inductor is connected to the input of the auxiliary amplifier A1. b The other end is connected to the common terminal Gnd; the gate of the common gate amplifier tube M1 is connected to the output end of the auxiliary amplifier A1 through the inductor L1; the drain of the common gate amplifier tube M1 is connected to the amplifier output end and the load resistor R L One end of the load resistor R L The other end is connected to the power supply Vdd; the parasitic capacitor C0 is connected in parallel between the input node and the output node of the auxiliary amplifier A1; the inductor L b Together with inductor L1, a transformer is formed. b is the primary inductance, inductance L1 is the secondary inductance, the coupling coefficient is k, and the inductance L b There is a feed-forward path to inductor L1.

3. The transconductance enhanced low noise amplifier according to claim 2, characterized in that: In the small signal model of the transconductance enhanced low noise amplifier, the common gate amplifier tube M1 is replaced by a voltage-controlled current source S1; the inductor L b The coupling relationship with inductor L1 is determined by b The current-controlled current source S2 connected in parallel and the current-controlled current source S3 connected in parallel with the inductor L1 are equivalently replaced.

4. The transconductance enhanced low noise amplifier according to claim 3, characterized in that: The small signal model of the transconductance enhanced low noise amplifier applies Kirchhoff's law to calculate the input admittance of the transconductance enhanced low noise amplifier: In the formula, g m is the transconductance of the common gate amplifier tube M1, a is the voltage gain of the auxiliary amplifier A1, and M is the inductance L b The equivalent mutual inductance with the inductor L1, s is the complex variable of the signal in the frequency domain analysis, expressed as s=jω, j is the imaginary unit, ω=2πf, f is the signal frequency.

5. The transconductance enhanced low noise amplifier according to claim 4, characterized in that: Equivalent Mutual Inductance 6. The transconductance enhanced low noise amplifier according to claim 2, characterized in that: The auxiliary amplifier A1 includes: MOS tube M2, MOS tube M3 and resistor R b ; The drain of MOS tube M2, the drain of MOS tube M3 and R b One end is connected to the output end of A1; the gate of MOS tube M2, the gate of MOS tube M3 and R b The other end of is connected to the input end of A1; the source of the MOS tube M2 is connected to the common end Gnd, and the source of the MOS tube M3 is connected to the power supply Vdd.

7. The transconductance enhanced low noise amplifier according to any one of claims 2 to 6, characterized in that: The common-gate amplifier tube M1 is an NMOS tube.

8. The transconductance enhanced low noise amplifier according to claim 6, characterized in that: The MOS tube M2 is an NMOS tube, and the MOS tube M3 is a PMOS tube.

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